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Sample records for weed competition planting

  1. Crop–weed competition

    DEFF Research Database (Denmark)

    Gallandt, Eric R.; Weiner, Jacob

    2015-01-01

    on crops. Longer term management of crop–weed competition can be achieved through crop rotations, specifically crop sequences that reduce the weed seed bank, and therefore seedling density, and prevent proliferation of perennial weeds. Key ConceptsKey Concepts * Plant growth requires sunlight, water...

  2. PLANT SPACING AND WEED MANAGEMENT TECHNIQUES INFLUENCE WEED COMPETITIVENESS OF DRUM SEEDED RICE (Oryza sativa L.

    Directory of Open Access Journals (Sweden)

    B N Sandeep Nayak

    2014-11-01

    plant densities, a medium level population of 47 hills m-2 (D2 significantly increased the paddy yield over all other treatments except D1 treatments with a plant density of 71 hills m-2 .The highest grain yield of 3476 kg ha-1 was observed with a plant density of 47 hills m-2 and it was significantly superior to 71, 35, 28, 20 hills m-2drum seeded and 33 hills m-2 transplant paddies. which ultimately produced the highest rice yield. Weed inflicted relative yield loss was also minimized by the closest spacing. Present findings imply rice spacing mostly determines rice-weed competition, and can play a decisive role to minimize weed pressure. Therefore, closer spacing could be considered as a vital tool in the integrated weed management program for direct wet-seeded rice sown through drum seeder.

  3. Interaction Effects of Planting Date and Weed Competition on Yield and Yield Components of Three white Bean Cultivars in Semirom

    Directory of Open Access Journals (Sweden)

    A. Yadavi

    2012-06-01

    Full Text Available Unsuitable planting and weed competition are the most important factors that greatly reduce the yield of bean. In order to study the effect of planting date on yield and yield components of three white bean cultivars in weed infest and weed free condition a factorial experiment with randomized complete block design and three replications was carried out at Semirom in 2009. The treatments were planting date (May10, May 25 and June 9 and white bean cultivars (Shekofa, Pak and Daneshkade and two levels of weed infestation (weedy and weed free. Results showed that planting date, weed competition and cultivars had significant effects on yield and yield components of white bean. The 30-day delay in planting date reduced the number of pods per plant, seeds per pod, 100 seed weight and biological yield of white bean cultivars, 22.5, 18, 20.1 and 22.5 percent respectively. Also weed competition, reduced the number of seeds per pod, 100 seed weight and biological yield respectively by 13.5, 5.7 and 27.1 percent. Result of planting date and weed competition interaction effects indicated that the weed competition decreased grain yield (53% in third planting date more than others and delay in planting date was companion with increasing weed density and dry weight in flowering stage of bean. Also Shekofa cultivar had highest grain yield (3379 kg/ha at the first planting date and weed free condition.

  4. Application of electrical capacitance measurement for in situ monitoring of competitive interactions between maize and weed plants

    Directory of Open Access Journals (Sweden)

    Imre Cseresnyés

    2016-06-01

    Full Text Available Applicability of root electrical capacitance (EC measurement for monitoring of crop–weed competition was studied in a pot experiment. Maize (Zea mays L. was grown both alone and with Echinochloa crus-galli or Abutilon theophrasti in different densities with regular measurement of root EC. Plants were harvested 42 days after planting to determine above- and belowground biomass. Depending on weed density, E. crus-galli-A. theophrasti interaction reduced the root EC of maize by 22–66% and 3–57%, respectively. Competitive effect of crop on weeds and intraspecific competition among weeds could also be detected by EC values: E. crus-galli was less sensitive both to the presence of maize and to intraspecific competition than A. theophrasti. Strong linear correlations between root dry mass and root EC for crop and weeds (with R2 from 0.901 to 0.956 were obtained by regression analyses at the end of the experiment. EC monitoring informed us on the emergence time of competition: E. crus-galli interfered with maize root growth a week earlier then A. theophrasti, and increasing weed densities accelerated the emergence of competition. In conclusion, the simple, non-destructive EC method should be considered a potential in situ technique for pot studies on crop–weed competition, which may partially substitute the intrusive techniques commonly used in agricultural researches.

  5. Application of electrical capacitance measurement for in situ monitoring of competitive interactions between maize and weed plants

    Energy Technology Data Exchange (ETDEWEB)

    Cseresnyés, I.; Takács, T.; Füzy, A.; Végh, K.R.; Lehoczky, E.

    2016-11-01

    Applicability of root electrical capacitance (EC) measurement for monitoring of crop–weed competition was studied in a pot experiment. Maize (Zea mays L.) was grown both alone and with Echinochloa crus-galli or Abutilon theophrasti in different densities with regular measurement of root EC. Plants were harvested 42 days after planting to determine above- and belowground biomass. Depending on weed density, E. crus-galli-A. theophrasti interaction reduced the root EC of maize by 22–66% and 3–57%, respectively. Competitive effect of crop on weeds and intraspecific competition among weeds could also be detected by EC values: E. crus-galli was less sensitive both to the presence of maize and to intraspecific competition than A. theophrasti. Strong linear correlations between root dry mass and root EC for crop and weeds (with R2 from 0.901 to 0.956) were obtained by regression analyses at the end of the experiment. EC monitoring informed us on the emergence time of competition: E. crus-galli interfered with maize root growth a week earlier then A. theophrasti, and increasing weed densities accelerated the emergence of competition. In conclusion, the simple, non-destructive EC method should be considered a potential in situ technique for pot studies on crop–weed competition, which may partially substitute the intrusive techniques commonly used in agricultural researches. (Author)

  6. CRITICAL PERIOD OF MUNGBEAN (PHASEOLUS RADIATUS L. TO WEED COMPETITION

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    I.H. UTOMO*

    1989-01-01

    Full Text Available A field experiment was conducted to study the critical period of weed control on the crop of mungbean (Phaseolus radiatus L.. The studies were done in the field of BIOTROP Experimental Station with the natural existing weed population. It was found that the critical period of mungbean to weed competition was from 3-6 weeks after planting.

  7. CRITICAL PERIOD OF MUNGBEAN (PHASEOLUS RADIATUS L.) TO WEED COMPETITION

    OpenAIRE

    I.H. UTOMO*

    1989-01-01

    A field experiment was conducted to study the critical period of weed control on the crop of mungbean (Phaseolus radiatus L.). The studies were done in the field of BIOTROP Experimental Station with the natural existing weed population. It was found that the critical period of mungbean to weed competition was from 3-6 weeks after planting.

  8. Competitive ability of black common bean genotypes with weeds

    Directory of Open Access Journals (Sweden)

    Gilcimar Adriano Vogt

    2013-10-01

    Full Text Available The morpho-physiologic characteristics of common bean plants can affect their competitive ability with weeds. The objective of this work was to evaluate the competitive ability of black bean genotypes with weeds. An experiment was carried out in the 2010/11 cropping season in Papanduva, SC, southern Brazil, in order to verify the variability of some plant characteristics among genotypes of common bean. The randomized block design was used, with four replications. Seven cultivars underwent the treatments: BRS Campeiro, CHP 01-238, CHP 01-239, Diamante Negro, BRS Supremo, BRS Valente, IPR Uirapuru, FTS Soberano, IPR Graúna, IPR Tiziu e IAC Diplomata. At 6, 14, 18, 25 and 32 days after emergence (DAE were evaluated plant height, ground cover by common bean plants, dry biomass of stems and leaves, and grain yield. In the 2011/12 cropping season the same cultivars were grown in the presence or absence of weeds, adopting similar methodology to the 2010/11. The losses of grain yield in black common bean genotypes due to weed interference ranged from 30.8% to 54.9%. There was a positive correlation between yield reduction promoted by the weed infestation and dry biomass produced by the weeds. In addition, there was a positive correlation between percentage of yield reduction due to the weed infestation and grain yield without weed interference. The characteristics evaluated did not estimate the competitive ability of black common bean genotypes with weeds.

  9. Global warming increases the interspecific competitiveness of the invasive plant alligator weed, Alternanthera philoxeroides.

    Science.gov (United States)

    Wu, Hao; Ismail, Mohannad; Ding, Jianqing

    2017-01-01

    Global warming could accelerate the spread of invasive species to higher latitudes and intensify their effects on native species. Here, we report results of two years of field surveys along a latitudinal gradient (21°N to 31°N) in southern China, to determine the species structure of the invasive plant Alternanthera philoxeroides community. We also performed a replacement series experiment (mono and mixed) to evaluate the effects of elevated temperature on the competitiveness of A. philoxeroides with the native co-occurring species Digitaria sanguinalis. In the field survey, we found that the dominance of A. philoxeroides increased with increasing of latitude gradient while cover of D. sanguinalis decreased. In monospecific plantings, artificial warming reduced the length of D. sanguinalis roots. In mixed plantings, warming reduced both A. philoxeroides abundance and D. sanguinalis stem length when A. philoxeroides was more prevalent in the planting. Warming also significantly reduced D. sanguinalis biomass, but increased that of A. philoxeroides. In addition, elevated temperatures significantly reduced the relative yield (RY) of D. sanguinalis, particularly when A. philoxeroides was planted in higher proportion in the plot. These results suggest that the invasiveness of A. philoxeroides increased with increasing latitude, and that warming may increase the effectiveness of its interspecific competition with D. sanguinalis. Hence, under global warming conditions, the harm to native species from A. philoxeroides would increase at higher latitudes. Our findings are critical for predicting the invasiveness of alien species under climate change. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. [Alfalfa Planting as weed control

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a letter to farming cooperators regarding the stipulations surrounding alfalfa plantings in lieu of small grain plantings to provide weed control,...

  11. IMPORTANCE OF CRITICAL PERIOD OF WEED COMPETITION FOR CROP GROWING

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    Marijana Ivanek-Martinčić

    2010-06-01

    Full Text Available A concept of critical period of weed competition has been introduced for more than 40 years ago. The concept is based on the assumption that weeds are not equally harmful to a crop during the whole season and that there is a period in crop development in which weeds impact on the yield is the biggest. This period is called critical period of weed competition (CPWC, critical period of weed interference, or critical period of weed control. There is a difference in CPWC between crops, but CPWC for a certain crop can vary a lot because it depends on many factors which can affect the crop or weeds competition ability. The critical period of weed competition identification is essential for integrated weed control and precise planning of a weed control strategy as well as for rationale use of herbicides and other weed control measures.

  12. Competitive oats for integrated weed management and organic rotations

    OpenAIRE

    Fradgley, Nick

    2014-01-01

    Using a competitive crop like oats is essential for integrated management of weed problems. Oats can compete well with weeds through efficient nutrient uptake, allelopathy and canopy cover shading. Weeds are suppressed by the crops tillering ability and varieties with good canopy cover. Some varieties can tolerate weeds better by having both good canopy cover and height.

  13. Photosynthetic activity of cassava plants under weed competition Atividade fotossintética de plantas de mandioca submetidas a competição com plantas daninhas

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    I. Aspiazú

    2010-01-01

    Full Text Available The objective of this work was to evaluate characteristics associated with the photosynthetic activity of cassava plants under weed competition. The trial was carried out under field conditions, and experimental units consisted of 150 dm³ fiberglass boxes containing red yellow Latosol, previously corrected and fertilized. Treatments consisted in the cultivation of cassava plants which were free of weed competition and associated with three weed species: Bidens pilosa, Commelina benghalensis or Brachiaria plantaginea. After manioc sprouting started, 15 days after being planted, weeds that had been sown when manioc was planted were thinned, there were then eight plants left per experimental unit in accordance with specified treatments: cassava free of competition, cassava competing with B. pilosa, cassava competing with C. benghalensis and cassava competing with B. plantaginea. Sixty days after crop emergence leaf internal CO2 concentration (Ci, leaf temperature at the time of evaluation (Tleaf and photosynthetic rate (A were evaluated, also the CO2 consumption rate (ΔC of cassava plants was calculated. A correlation matrix between variables was also obtained. All characteristics associated with photosynthesis in cassava plants were influenced by weed species. Cassava was more affected by B. pilosa and B. plantaginea in which concerns its exposition to solar radiation and water, while C. benghalensis seems to mostly affect the composition of incident light on the culture, allowing cassava to anticipate imposition when competing, even before it reaches harmful levels.Objetivou-se com este trabalho avaliar características associadas à atividade fotossintética de plantas de mandioca sob competição ou não com plantas daninhas. O experimento foi realizado em condições de ambiente aberto, sendo as unidades experimentais compostas por vasos de fibra de vidro de 150 dm³ preenchidos com Latossolo Vermelho Amarelo, previamente adubado. Os

  14. Mycorrhizal association in soybean and weeds in competition

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    Cíntia Maria Teixeira Fialho

    2016-04-01

    Full Text Available The purpose of this study was to evaluate the effects of mycorrhizal association on the interference of Bidens pilosa, Urochloa decumbens and Eleusine indica on soybean culture in two conditions: a plants competing without contact with roots of another species; b with contact between roots. At 60 days after planting, growth, nutrient accumulation and mycorrhizal colonization of soybean and weeds were evaluated. The contact between roots of soybean plant and weed species increased the negative interference effects for both species, with less growth and nutrient accumulation. With the individualization of roots, higher competition occurred for soil resources up to 60 days of coexistence between species. In competition with soybean, Bidens pilosa and Urochloa decumbens stood out in accumulation of most nutrients without differing from when cultivated in monocultivation. The increase of the soybean mycorrhizal colonization was 53, 40 and 33% when in competition with Urochloa decumbens, Eleusine indica and Bidens pilosa species, respectively. A positive interaction occurred for soybean mycorrhizal colonization and competing plants irrespective of weed species or root contact.

  15. IMPORTANCE OF CRITICAL PERIOD OF WEED COMPETITION FOR CROP GROWING

    OpenAIRE

    Marijana Ivanek-Martinčić; Zvonimir Ostojić; Klara Barić

    2010-01-01

    A concept of critical period of weed competition has been introduced for more than 40 years ago. The concept is based on the assumption that weeds are not equally harmful to a crop during the whole season and that there is a period in crop development in which weeds impact on the yield is the biggest. This period is called critical period of weed competition (CPWC), critical period of weed interference, or critical period of weed control. There is a difference in CPWC between crops, but CPWC ...

  16. A review of the potential for competitive cereal cultivars as a tool in integrated weed management.

    Science.gov (United States)

    Andrew, I K S; Storkey, J; Sparkes, D L

    2015-06-01

    Competitive crop cultivars offer a potentially cheap option to include in integrated weed management strategies (IWM). Although cultivars with high competitive potential have been identified amongst cereal crops, competitiveness has not traditionally been considered a priority for breeding or farmer cultivar choice. The challenge of managing herbicide-resistant weed populations has, however, renewed interest in cultural weed control options, including competitive cultivars. We evaluated the current understanding of the traits that explain variability in competitive ability between cultivars, the relationship between suppression of weed neighbours and tolerance of their presence and the existence of trade-offs between competitive ability and yield in weed-free scenarios. A large number of relationships between competitive ability and plant traits have been reported in the literature, including plant height, speed of development, canopy architecture and partitioning of resources. There is uncertainty over the relationship between suppressive ability and tolerance, although tolerance is a less stable trait over seasons and locations. To realise the potential of competitive crop cultivars as a tool in IWM, a quick and simple-to-use protocol for assessing the competitive potential of new cultivars is required; it is likely that this will not be based on a single trait, but will need to capture the combined effect of multiple traits. A way needs to be found to make this information accessible to farmers, so that competitive cultivars can be better integrated into their weed control programmes.

  17. Quantifying the effect of crop spatial arrangement on weed suppression using functional-structural plant modelling.

    Science.gov (United States)

    Evers, Jochem B; Bastiaans, Lammert

    2016-05-01

    Suppression of weed growth in a crop canopy can be enhanced by improving crop competitiveness. One way to achieve this is by modifying the crop planting pattern. In this study, we addressed the question to what extent a uniform planting pattern increases the ability of a crop to compete with weed plants for light compared to a random and a row planting pattern, and how this ability relates to crop and weed plant density as well as the relative time of emergence of the weed. To this end, we adopted the functional-structural plant modelling approach which allowed us to explicitly include the 3D spatial configuration of the crop-weed canopy and to simulate intra- and interspecific competition between individual plants for light. Based on results of simulated leaf area development, canopy photosynthesis and biomass growth of the crop, we conclude that differences between planting pattern were small, particularly if compared to the effects of relative time of emergence of the weed, weed density and crop density. Nevertheless, analysis of simulated weed biomass demonstrated that a uniform planting of the crop improved the weed-suppression ability of the crop canopy. Differences in weed suppressiveness between planting patterns were largest with weed emergence before crop emergence, when the suppressive effect of the crop was only marginal. With simultaneous emergence a uniform planting pattern was 8 and 15 % more competitive than a row and a random planting pattern, respectively. When weed emergence occurred after crop emergence, differences between crop planting patterns further decreased as crop canopy closure was reached early on regardless of planting pattern. We furthermore conclude that our modelling approach provides promising avenues to further explore crop-weed interactions and aid in the design of crop management strategies that aim at improving crop competitiveness with weeds.

  18. Developing selection protocols for weed competitiveness in aerobic rice

    NARCIS (Netherlands)

    Zhao, D.L.; Atlin, G.N.; Bastiaans, L.; Spiertz, J.H.J.

    2006-01-01

    Aerobic rice production systems, wherein rice is dry-sown in non-puddled soil and grown as an upland crop, offer large water savings but are subject to severe weed infestation. Weed-competitive cultivars will be critical to the adoption of aerobic rice production by farmers. Breeding

  19. Quantifying the effect of crop spatial arrangement on weed suppression using functional-structural plant modelling

    NARCIS (Netherlands)

    Evers, Jochem B.; Bastiaans, Lammert

    2016-01-01

    Suppression of weed growth in a crop canopy can be enhanced by improving crop competitiveness. One way to achieve this is by modifying the crop planting pattern. In this study, we addressed the question to what extent a uniform planting pattern increases the ability of a crop to compete with weed

  20. Breeding cereal crops for enhanced weed suppression: optimizing allelopathy and competitive ability.

    Science.gov (United States)

    Worthington, Margaret; Reberg-Horton, Chris

    2013-02-01

    Interest in breeding grain crops with improved weed suppressive ability is growing in response to the evolution and rapid expansion of herbicide resistant populations in major weeds of economic importance, environmental concerns, and the unmet needs of organic producers and smallholder farmers without access to herbicides. This review is focused on plant breeding for weed suppression; specifically, field and laboratory screening protocols, genetic studies, and breeding efforts that have been undertaken to improve allelopathy and competition in rice, wheat, and barley. The combined effects of allelopathy and competition determine the weed suppressive potential of a given cultivar, and research groups worldwide have been working to improve both traits simultaneously to achieve maximum gains in weed suppression. Both allelopathy and competitive ability are complex, quantitatively inherited traits that are heavily influenced by environmental factors. Thus, good experimental design and sound breeding procedures are essential to achieve genetic gains. Weed suppressive rice cultivars are now commercially available in the U.S. and China that have resulted from three decades of research. Furthermore, a strong foundation has been laid during the past 10 years for the breeding of weed suppressive wheat and barley cultivars.

  1. Using Weeds and Wildflowers to Study Plants.

    Science.gov (United States)

    Nowak, Nancy

    1984-01-01

    Offers suggestions for activities in which local weeds and wildflowers are used to study a variety of topics. These topics include classification, ecological succession, and mapping. Also lists the types of experiments students can perform with these plants. (JN)

  2. Using Weeds and Wildflowers to Study Plants.

    Science.gov (United States)

    Nowak, Nancy

    1984-01-01

    Offers suggestions for activities in which local weeds and wildflowers are used to study a variety of topics. These topics include classification, ecological succession, and mapping. Also lists the types of experiments students can perform with these plants. (JN)

  3. Competitive suppression of weeds in a leek-celery intercropping system : An exploration of functional biodiversity

    NARCIS (Netherlands)

    Baumann, D.T.

    2001-01-01

    Late-emerging weeds, although not directly damaging the crop, may cause long-term weed management problems due to excessive seed production. Particularly in weak competitive crops with high quality requirements, such as leek, financial losses due to weed competition or weed management costs can be c

  4. The Effect of Weeds Interference Time and Plant Density on Weeds Control and Broad Bean (Vicia faba L. Yield

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    M Dabaghzadeh

    2016-10-01

    Full Text Available Introduction Broad bean (Vicia faba L. belongs to the Fabaceae family and is the most important protein plant in the world. Although broad bean used as cover crop is able to deal with weeds, but the evidence show that yield of the plant decreased 32-82% because of competition with weeds. Using crop density is one of the ecological approaches in weed management. Broad bean density can produce biomass, weed competition, seed yield and ultimately influence the economic yield. Many reports show that increasing crop density reduced negative effects of weeds. The aim of this experiment was to evaluate the effect of weeds interference and different densities of broad bean on density and biomass of weeds and broad bean seed yield. Materials and Methods The experiment was carried out as split plot in randomized complete block, with four replications, during 2009-2010 in a field experiment at Ramin Agricultural and Natural Resources University, Ahwaz. Weeds interference was investigated on 5 levels, including V5, V9, V13 broad-bean phonological stages, full season weeding and full season weeds interference selected as main plots, and broad-bean density on 3 levels: including 8, 11 and 14 plants m-2 as subplots. Density, dry weight and diversity of weeds and seed yield of broad bean were evaluated. Results and Discussion The results showed that the weeds including wild beet, field bindweed and mallow had the highest occurrence (26.35, 21.17 and 18.46 plants m-2 respectively in V9 broad-bean phonological stage, where the peak abundance of weeds was observed. The frequency of mallow, clover and yellow alfalfa were high until V5 broad-bean phonological stage, but in the next stages, they were replaced by other weeds and sorrel. It was also observed that the environmental factors can affect composition of weeds, for example, as the temperature increased in the early spring, an increase in the density of field bindweed was recorded. In the treatment of 8 plants

  5. Effect of pre-planting irrigation, maize planting pattern and nitrogen on weed seed bank population.

    Science.gov (United States)

    Hemmati, E; Vazan, S; Oveisi, M

    2011-01-01

    Pre-planting irrigation and planting patterns are important factors in weed management that effect on seed bank. Additionally, the nitrogen is the most important factor in plant growth that affects weed-crop competition and ultimately, seed rain into the soil. A field experiment was conducted to study the effect of nitrogen application rates, pre-planting irrigation and maize planting patterns on weed seed bank population. Experimental factors were nitrogen rates at 4 levels (200, 300, 400 and 500 kg per hectare) as main plot; and pre-planting irrigation at 2 levels (irrigation before planting plus weeding emerged seedlings and, irrigation after sowing), and maize planting patterns (one-row and two-row planting of maize with same density per square of row length) that were assigned in a factorial arrangement to the sub plots. Soil samples were taken at the beginning of the season (before planting of maize) and at the end of the season (after harvest) at depth of 0-5 cm in the fixed quadrates (60 cm x 60 cm). The weed seeds were extracted from the soil samples and were identified using standard methods. The majority of weed seed bank populations included 6 weed species: Portulaca oleracea, Chenopodium album, Amaranthus retroflexus, Sorghum halepense, Daturea stramonium, Xanthium strumarium. Results showed that population of weed seed bank increased significantly with increasing nitrogen rate. The increasing rate was different between one-row and two-row planting patterns. The parameters indicated that seed bank population was much higher in a one row planting pattern of maize. With two-row planting, seed bank was decreased by 34, 26, 20 and 5% at 200, 300, 400 and 500 kg N/ha, respectively. Pre-planting irrigation was also found an effective implement to reduce the weed seed bank. When pre-planting irrigation was applied, seed bank was decreased by 57, 43, 34 and 9% at 200, 300, 400 and 500 kg N/ha. Increasing nitrogen because of weed's better growth and higher seed

  6. Cultivation of Pleurotus ostreatus on weed plants.

    Science.gov (United States)

    Das, Nirmalendu; Mukherjee, Mina

    2007-10-01

    Oyster mushroom, Pleurotus ostreatus (Jacq.:Fr.) Kumm. ITCC 3308 (collected from Indian Type Culture Collection, IARI, New Delhi, India, 110012) was grown on dry weed plants, Leonotis sp, Sida acuta, Parthenium argentatum, Ageratum conyzoides, Cassia sophera, Tephrosia purpurea and Lantana camara. Leonotis sp. was the best substrate in fruit body production of P. ostreatus when it was mixed with rice straw (1:1, wet wt/wet wt) for mushroom cultivation. The fruiting time for P. ostreatus was also less on Leonotis sp. than on any other weed substrates tested in the present investigation. T. purpurea was the least suited weed for oyster mushroom cultivation. The main problem of oyster mushroom cultivation on weed substrates was found to be low yield in the second flush that could be overcome by blending weed plants with rice straw. The protein contents of the fruit bodies obtained from Cassia sophera, Parthenium argentatum and Leonotis sp. were not only better than rice straw but also from the rice straw supplemented weeds.

  7. Competitivity of the common-bean plant relative to the weed alexandergrass [Brachiaria plantaginea (link hitch.] Competitividade do feijoeiro-comum com o capim-marmelada [Brachiaria plantaginea (link hitch.

    Directory of Open Access Journals (Sweden)

    Telma Passini

    2003-01-01

    Full Text Available Methodologies of competitive interaction quantification between weeds and crops are not widely elucidated and compared in the literature. The competitive ability of common-bean (Phaseolus vulgaris relative to alexandergrass (Brachiaria plantaginea was assessed and two approaches of replacement series experiment analysis were compared. The response of the species to the presence of each other at different densities and proportion was evaluated. Replacement series at total densities of 625, 816 and 1,111 plants m-2 were performed at the proportions of common-bean:alexandergrass of 100:0 (pure stand of common-bean, 75:25, 50:50, 25:75 and 0:100% (pure stand of alexandergrass, at four replicates in a randomized block design. Data analyses were performed by the qualitative compared to the quantitative approach. The quantitative approach provided larger number of information than did the qualitative approach, and indicated that there was intraspecific competition among common-bean plants, and a minimum of interspecific competition from alexandergrass. There was no intraspecific competition among alexandergrass plants, being the crop effect on the weed larger than the effect among alexandergrass plants. The ecological niche differentiation was partial, since the crop intraspecific competition was larger than the interspecific, and the last one was negligible, at the same time that the weed interspecific competition was larger than the intraspecific. Common-bean, as a competitor species, is superior to alexandergrass.As metodologias de quantificação das interações competitivas entre plantas cultivadas e daninhas não estão amplamente elucidadas e comparadas na literatura. A competitividade da cultura de feijão-comum (Phaseolus vulgaris em relação ao capim-marmelada (Brachiaria plantaginea foi avaliada pela comparação entre o método qualitativo e um método quantitativo de análise de resultados. A resposta de cada espécie à presença da

  8. Weed competitiveness and yielding ability of aerobic rice genotypes

    NARCIS (Netherlands)

    Zhao, D.L.

    2006-01-01

    Keywords:    Broad-sense heritability; Crop vigour; Genetic correlation; Indirect selection index; Plant erectness; Rice germplasm; Seeding rate; Vegetative growth; Weed-suppressive ability.

  9. Weed competitiveness and yielding ability of aerobic rice genotypes

    NARCIS (Netherlands)

    Zhao, D.L.

    2006-01-01

    Keywords:    Broad-sense heritability; Crop vigour; Genetic correlation; Indirect selection index; Plant erectness; Rice germplasm; Seeding rate; Vegetative growth; Weed-suppressive ability.

    Aerobi

  10. Do cover crop mixtures have the same ability to suppress weeds as competitive monoculture cover crops?

    Directory of Open Access Journals (Sweden)

    Brust, Jochen

    2014-02-01

    Full Text Available An increasing number of farmers use cover crop mixtures instead of monoculture cover crops to improve soil and crop quality. However, only little information is available about the weed suppression ability of cover crop mixtures. Therefore, two field experiments were conducted in Baden-Württemberg between 2010 and 2012, to compare growth and weed suppression of monoculture cover crops and cover crop mixtures. In the first experiment, heterogeneous results between yellow mustard and the cover crop mixture occurred. For further research, a field experiment was conducted in 2012 to compare monocultures of yellow mustard and hemp with three cover crop mixtures. The evaluated mixtures were: “MELO”: for soil melioration; “BETA”: includes only plant species with no close relation to main cash crops in Central Europe and “GPS”: for usage as energy substrate in spring. Yellow mustard, MELO, BETA and GPS covered 90% of the soil in less than 42 days and were able to reduce photosynthetically active radiation (PAR on soil surface by more than 96% after 52 days. Hemp covered 90% of the soil after 47 days and reduced PAR by 91% after 52 days. Eight weeks after planting, only BETA showed similar growth to yellow mustard which produced the highest dry matter. The GPS mixture had comparatively poor growth, while MELO produced similar dry matter to hemp. Yellow mustard, MELO and BETA reduced weed growth by 96% compared with a no cover crop control, while hemp and GPS reduced weeds by 85% and 79%. In spring, weed dry matter was reduced by more than 94% in plots with yellow mustard and all mixtures, while in hemp plots weeds were only reduced by 71%. The results suggest that the tested cover crop mixtures offer similar weed suppression ability until spring as the monoculture of the competitive yellow mustard.

  11. Effects of Planting Date, Time and Methods of Weed Control on Weed Density and Biomass in Cumin Fields

    Directory of Open Access Journals (Sweden)

    R. Ghorbani

    2011-01-01

    Full Text Available Abstract Two field experiments were carried out in order to evaluate the effect of planting date, method and date of weed control on weed density and biomass in the experimental research field, Faculty of Agriculture, Ferdowsi University of Mashhad, during 2006 and 2007. Treatments included planting date (30 December, 20 January and 30 February, weeding date (first true leaf, start of branching and beginning of flowering stages and weed control methods (hand weeding, fire treatment and control. The results showed that there were significant differences in the number of weeds between different sowing dates, weeding dates and control methods. The highest mean density and biomass of weeds were obtained on the planting date, 30 February, and when weed was controlled at the first leaf appearance stage with fire treatment. The most appropriate time for weed control was at the beginning of cumin flowering. Fire treatment reduced weed growth in the first half of growing season. However, hand weeding significantly reduced weed density and biomass in the second half of cumin growing season. The first planting date caused the lowest mean weed biomass and the highest cumin yield compared to later planting dates. Hand weeding treatment contained lower mean weed density and biomass compared to fire treatment, however, cumin yield was lower in hand weeding plots than fire treatment. Keywords: Cultural control, Cuminum cyminum, Fire, Hand weeding, Control time

  12. BIOLOGICAL CONTROL OF WEEDS BY MEANS OF PLANT PATHOGENS

    Directory of Open Access Journals (Sweden)

    Marija Ravlić

    2014-06-01

    Full Text Available Biological control is the use of live beneficial organisms and products of their metabolism in the pests control. Plant pathogens can be used for weed control in three different ways: as classical, conservation and augmentative (inoculative and inundated biological control. Inundated biological control involves the use of bioherbicides (mycoherbicides or artificial breeding of pathogens and application in specific stages of crops and weeds. Biological control of weeds can be used where chemical herbicides are not allowed, if resistant weed species are present or in the integrated pest management against weeds with reduced herbicides doses and other non-chemical measures, but it has certain limitations and disadvantages.

  13. Competição de plantas daninhas com a cultura do café em duas épocas de infestação Competition of weeds with coffee plants, in two times of infestation

    Directory of Open Access Journals (Sweden)

    C.M.T. Fialho

    2010-01-01

    ³ of substrate. The experiment was arranged in a randomized blocs, with four replications, in factorial design (2 x 4 x 2, with two weed species (Brachiaria decumbens and Brachiaria plantaginea, cultured per 90 days, in four densities (zero, two, four and six plants per pot, together with coffee seedlings of different ages: 60 and 180 days after transplanted. In the moment of the experiment harvest was evaluated the increment in plant height, in leaf area and in girth diameter of the coffee, dry matter of weeds and coffee, and coffee root density. It also estimated the leaf mass ratio, stem mass ratio, root mass ratio, root system/shoot ratio of coffee plants. The weeds provided negative interference in the characteristics evaluated. Verified was smaller increase of height, leaf area and total dry matter of coffee plants with the increase of weed density. The effects of plants interference were bigger when the interference was installed sooner. In this case smaller occurred accumulation of growth variables; however both grasses behaved of similar way not differing for the most variables. When the competition was installed later the coffee plants were more sensible to competition the B. plantaginea in relation to B. decumbens. The increase of weed densities promoted bigger allocation of photoassimilates for the shoot part in detriment to coffee root system.

  14. Prediction of the competitive effects of weeds on crop yields based on the relative leaf area of weeds

    DEFF Research Database (Denmark)

    Lotz, L. A. P.; Christensen, Svend; Cloutier, D.

    1996-01-01

    L.) and in 11 experiments in spring wheat (Triticum aestivum L.). Most data sets were heller described by a model based on the relative leaf area of the weed than by a hyperbolic model based on weed density. This leaf area model accounted for (part of) the effect of different emerging times of the S....... alba whereas the density model did not. A parameter that allows the maximum yield loss to be smaller than 100% was mostly not needed to describe the effects of weed competition. The parameter that denotes the competitiveness of the weed species with respect to the crop decreased the later the relative...... leaf area of the mustard was determined. This decrease could be estimated from the differences in relative growth rate of the leaf area of crop and S. alba. However, the accuracy of this estimation was poor. The parameter value of the leaf area model varied considerably between sites and years...

  15. Influence of Weed Competition on Potato Growth, Production and Radiation Use Efficiency

    Directory of Open Access Journals (Sweden)

    Farzad MONDANI

    2011-08-01

    Full Text Available Weed management in potato production is one of the main cost and time consuming practices. Understanding the most effective time of weed control could reduce the costs and increase potato yield. Field study was conducted in the west region of Iran during 2006 to evaluate the effect of weeds damage in potato fields. Twelve treatments used consisted of six initial weed-free periods in which plots were kept free of weeds for 0, 10, 20, 30, 40 and 50 days after crop emergence (DAE, and then weeds were allowed to grow until harvest, and six initial weed-infested periods in which, weeds were allowed to grow for 0, 10, 20, 30, 40 and 50 DAE, then the plots were kept free of weeds until harvest. Experiment was arranged as a randomized complete block design with three replications. The results showed effect of weed competition on crop dry matter started about 40 DAE and about 90 DAE reached its maximum. The weeds competition decreased dry matter accumulation, leaf area index, crop growth rate, leaf area index duration, light absorption, light extinction coefficient and radiation use efficiency (RUE of potato. Weeds reduced the potato yield 54.8 percent. The beginning and the end of the critical period of weed control in potato (CPWC was based on 5% and 10% tuber yield loss. The onset of the CPWC ranged from 486 to 572 GDD, at 5% and 10% yield loss level corresponding to 11 and 19 days after crop emergence, respectively. The end of the CPWC varied from 1372 to 1164 GDD, at 5% and 10% yield loss level corresponding to 65 and 51 days after crop emergence, respectively. RUE in the weed infestation treatment in comparison to the weed free treatment, reduced 11.8 percent.

  16. Managing invasive plants in natural areas: Moving beyond weed control

    Science.gov (United States)

    Dean Pearson; Yvette Ortega

    2009-01-01

    Exotic invasive plants present one of the greatest challenges to natural resource management. These weeds can alter entire communities and ecosystems, substantially degrading important ecosystem services such as forage for wild and domestic herbivores, water and soil quality, recreational values, and wildlife habitat. Traditionally, weed management in natural areas has...

  17. Response of rice genotypes to weed competition in dry direct-seeded rice in India.

    Science.gov (United States)

    Mahajan, Gulshan; Ramesha, Mugalodi S; Chauhan, Bhagirath S

    2014-01-01

    The differential weed-competitive abilities of eight rice genotypes and the traits that may confer such attributes were investigated under partial weedy and weed-free conditions in naturally occurring weed flora in dry direct-seeded rice during the rainy seasons of 2011 and 2012 at Ludhiana, Punjab, India. The results showed genotypic differences in competitiveness against weeds. In weed-free plots, grain yield varied from 6.6 to 8.9 t ha(-1) across different genotypes; it was lowest for PR-115 and highest for the hybrid H-97158. In partial weedy plots, grain yield and weed biomass at flowering varied from 3.6 to 6.7 t ha(-1) and from 174 to 419 g m(-2), respectively. In partial weedy plots, grain yield was lowest for PR-115 and highest for PR-120. Average yield loss due to weed competition ranged from 21 to 46% in different rice genotypes. The study showed that early canopy closure, high leaf area index at early stage, and high root biomass and volume correlated positively with competitiveness. This study suggests that some traits (root biomass, leaf area index, and shoot biomass at the early stage) could play an important role in conferring weed competitiveness and these traits can be explored for dry-seeded rice.

  18. A new strategy for controlling invasive weeds: selecting valuable native plants to defeat them

    OpenAIRE

    2015-01-01

    To explore replacement control of the invasive weed Ipomoea cairica, we studied the competitive effects of two valuable natives, Pueraria lobata and Paederia scandens, on growth and photosynthetic characteristics of I. cairica, in pot and field experiments. When I. cairica was planted in pots with P. lobata or P. scandens, its total biomass decreased by 68.7% and 45.8%, and its stem length by 33.3% and 34.1%, respectively. The two natives depressed growth of the weed by their strong effects o...

  19. Differences between organically grown varieties of spring wheat, in response to weed competition and yield

    Directory of Open Access Journals (Sweden)

    Feledyn-Szewczyk Beata

    2015-07-01

    Full Text Available When growing wheat, one of the non-chemical methods of weed regulation is to choose wheat varieties which have a high ability to compete with weeds. The first aim of the research was the estimation of the relationships between the morphological features and canopy parameters of six spring wheat varieties. The second aim was the estimation of the varieties’ competitive ability against weeds. The third aim was the estimation of the grain yield of the six varieties. The experiment was carried out in the 2011–2013 time period, on fields which had been organically managed since 1994. Different features affected the weed infestation levels of the spring wheat varieties. For Bombona, negative correlations between the number of weeds and the height, dry matter of wheat, and wheat density, were proved. For Brawura, Hewilla, and Żura, the height, number of tillers, and dry matter of wheat were the main factors influencing weed abundance. A strong negative correlation between the number of weeds and the dry matter of wheat was found for Parabola. Cluster analysis indicated that Bombona and Brawura were the most competitive against weeds, while Monsun and Parabola were characterized as being the least competitive against weeds. Weed number significantly affected the grain yield of spring wheat (r = −0.418. The grain yield was positively correlated with the number of tillers (r = 0.459 and ears (r = 0.355, and the height (r = 0.534 and wheat dry matter (r = 0.411. Bombona and Brawura were the lowest yielding varieties (3.03 and 3.20 t · ha−1, respectively, whereas the highest yield was achieved by Żura (3.82 t · ha−1, on average.

  20. Competitive effects of introduced annual weeds on some native and reclamation species in the Powder River Basin, Wyoming

    Energy Technology Data Exchange (ETDEWEB)

    Allen, E.B.; Knight, D.H.

    1980-01-01

    Four experiments were conducted to examine the competitive effects of introduced annual weeds on certain native and reclamation species. The first experiment was initiated by discing three sites in the Powder River Basin, Wyoming, at three distances from introduced weed seed sources. Introduced weed colonization was greatest when a seed source was located nearby. Higher weed cover resulted in reductions of percent cover, density, and richness of the native species. The second experiment was conducted in the greenhouse and was designed to determine if there are changes in response of S. kali and the native grasses Agropyron smithii and Bouteloua gracilis to competition and water regime. Both grass species had lower biomass and higher stomatal resistance when growing in mixed culture with S. kali than in pure culture in the dry regime, but there were no significant differences in the wet regime. In general, the difference in plant response between mixed and pure cultures was more pronounced in the dry than in the wet regime. The third study was a greenhouse experiment on germination and competition of S. kali (a C/sub 4/ species) with native species Lepidium densiflorum (C/sub 3/), Chenopodium pratericola (C/sub 3/), A. smithii (C/sub 3/), and B. gracilis (C/sub 4/) under May, June, and July temperature regimes. Salsola kali germinated equally well in all three regimes, but the other C/sub 4/ species had highest germination in the July regime and the C/sub 3/ species in the May and June regimes. The fourth study was designed to examine the effect of weed colonization on the success of mine reclamation. Little effect was observed, but colonization by introduced annuals was very low. (ERB)

  1. Effects of fertility, weed density and crop competition on biomass partitioning in Centaurea cyanus L.

    Directory of Open Access Journals (Sweden)

    Łukasz Chachulski

    2014-01-01

    Full Text Available The influence of environmental factors on biomass partitioning of annual arable weed Centaurea cyanus was analysed. We investigated the effect of fertilisation, density and competition with the winter rye crop on the reproductive investment. Three fertiliser treatments and three density levels were applied. In Centaurea cyanus differences in the pattern of biomass allocation to reproduction are related to plant size. The relationship between reproductive and vegetative mass is close to linear. It is consistent with the model of linear size-dependent reproductive output. In Centaurea cyanus this model worked well for size differences that have been generated by interspecific competition, nutrients supply and density. Our data support the hypothesis that plastic changes in relationship between vegetative and generative biomass are environmentally-induced. Significantly different relationship between vegetative and reproductive biomass were detected among populations growing at different density and fertility levels. The fertilisation with mineral fertiliser and manure resulted in an increase of generative biomass allocated to flowerheads and a decrease of reproductive effort. Generative dry weight increased more rapidly with plant size in higher densities of population and at lower fertility levels. The experiment showed that the rate of weight allocated to reproductive structures was bigger under the pressure of competition with cereal crop. At low fertility level and high density, when the individuals were small, generative biomass increased faster with plant size. The production of seeds was not directly dependent on biomass allocated into total reproductive structures. At low level, of nutrient supply C. cyanus gave more offspring per gram of its biomass. We discuss the results in context of life-history theory. From the strategic point of view, size-dependent variation in reproductive effort and in efficiency of reproduction can be

  2. Impact of preceding crop on alfalfa competitiveness with weeds

    Science.gov (United States)

    Organic producers would like to include no-till practices in their farming systems. We are seeking to develop a continuous no-till system for organic farming, based on a complex rotation that includes a 3-year sequence of alfalfa. In this study, we evaluated impact of preceding crop on weed infest...

  3. Effect of crop density on competition by wheat and barley with Agrostemma githago and other weeds

    DEFF Research Database (Denmark)

    Doll, H.; Holm, U.; Søgaard, B.

    1995-01-01

    The effect of Agrostemma githago L. and other naturally occurring weeds on biomass production and grain yield was studied in winter wheat and winter barley. Naturally occurring weeds had only a negligible effect on barley, but reduced wheat grain yield by 10% at a quarter of normal crop density....... The interaction between the cereals and A. githago was studied in additive series employing different crop densities. Growth of this weed species was strongly dependent on crop density, which was more important for controlling weed growth than it was for obtaining a normal grain yield. Wheat and especially barley...... had a better competitive ability than A. githago. Wheat and A. githago utilized resources for growth better when grown in mixture than when grown in pure stands as the relative yield totals were significantly larger than unity....

  4. Trait-based characterisation of soil exploitation strategies of banana, weeds and cover plant species

    Science.gov (United States)

    Tardy, Florence; Damour, Gaëlle; Dorel, Marc; Moreau, Delphine

    2017-01-01

    Cover plants can be introduced in cropping systems to provide agroecosystem services, including weed control via competition for resources. There is currently no consensus on how to identify the best cover plant species, while trait-based approaches are promising for screening plant species due to their agroecosystem service provision potential. This study was carried out to characterize soil exploitation strategies of cover plant species in banana agroecosystems using a trait-based approach, and in turn identify cover plant species with a high weed control potential via competition for soil resources in banana cropping systems. A field experiment was conducted on 17 cover plant species, two weed species and two banana cultivars grown individually. Four functional traits were measured. Two of them (i.e., the size of the zone explored by roots and the root impact density) were used to characterize root system soil exploration patterns. Two other traits (i.e., specific root length and root diameter) were used to characterize resource acquisition within the soil zone explored by the roots. All studied traits exhibited marked variations among species. The findings suggested a trade-off between the abilities of species to develop a limited number of large diameter roots exploring a large soil zone versus many thin roots exploring a smaller soil zone. Three soil-resource exploitation strategies were identified among species: (i) with large diameter roots that explore a large soil zone; (ii) with small diameter roots and a high specific length that explore a smaller soil zone; and (iii) with a high total root-impact density and an intermediate specific root length that explore the uppermost soil layers. Interestingly, in our panel of species, no correlations with regard to belowground and aboveground strategies were noted: species with an acquisitive belowground strategy could display an acquisitive or a conservative aboveground strategy. The findings of this study

  5. Trait-based characterisation of soil exploitation strategies of banana, weeds and cover plant species.

    Science.gov (United States)

    Tardy, Florence; Damour, Gaëlle; Dorel, Marc; Moreau, Delphine

    2017-01-01

    Cover plants can be introduced in cropping systems to provide agroecosystem services, including weed control via competition for resources. There is currently no consensus on how to identify the best cover plant species, while trait-based approaches are promising for screening plant species due to their agroecosystem service provision potential. This study was carried out to characterize soil exploitation strategies of cover plant species in banana agroecosystems using a trait-based approach, and in turn identify cover plant species with a high weed control potential via competition for soil resources in banana cropping systems. A field experiment was conducted on 17 cover plant species, two weed species and two banana cultivars grown individually. Four functional traits were measured. Two of them (i.e., the size of the zone explored by roots and the root impact density) were used to characterize root system soil exploration patterns. Two other traits (i.e., specific root length and root diameter) were used to characterize resource acquisition within the soil zone explored by the roots. All studied traits exhibited marked variations among species. The findings suggested a trade-off between the abilities of species to develop a limited number of large diameter roots exploring a large soil zone versus many thin roots exploring a smaller soil zone. Three soil-resource exploitation strategies were identified among species: (i) with large diameter roots that explore a large soil zone; (ii) with small diameter roots and a high specific length that explore a smaller soil zone; and (iii) with a high total root-impact density and an intermediate specific root length that explore the uppermost soil layers. Interestingly, in our panel of species, no correlations with regard to belowground and aboveground strategies were noted: species with an acquisitive belowground strategy could display an acquisitive or a conservative aboveground strategy. The findings of this study

  6. Determination of plant height for weed detection in stereoscopic images

    OpenAIRE

    Piron, Alexis; Leemans, Vincent; Kleynen, Olivier; Destain, Marie-France

    2008-01-01

    The aim of this study was twofold. The first goal was to acquire high accuracy stereoscopic images of small-scale field scenes, the second to examine the potential of plant height as a discriminant factor between crop and weed, within carrot rows. Emphasis was put on how to determine actual plant height taking into account the variable distance from camera to ground and ground irregularities for in-field measurements. Multispectral stereoscopic images were taken over a period o...

  7. Using thermal units for estimating critical period of weed competition in off-season maize crop.

    Science.gov (United States)

    López-Ovejero, Ramiro Fernando; y Garcia, Axel Garcia; de Carvalho, Saul Jorge P; Christoffoleti, Pedro J; Neto, Durval Dourado; Martins, Fernando; Nicolai, Marcelo

    2005-01-01

    Brazilian off-season maize production is characterized by low yield due to several factors, such as climate variability and inadequate management practices, specifically weed management. Thus, the goal of this study was to determinate the critical period of weed competition in off-season maize (Zea mays L.) crop using thermal units or growing degree days (GDD) approach to characterize crop growth and development. The study was carried out in experimental area of the University of São Paulo, Brazil, with weed control (C), as well as seven coexistence periods, 2, 4, 6, 8, and 12 leaves, flowering, and all crop cycle; fourteen treatments were done. Climate data were obtained from a weather station located close to the experimental area. To determine the critical period for weed control (CPWC) logistic models were fitted to yield data obtained in both W and C, as a function of GDD. For an arbitrary maximum yield loss fixed in 2.5%, the CPWC was found between 301 and 484 GDD (7-8 leaves). Also, when the arbitrary loss yield was fixed in 5 and 10%, the period before interference (PBI) was higher than the critical weed-free period (CWFP), suggesting that the weeds control can be done with only one application, between 144 and 410 GDD and 131 and 444 GDD (3-8 leaves), respectively. The GDD approach to characterize crop growth and development was successfully used to determine the critical period of weeds control in maize sown off-season. Further works will be necessary to better characterize the interaction and complexity of maize sown off-season with weeds. However, these results are encouraging because the possibility of the results to be extrapolated and because the potential of the method on providing important results to researchers, specifically crop modelers.

  8. A new strategy for controlling invasive weeds: selecting valuable native plants to defeat them

    Science.gov (United States)

    Li, Weihua; Luo, Jianning; Tian, Xingshan; Soon Chow, Wah; Sun, Zhongyu; Zhang, Taijie; Peng, Shaolin; Peng, Changlian

    2015-06-01

    To explore replacement control of the invasive weed Ipomoea cairica, we studied the competitive effects of two valuable natives, Pueraria lobata and Paederia scandens, on growth and photosynthetic characteristics of I. cairica, in pot and field experiments. When I. cairica was planted in pots with P. lobata or P. scandens, its total biomass decreased by 68.7% and 45.8%, and its stem length by 33.3% and 34.1%, respectively. The two natives depressed growth of the weed by their strong effects on its photosynthetic characteristics, including suppression of leaf biomass and the abundance of the CO2-fixing enzyme RUBISCO. The field experiment demonstrated that sowing seeds of P. lobata or P. scandens in plots where the weed had been largely cleared produced 11.8-fold or 2.5-fold as much leaf biomass of the two natives, respectively, as the weed. Replacement control by valuable native species is potentially a feasible and sustainable means of suppressing I. cairica.

  9. The role of plant-microbiome interactions in weed establishment and control.

    Science.gov (United States)

    Trognitz, Friederike; Hackl, Evelyn; Widhalm, Siegrid; Sessitsch, Angela

    2016-10-01

    The soil microbiome plays an important role in the establishment of weeds and invasive plants. They associate with microorganisms supporting their growth and health. Weed management strategies, like tillage and herbicide treatments, to control weeds generally alter soil structure going alongside with changes in the microbial community. Once a weed population establishes in the field, the plants build up a close relationship with the available microorganisms. Seeds or vegetative organs overwinter in soil and select early in the season their own microbiome before crop plants start to vegetate. Weed and crop plants compete for light, nutrition and water, but may differently interact with soil microorganisms. The development of new sequencing technologies for analyzing soil microbiomes has opened up the possibility for in depth analysis of the interaction between 'undesired' plants and crop plants under different management systems. These findings will help us to understand the functions of microorganisms involved in crop productivity and plant health, weed establishment and weed prevention. Exploitation of the knowledge offers the possibility to search for new biocontrol methods against weeds based on soil and plant-associated microorganisms. This review discusses the recent advances in understanding the functions of microbial communities for weed/invasive plant establishment and shows new ways to use plant-associated microorganisms to control weeds and invasive plants in different land management systems.

  10. The competitive ability of pea–barley intercrops against weeds and the interactions with crop productivity and soil N availability

    DEFF Research Database (Denmark)

    Corre-Hellou, G.; Dibet, A.; Hauggaard-Nielsen, Henrik

    2011-01-01

    Grain legumes, such as peas (Pisum sativum L.), are known to be weak competitors against weeds when grown as the sole crop. In this study, the weed-suppression effect of pea–barley (Hordeum vulgare L.) intercropping compared to the respective sole crops was examined in organic field experiments...... (2003–2005). The weed biomass was three times higher under the pea sole crops than under both the intercrops and barley sole crops at maturity. The inclusion of joint experiments in several countries and various growing conditions showed that intercrops maintain a highly asymmetric competition over...... weeds, regardless of the particular weed infestation (species and productivity), the crop biomass or the soil nitrogen availability. The intercropping weed suppression was highly resilient, whereas the weed suppression in pea sole crops was lower and more variable. The pea–barley intercrops exhibited...

  11. Arbuscular mycorrhizal associations and occurrence of dark septate endophytes in the roots of Brazilian weed plants.

    Science.gov (United States)

    Massenssini, André Marcos; Bonduki, Víctor Hugo Araújo; Tótola, Marcos Rogério; Ferreira, Francisco Affonso; Costa, Maurício Dutra

    2014-02-01

    The ecology of weed plants includes their interactions with soil microorganisms, such as mutualistic partners that may contribute to their adaptation and competitive success in the agricultural fields. Despite the importance of microorganisms to plant growth, knowledge on weed-symbiont associations is still incipient compared to crops. Thus, a survey for the presence of arbuscular mycorrhiza (AM) and dark septate endophyte (DSE) associations in the roots of 50 weed species was done in three distinct areas during the dry and rainy seasons. We found that 41 and 29 out of the 50 species were associated with AM fungi and DSE, respectively, and 27 species presented both associations. All the plant species not forming AM belong to families thought to be nonmycorrhizal, such as Amaranthaceae, Commelinaceae, Brassicaceae, and Cyperaceae. The most common morphotype of AM observed was the Arum-type. No significant differences were found in root length colonization between the areas or seasons. For 19 species surveyed, this is the first report on their mycorrhizal status.

  12. Relative contributions of allelopathy and competitive traits to the weed suppressive ability of winter wheat lines against Italian ryegrass

    Science.gov (United States)

    Allelopathy and competitive ability have been identified as independent factors contributing to the weed suppressive ability of crop cultivars; however, it is not clear whether these factors have equal influence on weed suppression outcomes of winter wheat (Triticum aestivum L.) lines in the field. ...

  13. Competition increases sensitivity of wheat (Triticum aestivum to biotic plant-soil feedback.

    Directory of Open Access Journals (Sweden)

    W H Gera Hol

    Full Text Available Plant-soil feedback (PSF and plant competition play an important role in structuring vegetation composition, but their interaction remains unclear. Recent studies suggest that competing plants could dilute pathogenic effects, whereas the standing view is that competition may increase the sensitivity of the focal plant to PSF. In agro-ecosystems each of these two options would yield contrasting outcomes: reduced versus enhanced effects of weeds on crop biomass production. To test the effect of competition on sensitivity to PSF, we grew Triticum aestivum (Common wheat with and without competition from a weed community composed of Vicia villosa, Chenopodium album and Myosotis arvensis. Plants were grown in sterilized soil, with or without living field inoculum from 4 farms in the UK. In the conditioning phase, field inocula had both positive and negative effects on T. aestivum shoot biomass, depending on farm. In the feedback phase the differences between shoot biomass in T. aestivum monoculture on non-inoculated and inoculated soils had mostly disappeared. However, T. aestivum plants growing in mixtures in the feedback phase were larger on non-inoculated soil than on inoculated soil. Hence, T. aestivum was more sensitive to competition when the field soil biota was present. This was supported by the statistically significant negative correlation between shoot biomass of weeds and T. aestivum, which was absent on sterilized soil. In conclusion, competition in cereal crop-weed systems appears to increase cereal crop sensitivity to soil biota.

  14. Competition increases sensitivity of wheat (Triticum aestivum) to biotic plant-soil feedback.

    Science.gov (United States)

    Hol, W H Gera; de Boer, Wietse; ten Hooven, Freddy; van der Putten, Wim H

    2013-01-01

    Plant-soil feedback (PSF) and plant competition play an important role in structuring vegetation composition, but their interaction remains unclear. Recent studies suggest that competing plants could dilute pathogenic effects, whereas the standing view is that competition may increase the sensitivity of the focal plant to PSF. In agro-ecosystems each of these two options would yield contrasting outcomes: reduced versus enhanced effects of weeds on crop biomass production. To test the effect of competition on sensitivity to PSF, we grew Triticum aestivum (Common wheat) with and without competition from a weed community composed of Vicia villosa, Chenopodium album and Myosotis arvensis. Plants were grown in sterilized soil, with or without living field inoculum from 4 farms in the UK. In the conditioning phase, field inocula had both positive and negative effects on T. aestivum shoot biomass, depending on farm. In the feedback phase the differences between shoot biomass in T. aestivum monoculture on non-inoculated and inoculated soils had mostly disappeared. However, T. aestivum plants growing in mixtures in the feedback phase were larger on non-inoculated soil than on inoculated soil. Hence, T. aestivum was more sensitive to competition when the field soil biota was present. This was supported by the statistically significant negative correlation between shoot biomass of weeds and T. aestivum, which was absent on sterilized soil. In conclusion, competition in cereal crop-weed systems appears to increase cereal crop sensitivity to soil biota.

  15. Using simulation models to investigate the cumulative effects of sowing rate, sowing date and cultivar choice on weed competition.

    Science.gov (United States)

    Andrew, Izzadora K S; Storkey, Jonathan

    2017-05-01

    With the increasing pressure on crop production from the evolution of herbicide resistance, farmers are increasingly adopting Integrated Weed Management (IWM) strategies to augment their weed control. These include measures to increase the competitiveness of the crop canopy such as increased sowing rate and the use of more competitive cultivars. While there are data on the relative impact of these non-chemical weed control methods assessed in isolation, there is uncertainty about their combined contribution, which may be hindering their adoption. In this article, the INTERCOM simulation model of crop/weed competition was used to examine the combined impact of crop density, sowing date and cultivar choice on the outcomes of competition between wheat (Triticum aestivum) and Alopecurus myosuroides. Alopecurus myosuroides is a problematic weed of cereal crops in North-Western Europe and the primary target for IWM in the UK because it has evolved resistance to a range of herbicides. The model was parameterised for two cultivars with contrasting competitive ability, and simulations run across 10 years at different crop densities and two sowing dates. The results suggest that sowing date, sowing density and cultivar choice largely work in a complementary fashion, allowing enhanced competitive ability against weeds when used in combination. However, the relative benefit of choosing a more competitive cultivar decreases at later sowing dates and higher crop densities. Modeling approaches could be further employed to examine the effectiveness of IWM, reducing the need for more expensive and cumbersome long-term in situ experimentation.

  16. On weed competition and population dynamics : considerations for crop rotations & organic farming

    NARCIS (Netherlands)

    Mertens, S.K.

    2002-01-01

    Key words: organic farming, weeds, weed management, weed ecology, weed diversity, matrix population model, elasticity analysis, neighbourhood model, survey, crop row spacing, mechanical hoe, harrow, Polygonum convolvulus ,

  17. SOME FACTORS IN THE COMPETITION OR ANTAGONISM AMONG BACTERIA, ALGAE, AND AQUATIC WEEDS.

    Science.gov (United States)

    Filzgerald, G P

    1969-12-01

    Field observations of changes in the populations of aquatic weeds and phytoplankton have confirmed that aquatic weeds have antagonistic activity toward phytoplankton. Nutritional studies in the laboratory indicate that cultures of the aquatic weeds, Myriophyllum sp., Ceratophyllum sp., and duckweed (Lemma minor L.); liquid cultures of barley (Hordeum vulgare L., Dickson variety); and cultures of the filamentous green algae, Cladophora sp. and Pithophora oedogonium (Mont.) Withrock, will remain relatively free of epiphytes or competing phytoplankton if the cultures are nitrogen-limited. Field observations of Cladophora sp. have confirmed that the growth of epiphytes on the Cladophora is related to conditions of surplus available nitrogen compounds. It is proposed that this antagonistic activity may be due to a "nitrogen sink" effect in which the aquatic weeds or filamentous green algae prevent the growth of contaminating algae by competition for the limited nitrogen compounds available. However, the presence of bacteria-sized organisms which have selective toxicity to certain algae indicates that perhaps multiple factors exist. Discussed are the ecological implications of associations of certain algae with bacteria that have selective toxicities for other species of algae under certain environmental conditions such as nitrogen-limited growth.

  18. Weed management, training, and irrigation practices for organic production of trailing blackberry: II. Soil and plant nutrient concentrations

    Science.gov (United States)

    Organic production of blackberries is increasing, but there is relatively little known about how production practices affect plant and soil nutrient status. The impact of cultivar (‘Black Diamond’ and ‘Marion’), weed management (weed mat, hand weeding, and no weeding), primocane training time (Augus...

  19. Características de plantas de cultivares de arroz irrigado relacionadas à habilidade competitiva com plantas concorrentes Characteristics of flooded rice cultivar plants related to competitive ability against weeds concurrent plants

    Directory of Open Access Journals (Sweden)

    N.G. Fleck

    2003-04-01

    Full Text Available Plantas que apresentam rápido crescimento tendem a ocupar precocemente nichos disponíveis, utilizando o espaço de suas vizinhas. Em geral, esses vegetais adquirem prioridade na utilização dos recursos do meio. O objetivo deste trabalho foi avaliar variações em características de crescimento de cultivares de arroz irrigado. Para isso, conduziu-se um experimento em campo na estação de crescimento de 2000/2001, em Cachoeirinha-RS. Investigou-se o comportamento de oito cultivares de arroz, cultivados em presença e ausência de plantas de arroz do cultivar EEA 406, simulando infestação de arroz-vermelho, estabelecida com densidade média de 30 plantas m-2. Entre 15 e 60 dias após a semeadura (DAS, avaliou-se a evolução de área foliar, estatura e massa aérea das plantas de arroz. Com esses dados, calcularam-se razão de área foliar (RAF, taxa de crescimento relativo (TCR e taxa de assimilação líquida (TAL dos cultivares. Os cultivares Ligeirinho e XL 6 apresentaram elevadas velocidades de ganho em área foliar, estatura e massa aérea; com isso, alcançaram as maiores coberturas do solo, juntamente com o cultivar IR 841. Por outro lado, os cultivares Bluebelle e Formosa mostraram lento crescimento absoluto no período avaliado, mas, em geral, apresentaram os maiores valores para TCR e TAL.Fast-growing plants tend to occupy available niches utilizing these spaces ahead of their neighbors. In general, these plants have priority over others in the use of environmental resources. The objective of this research was to evaluate variations in growth characteristics of flooded rice cultivars. A field experiment was carried out during the 2000/01 summer season, in Cachoeirinha, RS, Brazil. The behavior of eight rice cultivars, grown in the absence or presence of the EEA 406 rice genotype was investigated, simulating a red rice infestation, established at an average density of 30 plants m-2. From 15 to 60 days after seeding (DAS

  20. Host plant resistance to parasitic weeds; recent progress and bottlenecks.

    Science.gov (United States)

    Yoder, John I; Scholes, Julie D

    2010-08-01

    Parasitic witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.) directly invade the roots of crop plants connecting to the vascular system and abstracting nutrients and water. As a consequence they cause devastating losses in crop yield. Genetic resistance to parasitic weeds is a highly desirable component of any control strategy. Resistance to parasitic plants can occur at different stages of the parasite lifecycle: before attachment to the host, during penetration of the root or after establishment of vascular connections. New studies are beginning to shed light on the molecular mechanisms and signaling pathways involved in plant-plant resistance. The first resistance gene to Striga, encoding a CC-NBS-LRR Resistance protein (R) has been identified and cloned suggesting that host plants resist attack from parasitic plants using similar surveillance mechanisms as those used against fungal and bacterial pathogens. It is becoming clear that the salicylic acid (SA) signaling pathway plays an important role in resistance to parasitic plants and genes encoding pathogenesis-related (PR) proteins are upregulated in a number of the resistant interactions. New strategies for engineering resistance to parasitic plants are also being explored, including the expression of parasite-specific toxins in host roots and RNAi to silence parasite genes crucial for development.

  1. Delimitacion del periodo critico de competencia de malezas en el cultivo de lino (Linum usitatissimum Determination of the critical period of weed competition in linseed (Linum usitatissimum

    Directory of Open Access Journals (Sweden)

    R.A. Barreyro

    2002-12-01

    Full Text Available La planta de lino oleaginoso es especialmente sensible a la competencia con malezas, que limita el rendimiento potencial. El objetivo de este trabajo fue delimitar el período crítico de competencia del lino con una comunidad natural de malezas. Se realizó una experiencia de campo durante 1993, 1994 y 1995 en La Plata, Argentina. Los tratamientos consistieron en mantener el lino con y sin presencia de malezas en distintas etapas de su desarrollo. La comunidad de malezas fue evaluada en su composición y producción de materia seca y el cultivo en su rendimiento en semillas y componentes. El período crítico se delimitó entre los 30 y 80 días después de la siembra. En este período, la disminución de rendimiento de lino respecto del testigo sin malezas fue superior al 10%. La disminución de rendimiento del cultivo totalmente enmalezado fue del 79% respecto del desmalezado todo el ciclo. Fue afectado el número de semillas por planta ya que su definición está incluida en el período delimitado. Los resultados obtenidos sugieren que las alternativas de control deben considerar el período crítico y también propiciar su utilización en modelos de predicción.Linseed plant is especially sensitive to weed competition, which limits its potential yield. The aim of this work was to determine the critical period of linseed competition with a natural weed community. A field experiment was carried out in 1993, 1994 and 1995 in La Plata, Argentina. Treatments consisted of keeping linseed with and without weeds at different stages of development. Weed composition and dry biomass, and linseed yield and its components were evaluated. The critical period of competition was determined, starting at 30 days and ending 80 days after crop seeding. Linseed yield decrease was greater than 10% during the critical period of competition,when compared to the check plot kept without competition. The maximum yield decrease of the check plot kept totally weeded

  2. Weed seed production, crop planting pattern, and mechanical weeding in wheat

    NARCIS (Netherlands)

    Mertens, S.K.; Jansen, J.

    2002-01-01

    Experiments were carried out to investigate weed seed production in widely spaced spring wheat crops that received aggressive mechanical weed control (hoeing and harrowing) compared with that in narrowly spaced crops receiving less aggressive mechanical control (harrowing only). Three species (wild

  3. Status of weeds as reservoirs of plant parasitic nematodes in banana fields in Martinique

    OpenAIRE

    Quénéherve, Patrick; Chabrier, C.; Auwerkerken, Annemie; Topart, Patrick; Martiny, Bernard; Marie Luce, S.

    2006-01-01

    During a survey of the nematodes associated with weeds in banana fields in Martinique, 41 weed species in 37 genera from 20 plant families were collected to extract nematodes from the roots. Results of this survey showed that 24 weed species were hosts of Radopholus similis, 23 were hosts of Helicotylenchus spp., 13 were hosts of Pratylenchus spp., 13 were hosts of Hoplolaimus seinhorsti, 29 were hosts of Meloidogyne spp. and 24 were hosts of Rotylenchulus reniformis. The presence of the burr...

  4. Weed management in banana production: The use of Nelsonia ...

    African Journals Online (AJOL)

    EJIRO

    reduced in banana grown with N. canescens cover crop than in plants grown without. ... benefiting the soil and other crops (SAN, 1996; Creamer ... canopy that is more competitive than weeds for light, ... suppress weeds, to what extent it affects banana yield as .... time taken in weeding plots with cover crop was about a.

  5. Weed Interference Affects Dry Bean Yield and Growth

    Directory of Open Access Journals (Sweden)

    Hossein GHAMARI

    2012-08-01

    Full Text Available Dry bean is one of the most important pulse crops in Iran. Field study was conducted in 2011 to evaluate effects of weed competition from a natural flora on growth and yield of dry bean (Phaseolus vulgaris L.. The treatments consisted of weed infestation and weed removal periods (10, 20, 30, 40 and 50 days after crop emergence. Control plots kept weed-infested and weed-free throughout growing season. To assess the weed competition effect on crop characteristics, Richards, Gompertz and logistic equations were fitted to the data. The most abundant weed species were Chenopodium album and Amaranthus retroflexus. Increase in duration of weed interference decreased the stem height of dry bean. At the end of the growing season, dry bean was 20 cm taller in season-long weed-free treatment compared to the season-long weed-infested treatment. As the number of days of weed interference increased, a declining trend of LAI and number of pods was observed. The minimum number of pods was obtained in season-long weed-infested treatment (5.01 pods/plant. Weed interference during the whole growing season, caused a 60% reduction in yield. Considering 5% and 10% acceptable yield lost, the critical period of weed competition was determined from 20 to 68 and 23 to 55 days after planting (DAE, respectively.

  6. Crop weed competition and herbicide performance in cereal species and varieties

    DEFF Research Database (Denmark)

    Christensen, Svend

    1994-01-01

    In dose-response experiments with the herbicide combinations MCPA+dichlorprop and ioxynil+mecoprop in barley, winter wheat, and winter rye varieties, oilseed rape (Brassica napus L.) was used as a substitute for weeds. The results showed a significant interaction between the competitive ability...... war es erforderlich, eine 154 % höhere Herbiziddosis als bei der Wintergerstensorte Trixi anzuwenden, während die Herbiziddosis bei der Winterroggensorte Petkus II im Vergleich zu Trixi um 31 % reduziert werden konnte. Die Unterschiede waren bei Sommergerstensorten geringer, jedoch signifikant....

  7. What do we really know about alien plant invasion? A review of the invasion mechanism of one of the world's worst weeds.

    Science.gov (United States)

    Bajwa, Ali Ahsan; Chauhan, Bhagirath Singh; Farooq, Muhammad; Shabbir, Asad; Adkins, Steve William

    2016-07-01

    This review provides an insight into alien plant invasion taking into account the invasion mechanism of parthenium weed ( Parthenium hysterophorus L.). A multi-lateral understanding of the invasion biology of this weed has pragmatic implications for weed ecology and management. Biological invasions are one of the major drivers of restructuring and malfunctioning of ecosystems. Invasive plant species not only change the dynamics of species composition and biodiversity but also hinder the system productivity and efficiency in invaded regions. Parthenium weed, a well-known noxious invasive species, has invaded diverse climatic and biogeographic regions in more than 40 countries across five continents. Efforts are under way to minimize the parthenium weed-induced environmental, agricultural, social, and economic impacts. However, insufficient information regarding its invasion mechanism and interference with ecosystem stability is available. It is hard to devise effective management strategies without understanding the invasion process. Here, we reviewed the mechanism of parthenium weed invasion. Our main conclusions are: (1) morphological advantages, unique reproductive biology, competitive ability, escape from natural enemies in non-native regions, and a C3/C4 photosynthesis are all likely to be involved in parthenium weed invasiveness. (2) Tolerance to abiotic stresses and ability to grow in wide range of edaphic conditions are thought to be additional invasion tools on a physiological front. (3) An allelopathic potential of parthenium weed against crop, weed and pasture species, with multiple modes of allelochemical expression, may also be responsible for its invasion success. Moreover, the release of novel allelochemicals in non-native environments might have a pivotal role in parthenium weed invasion. (4) Genetic diversity found among different populations and biotypes of parthenium weed, based on geographic, edaphic, climatic, and ecological ranges, might also

  8. EFFECTS OF PLANTING DATE AND SPATIAL ARRANGEMENT ON COMMON BEAN (Phaseolus vulgaris) YIELD UNDER WEED-FREE AND WEEDY CONDITIONS

    National Research Council Canada - National Science Library

    ESMAEILZADEH, S; AMINPANAH, H

    2015-01-01

    ABSTRACTTo evaluate the effect of planting date and spatial pattern on common bean yield under weed-free and weed-infested conditions, an experiment was conducted in Kelachay, Northern Iran, in 2013...

  9. Effects of hand weeding strip and nitrogen fertilizer on corn plants.

    Science.gov (United States)

    da Silva, João Renato Vaz; Martins, Dagoberto; Cardoso, Leonildo A; Carbonari, Caio Antonio

    2005-01-01

    The objective of the present research was to evaluate effects of different strip weed control associated with nitrogen fertilizer on corn applied after planting. The experiment was set and conducted in Botucatu, São Paulo State, Brazil, and the hybrid planted was Dekalb 333-B. A completely randomized block design with four replications was used. Experimental plots were disposed as a factorial scheme 2 x 2 x 4, constituted by two types of weeding on row (with or without manual hoeing), two types of weeding on inter-row (with or without manual hoeing), and four nitrogen levels applied after planting (00, 60, 90, and 120 kg ha(-1)). Plots were composed by six rows with 5 m length. Nitrogen fertilizer was applied at 35 days after emergence (d.a.e). For weed community it was evaluated: weed density, dominancy, frequency, and relative importance. The main weed species were: Brachiaria plantiginea, Amaranthus retroflexus, Bidens pilosa, Cyperus rotunds, Brachiaria decumbens, Euphorbia heterofila, Oxalis latifolia, Acanthospermum hispidum, Commelina benghalensis. It was evaluated corn height at 40 and 100 d.a.e., first ear insertion height at 100 d.a.e., and final grain yield at harvesting. Plants and first ear insertion height were affected when nitrogen fertilizer was not applied. Treatments without weed control showed that weed interfered negatively with plants height. There were no correlation between weeds and nitrogen fertilizer for all parameters evaluated. Parcels without weed showed the highest ear weights and final grain production. Treatments that received nitrogen fertilizer, independently of studied arrangement, provided higher yields.

  10. Formation of Plant Canopy Hierarchies and Consequences for Water Use: Insights From Field Experiments and Individual Based Modeling of Weed-Crop Interactions

    Science.gov (United States)

    Berger, A. G.; McDonald, A. J.; Riha, S. J.

    2008-12-01

    In an agricultural landscape, water use is tightly linked to the dynamics of canopy development. When weeds are present, the plant community may develop leaf area faster than crop monocultures and several hierarchies of plants may be formed. The position of each individual plant within these hierarchies depends on the spatial arrangement of the plants, the initial sizes, and the availability of resources as determined by management, soil properties, weather, and competition. Together, these factors establish a highly dynamic system with nonlinear responses to the availability of resources (e.g. soil water) that is reflected in high levels of site and regional variability in crop yield losses due to weed interference. We developed a spatially-explicit, individual based model of plant competition to evaluate dynamic outcomes of crop-weed interactions and implications for water use. The model simulates the growth of individual plants using the light interception algorithms of the forest model MAESTRA, and estimates photosynthesis through the Farquhar-vonCaemmerer method. Transpiration and photosynthesis are coupled through stomatal conductance. Maximum stomatal conductance is determined by the photosynthetic demand for CO2, but under water stress, actual transpiration per plant is used to estimate stomatal conductance and then the actual rate of photosynthesis. We also used a novel approach to estimate profile water uptake, scaling the root zone of influence (volume of soil exploited by each individual plant) to plant biomass. Additive field experiments with maize in monoculture and in combination with high-density stands of a common annual weed species (A. theophrasti M.) were established to test model performance. Despite exceptionally dry conditions in the field in some years, we found no evidence that the maize-weed mixtures had less total soil water or different rates of water extraction through the profile than the maize monocrop. Furthermore, time series

  11. The effects of weed-crop competition on nutrient uptake as affected by crop rotation and fertilizers.

    Science.gov (United States)

    Mohammaddoust-E-Chamanabad, Hamid Reza; Asghari, Ali; Tulikov, Aleksander Mikhailovic

    2007-11-15

    A field study at the Agricultural University of Timiriazev, Moscow, was conducted to determine the effect of crop rotation and Long-term fertilizer application on differences in the competitive ability of spring barley and weeds to nutrient uptake in 2004 and 2005. Spring barley was cultivated in continuous and in crop rotation with winter rye, potato, clover, flax and fallow, with and without NPK application since 1912. Spring barley, especially in no fertilizer plots grown in crop rotation has greater dry mass than spring barley grown in continuous. While dry weed mass markedly decreased in crop rotation. Decrease dry weeds mass was greater when NPK had applied. The statistical analyses show that when spring barley grew in competition with weeds in the no fertilizer plots, crop rotation significantly increased nutrient content in spring barley, but when fertilizer applied the content of N, P2O5 and K2O in barley did not change. Lowest weeds nutrient content observed where soil fertility was increased by crop rotation and NPK application. Crop rotation significantly increased total nutrient uptake of soils by spring barley, but decreased total nutrient uptake by weeds.

  12. The Effect of Different Levels of Nitrogen Fertilizer on Yield and Agronomic Characteristics of Basil (Ocimum basilicum L. Intercropped with Cowpea (Vigna unguiculata L. and Affected by Weed Competition

    Directory of Open Access Journals (Sweden)

    H. Abadian

    2016-02-01

    Full Text Available In order to study the intercropping of basil (Ocimum basiilicum L. and cowpea (Vigna unguiculata  L. under different levels of nitrogen supply and weed competition conditions, a field experiment was carried out in split-split plot arrangement based on a randomized complete block design with three replications during 2010 and 2011 at Sari Agricultural Science and Natural Resources University. Experimental factors included weed treatment (weed free and weed infested, three levels of nitrogen fertilizer (0, 50 and 100 kg ha-1, and different planting ratios (monoculture of cowpea and basil, additive planting ratio 25, 50 and 75% basil. In weed control conditions, the maximum yield of cowpea (684 kg ha-1 and dry matter yield of basil (420 kg ha-1 were belonged to 20, 50 percent of basil ratio and 50 and100 kg ha-1 nitrogen fertilizers, respectively. The highest amount of essence yield in weed free and weed infested were 69.24 and 70.40 percent as compared to the basil monocropping which belonged to 50 and 25 percent of additive basil intercropping with 100 kg ha-1 nitrogen application, respectively. Also, the dry weight of shoot and oil yield in monoculture treatments were significantly higher than intercropping. The leaf percent and the ratio of leaf and flower to stem in basil plant were significantly lower in monocropping than intercropping. In weed infested conditions, the highest percentage of stem (62.18 and basil dry yield (160 kg ha-1 were recorded in 25 percent of basil ratio and 100 kg ha-1 of nitrogen application. Also, the highest system productivity index (1517 and land equivalent ratio (LER=1.31 were belonged to 50 percent of basil ratio and 50 kg ha-1of nitrogen fertilizer in weed free conditions which shows that intercropping is more efficient than monocropping.

  13. Belowground microbes mitigate plant-plant competition.

    Science.gov (United States)

    Fonseca, Márcia Bacelar; Dias, Teresa; Carolino, Maria Manuela; França, Marcel Giovanni Costa; Cruz, Cristina

    2017-09-01

    Dimorphandra wilsonii, a Cerrado endemic Fabaceae tree, is threatened by land-use changes. The few remaining individuals occur in areas dominated by alien grasses like Urochloa decumbens. We tested the impact of nitrogen (N) availability and symbionts' presence on mitigating the effects of competition from U. decumbens. Dimorphandra wilsonii seedlings were 50-week pot-cultivated under limiting (3mM) or non-limiting (10mM) N, with or without U. decumbens, and inoculated or not with a N-fixer (Bradyrhizobium sp.) and an arbuscular mycorrhizal fungus (AMF - Glomus etunicatum), both forming symbioses in the field. Since D. wilsonii seedlings grew more and 'lost' fewer nutrients under the symbionts' presence, symbionts mitigated plant-plant competition. Under limiting N, inoculated D. wilsonii seedlings grew more (despite no nodulation), but N fixation was only suggested when inoculated D. wilsonii seedlings competed with U. decumbens. D. wilsonii(13)C, and substrate's carbon and respiration suggest that only the microbes performing key functions received plant carbon. Under non-limiting N, inoculated D. wilsonii seedlings became enriched in (13)C, substrate accumulated carbon and microbial respiration increased, suggesting a more generalist microbial community. Data suggest inoculating D. wilsonii seeds/seedlings with AMF and N-fixers as a conservation measure. However, long-term field-studies need to confirm these conclusions. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Effect of Weed Interference on Yield and Agronomical Characteristics of Fenugreek (Trigonella foenum gracum in Different Plant Density under Birjand Conditions

    Directory of Open Access Journals (Sweden)

    R Baradaran

    2016-02-01

    grain yield, plant height, biological yield, number of branches per plant and harvest index were measured. Ultimate performance were measured when the plant pods were yellow and dried. At the beginning of each plot five plants randomly chosen to measure the morphological characteristics and traits in yield components were recorded and then removed 50 cm of the margins of the plot, the rest were taken to determine the function. Analysis of variance and statistical analysis was performed using SAS and Excel softwares, Mean comparison was done by Duncan test at 5 percent. Results and Discussion Analysis of variance showed that the density and weed interference were significant at 1 and 5 percent, respectively. The interaction between density and weed interference on yield was significant at 5% level too. By prolonging the period of weed interference, the yield fell to the lowest amount of weeding treatments. The significance of the interaction between density and weed interference represents different responses in different levels of compression performance is to weed competition. In general, the choice of planting density and suitable crop can reduce weeds, increase competitive ability of the crop and increase its performance. Biological yield was significantly affected by the plant density. The density of planting, the maximum density of 40 plants (325.56 grams per square meter and the lowest density of 10 plants (232.66 grams per square meter and biomass production. Biological yield was not affected significantly by weed interference. Although by increasing time interval of weeding time (up to 20 days biological yield decreased from 280.49 to 257.49, but this reduction was not significant. The interaction between planting density and weed interference on biological performance was not significant. Most biological yield was achieved in the absence of weeds. This is not unexpected because the availability of a large part of the resources cause more shoots in plant during

  15. Plant Distribution and Habitat, Other, Weed Points, Published in 2006, Duchesne County.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Plant Distribution and Habitat, Other dataset, was produced all or in part from Other information as of 2006. It is described as 'Weed Points'. Data by this...

  16. Allelopathy—A Tool to Improve the Weed Competitive Ability of Wheat with Herbicide-Resistant Black-Grass (Alopecurus myosuroides Huds.

    Directory of Open Access Journals (Sweden)

    Nils-Ove Bertholdsson

    2012-10-01

    Full Text Available Controlling black-grass in winter wheat production in northern Europe is an increasing problem because of more frequent winter crops and development of herbicide resistance in weeds. Alternative weed management strategies are needed, e.g., use of more competitive cultivars. Factors that increase cultivar competitiveness include early vigor and straw length, but also allelopathy. Therefore, the allelopathic properties of wheat cultivars included in the Swedish national list or in the release pipeline were investigated using a bioassay with herbicide-resistant and herbicide-sensitive black-grass as receiver plants. Wheat-rye translocation lines were also included in this screening to identify possible sources of high allelopathic activity. The bioassay results were followed up in two-year field trials. The results revealed large variations in allelopathic activity between cultivars. Most cultivars showed interference with both herbicide-sensitive and herbicide-resistant black-grass, although the allelopathic effect was lower on the herbicide-resistant biotype. Cultivars with high allelopathic activity gave only half the black-grass biomass of low allelopathic cultivars. Dinaro, a triticale (wheat-rye hybrid cultivar and the new wheat cultivar Nimbus showed the highest allelopathy and inhibition of black-grass growth. Only a few wheat lines with rye chromatin, all or part of a rye chromosome, showed high allelopathy. Use of cultivars with high allelopathic activity can thus be important in integrated weed management of black-grass.

  17. [Allelopathy of aqueous extract from Ligularia virgaurea, a dominant weed in psychro-grassland, on pasture plants].

    Science.gov (United States)

    Ma, Ruijun; Wang, Mingli; Zhao, Kun; Guo, Shoujun; Zhao, Qingfang; Sun, Kun

    2006-05-01

    Ligularia virgaurea is a noxious weed widely distributed in the alpine grassland of east Qinghai-Tibet Plateau of China. This paper studied the allelopathy of its aqueous extract on the pasture plants Festuca sinensis, Bromus magnus, Elymus nutans, Poa annua, and F. ovina in the region. The mean response index (RI) values of the pasture plants were calculated, and used to quantitatively assess the allelopathic sensitivity of the receptors at three levels, i. e., growth items, development stages, and species. Corresponding values of the weed were also treated in similar way to assess the allelopathic potential of the donor. The results showed that the allelopathic sensitivity was in the order of P. annua > B. magnus > F. sinensis > F. ovina > E. nutans. Both the seed germination and the seedling growth of test pasture plants were inhibited at species level, suggesting that rain eluviation was one of the means by which the weed released allelochemicals. The aqueous extracts from L. virgaurea root and leaf had a significant inhibitory effect at species level, and the effect of root extract was stronger than that of leaf extract, suggesting the competition among species on the underground resources in natural grassland. Allelopathy played an important role in L. virgaurea invasion, and might be responsible to the formation of mono-dominant community and the degeneration of grassland.

  18. Influence of Seeding Rate on Weed Density in Soybean Planting System for Southeastern Coastal Plains

    Directory of Open Access Journals (Sweden)

    Pawel Wiatrak

    2011-01-01

    Full Text Available Problem statement: Increasing seeding rates may help decrease weed pressure in soybean [Glycine max (L. Merr.] wide row spacing. Approach: The objective of this study was to evaluate the influence of five glyphosate-resistant soybean Maturity Groups (MG (IV, V, VI, VII and VIII and six seeding rates (68,000,136,000, 204,000, 272,000, 340,000 and 408,000 seeds ha-1 on weed density under dryland conditions on the Southeastern coastal plain in 2007-2009. Results: Weed decrease with increasing seeding rate varied over years. Weed density was generally lower at higher seeding rates for most MG soybeans at 30 and 60 DAP, except MG IV and VIII at 30 DAP in 2007 and MG VI at 30 DAP in 2008. At 60 DAP, soybean leaf area index (LAI and normalized difference vegetation index (NDVI were greater with lower weed density. Conclusion: Additionally, negative correlations were observed between weed density and plant LAI/NDVI for all MG in 2008 and MG IV through VI in 2009. These results suggest that increased seeding rates may help decrease weed pressure and improve soybean growth at early growth stages. However the response of weed pressure to seeding rate may vary over years and depend on MG soybean.

  19. Shared and host-specific microbiome diversity and functioning of grapevine and accompanying weed plants.

    Science.gov (United States)

    Samad, Abdul; Trognitz, Friederike; Compant, Stéphane; Antonielli, Livio; Sessitsch, Angela

    2017-04-01

    Weeds and crop plants select their microbiota from the same pool of soil microorganisms, however, the ecology of weed microbiomes is poorly understood. We analysed the microbiomes associated with roots and rhizospheres of grapevine and four weed species (Lamium amplexicaule L., Veronica arvensis L., Lepidium draba L. and Stellaria media L.) growing in proximity in the same vineyard using 16S rRNA gene sequencing. We also isolated and characterized 500 rhizobacteria and root endophytes from L. draba and grapevine. Microbiome data analysis revealed that all plants hosted significantly different microbiomes in the rhizosphere as well as in root compartment, however, differences were more pronounced in the root compartment. The shared microbiome of grapevine and the four weed species contained 145 OTUs (54.2%) in the rhizosphere, but only nine OTUs (13.2%) in the root compartment. Seven OTUs (12.3%) were shared in all plants and compartments. Approximately 56% of the major OTUs (>1%) showed more than 98% identity to bacteria isolated in this study. Moreover, weed-associated bacteria generally showed a higher species richness in the rhizosphere, whereas the root-associated bacteria were more diverse in the perennial plants grapevine and L. draba. Overall, weed isolates showed more plant growth-promoting characteristics compared with grapevine isolates. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  20. Crop-weed competition between sunflower (Helianthus annuus L.) and Convolvulus arvensis L. in substitutive experiments.

    Science.gov (United States)

    Kazinczi, G; Takács, A; Horváth, J

    2006-01-01

    The main characteristics of a substitutive experiment is that the proportions of two species in the mixtures are varied while the overall density of the two species is maintained constant - a replacement series. In our experiments early competition between sunflower and field bindweed (Convolvulus arvensis) was studied in a replacement studies under glasshouse conditions. Pot experiments were set up with the following treatments: 1, sunflower 100% (6 plants pot(-1)); 2, sunflower 66.6% (4 plants pot(-1)) + C. arvensis 33.3% (2 plants pot(-1)); 3, sunflower 33.3% (2 plants pot(-1)) + C. arvensis 66.6% (4 plants pot(-1)); 4, C. arvensis 100% (6 plants pot(-1)). Sixty eight days after sowing dry weight of shoots and roots were measured and nitrogen (N), phosphorus (P) and potassium (K) content was also determined. Dry biomass production of sunflower was almost twice higher as compared to that of C. arvensis without interspecific competition. Dry weight of sunflower and C. arvensis shoots and roots for a plant continuously decreased by reducing their proportion in the mixtures. Higher biomass production of sunflower suggests, that its development is faster at the beginning of vegetation penod, therefore sunflower has better competitive ability in sunflower--C. arvensis mixtures in the early competition as compared to C. arvensis. Shoot:root ratio of plants did not change considerably in mixtures, but generally was ten times higher in sunflower plants, as compared to that of C. arvensis. Shoots generally contained macro elements at higher concentration as compared to those of roots. Total NPK content of sunflower was reduced by 53 and 82% for a pot, as its proportion decreased in the mixtures. More severe reduction in NPK content was observed in case of C. arvensis, which also proves stronger competitive ability of sunflower in the early vegetation.

  1. Weeds in a Changing Climate: Vulnerabilities, Consequences, and Implications for Future Weed Management.

    Science.gov (United States)

    Ramesh, Kulasekaran; Matloob, Amar; Aslam, Farhena; Florentine, Singarayer K; Chauhan, Bhagirath S

    2017-01-01

    Whilst it is agreed that climate change will impact on the long-term interactions between crops and weeds, the results of this impact are far from clear. We suggest that a thorough understanding of weed dominance and weed interactions, depending on crop and weed ecosystems and crop sequences in the ecosystem, will be the key determining factor for successful weed management. Indeed, we claim that recent changes observed throughout the world within the weed spectrum in different cropping systems which were ostensibly related to climate change, warrant a deeper examination of weed vulnerabilities before a full understanding is reached. For example, the uncontrolled establishment of weeds in crops leads to a mixed population, in terms of C3 and C4 pathways, and this poses a considerable level of complexity for weed management. There is a need to include all possible combinations of crops and weeds while studying the impact of climate change on crop-weed competitive interactions, since, from a weed management perspective, C4 weeds would flourish in the increased temperature scenario and pose serious yield penalties. This is particularly alarming as a majority of the most competitive weeds are C4 plants. Although CO2 is considered as a main contributing factor for climate change, a few Australian studies have also predicted differing responses of weed species due to shifts in rainfall patterns. Reduced water availability, due to recurrent and unforeseen droughts, would alter the competitive balance between crops and some weed species, intensifying the crop-weed competition pressure. Although it is recognized that the weed pressure associated with climate change is a significant threat to crop production, either through increased temperatures, rainfall shift, and elevated CO2 levels, the current knowledge of this effect is very sparse. A few models that have attempted to predict these interactions are discussed in this paper, since these models could play an integral

  2. Weeds in a Changing Climate: Vulnerabilities, Consequences, and Implications for Future Weed Management

    Science.gov (United States)

    Ramesh, Kulasekaran; Matloob, Amar; Aslam, Farhena; Florentine, Singarayer K.; Chauhan, Bhagirath S.

    2017-01-01

    Whilst it is agreed that climate change will impact on the long-term interactions between crops and weeds, the results of this impact are far from clear. We suggest that a thorough understanding of weed dominance and weed interactions, depending on crop and weed ecosystems and crop sequences in the ecosystem, will be the key determining factor for successful weed management. Indeed, we claim that recent changes observed throughout the world within the weed spectrum in different cropping systems which were ostensibly related to climate change, warrant a deeper examination of weed vulnerabilities before a full understanding is reached. For example, the uncontrolled establishment of weeds in crops leads to a mixed population, in terms of C3 and C4 pathways, and this poses a considerable level of complexity for weed management. There is a need to include all possible combinations of crops and weeds while studying the impact of climate change on crop-weed competitive interactions, since, from a weed management perspective, C4 weeds would flourish in the increased temperature scenario and pose serious yield penalties. This is particularly alarming as a majority of the most competitive weeds are C4 plants. Although CO2 is considered as a main contributing factor for climate change, a few Australian studies have also predicted differing responses of weed species due to shifts in rainfall patterns. Reduced water availability, due to recurrent and unforeseen droughts, would alter the competitive balance between crops and some weed species, intensifying the crop-weed competition pressure. Although it is recognized that the weed pressure associated with climate change is a significant threat to crop production, either through increased temperatures, rainfall shift, and elevated CO2 levels, the current knowledge of this effect is very sparse. A few models that have attempted to predict these interactions are discussed in this paper, since these models could play an integral

  3. Natal Host Plants Can Alter Herbivore Competition

    OpenAIRE

    Pan, Huipeng; Evan L. Preisser; Su, Qi; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Zhang, Youjun

    2016-01-01

    Interspecific competition between herbivores is widely recognized as an important determinant of community structure. Although researchers have identified a number of factors capable of altering competitive interactions, few studies have addressed the influence of neighboring plant species. If adaptation to/ epigenetic effects of an herbivore’s natal host plant alter its performance on other host plants, then interspecific herbivore interactions may play out differently in heterogeneous and h...

  4. Flowers & Weeds.

    Science.gov (United States)

    Flannery, Maura C.

    1996-01-01

    Describes the topics and teaching strategies employed in an Issues in Biology course. Discusses flowers, plant breeding, potatoes and tomatoes, the chocolate tree, weeds, Arabidopis, gene transfers, and plant genes/human genes. Contains 22 references. (JRH)

  5. Flowers & Weeds.

    Science.gov (United States)

    Flannery, Maura C.

    1996-01-01

    Describes the topics and teaching strategies employed in an Issues in Biology course. Discusses flowers, plant breeding, potatoes and tomatoes, the chocolate tree, weeds, Arabidopis, gene transfers, and plant genes/human genes. Contains 22 references. (JRH)

  6. Using genetically modified tomato crop plants with purple leaves for absolute weed/crop classification.

    Science.gov (United States)

    Lati, Ran N; Filin, Sagi; Aly, Radi; Lande, Tal; Levin, Ilan; Eizenberg, Hanan

    2014-07-01

    Weed/crop classification is considered the main problem in developing precise weed-management methodologies, because both crops and weeds share similar hues. Great effort has been invested in the development of classification models, most based on expensive sensors and complicated algorithms. However, satisfactory results are not consistently obtained due to imaging conditions in the field. We report on an innovative approach that combines advances in genetic engineering and robust image-processing methods to detect weeds and distinguish them from crop plants by manipulating the crop's leaf color. We demonstrate this on genetically modified tomato (germplasm AN-113) which expresses a purple leaf color. An autonomous weed/crop classification is performed using an invariant-hue transformation that is applied to images acquired by a standard consumer camera (visible wavelength) and handles variations in illumination intensities. The integration of these methodologies is simple and effective, and classification results were accurate and stable under a wide range of imaging conditions. Using this approach, we simplify the most complicated stage in image-based weed/crop classification models. © 2013 Society of Chemical Industry.

  7. Introduction to Weeds and Herbicides.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University is an introduction to weed control and herbicide use. An initial discussion of the characteristics of weeds includes scientific naming, weed competition with crops, weed dispersal and dormancy, and conditions affecting weed seed germination. The main body of the…

  8. Introduction to Weeds and Herbicides.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University is an introduction to weed control and herbicide use. An initial discussion of the characteristics of weeds includes scientific naming, weed competition with crops, weed dispersal and dormancy, and conditions affecting weed seed germination. The main body of the…

  9. Effects of planting pattern and density on growth indices, yield and yield component of corn (Zea mays in competition with redroot pigweed (Amaranthus retrofelexus(

    Directory of Open Access Journals (Sweden)

    alireza barkhi

    2009-06-01

    Full Text Available An experiment was conducted in 2002-2003 using split-split plot arrangement based on Rondomised Compelete Block Design with three replications at Feiz Abad Agricultural Research Station of Qazvin, in order to study of planting patterns and corn densitis effect in competition with redroot pigweed. Main plots inclouded two planting pattern of corn (P1: single row and P2: double row, sub plots inclouded two corn densities (D1:7 and D2:10 plant/m2 and sub sub plots inclouded 4 weed densities (C1:0, C2:2, C3:6, C4:12 plant/m2. Sampling conducted in 2-weekly intervals and growth indices evaluated. Results indicated that with increasing of weed density CGR, TDW, LAI, number of seeds in row, grain and ear yield decreased but plant height increased. Also LAI, CGR, TDW, number of weed seed and seed,s weight of weed increased. By increasing in corn density LAI, CGR, TDW, ear and grain yield increased, but length and diameter of ear and number of seeds in row decreased. Also LAI and CGR of weed increased, but TDW was decreased. In double row planting pattern just CGR, LAI, TDW of corn were higher significantly than single row planting pattern. But single row planting of weed caused higher LAI, NAR, RGR, CGR and TDW of weed in comparison with double row planting pattern. In 2-way interaction, double row planting pattern and zero densities and 2 weeds/m2 had highest grain yield respectively. There were no significant differences for 3-way interactions but double row planting pattern 10 plant density of corn/m2 zero weed/ m2 had highest grain yield.

  10. Weed infestation in canopy of spring barley in condition of different tillage systems and fertilization and plant protection levels

    Directory of Open Access Journals (Sweden)

    Piotr Kraska

    2012-12-01

    Full Text Available The purpose of this work was to determine the influence of conventional tillage (fall ploughing at 25 cm and minimum tillage systems (chisel ploughing at 30 cm and two differentiated fertilization and plant protection levels on number, species composition and air dry weed mass in spring barley cv. Rataj. This spring barley was cultivated in crop rotation potato - spring barley - winter rye. The analysis of field infestation was made prior to spring barley harvest with quantitative- weighting method. There was estimated number of weeds, weed species composition and air dry weight of weeds in two randomly chosen areas of each plot of 0.5 m2. The density of weeds and weed air dry weight was statistically analysed by means of variance analysis, and the mean values were estimated with Tukey's confidence intervals (p=0.05. Intensive level of fertilization and chemical crop protection decreased number of monocotyledonous weeds and total weeds in canopy of spring barley. Conventional system of soil cultivation decreased in a canopy of spring barley the following species of weeds: Geranium pusillum, Galinsoga parviflora, Stellaria media, Apera spica-venti, Poa annua and Echinochloa crusgalli. Conventional tillage increases number of Chamomilla suaveolens and Fallopia convolvulus in a canopy of spring barley. Intensive fertilization and plant protection levels decreased weed infestation first of all through Echinochloa crusgalli, Apera spica-venti, Fallopia convolvulus, Galinsoga parviflora, Geranium pusillum, Chenopodium album and Setaria pumila.

  11. Fruiting phenology of some weed species in sowing of chosen cultivar plants

    Directory of Open Access Journals (Sweden)

    Marian Wesołowski

    2012-12-01

    Full Text Available In the paper, the percentage shares of the phases of fruiting and diaspore shedding of some weed species during fodder beet, spring wheat and faba bean harvest are presented. The results of the study were gathered in the years 2000-2003 on river alluvial soil made from light loam. The experimental scheme included mechanical and chemical control of the cultivated plants. On weed-free objects treated with herbicides, the following herbicides were used: fodder beet - Buracyl 80 WP (lenacyl 80% in dose 1 kg.ha-1; spring wheat - Chwastox Turbo 340 SL (MCPA + dicamba in dose 2l.ha-1; faba-bean - Afalon (linuron 50% in dose 1,5 kg.ha-1. Phenological observations were carried out at 10-day intervals beginning from the day of sowing the cultivated plant. It was proven that weeds had the most favourable conditions of fruiting and seed shedding in fodder beet and faba bean. Fruiting and shedding of most weed species were limited by herbicides, as well as cold years. The following weed species: fodder beet without herbicides - Lamium amplexicaule, Chenopodium polyspermum, Anagallis arvensis i Echinochloa crus-galli; fodder beet with herbicides - Convolvulus arvensis, Lamium purpureum i Echinochloa crus-galli; spring wheat without herbicides - Capsella bursa-pastoris i Fallopia convolvulus; spring wheat with herbicides - Avena fatua; faba been without herbicides - Galium aparine, Anagallis arvensis i Convolvulus arvensis; faba been with herbicides - Galium aparine, shed diaspores in the greatest degree.

  12. Nutrient absorbtion of weeds in maize.

    Science.gov (United States)

    Lehoczky, E; Kismányoky, A; Nagy, P; Németh, T

    2008-01-01

    Our study was carried out in Hungary at Keszthely, in 2007. The effect of different cultivation methods: no-till drill, disk tillage, conventional tillage (ploughing) and five increasing N doses were studied on the weediness. The bi-factorial trial was arranged in split plot design with four replications. Crop rotation: winter wheat-winter wheat-maize-maize. The seeding of maize was 23rd of April in 2007. The weed survey was made with Balázs-Ujvárosi coenological method on the 17th of May. In the experiment were found 21 weed species. We collected all plants of every weed species by plots. The sample area was 1 m2. Furthermore five maize plants per plot were sampled on the 22nd of May. Maize was at 3-4 leaves stage. For reason of competition studies no herbicides were applied on sampling sites. The aerial parts of weeds and maize plants were collected, and the fresh and dry matter weight was measured. We analyzed in detail, the occurrence of weed species, and the biomass production of weeds in comparison with maize. The effect of different cultivation methods markedly demonstrated the weed cover, the number of perennial and annual weeds and the number of occurring weed species.

  13. Weeding with transgenes.

    Science.gov (United States)

    Duke, Stephen O

    2003-05-01

    Transgenes promise to reduce insecticide and fungicide use but relatively little has been done to significantly reduce herbicide use through genetic engineering. Recently, three strategies for transgene utilization have been developed that have the potential to change this. These are the improvement of weed-specific biocontrol agents, enhancement of crop competition or allelopathic traits, and production of cover crops that will self-destruct near the time of planting. Failsafe risk mitigation technologies are needed for most of these strategies.

  14. Evaluating subsoiling and herbaceous weed control on shortleaf pine planted in retired farm land

    Science.gov (United States)

    John D. Kushla

    2010-01-01

    In March 2005, shortleaf pine was planted on retired fields of the Mississippi Agriculture and Forestry Experiment Station in Holly Springs. The objectives were to evaluate subsoiling and herbaceous weed control on first year seedling stocking, survival, and size. First year seedling measurements were made on stocking, survival, and size. Only results for first year...

  15. Ten-Year Growth of Five Planted Hardwood Species Mechanical Weed Control on Sharkey Clay Soil

    Science.gov (United States)

    Roger M. Krinard; Harvey E. Kennedy

    1983-01-01

    Five hardwood species planted on Sharkey clay soil showed little practical difference in growth whether plots were mowed or diskedfor weed control in years 6 to 10, although disking had given better growth in the first 5 years. After 10 years, cottonwood (Populus deltoides Bartr. ex Marsh.) stem volume was at least three times greater than other species. Changes in...

  16. Forage radish winter cover crop suppresses winter annual weeds in fall and before corn planting

    Science.gov (United States)

    Forage radish (Raphanus sativus L. var. longipinnatus) is a new winter cover crop in the Mid-Atlantic region. The objective of this project was to characterize the repeatability, amount, and duration of weed suppression during and after a fall-planted forage radish cover crop and to quantify the sub...

  17. Natal Host Plants Can Alter Herbivore Competition

    Science.gov (United States)

    Pan, Huipeng; Preisser, Evan L.; Su, Qi; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun

    2016-01-01

    Interspecific competition between herbivores is widely recognized as an important determinant of community structure. Although researchers have identified a number of factors capable of altering competitive interactions, few studies have addressed the influence of neighboring plant species. If adaptation to/ epigenetic effects of an herbivore’s natal host plant alter its performance on other host plants, then interspecific herbivore interactions may play out differently in heterogeneous and homogenous plant communities. We tested wether the natal host plant of a whitefly population affected interactions between the Middle-east Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species of the whitefly Bemisia tabaci by rearing the offspring of a cabbage-derived MEAM1 population and a poinsettia-derived MED population together on three different host plants: cotton, poinsettia, and cabbage. We found that MED dominated on poinsettia and that MEAM1 dominated on cabbage, results consistent with previous research. MED also dominated when reared with MEAM1 on cotton, however, a result at odds with multiple otherwise-similar studies that reared both species on the same natal plant. Our work provides evidence that natal plants affect competitive interactions on another plant species, and highlights the potential importance of neighboring plant species on herbivore community composition in agricultral systems. PMID:28030636

  18. Natal Host Plants Can Alter Herbivore Competition.

    Science.gov (United States)

    Pan, Huipeng; Preisser, Evan L; Su, Qi; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Zhang, Youjun

    2016-01-01

    Interspecific competition between herbivores is widely recognized as an important determinant of community structure. Although researchers have identified a number of factors capable of altering competitive interactions, few studies have addressed the influence of neighboring plant species. If adaptation to/ epigenetic effects of an herbivore's natal host plant alter its performance on other host plants, then interspecific herbivore interactions may play out differently in heterogeneous and homogenous plant communities. We tested wether the natal host plant of a whitefly population affected interactions between the Middle-east Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species of the whitefly Bemisia tabaci by rearing the offspring of a cabbage-derived MEAM1 population and a poinsettia-derived MED population together on three different host plants: cotton, poinsettia, and cabbage. We found that MED dominated on poinsettia and that MEAM1 dominated on cabbage, results consistent with previous research. MED also dominated when reared with MEAM1 on cotton, however, a result at odds with multiple otherwise-similar studies that reared both species on the same natal plant. Our work provides evidence that natal plants affect competitive interactions on another plant species, and highlights the potential importance of neighboring plant species on herbivore community composition in agricultral systems.

  19. Weed Interference Effects on Leaves, Internode and Harvest Index of Dry Bean (Phaseolus vulgaris L.

    Directory of Open Access Journals (Sweden)

    Hossein GHAMARI

    2015-03-01

    Full Text Available The development of appropriate weed management strategies and efficient use of herbicides relies upon understanding weed-crop interactions. A field study was carried out to assess the effect of weed interference on leaves, internode and harvest index of dry bean (Phaseolus vulgaris L.. The experiment was established under a randomized complete block design with two types of weed interference treatments: plots with weeds and plots without weeds at different time intervals (0, 10, 20, 30, 40 and 50 days after crop emergence. The sigmoid Boltzmann model was used to quantify the crop traits as influenced by weed interference. Prolonged delays in weed removal reduced gradually the number of leaves of the crop. Weed interference decreased dry weight of leaves as well, so that the lowest value of it (33.49 g plant-1 was observed in full season during weed-infested treatment. Infestation of weeds affected the length of the crop internodes. While the weed interference duration increased, the length of the internodes decreased. Harvest index was also sensitive to weed competition. As the crop was kept weed-infested from the emergence for increasing periods of time, harvest index decreased to a value of 28.01%. A significant negative correlation between total biomass of weeds and dry bean traits (number of leaves, leaves dry weight, internode length and harvest index was observed. Therefore, weeds are able to adversely affect dry bean growth through constraining environmental resources and impairing leaves as the photosynthetic areas.

  20. Competition-density effect in plant populations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The competition-density effect of plant populations is of significance in theory and practice of forest management and has been studied for long time. The differences between the two reciprocal equations of the competition-density effect in nonself-thinning populations and self-thinning populations were analyzed theoretically. This supplies a theoretical basis for analyzing the dynamics of forest populations and evaluating the effect of forest management.

  1. Effect of sunn hemp (Crotalaria juncea L.) cutting date and planting density on weed suppression in Georgia, USA.

    Science.gov (United States)

    Morris, J Bradley; Chase, Carlene; Treadwell, Danielle; Koenig, Rosie; Cho, Alyssa; Morales-Payan, Jose Pable; Murphy, Tim; Antonious, George F

    2015-01-01

    A field study was conducted in 2008 and 2009 at the USDA, ARS, Plant Genetic Resources Conservation Unit in Griffin, GA, to investigate weed suppression by sunn hemp (Crotalaria juncea L). The objectives were to (1) evaluate the effects of apical meristem removal (AMR) at three dates [5, 6, and 7 wks after planting (WAP) on May 14, 2008 and May 21, 2009] and (2) assess the impact of seeding rates (11, 28, and 45 kg ha(-1)) on weed biomass reduction. Weed species were identified at 4, 8, and 12 wks after sunn hemp planting. Sunn hemp cutting date had no significant effect on weed suppression in 2008 but significant differences for grass weeds at 4, 8, and 12 WAP and for yellow nutsedge at 8 and 12 WAP did occur when compared to the control in 2009. In comparison to the sunn hemp-free control plot in 2009, all three seeding rates had reduced grass weed dry weights at 4, 8, and 12 WAP. The total mass of yellow nutsedge when grown with sunn hemp was reduced compared to the total mass of yellow nutsedge grown in the weedy check for all seeding rates at 8 and 12 WAP. Lower grass weed biomass was observed by 12 WAP for cutting dates and seeding rates during 2008 and 2009. Sunn hemp cutting date and seeding rate reduced branch numbers in both years. The reduction in sunn hemp seeding rates revealed a decrease in weed populations.

  2. Variabilidade da infestação em duas variedades de trigo mole (Triticum Aestivum L.. II: em função de características relativas à capacidade competitiva do trigo Variability of weed infestation in two wheat varieties (Triticum Aestivum L.. II: as influenced by their weed competition characteristics

    Directory of Open Access Journals (Sweden)

    José Manuel Godinho Calado

    2008-01-01

    Full Text Available Culturas e/ou variedades competitivas com as plantas infestantes são auxiliares relevantes para a gestão da infestação. Assim, neste trabalho, procurou-se verificar a relação da taxa de afilhamento e da altura das plantas do trigo mole com a infestação. As observações e verificações foram realizadas durante quatro anos (1996/97 a 1999/00, a partir de um ensaio de datas de sementeira e de controlo das infestantes em duas variedades de trigo mole (Sever e Centauro instalado na Herdade da Revelheira, concelho de Reguengos de Monsaraz. De acordo com a análise dos resultados, constatou-se que, perante níveis elevados de infestação, a taxa de afilhamento e a altura das plantas de trigo variaram inversamente com o número de plantas infestantes da classe Monocotiledónea e directamente com a produção de grão e de biomassa da cultura. Por isso, conclui-se que as características referidas (afilhamento e altura das plantas se relacionam positivamente com a capacidade das plantas de trigo competirem com a flora infestante.Weed competitiveness of crops and/or varieties can be an important tool for weed management. In this study, the effect of plant height and tillering capacity of two wheat varieties was analyzed regarding their contribution to weed competitiveness. The observations were carried out over four years (1996/97 to 1999/00 in a field trial on seeding dates and weed control in two wheat varieties (Sever and Centauro on the “Herdade da Revilheira”, municipality of Reguengos de Monsaraz. The results show that the two parameters plant height and tillering rate are positively related to crop yield and that there is a negative correlation with the number of weeds, especially grass weeds. Thus it can be concluded that the characteristics of plant height and tillering rate are positively related to the capacity of the wheat crop to compete with weed infestation.

  3. Activity of Stress-related Antioxidative Enzymes in the Invasive Plant Crofton Weed(Eupatorium adenophorum)

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Crofton weed is an Invasive weed in southwestern China.The activities of several antioxidative enzymes involved in plant protection against oxidative stress were assayed to determine physiological aspects of the crofton weed that might render the plant vulnerable to environmental stress.Stresses imposed on crofton weed were heat (progressively increasing temperatures:25℃,30℃,35℃.38℃ and 42℃ at 24 h intervals),cold(progressively decreasing temperatures:25℃,20℃,15℃,10℃ and 5℃ at 24h intervals),and drought(without watering up to 4 days).The three stresses induced oxidative damage as evidenced by an increase in lipid peroxidation.The effect varied with the stress imposed and the length of exposure.The activity of superoxide dismutase(SOD)increased in response to all stresses but was not significantly different from the controls(P<0.05) when exposed to cold stress.Catalase (CAT)activity decreased in response to heat and drought stress but increased when exposed to cold conditions.Guaiacol peroxidase(POD) and glutathione reductase (GR)activities increased in response to cold and drought but decreased in response to heat stress.The activity of ascorbate peroxidase(APX) responded differently to all three stresses.Monodehydroascorbate reductase (MDHAR)activity decreased in response to heat and drought,and slightly increased in response to the cold stress but was not significantly different from the controls (P<0.05).The activity of dehydroascorbate reductase(DHAR)increased in response to all three stresses.Taken together,the co-ordinate increase of the oxygen-detoxifying enzymes might be more effective to protect crofton weed from the accumulation of oxygen radicals at low temperatures rather than at high temperatures.

  4. Response of Exotic Invasive Weed Alternanthera philoxeroides to Environmental Factors and Its Competition with Rice

    Institute of Scientific and Technical Information of China (English)

    YU Liu-qing; Yoshiharu FUJII; ZHOU Yong-jun; ZHANG Jian-ping; LU Yong-liang; XUAN Song-nan

    2007-01-01

    A greenhouse experiment was conducted to determine the influence of the environmental factors such as Iow-temperature, drought stress, salt-alkali and flooding on the survival rate, propagation rate, fresh biomass and viability of the Alternanthera philoxeroides and its competitive ability against rice by using bioassay method. A high viability of 84% was found when the stems were treated at 4 ℃ and then grew under normal conditions, while no viable plant was noted when the stems were treated at -20 ℃ and grew under normal conditions. Compared to the fresh stem with water content of 93.5%, the survival rate, number of propagated stems and fresh biomass of A. philoxeroides derived from the stems with water content of 30.2% were reduced by 45%,33% and 74% respectively. The treatments of 0.1% salt-alkaline solution led to loss of viability of A. philoxeroides. The stems of A.philoxeroides could grow in wet soil with different depths of water-layer. The A. philoxeroides at density of 23-180 plants/m2 reduced the rice grain yield by 43-50% at the rice plant density of 100 plants/m2.

  5. Viability of various weed seeds in anaerobic conditions (biogas plant)

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, S.; Hansen, J.

    1983-04-01

    Seeds from different weeds, Urtica urens L. (nettle), Solanum nigrum L. (nightshade), Avena fatua L. (wild oat-grass), Brassica napus L. (rape), Chenopodium album L. (goose-foot), were put into small polyester net bags, which were placed in biogas reactors containing cattle manure. These ''biogas reactors'' were placed at different temperatures . Net bags were taken out after 4.5, 10.5, 21.5, 38 and 53 days, and the seeds were tested for their viability by germination tests and the tetrazolium method. Concerning all seeds it was manifested that the viability decreased very steeply at 35degC. Most of the seeds had a T/sub 50/ at 2-5 days; Chenopodium album L seeds had a T/sub 50/ at 16 days. After 4.5 days it was not possible to find living Avena fatua L seeds. The decrease in viability was less steep at 20degC and even less steep at 2degC.

  6. Plant population and weeds influence stalk insects, soil moisture, and yield in rainfed sunflowers

    Institute of Scientific and Technical Information of China (English)

    JAWWAD A. QURESHI; PHILLIP W. STAHLMAN; J. P. MICHAUD

    2007-01-01

    Insect infestation, soil moisture, and yield were examined in populations of≈ 33 140 plants/ha (low) and ≈ 40 340 plants/ha (high) of an oilseed sunflower, Helianthus annuus L, cv. ' Triumph 660CL' with two levels of weediness. Less weedy plots resulted from the application of herbicide combination of S-metolachlor and sulfentrazone, whereas more weedy plots resulted from application of sulfentrazone alone. Among the 12 weed species recorded, neither plant numbers nor biomass differed between crop plant densities.Larvae of the stalk-boring insects Cylindrocopturus adspersus (Coleoptera: Curculionidae) and Mordellistena sp. (Coleoptera: Mordellidae) were less abundant in high density sunflowers, ostensibly due to reduced plant size. However, the same effect was not observed for Dectes texanus (Coleoptera: Cerambycidae) or Pelochrista womanana (Lepidoptera:Tortricidae), two other stalk-boring insects. Soil moisture was highest in low density and lowest in the high density sunflowers that were less weedy. Stalk circumference, head diameter, and seed weight were reduced for sunflower plants with short interplant distances (mean = 20 cm apart) compared to plants with long interplant distances (mean = 46 cm apart).These three variables were greater in less weedy plots compared with more weedy plots and positively correlated with interplant distance. Yields on a per-hectare basis paralleled those on a per-plant basis but were not different among treatments. The agronomic implications of planting density are discussed in the context of weed and insect management.

  7. Weed Control and Corn (Zea mays Response to Planting Pattern and Herbicide Program with High Seeding Rates in North Carolina

    Directory of Open Access Journals (Sweden)

    Mitchell K. Williams

    2014-01-01

    Full Text Available Effective weed control in corn (Zea mays L. is important to optimize yield. Concern over environmental impact of atrazine and selection for glyphosate resistance has increased the need to develop alternative strategies that use herbicides other than atrazine and glyphosate and appropriate cultural practices to control weeds. Research was conducted during 2011 and 2012 to determine weed and corn response to herbicide programs containing dicamba, glufosinate, and glyphosate applied postemergence alone or with atrazine in single- and twin-row planting patterns. Planting pattern had no effect on common ragweed (Ambrosia artemisiifolia L. and Texas panicum (Panicum texanum L. population and did not interact with herbicide program. Effective weed control hastened maturity in some but not all instances. Under weed-free conditions, corn grain yield was higher in 5 of 7 trials when planted in twin rows versus single rows at equivalent corn populations (141,000 plants ha−1. These results suggest that while planting pattern may not impact weed control dramatically, planting corn in twin rows may be an effective alternative to single-row planting patterns because of increased yield under high corn populations.

  8. Elucidating the apparent maize tolerance to weed competition in long-term organically managed systems

    NARCIS (Netherlands)

    Ryan, M.R.; Mortensen, D.A.; Bastiaans, L.; Teasdale, J.R.; Mirsky, S.B.; Curran, W.S.; Seidel, R.

    2010-01-01

    In a long-term cropping systems trial comparing organically and conventionally managed systems, organic maize production sustained crop yields equal to conventional methods despite higher weed levels. In 2005 and 2006, an experiment nested within the trial was conducted to gain insight into this

  9. Annual warm-season grasses vary for forage yield, quality, and competitiveness with weeds

    Science.gov (United States)

    Warm-season annual grasses may be suitable as herbicide-free forage crops. A two-year field study was conducted to determine whether tillage system and nitrogen (N) fertilizer application method influenced crop and weed biomass, water use, water use efficiency (WUE), and forage quality of three war...

  10. [Biological activity of fungi from the phyllosphere of weeds and wild herbaceous plants].

    Science.gov (United States)

    Berestitskiĭ, A O; Gasich, E L; Poluéktova, E V; Nikolaeva, E V; Sokornova, S V; Khlopunova, L B

    2014-01-01

    Antimicrobial, phytotoxic, and insecticidal activity of 30 fungal isolates obtained from leaves of weeds and wild herbaceous plants was assessed. Antibacterial, antifungal, phytotoxic, and insecticidal activity was found in over 50, 40, 47, and 40% of the isolates, respectively. These findings may be important for toxicological assessment of potential mycoherbicides, as well as provide a basis for investigation of the patterns of development of phyllosphere communities affected by fungal metabolites.

  11. Marijuana (Weed, Pot) Facts

    Science.gov (United States)

    ... That People Abuse » Marijuana (Weed, Pot) Facts Marijuana (Weed, Pot) Facts Listen Marijuana is a green, brown, or gray mix of dried, shredded leaves and flowers from the marijuana plant. Marijuana can be rolled up and smoked ...

  12. Mixed Weeds and Competition with Directly Seeded Cotton, North Henan Province,China%豫北露地直播棉田杂草的发生及其与棉花的竞争作用

    Institute of Scientific and Technical Information of China (English)

    马小艳; 马艳; 奚建平; 姜伟丽; 马亚杰; 李希风

    2012-01-01

    为了明确棉田自然混生杂草对棉花的危害程度及其关键防除时期,通过田间杂草共生期试验,研究了豫北露地直播棉田杂草的发生及其与棉花的竞争临界期.结果表明,豫北地区露地直播棉田的优势杂草为牛筋草、马齿苋、藜和鳢肠,杂草出土高峰期集中在棉花苗期和花蕾期,且存在3个出土高峰,分别在5月中旬、6月上中旬和7月中下旬.当杂草与棉花竞争持续时间少于4周时,由于杂草与棉花植株均较小,且土壤中养分相对充足,因此杂草对棉花生长和产量的影响不大;当杂草与棉花竞争期达8周以上时,杂草对棉花的竞争作用明显增强,棉花的株数减少,茎秆变细,形成瘦高植株,且单株结铃数、铃重等产量指标明显降低.因此,豫北棉田自然混生杂草群落与棉花的竞争临界期为棉花出苗后4~8周,在此期间应采取相应措施,保证田间无草害.%In order to understand the degree of damage caused by mixed weeds, and the critical control period, a field experiment was conducted to investigate weed occurrence and the critical period of competition in a directly seeded cotton field in North Henan Province. Eleusine indica (L.) Gaerth, Portulaca oleracea L., Chenopodium aldum L., and Eclipta prostrata L. Were dominant weed species in the cotton field over the whole growing season. Weeds germinated mainly between the seedling stage and the budding stage of the cotton, with three peaks in weed seedling emergence in mid-May, early to mid-June, and mid to late July. Duration of weed competition less than four weeks did not significantly affect cotton growth and yield because soil nutrients were sufficient for both weed and cotton seedlings. However, the number of cotton plants, stem diameter, and yield component factors including boll number per plant and boll weight, were reduced when weed competition lasted up to 8 weeks. Therefore, the critical period for weed control in cotton

  13. Mycorrhizal fungal identity and diversity relaxes plant-plant competition.

    Science.gov (United States)

    Wagg, Cameron; Jansa, Jan; Stadler, Marina; Schmid, Bernhard; van der Heijden, Marcel G A

    2011-06-01

    There is a great interest in ecology in understanding the role of soil microbial diversity for plant productivity and coexistence. Recent research has shown increases in species richness of mutualistic soil fungi, the arbuscular mycorrhizal fungi (AMF), to be related to increases in aboveground productivity of plant communities. However, the impact of AMF richness on plant-plant interactions has not been determined. Moreover, it is unknown whether species-rich AMF communities can act as insurance to maintain productivity in a fluctuating environment (e.g., upon changing soil conditions). We tested the impact of four different AMF taxa and of AMF diversity (no AMF, single AMF taxa, and all four together) on competitive interactions between the legume Trifolium pratense and the grass Lolium multiflorum grown under two different soil conditions of low and high sand content. We hypothesized that more diverse mutualistic interactions (e.g., when four AMF taxa are present) can ease competitive effects between plants, increase plant growth, and maintain plant productivity across different soil environments. We used quantitative PCR to verify that AMF taxa inoculated at the beginning of the experiment were still present at the end. The presence of AMF reduced the competitive inequality between the two plant species by reducing the growth suppression of the legume by the grass. High AMF richness enhanced the combined biomass production of the two plant species and the yield of the legume, particularly in the more productive soil with low sand content. In the less productive (high sand content) soil, the single most effective AMF had an equally beneficial effect on plant productivity as the mixture of four AMF. Since contributions of single AMF to plant productivity varied between both soils, higher AMF richness would be required to maintain plant productivity in heterogeneous environments. Overall this work shows that AMF diversity promotes plant productivity and that AMF

  14. Capacidade competitiva do jatobá com adubos verdes, forrageiras e plantas daninhas Competitive capacity of Hymenaea courbaril with green manure, forage species and weeds

    Directory of Open Access Journals (Sweden)

    A.M.M Gandini

    2011-01-01

    Full Text Available O estudo do consórcio entre espécies anuais e perenes representa uma ferramenta importante no processo de implantação e manejo florestal. O objetivo deste trabalho foi avaliar a capacidade competitiva do jatobá (Hymenaea courbaril com espécies de adubos verdes, forrageiras e plantas daninhas quanto à alocação de matéria seca, área foliar e concentração de nutrientes. Foram conduzidos dois experimentos, sendo os tratamentos compostos pela combinação de mudas de jatobá, desenvolvendo-se isoladamente ou em competição com cada uma das seguintes espécies: Brachiaria humidicola, Brachiaria brizantha, Brachiaria decumbens, Panicum maximum, Cajanus cajan, Canavalia ensiformis e Mucuna aterrima (experimento 1 e Bidens pilosa, Cenchrus echinatus, Euphorbia heterophylla, Lolium multiflorum e Solanum americanum (experimento 2, mais o cultivo de cada planta daninha e consorte isolada. Após convivência por 60 dias, as plantas foram coletadas para avaliação de matéria seca, área foliar e teor de nutrientes. Observou-se que a competição entre as plantas não promoveu alterações na produção de matéria seca ou área foliar do jatobá. Tendo em vista o exposto, verifica-se que a capacidade competitiva do jatobá não é afetada pela presença das espécies de adubos verdes e forrageiras, possibilitando convivência em fase inicial de desenvolvimento. Quanto à convivência das plantas daninhas com o jatobá, observou-se efeito positivo no acúmulo de nutrientes por estas.The study of intercropping between annual and perennial plants is an important tool in the process of forest implantation and management. The objective of this study was to assess the competitive capacity of jatoba (Hymeneae courbaril against green manure, forage and weed species, regarding the allocation of dry matter, leaf area and nutritional content. Two experiments were installed and the treatments consisted of combinations of jatoba seedlings per plot, alone

  15. TAXONOMY OF FUSARIUM SPECIES ISOLATED FROM CULTIVATED PLANTS, WEEDS AND THEIR PATHOGENICITY FOR WHEAT

    Directory of Open Access Journals (Sweden)

    Jasenka Ćosić

    2002-06-01

    Full Text Available Fusarium species are wide-spread and known to be pathogenic agents to cultivated plants in various agroclimatic areas. During a four year investigation 10 Fusarium species and Microdochium nivale were isolated from wheat, barley, maize and soybean as well as from 10 weeds collected from 10 locations in Slavonia and Baranya. Fusarium graminearum was dominant on wheat and barley, F. moniliforme on maize and F. oxysporum on soybean. Regarding weeds, the presence of the following Fusarium species was established: F. graminearum on Amaranthus hybridus, Capsella bursa-pastoris, Lamium purpureum, Sorghum halepense and Urtica dioica, F. moniliforme on Abutilon theophrasti, F. subglutinans on Polygonum aviculare, F. avenaceum on Capsella bursa-pastoris, Rumex crispus and Matricaria sp., F. culmorum on Abutilon theophrasti, F. sporotrichioides on Polygonum aviculare, F. proliferatum and F. poae on Artemisia vulgaris. Pathogenicity test to wheat seedlings was done in our laboratory on winter wheat cultivars Slavonija and Demetra (totally 146 isolates. The most pathogenic species to wheat seedilings were F. graminearum, F. culmorum and F. sporotrichioides and the least pathogenic F. moniliforme, F. solani, F. oxysporum and F. poae. Pathogenicity test for wheat ears was done on genotypes Osk.8c9/3-94 and Osk.6.11/2 (totally 25 isolates. The results obtained by our investigation showed that there were no significant differences in pathogenicity of Fusarium species isolated from both cultivated plants and weeds. Weeds represent a constant source of inoculum of F. species for cultivated plants and they serve as epidemiologic bridges among vegetations.

  16. Intercropping frost-sensitive legume crops with winter oilseed rape reduces weed competition, insect damage, and improves nitrogen use efficiency

    Directory of Open Access Journals (Sweden)

    Cadoux Stéphane

    2015-05-01

    Full Text Available Mixing plant species in agroecosystems is highlighted as an agroecological solution to reduce pesticides and fertilizers while maintaining profitability. In the French context, intercropping frost-sensitive legume crops with winter oilseed rape is potentially interesting and began to be implemented by farmers. In this study we aimed at measuring the services and disservices of this intercrop with three different legume mixtures, in terms of growth and yield for rapeseed, ground cover of weeds in autumn and damage caused by rape winter stem weevil. The experiment was carried out at four sites from 2011 to 2014. We showed higher total aerial dry weights and total aerial nitrogen contents in the intercrops compared to sole winter oilseed rape in November. The companion plants contributed to the control of weeds and the mitigation of rape winter stem weevil damage, notably through the increase in the total aerial weight. In spring, after destruction of the companion plants, the intercrops had partially compensated a reduction in the N fertilization rate (–30 kg per hectare in terms of aerial nitrogen content in rapeseed, with no consequences on the yield which was maintained or even increased. There were probably other interactions such as an improvement in rapeseed root exploration. The consequences were an increase in the nitrogen use efficiency in intercrops. The intercrop with faba bean and lentil showed the best results in terms of autumn growth, weed control, reduction in rape winter stem weevil damage, and rapeseed N content in spring and yield. Intercropping frost-sensitive legume crops with winter oilseed rape is thus a promising way to reconcile yield and reduction in pesticides and fertilizer use and perhaps to benefit more widely to the cropping system.

  17. Exotic weeds and fluctuating microclimate can constrain native plant regeneration in urban forest restoration.

    Science.gov (United States)

    Wallace, K J; Laughlin, Daniel C; Clarkson, Bruce D

    2017-02-09

    Restoring forest structure and composition is an important component of urban land management, but we lack clear understanding of the mechanisms driving restoration success. Here we studied two indicators of restoration success in temperate rainforests: native tree regeneration and epiphyte colonization. We hypothesized that ecosystem properties such as forest canopy openness, abundance of exotic herbaceous weeds, and the microclimate directly affect the density and diversity of native tree seedlings and epiphytes. Relationships between environmental conditions and the plant community were investigated in 27 restored urban forests spanning 3 to 70 years in age and in unrestored and remnant urban forests. We used structural equation modelling to determine the direct and indirect drivers of native tree regeneration and epiphyte colonization in the restored forests. Compared to remnant forest, unrestored forest had fewer native canopy tree species, significantly more light reaching the forest floor annually, and higher exotic weed cover. Additionally, epiphyte density was lower and native tree regeneration density was marginally lower in the unrestored forests. In restored forests, light availability was reduced to levels found in remnant forests within 20 years of restoration planting, followed shortly thereafter by declines in herbaceous exotic weeds and reduced fluctuation of relative humidity and soil temperatures. Contrary to expectations, canopy openness was only an indirect driver of tree regeneration and epiphyte colonization, but it directly regulated weed cover and microclimatic fluctuations, both of which directly drove the density and richness of regeneration and epiphyte colonization. Epiphyte density and diversity were also positively related to forest basal area, as large trees provide physical habitat for colonization. These results imply that ecosystem properties change predictably after initial restoration plantings, and that reaching critical

  18. ALLELOPATHIC EFFECTS OF WEED (Tridax procumbens L.) EXTRACT ON SEED GERMINATION AND SEEDLING GROWTH OF SOME LEGUMINOUS PLANTS

    OpenAIRE

    D Femina; P. Lakshmipriya; Subha, S; R. Manonmani

    2012-01-01

    Aqueous leaves extract of different concentrations of weed (Tridax procumbens L.) was used to investigate their allelopathic effects on seed germination, root and shoot length and fresh and dry weight of some leguminous plants viz. Vigna radiata L. (Green gram), Dolichos biflorus L. (Horse gram) and Vigna unguiculata L. (Cow pea). Mature fresh leaves of weed were crushed and soaked for 24h; the filtrates were diluted to make different concentrations and used to investigate their effect on the...

  19. Application of generalized Hough transform for detecting sugar beet plant from weed using machine vision method

    Directory of Open Access Journals (Sweden)

    A Bakhshipour Ziaratgahi

    2017-05-01

    Full Text Available Introduction Sugar beet (Beta vulgaris L. as the second most important world’s sugar source after sugarcane is one of the major industrial crops. The presence of weeds in sugar beet fields, especially at early growth stages, results in a substantial decrease in the crop yield. It is very important to efficiently eliminate weeds at early growing stages. The first step of precision weed control is accurate detection of weeds location in the field. This operation can be performed by machine vision techniques. Hough transform is one of the shape feature extraction methods for object tracking in image processing which is basically used to identify lines or other geometrical shapes in an image. Generalized Hough transform (GHT is a modified version of the Hough transform used not only for geometrical forms, but also for detecting any arbitrary shape. This method is based on a pattern matching principle that uses a set of vectors of feature points (usually object edge points to a reference point to construct a pattern. By comparing this pattern with a set pattern, the desired shape is detected. The aim of this study was to identify the sugar beet plant from some common weeds in a field using the GHT. Materials and Methods Images required for this study were taken at the four-leaf stage of sugar beet as the beginning of the critical period of weed control. A shelter was used to avoid direct sunlight and prevent leaf shadows on each other. The obtained images were then introduced to the Image Processing Toolbox of MATLAB programming software for further processing. Green and Red color components were extracted from primary RGB images. In the first step, binary images were obtained by applying the optimal threshold on the G-R images. A comprehensive study of several sugar beet images revealed that there is a unique feature in sugar beet leaves which makes them differentiable from the weeds. The feature observed in all sugar beet plants at the four

  20. Phytotoxic effects of Calotropis procera (Ait. R. Br. extract on three weed plants

    Directory of Open Access Journals (Sweden)

    Gulzar, A.

    2014-11-01

    Full Text Available A study was conducted to determine the potential and nature of allelopathic interference of Calotropis procera on seed germination and seedling growth of three weed species (Ageratum conyzoides L., Cannabis sativa L. and Trifolium repens L. Aqueous extracts of Calotropis procera at 0.5, 1.0, 2.0 and 4.0% concentrations were applied to determine their effect on seed germination and seedling growth of test plants under laboratory conditions. The aqueous extracts had retardary effect on seed germination, root length and shoot length. Germination percentage, root length and shoot length of weed species decreased progressively when treated with increasing extract concentration (0.5, 1, 2 and 4%. The pH values did not increase at all extract concentrations. Therefore, the change in pH values in this experiment is not responsible for the inhibition of test species growth.The phenolic content analysed show more pronounced increase in its contents at 4% concentrations. The study concludes that C. procera releases phenolics into the extract and these are probably involved in the growth inhibitory effect, which causes allelopathy operative in the community dominated by C. procera and provide an advantage to the weed.

  1. Weed control by direct injection of plant protection products according to specific situations

    Directory of Open Access Journals (Sweden)

    Krebs, Mathias

    2016-02-01

    Full Text Available Precision Farming in agriculture allows a site-specific management of the crop. The aim of plant protection is to apply plant protection products (PPP according to the site specific requirements on the field. Within the context of a research program to promote innovation, a sprayer with direct injection of plant protection products was developed. The direct injection offers site specific spraying of different individual PPP in a single pass. The sprayer prototype is equipped with a special spray boom combining three nozzle lines. In order to prevent delay times, the nozzle lines are preloaded before spraying. First results for weed control from test stand measurements and field trials showed that the injection pumps work with high accuracy. The prototype can be used without delay times site specific with up to three different herbicides. Field trials for site-specific weed control in winter wheat demonstrate the applicability of the system under practical conditions. By treatment of subareas herbicides and therefore costs could be saved. A reduction in yield compared with the conventionally treated field areas could not be ascertained. Also an efficacy reduction through washout of active ingredient from target surfaces due to simultaneous use of all three nozzle lines with up to 1050 l/ha application rate could not be detected. At high water spray rates, the efficacy effect occurs delayed. Overall, the newly developed direct injection system proved fieldabillity during the first tests. So weed control can be carried out situation-responsive, which can save herbicides and environmental impacts are reduced.

  2. Alelopatia de cultivos de cobertura vegetal sobre plantas infestantes = Allelopathy of cover crop on weed plants

    Directory of Open Access Journals (Sweden)

    Luciene Kazue Tokura

    2006-07-01

    Full Text Available O presente trabalho avaliou o potencial alelopático de cultivos de cobertura vegetal de trigo, aveia preta, milheto, nabo forrageiro e colza sobre o desenvolvimento de plantas infestantes e verificou qual das coberturas vegetais exerce maior controle sobre as mesmas. Os cultivos de cobertura vegetal foram implantados sob preparo convencional (uma aração e uma gradagem no Núcleo Experimental de Engenharia Agrícola (NEEA, da Universidade Estadual do Oeste do Paraná (Unioeste, Cascavel, Estado do Paraná. Mensalmente, realizou-se o acompanhamento e identificação das plantas infestantes emersas nas áreas de cobertura vegetal no período de agosto de 2000 a agosto de 2001. Os resultados obtidos permitiram concluir que das espécies encontradas, o capim marmelada foi o que apresentou maior potencial alelopático e a erva-de-santa-maria o menor. As coberturasvegetais que apresentaram melhor controle do total de plantas infestantes presentes na área experimental, incluindo àquelas com reconhecido potencial alelopático, foram aveia preta, colza, nabo forrageiro e milheto.This work evaluated the cover crop allelopathic potential of wheat, black oat, pearl millet, turnip and rape on the development of weed plants. It also verified which cover crop has larger control on the weed plants. The cover crop was implanted under conventional tillage (one disk plowing plus one disk harrowing in the Experimental Nucleus of Agricultural Engineering (NEEA, of the State University of the West of Paraná (Unioeste, Cascavel, Paraná State. Monthly (from August 2000 to August 2001, weed plants identification in the cover crop area was made. Results showed that from the found species, the alexander grass was the one that presented larger allelopathic potential, and, the mexican-tea was the one that presented smaller control. The vegetable coverings that presented larger control of the total of weed plants in the experimental area, including those with

  3. Apparent competition and native consumers exacerbate the strong competitive effect of an exotic plant species.

    Science.gov (United States)

    Orrock, John L; Dutra, Humberto P; Marquis, Robert J; Barber, Nicholas

    2015-04-01

    Direct and indirect effects can play a key role in invasions, but experiments evaluating both are rare. We examined the roles of direct competition and apparent competition by exotic Amur honeysuckle (Lonicera maackii) by manipulating (1) L. maackii vegetation, (2) presence of L. maackii fruits, and (3) access to plants by small mammals and deer. Direct competition with L. maackii reduced the abundance and richness of native and exotic species, and native consumers significantly reduced the abundance and richness of native species. Although effects of direct competition and consumption were more pervasive, richness of native plants was also reduced through apparent competition, as small-mammal consumers reduced richness only when L. maackii fruits were present. Our experiment reveals the multiple, interactive pathways that affect the success and impact of an invasive exotic plant: exotic plants may directly benefit from reduced attack by native consumers, may directly exert strong competitive effects on native plants, and may also benefit from apparent competition.

  4. Host plant quality mediates competition between arbuscular mycorrhizal fungi

    NARCIS (Netherlands)

    B. Knegt; J. Jansa; O. Franken; D.J.P. Engelmoer; G.D.A. Werner; H. Bücking; E.T. Kiers

    2014-01-01

    Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of

  5. Host plant quality mediates competition between arbuscular mycorrhizal fungi

    NARCIS (Netherlands)

    Knegt, B.; Jansa, J.; Franken, O.; Engelmoer, D.J.P.; Werner, G.D.A.; Bücking, H.; Kiers, E.T.

    2016-01-01

    Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of

  6. Host plant quality mediates competition between arbuscular mycorrhizal fungi

    NARCIS (Netherlands)

    Knegt, B.; Jansa, J.; Franken, O.; Engelmoer, D.J.P.; Werner, G.D.A.; Bücking, H.; Kiers, E.T.

    2016-01-01

    Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of

  7. Período crítico de competição de plantas daninhas com a cultura do trigo Critical period for weed competition with wheat

    Directory of Open Access Journals (Sweden)

    D. Agostinetto

    2008-06-01

    Full Text Available Na cultura do trigo, diversos fatores limitam a sua produtividade, dentre os quais se destaca a competição imposta por plantas daninhas. O objetivo deste trabalho foi determinar o período crítico de interferência das plantas daninhas na cultura do trigo e os efeitos da competição em variáveis morfológicas e nos componentes da produtividade. O experimento foi conduzido a campo, no ano de 2006, no Centro Agropecuário da Palma, Capão do Leão/RS. Os fatores testados foram períodos de convivência e controle das plantas daninhas na cultura do trigo, cultivar FUNDACEP 52. Os períodos de convivência e/ou controle foram de: 0, 7, 14, 21, 28, 35, 42 e 126 dias após a emergência (DAE. Os resultados obtidos referentes às variáveis determinadas no final de cada período de controle ou convivência e por ocasião da colheita demonstraram que os componentes da produtividade do trigo não foram influenciados pela competição com plantas daninhas e que medidas efetivas de controle devem ser adotadas no período entre 12 e 24 dias após a emergência.Several factors limit wheat crop yield, with competition imposed by weed plants being the most outstanding. The objective of this study was to determine the critical period of weed interference in wheat crop and the effects of competition on morphological variables and yield components. This field experiment was carried out at Centro Agropecuário da Palma, Capão do Leão, RS, Brazil. Factors tested were periods of coexistence and weed plant control in FUNDACEP 52 wheat cultivar. Periods of coexistence and/or control were: 0, 7, 14, 21, 28, 35, 42 and 126 days after emergence (DAE. Results obtained for variables at the end of each control period or coexistence, and at harvesting, showed that wheat yield components were not affected by competition with weed plants and that effective control measures should be taken between 12 and 24 days after emergence.

  8. Early growth of Quercus castaneifolia (C.A. Meyer) seedlings as affected by weeding, shading and irrigation.

    Science.gov (United States)

    Mirzaei, Javad; Tabari, Masoud; Daroodi, Hadi

    2007-08-01

    The influence of shading, irrigation and weeding on survival, growth and morphology of 1-year Quercus castaneifolia seedlings was studied in north of Iran. The seedlings were grown under eight treatments including full-light versus artificial shading, irrigation versus non-irrigation and weed presence versus weed removing at three replicates. At the end of the first growing season seedling survival in all treatments was 100%. Weed removing had positive effect on height, diameter growth, slenderness coefficient and leaf area of Q. castaneifolia. Irrigation enhanced diameter growth and leaf area and shading increased leaf area. Irrigation had no significant effect on plant growth where the weed was removed. In weed plots seedlings growth and leaf area were greater in shading than in full-light. The results indicated that for 1 year Q. castaneifolia seedlings, weeding, in contrast to irrigation, is an essential factor. Where the weed competition is a difficulty, plantation with higher stem length should be applied.

  9. Levels of nitrogen and iodosulfuron + mesosulfuron affecting the wheat competitive ability against weeds

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    Mahdi Zare

    2014-08-01

    Full Text Available The trial was a split plot experiment based on randomized complete block design (RCBD with four replications in Abadeh, Fars, Iran, during 2010-2011 growing seasons. The treatments were consisted of three levels of nitrogen (200, 300, and 400 kg ha-1 and four herbicide application levels (53, 68, 83, and 97 g ha-1. Interaction effects of N fertilizer×herbicide levels on number spike per m2, number of kernels spike-1, 1000-seed weight, harvest index, seed yield, number of wild oat, number of common mallow and common mallow dry matter weight were significant. The maximum seed yield was related to 300 kg ha-1 N fertilizer with 97 g ha-1 herbicide treatment (3,526 kg ha-1 and the minimum seed yield was belonged to 200 kg ha-1 N fertilizer with 53 g ha-1 herbicide treatment (2,242 kg ha-1. Number of spikes m-2 was the most important trait contributing to the grain yield in wheat. In conclusion, weed control was essential for efficient use of N fertilizer by the crop. Therefore, integration of N fertilization and herbicide is recommended for the region to increase wheat grain yield.

  10. Cultivar weed-competitiveness in aerobic rice : heritability, correlated traits, and the potential for indirect selection in weed-free environments

    NARCIS (Netherlands)

    Zhao, D.L.; Atlin, G.N.; Bastiaans, L.; Spiertz, J.H.J.

    2006-01-01

    Forty rice (Oryza sativa L.) cultivars and breeding lines used in the International Rice Research Institute (IRRI) upland rice breeding program were evaluated in adjacent weed-free and weedy trials in aerobic soil conditions during the wet seasons of 2001, 2002, and 2003. The objectives of this

  11. Weed Identification and Control in Vegetable Crops.

    Science.gov (United States)

    Ferretti, Peter A., Comp.

    This agriculture extension service publication from Pennsylvania State University examines weed control and identification in vegetable crops. Contents include: (1) Types of weeds; (2) Reducing losses caused by weeds, general control methods and home garden weed control; (3) How herbicides are used; (4) Specific weeds in vegetable plantings; and…

  12. Weed Identification and Control in Vegetable Crops.

    Science.gov (United States)

    Ferretti, Peter A., Comp.

    This agriculture extension service publication from Pennsylvania State University examines weed control and identification in vegetable crops. Contents include: (1) Types of weeds; (2) Reducing losses caused by weeds, general control methods and home garden weed control; (3) How herbicides are used; (4) Specific weeds in vegetable plantings; and…

  13. Eficiência nutricional de cultivares de feijão em competição com plantas daninhas Nutritional efficiency of bean cultivars under competition with weeds

    Directory of Open Access Journals (Sweden)

    J.P Cury

    2013-03-01

    Full Text Available Apesar do ciclo efetivamente rápido do feijoeiro, a habilidade no uso dos nutrientes adicionados por ocasião do plantio e cobertura pode ser prejudicada pela presença de determinadas espécies de plantas daninhas. Objetivou-se com este trabalho avaliar os efeitos da competição entre três cultivares de feijão (IPR Colibri, IPR Eldorado e Pérola e seis espécies de plantas daninhas (Euphorbia heterophylla, Bidens pilosa, Cenchrus echinatus, Amaranthus spinosus, Commelina benghalensis e Brachiaria plantaginea no acúmulo de N, P e K pelas plantas e na eficiência nutricional do feijoeiro. O experimento foi realizado em condições controladas de temperatura e umidade, em delineamento de blocos casualizados, com quatro repetições. O período de convivência entre os cultivares de feijão e as plantas daninhas foi de 45 dias após emergência da cultura. Os cultivares de feijão apresentaram reduzido acúmulo relativo de N, P e K quando estavam em competição, sendo o sistema radicular o principal órgão afetado negativamente. O cultivar IPR Colibri foi o que menos tolerou a competição com plantas daninhas e E. heterophylla foi a espécie com menor poder de competição, enquanto A. spinosus e B. plantaginea foram as mais competitivas com a cultura do feijão. A eficiência nutricional do feijoeiro variou conforme o genótipo de feijão e a espécie infestante.Although the common bean has an effectively rapid cycle, its ability to use nutrients added during planting and cover can be affected by the presence of certain weed species. The objective of this study was to evaluate the effects of competition between three bean cultivars (IPR Colibri, IPR Eldorado, and Pérola and six weed species (Euphorbia heterophylla, Bidens pilosa, Cenchrus echinatus, Amaranthus spinosus, Commelina benghalensis and Brachiaria plantaginea on accumulation of N, P, and K by the plants, and on the nutritional efficiency of the bean plant. The experiment was

  14. Intercropping leeks to suppress weeds

    NARCIS (Netherlands)

    Baumann, D.T.; Kropff, M.J.; Bastiaans, L.

    2000-01-01

    Many field vegetables such as leek are weak competitors against weeds, causing high costs for weed management practice. Using celery as a companion cash crop was suggested to improve the weed suppression of leek. Three field experiments were carried out to study the intra- and interspecific competit

  15. Annual Glyphosate Treatments Alter Growth of Unaffected Bentgrass (Agrostis) Weeds and Plant Community Composition

    Science.gov (United States)

    Ahrens, Collin W.; Auer, Carol A.

    2012-01-01

    Herbicide resistance is becoming more common in weed ecotypes and crop species including turfgrasses, but current gaps in knowledge limit predictive ecological risk assessments and risk management plans. This project examined the effect of annual glyphosate applications on the vegetative growth and reproductive potential of two weedy bentgrasses, creeping bentgrass (CB) and redtop (RT), where the glyphosate resistance (GR) trait was mimicked by covering the bentgrass plants during glyphosate application. Five field plots were studied in habitats commonly inhabited by weedy bentgrasses including an agricultural hayfield, natural meadow, and wasteland. Results showed that annual glyphosate treatment improved bentgrass survivorship, vegetative growth, and reproductive potential compared with bentgrass in unsprayed subplots. In the second year of growth, RT plants had an 86-fold increase in flower number in glyphosate-treated subplots versus controls, while CB plants had a 20-fold increase. At the end of the three year study, plant community composition had changed in glyphosate-treated subplots in hayfield and meadow plots compared to controls. Soils in subplots receiving glyphosate had higher nitrate concentrations than controls. This is the first study to mimic the GR trait in bentgrass plants with the goal of quantifying bentgrass response to glyphosate selection pressure and understanding the impacts on surrounding plant communities. PMID:23226530

  16. Annual glyphosate treatments alter growth of unaffected bentgrass (Agrostis) weeds and plant community composition.

    Science.gov (United States)

    Ahrens, Collin W; Auer, Carol A

    2012-01-01

    Herbicide resistance is becoming more common in weed ecotypes and crop species including turfgrasses, but current gaps in knowledge limit predictive ecological risk assessments and risk management plans. This project examined the effect of annual glyphosate applications on the vegetative growth and reproductive potential of two weedy bentgrasses, creeping bentgrass (CB) and redtop (RT), where the glyphosate resistance (GR) trait was mimicked by covering the bentgrass plants during glyphosate application. Five field plots were studied in habitats commonly inhabited by weedy bentgrasses including an agricultural hayfield, natural meadow, and wasteland. Results showed that annual glyphosate treatment improved bentgrass survivorship, vegetative growth, and reproductive potential compared with bentgrass in unsprayed subplots. In the second year of growth, RT plants had an 86-fold increase in flower number in glyphosate-treated subplots versus controls, while CB plants had a 20-fold increase. At the end of the three year study, plant community composition had changed in glyphosate-treated subplots in hayfield and meadow plots compared to controls. Soils in subplots receiving glyphosate had higher nitrate concentrations than controls. This is the first study to mimic the GR trait in bentgrass plants with the goal of quantifying bentgrass response to glyphosate selection pressure and understanding the impacts on surrounding plant communities.

  17. Annual glyphosate treatments alter growth of unaffected bentgrass (Agrostis weeds and plant community composition.

    Directory of Open Access Journals (Sweden)

    Collin W Ahrens

    Full Text Available Herbicide resistance is becoming more common in weed ecotypes and crop species including turfgrasses, but current gaps in knowledge limit predictive ecological risk assessments and risk management plans. This project examined the effect of annual glyphosate applications on the vegetative growth and reproductive potential of two weedy bentgrasses, creeping bentgrass (CB and redtop (RT, where the glyphosate resistance (GR trait was mimicked by covering the bentgrass plants during glyphosate application. Five field plots were studied in habitats commonly inhabited by weedy bentgrasses including an agricultural hayfield, natural meadow, and wasteland. Results showed that annual glyphosate treatment improved bentgrass survivorship, vegetative growth, and reproductive potential compared with bentgrass in unsprayed subplots. In the second year of growth, RT plants had an 86-fold increase in flower number in glyphosate-treated subplots versus controls, while CB plants had a 20-fold increase. At the end of the three year study, plant community composition had changed in glyphosate-treated subplots in hayfield and meadow plots compared to controls. Soils in subplots receiving glyphosate had higher nitrate concentrations than controls. This is the first study to mimic the GR trait in bentgrass plants with the goal of quantifying bentgrass response to glyphosate selection pressure and understanding the impacts on surrounding plant communities.

  18. Complex Outcomes from Insect and Weed Control with Transgenic Plants: Ecological Surprises?

    Directory of Open Access Journals (Sweden)

    Thomas Bøhn

    2017-09-01

    Full Text Available Agriculture is fundamental for human survival through food production and is performed in ecosystems that, while simplified, still operate along ecological principles and retain complexity. Agricultural plants are thus part of ecological systems, and interact in complex ways with the surrounding terrestrial, soil, and aquatic habitats. We discuss three case studies that demonstrate how agricultural solutions to pest and weed control, if they overlook important ecological and evolutionary factors, cause “surprises”: (i the fast emergence of resistance against the crop-inserted Bt-toxin in South Africa, (ii the ecological changes generated by Bt-cotton landscapes in China, and (iii the decline of the monarch butterfly, Danaus plexippus, in North America. The recognition that we work with complex systems is in itself important, as it should limit the belief in reductionist solutions. Agricultural practices lacking eco-evolutionary understanding result in “surprises” like resistance evolution both in weeds and pest insects, risking the reappearance of the “pesticide treadmill”—with increased use of toxic pesticides as the follow-up. We recommend prioritization of research that counteracts the tendencies of reductionist approaches. These may be beneficial on a short term, but with trade-off costs on a medium- to long-term. Such costs include loss of biodiversity, ecosystem services, long-term soil productivity, pollution, and reduced food quality.

  19. Effect of Sunn Hemp (Crotalaria juncea L.) Cutting Date and Planting Density on Weed Suppression in Georgia, USA

    Science.gov (United States)

    A field study was conducted in 2008 and 2009 at the USDA, ARS, Plant Genetic Resources Conservation Unit in Griffin, GA to investigate weed suppression by sunn hemp (Crotalaria juncea L). The objectives were to: 1) evaluate the effects of apical meristem removal (AMR) at three dates [5, 6, and 7 wks...

  20. Federal Interagency Coordination for Invasive Plant Issues -- The Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW)

    Science.gov (United States)

    Westbrooks, Randy G.

    2011-01-01

    The U.S. Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW) is a formal partnership between 16 federal agencies that have invasive plant management and regulatory responsibilities for the United States and its territories. Efforts to develop a national level federal interagency committee to coordinate federal activities were initiated by national weed program managers with the USDA Forest Service and the Bureau of Land Management in 1989. FICMNEW was formally established through a Memorandum of Understanding that was signed by agency administrators of member agencies in August, 1994.

  1. Spatial and Spectral Methods for Weed Detection and Localization

    Directory of Open Access Journals (Sweden)

    Truchetet Frédéric

    2002-01-01

    Full Text Available This study concerns the detection and localization of weed patches in order to improve the knowledge on weed-crop competition. A remote control aircraft provided with a camera allowed to obtain low cost and repetitive information. Different processings were involved to detect weed patches using spatial then spectral methods. First, a shift of colorimetric base allowed to separate the soil and plant pixels. Then, a specific algorithm including Gabor filter was applied to detect crop rows on the vegetation image. Weed patches were then deduced from the comparison of vegetation and crop images. Finally, the development of a multispectral acquisition device is introduced. First results for the discrimination of weeds and crops using the spectral properties are shown from laboratory tests. Application of neural networks were mostly studied.

  2. Resource competition in plant invasions: emerging patterns and research needs

    Science.gov (United States)

    Gioria, Margherita; Osborne, Bruce A.

    2014-01-01

    Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species. PMID

  3. RoboWeedSupport

    DEFF Research Database (Denmark)

    Dyrmann, Mads; Nyholm Jørgensen, Rasmus

    2015-01-01

    Information about the weed population in fields is important for determining the optimal herbicides for the fields. A system based on images is presented that can provide support in determining the species and density of the weeds. Firstly, plants are segmented from the soil. Plants that after th...

  4. Terpenoid trans-caryophyllene inhibits weed germination and induces plant water status alteration and oxidative damage in adult Arabidopsis.

    Science.gov (United States)

    Araniti, F; Sánchez-Moreiras, A M; Graña, E; Reigosa, M J; Abenavoli, M R

    2017-01-01

    trans-Caryophyllene (TC) is a sesquiterpene commonly found as volatile component in many different aromatic plants. Although the phytotoxic effects of trans-caryophyllene on seedling growth are relatively explored, not many information is available regarding the phytotoxicity of this sesquiterpenes on weed germination and on adult plants. The phytotoxic potential of TC was assayed in vitro on weed germination and seedling growth to validate its phytotoxic potential on weed species. Moreover, it was assayed on the metabolism of Arabidopsis thaliana adult plants, through two different application ways, spraying and watering, in order to establish the primary affected organ and to deal with the unknown mobility of the compound. The results clearly indicated that TC inhibited both seed germination and root growth, as demonstrated by comparison of the ED50 values. Moreover, although trans-caryophyllene-sprayed adult Arabidopsis plants did not show any effect, trans-caryophyllene-watered plants became strongly affected. The results suggested that root uptake was a key step for the effectiveness of this natural compound and its phytotoxicity on adult plants was mainly due to the alteration of plant water status accompanied by oxidative damage. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

  5. Effects of vermicompost and nitrogen fertilizers on growth of Jimson weed (Datura stramonium L. as a medicinal plant

    Directory of Open Access Journals (Sweden)

    Ramin Abbaspour

    2016-05-01

    Full Text Available An experiment was conducted in order to evaluate the effect of organic (3 and 6 ton/ha vermicompost and chemical (150 and 300 kg/ha nitrogen fertilizers on growth, seed dispersal and heteroblasty of jimson weed at green house of Shiraz University in 2012. The results showed that the highest and the lowest plant growth, seed production and seed dispersal was in 300 kg/ha N and 6 ton/ha vermicompost, respectively. Position of the seeds on maternal plant had an important influence on the emergence percentage. Seeds on the middle and lowest parts of the plants had less emergence percentage compared with those on the higher parts. In general, application of 300 kg/ha nitrogen accelerated the growth of jimson weed and increase dispersal and heteroblasty of the jimson seed.

  6. PATHOGENICITY OF FUSARIUM SPP. ISOLATED FROM WEEDS AND PLANT DEBRIS IN EASTERN CROATIA TO WHEAT AND MAIZE

    Directory of Open Access Journals (Sweden)

    Jelena Ilić

    2012-12-01

    Full Text Available Pathogenicity of thirty isolates representing 14 Fusarium species isolated from weeds and plant debris in eastern Croatia was investigated in the laboratory. Pathogenicity tests were performed on wheat and maize seedlings. The most pathogenic Fusarium spp. was F. graminearum isolated from Amaranthus retroflexus, Abutilon theophrasti and Chenopodium album. There was a noticeable inter- and intraspecies variability in pathogenicity towards wheat and maize. Isolates of F. solani from Sonchus arvensis and F. verticillioides from C. album were highly pathogenic to wheat seedlings and apathogenic to maize seedlings. Isolates of F. venenatum were very pathogenic to wheat and maize being the first report about pathogenicity of this species. This experiment proves that weeds and plant debris can serve as alternate hosts and source of inoculum of plant pathogens.

  7. Native weeds and exotic plants: Relationships to disturbance in mixed-grass prairie

    Science.gov (United States)

    Larson, D.L.

    2003-01-01

    Disturbance frequently is implicated in the spread of invasive exotic plants. Disturbances may be broadly categorized as endogenous (e.g., digging by fossorial animals) or exogenous (e.g., construction and maintenance of roads and trails), just as weedy species may be native or exotic in origin. The objective of this study was to characterize and compare exotic and native weedy plant occurrence in and near three classes of disturbance -digging by prairie dogs (an endogenous disturbance to which native plants have had the opportunity to adapt), paved or gravel roads (an exogenous disturbance without natural precedent), and constructed trails (an exogenous disturbance with a natural precedent in trails created by movement of large mammals) - in three geographically separate national park units. I used plant survey data from the North and South Units of Theodore Roosevelt National Park and Wind Cave National Park in the northern mixed-grass prairie of western North and South Dakota, USA, to characterize the distribution of weedy native and exotic plants with respect to the three disturbance classes as well as areas adjacent to them. There were differences both in the susceptibility of the disturbance classes to invasion and in the distributions of native weeds and exotic species among the disturbance classes. Both exotic and native weedy species richness were greatest in prairie dog towns and community composition there differed most from undisturbed areas. Exotic species were more likely to thrive near roadways, where native weedy species were infrequently encountered. Exotic species were more likely to have spread beyond the disturbed areas into native prairie than were weedy native species. The response of individual exotic plant species to the three types of disturbance was less consistent than that of native weedy species across the three park units.

  8. Green ear yield and grain yield of maize cultivars in competition with weeds Rendimentos de espigas verdes e de grãos de cultivares de milho em competição com plantas daninhas

    Directory of Open Access Journals (Sweden)

    P.S.L. Silva

    2010-01-01

    Full Text Available The reduction in herbicide use is one of the greatest interests for modern agriculture and several alternatives are being investigated with this objective, including the adoption of cultivars that suppress weeds. The objective of this study was to verify if maize cultivars develop differently, in competition with weeds, to produce green ears and grain. Randomized complete block design was used, with split-plots and five replications. Cultivars DKB 390, DKB 466, DKB 350, AG 7000, AG 7575 and Master, were evaluated in the plots, without weeding and two weedings (at 22 and 41 days after sowing in sub plots. Twenty-one species were identified in the experimental area, the most frequent being Gramineae (Poaceae, Euphorbiaceae, Leguminosae (Fabaceae and Convolvulaceae species. There was no difference in the dry biomass above-ground part of the weeds in the plots of the evaluated cultivars. The cultivars behaved similarly in treatments with or without hoeing, except for plant height and ear height evaluations. Without hoeing, plant height increased in cultivar DKB 390, while plant height and ear height decreased in cultivar AG 7575. In the other cultivars, these traits did not change under weed control. The presence of weeds decreased the values of all traits employed to assess green corn yield, with the exception of the total number of green ears and grain yield.A redução do uso de herbicidas é um dos maiores interesses da agricultura moderna e várias alternativas estão sendo investigadas com esse objetivo, dentre elas a adoção de cultivares que suprimam as plantas daninhas. O objetivo do trabalho foi verificar se cultivares de milho, em competição com plantas daninhas, apresentam comportamento diferente para produzir espigas verdes e grãos. Utilizou-se o delineamento de blocos completos casualizados, com parcelas subdivididas, e cinco repetições. As cultivares DKB 390, DKB 466, DKB 350, AG 7000, AG 7575 e Master, semeadas nas parcelas

  9. Growth and yield of corn grain and green ear in competition with weeds Crescimento e rendimento de espigas verdes e de grãos de milho em competição com plantas daninhas

    Directory of Open Access Journals (Sweden)

    P.S.L Silva

    2009-12-01

    Full Text Available Studies on plant growth are interesting because they provide explanations for the factors that influence yield in various crops. The objective of this work was to evaluate growth and yield in corn cultivar AG1051, when in competition with weeds. Cultivar AG 1051 was submitted to two groups of treatments: weed control, and sampling periods for dry biomass evaluation. The weed control treatments consisted of hoeing (two hoeings performed at 20 and 40 days after sowing and no hoeing. Sampling periods consisted of collecting the above-ground part and roots of corn every fifteen days, until 105 days after sowing (DAS; the first sampling was performed 30 DAS. A completely randomized block design with ten replicates was used. For the characteristics evaluated in a single season, statistical analyses were carried out as a random block experiment. For the characteristics evaluated in several periods, statistical analyses were carried out as random blocks with split-plots (weed control assigned to plots. Fourteen weed species, unevenly distributed throughout the experimental area, were the most important. The growth observed for the above-ground part and root system of corn was 30% smaller in the non-hoed plots, compared to the hoed plots. Lack of weed control increased dry matter of the above-ground part of the weeds and reduced the number of unhusked and husked marketable green ears by 23% and 49%, respectively. Grain yield reduction caused by lack of weed control reached 38%.Apesar de trabalhosos, os estudos sobre o crescimento são de interesse porque fornecem explicações sobre os fatores que influenciam o rendimento das culturas. O objetivo do presente trabalho foi avaliar o crescimento e o rendimento de espigas verdes e de grãos do cultivar de milho AG 1051, em competição com plantas daninhas. Esse cultivar foi submetido a dois grupos de tratamento: controle de plantas daninhas e épocas de amostragem para avaliação da biomassa seca. Os

  10. Multispecies weed competition and their economic threshold on the wheat crop Interferência e nível de dano econômico de várias espécies infestantes na cultura de trigo

    Directory of Open Access Journals (Sweden)

    J. Gherekhloo

    2010-06-01

    Full Text Available Two field experiments were conducted to evaluate the effects of multispecies weed competition on wheat grain yield and to determine their economic threshold on the crop. The experiments were conducted in 2002, on two sites in Iran: at the Agricultural Research Station on Ferdowsi University of Mashhad (E1 and on the fields of Shirvan's Agricultural College (E2. A 15 x 50 m area of a 15 ha wheat field in E1 and a 15 x 50 m area of a 28 ha wheat field in E2 were selected as experimental sites. These areas were managed like other parts of the fields, except for the use of herbicides. At the beginning of the shooting stage, 30 points were randomly selected by dropping a 50 x 50 cm square marker on each site. The weeds present in E1 were: Avena ludoviciana, Chenopodium album, Solanum nigrum, Stellaria holostea, Convolvulus spp., Fumaria spp., Sonchus spp., and Polygonum aviculare. In E2 the weeds were A. ludoviciana, Erysimum sp., P. aviculare, Rapistrum rugosum, C. album, Salsola kali, and Sonchus sp. The data obtained within the sampled squares were submitted to regression equations and weeds densities were calculated in terms of TCL (Total Competitive Load. The regression analysis model indicated that only A. ludoviciana, Convolvulus spp. and C. album, in E1; and A. ludoviciana, S. kali, and R. rugosum, in E2 had a significant effect on the wheat yield reduction. Weed economic thresholds were 5.23 TCL in E1 and 6.16 TCL in E2; which were equivalent to 5 plants m-2 of A. ludoviciana or 12 plants m-2 of Convolvulus spp. or 19 plants m-2 of C. album in E1; and 6 plants m-2 A. ludoviciana, 13 plants m-2 S. kali and 27 plants m-2 R. rugosum in E2. Simulations of economic weed thresholds using several wheat grain prices and weed control costs allowed a better comparison of the experiments, suggesting that a more competitive crop at location E1 than at E2 was the cause of a lower weed competitive ability at the first location.Foram realizados dois

  11. Auxinic herbicides, mechanisms of action, and weed resistance: A look into recent plant science advances

    Directory of Open Access Journals (Sweden)

    Pedro Jacob Christoffoleti

    2015-08-01

    Full Text Available Auxin governs dynamic cellular processes involved at several stages of plant growth and development. In this review, we discuss the mechanisms employed by auxin in light of recent scientific advances, with a focus on synthetic auxins as herbicides and synthetic auxin resistance mechanisms. Two auxin receptors were reported. The plasma membrane receptor ABP1 (Auxin Binding Protein 1 alters the structure and arrangement of actin filaments and microtubules, leading to plant epinasty and reducing peroxisomes and mitochondria mobility in the cell environment. The second auxin receptor is the gene transcription pathway regulated by the SCFTir/AFB ubiquitination complex, which destroys transcription repressor proteins that interrupt Auxin Response Factor (ARF activation. As a result mRNA related with Abscisic Acid (ABA and ethylene are transcribed, producing high quantities of theses hormones. Their associated action leads to high production of Reactive Oxygen Species (ROS, leading to tissue and plant death. Recently, another ubiquitination pathway which is described as a new auxin signaling route is the F-box protein S-Phase Kinase-Associated Protein 2A (SKP2A. It is active in cell division regulation and there is evidence that auxin herbicides can deregulate the SKP2A pathway, which leads to severe defects in plant development. In this discussion, we propose that SFCSKP2A auxin binding site alteration could be a new auxinic herbicide resistance mechanism, a concept which may contribute to the current progress in plant biology in its quest to clarify the many questions that still surround auxin herbicide mechanisms of action and the mechanisms of weed resistance.

  12. Acúmulo e partição de nutrientes de cultivares de milho em competição com plantas daninhas Accumulation and partitioning of dry matter and nutrients in maize cultivars in competition with weed

    Directory of Open Access Journals (Sweden)

    J.P. Cury

    2012-06-01

    Full Text Available A competição por nutrientes varia com as espécies envolvidas e pode determinar o sucesso de plantas cultivadas em detrimento das espécies daninhas. Objetivou-se com este trabalho avaliar os efeitos da competição entre três cultivares de milho (híbrido DKB 390 YG, variedade AL 25 e híbrido SHS 4080 e seis espécies de plantas daninhas (Bidenspilosa, Cenchrus echinatus, Brachiaria brizantha, Commelina benghalensis, Brachiaria plantaginea e Euphorbia heterophylla no acúmulo e na alocação de nutrientes pelas plantas, determinando-se também o potencial dessas espécies em ciclar nutrientes. O experimento foi realizado em condições controladas de temperatura e umidade, em delineamento de blocos casualizados, com quatro repetições. O período de convivência entre os cultivares de milho e as plantas daninhas foi de 60 dias após emergência do milho. Os cultivares de milho apresentaram reduzida capacidade de acumular nutrientes quando em competição. O conteúdo relativo das espécies infestantes foi severamente reduzido em função dessa convivência. A capacidade de acumular nutrientes aparentemente não representa vantagem competitiva para as espécies infestantes. O cultivar AL 25 foi o que menos tolerou a competição, e B. brizantha e C. benghalensis foram as espécies com maior capacidade competitiva. B. brizantha e C. echinatus, livre da convivência com o milho, apresentaram elevado potencial em ciclar nutrientes.Competition for nutrients varies with the species involved and can determine the success of plants grown at the expense of weeds. The objective of this study was to evaluate the effects of competition among three cultivars of maize (hybrid DKB 390 YG, variety AL 25, and hybrid SHS 4080 and six weed species (Bidens pilosa, Cenchrus echinatus, Brachiaria brizantha, Commelina benghalensis, Brachiaria plantaginea and Euphorbia heterophylla on the accumulation and allocation of nutrients by plants, also determining the

  13. Dynamics of Weeds in the Soil Seed Bank: A Hidden Markov Model to Estimate Life History Traits from Standing Plant Time Series.

    Science.gov (United States)

    Borgy, Benjamin; Reboud, Xavier; Peyrard, Nathalie; Sabbadin, Régis; Gaba, Sabrina

    2015-01-01

    Predicting the population dynamics of annual plants is a challenge due to their hidden seed banks in the field. However, such predictions are highly valuable for determining management strategies, specifically in agricultural landscapes. In agroecosystems, most weed seeds survive during unfavourable seasons and persist for several years in the seed bank. This causes difficulties in making accurate predictions of weed population dynamics and life history traits (LHT). Consequently, it is very difficult to identify management strategies that limit both weed populations and species diversity. In this article, we present a method of assessing weed population dynamics from both standing plant time series data and an unknown seed bank. We use a Hidden Markov Model (HMM) to obtain estimates of over 3,080 botanical records for three major LHT: seed survival in the soil, plant establishment (including post-emergence mortality), and seed production of 18 common weed species. Maximum likelihood and Bayesian approaches were complementarily used to estimate LHT values. The results showed that the LHT provided by the HMM enabled fairly accurate estimates of weed populations in different crops. There was a positive correlation between estimated germination rates and an index of the specialisation to the crop type (IndVal). The relationships between estimated LHTs and that between the estimated LHTs and the ecological characteristics of weeds provided insights into weed strategies. For example, a common strategy to cope with agricultural practices in several weeds was to produce less seeds and increase germination rates. This knowledge, especially of LHT for each type of crop, should provide valuable information for developing sustainable weed management strategies.

  14. Weeds Cause Losses in Field Crops through Allelopathy

    Directory of Open Access Journals (Sweden)

    Tasawer ABBAS

    2016-03-01

    Full Text Available A large number of weeds are known to be associated with crops and causing economic losses. Weeds interfere with crops through competition and allelopathy. They produce secondary metabolites known as allelochemicals, which belong to numerous chemical classes such as phenolics, alkaloids, fatty acids, indoles, terpens etc. However, phenolics are the predominant class of allelochemicals. The allelochemicals release from weed plants takes place through leaf leachates, decomposition of plant residues, volatilization and root exudates. Weeds leave huge quantities of their residues in field and affect the associated, as well as succeeding crops, in various cropping systems. Liberation of allelochemicals from weeds affects the germination, stand establishment, growth, yield and physiology of crop plants. They cause substantial reduction in germination and growth of the crop plants by altering various physiological processes such as enzyme activity, protein synthesis, photosynthesis, respiration, cell division and enlargement, which ultimately leads to a significant reduction in crop yield. In crux, allelopathic weeds represent a potential threat for crop plants and cause economic losses.

  15. The distribution and extent of declared weeds and invader plants in the macro channel of the Olifants River System, Mpumalanga

    Directory of Open Access Journals (Sweden)

    W.J. Myburgh

    2005-06-01

    Full Text Available The vegetation associated with the macro channel of the Olifants River System was investigated to distinguish plant communities at a spatial scale of 1:250 000. The floristic data were analysed in terms of the sectional and longitudinal distribution and extent of declared weeds and invaders recorded during the survey. The results gained using the PHYTOTAB PC-classification and mapping program package revealed eight Grassland Biome and nine Savanna Biome plant communities from it's origin near the town of Breyten up to the border of the Kruger National Park. It was found that different invader species/weeds are associated with different biomes and habitats along the river system and that an alarming number of these species occur throughout the system.

  16. Weed risk assessment for aquatic plants: modification of a New Zealand system for the United States.

    Directory of Open Access Journals (Sweden)

    Doria R Gordon

    Full Text Available We tested the accuracy of an invasive aquatic plant risk assessment system in the United States that we modified from a system originally developed by New Zealand's Biosecurity Program. The US system is comprised of 38 questions that address biological, historical, and environmental tolerance traits. Values associated with each response are summed to produce a total score for each species that indicates its risk of invasion. To calibrate and test this risk assessment, we identified 39 aquatic plant species that are major invaders in the continental US, 31 species that have naturalized but have no documented impacts (minor invaders, and 60 that have been introduced but have not established. These species represent 55 families and span all aquatic plant growth forms. We found sufficient information to assess all but three of these species. When the results are compared to the known invasiveness of the species, major invaders are distinguished from minor and non-invaders with 91% accuracy. Using this approach, the US aquatic weed risk assessment correctly identifies major invaders 85%, and non-invaders 98%, of the time. Model validation using an additional 10 non-invaders and 10 invaders resulted in 100% accuracy for the former, and 80% accuracy for the latter group. Accuracy was further improved to an average of 91% for all groups when the 17% of species with scores of 31-39 required further evaluation prior to risk classification. The high accuracy with which we can distinguish non-invaders from harmful invaders suggests that this tool provides a feasible, pro-active system for pre-import screening of aquatic plants in the US, and may have additional utility for prioritizing management efforts of established species.

  17. Weed risk assessment for aquatic plants: modification of a New Zealand system for the United States.

    Science.gov (United States)

    Gordon, Doria R; Gantz, Crysta A; Jerde, Christopher L; Chadderton, W Lindsay; Keller, Reuben P; Champion, Paul D

    2012-01-01

    We tested the accuracy of an invasive aquatic plant risk assessment system in the United States that we modified from a system originally developed by New Zealand's Biosecurity Program. The US system is comprised of 38 questions that address biological, historical, and environmental tolerance traits. Values associated with each response are summed to produce a total score for each species that indicates its risk of invasion. To calibrate and test this risk assessment, we identified 39 aquatic plant species that are major invaders in the continental US, 31 species that have naturalized but have no documented impacts (minor invaders), and 60 that have been introduced but have not established. These species represent 55 families and span all aquatic plant growth forms. We found sufficient information to assess all but three of these species. When the results are compared to the known invasiveness of the species, major invaders are distinguished from minor and non-invaders with 91% accuracy. Using this approach, the US aquatic weed risk assessment correctly identifies major invaders 85%, and non-invaders 98%, of the time. Model validation using an additional 10 non-invaders and 10 invaders resulted in 100% accuracy for the former, and 80% accuracy for the latter group. Accuracy was further improved to an average of 91% for all groups when the 17% of species with scores of 31-39 required further evaluation prior to risk classification. The high accuracy with which we can distinguish non-invaders from harmful invaders suggests that this tool provides a feasible, pro-active system for pre-import screening of aquatic plants in the US, and may have additional utility for prioritizing management efforts of established species.

  18. Plant functional traits have globally consistent effects on competition.

    Science.gov (United States)

    Kunstler, Georges; Falster, Daniel; Coomes, David A; Hui, Francis; Kooyman, Robert M; Laughlin, Daniel C; Poorter, Lourens; Vanderwel, Mark; Vieilledent, Ghislain; Wright, S Joseph; Aiba, Masahiro; Baraloto, Christopher; Caspersen, John; Cornelissen, J Hans C; Gourlet-Fleury, Sylvie; Hanewinkel, Marc; Herault, Bruno; Kattge, Jens; Kurokawa, Hiroko; Onoda, Yusuke; Peñuelas, Josep; Poorter, Hendrik; Uriarte, Maria; Richardson, Sarah; Ruiz-Benito, Paloma; Sun, I-Fang; Ståhl, Göran; Swenson, Nathan G; Thompson, Jill; Westerlund, Bertil; Wirth, Christian; Zavala, Miguel A; Zeng, Hongcheng; Zimmerman, Jess K; Zimmermann, Niklaus E; Westoby, Mark

    2016-01-14

    Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions, but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear. Here we use growth data from more than 3 million trees in over 140,000 plots across the world to show how three key functional traits--wood density, specific leaf area and maximum height--consistently influence competitive interactions. Fast maximum growth of a species was correlated negatively with its wood density in all biomes, and positively with its specific leaf area in most biomes. Low wood density was also correlated with a low ability to tolerate competition and a low competitive effect on neighbours, while high specific leaf area was correlated with a low competitive effect. Thus, traits generate trade-offs between performance with competition versus performance without competition, a fundamental ingredient in the classical hypothesis that the coexistence of plant species is enabled via differentiation in their successional strategies. Competition within species was stronger than between species, but an increase in trait dissimilarity between species had little influence in weakening competition. No benefit of dissimilarity was detected for specific leaf area or wood density, and only a weak benefit for maximum height. Our trait-based approach to modelling competition makes generalization possible across the forest ecosystems of the world and their highly diverse species composition.

  19. Plant Size and Competitive Dynamics along Nutrient Gradients.

    Science.gov (United States)

    Goldberg, Deborah E; Martina, Jason P; Elgersma, Kenneth J; Currie, William S

    2017-08-01

    Resource competition theory in plants has focused largely on resource acquisition traits that are independent of size, such as traits of individual leaves or roots or proportional allocation to different functions. However, plants also differ in maximum potential size, which could outweigh differences in module-level traits. We used a community ecosystem model called mondrian to investigate whether larger size inevitably increases competitive ability and how size interacts with nitrogen supply. Contrary to the conventional wisdom that bigger is better, we found that invader success and competitive ability are unimodal functions of maximum potential size, such that plants that are too large (or too small) are disproportionately suppressed by competition. Optimal size increases with nitrogen supply, even when plants compete for nitrogen only in a size-symmetric manner, although adding size-asymmetric competition for light does substantially increase the advantage of larger size at high nitrogen. These complex interactions of plant size and nitrogen supply lead to strong nonlinearities such that small differences in nitrogen can result in large differences in plant invasion success and the influence of competition along productivity gradients.

  20. The influence of plant mulches on the content of phenolic compounds in soil and primary weed infestation of maize

    Directory of Open Access Journals (Sweden)

    Agnieszka Stokłosa

    2012-12-01

    Full Text Available In growing maize, an increase in the content of phenolic compounds and selected phenolic acids in soil was found after the incorporation of white mustard, buckwheat, spring barley, oats and rye mulches into the soil. The highest content of phenolic compounds in soil was found after oats mulch incorporation (20% more than in the control soil. The highest content of selected phenolic acids was found for the soil with the oats and rye mulch. Among the phenolic acids investigated, ferulic acid was most commonly found in the soil with the plant mulches. However, two phenolic acids: the protocatechuic and chlorogenic acid, were not detected in any soil samples (neither in the control soil nor in the mulched soil. At the same time, a decrease in the primary weed infestation level in maize was found in the plots with all the applied plant mulches, especially on the plots with oats, barley and mustard. The plant mulches were more inhibitory against monocotyledonous weeds than dicotyledonous ones. During high precipitation events and wet weather, a rapid decrease in the content of phenolic compounds in soil and an increase in the primary weed infestation level in maize were observed.

  1. Plant spacing and weed control affect sunflower stalk insects and the girdling behavior of Dectes texanus (Coleoptera: Cerambycidae).

    Science.gov (United States)

    Michaud, J P; Stahlman, P W; Jyoti, J L; Grant, A K

    2009-06-01

    We conducted a 2-yr study to determine the effects of crop density and weeds on levels of damage caused by stalk-boring insects in rain-fed sunflowers in west-central Kansas. Weed-free sunflower had higher seed weight and oil content in 2007, but not in 2006, but weeds did not affect infestation by stalk-boring insects in either year. High-density sunflower had lower estimated seed yield per unit area than low-density sunflower in both years, but percentage oil was slightly greater in the high-density treatment in 2006. Sunflowers were more heavily infested by larvae of Ataxia hubbardi Fisher, Cylindrocopturus adspersus (Leconte), and Pelochrista womanana (Kearfott) in 2006 than in 2007, ostensibly as a result of being planted earlier. Larvae of Dectes texanus LeConte appeared unaffected by planting date and were present in > 70% of plants in both years. Conditions during the period of crop maturity were much drier in 2006 than in 2007 and were associated with higher seed oil content and earlier and faster progression of stalk girdling by D. texanus larvae in both low- and high-density plots. There was also a strong effect of plant density on girdling behavior that seemed to be mediated by effects on soil moisture. Stalk girdling began earlier in high-density plots and a larger proportion of plants were girdled compared with low-density plots on all sampling dates in both years. Certain cultural tactics, in particular reduced plant spacing, have potential to delay the onset of girdling behavior by D. texanus larvae and thus mitigate losses that otherwise result from the lodging of girdled plants.

  2. Interference of allelopathic wheat with different weeds.

    Science.gov (United States)

    Zhang, Song-Zhu; Li, Yong-Hua; Kong, Chui-Hua; Xu, Xiao-Hua

    2016-01-01

    Interference of allelopathic wheat with weeds involves a broad spectrum of species either independently or synergistically with competitive factors. This study examined the interference of allelopathic wheat with 38 weeds in relation to the production of allelochemical 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) in wheat with and without root-root interactions. There were substantial differences in weed biomass and DIMBOA concentration in wheat-weed coexisting systems. Among 38 weeds, nine weeds were inhibited significantly by allelopathic wheat but the other 29 weeds were not. DIMBOA levels in wheat varied greatly with weed species. There was no significant relationship between DIMBOA levels and weed suppression effects. Root segregation led to great changes in weed inhibition and DIMBOA level. Compared with root contact, the inhibition of eight weeds was lowered significantly, while significantly increased inhibition occurred in 11 weeds with an increased DIMBOA concentration under root segregation. Furthermore, the production of DIMBOA in wheat was induced by the root exudates from weeds. Interference of allelopathic wheat with weeds not only is determined by the specificity of the weeds but also depends on root-root interactions. In particular, allelopathic wheat may detect certain weeds through the root exudates and respond by increasing the allelochemical, resulting in weed identity recognition. © 2015 Society of Chemical Industry.

  3. 7 CFR 201.50 - Weed seed.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Weed seed. 201.50 Section 201.50 Agriculture... REGULATIONS Purity Analysis in the Administration of the Act § 201.50 Weed seed. Seeds (including bulblets or tubers) of plants shall be considered weed seeds when recognized as weed seeds by the law or rules and...

  4. 7 CFR 201.15 - Weed seeds.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Weed seeds. 201.15 Section 201.15 Agriculture... REGULATIONS Labeling Agricultural Seeds § 201.15 Weed seeds. The percentage of weed seeds shall include seeds of plants considered weeds in the State into which the seed is offered for transportation or...

  5. Effect of weed harrowing frequency on plants, beneficial arthropods and crop yield

    DEFF Research Database (Denmark)

    Navntoft, Søren; Kristensen, Kristian; Johnsen, Ib

    2016-01-01

    * Weed harrowing is an alternative to herbicides but it may have negative effects on epigaeic arthropods. We assessed the effects of frequent (four) versus two harrowings during the growing season on the density and diversity of generalist arthropods and the weed flora. Collection by flooding...... was used to estimate arthropod densities, after collection of weeds and crop for biomass estimation. * The predatory guild of spiders Tachyporus spp. carabids was reduced by frequent harrowing. Spiders and Tachyporus spp. were the most sensitive, with up to 38% higher density in plots harrowed only twice...... compared with four times. Furthermore, a marginally significant decrease in arthropod diversity was found after four harrowings. The negative effect of frequent harrowing on arthropods was probably caused by a combination of direct lethal effects and habitat disruption. Additional harrowings reduced weeds...

  6. Native weeds and exotic plants: relationships to disturbance in mixed grass prairie

    Science.gov (United States)

    Larson, D.L.

    2003-01-01

    The paper compares distributions of native weedy species and exotic species with respect to three kinds of disturbance, roads, trails, and prairie dog towns. Data were collected at the north and south units of Theodore Roosevelt National Park and at Wind Cave National Park. The paper concludes that many exotic species differ substantially from native weeds in their exploitation of disturbance. It is thus not useful to manage exotics as if they were just another weed.

  7. Interferência das plantas daninhas sobre o desenvolvimento inicial de plantas de soja e arroz através da qualidade da luz Weed interference in the initial development of soybean and rice plants through light quality

    Directory of Open Access Journals (Sweden)

    A. Merotto Jr.

    2002-04-01

    and natural sources, weed competition and crop residues on the soil. The second experiment consisted of variation of weed competition in time, between rows and broadcast, and of devices placed inside the soil and along the rice crops to eliminate water and nutrient competition. Far-red light increased soybean plant height at 25 days after emergence (DAE. The presence of weeds until 15 and 16 DAE decreased rice and soybean growth, respectively. The effects of light quality alone, from weeds and isolated by the inter-row devices, decreased dry matter, and growth stage/tillering of rice plants at 15 and 29 DAE. The weeds can be considered as a factor that changes light quality, thus interfering in the initial crop development.

  8. Comparison of different cover crop mulches and extracts on inhibition of crop and weed growth

    Directory of Open Access Journals (Sweden)

    Sturm, Domonic Johannes

    2016-02-01

    Full Text Available Weed suppression of cover crops is a result of competition for light, space, water and nutrients and the release of allelochemicals in the soil. Two laboratory and greenhouse experiments were conducted to analyse biochemical effects of extracts and mulches of Fagopyrum tataricum (L. Gaertn., Raphanus sativus var. oleiformis Pers. and a cover crop mixture on germination and plant growth of the crop plants maize (Zea mays L. and sugar beet (Beta vulgaris ssp. vulgaris var. altissima Döll. and the weeds Chenopodium album L., Matricaria chamomilla L. and Stellaria media (L. Vill.. In the first experiment, aqueous cover crop extracts were applied on crop and weed seeds in germination assays. Germination rate, mean germination time and root length of crops and weeds were measured. In experiment 2, the influence of cover crop mulch on germination rate and dry weight of the test plants was determined after a period of 21 days. Significant reductions of the root length for all test plants were observed in experiment 1. Additionally, mean germination time was extended for crops and weeds by all cover crops. Germination rate and dry matter of crops and weeds were decreased significantly in experiment 2 compared to the untreated control. Root length, germination rate and mean germination time in germination tests in experiment 1 were found to be correlated with biomass of crops and weeds in experiment 2. This work reveals the important role of biochemical effects on weed suppression by cover crops.

  9. Phenotypic Evaluation of Weed-competitive Traits and Yield of Rice RILs from an Indica x Tropical Japonica Mapping Population

    Science.gov (United States)

    Indica rice cultivars can suppress weedy grasses. To better understand the important traits and genes underlying weed suppression and crop productivity, a recombinant inbred line (RIL) F8 population was developed by crossing non-suppressive ‘Katy’ and high-yielding, allelopathic ‘PI312777’. Three h...

  10. Bacterial endophytes enhance competition by invasive plants.

    Science.gov (United States)

    Rout, Marnie E; Chrzanowski, Thomas H; Westlie, Tara K; DeLuca, Thomas H; Callaway, Ragan M; Holben, William E

    2013-09-01

    Invasive plants can alter soil microbial communities and profoundly alter ecosystem processes. In the invasive grass Sorghum halepense, these disruptions are consequences of rhizome-associated bacterial endophytes. We describe the effects of N2-fixing bacterial strains from S. halepense (Rout and Chrzanowski, 2009) on plant growth and show that bacteria interact with the plant to alter soil nutrient cycles, enabling persistence of the invasive. • We assessed fluxes in soil nutrients for ∼4 yr across a site invaded by S. halepense. We assayed the N2-fixing bacteria in vitro for phosphate solubilization, iron chelation, and production of the plant-growth hormone indole-3-acetic acid (IAA). We assessed the plant's ability to recruit bacterial partners from substrates and vertically transmit endophytes to seeds and used an antibiotic approach to inhibit bacterial activity in planta and assess microbial contributions to plant growth. • We found persistent alterations to eight biogeochemical cycles (including nitrogen, phosphorus, and iron) in soils invaded by S. halepense. In this context, three bacterial isolates solubilized phosphate, and all produced iron siderophores and IAA in vitro. In growth chamber experiments, bacteria were transmitted vertically, and molecular analysis of bacterial community fingerprints from rhizomes indicated that endophytes are also horizontally recruited. Inhibiting bacterial activity with antibiotics resulted in significant declines in plant growth rate and biomass, with pronounced rhizome reductions. • This work suggests a major role of endophytes on growth and resource allocation of an invasive plant. Indeed, bacterial isolate physiology is correlated with invader effects on biogeochemical cycles of nitrogen, phosphate, and iron.

  11. Papéis do arranjo de plantas e do cultivar de soja no resultado da interferência com plantas competidoras Plant arrangement and soybean cultivar roles in weed interference results

    Directory of Open Access Journals (Sweden)

    M.A. Bianchi

    2010-01-01

    Full Text Available O uso combinado de cultivar competitivo e de arranjo equidistante de plantas pode incrementar a habilidade competitiva das culturas com plantas daninhas. Conduziram-se dois experimentos em campo na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul-RS, durante o ano agrícola 2001/02, com o objetivo de caracterizar a contribuição do cultivar e do espaçamento entre fileiras para a competitividade da soja com plantas concorrentes. No experimento 1, testaram-se condições de competição (ausência ou presença do cultivar de soja Fundacep 33, simulando planta daninha, espaçamentos entre fileiras (25 e 50 cm e seis cultivares de soja reagentes. No experimento 2, compararam-se condições de competição (ausência ou presença de plantas daninhas dicotiledôneas, espaçamentos entre fileiras (25 e 50 cm e cultivares de soja (IAS 5 e Fepagro RS 10. O cultivar Fepagro RS 10 apresenta características de planta que o destacam quanto à habilidade em competir com plantas daninhas, como plantas mais altas, com mais matéria seca, com maior razão de massa foliar e que proporcionam maior cobertura do solo, além de figurar entre os cultivares mais produtivos. O espaçamento reduzido entre fileiras proporciona cobertura precoce do solo pela soja, reduz a população e a matéria seca das plantas daninhas e mantém ou incrementa a produtividade de grãos de soja.The use of a soybean cultivar with competitive ability combined with an equidistant plant population distribution can enhance the competitive ability of crops against weeds. Two field experiments were carried out at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, in Eldorado do Sul-RS, during the 2001/2002 growing season, aiming to characterize the contribution of the cultivar and row spacing to soybean competitiveness against weeds. Experiment 1 tested the competitive conditions expressed by the presence or absence of the soybean cultivar

  12. Weeds as a source of plant growth promoting rhizobacteria in agricultural soils.

    Science.gov (United States)

    Sturz, A V; Matheson, B G; Arsenault, W; Kimpinski, J; Christie, B R

    2001-11-01

    The influence of plant growth promoting (PGP) activity of bacterial communities recovered from each of six weed species (barnyard grass (Echinochloa crusfalli (L.) Beauv.), corn spurrey (Spergula arvensis L.), goldenrod (Sonchus sp.), Italian ryegrass (Lolium multiflorum L.), lamb's-quarters (Chenopodium album L.), and quack grass (Agropyron repens (L.) Beauv.)) was examined in relation to the effect it had on the growth of the potato cultivar Russet Burbank. Bacterial species composition and community structure were compared, species-abundance relationships were determined, and those members conferring positive benefits for potato growth and development were identified. Of the genera identified, Bacillus, Arthrobacter, Stenotrophomonas, Acinetobacter, and Pseudomonas were the most common, and Stenotrophomonas maltophilia was the most frequent species recovered across all sources. Significantly higher population densities were found in the root zones of quack grass, compared with Italian ryegrass and lamb's-quarters. There were no significant differences in species richness among the root zones; however, evenness indices (species distribution) were significantly lower in corn spurrey (P = 0.05). Significantly higher diversity indices (Hill-1 and Hill-2 numbers) (P = 0.05) were found in the root zone soil communities of potato and goldenrod, indicating a decrease in the proportional abundance of common and very abundant species, respectively, while in barnyard grass, corn spurrey, and Italian ryegrass the reverse was the case. In both years of the study, Italian ryegrass and corn spurrey were consistently better sources of PGP rhizobacteria for potatoes, significantly (P rhizobacterial biodiversity and functional versatility can influence the numbers and types of PGP bacterial strains, and consequently may serve to improve soil quality.

  13. Differential host-finding abilities by a weed biocontrol insect create within-patch spatial refuges for nontarget plants.

    Science.gov (United States)

    Catton, Haley A; Lalonde, Robert G; De Clerck-Floate, Rosemarie A

    2014-10-01

    Many modern weed biocontrol insects exhibit transient "spillover" nontarget herbivory when and where insects are in high density, such as following biocontrol releases, or around dense target weed infestations. Understanding spatial patterns of herbivory is important for predicting efficacy and safety of biocontrol, as refuges from herbivory can buffer plants from population-level impacts. Here, we demonstrate that differential host-finding and arrestment behaviors by an oligophagous biocontrol insect lead to spatial refuges from nontarget herbivory around insect release points within mixed patches of target and nontarget plants. We created transient insect outbreaks by releasing large numbers of Mogulones crucifer Pallas (Coleoptera: Curculionidae) into naturally occurring rangeland patches of the nontarget plant Hackelia micrantha (Eastwood) J.L. Gentry with varying densities of its target weed Cynoglossum officinale L., and monitored spatial patterns of herbivory around release points after 4-7 wk. In complement, we conducted a mark-release-recapture (MRR) experiment to compare M. crucifer's target and nontarget host-finding and arrestment behaviors. For rangeland releases, 95% of nontarget herbivory occurred within 4.25 m of release points, independent of target plant density. Target herbivory occurred throughout our evaluation radii (up to 14 m), where maximum density of diffusing M. crucifer was 1/10 of that in the nontarget herbivory radius. In the MRR experiment, more weevils were recaptured on C. officinale (but not H. micrantha) than expected by chance. M. crucifer's lack of specialized nontarget host-finding and arrestment behaviors means that spatial refuges from herbivory are created for H. micrantha just meters away from sources of high weevil density.

  14. Weeds and Wildlife: Perceptions and Practices of Weed Managers

    Directory of Open Access Journals (Sweden)

    Emma H Carlos

    2014-01-01

    Full Text Available Negative impacts of invasive plants or weeds on biodiversity have been well established yet their role in providing key habitats and resources for wildlife has been little understood. Weed removal thus has the potential to adversely affect wildlife but whether this is considered during weed management is poorly known. To determine the extent of this knowledge, we examined the perceptions of weed managers regarding wildlife and weed management in Victoria, Australia. We surveyed 81 weed managers of varying levels of experience from different types of organisations, including state and local government, community groups and private companies. We found 90% of managers had observed wildlife-weed interactions and that most (70% adjusted management programmes to accommodate wildlife. Despite this, few (19% had adopted the recommended practice of combining gradual weed removal with re-vegetation. While management programmes included monitoring of native vegetation, consideration of wildlife monitoring in weed management was rare. This highlights the need for management to better understand and respond to wildlife-weed relationships. If the improvement of wildlife habitat is included in the objectives of weed programmes, as it should be, then wildlife should also be incorporated in project monitoring. This would lead to a greater understanding of the role weeds and their management have in each situation and, ultimately, more informed decision making.

  15. Produção e partição de matéria seca de cultivares de feijão em competição com plantas daninhas Dry matter production and distribution of bean cultivars under weed competition

    Directory of Open Access Journals (Sweden)

    J.P. Cury

    2011-03-01

    Full Text Available Objetivou-se com este trabalho avaliar os efeitos da competição entre três cultivares de feijão e seis espécies de plantas daninhas no crescimento inicial e na alocação de matéria seca pelas plantas. Adotou-se arranjo fatorial em esquema 3 x 6 + 9, constituído pela combinação de três genótipos de feijão (IPR Colibri, IPR Eldorado e Pérola em competição com seis espécies de plantas daninhas (Euphorbia heterophylla, Bidens pilosa, Cenchrus echinatus, Amaranthus spinosus, Commelina benghalensis e Brachiaria plantaginea, além de nove tratamentos adicionais, correspondentes aos cultivares de feijão e às espécies daninhas ausentes de competição. O delineamento foi em blocos casualizados com quatro repetições, e cada vaso contendo 5 L de substrato representou uma unidade experimental. O período de convivência entre os cultivares de feijão e as plantas daninhas foi de 45 dias após emergência da cultura; depois disso, coletou-se o material vegetal para avaliação da matéria seca e distribuição entre os diferentes órgãos (raízes, folhas e caule. Os cultivares de feijão apresentaram menor acúmulo de matéria seca quando estavam em competição com as espécies de plantas daninhas. A raiz foi o principal órgão afetado negativamente pela competição. De forma contrária, as folhas e o caule das espécies daninhas foram os órgãos mais prejudicados. De maneira geral, o cultivar Pérola foi o genótipo que mais tolerou a competição com plantas daninhas, e E. heterophylla foi a espécie daninha menos competitiva. A. spinosus e B. plantaginea foram as espécies com maior capacidade de competição com a cultura do feijão.This study aimed to determine the competitive ability of three bean cultivars and six weed species and to quantify the effect of competition on the plants' growth and dry mass allocation. A factorial scheme 3 x 6 + 9 was adopted, consisting of a combination of three genotypes (Colibri IPR, IPR

  16. Spatial interplay of plant competition and consumer foraging mediate plant coexistence and drive the invasion ratchet.

    Science.gov (United States)

    Orrock, John L; Baskett, Marissa L; Holt, Robert D

    2010-11-01

    Indirect effects may play an important role in structuring plant communities. Using a spatially explicit model of consumer foraging and plant competition, we demonstrate how the relationship between the spatial area over which plants compete and the spatial scale of consumer behaviour can determine the outcome of competition when one plant species provides a refuge for mobile consumers (i.e. refuge-mediated apparent competition). Once an initial population of the invader is established, complete invasion may be inevitable because of an ever-advancing invasion front ratchets forward driven by a feeding front of mobile consumers. Because the spatial extent of apparent competition determines the area available for colonization, consumers may also dictate the rate at which an invasion occurs. We find that, as long as refuge-mediated apparent competition is sufficiently localized, invasion is possible even in systems characterized by low overall levels of consumer pressure. Moreover, we show that a stable equilibrium can result in which both resident and invading plants coexist, suggesting that spatial heterogeneity created by refuge-mediated apparent competition may be important in mediating coexistence in plant communities. The spatial interplay of consumer behaviour and plant competition may be an underappreciated mechanism affecting the composition, diversity and spatial pattern of plant communities.

  17. Effects of nitrogen application method and weed control on corn yield and yield components.

    Science.gov (United States)

    Sepahvand, Pariya; Sajedi, Nurali; Mousavi, Seyed Karim; Ghiasvand, Mohsen

    2014-04-01

    The effects of nitrogen fertilizer application and different methods for weed control on yield and yield components of corn was evaluated in Khorramabad in 2011. The experiment was conducted as a split plot based on randomized complete block design in 3 replications. Nitrogen application was as main plot in 4 levels (no nitrogen, broadcasting nitrogen, banding nitrogen and sprayed nitrogen) and methods of weed control were in 4 levels (non-control weeds, application Equip herbicide, once hand control of weeds and application Equip herbicide+once time weeding) was as subplots. Result illustrated that effects of nitrogen fertilizer application were significant on grain and forage yield, 100 seeds weight, harvest index, grain number per row and cob weight per plant. Grain yield increased by 91.4 and 3.9% in application banding and broadcasting for nitrogen fertilizer, respectively, compared to the no fertilizer treatment. The results show improved efficiency of nitrogen utilization by banding application. Grain yield, harvest index, seed rows per cob, seeds per row and cob weight were increased by weed control. In the application of Equip herbicide+ hand weeding treatment corn grain yield was increased 126% in comparison to weedy control. It represents of the intense affects of weed competition with corn. The highest corn grain yield (6758 kg h(-1)) was related to the application banding of nitrogen fertilizer and Equip herbicide+once hand weeding.

  18. Plant functional traits have globally consistent effects on competition

    NARCIS (Netherlands)

    Kunstler, Georges; Falster, Daniel; Coomes, David A.; Poorter, Lourens

    2016-01-01

    Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions, but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear. Here we

  19. Negative plant-soil feedbacks increase with plant abundance, and are unchanged by competition.

    Science.gov (United States)

    Maron, John L; Laney Smith, Alyssa; Ortega, Yvette K; Pearson, Dean E; Callaway, Ragan M

    2016-08-01

    Plant-soil feedbacks and interspecific competition are ubiquitous interactions that strongly influence the performance of plants. Yet few studies have examined whether the strength of these interactions corresponds with the abundance of plant species in the field, or whether feedbacks and competition interact in ways that either ameliorate or exacerbate their effects in isolation. We sampled soil from two intermountain grassland communities where we also measured the relative abundance of plant species. In greenhouse experiments, we quantified the direction and magnitude of plant-soil feedbacks for 10 target species that spanned a range of abundances in the field. In soil from both sites, plant-soil feedbacks were mostly negative, with more abundant species suffering greater negative feedbacks than rare species. In contrast, the average response to competition for each species was unrelated with its abundance in the field. We also determined how competitive response varied among our target species when plants competed in live vs. sterile soil. Interspecific competition reduced plant size, but the strength of this negative effect was unchanged by plant-soil feedbacks. Finally, when plants competed interspecifically, we asked how conspecific-trained, heterospecific-trained, and sterile soil influenced the competitive responses of our target species and how this varied depending on whether target species were abundant or rare in the field. Here, we found that both abundant and rare species were not as harmed by competition when they grew in heterospecific-trained soil compared to when they grew in conspecific-cultured soil. Abundant species were also not as harmed by competition when growing in sterile vs. conspecific-trained soil, but this was not the case for rare species. Our results suggest that abundant plants accrue species-specific soil pathogens to a greater extent than rare species. Thus, negative feedbacks may be critical for preventing abundant species from

  20. The issues of weed infestation with environmentally hazardous plants and methods of their control

    Science.gov (United States)

    Bogdanov, V. L.; Posternak, T. S.; Pasko, O. A.; Kovyazin, V. F.

    2016-09-01

    The authors analyze expansion of segetal and ruderal vegetation on agricultural lands in Leningrad and Tomsk oblasts, typical for the European and Asian parts of Russia. The spreading conditions, composition of species, biological features and ecological requirements of the most aggressive species are identified. Some effective ways of weed control are suggested.

  1. Apical Dominance and Planting Density Effects on Weed Suppression by Sunn Hemp (Crotalaria juncea L.)

    Science.gov (United States)

    A field study was conducted in 2008 and 2009 in Citra, Florida to evaluate the effects of seeding rate and removal of apical dominance of sunn hemp (Crotalaria juncea L.) on weed suppression and seed production of sunn hemp. Three seeding rates of sunn hemp were used; a representative seed producti...

  2. Allelopathic Activity of Extracts from Different Brazilian Peanut (Arachis hypogaea L.) Cultivars on Lettuce (Lactuca sativa) and Weed Plants.

    Science.gov (United States)

    Casimiro, G S; Mansur, E; Pacheco, G; Garcia, R; Leal, I C R; Simas, N K

    2017-01-01

    Peanut (Arachis hypogaea L.) is the fourth most consumed oleaginous plant in the world, producing seeds with high contents of lipids, proteins, vitamins, and carbohydrates. Biological activities of different extracts of this species have already been evaluated by many researchers, including antioxidant, antitumoral, and antibacterial. In this work, the allelopathic activity of extracts from different Brazilian peanut cultivars against lettuce (Lactuca sativa) and two weed plants (Commelina benghalensis and Ipomoea nil) was studied. Aerial parts, roots, seeds, and seed coats were used for the preparation of crude extracts. Seed extract partitioning was performed with n-hexane, dichloromethane, ethyl acetate, n-butanol, and aqueous residue. Germination and growth of hypocotyls and rootlets were evaluated after one and five days of incubation with plant extracts, respectively. Crude seed extract and its dichloromethanic partition displayed highest allelopathic activity. These results contribute for the study of new potential natural herbicides.

  3. Agronomic Weeds.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University examines agronomic weed problems and control. Contents include a listing of the characteristics of weeds, a section on herbicides, and a section on the important weeds of agronomic crops in Pennsylvania. The herbicide section discusses systemic herbicides, contact…

  4. Agronomic Weeds.

    Science.gov (United States)

    Hartwig, Nathan L.

    This agriculture extension service publication from Pennsylvania State University examines agronomic weed problems and control. Contents include a listing of the characteristics of weeds, a section on herbicides, and a section on the important weeds of agronomic crops in Pennsylvania. The herbicide section discusses systemic herbicides, contact…

  5. Adapting weed management in rice to changing climates

    NARCIS (Netherlands)

    Rodenburg, J.; Meinke, H.B.

    2011-01-01

    This paper provides some of the scientific background on how projected environmental conditions could affect weeds and weed management in rice in Africa. Elevated CO2 levels may have positive effects on rice competitiveness with C4 weeds, but these are generally outnumbered by C3 species in weed pop

  6. ALLELOPATHIC EFFECTS OF WEED (Tridax procumbens L. EXTRACT ON SEED GERMINATION AND SEEDLING GROWTH OF SOME LEGUMINOUS PLANTS

    Directory of Open Access Journals (Sweden)

    D Femina

    2012-06-01

    Full Text Available Aqueous leaves extract of different concentrations of weed (Tridax procumbens L. was used to investigate their allelopathic effects on seed germination, root and shoot length and fresh and dry weight of some leguminous plants viz. Vigna radiata L. (Green gram, Dolichos biflorus L. (Horse gram and Vigna unguiculata L. (Cow pea. Mature fresh leaves of weed were crushed and soaked for 24h; the filtrates were diluted to make different concentrations and used to investigate their effect on the test crops. The experiment was carried out in sterilized petriplates with sterilized absorbent cotton kept under natural light dark cycle and was replicated 3 times. The aqueous leaf extract of Tridax procumbens was found to have inhibitory effect on germination, root, shoot elongation and fresh and dry weight of receptor plants. The bioassays indicated that the inhibitory effect was much more pronounced at higher concentrations. The most affected crop was green gram among the test crops. The inhibitory effect was much pronounced in root length as compared to shoot and germination of the receptor crops.

  7. Weed interference with peppermint (Mentha x piperita L.) and spearmint (Mentha spicata L.) crops under different herbicide treatments: effects on biomass and essential oil yield.

    Science.gov (United States)

    Karkanis, Anestis; Lykas, Christos; Liava, Vasiliki; Bezou, Anna; Petropoulos, Spyridon; Tsiropoulos, Nikolaos

    2017-05-15

    'Minor crops' such as spearmint and peppermint are high added value crops, despite the fact that their production area is comparably small worldwide. The main limiting factor in mint commercial cultivation is weed competition. Thus, field experiments were carried out to evaluate the effects of weed interference on growth, biomass and essential oil yield in peppermint and spearmint under different herbicide treatments. The application of pendimethalin and oxyfluorfen provided better control of annual weeds resulting in higher crop yield. Additionally, when treated with herbicides both crops were more competitive against annual weeds in the second year than in the first year. All pre-emergence herbicides increased biomass yield, since pendimethalin, linuron and oxyfluorfen reduced the density of annual weeds by 71-92%, 63-74% and 86-95%, respectively. Weed interference and herbicide application had no effect on essential oil content; however, a relatively strong impact on essential oil production per cultivated area unit was observed, mainly due to the adverse effect of weed interference on plant growth. Considering that pendimethalin and oxyfluorfen were effective against annual weeds in both spearmint and peppermint crops, these herbicides should be included in integrated weed management systems for better weed management in mint crops. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  8. Comprehensive Treatment of Dianchi Lake by Soilless Planting Weeds%滇池综合治理-无土栽种稗子

    Institute of Scientific and Technical Information of China (English)

    阎骄阳; 周庆; 闫自申

    2015-01-01

    回顾了滇池水污染和综合治理历程,提出在滇池特定水域无土栽培稗子的工程措施,并就无土种植的位置和面积、浮体材料、水上作业机械、稗子的综合利用和效益、稗子根部的处置等方面进行了可行性探讨。%The water pollution control management of Dianchi Lake was reviewed.The project of soilless planting weeds in some certain areas of Dianchi Lake was proposed.The exact location of weeds planting and its area and the related floating materials and operating machines were introduced.The feasible usage and the benefits of the weeds as well as the disposal of their roots were discussed.

  9. CRITICAL COMPETITION PERIOD BETWEEN COTTON AND (Gossypium hirsutum L. HARMFUL WEED COMMUNITIES IN THE GOIÁS STATE PERÍODO CRÍTICO DE COMPETIÇÃO ENTRE COMUNIDADES DE PLANTAS DANINHAS E O ALGODOEIRO (Gossypium hirsutum L. NO ESTADO DE GOIÁS

    Directory of Open Access Journals (Sweden)

    Armando M. Macêdo

    2007-09-01

    Full Text Available

    In order to study the critical time that weeds compete with the cotton plant, five trial experiments were conducted from 1978-1981. Two of the trials were carried out in a dark red latosoil with 4.70% organic matter and 10.73% clay, at the Rio Verde Agricultural School in the state of Goiás, during the 1978—79 and 1979—80 planting seasons. The other three were carried out in dark red latosoil, with a loam clay texture, moderate acidity and a low proportion of organic matter, at the Experimental station in Goiânia, Goiás during the 1978—79, 1979—80 and 1980—81 planting seasons. The treatments designed were: weeding up to 2, 4, 6, 8 first weeks, and weeding during the whole cycle ,and weeding after the 2, 4, 6, 8 first weeks and no weeding at all during the cycle. The results showed that weed competition , when not controlled, determined a yield loss of 88.75% in Goiânia and 90.65% in Rio Verde. Regarding the group control, which was maintained without weed competition, the best yield was obtained when the cotton was maintained without competition during eight weeks after the emergence in Rio Verde and during 4, 6, 8 weeks in Goiânia. The critical competition period occurred between the fourth and sixth weeks after the emergence in Rio Verde and in the fourth week after the emergence in Goiânia.

    Com a finalidade de estudar as épocas críticas de competição de plantas daninhas com o algodoeiro (Gossipium hirsutum L. , foram instalados cinco ensaios em área do Colégio Agrícola de Rio Verde — Goiás, no período de 1978 a 1981, sendo dois ensaios nos anos agrícolas de 1978/79 e 1979/80 em latossolo vermelho—escuro com 4,71% de matéria orgânica e 10,73% de argila. Os outros três ensaios foram instalados nos anos agrícolas 1978/79, 1979/80 e 1980/81, em área da Estação Experimental de

  10. Manejo de plantas daninhas na cultura de milho em função do arranjo espacial de plantas e características dos genótipos Weed management in the corn crop through plant spatial arrangement and characteristics of genotypes

    Directory of Open Access Journals (Sweden)

    Alvadi Antonio Balbinot Junior

    2005-02-01

    Full Text Available Para se obter elevada produtividade de grãos na cultura de milho, é preciso a utilização de práticas de manejo que reduzam o efeito negativo da infestação de plantas daninhas sobre a cultura. As relações de competição entre a cultura de milho e as plantas daninhas são usualmente influenciadas pelo arranjo espacial das plantas da cultura e pelas características morfofisiológicas dos genótipos. Esta revisão de literatura tem o objetivo de discutir a influência do arranjo espacial e das características dos genótipos das plantas de milho nas relações de competição entre a cultura e as plantas daninhas. Em geral, arranjos mais eqüidistantes entre plantas, obtidas pela redução do espaçamento entre fileiras, promovem maior competitividade à cultura. Em adição, genótipos que apresentam alta velocidade de crescimento no início do ciclo e características de planta apropriadas, especialmente estatura, sofrem menos a competição com plantas daninhas.Management practices contribute to reaching high grain yield in corn, which reduce negative effects of weed infestations. The competitive relationship between corn crop and weeds are usually modified by crop plant spatial arrangement and genotype morphophysiological characteristics. This literature review aims to discuss the influence of plant spatial arrangement and corn genotype characteristics in the competition relationship with weeds. Generally, equidistant plant arrangements, achieved through row width reduction, promote greater crop competitivity. Additionally, crop genotypes which present rapid initial growth, and suitable plant characteristics, particularly plant height, can tolerate interspecific plant competition better.

  11. Understanding the impact of plant competition on the coupling between vegetation and the atmosphere.

    NARCIS (Netherlands)

    van Loon, M.P.; Dekker, S.C.; Anten, Niels; Rietkerk, M.G.; de Arellano, Jordi Vila-Guerau

    2015-01-01

    Competition between plants for resources is an important selective force. As a result competition through natural selection determines vegetation functioning and associated atmospheric interactions. Our aim was to investigate how the coupling between vegetation and atmosphere is influenced by plant

  12. Understanding the impact of plant competition on the coupling between vegetation and the atmosphere

    NARCIS (Netherlands)

    Loon, van M.P.; Dekker, S.C.; Anten, N.P.R.; Rietkerk, M.; Vilà-Guerau De Arellano, J.

    2015-01-01

    Competition between plants for resources is an important selective force. As a result competition through natural selection determines vegetation functioning and associated atmospheric interactions. Our aim was to investigate how the coupling between vegetation and atmosphere is influenced by plant

  13. Aumento da população de plantas e uso de herbicidas no controle de plantas daninhas em milho Increase of plant population and use of herbicides to control weeds in corn

    Directory of Open Access Journals (Sweden)

    Aldo Merotto Junior

    1997-01-01

    plots: 35000, 50000, 68000 and 80000 plants ha-1. Incre asing plant population was more effective to decrease weed dry matter when no additional control was performed or herbicide was used in pre emergent. Weed influence on corn grain yield was greater at 80000 plantas ha-1 due to both weed and intraespecific competition. The use of high plant population can mitigate weed competition. However, it should be complemented with other methods of control during the early stages of corn development to achive high grain yields.

  14. Weed communities of rain-fed lowland rice vary with infestation by Rhamphicarpa fistulosa

    Science.gov (United States)

    Houngbédji, Tossimidé; Dessaint, Fabrice; Nicolardot, Bernard; Shykoff, Jacqui A.; Gibot-Leclerc, Stéphanie

    2016-11-01

    The facultative hemiparasitic plant Rhamphicarpa fistulosa (Orobanchaceae) thrives in seasonally wet soils in sub-Saharan Africa, mainly in marginal lowland rice growing environments where weeds are already a major constraint for rice production. Because lowland rice production is increasing in tropical Africa, it is important to ascertain the influence of R. fistulosa on weed plant communities in these rice-growing habitats. We investigated weed plant community richness and composition at four different levels of R. fistulosa infestation across two years of surveys from lowland rice fields in northern Togo (West Africa). Despite a lack of significant differences in community richness among sites with different R. fistulosa infestation levels, there were significant differences in community composition, both when estimated from presence-absence data and from relative abundance data, after controlling statistically for geographic proximity among sites. Rhamphicarpa fistulosa infestation, therefore, may influence the competitive balance between rice and its weeds and shape weed community structure. However, experimental studies are required to elucidate the weed host range of R. fistulosa and the direct and indirect effects of this hemiparasite in rice fields in order to predict its net impact on rice and its weed species.

  15. Weed suppression ability of spring barley varieties

    DEFF Research Database (Denmark)

    Christensen, Svend

    1995-01-01

    Three years of experiments with spring barley showed significant differences in weed suppression ability among varieties. Weed dry matter in the most suppressive variety, Ida, was 48% lower than the mean weed dry matter of all varieties, whereas it was 31% higher in the least suppressive variety......, Grit. Ranking varietal responses to weed competition in terms of grain yield loss corresponded well to ranking weed dry matter produced in crop weed mixtures. There was no correspondence between the varietal grain yields in pure stands and their competitiveness, suggesting that breeding to optimize...... interception model was developed to describe the light interception profiles of the varieties. A study of the estimated parameters showed significant correlation between weed dry matter, rate of canopy height development and the light interception profile. However, when estimates were standardized to eliminate...

  16. Communities of different plant diversity respond similarly to drought stress: experimental evidence from field non-weeded and greenhouse conditions

    Science.gov (United States)

    Lanta, Vojtěch; Doležal, Jiří; Zemková, Lenka; Lepš, Jan

    2012-06-01

    Accelerating rate of species loss has prompted researchers to study the role of species diversity in processes that control ecosystem functioning. Although negative impact of species loss has been documented, the evidence concerning its impact on ecosystem stability is still limited. Here, we studied the effects of declining species and functional diversity on plant community responses to drought in the field (open to weed colonization) and greenhouse conditions. Both species and functional diversity positively affected the average yields of field communities. However, this pattern was similar in both drought-stressed and control plots. No effect of diversity on community resistance, biomass recovery after drought and resilience was found because drought reduced biomass production similarly at each level of diversity by approximately 30 %. The use of dissimilarity (characterized by Euclidean distance) revealed higher variation under changing environments (drought-stressed vs. control) in more diverse communities compared to less species-rich assemblages. In the greenhouse experiment, the effect of species diversity affected community resistance, indicating that more diverse communities suffered more from drought than species-poor ones. We conclude that our study did not support the insurance hypothesis (stability properties of a community should increase with species richness) because species diversity had an equivocal effect on ecosystem resistance and resilience in an environment held under non-weeded practice, regardless of the positive relationship between sown species diversity and community biomass production. More species-rich communities were less resistant against drought-stressed conditions than species-poor ones grown in greenhouse conditions.

  17. Measuring competition in plant communities where it is difficult to distinguish individual plants

    DEFF Research Database (Denmark)

    Damgaard, Christian

    2011-01-01

    . The method allows direct measurements of the competitive effects of neighbouringzplants on plant performance and the estimation of parameters that describe the ecological processes of plantplant interactions during the growing season as well as the process of survival and recruitment between growing seasons...... measured by plant cover and vertical density (a measure that is correlated to the 3-dimensional space occupancy and biomass). Both plant cover and vertical density are measured in a standard pin-point analysis in the beginning and at the end of the growing season. In the outlined competition model....... Additionally, the presented method is suited for testing different ecological hypothesis on competitive interactions along environmental gradients, investigating the importance of competition, as well as predicting the likelihood of different ecological scenarios....

  18. A REVIEW OF WEED MANAGEMENT IN INDIA: THE NEED OF NEW DIRECTIONS FOR SUSTAINABLE AGRICULTURE

    Directory of Open Access Journals (Sweden)

    S K VERMA

    2016-03-01

    Full Text Available Weeds are the major deterrent to the development of sustainable crop production. Since weeds dictate most of the crop production practices and causes enormous losses (37 per cent due to their interference. Farmers follow several practices for managing weeds in different crops/cropping systems, of which at present the use of herbicides are on the top due to the scarcity of labors. The sustainability of these systems is being questioned because of environmental, social, and economic concerns caused by global competition, production cost, soil erosion, environmental pollution, and concern over the quality of rural life. Enhancing the crop competitiveness through preventive methods, cultural practices, mechanical methods, plant breeding, biotechnology, biological control and crop diversification will be the central thesis in new paradigms of weed management. Integration of above techniques will be key to sustainable weed management that maintain or enhance the crop productivity, profitability and environmental quality. This article explores the scope of sustainable weed management, growing concerns over herbicide resistance, environmental and health hazards of pesticides including herbicides and declining profitability are the major challenges of ‘high input’ agriculture. The goal of this review is to facilitate the development of ecologically based alternative methods for sustainable weed management that will support crop production systems, which require less tillage, herbicide and other inputs. To accomplish this goal, research efforts must be radically expanded in crop ecology and in the development of ecologically based technologies for weed management. Adoption of sustainable agricultural practices reduces the intensity of soil manipulation thereby creates an unfavorable condition for weed seed germination, reduces the organic matter depletion and soil erosion. Thus, the sustainable approaches could be an option for weed and soil

  19. Site-specific weed control technologies

    DEFF Research Database (Denmark)

    Christensen, S; Søgaard, H T; Kudsk, P

    2009-01-01

    Site-specific weed control technologies are defined as machinery or equipment embedded with technologies that detect weeds growing in a crop and, taking into account predefined factors such as economics, takes action to maximise the chances of successfully controlling them. In the article, we...... describe the basic parts of site specific weed control technologies, comprising of weed sensing systems, weed management models and precision weed control implements. A review of state-of-the-art technologies shows that several weed sensing systems and precision implements have been developed over the last...... two decades, though barriers prevent their breakthrough. Most important among these is the lack of a truly robust weed recognition method, owing to mutual shading among plants and limitations in the capacity of highly accurate spraying and weeding apparatuses.   Another barrier is the lack...

  20. Model of annual plants dynamics with facilitation and competition.

    Science.gov (United States)

    Droz, Michel; Pękalski, Andrzej

    2013-10-21

    An individual-based model describing the dynamics of one type of annual plants is presented. We use Monte Carlo simulations where each plant has its own history and the interactions among plants are between nearest neighbours. The character of the interaction (positive or negative) depends on local conditions. The plants compete for two external resources-water and light. The amount of water and/or light a plant receives depends on the external factor but also on local arrangement. Survival, growth and seed production of plants are determined by how well their demands for the resources are met. The survival and seeds production tests have a probabilistic character, which makes the dynamics more realistic than by using a deterministic approach. There is a non-linear coupling between the external supplies. Water evaporates from the soil at a rate depending on constant evaporation rate, local conditions and the amount of light. We examine the dynamics of the plant population along two environmental gradients, allowing also for surplus of water and/or light. We show that the largest number of plants is when the demands for both resources are equal to the supplies. We estimate also the role of evaporation and we find that it depends on the situation. It could be negative, but sometimes it has a positive character. We show that the link between the type of interaction (positive or negative) and external conditions has a complex character. In general in favourable environment plants have a stronger tendency for competitive interactions, leading to mostly isolated plants. When the conditions are getting more difficult, cooperation becomes the dominant type of interactions and the plants grow in clusters. The type of plants-sun-loving or shade tolerating, plays also an important role.

  1. Variação da competição interespecífica em milho em função do controle de plantas daninhas em faixas Variation of interspecific weed competition in corn as a function of banded weed control

    Directory of Open Access Journals (Sweden)

    A. Merotto Jr.

    2001-08-01

    Full Text Available O controle de plantas daninhas em faixas é mais uma estratégia que pode ser utilizada no manejo integrado de plantas daninhas (MIPD para aumentar a racionalização do uso do ambiente no cultivo de plantas. Os objetivos deste trabalho foram determinar o efeito do controle de plantas daninhas em faixas na linha ou na entrelinha e avaliar suas conseqüências sobre a competição interespecífica na cultura do milho. Os tratamentos constaram do estabelecimento de um gradiente de infestação de Brachiaria plantaginea, obtido com a variação da intensidade do controle em pré-emergência, e do controle de plantas daninhas em pós-emergência realizado em faixas na linha, na entrelinha ou em área total. O controle de plantas daninhas em pós-emergência em faixas não foi suficiente para reduzir os efeitos da competição interespecífica sobre o rendimento de grãos de milho, mesmo em baixas densidades de plantas daninhas. Os prejuízos causados pela presença de plantas daninhas na linha da cultura são duas a três vezes maiores em comparação com a presença destas plantas na entrelinha ou em área total da cultura. O controle de plantas daninhas na linha da cultura necessita de complementação com práticas culturais ou outros métodos de controle destas plantas na entrelinha.Banded weed control is one of the methods used for integrated weed management (IWM to increase the rationalization of environmental use in crop activities management. The aim of this work was to determine the effect of in-and between-row weed control and the effects of weed competition on corn. The treatments consisted in the establishment of a range of Brachiaria plantaginea densities by varying the intensity of weed control in pre-emergence, complemented with post-emergence weed control in-row, between row and broadcast. Banded weed control was not efficient in decreasing weed competition and reducing corn grain yield, even at low weed infestation. In-row weed

  2. The biology of habitat dominance; can microbes behave as weeds?

    Science.gov (United States)

    Cray, Jonathan A; Bell, Andrew N W; Bhaganna, Prashanth; Mswaka, Allen Y; Timson, David J; Hallsworth, John E

    2013-09-01

    Competition between microbial species is a product of, yet can lead to a reduction in, the microbial diversity of specific habitats. Microbial habitats can resemble ecological battlefields where microbial cells struggle to dominate and/or annihilate each other and we explore the hypothesis that (like plant weeds) some microbes are genetically hard-wired to behave in a vigorous and ecologically aggressive manner. These 'microbial weeds' are able to dominate the communities that develop in fertile but uncolonized--or at least partially vacant--habitats via traits enabling them to out-grow competitors; robust tolerances to habitat-relevant stress parameters and highly efficient energy-generation systems; avoidance of or resistance to viral infection, predation and grazers; potent antimicrobial systems; and exceptional abilities to sequester and store resources. In addition, those associated with nutritionally complex habitats are extraordinarily versatile in their utilization of diverse substrates. Weed species typically deploy multiple types of antimicrobial including toxins; volatile organic compounds that act as either hydrophobic or highly chaotropic stressors; biosurfactants; organic acids; and moderately chaotropic solutes that are produced in bulk quantities (e.g. acetone, ethanol). Whereas ability to dominate communities is habitat-specific we suggest that some microbial species are archetypal weeds including generalists such as: Pichia anomala, Acinetobacter spp. and Pseudomonas putida; specialists such as Dunaliella salina, Saccharomyces cerevisiae, Lactobacillus spp. and other lactic acid bacteria; freshwater autotrophs Gonyostomum semen and Microcystis aeruginosa; obligate anaerobes such as Clostridium acetobutylicum; facultative pathogens such as Rhodotorula mucilaginosa, Pantoea ananatis and Pseudomonas aeruginosa; and other extremotolerant and extremophilic microbes such as Aspergillus spp., Salinibacter ruber and Haloquadratum walsbyi. Some microbes

  3. Efficacy evaluation of selected herbicides on weed control and productivity evaluation of Bt cotton in Punjab.

    Science.gov (United States)

    Singh, Kulvir; Rathore, Pankaj

    2015-07-01

    Field experiments were conducted during Kharif 2012 and 2013 to evaluate the efficacy of different herbicides for weed management in cotton. Highest seed cotton yield (3537.3 kg ha(-1)) was recorded in weed free plots followed by pendimethalin @1.0 kg a.i ha(-1) as Pre.em.+quizalofopethyl @50 g a.i ha(-1) post-em at 2-4 weed leaf stage + one hoeing (3318.9 kg ha") owing to improved number of bolls per plant and boll weight. Statistically least yield was recorded underweedy check (1435.4 kg ha(-1)). Application of pyrithiobac sodium could not express any visible toxic effect on crop indicating its selectivity for cotton, although none of the tested new chemicals i.e., pyrithiobac sodium@ 62.5g a.i ha(-1) and quizalofopethyl @50g a.i ha(-1) when applied alone could not outperform the existing recommended chemicals for weed management. Yield losses to the extent of 6.2-59.4% were recorded due to weed competition. Weed control efficiency (WCE) was highest under weed free check (86.8%) followed by pendimethalin @1.0 kg a.i ha(-1) as Pre. em.+quizalofopethyl @50g a.i ha(-1), at 2-4 weed leaf stage + one hoeing (73.7%), whereas minimum values were for weedy check (24.7%). Though net returns (r94660 ha(-1)) were highest for weed free check but higher B:C ratio (2:11) was observed for pendimethalin @1.0 kg a.i ha(-1) as Pre em.+quizalofopethyl @50 g a.i ha(-1) post-em at 2-4 weed leaf stage+one hoeing. Therefore, for reasons such as labor shortage besides their timely availability, using these herbicides in combination with cultural practices could be the practical solution foreconomically efficient and effective weed management.

  4. Economics of supplemental weed control applications on spring-transplanted onions

    Science.gov (United States)

    Field research conducted to determine the relative benefits among alternative herbicides for weed control in onions (Allium cepa L.) measured weed control efficacy, impact of herbicides on crop injury, and the resulting weed competition on crop yields and marketable bulb size. Weed competition produ...

  5. Evidence for competition and cooperation among climbing plants.

    Science.gov (United States)

    Biernaskie, Jay M

    2011-07-07

    A plant's best strategy for acquiring resources may often depend on the identity of neighbours. Here, I ask whether plants adjust their strategy to local relatedness: individuals may cooperate (reduce competitiveness) with kin but compete relatively intensely with non-kin. In a greenhouse experiment with Ipomoea hederacea, neighbouring siblings from the same inbred line were relatively uniform in height; groups of mixed lines, however, were increasingly variable as their mean height increased. The reproductive yield of mixed and sibling groups was similar overall, but when adjusted to a common mean height and height inequality, the yield of mixed groups was significantly less. Where this difference in yield was most pronounced (among groups that varied most in height), mixed groups tended to allocate more mass to roots than comparable sibling groups, and overall, mixed groups produced significantly fewer seeds per unit mass of roots. These results suggest that, from the group perspective, non-kin may have wasted resources in below-ground competition at the expense of reproduction; kin groups, on the other hand, displayed the relative efficiency that is expected of reduced competitiveness.

  6. Understanding the impact of plant competition on the coupling between vegetation and the atmosphere.

    OpenAIRE

    van Loon, M.P.; Dekker, S.C.; Anten, Niels; Rietkerk, M.G.; de Arellano, Jordi Vila-Guerau

    2015-01-01

    Competition between plants for resources is an important selective force. As a result competition through natural selection determines vegetation functioning and associated atmospheric interactions. Our aim was to investigate how the coupling between vegetation and atmosphere is influenced by plant competition. Though included in some coupled vegetation-atmosphere models, little attention has been paid to systematically study the impact of plant competition in determining the evolution of sur...

  7. What's a Weed? Knowledge, Attitude and Behaviour of Park Visitors about Weeds.

    Directory of Open Access Journals (Sweden)

    Michael Ansong

    Full Text Available Weeds are a major threat to biodiversity globally degrading natural areas of high conservation value. But what are our attitudes about weeds and their management including weeds in national parks? Do we know what a weed is? Do we consider weeds a problem? Do we support their management? Are we unintentionally spreading weeds in parks? To answer these questions, we surveyed visitors entering a large popular national park near the city of Brisbane, Australia. Park visitors were knowledgeable about weeds; with >75% correctly defining weeds as 'plants that grow where they are not wanted'. About 10% of the visitors, however, provided their own sophisticated definitions. This capacity to define weeds did not vary with people's age, sex or level of education. We constructed a scale measuring visitors' overall concern about weeds in parks using the responses to ten Likert scale statements. Over 85% of visitors were concerned about weeds with older visitors, hikers, and those who could correctly define weeds more concerned than their counterparts. The majority think visitors unintentionally introduce seeds into parks, with many (63% having found seeds on their own clothing. However, over a third disposed of these seeds in ways that could facilitate weed spread. Therefore, although most visitors were knowledgeable and concerned about weeds, and support their control, there is a clear need for more effective communication regarding the risk of visitors unintentionally dispersing weed seeds in parks.

  8. What's a Weed? Knowledge, Attitude and Behaviour of Park Visitors about Weeds.

    Science.gov (United States)

    Ansong, Michael; Pickering, Catherine

    2015-01-01

    Weeds are a major threat to biodiversity globally degrading natural areas of high conservation value. But what are our attitudes about weeds and their management including weeds in national parks? Do we know what a weed is? Do we consider weeds a problem? Do we support their management? Are we unintentionally spreading weeds in parks? To answer these questions, we surveyed visitors entering a large popular national park near the city of Brisbane, Australia. Park visitors were knowledgeable about weeds; with >75% correctly defining weeds as 'plants that grow where they are not wanted'. About 10% of the visitors, however, provided their own sophisticated definitions. This capacity to define weeds did not vary with people's age, sex or level of education. We constructed a scale measuring visitors' overall concern about weeds in parks using the responses to ten Likert scale statements. Over 85% of visitors were concerned about weeds with older visitors, hikers, and those who could correctly define weeds more concerned than their counterparts. The majority think visitors unintentionally introduce seeds into parks, with many (63%) having found seeds on their own clothing. However, over a third disposed of these seeds in ways that could facilitate weed spread. Therefore, although most visitors were knowledgeable and concerned about weeds, and support their control, there is a clear need for more effective communication regarding the risk of visitors unintentionally dispersing weed seeds in parks.

  9. What’s a Weed? Knowledge, Attitude and Behaviour of Park Visitors about Weeds

    Science.gov (United States)

    Ansong, Michael; Pickering, Catherine

    2015-01-01

    Weeds are a major threat to biodiversity globally degrading natural areas of high conservation value. But what are our attitudes about weeds and their management including weeds in national parks? Do we know what a weed is? Do we consider weeds a problem? Do we support their management? Are we unintentionally spreading weeds in parks? To answer these questions, we surveyed visitors entering a large popular national park near the city of Brisbane, Australia. Park visitors were knowledgeable about weeds; with >75% correctly defining weeds as ‘plants that grow where they are not wanted’. About 10% of the visitors, however, provided their own sophisticated definitions. This capacity to define weeds did not vary with people’s age, sex or level of education. We constructed a scale measuring visitors’ overall concern about weeds in parks using the responses to ten Likert scale statements. Over 85% of visitors were concerned about weeds with older visitors, hikers, and those who could correctly define weeds more concerned than their counterparts. The majority think visitors unintentionally introduce seeds into parks, with many (63%) having found seeds on their own clothing. However, over a third disposed of these seeds in ways that could facilitate weed spread. Therefore, although most visitors were knowledgeable and concerned about weeds, and support their control, there is a clear need for more effective communication regarding the risk of visitors unintentionally dispersing weed seeds in parks. PMID:26252004

  10. Weed Garden: An Effective Tool for Extension Education

    Science.gov (United States)

    Beck, Leslie; Patton, Aaron J.

    2015-01-01

    A weed garden was constructed to quantify and improve identification skills among clientele. The garden was planted with over 100 weed species based on surveys on problematic weeds. The weed garden proved useful for introducing additional hands-on learning activities into traditional lecture-based seminars. Through seminar and field day attendee…

  11. Weed Garden: An Effective Tool for Extension Education

    Science.gov (United States)

    Beck, Leslie; Patton, Aaron J.

    2015-01-01

    A weed garden was constructed to quantify and improve identification skills among clientele. The garden was planted with over 100 weed species based on surveys on problematic weeds. The weed garden proved useful for introducing additional hands-on learning activities into traditional lecture-based seminars. Through seminar and field day attendee…

  12. An exotic invasive plant selects for increased competitive tolerance, but not competitive suppression, in a native grass.

    Science.gov (United States)

    Fletcher, Rebecca A; Callaway, Ragan M; Atwater, Daniel Z

    2016-06-01

    Exotic invasive plants can exert strong selective pressure for increased competitive ability in native plants. There are two fundamental components of competitive ability: suppression and tolerance, and the current paradigm that these components have equal influences on a species' overall competitive ability has been recently questioned. If these components do not have equal influences on overall ability, then selection on competitive tolerance and suppression may be disproportionate. We used naturally invaded communities to study the effects of selection caused by an invasive forb, Centaurea stoebe, on a native grass, Pseudoroegneria spicata. P. spicata plants were harvested from within dense C. stoebe patches and from nearby uninvaded areas, divided clonally into replicates, then transplanted into a common garden where they grew alone or competed with C. stoebe. We found that P. spicata plants collected from within C. stoebe patches were significantly more tolerant of competition with C. stoebe than P. spicata plants collected from uninvaded areas, but plants from inside invaded patches were not superior at suppressing C. stoebe. These results are consistent with the hypothesis that strong competitors may select for tolerance to competition more than for the ability to suppress neighbors. This has important implications for how native plant communities may respond to invasion over time, and how invasive and native species may ultimately coexist.

  13. Accumulation of macronutrients by weed and corn in coexistence in soil with different fertility managements

    Directory of Open Access Journals (Sweden)

    Christiane Augusta Diniz Melo

    2015-04-01

    Full Text Available The understanding of weed interference on crops is very important in agricultural systems. However, there is little known about the influence of soil fertility management in competitive relations between plants. The objective of this study was to evaluate the effects of mutual interference between weeds and corn on the content of macronutrients under different soil fertility managements. The experimental test was conducted in a greenhouse, considering four soil fertility managements (with calcium and magnesium silicate and fertilization; with limestone and fertilization; without correction of acidity, but with fertilization; without correction of acidity and without fertilization and eleven crops (five arrangements of competition between Zea mays and the weeds Urochloa brizantha, Ipomoea grandifolia, Conyza canadensis, Hyptis suaveolens and Bidens pilosa, plus the six species in monoculture. Corn had reductions exceeding 50% in the content of all macronutrients under interference of U. brizantha. Additionally, U. brizantha and B. pilosa in competition with corn has high ability to extract macronutrients in the four soil conditions. Calcium and magnesium silicate and limestone influenced variable on nutrient accumulation by weeds in monoculture or under interference. Corn grown in soil amended with silicate suffered greater competition with weeds compared to grown in soil amended with lime. U. brizantha was the specie most damaging to the crop. B. pilosa showed high potential for nutrient cycling in the four soil fertility management.

  14. Parthenium Weed (Parthenium hysterophorusL.)

    African Journals Online (AJOL)

    plant compounds (parthenin, chlorogenic acid, isocholorogenic acid, vanilic ... Parthenium Weed (Parthenium hysterophorus L.) Research in Ethiopia ..... other infested areas in Austaralia and America was conducted using cluster analysis.

  15. Biotechnology in weed control

    Science.gov (United States)

    Biotechnology can be used to enhance the management of weeds in several ways. Crops have been made resistant to herbicides by inserting transgenes that impart herbicide resistance into the plant genome. Glyphosate and glufosinate-resistant crops are commercialized in North America and crops made res...

  16. Competição entre soja resistente ao glyphosate e plantas daninhas em solo compactado Competition between glyphosate resistant soybean and weeds in compacted soil

    Directory of Open Access Journals (Sweden)

    J.B. Santos

    2008-03-01

    Full Text Available Objetivou-se com este trabalho avaliar a competição entre a soja (var. BRS 243 RR e as plantas daninhas Bidens pilosa e Brachiaria brizantha, em diferentes níveis de compactação do solo. Para isso, foram confeccionadas colunas de PVC (10 cm de diâmetro com três anéis: superior (com 5 cm de altura e densidade de 1,2 kg dm-3, intermediário (com 10 cm de altura e densidade variando entre 1,0 e 1,6 kg dm-3, conforme tratamento e inferior (com 10 cm de altura e densidade de 1,2 kg dm-3. Sobre as colunas foram realizados cinco cultivos: soja, B. pilosa, B. brizantha, soja e B. pilosa e soja e B. brizantha, em esquema fatorial com as densidades, perfazendo um total de 20 tratamentos. Aos 30 dias após emergência da soja, foram avaliadas a altura, a massa seca de folhas, de caule e de raízes (em cada anel, separadamente, a área foliar e a área foliar específica. Observou-se que B. brizantha foi mais competitiva que B. pilosa; contudo, esta última possui maior capacidade de exploração radicular em solos com maior nível de compactação, indicando maior adaptabilidade a condições como déficit hídrico e escassez de nutrientes. Considerando a capacidade competitiva da soja sobre as plantas daninhas, maiores níveis de compactação favorecem a cultura, em relação a B. pilosa.This work aimed to evaluate competition between soybean (BRS 243 RR and the weeds Bidens pilosa and Brachiaria brizantha, in soil with simulated compactation. Thus columns of PVC tubes (10 cm of diameter were made with three rings (superior (5 cm high and 1.2 kg dm-3 density; intermediate (10 cm high and around 1.0 and 1.6 kg dm-3 density and inferior (10 cm high and 1.2 kg dm-3 density. Five crops, soybean, B. pilosa, B. brizantha, soybean and B. pilosa, and soybean and B. brizantha, were cultivated on the columns in a factorial scheme with the densities, totaling 20 treatments. At 30 days after soybean emergence, height leaf, stem and root dry matter, leaf area

  17. An overview of plant volatile metabolomics, sample treatment and reporting considerations with emphasis on mechanical damage and biological control of weeds.

    Science.gov (United States)

    Beck, John J; Smith, Lincoln; Baig, Nausheena

    2014-01-01

    The technology for the collection and analysis of plant-emitted volatiles for understanding chemical cues of plant-plant, plant-insect or plant-microbe interactions has increased over the years. Consequently, the in situ collection, analysis and identification of volatiles are considered integral to elucidation of complex plant communications. Due to the complexity and range of emissions the conditions for consistent emission of volatiles are difficult to standardise. To discuss: evaluation of emitted volatile metabolites as a means of screening potential target- and non-target weeds/plants for insect biological control agents; plant volatile metabolomics to analyse resultant data; importance of considering volatiles from damaged plants; and use of a database for reporting experimental conditions and results. Recent literature relating to plant volatiles and plant volatile metabolomics are summarised to provide a basic understanding of how metabolomics can be applied to the study of plant volatiles. An overview of plant secondary metabolites, plant volatile metabolomics, analysis of plant volatile metabolomics data and the subsequent input into a database, the roles of plant volatiles, volatile emission as a function of treatment, and the application of plant volatile metabolomics to biological control of invasive weeds. It is recommended that in addition to a non-damaged treatment, plants be damaged prior to collecting volatiles to provide the greatest diversity of odours. For the model system provided, optimal volatile emission occurred when the leaf was punctured with a needle. Results stored in a database should include basic environmental conditions or treatments. Copyright © 2013 John Wiley & Sons, Ltd.

  18. Purslane Weed (Portulaca oleracea: A Prospective Plant Source of Nutrition, Omega-3 Fatty Acid, and Antioxidant Attributes

    Directory of Open Access Journals (Sweden)

    Md. Kamal Uddin

    2014-01-01

    Full Text Available Purslane (Portulaca oleracea L. is an important plant naturally found as a weed in field crops and lawns. Purslane is widely distributed around the globe and is popular as a potherb in many areas of Europe, Asia, and the Mediterranean region. This plant possesses mucilaginous substances which are of medicinal importance. It is a rich source of potassium (494 mg/100 g followed by magnesium (68 mg/100 g and calcium (65 mg/100 g and possesses the potential to be used as vegetable source of omega-3 fatty acid. It is very good source of alpha-linolenic acid (ALA and gamma-linolenic acid (LNA, 18 : 3 w3 (4 mg/g fresh weight of any green leafy vegetable. It contained the highest amount (22.2 mg and 130 mg per 100 g of fresh and dry weight, resp. of alpha-tocopherol and ascorbic acid (26.6 mg and 506 mg per 100 g of fresh and dry weight, resp.. The oxalate content of purslane leaves was reported as 671–869 mg/100 g fresh weight. The antioxidant content and nutritional value of purslane are important for human consumption. It revealed tremendous nutritional potential and has indicated the potential use of this herb for the future.

  19. Plant traits related to nitrogen uptake influence plant-microbe competition.

    Science.gov (United States)

    Moreau, Delphine; Pivato, Barbara; Bru, David; Busset, Hugues; Deau, Florence; Faivre, Céline; Matejicek, Annick; Strbik, Florence; Philippot, Laurent; Mougel, Christophe

    2015-08-01

    Plant species are important drivers of soil microbial communities. However, how plant functional traits are shaping these communities has received less attention though linking plant and microbial traits is crucial for better understanding plant-microbe interactions. Our objective was to determine how plant-microbe interactions were affected by plant traits. Specifically we analyzed how interactions between plant species and microbes involved in nitrogen cycling were affected by plant traits related to 'nitrogen nutrition in interaction with soil nitrogen availability. Eleven plant species, selected along an oligotrophic-nitrophilic gradient, were grown individually in a nitrogen-poor soil with two levels of nitrate availability. Plant traits for both carbon and nitrogen nutrition were measured and the genetic structure and abundance of rhizosphere. microbial communities, in particular the ammonia oxidizer and nitrate reducer guilds, were analyzed. The structure of the bacterial community in the rhizosphere differed significantly between plant species and these differences depended on nitrogen availability. The results suggest that the rate of nitrogen uptake per unit of root biomass and per day is a key plant trait, explaining why the effect of nitrogen availability on the structure of the bacterial community depends on the plant species. We also showed that the abundance of nitrate reducing bacteria always decreased with increasing nitrogen uptake per unit of root biomass per day, indicating that there was competition for nitrate between plants and nitrate reducing bacteria. This study demonstrates that nitrate-reducing microorganisms may be adversely affected by plants with a high nitrogen uptake rate. Our work puts forward the role of traits related to nitrogen in plant-microbe interactions, whereas carbon is commonly considered as the main driver. It also suggests that plant traits related to ecophysiological processes, such as nitrogen uptake rates, are more

  20. How light competition between plants affects trait optimization and vegetation-atmosphere feedbacks

    NARCIS (Netherlands)

    van Loon, M.P.

    2016-01-01

    How plants respond to climate change is of major concern, as plants will strongly impact future ecosystem functioning, food production and climate. Competition between plants for resources is an important selective force. As a result competition through natural selection determines vegetation functi

  1. Competition increases sensitivity of wheat (Triticum aestivum) to biotic plant-soil feedback

    NARCIS (Netherlands)

    Hol, W.H.G.; Boer, de W.; Hooven, ten F.; Putten, van der W.H.

    2013-01-01

    Plant-soil feedback (PSF) and plant competition play an important role in structuring vegetation composition, but their interaction remains unclear. Recent studies suggest that competing plants could dilute pathogenic effects, whereas the standing view is that competition may increase the sensitivit

  2. Evolutionary Agroecology: the potential for cooperative, high density, weed-suppressing cereals.

    Science.gov (United States)

    Weiner, Jacob; Andersen, Sven B; Wille, Wibke K-M; Griepentrog, Hans W; Olsen, Jannie M

    2010-09-01

    Evolutionary theory can be applied to improve agricultural yields and/or sustainability, an approach we call Evolutionary Agroecology. The basic idea is that plant breeding is unlikely to improve attributes already favored by millions of years of natural selection, whereas there may be unutilized potential in selecting for attributes that increase total crop yield but reduce plants' individual fitness. In other words, plant breeding should be based on group selection. We explore this approach in relation to crop-weed competition, and argue that it should be possible to develop high density cereals that can utilize their initial size advantage over weeds to suppress them much better than under current practices, thus reducing or eliminating the need for chemical or mechanical weed control. We emphasize the role of density in applying group selection to crops: it is competition among individuals that generates the 'Tragedy of the Commons', providing opportunities to improve plant production by selecting for attributes that natural selection would not favor. When there is competition for light, natural selection of individuals favors a defensive strategy of 'shade avoidance', but a collective, offensive 'shading' strategy could increase weed suppression and yield in the high density, high uniformity cropping systems we envision.

  3. Efeito do condicionamento osmótico de sementes de soja sobre a habilidade competitiva da cultura com as plantas daninhas Soybean seed osmoconditioning effect on the crop competitive ability against weeds

    Directory of Open Access Journals (Sweden)

    U.R. Nunes

    2003-04-01

    weeds. Soybean seeds, variety UFV 16, were harvested at the phenological stages R8 and R8 + 15 days and submitted to osmotic conditioning in a polyethylene glycol (PEG 6000 solution, at -0.8 Mpa, and 20ºC, for 96 hours. Seeds without pre-hydration treatment harvested at the same phenological stage were used as control. Seed germination and vigor were analyzed under laboratory conditions through the standard germination test, using a randomized complete design, 2x2 factorial, with 4 repetitions. Two experiments were conducted under field conditions, using seeds with and without osmotic conditioning, also harvested at the phenological stages R8 and R8 + 15 days, respectively. In both the experiments using randomized blocks with four repetitions, the effects of different weed coexistence periods (0, 15, 30, 45, 60 and 125 days after soybean emergence with the soybean crop were evaluated. The highest germination and vigor values related to initial and final stands and to grain yield were found in the treatments of seeds conditioned and harvested at the phenological stage R8. Other characteristics evaluated (plant height, number of nodes, number of pods per plant, number of seeds per plant, number of seeds per pod and 100-seed weight were not altered by conditioning. The competitive effect between weed and crop was verified by the lowest dry biomass values of the weeds, in the treatments in which seeds were harvested at the phenological stage R8 and were osmotically conditioned.

  4. Weeding Your Collection.

    Science.gov (United States)

    Kerby, Ramona

    2002-01-01

    Offers guidelines for weeding as part of school library collection development. Highlights include developing a weeding policy; and the CREW (Continuous Review Evaluation and Weeding) method, including reasons for weeding, scheduling, and guidelines for fiction and for nonfiction. (LRW)

  5. Nutritional Value and Toxins in Various Noxious Weeds

    OpenAIRE

    Burritt, Beth; Hart, Rae Ann

    2014-01-01

    Teaching animals to eat noxious weeds may be a solution to reducing noxious weeds. Grazing animals often avoid eating weeds due to novelty even though weeds are often as nutritious as many of our planted pasture and rangelands species. This fact sheet provides livestock producers with the nutritive values of many common weeds. These values were summarized from a variety of peer-reviewed journal articles.

  6. Weed detection in 3D images

    OpenAIRE

    Piron, Alexis; Van der heijden, F.; Destain, Marie-France

    2011-01-01

    Machine vision has been successfully used for mechanical destruction of weeds between rows of crops. Knowledge of the position of the rows where crops should be growing and the assumption that plants growing outside such positions are weeds may be used in such systems. However for many horticultural crops, the automatic removal of weeds from inside a row or bands of crops in which the weeds are mixed with plants in a random manner is not solved. The aim of this study was to verify that plant ...

  7. Fitness consequences of indirect plant defence in the annual weed, Sinapis arvensis

    NARCIS (Netherlands)

    Gols, Rieta; Wagenaar, Roel; Poelman, Erik H.; Kruidhof, H. Marjolein; van Loon, Joop J.A.; Harvey, Jeffrey A.

    2015-01-01

    * Plant traits that enhance the attraction of the natural enemies of their herbivores have been postulated to function as an ‘indirect defence’. An important underlying assumption is that this enhanced attraction results in increased plant fitness due to reduced herbivory. This assumption has been r

  8. Fitness consequences of indirect plant defence in the annual weed, Sinapis arvensis

    NARCIS (Netherlands)

    Gols, R.; Wagenaar, R.; Poelman, E.H.; Kruidhof, H.M.; Loon, van J.J.A.; Harvey, J.A.

    2015-01-01

    Plant traits that enhance the attraction of the natural enemies of their herbivores have been postulated to function as an 'indirect defence'. An important underlying assumption is that this enhanced attraction results in increased plant fitness due to reduced herbivory. This assumption has been rar

  9. Fitness consequences of indirect plant defence in the annual weed, Sinapis arvensis

    NARCIS (Netherlands)

    Gols, R.; Wagenaar, R.; Poelman, E.H.; Kruidhof, M.; Loon, van J.J.A.; Harvey, J.A.

    2015-01-01

    1. Plant traits that enhance the attraction of the natural enemies of their herbivores have been postulated to function as an ‘indirect defence’. An important underlying assumption is that this enhanced attraction results in increased plant fitness due to reduced herbivory. This assumption has been

  10. Fitness consequences of indirect plant defence in the annual weed, Sinapis arvensis

    NARCIS (Netherlands)

    Gols, R.; Wagenaar, R.; Poelman, E.H.; Kruidhof, H.M.; Loon, van J.J.A.; Harvey, J.A.

    2015-01-01

    Plant traits that enhance the attraction of the natural enemies of their herbivores have been postulated to function as an 'indirect defence'. An important underlying assumption is that this enhanced attraction results in increased plant fitness due to reduced herbivory. This assumption has been

  11. Fitness consequences of indirect plant defence in the annual weed, Sinapis arvensis

    NARCIS (Netherlands)

    Gols, R.; Wagenaar, R.; Poelman, E.H.; Kruidhof, M.; Loon, van J.J.A.; Harvey, J.A.

    2015-01-01

    1. Plant traits that enhance the attraction of the natural enemies of their herbivores have been postulated to function as an ‘indirect defence’. An important underlying assumption is that this enhanced attraction results in increased plant fitness due to reduced herbivory. This assumption has been

  12. Solanum nigrum L. weed plants as a remediation tool for metalaxyl-polluted effluents and soils.

    Science.gov (United States)

    Teixeira, Jorge; Sousa, Alexandra de; Azenha, Manuel; Moreira, José Tiago; Fidalgo, Fernanda; Fernando Silva, A; Faria, Joaquim L; Silva, Adrián M T

    2011-10-01

    In this work, the phytoremediation potential of metalaxyl, a commonly used persistent, mobile and leachy fungicide, by Solanum nigrum L. plants was studied. The study revealed that this plant species can be used as an excellent metalaxyl phytoremediation tool, thus providing a cost effective and environmentally friendly clean technology for the decontamination of sites and effluents. As it can be sowed directly in the remediation site, is able to complete its life cycle without suffering major stress. Because it accumulates high amounts of the fungicide in the aboveground tissues, enables its concentration and proper disposal by cutting off the corresponding plant part. The study also suggests that the tolerance to metalaxyl is due to a suitable antioxidant response comprising proline accumulation and guaiacol peroxidase and glutathione-S-transferase enhanced activities, that reduce oxidative damage to the plant organs. Copyright © 2011 Elsevier Ltd. All rights reserved.

  13. Can global weed assemblages be used to predict future weeds?

    Directory of Open Access Journals (Sweden)

    Louise Morin

    Full Text Available Predicting which plant taxa are more likely to become weeds in a region presents significant challenges to both researchers and government agencies. Often it is done in a qualitative or semi-quantitative way. In this study, we explored the potential of using the quantitative self-organising map (SOM approach to analyse global weed assemblages and estimate likelihoods of plant taxa becoming weeds before and after they have been moved to a new region. The SOM approach examines plant taxa associations by analysing where a taxon is recorded as a weed and what other taxa are recorded as weeds in those regions. The dataset analysed was extracted from a pre-existing, extensive worldwide database of plant taxa recorded as weeds or other related status and, following reformatting, included 187 regions and 6690 plant taxa. To assess the value of the SOM approach we selected Australia as a case study. We found that the key and most important limitation in using such analytical approach lies with the dataset used. The classification of a taxon as a weed in the literature is not often based on actual data that document the economic, environmental and/or social impact of the taxon, but mostly based on human perceptions that the taxon is troublesome or simply not wanted in a particular situation. The adoption of consistent and objective criteria that incorporate a standardized approach for impact assessment of plant taxa will be necessary to develop a new global database suitable to make predictions regarding weediness using methods like SOM. It may however, be more realistic to opt for a classification system that focuses on the invasive characteristics of plant taxa without any inference to impacts, which to be defined would require some level of research to avoid bias from human perceptions and value systems.

  14. Can Global Weed Assemblages Be Used to Predict Future Weeds?

    Science.gov (United States)

    Morin, Louise; Paini, Dean R.; Randall, Roderick P.

    2013-01-01

    Predicting which plant taxa are more likely to become weeds in a region presents significant challenges to both researchers and government agencies. Often it is done in a qualitative or semi-quantitative way. In this study, we explored the potential of using the quantitative self-organising map (SOM) approach to analyse global weed assemblages and estimate likelihoods of plant taxa becoming weeds before and after they have been moved to a new region. The SOM approach examines plant taxa associations by analysing where a taxon is recorded as a weed and what other taxa are recorded as weeds in those regions. The dataset analysed was extracted from a pre-existing, extensive worldwide database of plant taxa recorded as weeds or other related status and, following reformatting, included 187 regions and 6690 plant taxa. To assess the value of the SOM approach we selected Australia as a case study. We found that the key and most important limitation in using such analytical approach lies with the dataset used. The classification of a taxon as a weed in the literature is not often based on actual data that document the economic, environmental and/or social impact of the taxon, but mostly based on human perceptions that the taxon is troublesome or simply not wanted in a particular situation. The adoption of consistent and objective criteria that incorporate a standardized approach for impact assessment of plant taxa will be necessary to develop a new global database suitable to make predictions regarding weediness using methods like SOM. It may however, be more realistic to opt for a classification system that focuses on the invasive characteristics of plant taxa without any inference to impacts, which to be defined would require some level of research to avoid bias from human perceptions and value systems. PMID:23393591

  15. Modeling plant, microorganisms, and mineral surface competition for soil nitrogen and phosphorus: Competition representations and ecological significance

    Science.gov (United States)

    Zhu, Q.; Riley, W. J.; Chambers, J. Q.; Tang, J.

    2014-12-01

    It is widely accepted that terrestrial ecosystem carbon dynamics are strongly coupled and controlled by soil nutrients status. Nutrient availability serves as an indicator of aboveground carbon productivity and ecosystem stability, especially when soils are infertile. In these conditions, plants have to outcompete microorganism and mineral surfaces to acquire nutrients required for photosynthesis, respiration, seed production, defense, etc. It is usually hypothesized that microbes are short-term winners but long-term losers in nutrient competition. Microbes quickly trap available soil nitrogen and phosphorous, thereby preventing nutrient inaccessibility through hydrological leaching and mineral surface adsorption. Over longer temporal scales, nutrients are released into the soil and become available for plant uptake. Despite its ecological significance, nutrient competition is either absent or over-simplified (e.g., assuming all consumers are equally competitive) in terrestrial biogeochemistry models. Here, we aim to test the representation of different competitive strategies and to investigate their ecological consequences with a newly developed biogeochemical model structure. The new model includes three major soil nutrients (ammonia, nitrate, and phosphate) and multiple consumers (plants, microbes, mineral surfaces, nitrifiers, and denitrifiers). We analyze predicted soil carbon, nitrogen, and phosphorus dynamics with three different competitive strategies: (1) plants compete poorly against microorganisms; (2) all consumers are equally competitive; and (3) an explicit Equilibrium Chemical Approximation (ECA; Tang and Riley (2013)) treatment. We find that very different ecosystem states are predicted when assuming different competitive structures, and that the ECA approach provides the best match with a large suite of observational constraints from tropical experimental and transect studies. We conclude that terrestrial biogeochemical models should represent a

  16. 不同种植方式对玉米田杂草群落及生长发育的影响%Effect of different planting methods on weed group and weed growth and development in corn field

    Institute of Scientific and Technical Information of China (English)

    刘芳; 殷红; 郭范顺; 李建东; 燕雪飞; 王国娇; 韦岩

    2009-01-01

    Through inter-species of corn and alfalfa and cor n-species comparison, discussed the impact of grow alfalfa to weed group and we ed growth and development in corn fields. The result indicated that, the Echinochloa crusgalli and Polygonum orientale important value were higher in corn-species, were the idominant species, in in ter-species of corn and alfalfa field the idominant species were the Polygonu m orientale, Echinochloa crusgalli, Chenopodium album, Amaranthus retroflexus L and Solanum nigrum Linn, Abutilon theophrasti Medic; Various growth s tages in corn, inter species of alfalfa the weed biomass was lower than the corn species, most of the time, weed height was lower than the corn species; Inter- species of corn and alfalfa field, compared with the corn-species, ear length, ear rows, row rows, ear weight, grain weight per spike, weight of hundred grains and yield increased by 6.6%,7.6%,2.2%,12.28%,9.9%,7.8%,4.3%. Inter- species of alfalfa can control the number of weeds, inhibit weed biomass increas ed, increase corn production through of the alfalfa. This study could provide sc ientific bases for controlling weeds, drought resistance and water retention in corn field applied by exotic green manure plants.%采取随机区组试验,根据农田杂草群落的生态学原理 ,运用生态学方法,通过玉米苜蓿间种与玉米清种相对照,探讨了间种抗旱植物苜蓿对玉米田杂草群落与生长发育的影响.结果表明:清种玉米田中稗草和红蓼的重要值较高,为优势种,间种苜蓿田中的优势种有红蓼、稗草、苘麻、反枝苋、龙葵、藜;在玉米各生育期,间种苜蓿田中的杂草生物量均低于清种玉米田处理,杂草株高大部分低于清种玉米处理;间种苜蓿穗长、穗行数、行粒数、穗重、穗粒重、百粒重和产量较清种玉米分别增加了6.6%、7.6%、2.2%、 12.28%、9.9%、7.8%和4.3%.认为间种苜蓿能够控制杂草数量,抑制杂草生物量增加,苜蓿

  17. Are invasive plants more competitive than native conspecifics? Patterns vary with competitors.

    Science.gov (United States)

    Zheng, Yulong; Feng, Yulong; Valiente-Banuet, Alfonso; Li, Yangping; Liao, Zhiyong; Zhang, Jiaolin; Chen, Yajun

    2015-10-22

    Invasive plants are sometimes considered to be more competitive than their native conspecifics, according to the prediction that the invader reallocates resources from defense to growth due to liberation of natural enemies ['Evolution of Increased Competitive Ability' (EICA) hypothesis]. However, the differences in competitive ability may depend on the identity of competitors. In order to test the effects of competitors, Ageratina adenophora plants from both native and invasive ranges competed directly, and competed with native residents from both invasive (China) and native (Mexico) ranges respectively. Invasive A. adenophora plants were more competitive than their conspecifics from native populations when competing with natives from China (interspecific competition), but not when competing with natives from Mexico. Invasive A. adenophora plants also showed higher competitive ability when grown in high-density monoculture communities of plants from the same population (intrapopulation competition). In contrast, invasive A. adenophora plants showed lower competitive ability when competing with plants from native populations (intraspecific competition). Our results indicated that in the invasive range A. adenophora has evolved to effectively cope with co-occurring natives and high density environments, contributing to invasion success. Here, we showed the significant effects of competitors, which should be considered carefully when testing the EICA hypothesis.

  18. Are invasive plants more competitive than native conspecifics? Patterns vary with competitors

    Science.gov (United States)

    Zheng, Yulong; Feng, Yulong; Valiente-Banuet, Alfonso; Li, Yangping; Liao, Zhiyong; Zhang, Jiaolin; Chen, Yajun

    2015-01-01

    Invasive plants are sometimes considered to be more competitive than their native conspecifics, according to the prediction that the invader reallocates resources from defense to growth due to liberation of natural enemies [‘Evolution of Increased Competitive Ability’ (EICA) hypothesis]. However, the differences in competitive ability may depend on the identity of competitors. In order to test the effects of competitors, Ageratina adenophora plants from both native and invasive ranges competed directly, and competed with native residents from both invasive (China) and native (Mexico) ranges respectively. Invasive A. adenophora plants were more competitive than their conspecifics from native populations when competing with natives from China (interspecific competition), but not when competing with natives from Mexico. Invasive A. adenophora plants also showed higher competitive ability when grown in high-density monoculture communities of plants from the same population (intrapopulation competition). In contrast, invasive A. adenophora plants showed lower competitive ability when competing with plants from native populations (intraspecific competition). Our results indicated that in the invasive range A. adenophora has evolved to effectively cope with co-occurring natives and high density environments, contributing to invasion success. Here, we showed the significant effects of competitors, which should be considered carefully when testing the EICA hypothesis. PMID:26489964

  19. Weed Dynamics during Transition to Conservation Agriculture in Western Kenya Maize Production.

    Science.gov (United States)

    Odhiambo, Judith A; Norton, Urszula; Ashilenje, Dennis; Omondi, Emmanuel C; Norton, Jay B

    2015-01-01

    Weed competition is a significant problem in maize (Zea mays, L.) production in Sub-Saharan Africa. Better understanding of weed management and costs in maize intercropped with beans (Phaseolus vulgaris, L.) during transition to conservation agricultural systems is needed. Changes in weed population and maize growth were assessed for a period of three years at Bungoma where crops are grown twice per year and at Trans-Nzoia where crops are grown once per year. Treatments included three tillage practices: minimum (MT), no-till (NT) and conventional (CT) applied to three cropping systems: continuous maize/bean intercropping (TYPICAL), maize/bean intercropping with relayed mucuna after bean harvest (RELAY) and maize, bean and mucuna planted in a strip intercropping arrangement (STRIP). Herbicides were used in NT, shallow hand hoeing and herbicides were used in MT and deep hoeing with no herbicides were used in CT. Weed and maize performance in the maize phase of each cropping system were assessed at both locations and costs of weed control were estimated at Manor House only. Weed density of grass and forb species declined significantly under MT and NT at Manor House and of grass species only at Mabanga. The greatest declines of more than 50% were observed as early as within one year of the transition to MT and NT in STRIP and TYPICAL cropping systems at Manor House. Transitioning to conservation based systems resulted in a decline of four out of five most dominant weed species. At the same time, no negative impact of MT or NT on maize growth was observed. Corresponding costs of weed management were reduced by $148.40 ha(-1) in MT and $149.60 ha(-1) in NT compared with CT. In conclusion, farmers can benefit from effective and less expensive weed management alternatives early in the process of transitioning to reduced tillage operations.

  20. Weed Dynamics during Transition to Conservation Agriculture in Western Kenya Maize Production.

    Directory of Open Access Journals (Sweden)

    Judith A Odhiambo

    Full Text Available Weed competition is a significant problem in maize (Zea mays, L. production in Sub-Saharan Africa. Better understanding of weed management and costs in maize intercropped with beans (Phaseolus vulgaris, L. during transition to conservation agricultural systems is needed. Changes in weed population and maize growth were assessed for a period of three years at Bungoma where crops are grown twice per year and at Trans-Nzoia where crops are grown once per year. Treatments included three tillage practices: minimum (MT, no-till (NT and conventional (CT applied to three cropping systems: continuous maize/bean intercropping (TYPICAL, maize/bean intercropping with relayed mucuna after bean harvest (RELAY and maize, bean and mucuna planted in a strip intercropping arrangement (STRIP. Herbicides were used in NT, shallow hand hoeing and herbicides were used in MT and deep hoeing with no herbicides were used in CT. Weed and maize performance in the maize phase of each cropping system were assessed at both locations and costs of weed control were estimated at Manor House only. Weed density of grass and forb species declined significantly under MT and NT at Manor House and of grass species only at Mabanga. The greatest declines of more than 50% were observed as early as within one year of the transition to MT and NT in STRIP and TYPICAL cropping systems at Manor House. Transitioning to conservation based systems resulted in a decline of four out of five most dominant weed species. At the same time, no negative impact of MT or NT on maize growth was observed. Corresponding costs of weed management were reduced by $148.40 ha(-1 in MT and $149.60 ha(-1 in NT compared with CT. In conclusion, farmers can benefit from effective and less expensive weed management alternatives early in the process of transitioning to reduced tillage operations.

  1. 7 CFR 360.200 - Designation of noxious weeds.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 5 2010-01-01 2010-01-01 false Designation of noxious weeds. 360.200 Section 360.200... SERVICE, DEPARTMENT OF AGRICULTURE NOXIOUS WEED REGULATIONS § 360.200 Designation of noxious weeds. As... determined that the following plants 1 or plant products fall within the definition of “noxious weed” as...

  2. Plantas cultivadas e invasoras como habitat para predadores do gênero Orius(Wolff (Heteroptera: anthocoridae Crops and weeds as host plants Orius species (Heteroptera: anthocoridae

    Directory of Open Access Journals (Sweden)

    Luís Cláudio Paterno Silveira

    2003-01-01

    Full Text Available O objetivo deste trabalho foi registrar as espécies de Orius associadas a plantas cultivadas e invasoras presentes em uma localidade de Minas Gerais e três de São Paulo, nos anos de 1999 e 2000. As coletas foram realizadas através de batidas das plantas no interior de sacos plásticos para desalojar os insetos. Posteriormente, as espécies foram separadas em laboratório. O predador Orius insidiosus (Say foi coletado nas culturas de milho (Zea mays L., milheto (Pennisetum glaucum (L. R.Br., sorgo (Sorghum spp., feijão (Phaseolus vulgaris L., girassol (Helianthus annuus L., alfafa (Medicago sativa L., soja [Glycine max (L. Merr.], crisântemo (Chrysanthemum spp., tango (Solidago canadensis L. e cartamus (Carthamus tinctorius L. e nas plantas invasoras picão-preto (Bidens pilosa L., caruru (Amaranthus sp., losna-branca (Parthenium hysterophorus L. e apaga-fogo (Alternanthera ficoidea L.. Orius thyestes Herring foi encontrado nas plantas invasoras picão-preto, caruru e apaga-fogo. Orius perpunctatus (Reuter e Orius sp. foram coletados principalmente nas plantas invasoras picão-preto, caruru e apaga-fogo e no milho. Constatou-se que muitas dessas plantas são reservatórios naturais para esses predadores, em termos de habitat, abrigo, presas e pólen.The aim of this research was to record the Orius species present on some crops and weeds in areas located in the southeast region in Brazil, during 1999 and 2000. The insect collections were made through the tapping method to dislodge the insects from the plant into a plastic bag. The identifications of the specimens was done in the laboratory. Orius insidiosus (Say was collected on the following crops: corn (Zea mays L., pearl millet (Pennisetum glaucum (L. R.Br., sorghum (Sorghum spp., bean (Phaseolus vulgaris L., sunflower (Helianthus annuus L., alfalfa (Medicago sativa L., soybean (Glycine max (L. Merr., chrysanthemum (Chrysanthemum spp., tango (Solidago canadensis L. and carthamus

  3. Competition Between Plant Populations with Different Rooting Depths I. Theoretical Considerations

    NARCIS (Netherlands)

    Berendse, Frank

    1979-01-01

    As an extension of De Wit’s competition theory a theoretical description has been developed of competition between plant populations with different rooting depths. This model shows that in mixtures of plants with different rooting depths the value of the Relative Yield Total can be expected to excee

  4. Competition between Plant-Populations with Different Rooting Depths. 1. Theoretical Considerations

    NARCIS (Netherlands)

    Berendse, F.

    1979-01-01

    As an extension of De Wit's competition theory a theoretical description has been developed of competition between plant populations with different rooting depths. This model shows that in mixtures of plants with different rooting depths the value of the Relative Yield Total can be expected to excee

  5. A STUDY ON WEED CONTROL IN SOYBEAN

    Directory of Open Access Journals (Sweden)

    S. TJITROSEMITO

    1991-01-01

    Full Text Available Two field experiments on weed control in soybeans were carried out at BIOTROP, Bogor, Indonesia from February to June, 1989. The critical period for weed control was found to be between 20 - 40 days after planting of soybean (c. v. Wilis grown at a planting distance of 40 x 10 cm. It did not coincide with the fastest growth in terms of trifoliate leaf number. Further studies were suggested to understand the physiological growth of soybean related to weed control. Pendimethalin at 660- 1320 g a.e./ha applied one day after sowing did not cause any phytotoxic effect to soybean and had good weed control performance.

  6. Research methods in weed science: herbicide absorption and translocation in plants using radioisotopes

    Science.gov (United States)

    Herbicide absorption and translocation in plants is a key component in the study of herbicide physiology, mode of action, selectivity, resistance mechanisms, and in the registration process. Radioactive herbicides have been in use for over half-a-century in the research and study of herbicide absorp...

  7. Efeitos dos períodos de competição do mato na cultura do amendoim: II. Safra das águas Effects of weed competition periods on peanut: II. Wet season crop

    Directory of Open Access Journals (Sweden)

    EDISON MARTINS PAULO

    2001-01-01

    Full Text Available O presente trabalho foi realizado na safra das águas de 1989, no Núcleo de Agronomia da Alta Paulista, em Adamantina (SP para estudar o efeito de diferentes períodos de competição do mato no amendoim. Adotou-se o delineamento estatístico de blocos ao acaso, com quatro repetições e 22 tratamentos. Os tratamentos resultaram da combinação da presença e da ausência do mato a partir do início da cultura, com as seguintes épocas de remoção da flora infestante: 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 e 100 dias após a semeadura. As parcelas foram constituídas por quatro linhas de amendoim, perfazendo 6 m² de área útil. As principais plantas daninhas encontradas na área experimental foram: Cyperus lanceolatus Poir, Commelina benghalensis L., Brachiaria decumbens Stapf., Amaranthus viridis L., Eleusine indica (L. Gaertn., Portulaca oleracea L., Digitaria horizontalis Willd. e Solanum americanum Mill. A convivência do mato diminuiu a produção de vagens, de grãos e a população do amendoim na colheita. Não se observou efeito do mato sobre o rendimento de grãos e sobre a matéria seca acumulada pela parte aérea do amendoim. Capinas aplicadas aos 13 e 67 dias após a semeadura, respectivamente para os sistemas sem e com mato a partir da semeadura, foram suficientes para a obtenção de produção de vagens de amendoim estatisticamente igual à obtida pela cultura mantida sem competição, durante todo o ciclo. Os componentes da produção do amendoim foram favorecidos com a aplicação do sistema sem mato, a partir do início da cultura.The present research was carried out at the Núcleo de Agronomia da Alta Paulista, in Adamantina, State of Sao Paulo, Brazil, to study the effects of different periods of weed competition with peanut.The treatments were all possible combinations among the presence/absence of weeds (at the sowing time and the following periods of weed removal: 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 days

  8. Competition and facilitation in multispecies plant-herbivore systems of productive environments

    NARCIS (Netherlands)

    Huisman, Jef; Olff, Han

    1998-01-01

    We develop a multispecies plant-herbivore model to explore how plant competition for light and the selectivity of herbivores affect abundance patterns of plants and herbivores along productivity gradients. The model considers a small and a tall plant species, a generalist herbivore, and a selective

  9. Green Weeding

    Science.gov (United States)

    Penniman, Sarah; McColl, Lisa

    2008-01-01

    Gone are the days of tiptoeing to the dumpsters with boxes of weeded books in tow. Lots of libraries are now taking advantage of the many low-cost services and solutions that promise to help extend the lives of collection discards. Some of these options can be very profitable. Some create goodwill within the local community. Some may seem more…

  10. Competition

    NARCIS (Netherlands)

    Boone, J.

    2000-01-01

    Competition has been modelled in the literature in a number of ways.What do these different parametrizations of competition have in common?For instance, it turns out that it is not always the case that a rise in competition reduces price cost margins, industry wide profits or concentration.All param

  11. Intraspecific competition facilitates the evolution of tolerance to insect damage in the perennial plant Solanum carolinense.

    Science.gov (United States)

    McNutt, David W; Halpern, Stacey L; Barrows, Kahaili; Underwood, Nora

    2012-12-01

    Tolerance to herbivory (the degree to which plants maintain fitness after damage) is a key component of plant defense, so understanding how natural selection and evolutionary constraints act on tolerance traits is important to general theories of plant-herbivore interactions. These factors may be affected by plant competition, which often interacts with damage to influence trait expression and fitness. However, few studies have manipulated competitor density to examine the evolutionary effects of competition on tolerance. In this study, we tested whether intraspecific competition affects four aspects of the evolution of tolerance to herbivory in the perennial plant Solanum carolinense: phenotypic expression, expression of genetic variation, the adaptive value of tolerance, and costs of tolerance. We manipulated insect damage and intraspecific competition for clonal lines of S. carolinense in a greenhouse experiment, and measured tolerance in terms of sexual and asexual fitness components. Compared to plants growing at low density, plants growing at high density had greater expression of and genetic variation in tolerance, and experienced greater fitness benefits from tolerance when damaged. Tolerance was not costly for plants growing at either density, and only plants growing at low density benefited from tolerance when undamaged, perhaps due to greater intrinsic growth rates of more tolerant genotypes. These results suggest that competition is likely to facilitate the evolution of tolerance in S. carolinense, and perhaps in other plants that regularly experience competition, while spatio-temporal variation in density may maintain genetic variation in tolerance.

  12. Reproduction of Pratylenchus zeae on Weeds

    OpenAIRE

    BELLÉ,C.; KASPARY, T. E.; KUHN,P.R.; Schmitt, J.; LIMA-MEDINA, I.

    2017-01-01

    ABSTRACT Weeds can be hosts of root-lesion nematode (Pratylenchus spp.), maintaining or increasing their population in the soil. The objective of this study was to evaluate the reaction of 25 weeds species to the nematode Pratylenchus zeae. The weed plants were individually inoculated with 1,000 individuals of P. zeae and maintained in a greenhouse for 90 days. After this period, eggs and nematodes were extracted, quantified, and the reproduction factor (RF = final population/initial populati...

  13. Agronomic evaluation of cowpea as a function of weed control with herbicides and different combinations

    Directory of Open Access Journals (Sweden)

    Wando Wilson de Oliveira Souza

    2016-12-01

    Full Text Available ABSTRACT Cultivation of the cowpea is important in various regions of Brazil, but competition from weeds is one of the factors which limit productivity. The aim of this study therefore was to evaluate the pre-plant selectivity and efficiency of different herbicides, and combinations of herbicides, in the cowpea [Vigna unguiculata (L. Walp.]. An experiment was carried out in a randomised block design, in lots split over time and with three replications, using a 4 x 7 factorial scheme, where the treatments consisted of: glyphosate, glyphosate + imazethapyr, glyphosate + flumioxazin, glyphosate + imazethapyr + flumioxazin, glyphosate + ready mix (imazethapyr & flumioxazin, and two control treatments (one with no weeding and one with manual weeding. The treatments were evaluated in combination with four different sowing times, i.e. immediately after application of the herbicides, and at five, ten and fifteen days after application (DAA. The combination of glyphosate + flumioxazin at 15 DAA, gave the highest mean productivity, 1,105.32 kg ha-1, followed by manual weeding with 1,027.37 kg ha-1. The herbicide mixtures of glyphosate + imazethapyr + flumioxazin caused phyto-toxicity in the cowpea crop, limiting the production components. The best strategies for weed control in this crop are manual weeding with seeding at 10 DAA, as well as the application of a glyphosate + flumioxazin mixture with seeding at 15 DAA.

  14. A comprehensive test of evolutionarily increased competitive ability in a highly invasive plant species.

    Science.gov (United States)

    Joshi, Srijana; Gruntman, Michal; Bilton, Mark; Seifan, Merav; Tielbörger, Katja

    2014-12-01

    A common hypothesis to explain plants' invasive success is that release from natural enemies in the introduced range selects for reduced allocation to resistance traits and a subsequent increase in resources available for growth and competitive ability (evolution of increased competitive ability, EICA). However, studies that have investigated this hypothesis have been incomplete as they either did not test for all aspects of competitive ability or did not select appropriate competitors. Here, the prediction of increased competitive ability was examined with the invasive plant Lythrum salicaria (purple loosestrife) in a set of common-garden experiments that addressed these aspects by carefully distinguishing between competitive effect and response of invasive and native plants, and by using both intraspecific and interspecific competition settings with a highly vigorous neighbour, Urtica dioica (stinging nettle), which occurs in both ranges. While the intraspecific competition results showed no differences in competitive effect or response between native and invasive plants, the interspecific competition experiment revealed greater competitive response and effect of invasive plants in both biomass and seed production. The use of both intra- and interspecific competition experiments in this study revealed opposing results. While the first experiment refutes the EICA hypothesis, the second shows strong support for it, suggesting evolutionarily increased competitive ability in invasive populations of L. salicaria. It is suggested that the use of naturally co-occurring heterospecifics, rather than conspecifics, may provide a better evaluation of the possible evolutionary shift towards greater competitive ability. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. Diazotrophic diversity in the rhizosphere of two exotic weed plants, Prosopis juliflora and Parthenium hysterophorus.

    Science.gov (United States)

    Cibichakravarthy, B; Preetha, R; Sundaram, S P; Kumar, K; Balachandar, D

    2012-02-01

    This study is aimed at assessing culturable diazotrophic bacterial diversity in the rhizosphere of Prosopis juliflora and Parthenium hysterophorus, which grow profusely in nutritionally-poor soils and environmentally-stress conditions so as to identify some novel strains for bioinoculant technology. Diazotrophic isolates from Prosopis and Parthenium rhizosphere were characterized for nitrogenase activity by Acetylene Reduction Assay (ARA) and 16S rRNA gene sequencing. Further, the culture-independent quantitative PCR (qPCR) was performed to compare the abundance of diazotrophs in rhizosphere with bulk soils. The proportion of diazotrophs in total heterotrophs was higher in rhizosphere than bulk soils and 32 putative diazotrophs from rhizosphere of two plants were identified by nifH gene amplification. The ARA activity of the isolates ranged from 40 to 95 nmol ethylene h(-1) mg protein(-1). The 16S rRNA gene analysis identified the isolates to be members of alpha, beta and gamma Proteobacteria and firmicutes. The qPCR assay also confirmed that abundance of nif gene in rhizosphere of these two plants was 10-fold higher than bulk soil.

  16. Effects of Elimination of Alligator Weed on Certain Aquatic Plants and the Value of these Plants as Waterfowl Foods

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The effects of elimination of alligatorweed by granular silvex on the abundance of 12 species of aquatic plants were studied on the Santee National Wildlife Refuge,...

  17. Evaluation of allelopathic impact of aqueous extract of root and aerial root of Tinospora cordifolia (Willd. miers on some weed plants

    Directory of Open Access Journals (Sweden)

    K. M. Abdul RAOOF

    2012-05-01

    Full Text Available The present laboratory experimental study was conducted to evaluate the allelopathic potential of Tinospora cordifolia (Willd. Miers on seed germination and seedling growth of weed plants (Chenopodium album L. Chenopodium murale L., Cassia tora L. and Cassia sophera L.. Root and aerial root aqueous extracts of Tinospora at 0.5, 1.0, 2.0 and 4.0% concentrations were applied to determine their effect on seed germination and seedling growth of test plants under laboratory conditions. Germination was observed for 15 days after that the root length and shoot length was measured. Dry weight was measured after oven drying the seedlings. The aqueous extracts from root and aerial root had inhibitory effect on seed germination of test plants. Aqueous extracts from root and aerial root significantly inhibited not only germination and seedling growth but also reduced dry weight of the seedlings. Root length, shoot length of weed species decreased progressively when plants were exposed to increasing concentration (0.5, 1, 2 and 4%. Aqueous extract of aerial root shows the least inhibition. The pH of aqueous extracts of different parts of T. cordifolia does not show any major change when the concentration increases.

  18. Effect of Plant Growth Promoting Bacteria Associated with Halophytic Weed (Psoralea corylifolia L) on Germination and Seedling Growth of Wheat Under Saline Conditions.

    Science.gov (United States)

    Sorty, Ajay M; Meena, Kamlesh K; Choudhary, Khushboo; Bitla, Utkarsh M; Minhas, P S; Krishnani, K K

    2016-11-01

    Halotolerant bacteria associated with Psoralea corylifolia L., a luxuriantly growing annual weed in salinity-affected semi-arid regions of western Maharashtra, India were evaluated for their plant growth-promoting activity in wheat. A total of 79 bacteria associated with different parts viz., root, shoot and nodule endophytes, rhizosphere, rhizoplane, and leaf epiphytes, were isolated and grouped based on their habitat. Twelve bacteria isolated for their potential in plant growth promotion were further selected for in vitro studies. Molecular identification showed the presence of the genera Bacillus, Pantoea, Marinobacterium, Acinetobacter, Enterobacter, Pseudomonas, Rhizobium, and Sinorhizobium (LC027447-53; LC027455; LC027457, LC027459, and LC128410). The phylogenetic studies along with carbon source utilization profiles using the Biolog® indicated the presence of novel species and the in planta studies revealed promising results under salinity stress. Whereas the nodule endophytes had minute plant growth-promoting (PGP) activity, the cell free culture filtrates of these strains enhanced seed germination of wheat (Triticum aestivum L). The maximum vigor index was monitored in isolate Y7 (Enterobacter sp strain NIASMVII). Indole acetic acid (IAA) production by the isolates ranged between 0.22 and 25.58 μg mL(-1). This signifies the need of exploration of their individual metabolites for developing next-generation bio-inoculants through co-inoculation with other compatible microbes. This study has potential in utilization of the weed-associated microbiome in terms of alleviation of salinity stress in crop plants.

  19. Understanding the impact of plant competition on the coupling between vegetation and the atmosphere

    Science.gov (United States)

    Loon, Marloes P.; Dekker, Stefan C.; Anten, Niels P. R.; Rietkerk, Max; Vilà-Guerau de Arellano, Jordi

    2015-11-01

    Competition between plants for resources is an important selective force. As a result competition through natural selection determines vegetation functioning and associated atmospheric interactions. Our aim was to investigate how the coupling between vegetation and atmosphere is influenced by plant competition. Though included in some coupled vegetation-atmosphere models, little attention has been paid to systematically study the impact of plant competition in determining the evolution of surface and atmospheric variables. We used a coupled vegetation-atmosphere model and included a new representation of plant competition. We compared the model results with diurnal data from Ameriflux Bondville site over a growing season. Including competition improved LAI (Leaf Area Index) and net ecosystem exchange of CO2 (NEE) predictions; if competition was not considered, there were strong deviations from observations. Remarkably, competition increased LAI while it reduced whole stand photosynthesis, resulting in a less negative NEE. Finally, independent of competition, latent heat flux, surface temperature, specific humidity, and atmospheric CO2 are well reproduced by the model. Only the sensible heat flux was overestimated, mainly due to the imbalance in the surface energy balance that can lead to lower measured sensible heat fluxes. Sensitivity analysis showed that the importance of plant competition on model outcomes increases with more nitrogen and water availability and may differ between soil types. We thus quantified the potential effect of plant competition in a coupled vegetation-atmosphere system and showed that it strongly influences this system, and therefore, we propose that competition should be considered in more vegetation-atmosphere models.

  20. 杂草科学管理——理论基础与实施途径%Scientific Management of Weed:Theory and Implementation

    Institute of Scientific and Technical Information of China (English)

    涂修亮; 陈英明

    2002-01-01

    Scientific management of weeds is theoretically based on ecology.The implementation methods inclade:Intensifying the weed biology and ecology research, especially those of the heavy weeds;Intensifying the research of developing competition between the crop and the weed;Utilizing a allelopathy the gene engineering and breeding against the weeds;Utilizing allelopathy between the crop and the weed, and utilizing biological and agricultural measurements to control the weeds.

  1. Competitive analysis of soybean and sudangrass using replacement series design

    Directory of Open Access Journals (Sweden)

    Mauro Antônio Rizzardi

    Full Text Available ABSTRACT Competition is the best known form of direct interference of weeds on agricultural crops. However, there is relatively little information on the competition of the weed sudangrass on soybean, which has been common in agricultural areas in the southern of Rio Grande do Sul. The objective of this study was to evaluate the competition between sudangrass and soybeans using replacement series experiments. The experiment was carried out in a greenhouse in a completely randomized design with four replications. The treatments consisted of soybean and sudangrass associations. The experimental units were 8-L plastic pots, in the proportions 0: 8, 2: 6, 4: 4, 6: 2, 8: 0, corresponding to 0, 25, 50, 75 and 100% of the crop and weed respectively. Shoot, root and total dry matter and plant height were analyzed through diagrams applied to replacement series and competitive indices. Soybean showed competitive superiority in coexistence with sudangrass in relation to shoot, root and total dry matter. The intraspecific competition was more significant for the crop and inter-specific competition was more important for the weed.

  2. Interagency partnering for weed prevention--progress on development of a National Early Detection and Rapid Response System for Invasive Plants in the United States

    Science.gov (United States)

    Westbrooks, R.; Westbrooks, R.

    2011-01-01

    Over the past 50 years, experience has shown that interagency groups provide an effective forum for addressing various invasive species issues and challenges on multiple land units. However, more importantly, they can also provide a coordinated framework for early detection, reporting, identification and vouchering, rapid assessment, and rapid response to new and emerging invasive plants in the United States. Interagency collaboration maximizes the use of available expertise, resources, and authority for promoting early detection and rapid response (EDRR) as the preferred management option for addressing new and emerging invasive plants. Currently, an interagency effort is underway to develop a National EDRR System for Invasive Plants in the United States. The proposed system will include structural and informational elements. Structural elements of the system include a network of interagency partner groups to facilitate early detection and rapid response to new invasive plants, including the Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW), State Invasive Species Councils, State Early Detection and Rapid Response Coordinating Committees, State Volunteer Detection and Reporting Networks, Invasive Plant Task Forces, and Cooperative Weed Management Areas. Informational elements and products being developed include Regional Invasive Plant Atlases, and EDRR Guidelines for EDRR Volunteer Network Training, Rapid Assessment and Rapid Response, and Criteria for Selection of EDRR Species. System science and technical support elements which are provided by cooperating state and federal scientists, include EDRR guidelines, training curriculum for EDRR volunteers and agency field personnel, plant identification and vouchering, rapid assessments, as well as predictive modeling and ecological range studies for invasive plant species.

  3. Image-based thresholds for weeds in maize fields

    DEFF Research Database (Denmark)

    Asif, Ali; Streibig, Jens Carl; Christensen, Svend

    2015-01-01

    Recent development of site-specific weed management strategies suggests patch application of herbicides to avoid their excessive use in crops. The estimation of infestation of weeds and control thresholds are important components for taking spray decisions. If weed pressure is below a certain level...... in some parts of the field and if late germinating weeds do not affect yield, it may not be necessary the spray such places from an economic point of view. Consequently, it makes sense to develop weed control thresholds for patch spraying, based on weed cover early in the growing season. In Danish maize...... field experiments conducted from 2010 to 2012, we estimated competitive ability parameters and control thresholds of naturally established weed populations in the context of decision-making for patch spraying. The most frequent weed was Chenopodium album, accompanied by Capsella bursa-pastoris, Cirsium...

  4. Developments in physical weed control in Northwest Europe

    Directory of Open Access Journals (Sweden)

    Riemens, Marieen

    2016-02-01

    Full Text Available In North West Europe there is an increasing need for advanced weed control methods. This paper gives an overview of the developments in physical weed control methods. Current innovations in interrow weeding focus on systems that take over the steering function of the driver in order to make them more precise and reduce crop losses. The latest developments in intrarow weeding techniques involve technologies that automatically detect and classify crop and weed plants and use this information to guide a weeding device. Several commercially available examples are presented.

  5. Competitive interactions between native and invasive exotic plant species are altered under elevated carbon dioxide.

    Science.gov (United States)

    Manea, Anthony; Leishman, Michelle R

    2011-03-01

    We hypothesized that the greater competitive ability of invasive exotic plants relative to native plants would increase under elevated CO(2) because they typically have traits that confer the ability for fast growth when resources are not limiting and thus are likely to be more responsive to elevated CO(2). A series of competition experiments under ambient and elevated CO(2) glasshouse conditions were conducted to determine an index of relative competition intensity for 14 native-invasive exotic species-pairs. Traits including specific leaf area, leaf mass ratio, leaf area ratio, relative growth rate, net assimilation rate and root weight ratio were measured. Competitive rankings within species-pairs were not affected by CO(2) concentration: invasive exotic species were more competitive in 9 of the 14 species-pairs and native species were more competitive in the remaining 5 species-pairs, regardless of CO(2) concentration. However, there was a significant interaction between plant type and CO(2) treatment due to reduced competitive response of native species under elevated compared with ambient CO(2) conditions. Native species had significantly lower specific leaf area and leaf area ratio under elevated compared with ambient CO(2). We also compared traits of more-competitive with less-competitive species, regardless of plant type, under both CO(2) treatments. More-competitive species had smaller leaf weight ratio and leaf area ratio, and larger relative growth rate and net assimilation rate under both ambient and elevated CO(2) conditions. These results suggest that growth and allocation traits can be useful predictors of the outcome of competitive interactions under both ambient and elevated CO(2) conditions. Under predicted future atmospheric CO(2) conditions, competitive rankings among species may not change substantially, but the relative success of invasive exotic species may be increased. Thus, under future atmospheric CO(2) conditions, the ecological and

  6. Competitive effects of non-native plants are lowest in native plant communities that are most vulnerable to invasion

    Science.gov (United States)

    J.Stephen Brewer; W. Chase Bailey

    2014-01-01

    Despite widespread acknowledgment that disturbance favors invasion, a hypothesis that has received little attention is whether non-native invaders have greater competitive effects on native plants in undisturbed habitats than in disturbed habitats. This hypothesis derives from the assumption that competitive interactions are more persistent in habitats that have not...

  7. Effect of Cultural Practices in Night on Weed Density and Weed Dry Matter

    Directory of Open Access Journals (Sweden)

    M.H Rashed Mohasel

    2011-01-01

    Full Text Available Abstract In order to evaluate the response of weed seeds to light, two experiments, at two different locations were conducted at Ferdowsi university of Mashhad in 2009. At the first experiment, field was ploughed in day and night. Weed density was evaluated 70 d after plough, with 1×1 quadrate. At the second experiment, at night treatment, ploughing, potato planting and weeding with cultivator were done at night. Weed sampling was done twice at 43 and 130 days after planting with 1×1 quadrate and weeds were identified and counted. Result showed pigweed (Amaranthus retroflexus L., sowthistle (Sonchus oleraceus L., crabgrass (Digitaria sanguinalis (L. scop, jimsonweed (Datura stramonium L. and mallow (Hibiscus trionum L. did not observed at night plough, in contrast, night plough has no significance influence on common lambsquarters (Chenopodium album L., and black nightshade (Solanum nigrum L.. Only common lambsquarters had similar appearance in two treatments, indicating insusceptibility of this weed to time of plough. Interestingly, at the second experiment, result was very similar. Potato yield was higher at night treatment, but not significant. This research showed that some cultural practice like plough, planting and weeding with cultivator in night can reduce weed density and weed dry matter. Keywords: Germination, Time of plough, Sustainable weeds management, Light

  8. Competition.

    Science.gov (United States)

    Chambers, D W

    1997-01-01

    Our ambivalence toward competition can be traced to an unspoken preference for certain types of competition which give us an advantage over the types we value less. Four types are defined (a) pure (same rules, same objectives), (b) collaborative (same rules, shared objective), (c) market share (different rules, same objectives), and (d) market growth (different rules, value added orientation). The defining characteristics of the four types of competition are respectively: needing a referee, arguing over the spoils, differentiation and substitutability, and customer focus. Dentistry has features of all four types of competition, thus making it difficult to have a meaningful discussion or frame a coherent policy on this topic.

  9. Water management as a key component of integrated weed management

    Directory of Open Access Journals (Sweden)

    Giuseppe Zanin

    2011-02-01

    Full Text Available Water management within the cropping system is a key factor for an integrated weed management. Soil moisture affects seed persistence and seed dormancy, thus influencing their germination, the establishment of seedlings as well as the competition at adult stage and the number, vitality and dormancy of the new seeds produced by the weeds. The interactions among water availability and competition are very complex and still not fully understood. A research effort in this sector should the be very relevant for the development of new approaches of weed management, such as “Ecological weed management”, aiming to reduce weed density and competitiveness and, in the medium term, to prevent undesired modifications of the weed flora.

  10. The effect of competition from neighbours on stomatal conductance in lettuce and tomato plants.

    Science.gov (United States)

    Vysotskaya, Lidiya; Wilkinson, Sally; Davies, William J; Arkhipova, Tatyana; Kudoyarova, Guzel

    2011-05-01

    Competition decreased transpiration from young lettuce plants after 2 days, before any reductions in leaf area became apparent, and stomatal conductance (g(s) ) of lettuce and tomato plants was also reduced. Stomatal closure was not due to hydraulic signals or competition for nutrients, as soil water content, leaf water status and leaf nitrate concentrations were unaffected by neighbours. Competition-induced stomatal closure was absent in an abscisic acid (ABA)-deficient tomato mutant, flacca, indicating a fundamental involvement of ABA. Although tomato xylem sap ABA concentrations were unaffected by the presence of neighbours, ABA/pH-based stomatal modulation is still likely to underlie the response to competition, as soil and xylem sap alkalization was observed in competing plants. Competition also modulated leaf ethylene production, and treatment of lettuce plants with an ethylene perception inhibitor (1-methylcyclopropene) diminished the difference in g(s) between single and competing plants grown in a controlled environment room, but increased it in plants grown in the greenhouse: ethylene altered the extent of the stomatal response to competition. Effects of competition on g(s) are discussed in terms of the detection of the absence of neighbours: increases in g(s) and carbon fixation may allow faster initial space occupancy within an emerging community/crop.

  11. Evaluation of empirical models and competition indices in ranking canola

    Directory of Open Access Journals (Sweden)

    A. S Safahani

    2012-06-01

    Full Text Available In order to evaluate the competitive ability (CA of canola cultivars against wild mustard, two experiments were conducted at the Gorgan Institute in Iran during the 2005-2007 cropping seasons. The experimental factors were canola cultivars (1st year: Zarfam, Option500, Hayola330, Hayola401, Talayh, RGS003 and Sarigol; 2nd year: Zarfam, Hayola330, RGS003 and Option500 and weed density (1st year: control and 30 plants m-2; 2nd year: control, 4, 8 and 16 plants m-2. The result of the first year is experiment indicated that the grain yield and competitive indices differed significantly between the cultivars. Cultivar Zarfam showed a high ability to withstand competition (AWC = 47 %, high competitive indices (CI=1.79 and CI2 = 1.83 and low grain yield in the weed- free plots (1729 kg ha-1. The cultivar Option500, a less competitive cultivar had the lowest ability to withstand competition (AWC = 4 % and the lowest competitive indices (CI = 0.09 and CI2= 0.11 amongst the cultivars. However, the cultivar Option500 showed more grain yield in the weed- free plots (2333 kg ha-1 than cultivar Zarfam. In the second year of the experiment, the result of the yield loss models showed that the lowest and highest yield loss belonged to cultivars Zarfam and Option500 (50 and 95 % respectively. A comparison of different empirical models revealed that the empirical yield loss model based on weed relative leaf area was more reliable for predicting canola yield loss according to a high coefficient of determination (R2=0.99. The relative damage coefficient (q of the weed relative leaf area model showed that wild mustard was more competitive than canola (q>1.

  12. Do competitive interactions in dry heathlands explain plant abundance patterns and species coexistence?

    DEFF Research Database (Denmark)

    Ransijn, Johannes; Damgaard, Christian; Schmidt, Inger Kappel

    2015-01-01

    Plant community patterns in space and time may be explained by the interactions between competing plant species. The presented study investigates this in a nutrient and species poor ecosystem. The study presents a methodology for inferring competitive interactions from yearly vegetation inventories...... and uses this to assess the outcome of competitive interactions and to predict community patterns and dynamics in a Northwest-European dry heathland. Inferred competitive interactions from five consecutive years of measurements in permanent vegetation frames at a single dry heathland site were used...... to predict the community dynamics of C. vulgaris and D. flexuosa. This was compared with the observed plant community structure at 198 Danish dry heathland sites. Interspecific competition will most likely lead to competitive exclusion of D. flexuosa at the observed temporal and spatial scale...

  13. Weed detection in 3D images

    NARCIS (Netherlands)

    Piron, A.; Heijden, van der F.; Destain, M.F.

    2011-01-01

    Machine vision has been successfully used for mechanical destruction of weeds between rows of crops. Knowledge of the position of the rows where crops should be growing and the assumption that plants growing outside such positions are weeds may be used in such systems. However for many horticultural

  14. 75 FR 68945 - Update of Noxious Weed Regulations

    Science.gov (United States)

    2010-11-10

    ... Noxious Weed Regulations AGENCY: Animal and Plant Health Inspection Service, USDA. ACTION: Final rule... ] weeds by adding definitions of terms used in the regulations, adding details regarding the process of applying for the permits used to import or move noxious weeds, adding a requirement for the treatment of...

  15. The role of arable weed seeds for agroecosystem functioning

    NARCIS (Netherlands)

    Franke, A.C.; Lotz, L.A.P.; Burg, van der W.J.; Overbeek, van L.S.

    2009-01-01

    A literature study was conducted to gather knowledge on the impact of weed seeds on agroecosystem functioning other than effects related to the production of weed seedlings and plants. The results of the review suggested that a larger and more diverse weed seedbank can contribute to the biodiversity

  16. Competition

    NARCIS (Netherlands)

    F. Bridoux

    2014-01-01

    Competition traditionally refers to the actions that firms take in a product market to outperform rivals in attracting customers and generating revenues. Yet, competition extends beyond product markets to other arenas such as factor markets, where firms compete for resources, and the political arena

  17. Weed flora of South Africa 1: major groupings

    Directory of Open Access Journals (Sweden)

    M. J. Wells

    1983-12-01

    Full Text Available Whilst attention has been focussed on combating priority weeds we have neglected to obtain an overall picture of our weed flora. To rectify the position a National Weed List has been compiled, the weeds have been classified and an analysis made of the weed flora. Aspects covered in this paper are: major taxa, exotic and indigenous species and kinds of weeds. The presence of imbalances or power shifts between indigenous taxa is indicated by the fact that most weeds are supplied by a few families, and that Monocotyledon species are twice as likely to be weeds as are Dicotyledon species. The preponderance of Monocotyledon weeds is explained by re-invasion of cultivated and abandoned fields in grassland areas rather than by a shift towards Monocotyledon species in the veld. Exotic weeds contribute to imbalances via their greater versatility as well as by re-inforcing some taxa or kind of weed groupings at the expense of others. There is a power shift towards exotic Gymnosperms. Apart from flora weeds, exotics provide most agrestals, lawn weeds and weeds of planted pastures, and nearly as many ruderals as the indigenous species.

  18. WEED SURVEYING OF PHACELIA (PHACELIA TANACETIFOLIA L.) AND EVALUATING THE EFFICIENCY OF THE WEED CONTROL.

    Science.gov (United States)

    Horváth, E; Szabó, R

    2014-01-01

    The experiment was set up in an area of 9 ha that was split into 4 plots: in plot 1 the row spacing was 12 cm and the seeding rate was 10 kg; in plot 2 the row spacing was 24 cm and the seeding rate was 10 kg; in plot 3 the row spacing was 24 cm and the seeding rate was 8 kg; in plot 4 the row spacing was 12 cm and the seeding rate was 8 kg. After the weed surveying, the total weed coverage was established as follows: in plot 1 the total weed coverage was 11.34%, in plot 2 it was 12.3%, in plot 3 it was 18%, and in plot 4 the total weed coverage was 15%. Based on the weed survey, on the test area the following dicotyledon weeds belonging to the T4 Raunkiaer plant life-form category occupied the highest percentage: heal-all, black-bindweed, goosefoot. The proportion of the perennial dicotyledons: field bindweed (G3), tuberous pea (G1), white campion (H3) was negligible. In all four cases the weed control was executed using the same herbicide in the same doses and with regard to the weed species it showed the same level of efficiency. The smaller row spacing and higher seeding rate has a beneficial effect on the weed suppressing capacity of the crop, the crop's weed suppressing capacity is better and the development of the weeds becomes worse.

  19. Competição entre plantas com ênfase no recurso luz Competition among plants for the light recourse

    Directory of Open Access Journals (Sweden)

    Carlos Renato Tavares de Castro

    1996-04-01

    -especific competition is responsible for the reduction of productivity in many crops. This reduce the diversification of the intercropping and requiring intensive care in the weeds control. The change in the light intensity and quality impose by the higher crop in the intercropping is a selection factor in the species that can develop under this condition. Better use and utilization of the solar radiation, of the vertical and horizontal space, better nutrient cycling, and improvement of the soil structure are great intercropping advantages. Several researchers consider light competition, due to interference of the plant upper part, more important and complex than the substrato competition. Some species react to light competition by activation of complex mechanisms and by adaptation to the new light status. This gives to these species a great capacity of adaptation. Nowadays, one of the biggest challenge to the researchers is the development of intercropping techniques to increase the positive interaction among crops reducing, consequently, the competition. Thus, if is primordial the understanding of the competition processes involved and this article presents a briefreview about them.

  20. Allelopathy and resource competition: the effects of Phragmites australis invasion in plant communities.

    Science.gov (United States)

    Uddin, Md Nazim; Robinson, Randall William

    2017-12-01

    Phragmites australis, a ubiquitous wetland plant, has been considered one of the most invasive species in the world. Allelopathy appears to be one of the invasion mechanisms, however, the effects could be masked by resource competition among target plants. The difficulty of distinguishing allelopathy from resource competition among plants has hindered investigations of the role of phytotoxic allelochemicals in plant communities. This has been addressed via experiments conducted in both the greenhouse and laboratory by growing associated plants, Melaleuca ericifolia, Rumex conglomeratus, and model plant, Lactuca sativa at varying densities with the allelopathic plant, P. australis, its litter and leachate of P. australis litter. This study investigated the potential interacting influences of allelopathy and resource competition on plant growth-density relationships. In greenhouse, the root exudates mediated effects showed the strongest growth inhibition of M. ericifolia at high density whereas litter mediated results revealed increased growth at medium density treatments compared to low and high density. Again, laboratory experiments related to seed germination and seedling growth of L. sativa and R. conglomeratus exhibited phytotoxicity decreased showing positive growth as plant density increased and vice versa. Overall, the differential effects were observed among experiments but maximum individual plant biomass and some other positive effects on plant traits such as root and shoot length, chlorophyll content occurred at an intermediate density. This was attributed to the sharing of the available phytotoxin among plants at high densities which is compatible to density-dependent phytotoxicity model. The results demonstrated that plant-plant interference is the combined effect of allelopathy and resource competition with many other factors but this experimental design, target-neighbor mixed-culture in combination of plant grown at varying densities with varying

  1. Spatial heterogeneity of plant-soil feedback affects root interactions and interspecific competition.

    Science.gov (United States)

    Hendriks, Marloes; Ravenek, Janneke M; Smit-Tiekstra, Annemiek E; van der Paauw, Jan Willem; de Caluwe, Hannie; van der Putten, Wim H; de Kroon, Hans; Mommer, Liesje

    2015-08-01

    Plant-soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant-soil feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species. We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of 'own' and 'foreign' soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR. All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment. We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands.

  2. Competitive capabilities among manufacturing plants in developing, emerging, and industrialized countries : A comparative analysis

    NARCIS (Netherlands)

    Schoenherr, T.; Power, D.; Narasimhan, R.; Samson, D.

    2012-01-01

    Competitive capabilities have been defined as a plant's actual performance relative to its competitors, with the most commonly investigated capabilities being quality, delivery, flexibility, and cost. However, most research in this realm has investigated capabilities within developed countries, and

  3. Importance of herbicide resistance in weeds of natural areas

    OpenAIRE

    DiTomaso, Joseph

    2014-01-01

    Worldwide, the majority of the plant species that are developing herbicide resistance are those that occur as weeds in agricultural environments, on roadsides and in other rights-of-way. In contrast, herbicide resistance is not nearly so common in weeds of natural areas or rangelands. A search of the International Survey of Herbicide Resistant Weeds ( weedscience.com ) revealed no herbicide-resistant weeds (i.e., invasive nonnative species) listed for terrestrial natural areas anywhere in the...

  4. The sensitizing capacity of Compositae plants. VI. Guinea pig sensitization experiments with ornamental plants and weeds using different methods.

    Science.gov (United States)

    Zeller, W; de Gols, M; Hausen, B M

    1985-01-01

    Experimental studies in guinea pigs using ether extracts of 20 different species of the Compositae plant family were carried out with the open epicutaneous method (OET) and the guinea pig maximization test (GPMT). The results demonstrate that Cnicus benedictus (blessed thistle), Chrysanthemum leucanthemum (marguerite, ox-eye daisy) and Helianthus debilis (dwarf sunflower) are strong sensitizers while Helenium amarum (bitterweed), Gaillardia amblyodon (blanket flower), Artemisia ludoviciana (prairie sage), Ambrosia trifida (giant ragweed) and Solidago virgaurea (goldenrod) are medium sensitizers. Twelfe species revealed only a weak or no sensitizing capacity; among those were corn flower, wormwood, mugwort, coltsfoot and dandelion. Cross-reactivities were observed in a considerable number of the investigated plant species. The sensitizing power as well as the observed cross-reactions depend on the occurrence of sesquiterpene lactones which have an alpha-methylene group exocyclic to the lactone in common ("immunologic requisite"). As a practical consequence, patients suffering from allergic contact dermatitis due to Compositae species are strictly requested to avoid contact with the offending species and all related species to prevent recurrences of their skin lesions.

  5. Robotic weeding and automated weed measurements

    DEFF Research Database (Denmark)

    Christensen, S.; Søgaard, H.T.; Jørgensen, R.N.

    2003-01-01

    The goal of decreasing herbicide usage has so far focused on reducing the herbicide dosage or replacing chemical weed control by hoeing and harrowing. The conventional weed control strategy is to apply the same dose of herbicide or the same intensity of hoeing and harrowing in the whole field....... The strategy may be changed in the coming years because experiments in Germany, USA, Australia, and Denmark have shown that site-specific weed management can reduce herbicide usage significantly. One of the promising technologies for site specific weed management is robotic weeding. This paper reviews...... the state-of-the-art of automated weed measurement methods and the research projects concerning autonomous platform and information system for crop and weed monitoring and robotic weeding....

  6. A rotação de cultura reduz a matocompetição e aumenta o teor de clorofila e a produtividade do arroz Crop rotation reduces weed competition and increases chlorophyll concentration and yield of rice

    Directory of Open Access Journals (Sweden)

    Ricardo Antonio Marenco

    1999-10-01

    Full Text Available A rotação de culturas é uma prática importante em sistemas agrícolas sustentáveis pelos efeitos benéficos tanto na fertilidade do solo como na redução da matocompetição, entre outros. Este trabalho foi conduzido no campo experimental da UEMA, em São Luís, MA. Avaliou-se o efeito da rotação de culturas na incidência de plantas invasoras, nos teores de clorofila e na produtividade do arroz (Oryza sativa L. cv. Guarani. Cultivou-se o arroz com e sem adubação nitrogenada, bem como em rotação com caupi (Vigna unguiculata (L. Walp., crotalária (Crotalaria paulina Schrank e mucuna (Mucuna aterrima Piper & Tracy. No primeiro ciclo a cobertura morta das leguminosas, deixada sobre o solo para a safra seguinte, foi máxima na crotalária, intermediária na mucuna e mínima no caupi. No segundo ciclo, cultivado em plantio direto sem uso de herbicidas, a rotação com mucuna e crotalária reduziu a biomassa, a cobertura e a densidade das invasoras. O teor de clorofila foi maior na rotação com crotalária do que na testemunha. A produtividade do arroz foi maior na rotação com crotalária e mucuna do que no arroz em cultivo sucessivo com ou sem N. Concluiu-se que a rotação do arroz com leguminosas aumenta a produtividade do arroz e reduz a matocompetição.Crop rotation is an essential practice in sustainable agricultural systems, because its effects on soil fertility and other benefits including reduction on weed competition. A field experiment was carried out at the UEMA experimental station, São Luís, Maranhão State, Brazil, to evaluate the effect of crop rotation on weed population, leaf chlorophyll concentration and yield of rice (Oryza sativa L. cv. Guarani. The rice was cultivated with and without N application, and in rotation with cowpea (Vigna unguiculata (L. Walp., hyacinthbean (Crotalaria paulina Schrank and velvetbean (Mucuna aterrima Piper & Tracy. First crop legume residues were highest in hyacinthbean, less in

  7. Eco-functional intensification by cereal-grain legume intercropping in organic farming systems for increased yields, reduced weeds and improved grain protein concentration

    DEFF Research Database (Denmark)

    Bedoussac, Laurent; Journet, Étienne-Pascal; Hauggaard-Nielsen, Henrik

    2014-01-01

    arable cropping, particularly in low-N input systems, to enhance: (i) yields because of a general improvement of environmental resource use; (ii) cereal grain protein concentration due to a non-proportional competition for soil mineral N and other plant growth factors; and (iii) weed control compared...

  8. Spatial vegetation patterns and neighborhood competition among woody plants in an East African savanna.

    Science.gov (United States)

    Dohn, Justin; Augustine, David J; Hanan, Niall P; Ratnam, Jayashree; Sankaran, Mahesh

    2017-02-01

    The majority of research on savanna vegetation dynamics has focused on the coexistence of woody and herbaceous vegetation. Interactions among woody plants in savannas are relatively poorly understood. We present data from a 10-yr longitudinal study of spatially explicit growth patterns of woody vegetation in an East African savanna following exclusion of large herbivores and in the absence of fire. We examined plant spatial patterns and quantified the degree of competition among woody individuals. Woody plants in this semiarid savanna exhibit strongly clumped spatial distributions at scales of 1-5 m. However, analysis of woody plant growth rates relative to their conspecific and heterospecific neighbors revealed evidence for strong competitive interactions at neighborhood scales of up to 5 m for most woody plant species. Thus, woody plants were aggregated in clumps despite significantly decreased growth rates in close proximity to neighbors, indicating that the spatial distribution of woody plants in this region depends on dispersal and establishment processes rather than on competitive, density-dependent mortality. However, our documentation of suppressive effects of woody plants on neighbors also suggests a potentially important role for tree-tree competition in controlling vegetation structure and indicates that the balanced-competition hypothesis may contribute to well-known patterns in maximum tree cover across rainfall gradients in Africa. © 2016 by the Ecological Society of America.

  9. The critical period of weed control in corn Zea mays at Mashhad, Iran

    Directory of Open Access Journals (Sweden)

    majid abaspoor

    2009-06-01

    Full Text Available In order to determine the critical period of weed control in corn, an experiment was conducted at Research Station, Faculty of Agriculture, Ferdowsi University of Mashhad in year 2000. The experiment consisted of two discrete periods, a weed-free and a weed infested period. The weed-free period consisted of removing all weeds till 4th (19 days after planting, 7th (34 days after planting, 11th (48 days after planting, 13th (52 days after planting, and 17th (59 days after planting, leaf growth stages and weed free check for growing season (123 days after planting, and the critical time of weed infested consisted of removing all weeds from fourth (19 days after planting, 7th (34 days after planting, 11th (48 days after planting, 13th (52 days after planting, and 17th (59 days after planting, leaf growth stages and weedy infested check for growing season. All treatments were compared in a randomized complete block design with four replications. The results showed that by prolonging weed-infested period, dry matter and leaf surface area of weeds per square meter were increased, but by increasing weed-infested period, weed density was decreased. The lowest weed density (23 weed plants per m2 was shown at infested all period of corn growing season. By passing the growing season, C4 weed species such as red root pigweed and barnyard grass were dominant compared with C3 weed species. At weed infested all period of corn growing season, red root pigweed had the highest dry matter (93% of all weeds dry matter and leaf surface area (86% of all weeds leaf surface compared with other weed species. At the first treatment of critical weed-free (19 days after planting the regrowth of weeds were substantial which resulted in decreasing growth of corn. Grain yield of corn were significantly higher at 52, 59 and 123 days after planting in weed free treatments compared with 48, 52, 59 and 123 days after planting in weed infested treatments. However, there were no

  10. Puertollano IGCC plant. Present position and future competitiveness

    Energy Technology Data Exchange (ETDEWEB)

    Pedro Casero; Francisco Garcia-Pena

    2006-07-01

    This paper discusses the current status of the Puertollano 350 MW IGCC demonstration power plant in Spain. The experience provided by the operation of this plant during the last years is described, focussing on the core systems of the plant (gasifier, gas cleaning and gas turbines). Bottlenecks and weak points related to these systems are identified, along with the improvements. The production of hydrogen from coal at an IGCC plant is also discussed. 9 figs., 2 tabs.

  11. Competition

    Institute of Scientific and Technical Information of China (English)

    吕思思

    2007-01-01

    <正> The term competition reminds me of asoul-stirring fight between a mother monkeyand a crocodile,The crocodile caught her babywhen the baby was drinking water in a pool,Inthe end,the mother got her baby,but herbaby’s body only,She lost her child forever,just for a mouthful of water.Such is competition,cruel and merciless,But if we see the other side of the coin,we’ll

  12. Integrating management techniques to restore sites invaded by mile-a-minute weed, Persicaria perfoliata

    Science.gov (United States)

    Ellen C. Lake; Judith Hough-Goldstein; Vincent. D' Amico

    2014-01-01

    Efforts to suppress an invasive weed are often undertaken with the goal of facilitating the recovery of a diverse native plant community. In some cases, however, reduction in the abundance of the target weed results in an increase in other exotic weeds. Mile-a-minute weed (Persicaria perfoliata (L.) H. Gross (Polygonaceae)) is an annual vine from...

  13. Lawn Weeds and Their Control. North Central Regional Extension Publication No. 26.

    Science.gov (United States)

    Purdue Univ., Lafayette, IN. Cooperative Extension Service.

    This publication discusses lawn weed control for the twelve state north central region of the country. Written for use by homeowners, the publication focuses on weed identification and proper herbicide selection and application. Identification of weeds and safe and appropriate herbicide use are emphasized. Forty-six weed and turf plants are…

  14. Lawn Weeds and Their Control. North Central Regional Extension Publication No. 26.

    Science.gov (United States)

    Purdue Univ., Lafayette, IN. Cooperative Extension Service.

    This publication discusses lawn weed control for the twelve state north central region of the country. Written for use by homeowners, the publication focuses on weed identification and proper herbicide selection and application. Identification of weeds and safe and appropriate herbicide use are emphasized. Forty-six weed and turf plants are…

  15. [Genetic and physiological compatibility of different forms of stem eelworms. VI. The crossing of eelworms from cultivated plants and weeds].

    Science.gov (United States)

    Ladygina, N M

    1978-01-01

    The crossing of stem eelworms of onion and red clover with these from Cirsium setosum and Taraxacum officinale resulted in the fertilization of females, egglaying and embriogenesis. However, the hybrid eggs died, as a rule. Only in one experiment a large population developed up to F5 but few hybrids survived to F10. The studied stem eelworms of weeds are genetically non-compatible with Ditylenchus dipsaci of onion and red clover and are distinct species.

  16. Plantas consideradas daninhas para culturas como fontes de néctar e pólen Plant species considered weeds as source of nectar and pollen

    Directory of Open Access Journals (Sweden)

    Mitzi Brandão

    1984-01-01

    Full Text Available São relacionadas 164 espécies de plantas consideradas danin has às culturas, no Estado de Minas Gerais, e que são produtoras de néctar e pólen. Essas plantas poderiam ser exploradas economicamente, visando o fornecimento de matéria prima a apicultura, e como fonte de alimento para os insetos polinizadores.There are related 164 species of weed plants of cultures in the state of Minas Gerais as source of nec tar and nectar and pollen. These plants could be used economically for the purpose of supply of raw material to the apiculture and as source of food for the pollination insects.

  17. Interactive effects of herbivory and competition intensity determine invasive plant performance.

    Science.gov (United States)

    Huang, Wei; Carrillo, Juli; Ding, Jianqing; Siemann, Evan

    2012-10-01

    Herbivory can reduce plant fitness, and its effects can be increased by competition. Though numerous studies have examined the joint effects of herbivores and competitors on plant performance, these interactive effects are seldom considered in the context of plant invasions. Here, we examined variation in plant performance within a competitive environment in response to both specialist and generalist herbivores using Chinese tallow as a model species. We combined tallow plants from native and invasive populations to form all possible pairwise combinations, and designated invasive populations as stronger neighbours and native populations as weaker neighbours. We found that when no herbivory was imposed, invasive populations always had higher total biomass than natives, regardless of their neighbours, which is consistent with our assumption of increased competitive ability. Defoliation by either generalist or specialist herbivores suppressed plant growth but the effects of specialists were generally stronger for invasive populations. Invasive populations had their lowest biomass when fed upon by specialists while simultaneously competing with stronger neighbours. The root/shoot ratios of invasive populations were lower than those of native populations under almost all conditions, and invasive plants were taller than native plants overall, especially when herbivores were present, suggesting that invasive populations may adopt an "aboveground first" strategy to cope with herbivory and competition. These results suggest that release from herbivores, especially specialists, improves an invader's performance and helps to increase its competitive ability. Therefore, increasing interspecific competition intensity by planting a stronger neighbour while simultaneously releasing a specialist herbivore may be an especially effective method of managing invasive plants.

  18. Weed suppression and yield of thirteen spring wheat (Triticum aestivum L. varieties grown in an organic system

    Directory of Open Access Journals (Sweden)

    Beata Feledyn-Szewczyk

    2017-09-01

    Full Text Available The aim of this study was to determine the relationships between morphological features, canopy parameters, weed infestation, and grain yield of spring wheat varieties. The study was conducted in the period 2011–2013, on fields managed organically at the Experimental Station of The Institute of Soil Science and Plant Cultivation – State Research Institute, Osiny, Poland. Thirteen spring wheat varieties were sown in a randomized complete block design with four replications. Weed density and dry matter production were estimated as well biometric features of the wheat varieties at tillering (BBCH 22–24 and dough (BBCH 85–87 stages. The analyses of variance showed that the year had a stronger effect than varieties on the level of weed infestation. Pearson’s correlation analysis indicated that weed number was influenced by the height of wheat plants and their aboveground biomass at the tillering stage and additionally by number of tillers at the dough stage. A significant correlation (r = −0.328, siginfficant at p < 0.05 was shown between the number of weeds and wheat grain yield. Different morphological features and canopy parameters influenced the competitive abilities of the spring wheat varieties tested. A cluster analysis detected one set of varieties with the largest (‘Bombona’, ‘Brawura’, ‘Hewilla’, ‘Kandela’, ‘Katoda’, ‘Łagwa’, and ‘Żura’ and another with the smallest (‘Monsun’, ‘Ostka Smolicka’, and ‘Parabola’ competitive abilities against weeds. The main outcome of the research is information for farmers as to which varieties are highly competitive against weeds and also high yielding. Among the varieties with the highest competitiveness, Triticum aestivum ‘Żura’ was the highest yielder (3.82 t ha−1 on average, whereas ‘Bombona’ yielded only at an average level (3.03 t ha−1. The suppressive ability of spring wheat varieties against weeds and yield potential should be both

  19. Interactive effect of herbivory and competition on the invasive plant Mikania micrantha.

    Science.gov (United States)

    Li, Junmin; Xiao, Tao; Zhang, Qiong; Dong, Ming

    2013-01-01

    A considerable number of host-specific biological control agents fail to control invasive plants in the field, and exploring the mechanism underlying this phenomenon is important and helpful for the management of invasive plants. Herbivory and competition are two of the most common biotic stressors encountered by invasive plants in their recipient communities. We predicted that the antagonistic interactive effect between herbivory and competition would weaken the effect of herbivory on invasive plants and result in the failure of herbivory to control invasive plants. To examine this prediction, thus, we conducted an experiment in which both invasive Mikania micrantha and native Coix lacryma-job i were grown together and subjected to herbivory-mimicking defoliation. Both defoliation and competition had significantly negative effects on the growth of the invader. However, the negative effect of 75% respective defoliation on the above- and below-ground biomass of Mikania micrantha was alleviated by presence of Coix lacryma-jobi. The negative effect of competition on the above- and below-ground biomass was equally compensated at 25%, 50% and 100% defoliation and overcompensated at 75% defoliation. The interactive effect was antagonistic and dependent on the defoliation intensity, with the maximum effect at 75% defoliation. The antagonistic interaction between defoliation and competition appears to be able to release the invader from competition, thus facilitating the invasiveness of Mikania, a situation that might make herbivory fail to inhibit the growth of invasive Mikania in the invaded community.

  20. 植物基因工程应用于杂草综合管理的新策略%New strategies of plant gene-engineering for integrated weed management

    Institute of Scientific and Technical Information of China (English)

    刘征; 毛雪; 郝转芳; 李润植

    2002-01-01

    The purpose of this paper was to outline the potential of plant gene-engineering to make new contributions in the general field of weed management.Different new strategies had been identified.These included the followings:① Breeding “suicide” weeds by transferring “terminator” or floral development inhibitor genes.② Decreasing weed competitiveness and fitness by inducing some “unfitness factors” which could spread throughout weed population.③ Engineering various bioherbicides (bacteria,fungi,viruses,insects and other pathogens,etc) to specifically colonize a target weed,killing it out-right or rendering it less fit.④ Improving crop competitiveness by introgression of favorable genes which would increase plant vigor and access to water,nutrients and light.⑤ Developing allelopathic crop cultivars with weed-suppressive potential through genetic manipulation.These strategies involved marker-assistant selection,map-based cloning,gene silencing and DNA Chip technology.%杂草与农作物竞争阳光、水分和营养物质,造成农作物减产;化学除草剂的过度使用引发了严重的生态后果;杂草还可能从近缘的转基因作物中获得某些抗性性状,转变成"超级杂草",这些都增加了杂草管理的难度及复杂性.近年来应用先进的分子生物学及基因工程技术,人们已分离出许多目的基因,如各种器官或组织特异性启动子、细胞毒素基因、可提高作物活力的优势基因及异株克生化合物生物合成途径的关键基因等.运用这些基因可建立杂草综合管理的新策略:①向作物中导入"终止因子"或开花抑制因子,当作物与近缘杂草杂交后,所形成的后代变成一种"自杀杂草"而不能存活;②控制某些性状的基因对作物是有益的或中性的,而对杂草是有害的,将这些杂草的"不适应因子"基因导入作物后,作物与杂草杂交产生的后代将缺乏竞争力和适应性,同时这

  1. Image analysis as a non-destructive method to assess regrowth of weeds after repeated flame weeding

    DEFF Research Database (Denmark)

    Rask, Anne Merete; Kristoffersen, Palle; Andreasen, Christian

    2013-01-01

    Efficient non-chemical weed control like flame weeding often requires repeated treatments. In weed control experiments the effect of each treatment may be estimated by removing and weighing the remaining weed biomass after the treatment, but the method influences the weed plants ability to regrow......, and therefore it may influence the long-term effect of repeated treatments. Visual assessment of weed cover or image analysis do not affect the remaining parts of the weed plants after treatment, but the methods may have other disadvantages. In order to evaluate and compare three methods we measured changes...... in vegetation cover of perennial ryegrass after flaming by (1) a simple image analysis programme counting green pixels, (2) visual assessment of images and (3) by taking biomass samples. Plants were flame treated with eight different dosages (0, 20, 30, 35, 45, 60, 90 and 180 kg propane ha-1) and with various...

  2. The Invasive American Weed Parthenium hysterophorus Can Negatively Impact Malaria Control in Africa.

    Directory of Open Access Journals (Sweden)

    Vincent O Nyasembe

    Full Text Available The direct negative effects of invasive plant species on agriculture and biodiversity are well known, but their indirect effects on human health, and particularly their interactions with disease-transmitting vectors, remains poorly explored. This study sought to investigate the impact of the invasive Neotropical weed Parthenium hysterophorus and its toxins on the survival and energy reserves of the malaria vector Anopheles gambiae. In this study, we compared the fitness of An. gambiae fed on three differentially attractive mosquito host plants and their major toxins; the highly aggressive invasive Neotropical weed Parthenium hysterophorus (Asteraceae in East Africa and two other adapted weeds, Ricinus communis (Euphorbiaceae and Bidens pilosa (Asteraceae. Our results showed that female An. gambiae fitness varied with host plants as females survived better and accumulated substantial energy reserves when fed on P. hysterophorus and R. communis compared to B. pilosa. Females tolerated parthenin and 1-phenylhepta-1, 3, 5-triyne, the toxins produced by P. hysterophorus and B. pilosa, respectively, but not ricinine produced by R. communis. Given that invasive plants like P. hysterophorus can suppress or even replace less competitive species that might be less suitable host-plants for arthropod disease vectors, the spread of invasive plants could lead to higher disease transmission. Parthenium hysterophorus represents a possible indirect effect of invasive plants on human health, which underpins the need to include an additional health dimension in risk-analysis modelling for invasive plants.

  3. An ultrasonic system for weed detection in cereal crops.

    Science.gov (United States)

    Andújar, Dionisio; Weis, Martin; Gerhards, Roland

    2012-12-13

    Site-specific weed management requires sensing of the actual weed infestation levels in agricultural fields to adapt the management accordingly. However, sophisticated sensor systems are not yet in wider practical use, since they are not easily available for the farmers and their handling as well as the management practice requires additional efforts. A new sensor-based weed detection method is presented in this paper and its applicability to cereal crops is evaluated. An ultrasonic distance sensor for the determination of plant heights was used for weed detection. It was hypothesised that the weed infested zones have a higher amount of biomass than non-infested areas and that this can be determined by plant height measurements. Ultrasonic distance measurements were taken in a winter wheat field infested by grass weeds and broad-leaved weeds. A total of 80 and 40 circular-shaped samples of different weed densities and compositions were assessed at two different dates. The sensor was pointed directly to the ground for height determination. In the following, weeds were counted and then removed from the sample locations. Grass weeds and broad-leaved weeds were separately removed. Differences between weed infested and weed-free measurements were determined. Dry-matter of weeds and crop was assessed and evaluated together with the sensor measurements. RGB images were taken prior and after weed removal to determine the coverage percentages of weeds and crop per sampling point. Image processing steps included EGI (excess green index) computation and thresholding to separate plants and background. The relationship between ultrasonic readings and the corresponding coverage of the crop and weeds were assessed using multiple regression analysis. Results revealed a height difference between infested and non-infested sample locations. Density and biomass of weeds present in the sample influenced the ultrasonic readings. The possibilities of weed group discrimination were

  4. An Ultrasonic System for Weed Detection in Cereal Crops

    Directory of Open Access Journals (Sweden)

    Dionisio Andújar

    2012-12-01

    Full Text Available Site-specific weed management requires sensing of the actual weed infestation levels in agricultural fields to adapt the management accordingly. However, sophisticated sensor systems are not yet in wider practical use, since they are not easily available for the farmers and their handling as well as the management practice requires additional efforts. A new sensor-based weed detection method is presented in this paper and its applicability to cereal crops is evaluated. An ultrasonic distance sensor for the determination of plant heights was used for weed detection. It was hypothesised that the weed infested zones have a higher amount of biomass than non-infested areas and that this can be determined by plant height measurements. Ultrasonic distance measurements were taken in a winter wheat field infested by grass weeds and broad-leaved weeds. A total of 80 and 40 circular-shaped samples of different weed densities and compositions were assessed at two different dates. The sensor was pointed directly to the ground for height determination. In the following, weeds were counted and then removed from the sample locations. Grass weeds and broad-leaved weeds were separately removed. Differences between weed infested and weed-free measurements were determined. Dry-matter of weeds and crop was assessed and evaluated together with the sensor measurements. RGB images were taken prior and after weed removal to determine the coverage percentages of weeds and crop per sampling point. Image processing steps included EGI (excess green index computation and thresholding to separate plants and background. The relationship between ultrasonic readings and the corresponding coverage of the crop and weeds were assessed using multiple regression analysis. Results revealed a height difference between infested and non-infested sample locations. Density and biomass of weeds present in the sample influenced the ultrasonic readings. The possibilities of weed group

  5. Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage.

    Science.gov (United States)

    Dodd, Antony N; Salathia, Neeraj; Hall, Anthony; Kévei, Eva; Tóth, Réka; Nagy, Ferenc; Hibberd, Julian M; Millar, Andrew J; Webb, Alex A R

    2005-07-22

    Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that of the external light-dark cycle. In wild type and in long- and short-circadian period mutants of Arabidopsis thaliana, plants with a clock period matched to the environment contain more chlorophyll, fix more carbon, grow faster, and survive better than plants with circadian periods differing from their environment. This explains why plants gain advantage from circadian control.

  6. Competition between Plant-Populations with Different Rooting Depths. 2. Pot Experiments

    NARCIS (Netherlands)

    Berendse, F.

    1981-01-01

    In a previous paper in this series a model was proposed lor the competition between plant populations with different rooting depths. This model predicts that in mixtures of plant populations with different rooting depths the Relative Yield Total will exceed unity. Secondly it predicts that in these

  7. Competition for light and nutrients in layered communities of aquatic plants

    NARCIS (Netherlands)

    Van Gerven, Luuk P.A.; de Klein, J.J.M; Gerla, Daan J.; Kooi, B.W.; Kuiper, Jan J.; Mooij, Wolf M.

    2015-01-01

    Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that at h

  8. Competition for light and nutrients in layered communities of aquatic plants

    NARCIS (Netherlands)

    Gerven, van Luuk P.A.; Klein, de Jeroen J.M.; Gerla, Daan J.; Kooi, Bob W.; Kuiper, Jan J.; Mooij, Wolf M.

    2015-01-01

    Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that a

  9. Competition for Light and Nutrients in Layered Communities of Aquatic Plants

    NARCIS (Netherlands)

    van Gerven, L.P.A.; de Klein, J.J.M.; Gerla, D.J.; Kooi, B.W.; Kuiper, J.J.; Mooij, W.M.

    2015-01-01

    Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that at h

  10. Competition for light and nutrients in layered communities of aquatic plants.

    Science.gov (United States)

    van Gerven, Luuk P A; de Klein, Jeroen J M; Gerla, Daan J; Kooi, Bob W; Kuiper, Jan J; Mooij, Wolf M

    2015-07-01

    Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that at high supply of light and nutrients, floating plants always dominate due to their primacy for light, even when submerged plants have lower minimal resource requirements. The model also shows that floating-plant dominance cannot be an alternative stable state in light-limited environments but only in nutrient-limited environments, depending on the plants' resource consumption traits. Compared to unlayered communities, the asymmetry in competition for light-coincident with symmetry in competition for nutrients-leads to fundamentally different results: competition outcomes can no longer be predicted from species traits such as minimal resource requirements ([Formula: see text] rule) and resource consumption. Also, the same two species can, depending on the environment, coexist or be alternative stable states. When applied to two common plant species in temperate regions, both the model and field data suggest that floating-plant dominance is unlikely to be an alternative stable state.

  11. How light competition between plants affects their response to climate change.

    Science.gov (United States)

    van Loon, Marloes P; Schieving, Feike; Rietkerk, Max; Dekker, Stefan C; Sterck, Frank; Anten, Niels P R

    2014-09-01

    How plants respond to climate change is of major concern, as plants will strongly impact future ecosystem functioning, food production and climate. Here, we investigated how vegetation structure and functioning may be influenced by predicted increases in annual temperatures and atmospheric CO2 concentration, and modeled the extent to which local plant-plant interactions may modify these effects. A canopy model was developed, which calculates photosynthesis as a function of light, nitrogen, temperature, CO2 and water availability, and considers different degrees of light competition between neighboring plants through canopy mixing; soybean (Glycine max) was used as a reference system. The model predicts increased net photosynthesis and reduced stomatal conductance and transpiration under atmospheric CO2 increase. When CO2 elevation is combined with warming, photosynthesis is increased more, but transpiration is reduced less. Intriguingly, when competition is considered, the optimal response shifts to producing larger leaf areas, but with lower stomatal conductance and associated vegetation transpiration than when competition is not considered. Furthermore, only when competition is considered are the predicted effects of elevated CO2 on leaf area index (LAI) well within the range of observed effects obtained by Free air CO2 enrichment (FACE) experiments. Together, our results illustrate how competition between plants may modify vegetation responses to climate change.

  12. Endophytic benefit for a competitive host is neutralized by increasing ratios of infected plants

    Science.gov (United States)

    Wu, Lianjie; Ren, Anzhi; Jing, Yuanfang; Zhou, Yong; Wang, Xinyu; Qin, Junhua; Gao, Yubao

    2016-01-01

    Leaf endophytes such as Epichloë can affect the competitive ability of host grasses, but the reported responses are inconsistent. We hypothesized that this inconsistency is caused, at least in part, by the following two aspects. One is that a competitive advantage might occur as a result of an increase in storage compounds for both growth and defense. Another is that the effect of the endophyte might be related to both water availability and host density. In a greenhouse experiment, we compared the competitive abilities of endophyte-infected (EI) and endophyte-free (EF) Leymus chinensis, a dominant grass native to the Inner Mongolia Steppe of China, subjected to ten treatments comprised of a factorial combination of two levels of water availability (well-watered and drought) and five proportions of EI to EF plants (12:0, 4:8, 6:6, 8:4, 0:12). The results showed that the competitive ability of EI plants was higher than that of EF under drought. Here, greater belowground biomass and water use efficiency might contribute to better competitiveness of EI plants. When competing under well-watered conditions, endophyte infection did not provide a benefit to the host plant in biomass accumulation, but more carbon was allocated to defense (total phenolics) in EI plants. This scenario could help EI plants suffer less damage than EF when exposed to herbivores in natural habitats. The competitive ability of EI plants was regulated by EI:EF ratios. Competitive ability of EI plants was higher than that of EF plants in mixtures with lower numbers of EI plants, but the beneficial effect of endophyte infection was neutralized in mixtures with higher numbers of EI plants. Overall, endophyte infection improved the competitive ability of the host under either drought or well-watered conditions but in the presence of herbivore, only this benefit was neutralized by increasing ratios of EI plants. We suspect that both the conditional beneficial effects and stabilizing effects of density

  13. Weed biocontrol in landscape restoration

    Science.gov (United States)

    Weed biological control programs in natural areas are often undertaken with the goal of restoring native plant communities and/or ecosystem services to a pre-invasion level. These objectives may be achieved in some areas with biological control alone; however, in other sites integration of biologica...

  14. Spatial heterogeneity in light supply affects intraspecific competition of a stoloniferous clonal plant.

    Directory of Open Access Journals (Sweden)

    Pu Wang

    Full Text Available Spatial heterogeneity in light supply is common in nature. Many studies have examined the effects of heterogeneous light supply on growth, morphology, physiology and biomass allocation of clonal plants, but few have tested those effects on intraspecific competition. In a greenhouse experiment, we grew one (no competition or nine ramets (with intraspecific competition of a stoloniferous clonal plant, Duchesnea indica, in three homogeneous light conditions (high, medium and low light intensity and two heterogeneous ones differing in patch size (large and small patch treatments. The total light in the two heterogeneous treatments was the same as that in the homogeneous medium light treatment. Both decreasing light intensity and intraspecific competition significantly decreased the growth (biomass, number of ramets and total stolon length of D. indica. As compared with the homogeneous medium light treatment, the large patch treatment significantly increased the growth of D. indica without intraspecific competition. However, the growth of D. indica with competition did not differ among the homogeneous medium light, the large and the small patch treatments. Consequently, light heterogeneity significantly increased intraspecific competition intensity, as measured by the decreased log response ratio. These results suggest that spatial heterogeneity in light supply can alter intraspecific interactions of clonal plants.

  15. Ornamental and Turf Pest Control for Commercial Applicators: Pest Control of Ornamental Plants; NCR 12, Lawn Diseases in the Midwest; NCR 26, Lawn Weeds and their Control. Manual 89.

    Science.gov (United States)

    Craig, W. S., Comp.; And Others

    This training manual provides information needed to meet the minimum EPA standards for certification as a commercial applicator of pesticides in the ornamental and turf pest control category. The text discusses pest control of ornamental plants, lawn diseases, and lawn weeds and their control. (CS)

  16. Weed suppression and weed tolerance of wheat cultivars - relevant traits for Integrated Pest Management

    Directory of Open Access Journals (Sweden)

    Verschwele, Arnd

    2014-02-01

    Full Text Available An assortment of 10 winter wheat cultivars was tested for specific effects on weed suppression. Furthermore cultivar specific effects of weed infestation and weed control measures on the crop yield were investigated. Two trial series conducted from 2005 to 2010 demonstrated a wide cultivar specific range of shading capacity and weed suppression. Light penetration and the dry matter of the model weed Sinapis alba were highly correlated (r = 0.87 in trial series A (2005-2007. Consequently, the weed dry matter in the less competitive cultivar Dekan was 5 times higher compared to the weak competitor Cubus. Mechanical weed control by harrowing reduced ears density of all cultivars tested in trial series A. These reductions were significantly higher in the cultivars Bussard and Pegassos compared to the other cultivars. Since the weed infestation was low and negative crop effects by harrowing could be compensated by a higher number of kernels/ear, the yield effects were the same for all cultivars. Contrary to the hypothesis, a cultivar specific yield response by harrowing could not be assessed. Higher competition effects by sowing the model weed Sinapis alba could be realised in trial series B (2008-20120. Consequently, the control measures (a harrowing (b 50% herbicide (c 100% herbicide resulted in significantly higher crop yields ranging from 1.23 t*ha-1 (harrowing to 2.08 t*ha-1 (100% herbicide. The yield reduction caused by the model weed was not the same for all cultivars and was lower for the cultivars Cubus and Limes (6% and 7% compared to Boomer (15%. Thus, weed tolerance could be identified as a cultivar specific trait. There were significant interactions between cultivar and weed control measures: The yield increase (relative to model weed was 5% for Bussard, which was much lower compared to the treatment effects on the cultivar Impression (11%. The hypothesis that yield effects by mechanical and chemical weed control may be affected by the

  17. Common mycorrhizal networks amplify competition by preferential mineral nutrient allocation to large host plants.

    Science.gov (United States)

    Weremijewicz, Joanna; Sternberg, Leonel da Silveira Lobo O'Reilly; Janos, David P

    2016-10-01

    Arbuscular mycorrhizal (AM) fungi interconnect plants in common mycorrhizal networks (CMNs) which can amplify competition among neighbors. Amplified competition might result from the fungi supplying mineral nutrients preferentially to hosts that abundantly provide fixed carbon, as suggested by research with organ-cultured roots. We examined whether CMNs supplied (15) N preferentially to large, nonshaded, whole plants. We conducted an intraspecific target-neighbor pot experiment with Andropogon gerardii and several AM fungi in intact, severed or prevented CMNs. Neighbors were supplied (15) N, and half of the target plants were shaded. Intact CMNs increased target dry weight (DW), intensified competition and increased size inequality. Shading decreased target weight, but shaded plants in intact CMNs had mycorrhizal colonization similar to that of sunlit plants. AM fungi in intact CMNs acquired (15) N from the substrate of neighbors and preferentially allocated it to sunlit, large, target plants. Sunlit, intact CMN, target plants acquired as much as 27% of their nitrogen from the vicinity of their neighbors, but shaded targets did not. These results suggest that AM fungi in CMNs preferentially provide mineral nutrients to those conspecific host individuals best able to provide them with fixed carbon or representing the strongest sinks, thereby potentially amplifying asymmetric competition below ground.

  18. Use of rhizobacteria and endophytes for biological control of weeds

    Directory of Open Access Journals (Sweden)

    Trognitz, Friederike

    2014-02-01

    Full Text Available Weeds cause severe yield losses in agriculture, with a maximum estimate of 34% of yield loss worldwide due to competition between the crops and the weeds for nutrition, light and humidity (OERKE, 2006. Invasive plants contribute partially to other problems. The pollen of common ragweed, Ambrosia artemisiifolia L., for example, is five times more allergenic than grass pollen; already ten pollen grains per m3 air can trigger allergy in sensitized patients, including rhinitis, conjunctivitis and asthma. This neophyte from America has extended the season of allergy in European patients to October. Common ragweed is currently most frequent in Hungary, France and Italy. In Austria, ragweed populations along roads have increased dramatically since 2000. The effective means to control this weed of the Asteraceae family are limited; a single plant can produce up to 6000 seeds which stay in the soil for 40 years. Control using selective herbicides is not possible within stands of the Asteraceae member sunflower. Efforts to use herbivore insects as biological control agents also failed due to the unavailability of insects specializing on this ragweed. The use of plant-associated rhizobacteria and endophytes as bio-herbicides offers a novel alternative to conventional methods. By analogy to experiences from other plant-microbe systems, the chances to find microbes of the desired characteristics are highest when isolating and testing specimens directly from ragweed plants. These organisms often have an extremely narrow host range that permits their use for the control of among several even closely related plant species growing together in a field.

  19. Integration of sunflower (Helianthus annuus) residues with a pre-plant herbicide enhances weed suppression in broad bean (Vicia faba)

    OpenAIRE

    Alsaadawi,I.S; KHALIQ,A.; A.A Al-Temimi; Matloob,A

    2011-01-01

    Field trial was conducted with the aim of utilizing allelopathic crop residues to reduce the use of synthetic herbicides in broad bean (Vicia faba) fields. Sunflower residue at 600 and 1,400 g m-2 and Treflan (trifluralin) at 50, 75 and 100% of recommended dose were incorporated into the soil alone or in combination with each other. Untreated plots were maintained as a control. Herbicide application in plots amended with sunflower residue had the least total weed count and biomass, which was ...

  20. Competition in artifical plant growth media by Trichoderma spp

    DEFF Research Database (Denmark)

    Sarocco, Sabrina; Lübeck, Mette; Vannacci, Giovanni

    of the reason why more biocontrol agents are reaching the market place. A comparative evaluation of life strategies of both the pathogen and its antagonists is required to predict the fate of a biopesticide in agricultural systems.The objectives of this work have been: 1) to screen a collection of Trichoderma...... isolates in a natural pot mix in order to select potential fungal antagonists to be employed in the biocontrol of Rhizoctonia solani damping-off of radish, and 2) to verify the hypothesis that competition for a food base plays a role in reducing pathogen activity. Fifteen Trichoderma spp., selected among...

  1. Competition in artifical plant growth media by Trichoderma spp

    DEFF Research Database (Denmark)

    Sarocco, Sabrina; Lübeck, Mette; Vannacci, Giovanni

    of the reason why more biocontrol agents are reaching the market place. A comparative evaluation of life strategies of both the pathogen and its antagonists is required to predict the fate of a biopesticide in agricultural systems.The objectives of this work have been: 1) to screen a collection of Trichoderma...... isolates in a natural pot mix in order to select potential fungal antagonists to be employed in the biocontrol of Rhizoctonia solani damping-off of radish, and 2) to verify the hypothesis that competition for a food base plays a role in reducing pathogen activity. Fifteen Trichoderma spp., selected among...

  2. Ecologically sustainable weed management

    DEFF Research Database (Denmark)

    Liebman, Matt; Baraibar, Bàrbara; Buckley, Yvonne

    2016-01-01

    will be effective in various locations. Implementing new approaches for weed management will require multidisciplinary teams comprised of scientists, engineers, economists, sociologists, educators, farmers, land managers, industry personnel, policy makers, and others willing to focus on weeds within whole farming......Weed management is a critically important activity on both agricultural and non-agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade......, and greater weed impacts due to changes in climate and land use. Broad-scale use of new approaches is needed if weed management is to be successful in the coming era. We examine three approaches likely to prove useful for addressing current and future challenges from weeds: diversifying weed management...

  3. Microbial activity of soil cultivated with corn in association with weeds under different fertility management systems

    Directory of Open Access Journals (Sweden)

    Christiane Melo

    2014-12-01

    Full Text Available Interactions between weeds and soil microorganisms can give them a competitive advantage over crops. This study assessed the biomass and microbial activity of soil cultivated with weeds and corn (Zea mays L. in monoculture and in competition under different fertility management systems. The experiment considered four soil fertility management systems (calcium and magnesium silicate + fertilization; limestone + fertilization; no correction source + fertilization; no correction source + no fertilization and 12 crops (five competition arrangements between corn and weeds Urochloa brizantha (Hochst. ex A. Rich. R.D. Webster, lpomoea grandifolia (Dammer O'Donell, Conyza canadensis (L. Cronquist, Hyptis suaveolens (L. Poit., and Bidens pilosa L. plus the six species in monoculture and bare soil. After 60 d coexisting in a greenhouse, soil samples were collected to determine microbial biomass, respiration rate, and metabolic quotient. Soils cultivated with B. pilosa and Z. mays+U. brizantha showed higher microbial biomass. Cultivation of B. pilosa and Z. mays+H. suaveolens provided greater energy efficiency to maintain microbial cells. Biomass and microbial activity were altered by plant species, coexistence, and soil fertility management. Calcium and magnesium silicate, as well as limestone similarly influenced biomass and respiration rate of soil cultivated with most species. For some crops, the Si source was better than limestone to promote lower specific activity of the edaphic microbiota. The change in the microbial activity of soil can be a strategy used by the species to minimize the effects of competition.

  4. Weed Warriors

    Science.gov (United States)

    Buczynski, Sandy

    2007-01-01

    In these activities, middle school and high school students examine the threat of nonnative plant species to Hawaiian ecosystems. Students explore different viewpoints on alien plants and consider how beliefs and attitudes may affect others' decisions concerning nonnative plant species. Students also identify invasive plant characteristics and…

  5. Weed Warriors

    Science.gov (United States)

    Buczynski, Sandy

    2007-01-01

    In these activities, middle school and high school students examine the threat of nonnative plant species to Hawaiian ecosystems. Students explore different viewpoints on alien plants and consider how beliefs and attitudes may affect others' decisions concerning nonnative plant species. Students also identify invasive plant characteristics and…

  6. Competition

    CERN Multimedia

    Staff Association

    2017-01-01

    Get ready for the Easter Egg Hunt! The Staff Association is organising a competition from 10 to 21 April 2017. There are several Go Sport gift vouchers to win, with a value of 50 € each. Try your luck! Count the number of different eggs that we have hidden on our website. Then indicate your answer in the online form. To participate, you just need to be a member of the Staff Association. Winners will be randomly drawn among the correct answers.

  7. Competition

    CERN Multimedia

    Staff Association

    2016-01-01

      The Staff Association is organising a competition from 13 to 21 December 2016. There are several Go Sport vouchers to win with a value of 50 € each. Try your luck! To participate, you just have to be a member of the Staff Association and take the online quiz: https://ap-vote.web.cern.ch/content/jeu-concours-de-noel. The winners will be drawn among the correct answers.

  8. Competition

    CERN Multimedia

    Staff Association

    2016-01-01

      The Staff Association is organising a competition from April 11 to 20. There are several Go Sport gift vouchers with a value of 50 € each to win. Try your luck! To participate, you just have to be a member of the Staff Association and take the online quiz: https://ap-vote.web.cern.ch/content/jeu-concours. The winners will be drawn among the correct answers.

  9. Plant water use affects competition for nitrogen: why drought favors invasive species in California.

    Science.gov (United States)

    Everard, Katherine; Seabloom, Eric W; Harpole, W Stanley; de Mazancourt, Claire

    2010-01-01

    Abstract: Classic resource competition theory typically treats resource supply rates as independent; however, nutrient supplies can be affected by plants indirectly, with important consequences for model predictions. We demonstrate this general phenomenon by using a model in which competition for nitrogen is mediated by soil moisture, with competitive outcomes including coexistence and multiple stable states as well as competitive exclusion. In the model, soil moisture regulates nitrogen availability through soil moisture dependence of microbial processes, leaching, and plant uptake. By affecting water availability, plants also indirectly affect nitrogen availability and may therefore alter the competitive outcome. Exotic annual species from the Mediterranean have displaced much of the native perennial grasses in California. Nitrogen and water have been shown to be potentially limiting in this system. We parameterize the model for a Californian grassland and show that soil moisture-mediated competition for nitrogen can explain the annual species' dominance in drier areas, with coexistence expected in wetter regions. These results are concordant with larger biogeographic patterns of grassland invasion in the Pacific states of the United States, in which annual grasses have invaded most of the hot, dry grasslands in California but perennial grasses dominate the moister prairies of northern California, Oregon, and Washington.

  10. Applying a weed risk assessment approach to GM crops.

    Science.gov (United States)

    Keese, Paul K; Robold, Andrea V; Myers, Ruth C; Weisman, Sarah; Smith, Joe

    2014-12-01

    Current approaches to environmental risk assessment of genetically modified (GM) plants are modelled on chemical risk assessment methods, which have a strong focus on toxicity. There are additional types of harms posed by plants that have been extensively studied by weed scientists and incorporated into weed risk assessment methods. Weed risk assessment uses robust, validated methods that are widely applied to regulatory decision-making about potentially problematic plants. They are designed to encompass a broad variety of plant forms and traits in different environments, and can provide reliable conclusions even with limited data. The knowledge and experience that underpin weed risk assessment can be harnessed for environmental risk assessment of GM plants. A case study illustrates the application of the Australian post-border weed risk assessment approach to a representative GM plant. This approach is a valuable tool to identify potential risks from GM plants.

  11. Genetic resources: the basis for sustainable and competitive plant breeding

    Directory of Open Access Journals (Sweden)

    Luciano Lourenço Nass

    2012-12-01

    Full Text Available Plant genetic resources are the fuel for breeding, which in the search for higher yield and adapted genotypes, manipulates genes in order to meet the needs of farmers, and especially, of the current market. However, the use of accessions available in germplasm banks is low. Topics discussed in this paper emphasize the importance of plant genetic resources, and warn about problems related to genetic vulnerability; also, they discuss about aspects of costs involved in conservation and suggest recommendations for strengthening the area in Brazil.

  12. Proving allelopathy in crop-weed interactions

    Science.gov (United States)

    Allelopathy (plant/plant chemical warfare) is difficult to prove, especially when competition for resources is the dominant component of plant/plant interference (interference = allelopathy +competition). This paper describes experimental approaches for proving allelopathy and points out common pit...

  13. Weed supression by smother crops and selective herbicides

    Directory of Open Access Journals (Sweden)

    Severino Francisco José

    2004-01-01

    Full Text Available Using a smother crop is thought to suppress weed density and to add other beneficial effects in sustainable agricultural systems. Weed suppression ought to be considered an essential component of integrated weed management. However, very little is known about the effects of green manure plants on weeds. This study evaluated the influence of three green manure species on weed suppression and selectivity of herbicides. A field experiment was designed to determine the effect of the green manure species Crotalaria juncea, Arachis pintoi and pigeon pea on the weeds Brachiaria decumbens, guineagrass and hairy beggarticks, and on the natural weed infestation in the inter rows area of an avocado orchard. The weed species were suppressed differently by each green manure species. Soil samples collected from the field experiment presented a residual effect, of at least 30 d, in suppressing weed seed bank recruitment; this residual effect was caused by the residues of the green manure present in the soil. When the green manure was incorporated into the top 5 cm of soil or left on the surface, in a greenhouse experiment, the emergence of weed seeds was significantly inhibited, depending on the species, and on the amount and depth of green manure incorporation. Greenhouse experiments indicate that pre-emergence herbicides cause lower phytotoxicity than post-emergence Arachis pintoi. Smother crops using green manure species, when well established in an area, provide additional weed control to the cropping system and are effective and valuable tools in integrated weed management.

  14. Critical period of weed control In cumin (Cuminum cyminum

    Directory of Open Access Journals (Sweden)

    azade hoseyni

    2009-06-01

    Full Text Available In order to evaluate the critical period of weed control in Cumin, an experiment with Complete Randomized Block Design and three replications was conducted in experimental field of Faculty of Agriculture, Ferdowsi University of Mashhad, During 2004-2005 growing season. Treatments included different combinations of weed free and weed infested periods (20, 30, 40 and 80 days after germination plus weedy check and weed free check. Critical period weed control was evaluated with Gompertz and Logestic functions. Traits measured were yield and yield components, harvest index of cumin and also number and weight of weed species. Results showed the critical period was between 24-38 days after germination. With increasing interfereing period at early or late growth stages of cumin, the economic yield was reduced. By extending weeding periods at early stage of growth or during the growth period, dry weight of weeds were reduced, while extending weeding period at the end of growth stage and also weed free during growth period, early or late stages of growth had no significant effects on yield components except on number of umbels per plant. Harvest index was positively affected by early weeding. It appears that early weeding was somehow more effective on yield components for cumin.

  15. Strigolactones are a new-defined class of plant hormones which inhibit shoot branching and mediate the interaction of plant-AM fungi and plant-parasitic weeds

    Institute of Scientific and Technical Information of China (English)

    ZAITLIN; David

    2009-01-01

    Because plants are sessile organisms,the ability to adapt to a wide range of environmental conditions is critical for their survival.As a consequence,plants use hormones to regulate growth,mitigate biotic and abiotic stresses,and to communicate with other organisms.Many plant hormones function plei-otropically in vivo,and often work in tandem with other hormones that are chemically distinct.A newly-defined class of plant hormones,the strigolactones,cooperate with auxins and cytokinins to control shoot branching and the outgrowth of lateral buds.Strigolactones were originally identified as compounds that stimulated the germination of parasitic plant seeds,and were also demonstrated to induce hyphal branching in arbuscular mycorrhizal(AM) fungi.AM fungi form symbioses with higher plant roots and mainly facilitate the absorption of phosphate from the soil.Conforming to the classical definition of a plant hormone,strigolactones are produced in the roots and translocated to the shoots where they inhibit shoot outgrowth and branching.The biosynthesis of this class of compounds is regulated by soil nutrient availability,i.e.the plant will increase its production of strigolactones when the soil phosphate concentration is limited,and decrease production when phosphates are in ample supply.Strigolactones that affect plant shoot branching,AM fungal hyphal branching,and seed germination in parasitic plants facilitate chemical synthesis of similar compounds to control these and other biological processes by exogenous application.

  16. Weed hosts of cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae).

    Science.gov (United States)

    Vennila, S; Prasad, Y G; Prabhakar, M; Agarwal, Meenu; Sreedevi, G; Bambawale, O M

    2013-03-01

    The exotic cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) invaded India during 2006, and caused widespread infestation across all nine cotton growing states. P. solenopsis also infested weeds that aided its faster spread and increased severity across cotton fields. Two year survey carried out to document host plants of P. solenopsis between 2008 and 2010 revealed 27, 83, 59 and 108 weeds belonging to 8, 18, 10 and 32 families serving as alternate hosts at North, Central, South and All India cotton growing zones, respectively. Plant species of four families viz., Asteraceae, Amaranthaceae, Malvaceae and Lamiaceae constituted almost 50% of the weed hosts. While 39 weed species supported P. solenopsis multiplication during the cotton season, 37 were hosts during off season. Higher number of weeds as off season hosts (17) outnumbering cotton season (13) at Central over other zones indicated the strong carryover of the pest aided by weeds between two cotton seasons. Six, two and seven weed hosts had the extreme severity of Grade 4 during cotton, off and cotton + off seasons, respectively. Higher number of weed hosts of P. solenopsis were located at roadside: South (12) > Central (8) > North (3) zones. Commonality of weed hosts was higher between C+S zones, while no weed host was common between N+S zones. Paper furnishes the wide range of weed hosts of P. solenopsis, discusses their significance, and formulated general and specific cultural management strategies for nationwide implementation to prevent its outbreaks.

  17. High Colonization Possibility of Some Species of Weeds in Suaeda salsa Community: From an Ecological Stoichiometry Perspective

    Science.gov (United States)

    Ge, Changzi; Wang, Renqing; Chai, Yanchao; Wang, Haiqing; Kan, Manman; Liu, Jian

    2017-01-01

    Suaeda salsa community is a vegetation type in saline-alkali areas. Weed invasion and colonization in S. salsa communities lead to fragmentationsof S. salsa communities. The colonization of invaded weeds in S. salsa communities is related to community succession of saline-alkali zones. The fragmented S. salsa community may be restored if the mechanism of invaded weed colonization in S. salsa communities is clearly elucidated. Thus, we studied the ecological stoichiometric characteristics of soils and plants in a salt marsh to explain the high colonization possibility of invaded weeds in S. salsa communities. In October 2014, soils and plants were collected from Dongfeng Salt Marsh, Jiaozhou Bay, Shandong Province, China. The ratio of Ex-N/Ex-P in soil was less than 13, which suggests a relative nitrogen limitation for the primary production in the zone. The minimum phosphorus content in plants was higher than 1 mg g-1, whereas the maximum nitrogen content in plants was less than 13 mg g-1. These results imply that phosphorus was abundant, whereas nitrogen was deficient in the area. The plants in the salt marsh may be limited by nitrogen. Given the relatively lower nitrogen contents in Cyperus glomeratus, Echinochloa crusgalli, and Aster subulatus than that in S. salsa, these three species exhibited higher competitiveness than S. salsa did when nitrogen was limited in primary production. These weed species may colonize highly in S. salsa communities. Moreover, nitrogen fertilization might be effective to maintain S. salsa community in Dongfeng Salt Marsh, whereas its effects on controlling weeds colonization in S. salsa communities need more studies to verify. PMID:28135313

  18. High Colonization Possibility of Some Species of Weeds in Suaeda salsa Community: From an Ecological Stoichiometry Perspective.

    Science.gov (United States)

    Ge, Changzi; Wang, Renqing; Chai, Yanchao; Wang, Haiqing; Kan, Manman; Liu, Jian

    2017-01-01

    Suaeda salsa community is a vegetation type in saline-alkali areas. Weed invasion and colonization in S. salsa communities lead to fragmentationsof S. salsa communities. The colonization of invaded weeds in S. salsa communities is related to community succession of saline-alkali zones. The fragmented S. salsa community may be restored if the mechanism of invaded weed colonization in S. salsa communities is clearly elucidated. Thus, we studied the ecological stoichiometric characteristics of soils and plants in a salt marsh to explain the high colonization possibility of invaded weeds in S. salsa communities. In October 2014, soils and plants were collected from Dongfeng Salt Marsh, Jiaozhou Bay, Shandong Province, China. The ratio of Ex-N/Ex-P in soil was less than 13, which suggests a relative nitrogen limitation for the primary production in the zone. The minimum phosphorus content in plants was higher than 1 mg g-1, whereas the maximum nitrogen content in plants was less than 13 mg g-1. These results imply that phosphorus was abundant, whereas nitrogen was deficient in the area. The plants in the salt marsh may be limited by nitrogen. Given the relatively lower nitrogen contents in Cyperus glomeratus, Echinochloa crusgalli, and Aster subulatus than that in S. salsa, these three species exhibited higher competitiveness than S. salsa did when nitrogen was limited in primary production. These weed species may colonize highly in S. salsa communities. Moreover, nitrogen fertilization might be effective to maintain S. salsa community in Dongfeng Salt Marsh, whereas its effects on controlling weeds colonization in S. salsa communities need more studies to verify.

  19. Growth rates of rhizosphere microorganisms depend on competitive abilities of plants for nitrogen

    Science.gov (United States)

    Blagodatskaya, Evgenia; Littschwager, Johanna; Lauerer, Marianna; Kuzyakov, Yakov

    2010-05-01

    Rhizosphere - one of the most important ‘hot spots' in soil - is characterized not only by accelerated turnover of microbial biomass and nutrients but also by strong intra- and inter-specific competition. Intra-specific competition occurs between individual plants of the same species, while inter-specific competition can occur both at population level (plant species-specific, microbial species-specific interactions) and at community level (plant - microbial interactions). Such plant - microbial interactions are mainly governed by competition for available N sources, since N is one of the main growth limiting nutrients in natural ecosystems. Functional structure and activity of microbial community in rhizosphere is not uniform and is dependent on quantity and quality of root exudates which are plant specific. It is still unclear how microbial growth and turnover in the rhizosphere are dependent on the features and competitive abilities of plants for N. Depending on C and N availability, acceleration and even retardation of microbial activity and carbon mineralization can be expected in the rhizosphere of plants with high competitive abilities for N. We hypothesized slower microbial growth rates in the rhizosphere of plants with smaller roots, as they usually produce less exudates compared to plants with small shoot-to-root ratio. As the first hypothesis is based solely on C availability, we also expected the greater effect of N availability on microbial growth in rhizosphere of plants with smaller root mass. These hypothesis were tested for two plant species of strawberry: Fragaria vesca L. (native species), and Duchesnea indica (Andrews) Focke (an invasive plant in central Europe) growing in intraspecific and interspecific competition. Microbial biomass and the kinetic parameters of microbial growth in the rhizosphere were estimated by dynamics of CO2 emission from the soil amended with glucose and nutrients. Specific growth rate (µ) of soil microorganisms was

  20. Effects of competitive interactions of different life forms submersed plants on biomass allocation in shallow lakes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiu-feng

    2010-01-01

    Plant competition has been recognized as one of the most important factors influencing the structure and function of lake ecosystems.Competition from plants of dissimilar growth form may have profound effects on shallow lakes.An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dissimilar growth forms on the biomass allocations.Hydrilla verticillata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern.Results showed that the growth of Ⅴ.natans was significantly affected by the H.verticillata and caused a sharp reduction of biomass,but the root:shoot ratio of Ⅴ.natans was not affected significantly and there was a minimal increase in mixture: while for H.verticillata,the biomass and the root:shoot ratio were not significantly changed by the competitive interactions of Ⅴ.natans,there was minimal increase qf biomass and minimal decrease of the root:shoot ratio.These results may indicate that the phant which candevelop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that dependsmore on light availability near the sediment.

  1. The Evaluation and the Comparison of the Effect of Mechanical Weeding Systems on Rice Weed

    Directory of Open Access Journals (Sweden)

    Fazlollah Eskandari Cherati

    2012-08-01

    Full Text Available In order to study the influence of different methods of controlling weeds such as mechanical weeding and mechanical weeder efficiency analysis in mechanical cultivation conditions, in farming year of 2011 an experiment was done in a farm in coupling and development of technology center in Haraz, Iran. The treatments consisted of (I control treatment: where no weeding was done, (II use of mechanical weeding without engine and (III power mechanical weeding. Results showed that experimental treatments had significantly different effects (p = 0.05 on yield traits and number of filled grains per panicle, while treatments had the significant effects on grain weight and dry weight of weeds in the first, second and third weeding methods at 1% of confidence level. Treatment (II had its most significant effect on number of filled grains per panicle and yield performance standpoint, which was 3705.97 kg/ha in its highest peak. Treatment (III was ranked as second influential with 3559.8 kg/ha. In addition, under (I treatments, 2364.73 kg/ha of yield produced. The minimum dry weights of weeds in all weeding methods were related to the treatment (II, (III and (I, respectively. The correlation coefficient analysis showed that total yield had a significant positive correlation with the panicle grain yield per plant (r = 0.55* and the number of grains/panicle (r = 0.57* and the number of filled grains (r = 0.63*. Total rice yield also had negative correlation of r = -0.64* with weed dry weight at second weed sampling time (17 DAT. The weed dry weight at third and fourth sampling times (24 and 40 DAT had negative correlations of -0.65** and r = -0.61* with rice yield, respectively.

  2. Bistability of mangrove forests and competition with freshwater plants

    Science.gov (United States)

    Jiang, Jiang; Fuller, Douglas O; Teh, Su Yean; Zhai, Lu; Koh, Hock Lye; DeAngelis, Donald L.; Sternberg, L.D.S.L.

    2015-01-01

    Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.

  3. The influence of arbuscular mycorrhizae and light on Wisconsin (USA) sand savanna understories 2. Plant competition.

    Science.gov (United States)

    Landis, Frank C; Gargas, Andrea; Givnish, Thomas J

    2005-11-01

    Wisconsin (USA) oak savannas are endangered plant communities that have remarkably high plant species diversity. To investigate factors underlying this richness, we experimentally investigated the potentially interacting effects of light gradients and arbuscular mycorrhizal fungi (AMF) on plant competition in the greenhouse, using a fully randomized block design. We used four plant species, soil, and AMF from a remnant sand savanna, under two light and five AMF treatments. Plants were grown four per pot under two competition treatments (either one or four species per pot) for 20 weeks. Using ANOVA, we found that all species showed significant treatment effects on total and shoot biomass, primarily due to differences in competition and light, less to AMF. However, effects were the opposite of predictions. Putatively mycorrhizal plants showed neutral to negative responses to AMF, and a nonmycorrhizal species outcompeted AMF species in infected pots. We concluded that our experimental setup of small pots, sandy soil, and long growing period had induced parasitism by the AMF on susceptible hosts. This unexpected result is consistent with field data from the sand savanna, and may help explain how nonmycorrhizal plants can compete successfully with AMF species in established, species-rich communities.

  4. Eradication of Major Weeds

    Science.gov (United States)

    Indian Journal of Adult Education, 1975

    1975-01-01

    Strategies for weed control in cropped and non-cropped areas are presented together with an operational plan for implementing a program for weed control at the national level. The program includes training personnel and community education procedures. (EC)

  5. Eradication of Major Weeds

    Science.gov (United States)

    Indian Journal of Adult Education, 1975

    1975-01-01

    Strategies for weed control in cropped and non-cropped areas are presented together with an operational plan for implementing a program for weed control at the national level. The program includes training personnel and community education procedures. (EC)

  6. The critical period of weed control in corn) Zea mays) at Mashhad, Iran

    OpenAIRE

    majid abaspoor; parviz rezvani moghadam

    2009-01-01

    In order to determine the critical period of weed control in corn, an experiment was conducted at Research Station, Faculty of Agriculture, Ferdowsi University of Mashhad in year 2000. The experiment consisted of two discrete periods, a weed-free and a weed infested period. The weed-free period consisted of removing all weeds till 4th (19 days after planting), 7th (34 days after planting), 11th (48 days after planting), 13th (52 days after planting), and 17th (59 days after planting), leaf gr...

  7. Effect of different integrated weed management methods on weed density and yield of sugar beet crop

    Directory of Open Access Journals (Sweden)

    alireza koochaki

    2009-06-01

    Full Text Available In order to compare different weed management methods in sugar beet, two experiments were conducted at mashhad for two years in 2005-2006 and 2006-2007. Each experiment designed as a Complete Randomized Block with three replication. The treatments include: Metamitron(Goltix plus Phenmedipham (Betanal (Gol+Bet, Goltix plus Cultivation (Gol+Cu, Disk plus Betanal (Di+Bet, Disk plus Cultivation(Di+Cu, Cover Crop plus Betanal (Co+Bet, Cover Crop plus Cultivation (Co+Cu, Weeding (W and Betanal plus Weeding (Bet+W. Samplings were taken at three stages early season, after imposing the treatments and late season. Results showed that at early season in two experiments, density of weeds was lower in cover crop and disk treatment compared with other treats and the second sampling in first experiment, weeding and disk plus cultivation of treatments with 21.5 and 26.6 respectively plants per m2 and in second experiment year, weeding and application betanal plus weeding treatments, with 14 and 17.8 respectively plant in m2 showed the lowest. In the second experiment year, minimum and maximum sugar beet yield were obtained with cover crop plus betanal and weeding with 43 and 104 ton per hectare respectively. The lowest yield was obtained in check plots with 3.5ton per hectare. Maximum sugar contain (19.35% was obtained in betanal herbicide plus cultivation treatment and minimum (14.88% was obtained with hand weeding treatment. However maximum sugar beet yield was obtained with betanal plus weeding (17.85 ton per hectare and the minimum with cover crop plus betanal (7.5 ton per hectare. Key words: integrated weed management, cover crop, herbicide, cultivation, sugar beet.

  8. Plant traits related to nitrogen uptake influence plant-microbe competition

    OpenAIRE

    Moreau, Delphine; Pivato, Barbara; Bru, David; Busset, Hugues; Deau, Florence; Faivre, Céline; Matejicek, Annick; Strbik, Florence; Mougel, Christophe

    2015-01-01

    Plant species are important drivers of soil microbial communities. However, how plant functional traits are shaping these communities has received less attention though linking plant and microbial traits is crucial for better understanding plant-microbe interactions. Our objective was to determine how plant-microbe interactions were affected by plant traits. Specifically we analyzed how interactions between plant species and microbes involved in nitrogen cycling were affected by plant traits ...

  9. A mechanistic model of microbial competition in the rhizosphere of wetland plants

    Science.gov (United States)

    Aslkhodapasand, F.; Mayer, K. U.; Neumann, R. B.

    2014-12-01

    Wetlands are the largest natural source of methane to the atmosphere. Although they cover only 4-6% of earth's surface, wetlands contribute 20-39% of global methane emissions. Hollow aerenchyma tissues inside the roots, stems and leaves of plants represent one of the most important methane emission pathways for wetlands. Up to 90% of the emitted methane can diffuse through these hollow tissues that directly connect the atmosphere to the anoxic soils where methane is generated. Thus, concentrations of methane surrounding plant roots directly impact the amount of methane emitted by wetlands. Methane concentrations are controlled by a variety of microbial processes occurring in the soil around the roots of plants (aka the rhizosphere). The rhizosphere is a microbial hotspot sustained by plant inputs of organic carbon and oxygen; plant roots exude excess organic carbon generated in photosynthesis into the rhizosphere and atmospheric oxygen diffuses down to the rhizosphere through the hollow aerenchyma tissues. This environment supports a variety of microbial communities that compete with each other for available carbon and oxygen, including methanogens, methanotrophs, and heterotrophs. Methanogens ferment organic carbon into methane, a reaction that is inhibited by oxygen; methanotrophs use oxygen to oxidize methane into carbon dioxide; and heterotrophs use oxygen to oxidize organic carbon into carbon dioxide. We are interested in understanding how competition between these communities alters methane concentrations and responds to variations in plant inputs. To this end, we have developed a mechanistic root-scale model that describes microbial competition for organic carbon and oxygen in the rhizosphere of wetland plants. Our results focus on variations in rates of methane production, methane oxidation, heterotrophic respiration, and diffusion of methane into plant roots as a result of changes in carbon and oxygen inputs. The study provides insight into how plant

  10. Weed Diversity Affects Soybean and Maize Yield in a Long Term Experiment in Michigan, USA.

    Science.gov (United States)

    Ferrero, Rosana; Lima, Mauricio; Davis, Adam S; Gonzalez-Andujar, Jose L

    2017-01-01

    Managing production environments in ways that promote weed community diversity may enhance both crop production and the development of a more sustainable agriculture. This study analyzed data of productivity of maize (corn) and soybean in plots in the Main Cropping System Experiment (MCSE) at the W. K. Kellogg Biological Station Long-Term Ecological Research (KBS-LTER) in Michigan, USA, from 1996 to 2011. We used models derived from population ecology to explore how weed diversity, temperature, and precipitation interact with crop yields. Using three types of models that considered internal and external (climate and weeds) factors, with additive or non-linear variants, we found that changes in weed diversity were associated with changes in rates of crop yield increase over time for both maize and soybeans. The intrinsic capacity for soybean yield increase in response to the environment was greater under more diverse weed communities. Soybean production risks were greatest in the least weed diverse systems, in which each weed species lost was associated with progressively greater crop yield losses. Managing for weed community diversity, while suppressing dominant, highly competitive weeds, may be a helpful strategy for supporting long term increases in soybean productivity. In maize, there was a negative and non-additive response of yields to the interaction between weed diversity and minimum air temperatures. When cold temperatures constrained potential maize productivity through limited resources, negative interactions with weed diversity became more pronounced. We suggest that: (1) maize was less competitive in cold years allowing higher weed diversity and the dominance of some weed species; or (2) that cold years resulted in increased weed richness and prevalence of competitive weeds, thus reducing crop yields. Therefore, we propose to control dominant weed species especially in the years of low yield and extreme minimum temperatures to improve maize yields

  11. Weed Diversity Affects Soybean and Maize Yield in a Long Term Experiment in Michigan, USA

    Science.gov (United States)

    Ferrero, Rosana; Lima, Mauricio; Davis, Adam S.; Gonzalez-Andujar, Jose L.

    2017-01-01

    Managing production environments in ways that promote weed community diversity may enhance both crop production and the development of a more sustainable agriculture. This study analyzed data of productivity of maize (corn) and soybean in plots in the Main Cropping System Experiment (MCSE) at the W. K. Kellogg Biological Station Long-Term Ecological Research (KBS-LTER) in Michigan, USA, from 1996 to 2011. We used models derived from population ecology to explore how weed diversity, temperature, and precipitation interact with crop yields. Using three types of models that considered internal and external (climate and weeds) factors, with additive or non-linear variants, we found that changes in weed diversity were associated with changes in rates of crop yield increase over time for both maize and soybeans. The intrinsic capacity for soybean yield increase in response to the environment was greater under more diverse weed communities. Soybean production risks were greatest in the least weed diverse systems, in which each weed species lost was associated with progressively greater crop yield losses. Managing for weed community diversity, while suppressing dominant, highly competitive weeds, may be a helpful strategy for supporting long term increases in soybean productivity. In maize, there was a negative and non-additive response of yields to the interaction between weed diversity and minimum air temperatures. When cold temperatures constrained potential maize productivity through limited resources, negative interactions with weed diversity became more pronounced. We suggest that: (1) maize was less competitive in cold years allowing higher weed diversity and the dominance of some weed species; or (2) that cold years resulted in increased weed richness and prevalence of competitive weeds, thus reducing crop yields. Therefore, we propose to control dominant weed species especially in the years of low yield and extreme minimum temperatures to improve maize yields

  12. Weeds optimally grow in peat swamp after burning

    Directory of Open Access Journals (Sweden)

    P.D. Susanti

    2014-07-01

    Full Text Available After clearing land by burning the peat, then the weeds and undergrowth will flourish. Even sometimes, the weeds are eventually burned again. Weed is known as a destroyer plant that has to be controlled. Through proper treatment, the existing weeds in peatlands can be potentiallly exploited. The purpose of this study was to determine the calorific value of briquettes as one of peatland weeds utilization. The results showed that the calorific value ranged from 2,492 cal/g to 5,230 cal/g. The lowest calorific value was on ‘teki kecil’ grass (Scirpus grossus Lf, while the highest calorific value was observed for ‘bantalaki grass’ (Hymenachne amplexicaulis Nees. The high calorific value of the peat weeds are potential for biomass briquettes raw materials. The utilization and use of peat weed briquettes as a raw materials expected can reduce land degradation due to peat swamp burning

  13. Comparison of power output by rice (Oryza sativa) and an associated weed (Echinochloa glabrescens) in vascular plant bio-photovoltaic (VP-BPV) systems.

    Science.gov (United States)

    Bombelli, Paolo; Iyer, Durgaprasad Madras Rajaraman; Covshoff, Sarah; McCormick, Alistair J; Yunus, Kamran; Hibberd, Julian M; Fisher, Adrian C; Howe, Christopher J

    2013-01-01

    Vascular plant bio-photovoltaics (VP-BPV) is a recently developed technology that uses higher plants to harvest solar energy and the metabolic activity of heterotrophic microorganisms in the plant rhizosphere to generate electrical power. In the present study, electrical output and maximum power output variations were investigated in a novel VP-BPV configuration using the crop plant rice (Oryza sativa L.) or an associated weed, Echinochloa glabrescens (Munro ex Hook. f.). In order to compare directly the physiological performances of these two species in VP-BPV systems, plants were grown in the same soil and glasshouse conditions, while the bio-electrochemical systems were operated in the absence of additional energy inputs (e.g. bias potential, injection of organic substrate and/or bacterial pre-inoculum). Diurnal oscillations were clearly observed in the electrical outputs of VP-BPV systems containing the two species over an 8-day growth period. During this 8-day period, O. sativa generated charge ∼6 times faster than E. glabrescens. This greater electrogenic activity generated a total charge accumulation of 6.75 ± 0.87 Coulombs for O. sativa compared to 1.12 ± 0.16 for E. glabrescens. The average power output observed over a period of about 30 days for O. sativa was significantly higher (0.980 ± 0.059 GJ ha(-1) year(-1)) than for E. glabrescens (0.088 ± 0.008 GJ ha(-1) year(-1)). This work indicates that electrical power can be generated in both VP-BPV systems (O. sativa and E. glabrescens) when bacterial populations are self-forming. Possible reasons for the differences in power outputs between the two plant species are discussed.

  14. Ecologically sustainable weed management

    NARCIS (Netherlands)

    Liebman, Matt; Baraibar, Bàrbara; Buckley, Yvonne; Childs, Dylan; Christensen, Svend; Cousens, Roger; Eizenberg, Hanan; Heijting, Sanne; Loddo, Donato; Merotto, Aldo; Renton, Michael; Riemens, Marleen

    2016-01-01

    Weed management is a critically important activity on both agricultural and non-agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade, and

  15. Horny Goat Weed

    Science.gov (United States)

    Horny goat weed is an herb. The leaves are used to make medicine. As many as 15 horny goat weed species are known as “yin yang huo” in Chinese medicine. Horny goat weed is used for weak back and knees, joint ...

  16. Weed control using herbicides in short-rotation intensively cultured poplar plantations.

    Science.gov (United States)

    Edward A. Hansen; Daniel A. Netzer

    1985-01-01

    Summarizes a series of studies that investigated chemical weed control from time of planting to the end of the second growing season. The studies confirm the importance of weed control with preemergents at the time of planting and the importance of additional weed control before the start of the second growing season.

  17. Chronic wind and plant communities in dunes: Total biomass, inter-specific competition, and species abundance

    NARCIS (Netherlands)

    He, W.M.; Xi, W.M.; Anten, N.P.R.

    2013-01-01

    Chronic wind is an important ecological factor, but its direct roles in shaping plant communities remain poorly understood. We hypothesized that chronic wind can modulate community productivity, inter-specific competition, and species abundance in inland dunes. We conducted an experiment with three

  18. Simulation and Visualisation of Functional Landscapes: Effects of the Water Resource Competition Between Plants

    Institute of Scientific and Technical Information of China (English)

    Vincent Le Chevalier; Marc Jaeger; Xing Mei; Paul-Henry Cournède

    2007-01-01

    Vegetation ecosystem simulation and visualisation are challenging topics involving multidisciplinary aspects. In this paper, we present a new generic frame for the simulation of natural phenomena through manageable and interacting models. It focuses on the functional growth of large vegetal ecosystems, showing coherence for scales ranging from the individual plant to communities and with a particular attention to the effects of water resource competition between plants. The proposed approach is based on a model of plant growth in interaction with the environmental conditions. These are deduced from the climatic data (light, temperature, rainfall) and a model of soil hydrological budget. A set of layers is used to store the water resources and to build the interfaces between the environmental data and landscape components: temperature, rain, light, altitude, lakes, plant positions, biomass, cycles, etc. At the plant level, the simulation is performed for each individual by a structural-functional growth model, interacting with the plant's environment. Temperature is spatialised, changing according to altitude, and thus locally controls plant growth speed. The competition for water is based on a soil hydrological model taking into account rainfalls, water runoff, absorption, diffusion, percolation in soil. So far, the incoming light radiation is not studied in detail and is supposed constant. However, competition for light between plants is directly taken into account in the plant growth model. In our implementation, we propose a simple architecture for such a simulator and a simulation scheme to synchronise the water resource updating (on a temporal basis) and the plant growth cycles (determined by the sum of daily temperatures). The visualisation techniques are based on sets of layers, allowing both morphological and functional landscape views and providing interesting tools for ecosystem management. The implementation of the proposed frame leads to encouraging

  19. Allelopatic potential of weeds under the minimalization of soil treatment

    Directory of Open Access Journals (Sweden)

    Mikhail A. Mazirov

    2014-01-01

    Full Text Available The content of water-dispersible phenol substances in rhizosphere both of annual and perennial species of weeds (Cirsium arvense, Sonchus arvensis increases under soil treatment minimalization. The higher content of phenol substances of researched weeds is defined in rhizosphere of Common Couch (Agropyrum repens. The absence of intensive anthropogenic treatment of plowing layer which accumulates the significant mass of weed’s roots in the cause of much more higher allelopathic potential of some species’ of weeds. The high level of saturation by weeds in agrophytocoenosis under non-tillage soil treatment is defines the competitiveness between certain sepsis’ of weeds, especially, at the beginning of the vegetation. In this case, increasing the secretion of phenol substances is one of the physiological screenings of such competitiveness.

  20. Effect of tillage system on yield and weed populations of soybean ( Glycin Max L.).

    Science.gov (United States)

    Hosseini, Seyed Z; Firouzi, Saeed; Aminpanah, Hashem; Sadeghnejhad, Hamid R

    2016-03-01

    Field experiment was conducted at Agricultural and Natural Resources Research Center of Golestan Province, Iran, to determine the effects of tillage system and weed management regime on yield and weed populations in soybean ( Glycin max L.). The experimental design was a split plot where the whole plot portion was a randomized complete block with three replicates. Main plots were tillage system: 1- No-till row crop seeding, 2- No-till seed drilling, 3- Tillage with disc harrow and drill planting, 4- Tillage with chisel packer and drill planting. The subplots were weed management regimes: 1-Weed control with herbicide application, 2- Hand weeding, 3- Herbicide application plus hand weeding, and 4- Non-weeding. Results indicated that the main effects of tillage system and weed management regime were significant for seed yield, pod number per plant, seed number per pod, weed density and biomass, while their interaction were significant only for weed density, weed biomass, and seed number per pod. The highest grain yields (3838 kg ha-1) were recorded for No-till row crop seeding. The highest seed yield (3877 kg ha-1) also was recorded for weed control with herbicide and hand weeding treatment, followed by hand weeding (3379 kg ha-1).

  1. Effect of tillage system on yield and weed populations of soybean ( Glycin Max L.

    Directory of Open Access Journals (Sweden)

    Seyed Z. Hosseini

    2016-03-01

    Full Text Available Field experiment was conducted at Agricultural and Natural Resources Research Center of Golestan Province, Iran, to determine the effects of tillage system and weed management regime on yield and weed populations in soybean ( Glycin max L.. The experimental design was a split plot where the whole plot portion was a randomized complete block with three replicates. Main plots were tillage system: 1- No-till row crop seeding, 2- No-till seed drilling, 3- Tillage with disc harrow and drill planting, 4- Tillage with chisel packer and drill planting. The subplots were weed management regimes: 1-Weed control with herbicide application, 2- Hand weeding, 3- Herbicide application plus hand weeding, and 4- Non-weeding. Results indicated that the main effects of tillage system and weed management regime were significant for seed yield, pod number per plant, seed number per pod, weed density and biomass, while their interaction were significant only for weed density, weed biomass, and seed number per pod. The highest grain yields (3838 kg ha-1 were recorded for No-till row crop seeding. The highest seed yield (3877 kg ha-1 also was recorded for weed control with herbicide and hand weeding treatment, followed by hand weeding (3379 kg ha-1.

  2. Water use efficiency of cassava plants under competition conditions Eficiência do uso da água de plantas de mandioca em condições de competição

    Directory of Open Access Journals (Sweden)

    I Aspiazú

    2010-12-01

    Full Text Available The objective of this work was to evaluate characteristics associated with the photosynthetic activity of cassava plants in competition with weeds or not. The trial was performed on open environment conditions, with experimental units consisting of fiber glass vases with 150 dm³ filled with Red Yellow Latosol, previously fertilized. Treatments consisted in the cultivation of cassava plants isolated and associated to three weed species (Bidens pilosa, Commelina benghalensis and Brachiaria plantaginea. After cassava shooting, 15 days after planting, a removal of the weeds excess was performed, sown at the time of cassava planting, leaving six plants m-2 of B. pilosa and four plants m-2 of C. benghalensis and B. plantaginea. At 60 days after emergence (DAE, stomatal conductance (Gs, vapor pressure in the substomatal cavity (Ean, temperature gradient between leaf and air (ΔT, transpiration rate (E and water use efficiency (WUE were evaluated. B. pilosa showed greater capacity to affect growth of cassava plants. B. plantaginea is very efficient in using water, especially by presenting C4 metabolism, and remains competitive with cassava even under temporarily low water status. C. benghalensis, in turn, is not a good competitor for light and apparently is not the primary cause of water depletion in the soil. The effects of weeds, in this case, were more associated with the competition. However, they were found between moderate to low. This implies that the competition established at experimental level was low.Objetivou-se com este trabalho avaliar características associadas à eficiência de uso da água de plantas de mandioca sob competição ou não com plantas daninhas. O experimento foi realizado em condições de ambiente aberto, sendo as unidades experimentais compostas por vasos de fibra de vidro de 150 dm³preenchidos com Latossolo Vermelho Amarelo, previamente adubado. Os tratamentos consistiram no cultivo de plantas de mandioca isoladas e

  3. Glyphosate Resistance of C3 and C4 Weeds under Rising Atmospheric CO2.

    Science.gov (United States)

    Fernando, Nimesha; Manalil, Sudheesh; Florentine, Singarayer K; Chauhan, Bhagirath S; Seneweera, Saman

    2016-01-01

    The present paper reviews current knowledge on how changes of plant metabolism under elevated CO2 concentrations (e[CO2]) can affect the development of the glyphosate resistance of C3 and C4 weeds. Among the chemical herbicides, glyphosate, which is a non-selective and post-emergence herbicide, is currently the most widely used herbicide in global agriculture. As a consequence, glyphosate resistant weeds, particularly in major field crops, are a widespread problem and are becoming a significant challenge to future global food production. Of particular interest here it is known that the biochemical processes involved in photosynthetic pathways of C3 and C4 plants are different, which may have relevance to their competitive development under changing environmental conditions. It has already been shown that plant anatomical, morphological, and physiological changes under e[CO2] can be different, based on (i) the plant's functional group, (ii) the available soil nutrients, and (iii) the governing water status. In this respect, C3 species are likely to have a major developmental advantage under a CO2 rich atmosphere, by being able to capitalize on the overall stimulatory effect of e[CO2]. For example, many tropical weed grass species fix CO2 from the atmosphere via the C4 photosynthetic pathway, which is a complex anatomical and biochemical variant of the C3 pathway. Thus, based on our current knowledge of CO2 fixing, it would appear obvious that the development of a glyphosate-resistant mechanism would be easier under an e[CO2] in C3 weeds which have a simpler photosynthetic pathway, than for C4 weeds. However, notwithstanding this logical argument, a better understanding of the biochemical, genetic, and molecular measures by which plants develop glyphosate resistance and how e[CO2] affects these measures will be important before attempting to innovate sustainable technology to manage the glyphosate-resistant evolution of weeds under e[CO2]. Such information will be of

  4. Arbuscular mycorrhizal fungi reduce the differences in competitiveness between dominant and subordinate plant species.

    Science.gov (United States)

    Mariotte, Pierre; Meugnier, Claire; Johnson, David; Thébault, Aurélie; Spiegelberger, Thomas; Buttler, Alexandre

    2013-05-01

    In grassland communities, plants can be classified as dominants or subordinates according to their relative abundances, but the factors controlling such distributions remain unclear. Here, we test whether the presence of the arbuscular mycorrhizal (AM) fungus Glomus intraradices affects the competitiveness of two dominant (Taraxacum officinale and Agrostis capillaris) and two subordinate species (Prunella vulgaris and Achillea millefolium). Plants were grown in pots in the presence or absence of the fungus, in monoculture and in mixtures of both species groups with two and four species. In the absence of G. intraradices, dominants were clearly more competitive than subordinates. In inoculated pots, the fungus acted towards the parasitic end of the mutualism-parasitism continuum and had an overall negative effect on the growth of the plant species. However, the negative effects of the AM fungus were more pronounced on dominant species reducing the differences in competitiveness between dominant and subordinate species. The effects of G. intraradices varied with species composition highlighting the importance of plant community to mediate the effects of AM fungi. Dominant species were negatively affected from the AM fungus in mixtures, while subordinates grew identically with and without the fungus. Therefore, our findings predict that the plant dominance hierarchy may flatten out when dominant species are more reduced than subordinate species in an unfavourable AM fungal relationship (parasitism).

  5. Source selection problem of competitive power plants under government intervention: a game theory approach

    Science.gov (United States)

    Mahmoudi, Reza; Hafezalkotob, Ashkan; Makui, Ahmad

    2014-06-01

    Pollution and environmental protection in the present century are extremely significant global problems. Power plants as the largest pollution emitting industry have been the cause of a great deal of scientific researches. The fuel or source type used to generate electricity by the power plants plays an important role in the amount of pollution produced. Governments should take visible actions to promote green fuel. These actions are often called the governmental financial interventions that include legislations such as green subsidiaries and taxes. In this paper, by considering the government role in the competition of two power plants, we propose a game theoretical model that will help the government to determine the optimal taxes and subsidies. The numerical examples demonstrate how government could intervene in a competitive market of electricity to achieve the environmental objectives and how power plants maximize their utilities in each energy source. The results also reveal that the government's taxes and subsidiaries effectively influence the selected fuel types of power plants in the competitive market.

  6. Effect of vermicast generated from an allelopathic weed lantana (Lantana camara) on seed germination, plant growth, and yield of cluster bean (Cyamopsis tetragonoloba).

    Science.gov (United States)

    Karthikeyan, M; Hussain, N; Gajalakshmi, S; Abbasi, S A

    2014-11-01

    In perhaps the first-ever study of its kind, the effect of vermicompost, derived solely from an allelopathic weed, on the germination, growth, and yield of a botanical species, has been carried out. In test plots, the soil was treated with the vermicompost of lantana (Lantana camara) at the rates of 5, 7.5, and 10 t ha(-1), and cluster bean (Cyamopsis tetragonoloba) was grown on it. The performance of these systems was compared with the systems in which the soil was fortified with inorganic fertilizers (IFs) in concentrations equivalent to those present in the respective vermicompost (VC) treatments. Additionally, a set of control was studied in which the soil was used without fortification by either VC or IF. It was seen that up to 51.5 % greater germination success occurred in the VC treatments compared to controls. VC also supported better plant growth in terms of stem diameter, shoot length, shoot mass, number of leaves, and leaf pigments. The positive impact extended up to fruit yield. In addition, vermicast application enhanced root nodule formation, reduced disease incidence, and allowed for a smaller number of stunted plants. The results indicate that allelopathic ingredients of lantana seem to have been totally eliminated during the course of its vermicomposting and that lantana vermicompost has the potential to support germination, growth, and fruit yield better than equivalent quantities of IFs.

  7. Soil solarization for weed control in carrot

    Directory of Open Access Journals (Sweden)

    MARENCO RICARDO ANTONIO

    2000-01-01

    Full Text Available Soil solarization is a technique used for weed and plant disease control in regions with high levels of solar radiation. The effect of solarization (0, 3, 6, and 9 weeks upon weed populations, carrot (Daucus carota L. cv. Brasília yield and nematode infestation in carrot roots was studied in São Luís (2º35' S; 44º10' W, MA, Brazil, using transparent polyethylene films (100 and 150 mm of thickness. The maximum temperature at 5 cm of depth was about 10ºC warmer in solarized soil than in control plots. In the study 20 weed types were recorded. Solarization reduced weed biomass and density in about 50% of weed species, including Cyperus spp., Chamaecrista nictans var. paraguariensis (Chod & Hassl. Irwin & Barneby, Marsypianthes chamaedrys (Vahl O. Kuntze, Mitracarpus sp., Mollugo verticillata L., Sebastiania corniculata M. Arg., and Spigelia anthelmia L. Approximately 40% of species in the weed flora were not affected by soil mulching. Furthermore, seed germination of Commelina benghalensis L. was increased by soil solarization. Marketable yield of carrots was greater in solarized soil than in the unsolarized one. It was concluded that solarization for nine weeks increases carrot yield and is effective for controlling more than half of the weed species recorded. Mulching was not effective for controlling root-knot nematodes in carrot.

  8. Resource and competitive dynamics shape the benefits of public goods cooperation in a plant pathogen.

    Science.gov (United States)

    Platt, Thomas G; Fuqua, Clay; Bever, James D

    2012-06-01

    Cooperative benefits depend on a variety of ecological factors. Many cooperative bacteria increase the population size of their groups by making a public good available. Increased local population size can alleviate the constraints of kin competition on the evolution of cooperation by enhancing the between-group fitness of cooperators. The cooperative pathogenesis of Agrobacterium tumefaciens causes infected plants to exude opines--resources that provide a nearly exclusive source of nutrient for the pathogen. We experimentally demonstrate that opines provide cooperative A. tumefaciens cells a within-group fitness advantage over saprophytic agrobacteria. Our results are congruent with a resource-consumer competition model, which predicts that cooperative, virulent agrobacteria are at a competitive disadvantage when opines are unavailable, but have an advantage when opines are available at sufficient levels. This model also predicts that freeloading agrobacteria that catabolize opines but cannot infect plants competitively displace the cooperative pathogen from all environments. However, we show that these cooperative public goods also promote increased local population size. A model built from the Price Equation shows that this effect on group size can contribute to the persistence of cooperative pathogenesis despite inherent kin competition for the benefits of pathogenesis.

  9. Effects of clonal fragmentation on intraspecific competition of a stoloniferous floating plant.

    Science.gov (United States)

    Wang, P; Xu, Y-S; Dong, B-C; Xue, W; Yu, F-H

    2014-11-01

    Disturbance is common and can fragment clones of plants. Clonal fragmentation may affect the density and growth of ramets so that it could alter intraspecific competition. To test this hypothesis, we grew one (low density), five (medium density) or nine (high density) parent ramets of the floating invasive plant Pistia stratiotes in buckets, and newly produced offspring ramets were either severed (with fragmentation) or remained connected to parent ramets (no fragmentation). Increasing density reduced biomass of the whole clone (i.e. parent ramet plus its offspring ramets), showing intense intraspecific competition. Fragmentation decreased biomass of offspring ramets, but increased biomass of parent ramets and the whole clone, suggesting significant resource translocation from parent to offspring ramets when clones were not fragmented. There was no interaction effect of density x fragmentation on biomass of the whole clone, and fragmentation did not affect competition intensity index. We conclude that clonal fragmentation does not alter intraspecific competition between clones of P. stratiotes, but increases biomass production of the whole clone. Thus, fragmentation may contribute to its interspecific competitive ability and invasiveness, and intentional fragmentation should not be recommended as a measure to stop the rapid growth of this invasive species. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

  10. RNAseq reveals weed-induced PIF3-like as a candidate target to manipulate weed stress response in soybean.

    Science.gov (United States)

    Horvath, David P; Hansen, Stephanie A; Moriles-Miller, Janet P; Pierik, Ronald; Yan, Changhui; Clay, David E; Scheffler, Brian; Clay, Sharon A

    2015-07-01

    Weeds reduce yield in soybeans (Glycine max) through incompletely defined mechanisms. The effects of weeds on the soybean transcriptome were evaluated in field conditions during four separate growing seasons. RNASeq data were collected from six biological samples of soybeans growing with or without weeds. Weed species and the methods to maintain weed-free controls varied between years to mitigate treatment effects, and to allow detection of general soybean weed responses. Soybean plants were not visibly nutrient- or water-stressed. We identified 55 consistently downregulated genes in weedy plots. Many of the downregulated genes were heat shock genes. Fourteen genes were consistently upregulated. Several transcription factors including a PHYTOCHROME INTERACTING FACTOR 3-like gene (PIF3) were included among the upregulated genes. Gene set enrichment analysis indicated roles for increased oxidative stress and jasmonic acid signaling responses during weed stress. The relationship of this weed-induced PIF3 gene to genes involved in shade avoidance responses in Arabidopsis provide evidence that this gene may be important in the response of soybean to weeds. These results suggest that the weed-induced PIF3 gene will be a target for manipulating weed tolerance in soybean.

  11. Simulating changes in cropping practises in conventional and glyphosate-tolerant maize. I. Effects on weeds.

    Science.gov (United States)

    Colbach, Nathalie; Fernier, Alice; Le Corre, Valérie; Messéan, Antoine; Darmency, Henri

    2017-04-01

    Herbicide-tolerant (HT) crops such as those tolerant to glyphosate simplify weed management and make it more efficient, at least at short-term. Overreliance on the same herbicide though leads to the spread of resistant weeds. Here, the objective was to evaluate, with simulations, the impact on the advent of glyphosate resistance in weeds of modifications in agricultural practises resulting from introducing HT maize into cropping systems. First, we included a single-gene herbicide resistance submodel in the existing multispecific FLORSYS model. Then, we (1) simulated current conventional and probable HT cropping systems in two European regions, Aquitaine and Catalonia, (2) compared these systems in terms of glyphosate resistance, (3) identified pertinent cultural practises influencing glyphosate resistance, and (4) investigated correlations between cultural practises and species traits, using RLQ analyses. The simulation study showed that, during the analysed 28 years, (1) glyphosate spraying only results in glyphosate resistance in weeds when combined with other cultural factors favouring weed infestation, particularly no till; (2) pre-sowing glyphosate applications select more for herbicide resistance than post-sowing applications on HT crops; and (3) glyphosate spraying selects more for species traits avoiding exposure to the herbicide (e.g. delayed early growth, small leaf area) or compensating for fitness costs (e.g. high harvest index) than for actual resistance to glyphosate, (4) actual resistance is most frequent in species that do not avoid glyphosate, either via plant size or timing, and/or in less competitive species, (5) in case of efficient weed control measures, actual resistance proliferates best in outcrossing species. An advice table was built, with the quantitative, synthetic ranking of the crop management effects in terms of glyphosate-resistance management, identifying the optimal choices for each management technique.

  12. Changes in Soil Biota Resulting from Growth of the Invasive Weed, Ambrosia artemisiifolia L. (Compositae), Enhance Its Success and Reduce Growth of Co-Occurring Plants

    Institute of Scientific and Technical Information of China (English)

    LI Hui-na,XIAO Bo,LIU Wan-xue; WAN Fang-hao

    2014-01-01

    Exotic plant invasion presents a serious threat to native ecosystem structure and function. Little is known about the role of soil microbial communities in facilitating or resisting the spread of invasive plants into native communities. The purpose of this research is to understand how the invasive annual plantAmbrosiaartemisiifoliaL. facilitates its competition capacity through changing the structure and function of soil microbial communities.The soil characteristics of different areas invaded by A. artemisiifolia were examined. Greenhouse experiments were designed to assess the effect ofA. artemisiifolia invasion-induced changes of soil biota on co-occurring plant growth, and on the interactions betweenA. artemisiifoliaand three co-occurring plant species. The results showed that the soil organic C content was the highest in heavily invaded sites, the lowest in native plant sites, and intermediate in newly invaded sites. Soil available N, P and K concentrations in heavily invaded site were 2.4, 1.9 and 1.7 times higher than those in native plant soil, respectively. Soil pH decreased asA. artemisiifoliainvasion intensity increased, and was lower in invaded sites (heavily invaded and newly invaded) than in native plant sites. The soil microbial community structure was clearly separated in the three types of sites, andA. artemisiifoliainvasion increased anaerobe, sulfate-reducing bacteria and actinomycete abundance. Soil biota of invaded sites inhibits growth of co-occurring plants (Galinsoga parvilfora Cav.,Medicago sativaL. andSetaria plicata (Lam.) T. Cooke.) compared to soil biota from un-invaded sites, but facilitates A. artemisiifoliagrowth and competition with co-occurring plants.A. artemisiifolia biomass was 50-130% greater when competing with three co-occurring plants,compared to single-species competition only (invasion byA. artemisiifoliaalone), in heavily invaded soil. Results of the present study indicated thatA. artemisiifolia invasion alters the soil

  13. Arbuscular mycorrhizal fungi alter the competitive hierarchy among old-field plant species.

    Science.gov (United States)

    Stanescu, Sabina; Maherali, Hafiz

    2017-02-01

    Inoculation with arbuscular mycorrhizal (AM) fungi is known to increase the species diversity of plant communities. One mechanism that can increase the likelihood of species co-existence, and thus species diversity, is a trade-off between competitive ability and the magnitude of plant growth response to AM fungal inoculation. By suppressing the growth of strong competitors while simultaneously enhancing the growth of weak competitors, this trade-off would cause the competitive hierarchy to be less pronounced in soil inoculated with AM fungi relative to non-inoculated conditions. To test whether such a trade-off exists, we quantified competitive abilities and mycorrhizal growth response (MGR) among 21 species that co-occur in old fields in southern Ontario. Competitive ability was determined by calculating competitive effect (CE), or the degree to which each species suppressed the biomass of a common phytometer species, Plantago lanceolata. Higher CE values represent stronger competitive ability. Old-field species varied in their ability to suppress the biomass of the phytometer and MGR was generally positive. There was a statistically significant negative correlation between CE in non-inoculated soil and MGR (r = -0.49, P = 0.02). In addition, variance in CE was 73% lower in soil inoculated with AM fungi compared to non-inoculated soil (P = 0.0023). These findings support the hypothesis that AM fungi weaken strong competitors while enhancing the performance of weak competitors. Because this trade-off compressed the competitive hierarchy among old-field species in soil inoculated with AM fungi, it may be a mechanism by which mycorrhizal fungi enhance species evenness and diversity.

  14. Benefits of Precision Farming Technologies for Mechanical Weed Control in Soybean and Sugar Beet—Comparison of Precision Hoeing with Conventional Mechanical Weed Control

    Directory of Open Access Journals (Sweden)

    Christoph Kunz

    2015-04-01

    Full Text Available Weed infestations and associated yield losses require effective weed control measures in soybean and sugar beet. Besides chemical weed control, mechanical weeding plays an important role in integrated weed management systems. Field experiments were conducted at three locations for soybean in 2013 and 2014 and at four locations for sugar beet in 2014 to investigate if automatic steering technologies for inter-row weed hoeing using a camera or RTK-GNSS increase weed control efficacy, efficiency and crop yield. Treatments using precision farming technologies were compared with conventional weed control strategies. Weed densities in the experiments ranged from 15 to 154 plants m−2 with Chenopodium album, Polygonum convolvulus, Polygonum aviculare, Matricaria chamomilla and Lamium purpureum being the most abundant species. Weed hoeing using automatic steering technologies reduced weed densities in soybean by 89% and in sugar beet by 87% compared to 85% weed control efficacy in soybean and sugar beet with conventional weeding systems. Speed of weed hoeing could be increased from 4 km h−1 with conventional hoes to 7 and 10 km·h−1, when automatic steering systems were used. Precision hoeing technologies increased soybean yield by 23% and sugar beet yield by 37%. After conventional hoeing and harrowing, soybean yields were increased by 28% and sugar beet yield by 26%.

  15. Do plant traits predict the competitive abilities of closely related species?

    Science.gov (United States)

    Schwartz, Lauren M; Gibson, David J; Young, Bryan G

    2015-12-31

    Invasive species are a threat to every ecosystem. There is a strong incentive to predict which species will become invasive before they become too widespread and unmanageable. Different approaches have been advocated to assess invasive species potential. These include examining plant functional traits, quantifying competitive ability and phylogenetic comparison. In this study, we conducted experiments based on the above approaches in a multi-year, temporally replicated, set of experiments to compare these assessment methods to determine the invasive potential of Japanese chaff flower (Achyranthes japonica). We compared plant traits and competitive ability of Japanese chaff flower with two agricultural invasive species, Palmer amaranth (Amaranthus palmeri) and tall waterhemp (Amaranthus tuberculatus), and one endangered plant species, bloodleaf (Iresine rhizomatosa), in the Amaranthaceae. Additionally, we assessed the invasive potential based on each of these approaches and determined the degree of agreement between them. A relatively conservative assessment integrating all three approaches would be that the competitive ability of closely related individuals with similar functional traits would share invasive potential. In a greenhouse experiment, each of the study species and soya beans were grown as monocultures and were evaluated to assess the drawdown of an aboveground (light) and a belowground (nitrogen) resource. In a field experiment, each study species was grown at varying densities per 15-cm-diameter pot with or without one or two soya bean plants, to simulate relative densities for soya beans grown in 38- and 76-cm-wide row spacing, respectively. In addition, Japanese chaff flower seedlings were planted either as un-manipulated seedlings or as a seedling cut back to the soil surface at the four-node stage (cut Japanese chaff flower) at which point seedlings have reached a perennial growth stage. The greenhouse experiment showed that each species drew down

  16. Thiamethoxam as a seed treatment alters the physiological response of maize (Zea mays) seedlings to neighbouring weeds.

    Science.gov (United States)

    Afifi, Maha; Lee, Elizabeth; Lukens, Lewis; Swanton, Clarence

    2015-04-01

    Thiamethoxam is a broad-spectrum neonicotinoid insecticide that, when applied to seed, has been observed to enhance seedling vigour under environmental stress conditions. Stress created by the presence of neighbouring weeds is known to trigger the accumulation of hydrogen peroxide (H2 O2 ) in maize seedling tissue. No previous work has explored the effect of thiamethoxam as a seed treatment on the physiological response of maize seedlings emerging in the presence of neighbouring weeds. Thiamethoxam was found to enhance seedling vigour and to overcome the expression of typical shade avoidance characteristics in the presence of neighbouring weeds. These results were attributed to maintenance of the total phenolics content, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity and anthocyanin and lignin contents. These findings were also associated with the activation of scavenging genes, which reduced the accumulation of H2 O2 and the subsequent damage caused by lipid peroxidation in maize seedlings originating from treated seeds even when exposed to neighbouring weeds. These results suggest the possibility of exploring new chemistries and modes of action as novel seed treatments to upregulate free radical scavenging genes and to maintain the antioxidant system within plants. Such an approach may provide an opportunity to enhance crop competitiveness with weeds. © 2014 Society of Chemical Industry.

  17. Microwave Technologies as Part of an Integrated Weed Management Strategy: A Review

    Directory of Open Access Journals (Sweden)

    Graham Brodie

    2012-01-01

    Full Text Available Interest in controlling weed plants using radio frequency or microwave energy has been growing in recent years because of the growing concerns about herbicide resistance and chemical residues in the environment. This paper reviews the prospects of using microwave energy to manage weeds. Microwave energy effectively kills weed plants and their seeds; however, most studies have focused on applying the microwave energy over a sizable area, which requires about ten times the energy that is embodied in conventional chemical treatments to achieve effective weed control. A closer analysis of the microwave heating phenomenon suggests that thermal runaway can reduce microwave weed treatment time by at least one order of magnitude. If thermal runaway can be induced in weed plants, the energy costs associated with microwave weed management would be comparable with chemical weed control.

  18. Relative competitiveness of soybean cultivars with barnyardgrass

    Directory of Open Access Journals (Sweden)

    Marlon Ouriques Bastiani

    Full Text Available ABSTRACT The aim of this work was to evaluate the competitiveness between soybean cultivars and barnyardgrass, based on morphological and physiological characteristics of species. The experiments were conducted in completely randomized experimental design, with 4 replications. In the first study, for both soybean and barnyardgrass, it was determined the population of plants in which shoot dry matter became constant and independent of the population (16 plants∙pot−1 or 400 plants∙m−2. In the second study, 2 experiments were conducted to evaluate the competitiveness of BMX Apolo RR and BMX Potência RR soybean cultivars with barnyardgrass plants, both carried out in replacement series under different proportions of plants∙pot−1 (100:0; 75:25; 50:50; 25:75 and 0:100 between the crop and the weed. The analysis of the species competitiveness was determined through diagrams applied to replacement series experiments and use of relative competitiveness indexes. At 44 days after the emergence of species, the physiological and morphological parameters of the crop and the weed were evaluated. The BMX Apolo RR and BMX Potência RR soybean cultivars show similar competitiveness when competing with the barnyardgrass; therefore, the ability of one species to interfere on another is equivalent. For plant height, barnyardgrass displays higher competitiveness compared to BMX Apolo RR, with early cycle and short height. The intraspecific competition is more important to barnyardgrass than interspecific competition with soybean cultivars, resulting in negative effects on the morphological and physiological characteristics of species.

  19. WHITE BLISTER SPECIES (Albuginaceae ON WEEDS

    Directory of Open Access Journals (Sweden)

    Karolina Vrandečić

    2011-06-01

    Full Text Available The obligate fungi inside the family Albuginaceae are widespread world wide and cause white rust or white blister disease. Mycopopulation of weeds has been researched within the project „The role of weeds in epidemiology of row-crop diseases“. The aim of this research was to identify white blister species occurring on weeds in Eastern Croatia. Weed plants with disease symptoms characteristic for white blister species have been collected since 2001 on location Slavonia and Baranja country. Determination of white blister species was based on morphological characters of pathogen and the host. Wilsoniana bliti was determined on Amaranthus retroflexus and Amaranthus hybridus leaves. Capsella bursa pastoris is a host for Albugo candida. Ambrosia artemisiifolia is a host for Pustula sp. and Cirsium arvense was found to be host for Pustula spinulosa. Wilsoniana portulaceae was determined on Portulaca oleracea.

  20. Becoming weeds.

    Science.gov (United States)

    Stewart, C Neal

    2017-04-26

    A new resequencing analysis of weedy rice (Oryza sativa L.) biotypes illuminates distinct evolutionary paths and outcomes of de-domestication and ferality. This largest effort to date in weedy plant genomics gives a better understanding of weediness while also providing a promising source of alleles for rice breeding.

  1. Understanding Lolium rigidum Seeds: The Key to Managing a Problem Weed?

    Directory of Open Access Journals (Sweden)

    Kathryn J. Steadman

    2012-09-01

    Full Text Available The 40 million hectare southern Australian winter cropping region suffers from widespread infestation by Lolium rigidum (commonly known as annual or rigid ryegrass, a Mediterranean species initially introduced as a pasture plant. Along with its high competitiveness within crops, rapid adaptability and widespread resistance to herbicides, the dormancy of its seeds means that L. rigidum is the primary weed in southern Australian agriculture. With the individuals within a L. rigidum population exhibiting varying levels of seed dormancy, germination can be staggered across the crop-growing season, making complete weed removal virtually impossible, and ensuring that the weed seed bank is constantly replenished. By understanding the processes involved in induction and release of dormancy in L. rigidum seeds, it may be possible to develop strategies to more effectively manage this pest without further stretching herbicide resources. This review examines L. rigidum seed dormancy and germination from a weed-management perspective and explains how the seed bank can be depleted by control strategies encompassing all stages in the lifecycle of a seed, from development to germination.

  2. Spatial and temporal distribution of weeds in no-tillage system

    Directory of Open Access Journals (Sweden)

    Eduardo L. Bottega

    Full Text Available ABSTRACT Brazil is one of the largest grain producers in the world, due to its extensive arable land and favorable climate for the cultivation of any species. The production could be higher, but problems such as competition between crops and weeds reduces crop yields. This study aimed to analyze the spatial distribution of weeds, especially milkweed (Sonchus oleraceus, horse weed (Conyza spp. and ‘maria-mole’ (Senecio brasiliensis in an area under no-tillage system for two harvests. The work was carried out during the 2013/14 and 2014/15 crop years in an area of 22.5 ha, where soybean is grown in the summer and oat in the winter. The weeds were mapped using a sampling grid of 85 points. The number of plants present in 0.25 m2 was recorded at each sampling point. The data collected in the field composed the information bank and were used for geostatistical analysis and production of maps. Using geostatistical analysis, it was possible to map the horseweed infestation in the studied area for the 2013/14 season. The species ‘maria-mole’ and milkweed did not show spatial dependence. During the 2014/2015 season, because of the management carried out in the off season, none of the studied species showed spatial dependence.

  3. Impact of the timing and duration of weed control on the establishment of a rubber tree plantation.

    Science.gov (United States)

    Guzzo, Caio D; Carvalho, Leonardo B de; Giancotti, Paulo R F; Alves, Pedro L C A; Gonçalves, Elaine C P; Martins, José V F

    2014-03-01

    Rubber tree production is reduced by weeds that compete for environmental resources; therefore, the timing and duration of weed control influences weed interference. The objectives of this study were to evaluate the growth of rubber tree (Hevea brasiliensis) plants, to determine the critical period for weed control, and to evaluate the growth recovery of rubber trees that coexisted with weeds for different periods of time after planting. Two groups of treatments were established under field conditions in the first year of the investigation: one group contained crescent periods of weed infestation, while the other contained crescent periods of weed control, also including a weed-free check and a total weedy check. In the second year of the investigation, the weeds were totally controlled. Urochloa decumbens was the dominant weed (over 90% groundcover). Crop growth was greatly reduced due to the weed interference. Plant height decreased more rapidly than did any other characteristic. Plant height, leaf dry mass, and leaf area decreased by 99%, 97% and 96%, respectively, and were the most reduced characteristics. Plant height also recovered more rapidly than did any characteristic when the period of weed control was lengthened. However, stem dry mass increased by 750%, making it the most recovered characteristic. The critical period for weed control was between 4 and 9½ months after planting in the first year; however, the rubber trees showed an expressive growth recovery when the weeds were controlled throughout the second year.

  4. Impact of the timing and duration of weed control on the establishment of a rubber tree plantation

    Directory of Open Access Journals (Sweden)

    CAIO D. GUZZO

    2014-03-01

    Full Text Available Rubber tree production is reduced by weeds that compete for environmental resources; therefore, the timing and duration of weed control influences weed interference. The objectives of this study were to evaluate the growth of rubber tree (Hevea brasiliensis plants, to determine the critical period for weed control, and to evaluate the growth recovery of rubber trees that coexisted with weeds for different periods of time after planting. Two groups of treatments were established under field conditions in the first year of the investigation: one group contained crescent periods of weed infestation, while the other contained crescent periods of weed control, also including a weed-free check and a total weedy check. In the second year of the investigation, the weeds were totally controlled. Urochloa decumbens was the dominant weed (over 90% groundcover. Crop growth was greatly reduced due to the weed interference. Plant height decreased more rapidly than did any other characteristic. Plant height, leaf dry mass, and leaf area decreased by 99%, 97% and 96%, respectively, and were the most reduced characteristics. Plant height also recovered more rapidly than did any characteristic when the period of weed control was lengthened. However, stem dry mass increased by 750%, making it the most recovered characteristic. The critical period for weed control was between 4 and 9½ months after planting in the first year; however, the rubber trees showed an expressive growth recovery when the weeds were controlled throughout the second year.

  5. Conspecific flowers of Sinapis arvensis are stronger competitors for pollinators than those of the invasive weed Bunias orientalis.

    Science.gov (United States)

    Hochkirch, Axel; Mertes, Tamara; Rautenberg, Julia

    2012-03-01

    Biological invasions can affect the structure and function of ecosystems and threaten native plant species. Since most weeds rely on mutualistic relationships in their new environment, they may act as new competitors for pollinators. Pollinator competition is likely to be density dependent, but it is often difficult to disentangle competition caused by flower quality from effects caused by flower quantity. In order to test the effects of the presence and number of flowers of the invasive weed Bunias orientalis on the insect visitation rates in a native species (Sinapis arvensis), we performed two replacement experiments using plants with standardised flower numbers. The visitation rates in S. arvensis were significantly higher than in B. orientalis and the number of insect visits dropped significantly with increasing density of S. arvensis flowers. These results suggest that intraspecific competition among flowers of S. arvensis is stronger than the competitive effect of alien flowers. As flowers of B. orientalis do not seem to distract visitors from S. arvensis, it is unlikely that pollinator competition between these two plant species plays a crucial role. However, it cannot be excluded that mass blossom stands of B. orientalis may distract flower visitors from nativespecies.

  6. Conspecific flowers of Sinapis arvensis are stronger competitors for pollinators than those of the invasive weed Bunias orientalis

    Science.gov (United States)

    Hochkirch, Axel; Mertes, Tamara; Rautenberg, Julia

    2012-03-01

    Biological invasions can affect the structure and function of ecosystems and threaten native plant species. Since most weeds rely on mutualistic relationships in their new environment, they may act as new competitors for pollinators. Pollinator competition is likely to be density dependent, but it is often difficult to disentangle competition caused by flower quality from effects caused by flower quantity. In order to test the effects of the presence and number of flowers of the invasive weed Bunias orientalis on the insect visitation rates in a native species ( Sinapis arvensis), we performed two replacement experiments using plants with standardised flower numbers. The visitation rates in S. arvensis were significantly higher than in B. orientalis and the number of insect visits dropped significantly with increasing density of S. arvensis flowers. These results suggest that intraspecific competition among flowers of S. arvensis is stronger than the competitive effect of alien flowers. As flowers of B. orientalis do not seem to distract visitors from S. arvensis, it is unlikely that pollinator competition between these two plant species plays a crucial role. However, it cannot be excluded that mass blossom stands of B. orientalis may distract flower visitors from native species.

  7. Root secreted metabolites and proteins are involved in the early events of plant-plant recognition prior to competition.

    Directory of Open Access Journals (Sweden)

    Dayakar V Badri

    Full Text Available The mechanism whereby organisms interact and differentiate between others has been at the forefront of scientific inquiry, particularly in humans and certain animals. It is widely accepted that plants also interact, but the degree of this interaction has been constricted to competition for space, nutrients, water and light. Here, we analyzed the root secreted metabolites and proteins involved in early plant neighbor recognition by using Arabidopsis thaliana Col-0 ecotype (Col as our focal plant co-cultured in vitro with different neighbors [A. thaliana Ler ecotype (Ler or Capsella rubella (Cap]. Principal component and cluster analyses revealed that both root secreted secondary metabolites and proteins clustered separately between the plants grown individually (Col-0, Ler and Cap grown alone and the plants co-cultured with two homozygous individuals (Col-Col, Ler-Ler and Cap-Cap or with different individuals (Col-Ler and Col-Cap. In particularly, we observed that a greater number of defense- and stress-related proteins were secreted when our control plant, Col, was grown alone as compared to when it was co-cultured with another homozygous individual (Col-Col or with a different individual (Col-Ler and Col-Cap. However, the total amount of defense proteins in the exudates of the co-cultures was higher than in the plant alone. The opposite pattern of expression was identified for stress-related proteins. These data suggest that plants can sense and respond to the presence of different plant neighbors and that the level of relatedness is perceived upon initial interaction. Furthermore, the role of secondary metabolites and defense- and stress-related proteins widely involved in plant-microbe associations and abiotic responses warrants reassessment for plant-plant interactions.

  8. Yield loss prediction models based on early estimation of weed pressure

    DEFF Research Database (Denmark)

    Asif, Ali; Streibig, Jens Carl; Andreasen, Christian

    2013-01-01

    Weed control thresholds have been used to reduce costs and avoid unacceptable yield loss. Estimation of weed infestation has often been based on counts of weed plants per unit area or measurement of their relative leaf area index. Various linear, hyperbolic, and sigmoidal regression models have...... been proposed to predict yield loss, relative to yield in weed free environment from early measurements of weed infestation. The models are integrated in some weed management advisory systems. Generally, the recommendations from the advisory systems are applied to the whole field, but weed control...... time of weeds relative to crop. The aim of the review is to analyze various approaches to estimate infestation of weeds and the literature about yield loss prediction for multispecies. We discuss limitations of regression models and possible modifications to include the influential factors related...

  9. Activity of mesotrione on resistant weeds in maize.

    Science.gov (United States)

    Sutton, Peter; Richards, Claire; Buren, Larry; Glasgow, Les

    2002-09-01

    Mesotrione is a new callistemone herbicide that inhibits the HPPD enzyme (p-hydroxyphenylpyruvate dioxygenase) and introduces a new naturally selective tool into weed-management programmes for use in maize. Mesotrione provides control of the major broad-leaved weeds, and it can be used in integrated weed-management programmes depending on the grower's preferred weed-control strategy. At post-emergence rates of 150 g AI ha-1 or less, mesotrione provides naturally selective control of key species that may show triazine resistance (TR), e.g. Chenopodium album L, Amaranthus species, Solanum nigrum L, as well as species of weed that show resistance to acetolactase synthase (ALS) inhibitors e.g. Xanthium strumarium L, Amaranthus spp and Sonchus spp. The data presented show that resistant and susceptible biotypes of these species with resistance to triazine herbicides, such as atrazine, simazine, terbutylazine and metribuzin, or ALS-inhibitor herbicides, such as imazethepyr, remain susceptible to mesotrione. These results confirm that there is no cross-resistance in biotypes with target site resistance to triazine or ALS-inhibiting herbicides. It is important that herbicide choice and rotation becomes an integral part of planning weed management, so as to minimise the risks of crop losses from weed competition, build-up of weed seed in the soil and the further development of weed resistance across a range of herbicide modes of action.

  10. Soil Minerals: AN Overlooked Mediator of Plant-Microbe Competition for Organic Nitrogen in the Rhizosphere

    Science.gov (United States)

    Grandy, S.; Jilling, A.; Keiluweit, M.

    2016-12-01

    Recent research on the rate limiting steps in soil nitrogen (N) availability have shifted in focus from mineralization to soil organic matter (SOM) depolymerization. To that end, Schimel and Bennett (2004) argued that together with enzymatic breakdown of polymers to monomers, microsite processes and plant-microbial competition collectively drive N cycling. Here we present new conceptual models arguing that while depolymerization is a critical first step, mineral-organic associations may ultimately regulate the provisioning of bioavailable organic N, especially in the rhizosphere. Mineral-associated organic matter (MAOM) is a rich reservoir for N in soils and often holds 5-7x more N than particulate or labile fractions. However, MAOM is considered largely unavailable to plants as a source of N due to the physicochemical forces on mineral surfaces that stabilize organic matter. We argue that in rhizosphere hotspots, MAOM is in fact a potentially mineralizable and important source of nitrogen for plants. Several biochemical strategies enable plants and microbes to compete with mineral-organic interactions and effectively access MAOM. In particular, root-deposited low molecular weight compounds in the form of root exudates facilitate the biotic and abiotic destabilization and subsequent bioavailability of MAOM. We believe that the competitive balance between the potential fates of assimilable organic N — bound to mineral surfaces or dissolved and available for assimilation — depends on the specific interaction between and properties of the clay, soil solution, mineral-bound organic matter, and microbial community. For this reason, the plant-soil-MAOM interplay is enhanced in rhizosphere hotspots relative to non-rhizosphere environments, and likely strongly regulates plant-microbe competition for N. If these hypotheses are true, we need to reconsider potential soil N cycle responses to changes in climate and land use intensity, focusing on the processes by which

  11. Weed infestation of onion in soil reduced cultivation system

    Directory of Open Access Journals (Sweden)

    Marzena Błażej-Woźniak

    2013-12-01

    Full Text Available Field experiment was conducted in the years 1998-2000 in GD Felin. The influence of no-tillage cultivation and conventional tillage with spring ploughing on weed infestation of onion was compared. In experiment four cover crop mulches (Sinapis alba L., Vicia sativa L., Phacelia tanacetifolia B., Avena sativa L. were applied. From annual weeds in weed infestation of onion in great number Matricaria chamomilla L., and Senecio vulgaris L. stepped out. and from perennial - Agropyron repens (L.P.B. Reduced soil cultivation system (no-tillage caused the significant growth of primary weed infestation of onion in comparison with conventional tillage. In all years of investigations the executed pre-sowing ploughing limited significantly the annual weeds' number in primary weed infestation. The applied mulches from cover plants limited in considerable degree the number of primary weed infestation. In all years of investigations the most weeds stepped out on control object. Among investigated cover crop mulches Vicia sativa L. and Avena sativa L. had a profitable effect on decrease of onion`s primary weed infestation. Soil cultivation system and cover crop mulches had no signi ficant residual influence on the secondary weed infestation of onion.

  12. Selective Inhibition of Plant Serine Hydrolases by Agrochemicals Revealed by Competitive ABPP

    OpenAIRE

    Kaschani, Farnusch; Nickel, Sabrina; Pandey, Bikram; Benjamin F Cravatt; Kaiser, Markus; van der Hoorn, Renier A L

    2011-01-01

    Organophosphate and –phosphonates and their thiol derivatives are often used in agroindustry as herbicides and insecticides, but their potential off-targets in the plant and their consumers are poorly investigated. Here, we use competitive Activity-based Protein Profiling (ABPP) of serine hydrolases (SHs) to detect targets of these agrochemicals and other compounds in Arabidopsis thaliana. Using broad-range and specific probes, and by overexpression of various SHs in planta, we are able to co...

  13. Interactive effects of copper pollution, competition and drought on plant growth

    DEFF Research Database (Denmark)

    Pedersen, Marianne Bruus; Kjær, C.

    Previous studies have indicated that the toxicity of copper to plants in the field is enhanced compared to single-species laboratory tests with the same soil, i.e. under similar bioavailability conditions. The purpose of the present study was to examine whether this difference in toxicity between...... laboratory and field conditions may be explained by interactions between copper toxicity and climate (drought) or competition....

  14. Competitive interactions between established grasses and woody plant seedlings under elevated CO₂ levels are mediated by soil water availability.

    Science.gov (United States)

    Manea, A; Leishman, M R

    2015-02-01

    The expansion of woody plants into grasslands has been observed worldwide and is likely to have widespread ecological consequences. One proposal is that woody plant expansion into grasslands is driven in part by the rise in atmospheric CO2 concentrations. We have examined the effect of CO2 concentration on the competitive interactions between established C4 grasses and woody plant seedlings in a model grassland system. Woody plant seedlings were grown in mesocosms together with established C4 grasses in three competition treatments (root competition, shoot competition and root + shoot competition) under ambient and elevated CO2 levels. We found that the growth of the woody plant seedlings was suppressed by competition from grasses, with root and shoot competition having similar competitive effects on growth. In contrast to expectations, woody plant seedling growth was reduced at elevated CO2 levels compared to that at the ambient CO2 level across all competition treatments, with the most plausible explanation being reduced light and soil water availability in the elevated CO2 mesocosms. Reduced light and soil water availability in the elevated CO2 mesocosms was associated with an increased leaf area index of the grasses which offset the reductions in stomatal conductance and increased rainfall interception. The woody plant seedlings also had reduced 'escapability' (stem biomass and stem height) under elevated compared to ambient CO2 levels. Our results suggest that the expansion of woody plants into grasslands in the future will likely be context-dependent, with the establishment success of woody plant seedlings being strongly coupled to the CO2 response of competing grasses and to soil water availability.

  15. A New Hoe Blade for Inter-Row Weeding

    DEFF Research Database (Denmark)

    Green, O.; Znova, L.; Melander, Bo

    2016-01-01

    , for example uncontrollable sideward soil movement causing injurious coverage of crop plants. Based on feedbacks from researchers and practioners, a new device has been designed to overcome most of the problems associated with ‘Ducksfoot’ blades. The device consists of a stiff shank mounted on a curved VCO......New camera-based systems for automatic steering of inter-row cultivators have made it possible to conduct inter-row weeding in small inter-row spaces at reasonable work rates. This has motivated organic growers to shift from full-width weed harrowing of small grain cereals to inter-row hoeing....... The aim is mainly to improve weeding effectiveness against tall-growing and tap-rooted weed species. The ‘Ducksfoot’ hoe blade is commonly used for traditional inter-row weeding in row crops such as sugar beets and maize. This blade usually provides satisfactory weed control, if soils are not too wet...

  16. Effect of ecological management of weed control on economical income, yield and yield components of cotton (Gossypium hirsutum L.

    Directory of Open Access Journals (Sweden)

    A. Zare Feizabadi

    2016-04-01

    Full Text Available In order to compare of ecological management of weed control on economical income, yield and yield components of cotton (Gossypium hirsutum L., a Randomized Complete Block design with 12 treatments and four replications was conducted in Mahvelat of Khorasan Razavi province, Iran. Treatments consisted of weeding, harrowing, burning, two times weeding, weeding + harrowing, weeding + burning, harrowing + harrowing, harrowing + weeding, harrowing + burning, weeding+ harrowing+ burning, weed free and weedy as a check treatment. Investigated traits were plant height, number of boll in plant, 20 boll weight, 20 boll cotton lint weight, cotton lint yield per plant, cotton yield, number and biomass of weeds, outcome, net and gross income. The result showed that treatments had significant effect (p

  17. Epianthropochory in Mexican weed communities.

    Science.gov (United States)

    Vibrans, H

    1999-04-01

    The diaspores of the 50 most important maize field weed species (agrestals) in a traditional maize-growing area of south-central Mexico (region of Puebla and Tlaxcala) were analyzed for morphological adaptations to long-distance dispersal. Adaptations to wind-dispersal were absent and to endozoochory were minimal. Most species had no visible adaptations and are presumably transported with mud. However, about one-quarter of the taxa, particularly the tall and dominant ones, relied at least partially on burrs with hooks or awns. The possible vectors for these exo- or epizoochorous species are discussed: the most likely regular dispersers are humans (epianthropochory). Interviews with farmers confirm this conclusion. Using humans as vectors allows the plant to transport relatively large seeds to favorable habitats (directed dispersal). The importance of this relatively rare dispersal adaptation in Mexican maize field weeds leads to questions on the origin and evolution of these agrestals.

  18. Weed biocontrol in the EU: from serendipity to strategy

    Science.gov (United States)

    Biological control of weeds is a globally-recognized approach to the management of the worst invasive plants in the world. Unfortunately, accidental introduction of agents account for most weed biocontrol in the EU, but do include a number of current or emerging successes. From the redistribution of...

  19. 7 CFR 360.300 - General prohibitions and restrictions on the movement of noxious weeds; permits.

    Science.gov (United States)

    2010-01-01

    ... of noxious weeds; permits. 360.300 Section 360.300 Agriculture Regulations of the Department of Agriculture (Continued) ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE NOXIOUS WEED REGULATIONS § 360.300 General prohibitions and restrictions on the movement of noxious weeds; permits. (a) No...

  20. Effect of weeding management on the performance of local maize populations

    Directory of Open Access Journals (Sweden)

    J. Peña-Asin

    2013-11-01

    Full Text Available One of the most important stress factors in maize (Zea mays L. fields is weed competition, which reduces the crop yield. Weeds chiefly interfere with maize and establish considerable competition for light, water and nutrients. To avoid these harmful effects, there are different agronomic measures and factors among which, the most relevant are the interactions between crop and weed, weed management practices and type of germplasm. This study attempts to evaluate maize germplasm for tolerance to weed competition in order to achieve competitive ability and suitability for farming. Ten genotypes of maize, classified into two groups, i.e. improved populations and traditional cultivars, were grown under four types of weed management practices (mechanical harrowing control, chemical control, combination of harrowing and chemical control and untreated control as check for three years (from 2009 to 2011 in Zaragoza (Spain. We found that the effect of weed management practices was not significantly different, whereas the genotype effect was highly significant, with genotype EZS34 (mean yield of 7.7 Mg ha-1 showing the highest yield. Other traits, such as earliness, displayed a good behaviour under weed competition. On the other hand, harrowing management proved to be the most effective method of weed control although it did not show a significant response. The best results are associated with some maize genotypes that have a specific adaptation to local conditions, according to their genetic background.

  1. Can Arbuscular Mycorrhizal Fungi Reduce the Growth of Agricultural Weeds?

    Science.gov (United States)

    Veiga, Rita S. L.; Jansa, Jan; Frossard, Emmanuel; van der Heijden, Marcel G. A.

    2011-01-01

    Background Arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects on plants. However, there is increasing evidence that some ruderal plants, including several agricultural weeds, respond negatively to AMF colonization. Here, we investigated the effect of AMF on the growth of individual weed species and on weed-crop interactions. Methodology/Principal Findings First, under controlled glasshouse conditions, we screened growth responses of nine weed species and three crops to a widespread AMF, Glomus intraradices. None of the weeds screened showed a significant positive mycorrhizal growth response and four weed species were significantly reduced by the AMF (growth responses between −22 and −35%). In a subsequent experiment, we selected three of the negatively responding weed species – Echinochloa crus-galli, Setaria viridis and Solanum nigrum – and analyzed their responses to a combination of three AMF (Glomus intraradices, Glomus mosseae and Glomus claroideum). Finally, we tested whether the presence of a crop (maize) enhanced the suppressive effect of AMF on weeds. We found that the growth of the three selected weed species was also reduced by a combination of AMF and that the presence of maize amplified the negative effect of AMF on the growth of E. crus-galli. Conclusions/Significance Our results show that AMF can negatively influence the growth of some weed species indicating that AMF have the potential to act as determinants of weed community structure. Furthermore, mycorrhizal weed growth reductions can be amplified in the presence of a crop. Previous studies have shown that AMF provide a number of beneficial ecosystem services. Taken together with our current results, the maintenance and promotion of AMF activity may thereby contribute to sustainable management of agroecosystems. However, in order to further the practical and ecological relevance of our findings, additional experiments should be performed under field conditions. PMID

  2. Plant Community Richness Mediates Inhibitory Interactions and Resource Competition between Streptomyces and Fusarium Populations in the Rhizosphere.

    Science.gov (United States)

    Essarioui, Adil; LeBlanc, Nicholas; Kistler, Harold C; Kinkel, Linda L

    2017-07-01

    Plant community characteristics impact rhizosphere Streptomyces nutrient competition and antagonistic capacities. However, the effects of Streptomyces on, and their responses to, coexisting microorganisms as a function of plant host or plant species richness have received little attention. In this work, we characterized antagonistic activities and nutrient use among Streptomyces and Fusarium from the rhizosphere of Andropogon gerardii (Ag) and Lespedeza capitata (Lc) plants growing in communities of 1 (monoculture) or 16 (polyculture) plant species. Streptomyces from monoculture were more antagonistic against Fusarium than those from polyculture. In contrast, Fusarium isolates from polyculture had greater inhibitory capacities against Streptomyces than isolates from monoculture. Although Fusarium isolates had on average greater niche widths, the collection of Streptomyces isolates in total used a greater diversity of nutrients for growth. Plant richness, but not plant host, influenced the potential for resource competition between the two taxa. Fusarium isolates had greater niche overlap with Streptomyces in monoculture than polyculture, suggesting greater potential for Fusarium to competitively challenge Streptomyces in monoculture plant communities. In contrast, Streptomyces had greater niche overlap with Fusarium in polyculture than monoculture, suggesting that Fusarium experiences greater resource competition with Streptomyces in polyculture than monoculture. These patterns of competitive and inhibitory phenotypes among Streptomyces and Fusarium populations are consistent with selection for Fusarium-antagonistic Streptomyces populations in the presence of strong Fusarium resource competition in plant monocultures. Similarly, these results suggest selection for Streptomyces-inhibitory Fusarium populations in the presence of strong Streptomyces resource competition in more diverse plant communities. Thus, landscape-scale variation in plant species richness may be

  3. Interferência e nível de dano econômico de capim-arroz sobre o arroz em função do arranjo de plantas da cultura Interference and economic weed threshold (Ewt of barnyardgrass on rice as a function of crop plant arrangement

    Directory of Open Access Journals (Sweden)

    D. Agostinetto

    2010-01-01

    carried out under field conditions with rice crop, under the conventional system. The treatments consisted of three arrangements of rice plants, one cultivar BRS Pelota (17 and 32 cm, hand sown and nine populations of the competitor barnyardgrass present in each sowing method. The rectangular hyperbolic nonlinear regression model appropriately estimates rice productivity losses in the presence of barnyardgrass plants. Manually sown rice crop shows greater competitive ability against barnyardgrass in relation to the 17 and 32 cm spacings. The variable leaf area fits better to the hyperbolic model,compared to the variables plant population, shoot dry weight and soil covering. Sowing the crop by hand increases the economic weed threshold, justifying the adoption of measures to control barnyardgrass at higher population levels. Increased grain yield, rice price, herbicide efficiency and control cost reduction decrease the economic weed threshold values, justifying the adoption of control measures in low populations of barnyardgrass.

  4. Performance of Planted Herbaceous Species in Longleaf Pine (Pinus palustris Mill.) Plantations: Overstory Effects of Competition and Needlefall

    Energy Technology Data Exchange (ETDEWEB)

    Dagley, C.M.

    2001-07-03

    Research to determine the separate effects of above-ground and below-ground competition and needlefall of over-story pines on under-story plant performance. Periodic monitoring of over-story crown closure, soil water content, temperature, and nutrients were conducted. Results indicate competition for light had a more determental effect on performance of herbaceous species in longleaf pine plantations than that resulting from competition for below-ground resources.

  5. Herbivore exclusion drives the evolution of plant competitiveness via increased allelopathy.

    Science.gov (United States)

    Uesugi, Akane; Kessler, André

    2013-05-01

    The 'Evolution of Increased Competitive Ability (EICA)' hypothesis predicts the evolution of plant invasiveness in introduced ranges when plants escape from their natural enemies. So far, the EICA hypothesis has been tested by comparing plant vigor from native and invasive populations, but these studies are confounded by among-population differences in additional environmental factors and/or founder effects. We tested the major prediction of EICA by comparing the competitive ability (CA) of Solidago altissima plants originating from artificial selection plots in which we manipulated directly the exposure to above-ground herbivores. In a common garden experiment, we found an increase in inter-specific, but not intra-specific, CA in clones from herbivore exclusion plots relative to control plots. The evolutionary increase in inter-specific CA coincided with the increased production of polyacetylenes, whose major constituent was allelopathic against a heterospecific competitor, Poa pratensis, but not against conspecifics. Our results provide direct evidence that release from herbivory alone can lead to an evolutionary increase in inter-specific CA, which is likely to be mediated by the increased production of allelopathic compounds in S. altissima. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  6. Site Specific Weed Control Technologies

    DEFF Research Database (Denmark)

    Christensen, Svend; Søgaard, Henning Tangen; Kudsk, Per;

    2009-01-01

    describe the basic parts of site specific weed control technologies, comprising of weed sensing systems, weed management models and precision weed control implements. A review of state-of-the-art technologies shows that several weed sensing systems and precision implements have been developed over the last...... of knowledge about the economic and environmental potential for increasing the resolution of weed control. The integration of site-specific information on weed distribution, weed species composition and density, and the effect on crop yield, is decisive for successful site-specific weed management.   Keywords......Site-specific weed control technologies are defined as machinery or equipment embedded with technologies that detect weeds growing in a crop and, taking into account predefined factors such as economics, takes action to maximise the chances of successfully controlling them. In the article, we...

  7. Automated intelligent rotor tine cultivation and punch planting to improve the selectivity of mechanical intra-row weed control

    DEFF Research Database (Denmark)

    Rasmussen, Jesper; Griepentrog, Hans W.; Nielsen, Jon;

    2012-01-01

    planting is a sowing technique where holes are created in the ground with a minimum of soil disturbance, and seeds are inserted into them, without soil disturbance outside the holes. Two experiments were carried out with the cycloid hoe in organic sugar beet. The rotation tines were guided by RTK-GPS...

  8. Competitive advantages of the Brazilian Beef Processing Plants in their Internationalization Process

    Directory of Open Access Journals (Sweden)

    Francisco Américo Cassano

    2012-06-01

    Full Text Available The following study has the primary objective of identifying the major competitive advantages owned by Brazilian beef processing plants in their internationalization process. In order to reach it, it was carried out an exploratory research, based on the survey of official data and publications concerning world’s beef cattle production, followed by a literature review and finally, by a single case study. This case study was conducted through an interview with former employee of Redenção Frigorífico do Pará Ltda. The obtained results allowed the identification of the major competitive advantages of the studied company in its internationalization process, such as the raw material quality and availability, production scale, Brazilian cattle’s extensive production system, and control and prevention of main cattle diseases. It was concluded that Brazilian beef production plants really have competitive advantages within the internationalization process context, some of them practically observed in the studied company, and others that can be effectively corroborated by future studies.

  9. Weeding Library Collections.

    Science.gov (United States)

    Slote, Stanley J.

    This work, based on two recent research projects in the weeding of library collections and the identification of core collections, provides a comprehensive summary of the literature and research on these topics. It also presents practical guidance in weeding for the professional librarian or for the library school student. The book is divided into…

  10. Modeling spatial competition for light in plant populations with the porous medium equation.

    Science.gov (United States)

    Beyer, Robert; Etard, Octave; Cournède, Paul-Henry; Laurent-Gengoux, Pascal

    2015-02-01

    We consider a plant's local leaf area index as a spatially continuous variable, subject to particular reaction-diffusion dynamics of allocation, senescence and spatial propagation. The latter notably incorporates the plant's tendency to form new leaves in bright rather than shaded locations. Applying a generalized Beer-Lambert law allows to link existing foliage to production dynamics. The approach allows for inter-individual variability and competition for light while maintaining robustness-a key weakness of comparable existing models. The analysis of the single plant case leads to a significant simplification of the system's key equation when transforming it into the well studied porous medium equation. Confronting the theoretical model to experimental data of sugar beet populations, differing in configuration density, demonstrates its accuracy.

  11. Plant Photosynthesis-Irradiance Curve Responses to Pollution Show Non-Competitive Inhibited Michaelis Kinetics.

    Science.gov (United States)

    Lin, Maozi; Wang, Zhiwei; He, Lingchao; Xu, Kang; Cheng, Dongliang; Wang, Genxuan

    2015-01-01

    Photosynthesis-irradiance (PI) curves are extensively used in field and laboratory research to evaluate the photon-use efficiency of plants. However, most existing models for PI curves focus on the relationship between the photosynthetic rate (Pn) and photosynthetically active radiation (PAR), and do not take account of the influence of environmental factors on the curve. In the present study, we used a new non-competitive inhibited Michaelis-Menten model (NIMM) to predict the co-variation of Pn, PAR, and the relative pollution index (I). We then evaluated the model with published data and our own experimental data. The results indicate that the Pn of plants decreased with increasing I in the environment and, as predicted, were all fitted well by the NIMM model. Therefore, our model provides a robust basis to evaluate and understand the influence of environmental pollution on plant photosynthesis.

  12. Plant Photosynthesis-Irradiance Curve Responses to Pollution Show Non-Competitive Inhibited Michaelis Kinetics.

    Directory of Open Access Journals (Sweden)

    Maozi Lin

    Full Text Available Photosynthesis-irradiance (PI curves are extensively used in field and laboratory research to evaluate the photon-use efficiency of plants. However, most existing models for PI curves focus on the relationship between the photosynthetic rate (Pn and photosynthetically active radiation (PAR, and do not take account of the influence of environmental factors on the curve. In the present study, we used a new non-competitive inhibited Michaelis-Menten model (NIMM to predict the co-variation of Pn, PAR, and the relative pollution index (I. We then evaluated the model with published data and our own experimental data. The results indicate that the Pn of plants decreased with increasing I in the environment and, as predicted, were all fitted well by the NIMM model. Therefore, our model provides a robust basis to evaluate and understand the influence of environmental pollution on plant photosynthesis.

  13. Weeds under the canopies of tree species submitted to different planting densities and intercropping Plantas daninhas sob copas de espécies arbóreas submetidas a consórcios e densidades de plantio diferentes

    Directory of Open Access Journals (Sweden)

    A.D Souza

    2013-03-01

    Full Text Available Assessing the growth and floristic composition of species that grow under the canopy of trees is important for weed control (WC. The objective of this study was to assess two experiments (E1 and E2, when the trees were two years and one year of age, respectively. In E1, sabiá (S and gliricidia (G were submitted to planting densities from 400 to 1.200 plants ha-1. In E2, growing systems consisting of S, G, and neem (N combinations were compared: SSS, GGG, NNN, GSG, NSN, SGS, NGN, SNS, and GNG (each letter represents a row of plants. A random block design was adopted, with three (E1 and four (E2 replicates. In E1, treatments were arranged as split-plots (species in plots. In E2, the degrees of freedom for treatments (8 were partitioned into growing systems (treatments that involved the same species and between growing system groups (2. Twenty-one weed species were found in E1. Gliricidia attained greater plant height than sabiá, but these species did not differ in canopy diameter, number of weed species per plot, and weed green and dry biomass of the shoot. Higher planting densities resulted in the reduction of all those traits. Twenty-six weed species were found in E2. Growing systems that included gliricidia showed canopies with greater diameters than growing systems that included neem. There were no differences between growing systems for number of weed species per plot and for weed green and dry biomass of the shoot.Avaliações do crescimento e da composição florística de espécies que vegetam sob a copa das árvores são importantes no controle de plantas daninhas (PD. O objetivo deste trabalho foi realizar essas avaliações em dois experimentos (E1 e E2, quando as árvores tinham idades de dois anos e um ano, respectivamente. Em E1, sabiá (S e gliricídia (G foram submetidas a densidades de plantio de 400 a 1.200 plantas ha-1. Em E2, foram comparados sistemas de cultivo de S, G e nim (N: SSS, GGG, NNN, GSG, NSN, SGS, NGN, SNS e GNG

  14. Facilitation and competition among invasive plants: a field experiment with alligatorweed and water hyacinth.

    Science.gov (United States)

    Wundrow, Emily J; Carrillo, Juli; Gabler, Christopher A; Horn, Katherine C; Siemann, Evan

    2012-01-01

    Ecosystems that are heavily invaded by an exotic species often contain abundant populations of other invasive species. This may reflect shared responses to a common factor, but may also reflect positive interactions among these exotic species. Armand Bayou (Pasadena, TX) is one such ecosystem where multiple species of invasive aquatic plants are common. We used this system to investigate whether presence of one exotic species made subsequent invasions by other exotic species more likely, less likely, or if it had no effect. We performed an experiment in which we selectively removed exotic rooted and/or floating aquatic plant species and tracked subsequent colonization and growth of native and invasive species. This allowed us to quantify how presence or absence of one plant functional group influenced the likelihood of successful invasion by members of the other functional group. We found that presence of alligatorweed (rooted plant) decreased establishment of new water hyacinth (free-floating plant) patches but increased growth of hyacinth in established patches, with an overall net positive effect on success of water hyacinth. Water hyacinth presence had no effect on establishment of alligatorweed but decreased growth of existing alligatorweed patches, with an overall net negative effect on success of alligatorweed. Moreover, observational data showed positive correlations between hyacinth and alligatorweed with hyacinth, on average, more abundant. The negative effect of hyacinth on alligatorweed growth implies competition, not strong mutual facilitation (invasional meltdown), is occurring in this system. Removal of hyacinth may increase alligatorweed invasion through release from competition. However, removal of alligatorweed may have more complex effects on hyacinth patch dynamics because there were strong opposing effects on establishment versus growth. The mix of positive and negative interactions between floating and rooted aquatic plants may influence local

  15. Facilitation and competition among invasive plants: a field experiment with alligatorweed and water hyacinth.

    Directory of Open Access Journals (Sweden)

    Emily J Wundrow

    Full Text Available Ecosystems that are heavily invaded by an exotic species often contain abundant populations of other invasive species. This may reflect shared responses to a common factor, but may also reflect positive interactions among these exotic species. Armand Bayou (Pasadena, TX is one such ecosystem where multiple species of invasive aquatic plants are common. We used this system to investigate whether presence of one exotic species made subsequent invasions by other exotic species more likely, less likely, or if it had no effect. We performed an experiment in which we selectively removed exotic rooted and/or floating aquatic plant species and tracked subsequent colonization and growth of native and invasive species. This allowed us to quantify how presence or absence of one plant functional group influenced the likelihood of successful invasion by members of the other functional group. We found that presence of alligatorweed (rooted plant decreased establishment of new water hyacinth (free-floating plant patches but increased growth of hyacinth in established patches, with an overall net positive effect on success of water hyacinth. Water hyacinth presence had no effect on establishment of alligatorweed but decreased growth of existing alligatorweed patches, with an overall net negative effect on success of alligatorweed. Moreover, observational data showed positive correlations between hyacinth and alligatorweed with hyacinth, on average, more abundant. The negative effect of hyacinth on alligatorweed growth implies competition, not strong mutual facilitation (invasional meltdown, is occurring in this system. Removal of hyacinth may increase alligatorweed invasion through release from competition. However, removal of alligatorweed may have more complex effects on hyacinth patch dynamics because there were strong opposing effects on establishment versus growth. The mix of positive and negative interactions between floating and rooted aquatic plants may

  16. Allelobiosis in the interference of allelopathic wheat with weeds.

    Science.gov (United States)

    Li, Yong-Hua; Xia, Zhi-Chao; Kong, Chui-Hua

    2016-11-01

    Plants may chemically affect the performance of neighbouring plants through allelopathy, allelobiosis or both. In spite of increasing knowledge about allelobiosis, defined as the signalling interactions mediated by non-toxic chemicals involved in plant-plant interactions, the phenomenon has received relatively little attention in the scientific literature. This study examined the role of allelobiosis in the interference of allelopathic wheat with weeds. Allelopathic wheat inhibited the growth of five weed species tested, and the allelochemical (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) production of wheat was elicited in the presence of these weeds, even with root segregation. The inhibition and allelochemical levels varied greatly with the mixed species density. Increased inhibition and allelochemical levels occurred at low and medium densities but declined at high densities. All the root exudates and their components of jasmonic acid and salicylic acid from five weeds stimulated allelochemical production. Furthermore, jasmonic acid and salicylic acid were found in plants, root exudates and rhizosphere soils, regardless of weed species, indicating their participation in the signalling interactions defined as allelobiosis. Through root-secreted chemical signals, allelopathic wheat can detect competing weeds and respond by increased allelochemical levels to inhibit them, providing an advantage for its own growth. Allelopathy and allelobiosis are two probably inseparable processes that occur together in wheat-weed chemical interactions. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  17. Exploring the effects of glyphosate products on weed composition

    Directory of Open Access Journals (Sweden)

    Koning, Laurie Anne

    2016-02-01

    Full Text Available Glyphosate is a non-selective, broad-spectrum, systematic herbicide that is the world’s most widely used herbicide since its introduction in the 1970s as a pre-plant, post-directed and post-harvest herbicide application with further technological developments leading to its use within glyphosate resistant crops (GRCs as of the 1990s. In countries around the world, weed shifts have accompanied weed management systems employing glyphosate products. The farmer actions and weed reactions that have contributed to these weed shifts will be discussed. Evidence of glyphosate-induced weed shifts has not yet been documented in Germany, but through consideration of the conditions that have lead to glyphosate-induced weed shifts elsewhere the outlook for Germany will be assessed. An ongoing research project will be introduced in which weed monitoring is being employed to find out if glyphosate-induced weed shifts can be identified in northeastern German arable farm fields and in which field experiments are also being conducted to further explore the reactions of weed communities and populations under the intensive application of glyphosate products.

  18. Soil nutrient competition in earth system models: an important but underappreciated driver of plant responses to nutrient fertilization

    Science.gov (United States)

    Zhu, Q.; Riley, W. J.; Tang, J.; Koven, C.

    2015-12-01

    Earth System Models (ESMs) used to project future biosphere-climate feedbacks rely on predictions of terrestrial carbon dynamics. Furthermore, soil nutrient availability strongly modulates land surface carbon dynamics, including plant sequestration of atmospheric CO2. Plant growth under future environmental changes (e.g., nitrogen and phosphorus deposition) depends on how well plants compete with microbial and abiotic competitors. Here, we surveyed recent developments of nutrient competition representations in ESMs that participated in the CMIP5 project. We found that nutrient competition is over-simplified despite its ecological significance. Existing ESMs either assume that soil-decomposing microbes (1) outcompete plants or (2) are evenly competitive, both of which are inconsistent with theoretical understanding and field observations. We compiled and synthesized global data of forest carbon productivity in response to nitrogen and phosphorus fertilization experiments. Using this synthesis, we show that existing ESMs with the first and second competition schemes lead to underestimation and overestimation, respectively, of fertilization effects on plant growth. We reduced these systematic biases by applying a new competition scheme in CLM4.5 and the essentially equivalent ACME land model (ALMv0) based on the Equilibrium Chemistry Approximation, which is based on classical equilibrium chemical kinetics theory. This approach dynamically updates nutrient competitiveness among multiple consumers (e.g., plants, decomposing microbes, nitrifier, denitrifier, mineral surfaces) as a function of soil nutrient status. There has been a long-term debate regarding how to implement theoretically realistic and computationally efficient nutrient competition schemes in ESMs. Our approach reconciles the complex nature of ecosystem nutrient competition with a computationally tractable approach applicable to ESMs. More importantly, our results imply that previous estimates of plant

  19. Competition for light and water in a coupled soil-plant system

    Science.gov (United States)

    Manoli, Gabriele; Huang, Cheng-Wei; Bonetti, Sara; Domec, Jean-Christophe; Marani, Marco; Katul, Gabriel

    2017-10-01

    It is generally accepted that resource availability shapes the structure and function of many ecosystems. Within the soil-plant-atmosphere (SPA) system, resource availability fluctuates in space and time whereas access to resources by individuals is further impacted by plant-to-plant competition. Likewise, transport and transformation of resources within an individual plant is governed by numerous interacting biotic and abiotic processes. The work here explores the co-limitations on water losses and carbon uptake within the SPA arising from fluctuating resource availability and competition. In particular, the goal is to unfold the interplay between plant access and competition for water and light, as well as the impact of transport/redistribution processes on leaf-level carbon assimilation and water fluxes within forest stands. A framework is proposed that couples a three-dimensional representation of soil-root exchanges with a one-dimensional description of stem water flow and storage, canopy photosynthesis, and transpiration. The model links soil moisture redistribution, root water uptake, xylem water flow and storage, leaf potential and stomatal conductance as driven by supply and demand for water and carbon. The model is then used to investigate plant drought resilience of overstory-understory trees simultaneously competing for water and light. Simulation results reveal that understory-overstory interactions increase ecosystem resilience to drought (i.e. stand-level carbon assimilation rates and water fluxes can be sustained at lower root-zone soil water potentials). This resilience enhancement originates from reduced transpiration (due to shading) and hydraulic redistribution in soil supporting photosynthesis over prolonged periods of drought. In particular, the presence of different rooting systems generates localized hydraulic redistribution fluxes that sustain understory transpiration through overstory-understory interactions. Such complex SPA dynamics

  20. Variations in Growth, Photosynthesis and Defense System Among Four Weed Species Under Increased UV-B Radiation

    Institute of Scientific and Technical Information of China (English)

    Shiwen Wang; Liusheng Duan; Anthony Egrinya Eneji; Zhaohu Li

    2007-01-01

    Weed tolerance of UV-B radiation varies with species, and the radiation could affect weed ecology and management.Variations in growth, photosynthesis and defense system among four important agronomic weeds, Abutilon theophrasti Medik, Amaranthus retroflexus L., Digitaria sangulnalis (L.) Scop and Chloris virgata Swartz, under increased UV-B radiation (ambient and increased radiation at 2.7, 5.4 and 10.8 kJ·m-2·d-1) were studied in the greenhouse experiment. After 2 weeks of radiation, the shoots' dry mass decreased with increasing UV-B radiation except for D. sanguinalis. The reduction in biomass was the result of changes in morphology and physiology.Higher levels of UV-B treatment decreased the leaf area, plant height, net photosynthetic rate and chlorophyll contents, while it increased the contents of wax and UV-B absorbing compound in all species, except for A. retroflexus,which did not increase significantly. The activity of superoxide dismutase, catalase, ascorbate peroxide and the content of ascorbic acid changed differently among the weed species as UV-B radiation increased. D. sanguinalis was the most tolerant and A. retroflexus the most sensitive to increased UV-B radiation. The results also show that the two grass species (D. sanguinalis and C. virgata) were more tolerant to UV-B radiation than the two broadleafed species (A. theophrasti and A. retroflexus). The UV-B absorbing compound and leaf wax played important roles against UV-B damages in the two grass weeds. The overall results suggest that weed community, competition and management will be altered by continuous ozone depletion.

  1. Airborne hyperspectral and LiDAR data integration for weed detection

    Science.gov (United States)

    Tamás, János; Lehoczky, Éva; Fehér, János; Fórián, Tünde; Nagy, Attila; Bozsik, Éva; Gálya, Bernadett; Riczu, Péter

    2014-05-01

    Agriculture uses 70% of global available fresh water. However, ca. 50-70% of water used by cultivated plants, the rest of water transpirated by the weeds. Thus, to define the distribution of weeds is very important in precision agriculture and horticulture as well. To survey weeds on larger fields by traditional methods is often time consuming. Remote sensing instruments are useful to detect weeds in larger area. In our investigation a 3D airborne laser scanner (RIEGL LMS-Q680i) was used in agricultural field near Sopron to scouting weeds. Beside the airborne LiDAR, hyperspectral imaging system (AISA DUAL) and air photos helped to investigate weed coverage. The LiDAR survey was carried out at early April, 2012, before sprouting of cultivated plants. Thus, there could be detected emerging of weeds and direction of cultivation. However airborne LiDAR system was ideal to detect weeds, identification of weeds at species level was infeasible. Higher point density LiDAR - Terrestrial laser scanning - systems are appropriate to distinguish weed species. Based on the results, laser scanner is an effective tool to scouting of weeds. Appropriate weed detection and mapping systems could contribute to elaborate water and herbicide saving management technique. This publication was supported by the OTKA project K 105789.

  2. Upper Limit for Context--based Crop Classification in Robotic Weeding Applications

    DEFF Research Database (Denmark)

    Midtiby, Henrik Skov

    2016-01-01

    Knowledge of the precise position of crop plants is a prerequisite for effective mechanical weed control in robotic weeding application such as in crops like sugar beets which are sensitive to mechanical stress. Visual detection and recognition of crop plants based on their shapes has been...... described many times in the literature. In this paper the potential of using knowledge about the crop seed pattern is investigated based on simulated output from a perception system. The reliability of position–based crop plant detection is shown to depend on the weed density (ρ, measured in weed plants per...

  3. Upper limit for context-based crop classification in robotic weeding applications

    DEFF Research Database (Denmark)

    Midtiby, Henrik Skov; Åstrand, Björn; Jørgensen, Ole;

    2016-01-01

    Knowledge of the precise position of crop plants is a prerequisite for effective mechanical weed control in robotic weeding application such as in crops like sugar beets which are sensitive to mechanical stress. Visual detection and recognition of crop plants based on their shapes has been...... described many times in the literature. In this paper the potential of using knowledge about the crop seed pattern is investigated based on simulated output from a perception system. The reliability of position–based crop plant detection is shown to depend on the weed density (ρ, measured in weed plants per...

  4. Effect of organic mulch materials on maize performance and weed ...

    African Journals Online (AJOL)

    Effect of organic mulch materials on maize performance and weed growth in the derived ... AFRICAN JOURNALS ONLINE (AJOL) · Journals · Advanced Search ... of organic mulch materials (Plant and Animal) on the performance of maize and ...

  5. Weed Control Trials in Cottonwood Plantations

    Science.gov (United States)

    R. M. Krinard

    1964-01-01

    Weed control in the first year is essential for establishing a cottonwood plantation, for the young trees can neither survive nor grow well if they must compete with other plants. Once the light and moisture conditions are established in its favor, cottonwood becomes the fastest growing tree in the South.

  6. Grazing-induced effects on soil properties modify plant competitive interactions in semi-natural mountain grasslands.

    Science.gov (United States)

    Medina-Roldán, Eduardo; Paz-Ferreiro, Jorge; Bardgett, Richard D

    2012-09-01

    Plant-soil feedbacks are widely recognized as playing a significant role in structuring plant communities through their effects on plant-plant interactions. However, the question of whether plant-soil feedbacks can be indirectly driven by other ecological agents, such as large herbivores, which are known to strongly modify plant community structure and soil properties, remains poorly explored. We tested in a glasshouse experiment how changes in soil properties resulting from long-term sheep grazing affect competitive interactions (intra- and inter-specific) of two graminoid species: Nardus stricta, which is typically abundant under high sheep grazing pressure in British mountain grasslands; and Eriophorum vaginatum, whose abundance is typically diminished under grazing. Both species were grown in monocultures and mixtures at different densities in soils taken from adjacent grazed and ungrazed mountain grassland in the Yorkshire Dales, northern England. Nardus stricta performed better (shoot and root biomass) when grown in grazing-conditioned soil, independent of whether or not it grew under inter-specific competition. Eriophorum vaginatum also grew better when planted in soil from the grazed site, but this occurred only when it did not experience inter-specific competition with N. stricta. This indicates that plant-soil feedback for E. vaginatum is dependent on the presence of an inter-specific competitor. A yield density model showed that indirect effects of grazing increased the intensity of intra-specific competition in both species in comparison with ungrazed-conditioned soil. However, indirect effects of grazing on the intensity of inter-specific competition were species-specific favouring N. stricta. We explain these asymmetric grazing-induced effects on competition on the basis of traits of the superior competitor and grazing effects on soil nutrients. Finally, we discuss the relevance of our findings for plant community dynamics in grazed, semi

  7. Robust Crop and Weed Segmentation under Uncontrolled Outdoor Illumination

    Directory of Open Access Journals (Sweden)

    Hong Y. Jeon

    2011-06-01

    Full Text Available An image processing algorithm for detecting individual weeds was developed and evaluated. Weed detection processes included were normalized excessive green conversion, statistical threshold value estimation, adaptive image segmentation, median filter, morphological feature calculation and Artificial Neural Network (ANN. The developed algorithm was validated for its ability to identify and detect weeds and crop plants under uncontrolled outdoor illuminations. A machine vision implementing field robot captured field images under outdoor illuminations and the image processing algorithm automatically processed them without manual adjustment. The errors of the algorithm, when processing 666 field images, ranged from 2.1 to 2.9%. The ANN correctly detected 72.6% of crop plants from the identified plants, and considered the rest as weeds. However, the ANN identification rates for crop plants were improved up to 95.1% by addressing the error sources in the algorithm. The developed weed detection and image processing algorithm provides a novel method to identify plants against soil background under the uncontrolled outdoor illuminations, and to differentiate weeds from crop plants. Thus, the proposed new machine vision and processing algorithm may be useful for outdoor applications including plant specific direct applications (PSDA.

  8. Robust crop and weed segmentation under uncontrolled outdoor illumination.

    Science.gov (United States)

    Jeon, Hong Y; Tian, Lei F; Zhu, Heping

    2011-01-01

    An image processing algorithm for detecting individual weeds was developed and evaluated. Weed detection processes included were normalized excessive green conversion, statistical threshold value estimation, adaptive image segmentation, median filter, morphological feature calculation and Artificial Neural Network (ANN). The developed algorithm was validated for its ability to identify and detect weeds and crop plants under uncontrolled outdoor illuminations. A machine vision implementing field robot captured field images under outdoor illuminations and the image processing algorithm automatically processed them without manual adjustment. The errors of the algorithm, when processing 666 field images, ranged from 2.1 to 2.9%. The ANN correctly detected 72.6% of crop plants from the identified plants, and considered the rest as weeds. However, the ANN identification rates for crop plants were improved up to 95.1% by addressing the error sources in the algorithm. The developed weed detection and image processing algorithm provides a novel method to identify plants against soil background under the uncontrolled outdoor illuminations, and to differentiate weeds from crop plants. Thus, the proposed new machine vision and processing algorithm may be useful for outdoor applications including plant specific direct applications (PSDA).

  9. Size-symmetric competition in a shade-tolerant invasive plant

    DEFF Research Database (Denmark)

    Pan, Xiao-Yun; Weiner, Jacob; Li, Bo

    2013-01-01

    , a shade‐tolerant invasive species. Stem fragments of A. philoxeroides were grown at either low or high densities (6 vs. 24 plants per pot) under three light levels (10%, 34%, and 100% full sun). After 8 weeks, survival was 31% lower in pots with a higher initial density. Both high density and low light......Plant responses to crowding have been investigated extensively in stands of light‐demanding species, but shade‐tolerant species may react differently. In the present study, we investigated the effect of density on the mortality, size inequality, and biomass allocation of Alternanthera philoxeroides...... competition need not be size asymmetric, and suggest that tolerance to low light levels involves a reduction in phenotypic plasticity. Responses of the invasive A. philoxeroides to crowding may be an example of an invasive plant’s success in establishing dense stands of closely related individuals...

  10. Study on Application of Chemical Control Techniques for Worst Weeds in Landscape Plant Nurseries in Jianghuai Region%江淮地区园林苗圃地恶性杂草化学防除技术应用研究

    Institute of Scientific and Technical Information of China (English)

    王新洋; 周根土; 张均

    2015-01-01

    In this paper the integrated control techniques regarding the main weed species, herbicides and the times,concentrations, methods of their applications for chemical weeding and artificial weeding in landscape plant nurseries were introduced. Chemical and artificial weeding techniques for 6 worst weeds in pre-emergence and seedling stages were elaborated in detail including Alternanthera philoxeroides, Commelina communis, Cyperus rotundus, Artemisia Selengensis, Cirsium setosum and Imperata cylindrica,so were the chemical weeding methods for difficult-to-control weed species Digitaria sanguinalis, Acalypha australis, Amaranthus tricolor, Eclipta prostrata, Chenopodium quinoa,Convolvu arvensis,Celosia cristata, Portulaca oleracea and Abutilon theophrasti. The study could provide practical chemical weeding operation techniques for landscape plant nurseries.%本文叙述了园林苗圃地主要杂草、除草剂,化学除草施用时间、浓度、方法,以及人工除草等综合防除技术,详细叙述了芽前、苗期化学和人工除草技术及苗圃地空心莲子草、鸭跖草、香附子、芦蒿、刺儿菜、白茅6种恶性杂草,以及防除难度较大的杂草马唐、铁苋菜、苋菜、醴肠、藜、田旋花、野鸡冠花、马齿苋、茼麻等化学除草方法,为园林苗木培育提供实用的苗圃化学除草操作技术。

  11. Sistemas de control de malezas en maiz (Zea mays L.: efecto de metodos de control, densidad y distribucion del cultivo Weed control systems in corn: effects of control methods, density and plant distribution

    Directory of Open Access Journals (Sweden)

    G. Martinez

    1982-12-01

    realización de una escarda adicional no mejora significativamente el control de malezas, no afectando tampoco la incidencia de enfermedades, ni el desarrollo del cultivo, por lo cual resulta innecesaria. Las escardas tienen como principal efecto eliminar la interfe rencia presentada por las malezas y si éstas son eliminadas de otra manera, la realización de aquéllas no apareja beneficios significativos.An experiment was conducted at the Research Station of the University of Chapingo (Mexico (2250 m above sea level, average annual rainfall 550 mm( loamy soil, 1,7% O.M., where different cultural practices were combined in order to design a weed control system for corn. The work was done under rainfed conditions and the variables included were: two population densities (44.400 and 66.600 pl/ha, two plant distributions (normal and equidistant and seven weed control methods (cyanazine + alachlor (1,2 + 1,92 kg/ha, atrazine + alachlor (1,2 + 1,44 kg/ha, one cultivation, two cultivations, a weeded check, a weeded check + two cultivations and a weedy check. The main weed species were: pigweed (Amaranthus sp., Lopezia mexicana Jacq., hairy galinsoga (Galin-soga parviflora Cay., Encelia mexicana Mart., Sporobulus poiretti (Roem. et Sch. Hich., and large crabgrass (Digitaria sanguinalis (L. Scop.. The increase in plant population had no effect on the degree of weed control, incidence of diseases and crop growth. The equidistant distribution improved weed control over the normal one, but it also had a nigher incidence of diseases; this, is turn, may have caused the lack of differences in vegetative growth, a lower amount of cobs per ha and the lack of difference in grain yield between the two distributions. Atrazine + alachlor was better than cyanazine + alachlor in terms of weed control, although the difference was statistically observed only for the visual ratings. There were no differences between both chemical treatments in terms of incidence of diseases or their effect on crop

  12. The Politics of Weeding.

    Science.gov (United States)

    Tillman, Hope N.

    1988-01-01

    Reviews the literature that deals with the political ramifications of weeding material from academic library collections and the need to involve users and other libraries within the institution in the decision process. (14 references) (CLB)

  13. Effects of Spatial Patch Arrangement and Scale of Covarying Resources on Growth and Intraspecific Competition of a Clonal Plant.

    Science.gov (United States)

    Wang, Yong-Jian; Shi, Xue-Ping; Meng, Xue-Feng; Wu, Xiao-Jing; Luo, Fang-Li; Yu, Fei-Hai

    2016-01-01

    Spatial heterogeneity in two co-variable resources such as light and water availability is common and can affect the growth of clonal plants. Several studies have tested effects of spatial heterogeneity in the supply of a single resource on competitive interactions of plants, but none has examined those of heterogeneous distribution of two co-variable resources. In a greenhouse experiment, we grew one (without intraspecific competition) or nine isolated ramets (with competition) of a rhizomatous herb Iris japonica under a homogeneous environment and four heterogeneous environments differing in patch arrangement (reciprocal and parallel patchiness of light and soil water) and patch scale (large and small patches of light and water). Intraspecific competition significantly decreased the growth of I. japonica, but at the whole container level there were no significant interaction effects of competition by spatial heterogeneity or significant effect of heterogeneity on competitive intensity. Irrespective of competition, the growth of I. japonica in the high and the low water patches did not differ significantly in the homogeneous treatments, but it was significantly larger in the high than in the low water patches in the heterogeneous treatments with large patches. For the heterogeneous treatments with small patches, the growth of I. japonica was significantly larger in the high than in the low water patches in the presence of competition, but such an effect was not significant in the absence of competition. Furthermore, patch arrangement and patch scale significantly affected competitive intensity at the patch level. Therefore, spatial heterogeneity in light and water supply can alter intraspecific competition at the patch level and such effects depend on patch arrangement and patch scale.

  14. Overcompensation of herbivore reproduction through hyper-suppression of plant defenses in response to competition.

    Science.gov (United States)

    Schimmel, Bernardus C J; Ataide, Livia M S; Chafi, Rachid; Villarroel, Carlos A; Alba, Juan M; Schuurink, Robert C; Kant, Merijn R

    2017-06-01

    Spider mites are destructive arthropod pests on many crops. The generalist herbivorous mite Tetranychus urticae induces defenses in tomato (Solanum lycopersicum) and this constrains its fitness. By contrast, the Solanaceae-specialist Tetranychus evansi maintains a high reproductive performance by suppressing tomato defenses. Tetranychus evansi outcompetes T. urticae when infesting the same plant, but it is unknown whether this is facilitated by the defenses of the plant. We assessed the extent to which a secondary infestation by a competitor affects local plant defense responses (phytohormones and defense genes), mite gene expression and mite performance. We observed that T. evansi switches to hyper-suppression of defenses after its tomato host is also invaded by its natural competitor T. urticae. Jasmonate (JA) and salicylate (SA) defenses were suppressed more strongly, albeit only locally at the feeding site of T. evansi, upon introduction of T. urticae to the infested leaflet. The hyper-suppression of defenses coincided with increased expression of T. evansi genes coding for salivary defense-suppressing effector proteins and was paralleled by an increased reproductive performance. Together, these observations suggest that T. evansi overcompensates its reproduction through hyper-suppression of plant defenses in response to nearby competitors. We hypothesize that the competitor-induced overcompensation promotes competitive population growth of T. evansi on tomato. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  15. Mycorrhiza-mediated competition between plants and decomposers drives soil carbon storage.

    Science.gov (United States)

    Averill, Colin; Turner, Benjamin L; Finzi, Adrien C

    2014-01-23

    Soil contains more carbon than the atmosphere and vegetation combined. Understanding the mechanisms controlling the accumulation and stability of soil carbon is critical to predicting the Earth's future climate. Recent studies suggest that decomposition of soil organic matter is often limited by nitrogen availability to microbes and that plants, via their fungal symbionts, compete directly with free-living decomposers for nitrogen. Ectomycorrhizal and ericoid mycorrhizal (EEM) fungi produce nitrogen-degrading enzymes, allowing them greater access to organic nitrogen sources than arbuscular mycorrhizal (AM) fungi. This leads to the theoretical prediction that soil carbon storage is greater in ecosystems dominated by EEM fungi than in those dominated by AM fungi. Using global data sets, we show that soil in ecosystems dominated by EEM-associated plants contains 70% more carbon per unit nitrogen than soil in ecosystems dominated by AM-associated plants. The effect of mycorrhizal type on soil carbon is independent of, and of far larger consequence than, the effects of net primary production, temperature, precipitation and soil clay content. Hence the effect of mycorrhizal type on soil carbon content holds at the global scale. This finding links the functional traits of mycorrhizal fungi to carbon storage at ecosystem-to-global scales, suggesting that plant-decomposer competition for nutrients exerts a fundamental control over the terrestrial carbon cycle.

  16. Integration of agronomic practices with herbicides for sustainable weed management in aerobic rice.

    Science.gov (United States)

    Anwar, M P; Juraimi, A S; Mohamed, M T M; Uddin, M K; Samedani, B; Puteh, A; Man, Azmi

    2013-01-01

    Till now, herbicide seems to be a cost effective tool from an agronomic view point to control weeds. But long term efficacy and sustainability issues are the driving forces behind the reconsideration of herbicide dependent weed management strategy in rice. This demands reappearance of physical and cultural management options combined with judicious herbicide application in a more comprehensive and integrated way. Keeping those in mind, some agronomic tools along with different manual weeding and herbicides combinations were evaluated for their weed control efficacy in rice under aerobic soil conditions. Combination of competitive variety, higher seeding rate, and seed priming resulted in more competitive cropping system in favor of rice, which was reflected in lower weed pressure, higher weed control efficiency, and better yield. Most of the herbicides exhibited excellent weed control efficiency. Treatments comprising only herbicides required less cost involvement but produced higher net benefit. On the contrary, treatments comprising both herbicide and manual weeding required high cost involvement and thus produced lower net benefit. Therefore, adoption of competitive rice variety, higher seed rate, and seed priming along with spraying different early-postemergence herbicides in rotation at 10 days after seeding (DAS) followed by a manual weeding at 30 DAS may be recommended from sustainability view point.

  17. Robotic weed monitoring

    DEFF Research Database (Denmark)

    Bochtis, Dionysis; Sørensen, Claus Aage Grøn; Jørgensen, R N

    2011-01-01

    -farm operating console, the mobile robotic unit, and a field server for generating and storingmaps. The hypothesis is that it is possible to automate the planning and execution of theoperation of monitoring of the in-field weed density and species distribution. The developedplanning system includes the automatic...... of the weed monitoring operation.Key words: autonomous vehicles, farm management, mission planning, route planning,sampling....

  18. Competitive exclusion among fig wasps achieved via entrainment of host plant flowering phenology.

    Directory of Open Access Journals (Sweden)

    Min Liu

    Full Text Available Molecular techniques are revealing increasing numbers of morphologically similar but co-existing cryptic species, challenging the niche theory. To understand the co-existence mechanism, we studied phenologies of morphologically similar species of fig wasps that pollinate the creeping fig (F. pumila in eastern China. We compared phenologies of fig wasp emergence and host flowering at sites where one or both pollinators were present. At the site where both pollinators were present, we used sticky traps to capture the emerged fig wasps and identified species identity using mitochondrial DNA COI gene. We also genotyped F. pumila individuals of the three sites using polymorphic microsatellites to detect whether the host populations were differentiated. Male F. pumila produced two major crops annually, with figs receptive in spring and summer. A small partial third crop of receptive figs occurred in the autumn, but few of the second crop figs matured at that time. Hence, few pollinators were available to enter third crop figs and they mostly aborted, resulting in two generations of pollinating wasps each year, plus a partial third generation. Receptive figs were produced on male plants in spring and summer, timed to coincide with the release of short-lived adult pollinators from the same individual plants. Most plants were pollinated by a single species. Plants pollinated by Wiebesia sp. 1 released wasps earlier than those pollinated by Wiebesia sp. 3, with little overlap. Plants occupied by different pollinators were not spatially separated, nor genetically distinct. Our findings show that these differences created mismatches with the flight periods of the other Wiebesia species, largely 'reserving' individual plants for the resident pollinator species. This pre-emptive competitive displacement may prevent long term co-existence of the two pollinators.

  19. Size-symmetric competition in a shade-tolerant invasive plant

    Institute of Scientific and Technical Information of China (English)

    Xiao-Yun PAN; Jacob WEINER; Bo LI

    2013-01-01

    Plant responses to crowding have been investigated extensively in stands of light-demanding species,but shade-tolerant species may react differently.In the present study,we investigated the effect of density on the mortality,size inequality,and biomass allocation of Alternanthera philoxeroides,a shade-tolerant invasive species.Stem fragments ofA.philoxeroides were grown at either low or high densities (6 vs.24 plants per pot) under three light levels (10%,34%,and 100% full sun).After 8 weeks,survival was 31% lower in pots with a higher initial density.Both high density and low light levels reduced plant size substantially.Mean plant biomass ranged from 0.23 g in high-density and low-light pots to 4.41 g in low-density and high-light pots.There were no strong or significant effects of density or light level on size inequality of survivors.Most of the variation in allocation and morphology in response to light level and crowding were due to plant size and allometric growth,with little evidence of true plasticity.There was a small but significant increase in shoot allocation,in the direction predicted by optimal allocation theory,at low light levels.Our results show that intense competition need not be size asymmetric,and suggest that tolerance to low light levels involves a reduction in phenotypic plasticity.Responses of the invasive A.philoxeroides to crowding may be an example of an invasive plant's success in establishing dense stands of closely related individuals that are shade tolerant,cooperative,and follow a relatively fixed allometric trajectory with low plasticity.

  20. Multiple soil nutrient competition between plants, microbes, and mineral surfaces: model development, parameterization, and example applications in several tropical forests

    Directory of Open Access Journals (Sweden)

    Q. Zhu

    2015-03-01

    Full Text Available Soil is a complex system where biotic (e.g., plant roots, micro-organisms and abiotic (e.g., mineral surfaces consumers compete for resources necessary for life (e.g., nitrogen, phosphorus. This competition is ecologically significant, since it regulates the dynamics of soil nutrients and controls aboveground plant productivity. Here we develop, calibrate, and test a nutrient competition model that accounts for multiple soil nutrients interacting with multiple biotic and abiotic consumers. As applied here for tropical forests, the Nutrient COMpetition model (N-COM includes three primary soil nutrients (NH4+, NO3−, and POx (representing the sum of PO43−, HPO42−, and H2PO4− and five potential competitors (plant roots, decomposing microbes, nitrifiers, denitrifiers, and mineral surfaces. The competition is formulated with a quasi-steady-state chemical equilibrium approximation to account for substrate (multiple substrates share one consumer and consumer (multiple consumers compete for one substrate effects. N-COM successfully reproduced observed soil heterotrophic respiration, N2O emissions, free phosphorus, sorbed phosphorus, and free NH4+ at a tropical forest site (Tapajos. The overall model posterior uncertainty was moderately well constrained. Our sensitivity analysis revealed that soil nutrient competition was primarily regulated by consumer-substrate affinity rather than environmental factors such as soil temperature or soil moisture. Our results imply that the competitiveness (from most to least competitive followed this order: (1 for NH4+, nitrifiers ~ decomposing microbes > plant roots, (2 for NO3−, denitrifiers ~ decomposing microbes > plant roots, (3 for POx, mineral surfaces > decomposing microbes ~ plant roots. Although smaller, plant relative competitiveness is of the same order of magnitude as microbes. We then applied the N-COM model to analyze field nitrogen and phosphorus perturbation experiments in two tropical forest

  1. Weed control and selectivity of flumioxazin in eucalyptus

    Directory of Open Access Journals (Sweden)

    Rafael Augusto Soares Tiburcio

    2012-12-01

    Full Text Available Flumioxazin is a registered herbicide for agricultural crops what is an important fact concerning integrated management for weeds in eucalyptus plantations. This study evaluated the efficiency of weed control and the phytotoxicity in eucalyptus plants caused by the herbicide flumioxazin applied alone or in tank mixture with sulfentrazone and isoxaflutole. The aim was to extend the use of thisherbicide in eucalyptus. The herbicide was applied to eucalyptus plants using precision backpack sprayer. It was evaluated, visually,the intoxication percentage and measured height and diameter of eucalyptus trees, the control plants and dry mass of weeds. It wasconcluded that flumioxazin is selective to the eucalyptus at the 125 g.ha-1 dosage, and its efficiency in controlling weeds pre-emergencewas better when mixed in the tank with isoxaflutole and sulfentrazone.

  2. Effect of Row Intercropping Patterns on Yield, Yield Components, and Weed Control of Fenugreek (Trigonellafoenumgreacum L. and Anise (Pimpinellaanisum L.

    Directory of Open Access Journals (Sweden)

    F Mardani

    2016-02-01

    Full Text Available Introduction Due to population growth and food shortage agricultural production is on increasing demand. In this order increasing cultivation area and yield per unit area are two ways of obtaining higheragricultural production (20. There is another important way that without incurring additional costs and use of water and fertilizer could result in higher production. This approach is increasing agricultural production per unit area by growing more than one crop in a year. Intercropping will be successful when competition for sources issless than competition within a species. Plants in the mixture can be chosen in a way that a species benefits from environmental changes caused by other species in mixed cultures directly (7, 15. Intercropping inhibits the growth and development of weeds and leads to increased production. Since the system will reduce the pesticide use, environmental pollution will be also less proportionally (37. Materials and Methods In order to evaluate the yield, yield components and potential weeds control under intercropping fenugreek and anise, an experiment was carried out based on a randomized complete block design with three replicationsat the Agricultural Research Field of Yasouj University during growing season of 2012-2013. Treatments included pure cultures of fenugreek and anise, single-row, double-row and three-tier intercropping of fenugreek and anise at no weed control and weed control conditions. Results and Discussion The results showed that different intercropping treatments had significant effects on pod number per plant, grain weight and grain and biological yield of fenugreek and also, on number of lateral branches, number of grains per plant and grain and biological yield of anise. There were nosignificant effects on plant height, number of lateral branches, number of grain per pod, harvest index of fenugreek, as well as plant height, number of umbel let per plant, seed weight and harvest index of anise. The

  3. Role of co-occurring competition and facilitation in plant spacing hydrodynamics in water-limited environments.

    Science.gov (United States)

    Trautz, Andrew C; Illangasekare, Tissa H; Rodriguez-Iturbe, Ignacio

    2017-08-29

    Plant performance (i.e., fecundity, growth, survival) depends on an individual's access to space and resources. At the community level, plant performance is reflected in observable vegetation patterning (i.e., spacing distance, density) often controlled by limiting resources. Resource availability is, in turn, strongly dependent on plant patterning mediated by competitive and facilitative plant-plant interactions. Co-occurring competition and facilitation has never been specifically investigated from a hydrodynamic perspective. To address this knowledge gap, and to overcome limitations of field studies, three intermediate-scale laboratory experiments were conducted using a climate-controlled wind tunnel-porous media test facility to simulate the soil-plant-atmosphere continuum. The spacing between two synthetic plants, a design consideration introduced by the authors in a recent publication, was varied between experiments; edaphic and mean atmospheric conditions were held constant. The strength of the above- and belowground plant-plant interactions changed with spacing distance, allowing the creation of a hydrodynamic conceptual model based on established ecological theories. Greatest soil water loss was observed for the experiment with the smallest spacing where competition dominated. Facilitation dominated at the intermediate spacing; little to no interactions were observed for the largest plant spacing. Results suggest that there exists an optimal spacing distance range that lowers plant environmental stress, thus improving plant performance through reduced atmospheric demand and conservation of available soil water. These findings may provide a foundation for improving our understanding of many climatological, ecohydrological, and hydrological problems pertaining to the hydrodynamics of water-limited environments where plant-plant interactions and community self-organization are important.

  4. Microwave Technologies as Part of an Integrated Weed Management Strategy: A Review

    OpenAIRE

    Graham Brodie; Carmel Ryan; Carmel Lancaster

    2012-01-01

    Interest in controlling weed plants using radio frequency or microwave energy has been growing in recent years because of the growing concerns about herbicide resistance and chemical residues in the environment. This paper reviews the prospects of using microwave energy to manage weeds. Microwave energy effectively kills weed plants and their seeds; however, most studies have focused on applying the microwave energy over a sizable area, which requires about ten times the energy that is embodi...

  5. Modeling strategic competition in hydro-thermal electricity generation markets with cascaded reservoir-hydroelectric generation plants

    Science.gov (United States)

    Uluca, Basak

    This dissertation aims to achieve two goals. The first is to model the strategic interactions of firms that own cascaded reservoir-hydro plants in oligopolistic and mixed oligopolistic hydrothermal electricity generation markets. Although competition in thermal generation has been extensively modeled since the beginning of deregulation, the literature on competition in hydro generation is still limited; in particular, equilibrium models of oligopoly that study the competitive behavior of firms that own reservoir-hydro plants along the same river in hydrothermal electricity generation markets are still under development. In competitive markets, when the reservoirs are located along the same river, the water released from an upstream reservoir for electricity generation becomes input to the immediate downstream reservoir, which may be owned by a competitor, for current or future use. To capture the strategic interactions among firms with cascaded reservoir-hydro plants, the Upstream-Conjecture approach is proposed. Under the Upstream-Conjecture approach, a firm with an upstream reservoir-hydro plant assumes that firms with downstream reservoir-hydro plants will respond to changes in the upstream firm's water release by adjusting their water release by the same amount. The results of the Upstream Conjecture experiments indicate that firms that own upstream reservoirs in a cascade may have incentive to withhold or limit hydro generation, forcing a reduction in the utilization of the downstream hydro generation plants that are owned by competitors. Introducing competition to hydroelectricity generation markets is challenging and ownership allocation of the previously state-owned cascaded reservoir-hydro plants through privatization can have significant impact on the competitiveness of the generation market. The second goal of the dissertation is to extract empirical guidance about best policy choices for the ownership of the state-owned generation plants, including the

  6. Modelling the effects of plant facilitation-competition mechanisms on semiarid landscape co-evolution

    Science.gov (United States)

    Saco, Patricia M.

    2015-04-01

    Semiarid landscapes function as tightly coupled systems with strong biogeomorphic feedbacks. Worldwide, a vast portion of these areas are covered by patchy vegetation consisting of mixed herbaceous and woody plant species that interact exhibiting both competition and facilitation effects. Though the role of facilitative interactions in plant communities has received considerable attention in the last two decades, their effects on the coevolution of landscapes are still not clearly understood. Here a modelling framework is used to investigate the effects of facilitative interactions among vegetation species, as well as their role on the coevolution of water redistribution, vegetation patterns, and landforms. The model simulates the dynamics of and interactions between coexisting grasses and shrubs under varying competition-facilitation conditions. We explore facilitation effects associated with changes in micro environmental conditions for water availability in dry environments focussing on the role of infiltration enhancement and shading effects. Field experiments have shown that in many semiarid environments vegetation enhances infiltration. However, herbaceous and woody plants seem to have varying hydrologic traits in different areas and it is therefore not clear which species has the greatest contribution to infiltration enhancement. This study tests alternative hypothesis, varying the relative contributions to total infiltration of both species, through a sensitivity analysis of the key parameters affecting infiltration. We analyze the results by examining the simulated spatial patterns of biomass density, soil moisture and erosion. Results indicate that final vegetation cover structure and hydrologic connectivity strongly depend on the facilitation mechanisms included in the model. We find that the removal of woody species can lead to alternative steady states, including an increase on herbaceous cover, which is the expected outcome of these management

  7. Study of Canopy Structure and Growth Characters Role of Two Wheat Cultivars in Competition, on Economic Threshold and Yield of Rye and Wild Mustard

    Directory of Open Access Journals (Sweden)

    B. Saadatian

    2012-04-01

    Full Text Available To evaluate the role of effective factors on competition of two wheat cultivars against two species of narrow leaf and broad leaf weeds this study was conducted as two separated experiments based on a randomized complete block design with 3 replications at Agricultural Faculty of Bu-Ali Sina University, in 2008-2009. In both Experiments, Alvand and Sayson cultivars were planted with densities of 450 plants m-2. In the 1st experiment, rye with densities of 0, 20, 40, 60 and 80 plants m-2 were planted in inter-rows of wheat. In the 2nd experiment, wild mustard densities were 0, 8, 16, 24 and 32 plants m-2. The results showed that characters such as vertical distribution of leaf area index and dry matter, height and its increase rate in interference, emergence rate, rate of canopy development and precocity led to increasing competitive ability of Alvand than Sayson in competition with two weed species. These factors were effective in reduction seed production of weeds and economic threshold in Alvand. Despite of lower height of wild mustard than rye, distribution of leaf area and canopy structure of wild mustard increased light competition ability and shadow on crop, so that harmful effects of individual plant of wild mustard in different densities was more than rye. Increasing rate of wild mustard seed bank was more than ray.

  8. Dinamica y manejo de poblaciones de malas hierbas Dynamics and management of weed populations

    Directory of Open Access Journals (Sweden)

    Milagros S. Saavedra

    1994-01-01

    Full Text Available El presente trabajo es una revisión de la modelización de estudios de dinámica de poblaciones de malas hierbas, que fue presentada como ponencia en el XVIII Congresso Brasile iro de Herbicida s e Plant as Daninh as en 1991, Brasília. Partiendo de la población, como unidad básica de los ecosistemas agrarios, se relacionan diferentes modelos de dinámica incluyendo el fenómeno de competencia intra específica, la evolución del banco de semillas y aplicaciones a la asociación cultivo y mala hierba. A través de los diagramas de ciclos vitales, que relacionan los estados funcionales y los procesos demográficos, se llega al establecimiento del modelo matricial.This literature review is a report about the study model of weed population dynamics, which was presented at the XVIII Congress of the Brazilian Weed Science Society, held in Brasilia, Brazil, 1991. Starting from population as the basic block of farm ecosystems, different models of dynamics are related, including the phenomenon of intraspecific competition, the evolution of seed banks, and applications to the weed/crop asso ciation. Through life cycle diagrams, which relates the functional status and the demographic processes, it is possible to achieve a matricial model.

  9. Planting date impacts on soil water management, plant growth, and weeds in cover-crop-based no-till corn production

    Science.gov (United States)

    Low input and organic farmers are increasingly utilizing cover crop mulches in maize production. Many farmers are delaying planting corn into these high residue environments to allow greater growth of the cover crop to maximize nitrogen fixation and improve mechanical termination with roller crimpe...

  10. 36 CFR 222.8 - Cooperation in control of estray or unbranded livestock, animal diseases, noxious farm weeds, and...

    Science.gov (United States)

    2010-07-01

    ... estray or unbranded livestock, animal diseases, noxious farm weeds, and use of pesticides. 222.8 Section... unbranded livestock, animal diseases, noxious farm weeds, and use of pesticides. (a) Insofar as it involves... farm weeds. (2) The Animal and Plant Health Inspection Service and other Federal or State agencies and...

  11. Temperature-dependent performance of competitive native and alien invasive plant species

    Science.gov (United States)

    Song, Uhram

    2017-10-01

    To assess the likely impacts of environmental change, the responses of two well-known invasive plant species, native Pueraria lobata and alien Humulus japonicus, to differences in growth temperature were studied in South Korea. Habitat preferences, physiological responses such as photosynthetic rates and chlorophyll contents, growth rates, and nutrient contents were quantified for each species. A competition experiment was conducted to evaluate the temperature preferences of the two species. All results indicated that the alien species H. japonicus can take advantage of elevated temperatures (35 °C) to enhance its competitive advantage against the native species P. lobata. While H. japonicus took advantage of elevated temperatures and preferred high-temperature areas, P. lobata showed reduced performance and dominance in high-temperature areas. Therefore, in future, due to global warming and urbanization, there are possibilities that H. japonicus takes advantage of elevated temperature against P. lobata that could lead to increased H. japonicus coverage over time. Therefore, consistent monitoring of both species especially where P. lobata is dominated are required because both species are found in every continents in the world. Controlling P. lobata requires thorough inspection of H. japonicus presence of the habitat in advance to prevent post P. lobata management invasion of H. japonicus.

  12. Colonisation and competition dynamics can explain incomplete sterilisation parasitism in ant-plant symbioses.

    Science.gov (United States)

    Tarnita, Corina E; Palmer, Todd M; Pringle, Robert M

    2014-10-01

    Sterilisation of parasites prevents host reproduction, thereby diverting host resources to their own benefit. Previous theory predicts that parasites should evolve maximum virulence, yet hosts are often incompletely sterilised. Whereas prior attempts to resolve this paradox have sought evolutionary explanations, we present theory and experiments showing that incomplete sterilisation can arise from ecologically driven fluctuations in parasite load. The African ant-plant Acacia drepanolobium reproduced more when occupied by small colonies of the sterilising symbiont Crematogaster nigriceps. In nature, small colonies result from interference competition between ant colonies; these territorial conflicts thus provide intermittent windows of opportunity for host reproduction. Our mean-field model shows that numerical insufficiency of parasites can produce partial sterilisation of host populations, creating the appearance of reduced virulence even if ants have evolved to sterilise completely. This general framework helps explain both the apparent ubiquity of partial sterilisation parasitism and the ability of these symbiotic associations to persist.

  13. Competitive sorption-desorption behavior of triazine herbicides with plant cuticular fractions.

    Science.gov (United States)

    Shechter, Michal; Xing, Baoshan; Kopinke, Frank-Dieter; Chefetz, Benny

    2006-10-04

    Sorption interactions of plant cuticular matter with organic compounds are not yet fully understood. The objective of this study was to examine the competitive sorption-desorption interactions of the triazine herbicides (atrazine and ametryn) with cuticular fractions isolated from tomato fruits and leaves of Agave americana. The 13C NMR data suggest a rubber-like nature for the cutin. This biopolymer exhibited reversible and noncompetitive sorption. Enhanced desorption of atrazine was recorded in the bi-solute system with bulk and dewaxed A. americana cuticles. 13C NMR analyses of these samples suggested that the sorbed competitor ametryn facilitated a physical phase transition of rigid paraffinic sorption domain to mobile and flexible domain during sorption process. We suggest that the different sorption-desorption behavior obtained for the two cuticles is related to the higher content of waxes (14% vs 2.6%) and lower content of cutin (46% vs 75%) in the A. americana versus tomato fruit cuticle.

  14. Transdisciplinary weed research: new leverage on challenging weed problems?

    NARCIS (Netherlands)

    Jordan, N.; Schut, M.; Graham, S.; Barney, J.N.; Childs, D.Z.; Christensen, S.B.; Cousens, R.D.; Davis, A.S.; Eizenberg, H.; Ervin, D.E.; Fernandez-Quintanilla, C.; Harrison, L.J.; Harsch, M.A.; Heijting, S.; Liebman, M.; Loddo, D.; Mirsky, S.B.; Riemens, M.; Neve, P.; Peltzer, D.A.; Renton, M.; Williams, M.; Recasens, J.; Sønderskov, M.

    2016-01-01

    Transdisciplinary weed research (TWR) is a promising path to more effective management of challenging weed problems. We define TWR as an integrated process of inquiry and action that addresses complex weed problems in the context of broader efforts to improve economic, environmental and social

  15. Transdisciplinary weed research: new leverage on challenging weed problems?

    Science.gov (United States)

    Transdisciplinary Weed Research (TWR) is a promising path to more effective management of challenging weed problems. We define TWR as an integrated process of inquiry and action that addresses complex weed problems in the context of broader efforts to improve economic, environmental and social aspec...

  16. 宝天曼自然保护区杂木林群落的植物特征分析%Plant feature analyses of weed-tree forest community of Baotianman Nature Reserve

    Institute of Scientific and Technical Information of China (English)

    王文静; 李先芳

    2001-01-01

    There are 667 species of higher plants belonging to 334 genus, 114 families,making up respectively 51.12% of family,34.33% genus and 24.60% of species in Baotianman Nature Reserve;They make up 5.47% of family,25% of genus and 14.02% of species of higher plants in Henan Province.The superior families composing weed-tree forest plants are Rosaccac, Compositae,Gramineae, Leguminosac,adding up to 199 species, accounting for 32.4% of total angiosperm in this area.The main content of this weed-tree forest plants is temperate zone combined with some tropical types, which embodies the transitional quality,borderline quality,diversity and unique quality of plants in the area showing the cross in many ways and ancient specific property.The vertical distribution of this weed-tree forest community is comparatively obvious.%宝天曼自然保护区约有高等植物114科、334属、667种及变种,分别占宝天曼自然保护区植物科的51.12%,属的34.33%,种的24.60%;占河南高等植物科的5.47%,属的25%和种的14.02%.组成本区杂木林植物的优势科有蔷薇科、菊科、禾本科、豆科等4科,合计199种,占本区被子植物总种数的32.4%.杂木林植物以温带成分为主,兼有一定热带分布类群,它体现了本区植物区系的过渡性、边缘性、多样性和独特性,显示出多方交汇和一定的古老性。本区杂木林群落垂直分布比较明显.

  17. Wild onion (Asphodelus tenuifolius) competition in rainfed chickpea-chickpea cropping system

    OpenAIRE

    SIBTAIN,M.; Tanveer,A.; Javaid,M.M; Ali,H.H.

    2015-01-01

    Chickpea yield potential is limited by weed competition in typical chickpea growing areas of Pakistan where zero tillage crop grown on moisture conserved from rains received during the months of September and August. The objective of this work was to evaluate the growth and yield characteristics of chickpea grown in coexistence with increasing densities of wild onion (Asphodelus tenuifolius). The experiment was comprised of six density levels viz. zero, 20, 40, 80, 160 and 320 plants m-2 of A...

  18. Grass and weed killer poisoning

    Science.gov (United States)

    ... medlineplus.gov/ency/article/002838.htm Grass and weed killer poisoning To use the sharing features on this page, please enable JavaScript. Many weed killers contain dangerous chemicals that are harmful if ...

  19. Photosynthetic characteristics of hybrid and conventional rice plants as a function of plant competition Características fotossintéticas de plantas de arroz híbridas e convencionais em função da intensidade de competição

    Directory of Open Access Journals (Sweden)

    G Concenço

    2011-12-01

    Full Text Available The objective of this work was to evaluate the characteristics related to the photosynthetic ability of hybrid and inbred rice varieties, as a way to assess which of the two presented higher potential to stand out under conditions of competition. The trial was set in a greenhouse in completely randomized block design and 2 x 6 factorial scheme with four replications. Factor A consisted of rice varieties (hybrid or inbred and factor B by competition levels. Treatments consisted in maintaining one plant of either BRS Pelota (inbred or Inov (hybrid variety at the center of the plot, under competition with 0, 1, 2, 3, 4 or 5 plants of the variety BRS Pelota at the periphery of the experimental unit, according to the treatment. Fifty days after emergence (DAE, sub-stomatal CO2 concentration (Ci - mmol mol-1, photosynthetic rate (A - mmol m-2 s-1 and CO2 consumed (DC - mmol mol-1 were quantified, as well as shoot dry mass(SDM.Hybrid plants present higher photosynthesis capacity than inbred plants, when competing with up to 3 times its own density. When under the same competitive intensity, hybrid plants surpass the inbred. However, it should be emphasized that, when in farm condition, the lower competitive capacity with weeds often attributed to the hybrid varieties, probably is due to their lower planting density, but if weed competition is kept at low levels, hybrid rice plants may perform in the same way or usually better than inbred plants.Objetivou-se com este estudo avaliar características relacionadas a capacidade fotossintética de variedades de arroz híbridas e convencionais, de forma a quantificar seu potencial de competição. O experimento foi instalado em casa de vegetação em delineamento experimental de blocos casualizados e esquema fatorial 2 x 6, com quatro repetições. O fator A consistiu de variedades de arroz (convencional e híbrida e o fator B de níveis de competição. Os tratamentos consistiram em manter uma planta da

  20. Potencial alelopático de plantas de acapu (Vouacapoua americana: efeitos sobre plantas daninhas de pastagens Allelopathic potential of "acapu" (Vouacapoua americana plants: effects on pasture weed

    Directory of Open Access Journals (Sweden)

    A.P.S. Souza Filho

    2000-01-01

    Full Text Available Extratos aquosos de folhas e cascas de plantas de acapu (Vouacapoua americana foram preparados nas concentrações de 0, 1, 2, 3 e 5% (v/v, visando identificar e caracterizar a atividade potencialmente alelopática dessa espécie. Analisaram-se os efeitos dos extratos sobre a germinação de sementes e o alongamento da raiz primária das plantas daninhas malícia (Mimosa pudica e malva (Urena lobata. Os bioensaios de germinação foram desenvolvidos em condições de 25 ºC e fotoperíodo de 12 horas. Para os bioensaios de alongamento da raiz primária, as condições estabelecidas foram de 25 ºC e fotoperíodo de 24 horas. Os resultados obtidos indicaram variações de respostas em função da fonte do extrato aquoso, do parâmetro analisado e da concentração do extrato. As reduções observadas tanto na germinação como no alongamento da raiz primária foram crescentes com o aumento da concentração do extrato, sendo os efeitos mais intensos observados na concentração de 5%. Independentemente da espécie receptora e do parâmetro analisado, o extrato preparado a partir das cascas do acapu evidenciou maior atividade alelopática inibitória. O alongamento da raiz primária foi o parâmetro mais sensível aos efeitos potencialmente alelopáticos do que a germinação das sementes. Comparativamente, cascas e folhas apresentaram diferenças em relação às classes de substâncias químicas. Nas cascas foram encontradas cumarinas que não estavam presentes nas folhas, as quais, por sua vez, apresentaram esteróides e triterpenóides, que não foram identificados nas cascas do acapu.Aqueous extracts from leaves and bark of "Acapu" plants were prepared in concentration levels of 0, 1, 2, 3 and 5% to identify and characterize potential allelopathic activity of such plants. The extract effects on seed germination and primary root elongation of pasture weeds, such as Mimosa pudica and Urena lobata, were analyzed. The germination bioassays were

  1. THE PERFORMANCE OF SOYBEAN (GLYCINE MAX (L. MERRILL UNDER VARYING WEEDING REGIMES IN SOUTH WESTERN NIGERIA

    Directory of Open Access Journals (Sweden)

    F. O. ODELEYE

    2007-08-01

    Full Text Available Two field trials were conducted at the Teaching and Research Farm, the University of Ibadan, Ibadan, in 1999 and 2001, to study the performance of two soybean cultivars subjected to varying weeding regimes, viz: no weeding, weeding at 2 and 4 weeks after sowing (WAS, 2 and 6 WAS and 2 and 8 WAS. The experiments were a factorial combination of variety and weeding regimes in randomized complete block design with four replications. Data were taken at maturity on some vegetative, dry matter and yield parameters. The competing weeds were also identified, sampled, dried and weighed. Data were analyzed using ANOVA and means separated by LSD (P=0.05. Results showed that weeds did not adversely affect the performance of the two soybean varieties at 2 WAS. In addition, two weedings were adequate for the two soybean varieties but the interval of weeding was absolutely important in yield determination. The growth stage when these weeds prove to be harmful competition on soybeans, as evidenced from the results of this study, was between 4 and 6 WAS. The results also showed that plots left unwedded inevitably had the highest yield reduction in both varieties. On the other hand, plots weeded at 2 and 6 WAS showed the best performance in all aspects for both varieties of soybean, than other weeding regimes. It is clear from this study, therefore, that weeding at 2 and 6 WAS ensured that most parts of vegetative and reproductive stages were weed-free, so that in conclusion, weeding soybean crop twice is appropriate using the 2 and 6 WAS sequence, for optimum performance in south west Nigeria.

  2. Assessment of Corn Densities on Ecological Indices of Weed Species

    Directory of Open Access Journals (Sweden)

    G Mahmoodi

    2012-06-01

    Full Text Available Diversity, dominance, and stability of weeds are the most important ecological properties in agricultural systems, which influenced by management factors such as crop density, abundantly. This experiment was conducted in 2009 at Ferdowsi University of Mashhad Research Field. The experimental design was interval mapping with four levels of corn densities (5, 6, 7 and 9 plant.m-2 and four levels of weed control (full-control, without control, broad-leaves control and grasses control. Weed sampling was done at 3 stages included beginning and end of critical period weed control and harvesting time. The results showed that the effect of plant density on species diversity was significant; some how the amount of Shanon and Simpson Indices were lowest in the 9 plant.m-2 (0.39 and 0.45, respectively and greatest in 5 plant.m-2 (0.84. The results also showed that the maximum amount of dominance index was observed in 9 plant.m-2, that was seen in Echinochloa crus- galli and Convulvulus arvensis at the beginning of growing season, then in Solanum nigrum and Amaranthus retroflexus in the end of growing season. The amount of community dominance index in 9 plant.m-2 was higher than other densities, and it decreased with decline of densities. based on the results of present experiment the linear relationship between plant species and area was found. The calculated amount of Alpha and Beta diversities. in a θ and β scales based on coefficients of this relationship were 0.534 (four species per unit area and 0.29 (two species per unit area, respectively. In conclusion the result of this experiment pointed that the weeds diversity decreased with increasing of corn density, weed diversity decreased and therefore, having appropriate plant density is very efficient for sustainable weed management.

  3. Differences in competitive ability between plants from nonnative and native populations of a tropical invader relates to adaptive responses in abiotic and biotic environments.

    Directory of Open Access Journals (Sweden)

    Zhi-Yong Liao

    Full Text Available The evolution of competitive ability of invasive plant species is generally studied in the context of adaptive responses to novel biotic environments (enemy release in introduced ranges. However, invasive plants may also respond to novel abiotic environments. Here we studied differences in competitive ability between Chromolaena odorata plants of populations from nonnative versus native ranges, considering biogeographical differences in both biotic and abiotic environments. An intraspecific competition experiment was conducted at two nutrient levels in a common garden. In both low and high nutrient treatments, C. odorata plants from nonnative ranges showed consistently lower root to shoot ratios than did plants from native ranges grown in both monoculture and competition. In the low nutrient treatment, C. odorata plants from nonnative ranges showed significantly lower competitive ability (competition-driven decreases in plant height and biomass were more, which was associated with their lower root to shoot ratios and higher total leaf phenolic content (defense trait. In the high nutrient treatment, C. odorata plants from nonnative ranges showed lower leaf toughness and cellulosic contents (defense traits but similar competitive ability compared with plants from native ranges, which was also associated with their lower root to shoot ratios. Our results indicate that genetically based shifts in biomass allocation (responses to abiotic environments also influence competitive abilities of invasive plants, and provide a first potential mechanism for the interaction between range and environment (environment-dependent difference between ranges.

  4. Influencia de las malezas sobre el cultivo de frijol en función de espaciamiento y de la densidad de plantas Weeds influence in common bean as a function of spacing and plant density

    Directory of Open Access Journals (Sweden)

    M.C Parreira

    2011-12-01

    .45 and 0.60 m in two plant densities amounts per seed, 10 and 15 plants per meter. For each row spacing and seed density, the experimental design used was the randomized blocks, with four repetitions per treatment. Grain yield of the crop showed decreases of 16, 40, 36 and 58% when the coexistence with the weed was during all the cycle of the crop for row spacing of 0,45 m and seeding density of 10 and 15 plants per meter; and row spacing of 0,60 m and seeding density of 10 and 15 plants per meter, respectively. The period prior to weed interference (PPI occurred in 28, 26, 22 e 14 days after crop emergence, respectively.

  5. Biology, ecology and management of the invasive parthenium weed (Parthenium hysterophorus L.).

    Science.gov (United States)

    Adkins, Steve; Shabbir, Asad

    2014-07-01

    Parthenium weed (Parthenium hysterophorus L.) is one of the most aggressive invasive weeds, threatening natural ecosystems and agroecosystems in over 30 countries worldwide. Parthenium weed causes losses of crops and pastures, degrading the biodiversity of natural plant communities, causing human and animal health hazards and resulting in serious economic losses to people and their interests in many countries around the globe. Several of its biological and ecological attributes contribute towards its invasiveness. Various management approaches (namely cultural, mechanical, chemical and biological control) have been used to minimise losses caused by this weed, but most of these approaches are ineffective and uneconomical and/or have limitations. Although chemical control using herbicides and biological control utilising exotic insects and pathogens have been found to contribute to the management of the weed, the weed nevertheless remains a significant problem. An integrated management approach is proposed here for the effective management of parthenium weed on a sustainable basis. © 2014 Society of Chemical Industry.

  6. Effect of Establishment Methods and Weed Management Practices on Some Growth Attributes of Rice

    Institute of Scientific and Technical Information of China (English)

    Mohammad Safdar BALOCH; Inayat Ullah AWAN; Gul HASSAN; Abdul Aziz KHAKWANI

    2006-01-01

    Studies were carried out for two years to evaluate the effect of methods of sowing and weed control practices on the productivity of transplanted and direct wet-seeded rice in Dera Ismail Khan, NWFP, Pakistan. The experiment was laid out in a randomized complete block design with a split plot arrangement. The planting techniques viz. transplanting and direct seeding were maintained in main plots while weed control practices included the use of granular herbicide Sunstar 15WG (ethoxy sulfuron),Machete 60EC (butachlor), conventional hand weeding, and the weedy check (control) were assigned to the sub-plots. Data were recorded on weed parameters like weed density and dry weed biomass 60 and 90 days after sowing (DAS); agronomic parameters including plant population, number of panicles and paddy yield and physiological parameters like leaf area index and net assimilation rate 45 and 90 DAS. The planting methods and weed management significantly influenced most of the parameters studied. The data revealed that the paddy yield and its components were significantly higher in the transplanted method than that in direct-seeded method, while the weed density and biomass were lower in the transplanted plots than the direct-seeded plots.Among weed management tools, the maximum paddy yield was obtained in hand weeding, closely followed by herbicide application Machete 60EC during both cropping seasons.

  7. INVASIVE WEEDS IN BOGOR BOTANIC GARDENS, INDONESIA AND ITS IMPLICATION ON SURROUNDING LANDSCAPES

    Directory of Open Access Journals (Sweden)

    Edi Santosa

    2014-07-01

    Full Text Available Conservation areas with the objective for collection and exchange plant materials have been speculated as weed bank for surrounding areas. Objective of this study was to identify and characterize ruderal invasive weeds in the Bogor Botanic Gardens (BBG. Observations were conducted in all vak (collection blocks in the BBG in order to identify the weeds species, determine their invasiveness, dominance and distribution. Weeds associations with host plants were observed. Current weed control program and data of dead trees collection were analyzed in relevant to weed. Distribution of weeds outside BBG was observed by transects method following river and road directions. Results showed that there were seven invasive weeds, i.e., Cecropia adenopus (Cecropiaceae, Cissus nodosa Blume (Vitaceae, Cissus sicyoides Blume (Vitaceae, Dioscorea bulbifera L. (Dioscoreaceae, Ficus elastica Roxb. (Moraceae, Mikania micrantha H.B.K. (Asteraceae and Paraserianthes falcataria (L. Nielsen (Fabaceae. These seven weeds species invaded 41 out of 215 plant families in BBG. Six species of weeds, i.e., C. adenopus, C. nodosa Blume., C. sicyoides Blume., D. bulbifera L., M. micrantha H.B.K. and P. falcataria (L. Nielsen, were introduced as BBG collections for the first time while the F. elastica Roxb was considered as native. It is most likely that the weeds dispersal agents are the wind, birds, bats, visitors, and waters. All of these weeds existed in surrounding areas outside BBG. Given the detrimental impact of invasive weeds on the plant collection in BBG, it is necessary to develop long–term comprehensive control measures both inside and neighboring areas by involving other government authorities beyond BBG.

  8. Weed management in tropical turfgrass areas: A review

    Directory of Open Access Journals (Sweden)

    Uddin Kamal M.D.

    2012-01-01

    Full Text Available Cultural practices promoting vigorous, environmentally friendly dense turf are discussed. These are the most important and least recognized means of preventing weed establishment and encroachment which includes appropriate propagation material selection, sanitation and cultivation, adjustment of planting time, manual weed control (hand pulling, hoeing and rouging, turfgrass selection to better compete with weed populations, applying physiological stresses, fertilizer management, moisture management, mowing, and irrigation with salt water. Cultural management of weed is important because it reduces dependence on synthetic pesticides. A healthy turfgrass stand has been reported to be the best defense against weed colonization, and can be accomplished by proper mowing, watering, and fertilization. Mowing height is the clearest and best-documented cultural factor and a lower mowing height is always associated with more weeds in the turfgrass. Split application of fertilizer at intervals throughout the growing period is recommended for warm season turfgrasses. The application of fertilizer during dormant periods or periods of low growth may encourage weed growth. Hand pulling and hoeing effectively control annual and biennial seedling weeds for small areas. Irrigation by saltwater has been one method used recently to effectively control grassy broadleaved and sedge weeds in salt-tolerant turfgrass species. Cultural weed management practices in turf might provide a first defense: however, relying only on cultural control measures may not be a good idea. An integrated approach of combining cultural practices and chemicals can complement each other and give flexibility to decision making. Research is needed on optimizing the choices of herbicide and/or cultural practices as part of an integrated management system for turfgrass.

  9. Weed Identification Using An Automated Active Shape Matching (AASM) Technique

    DEFF Research Database (Denmark)

    Swain, K C; Nørremark, Michael; Jørgensen, R N

    2011-01-01

    Weed identification and control is a challenge for intercultural operations in agriculture. As an alternative to chemical pest control, a smart weed identification technique followed by mechanical weed control system could be developed. The proposed smart identification technique works...... on the concept of ‘active shape modelling’ to identify weed and crop plants based on their morphology. The automated active shape matching system (AASM) technique consisted of, i) a Pixelink camera ii) an LTI (Lehrstuhlfuer technische informatik) image processing library, iii) a laptop pc with the Linux OS. A 2......-leaf growth stage model for Solanum nigrum L. (nightshade) is generated from 32 segmented training images in Matlab software environment. Using the AASM algorithm, the leaf model was aligned and placed at the centre of the target plant and a model deformation process carried out. The parameters used...

  10. Using vegetation indices as input into ramdom forest for soybean and weed classification

    Science.gov (United States)

    Weed management is a major component of a soybean (Glycine max L.) production system; thus, managers need tools to help them distinguish soybean from weeds. Vegetation indices derived from light reflectance properties of plants have shown promise as tools to enhance differences among plants. The o...

  11. An invasive clonal plant benefits from clonal integration more than a co-occurring native plant in nutrient-patchy and competitive environments.

    Science.gov (United States)

    You, Wenhua; Fan, Shufeng; Yu, Dan; Xie, Dong; Liu, Chunhua

    2014-01-01

    Many notorious invasive plants are clonal, however, little is known about the different roles of clonal integration effects between invasive and native plants. Here, we hypothesize that clonal integration affect growth, photosynthetic performance, biomass allocation and thus competitive ability of invasive and native clonal plants, and invasive clonal plants benefit from clonal integration more than co-occurring native plants in heterogeneous habitats. To test these hypotheses, two stoloniferous clonal plants, Alternanthera philoxeroides (invasive), Jussiaea repens (native) were studied in China. The apical parts of both species were grown either with or without neighboring vegetation and the basal parts without competitors were in nutrient- rich or -poor habitats, with stolon connections were either severed or kept intact. Competition significantly reduced growth and photosynthetic performance of the apical ramets in both species, but not the biomass of neighboring vegetation. Without competition, clonal integration greatly improved the growth and photosynthetic performance of both species, especially when the basal parts were in nutrient-rich habitats. When grown with neighboring vegetation, growth of J. repens and photosynthetic performance of both species were significantly enhanced by clonal integration with the basal parts in both nutrient-rich and -poor habitats, while growth and relative neighbor effect (RNE) of A. philoxeroides were greatly improved by clonal integration only when the basal parts were in nutrient-rich habitats. Moreover, clonal integration increased A. philoxeroides's biomass allocation to roots without competition, but decreased it with competition, especially when the basal ramets were in nutrient-rich sections. Effects of clonal integration on biomass allocation of J. repens was similar to that of A. philoxeroides but with less significance. These results supported our hypothesis that invasive clonal plants A. philoxeroides benefits

  12. Biomass of tree species as a response to planting density and interspecific competition

    Directory of Open Access Journals (Sweden)

    Paulo Sérgio Lima e Silva

    2014-04-01

    Full Text Available Planting trees is an important way to promote the recovery of degraded areas in the Caatinga region. Experiments (E1, E2, and E3 were conducted in a randomized blocks design, with three, three, and five replicates, respectively. The objectives were to evaluate biomass of the shoots of: a gliricidia (G and sabiá (S, as a response to planting density; b G, S, and neem (N in competition; c G, and S in agroforestry. E1 was conducted in split-plots, and planting densities (400, 600, 800, 1000, and 1200 plants ha-1 as subplots. E2 consisted of a factorial comprising the following plots: GGG, NGN, SGS, NNN, GNG, SNS, SSS, GSG, NSN (each letter represents a row of plants. E3 was conducted with G and S in agroforestry experiment. The trees were harvested after 54, 42, and 27 months old, in E1, E2 and E3, respectively. In E1, G presented higher green biomass of the stems and leaf at smaller densities than S, but lower green biomass of branches at most densities. The species did not differ for mean stem dry biomass and leaf dry biomass, but G showed higher branch dry biomass at most densities. Higher planting densities increased green and dry biomass of stems, branches, and leaves in S, but decreased those characteristics in G, with the exception of leaf dry mass, which was not influenced by density. In E2, the behavior of each species was identical in plots containing the same or different species. Griricidia showed the highest green biomass of stems and branches, and the highest values for geren biomass of the leaf were observed for gliricidia and neem. The highest stem, branch, and leaf dry biomass values were obtained for G, S, and N, respectively. In E3, G was superior for stem and leaf green biomass, and for stem and branch dry biomass. There were no differences between species for the other biomass values.

  13. Visitantes florais de plantas invasoras de áreas com fruteiras irrigadas Floral visitors of weed plants of irrigated orchard areas

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    Lúcia Helena Piedade Kiill

    2000-09-01

    Full Text Available As plantas invasoras afetam a produtividade das fruteiras irrigadas, sendo necessários estudos sobre sua ecologia, principalmente formas de reprodução e associação com insetos. O presente trabalho foi desenvolvido em Petrolina-PE, objetivando classificar os visitantes florais de plantas invasoras em polinizadores e pilhadores, de acordo com o comportamento apresentado. As observações foram feitas de maio a outubro de 1998, em 26 dias não consecutivos, no intervalo das 7h00 às 16h00. As invasoras foram classificadas em nectaríferas e poliníferas, quando visitadas para retirada exclusiva de néctar ou de pólen; e em mistas, quando visitadas para retirada dos dois recursos. Para a análise de freqüência foi adotado um sistema de notas: a- número de visitas >30, b- entre 10 e 30 e c- Weeds can impair yield of irrigated fruit crops, studies about their ecology being needed, especially ways of reproduction and association with insects. This work was carried out in Petrolina, PE, Brazil with the objective of identifying the floral visitors of weeds, and classifying them as pollinators and pollen and/or nectar thieves, according to their behavior. The observations were made between May and October of 1998, in 26 not consecutive days, between 7:00 am and 4:00 pm. The weeds were classified in nectariferous and polliniferous when these were visited exclusively for collection of nectar or pollen, and mixed when these were visited to collect both. A grade system was adopted for the frequency evaluation: a- number of visits >30, b - between 10 to 30, c - <10. Among the 24 weeds observed, 14 were classified as nectariferous, six as polliniferous and four were considered mixed. Among the floral visitors, the following bees were registered (Xylocopa grisescens, X. frontalis, Centris aff. perforator, Ptilotrix aff. plumata, Diadasina riparia, Apis mellifera, Trigona spinipes, Eulaema nigrita, butterflies (Ascia monuste, Papilio thoas brasiliensis

  14. Scaling from individual plants to the globe in an Earth System Model: height structured competition and carbon cycling

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    Weng, E.; Malyshev, S.; Lichstein, J. W.; Farrior, C. E.; Dybzinski, R.; Zhang, T.; Shevliakova, E.; Pacala, S. W.

    2014-12-01

    The long-term and large scale dynamics of ecosystems are in large part determined by the performances of individual plants in competition with one another for light, water and nutrients. Woody biomass, a pool of carbon (C) larger than that in the atmosphere, exists because of height-structured competition for light. However, none of the current Earth System Models that predict climate change and C cycle feedbacks includes a mechanistic formulation for height-structured competition for light, or an explicit scaling from individual plants to the globe. In this study, we incorporate height-structured competition and explicit scaling from individuals to ecosystems into the land model (LM3) currently used in the Earth System Models developed by the Geophysical Fluid Dynamics Laboratory based on the Perfect Plasticity Approximation model (PPA), which has been shown to scale accurately from individual plants to stands in individual-based simulation models of plant competition for light, water and nutrients. Because of the tractability of the PPA, the coupled LM3-PPA model is able to include a large number of phenomena across a range of spatial and temporal scales, and still retain computational and mathematical tractability. We test a range of predictions against data from the temperate forests in northern USA. The results show the model predictions agree with diurnal and annual C fluxes, growth rates of individual trees in the canopy and understory, tree size distributions, and species-level population dynamics during succession. We also show how the competitively optimal allocation strategy shifts at different atmospheric CO2 concentrations due to competition with alternative strategies in the model. The results show that the competitively optimal allocation of carbon to leaves, wood, and fine roots depends on the atmospheric CO2 concentration, and that C sinks caused by CO2 fertilization in forests limited by light and water are down-regulated if allocation tracks

  15. Forest roadsides harbour less competitive habitats for a relict mountain plant (Pulsatilla vernalis) in lowlands

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    Zielińska, Katarzyna M.; Kiedrzyński, Marcin; Grzyl, Andrzej; Rewicz, Agnieszka

    2016-08-01

    The long-term survival of relict populations depends on the accessibility of appropriate sites (microrefugia). In recent times, due to the mass extinction of rare species that has resulted from the loss of natural habitats, the question is – Are there any human-made sites that can act as refugial habitats? We examined forest roadside populations of the mountain plant Pulsatilla vernalis in the last large lowland refugium in Central Europe. We compared the habitat conditions and community structure of roadsides with P. vernalis against the forest interior. Light availability and bryophyte composition were the main factors that distinguished roadsides. Pulsatilla occurred on sites that had more light than the forest interior, but were also more or less shaded by trees, so more light came as one-side illumination from the road. Roadsides had also a lower coverage of bryophytes that formed large, dense carpets. At the same time, they were characterised by a greater richness of vascular plants and ‘small’ bryophytes, which corresponds to a higher frequency of disturbances. In a warming and more fertile Anthropocene world, competition plays the main role in the transformation of forest communities, which is why relict populations have found refugia in extensively disturbed human-made habitats.

  16. Coevolution between invasive and native plants driven by chemical competition and soil biota.

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    Lankau, Richard A

    2012-07-10

    Although reciprocal evolutionary responses between interacting species are a driving force behind the diversity of life, pairwise coevolution between plant competitors has received less attention than other species interactions and has been considered relatively less important in explaining ecological patterns. However, the success of species transported across biogeographic boundaries suggests a stronger role for evolutionary relationships in shaping plant interactions. Alliaria petiolata is a Eurasian species that has invaded North American forest understories, where it competes with native understory species in part by producing compounds that directly and indirectly slow the growth of competing species. Here I show that populations of A. petiolata from areas with a greater density of interspecific competitors invest more in a toxic allelochemical under common conditions. Furthermore, populations of a native competitor from areas with highly toxic invaders are more tolerant to competition from the invader, suggesting coevolutionary dynamics between the species. Field reciprocal transplants confirmed that native populations more tolerant to the invader had higher fitness when the invader was common, but these traits came at a cost when the invader was rare. Exotic species are often detrimentally dominant in their new range due to their evolutionary novelty; however, the development of new coevolutionary relationships may act to integrate exotic species into native communities.

  17. An invasive plant promotes its arbuscular mycorrhizal symbioses and competitiveness through its secondary metabolites: indirect evidence from activated carbon.

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    Yuan, Yongge; Tang, Jianjun; Leng, Dong; Hu, Shuijin; Yong, Jean W H; Chen, Xin

    2014-01-01

    Secondary metabolites released by invasive plants can increase their competitive ability by affecting native plants, herbivores, and pathogens at the invaded land. Whether these secondary metabolites affect the invasive plant itself, directly or indirectly through microorganisms, however, has not been well documented. Here we tested whether activated carbon (AC), a well-known absorbent for secondary metabolites, affect arbuscular mycorrhizal (AM) symbioses and competitive ability in an invasive plant. We conducted three experiments (experiments 1-3) with the invasive forb Solidago canadensis and the native Kummerowia striata. Experiment 1 determined whether AC altered soil properties, levels of the main secondary metabolites in the soil, plant growth, and AMF communities associated with S. canadensis and K. striata. Experiment 2 determined whether AC affected colonization of S. canadensis by five AMF, which were added to sterilized soil. Experiment 3 determined the competitive ability of S. canadensis in the presence and absence of AMF and AC. In experiment 1, AC greatly decreased the concentrations of the main secondary metabolites in soil, and the changes in concentrations were closely related with the changes of AMF in S. canadensis roots. In experiment 2, AC inhibited the AMF Glomus versiforme and G. geosporum but promoted G. mosseae and G. diaphanum in the soil and also in S. canadensis roots. In experiment 3, AC reduced S. canadensis competitive ability in the presence but not in the absence of AMF. Our results provided indirect evidence that the secondary metabolites (which can be absorbed by AC) of the invasive plant S. canadensis may promote S. canadensis competitiveness by enhancing its own AMF symbionts.

  18. Weed Biomass and Weed Species Diversity of Juvenile Citrus Trees Intercrop with some Arable Crops

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    Patience Mojibade OLORUNMAIYE

    2012-02-01

    Full Text Available A preliminary study was carried out to evaluate the performances of eight crops in the intercrop of citrus with arable crops at the National Horticultural Research Institute (NIHORT Ibadan, Nigeria. Eight arable crops: maize, cucumber, sweet potato, Corchorus olitorius, large green, grain amaranth, Mucuna pruriens var. utilis, and groundnut were intercropped with young citrus trees in the early planting season of 2010 with sole citrus as control. The experiment was laid out in a completely randomized block design with three replicates. Data were collected on weed flora, weed density and weed dry weight. Results showed that the relative frequencies of weeds in all the plots were less than 4% at both 6 and 9WAP. Gomphrena celosoides, Oldenlandia corymbosa and Tridax procumbens were most preponderant in appearing in all the plots. Tridax procumbens had a consistent relative frequency (2.34% in all the plots except in citrus/maize plot (0.78% at 9 WAP. Significantly lower broadleaf weed densities were obtained in citrus/sweet potato, citrus/large green, control plot and citrus/cucumber (28.67, 45.00, 50.00 and 76.33 m-2 respectively than in citrus/groundnut plot (143.00 m-2. Similarly, significantly lower grass weed densities were produced in citrus/Mucuna and citrus/sweet potato (0.33 m-2 each plots than the control plot (11.33 m-2. Whereas citrus/corchorus plot produced significantly lower broadleaf weed dry weight (37.59 g m-2 than citrus/Mucuna plot (126.47 g m-2 at 3WAP, citrus/large green plot (16.15 g m-2 and citrus/groundnut plot (123.25 g m-2 followed the same trend at 6 WAP. Sedges dry weights were less than 7 g m-2 in all the plots compared with control plot.

  19. Weed Biomass and Weed Species Diversity of Juvenile Citrus Trees Intercrop with some Arable Crops

    Directory of Open Access Journals (Sweden)

    Patience Mojibade OLORUNMAIYE

    2012-02-01

    Full Text Available A preliminary study was carried out to evaluate the performances of eight crops in the intercrop of citrus with arable crops at the National Horticultural Research Institute (NIHORT Ibadan, Nigeria. Eight arable crops: maize, cucumber, sweet potato, Corchorus olitorius, large green, grain amaranth, Mucuna pruriens var. utilis, and groundnut were intercropped with young citrus trees in the early planting season of 2010 with sole citrus as control. The experiment was laid out in a completely randomized block design with three replicates. Data were collected on weed flora, weed density and weed dry weight. Results showed that the relative frequencies of weeds in all the plots were less than 4% at both 6 and 9WAP. Gomphrena celosoides, Oldenlandia corymbosa and Tridax procumbens were most preponderant in appearing in all the plots. Tridax procumbens had a consistent relative frequency (2.34% in all the plots except in citrus/maize plot (0.78% at 9 WAP. Significantly lower broadleaf weed densities were obtained in citrus/sweet potato, citrus/large green, control plot and citrus/cucumber (28.67, 45.00, 50.00 and 76.33 m-2 respectively than in citrus/groundnut plot (143.00 m-2. Similarly, significantly lower grass weed densities were produced in citrus/Mucuna and citrus/sweet potato (0.33 m-2 each plots than the control plot (11.33 m-2. Whereas citrus/corchorus plot produced significantly lower broadleaf weed dry weight (37.59 g m-2 than citrus/Mucuna plot (126.47 g m-2 at 3WAP, citrus/large green plot (16.15 g m-2 and citrus/groundnut plot (123.25 g m-2 followed the same trend at 6 WAP. Sedges dry weights were less than 7 g m-2 in all the plots compared with control plot.

  20. Capabilities of unmanned aircraft vehicles for low altitude weed detection

    Science.gov (United States)

    Pflanz, Michael; Nordmeyer, Henning

    2014-05-01

    Sustainable crop production and food security require a consumer and environmental safe plant protection. It is recently known, that precise weed monitoring approaches could help apply pesticides corresponding to field variability. In this regard the site-specific weed management may contribute to an application of herbicides with higher ecologically aware and economical savings. First attempts of precision agriculture date back to the 1980's. Since that time, remote sensing from satellites or manned aircrafts have been investigated and used in agricultural practice, but are currently inadequate for the separation of weeds in an early growth stage from cultivated plants. In contrast, low-cost image capturing at low altitude from unmanned aircraft vehicles (UAV) provides higher spatial resolution and almost real-time processing. Particularly, rotary-wing aircrafts are suitable for precise path or stationary flight. This minimises motion blur and provides better image overlapping for stitching and mapping procedures. Through improved image analyses and the recent increase in the availability of microcontrollers and powerful batteries for UAVs, it can be expected that the spatial mapping of weeds will be enhanced in the future. A six rotors microcopter was equipped with a modified RGB camera taking images from agricultural fields. The hexacopter operates within predefined pathways at adjusted altitudes (from 5 to 10 m) by using GPS navigation. Different scenarios of optical weed detection have been carried out regarding to variable altitude, image resolution, weed and crop growth stages. Our experiences showed high capabilities for site-specific weed control. Image analyses with regard to recognition of weed patches can be used to adapt herbicide application to varying weed occurrence across a field.

  1. A Case Study of Allelopathic Effect on Weeds in Wheat

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    Slaveya T. Petrova

    2015-06-01

    Full Text Available Most powerful and effective method of weed control is by chemical substances called herbicides. In recent years, they were published quite data on different side effects of herbicides on humans, animals, crops and the environment as a whole. Therefore, the increased interest for biological weed control lately is reasonable, since its improvement and expansion will contribute to limiting excessive use of herbicides, respectively their harmful effects and will support the successful implementation of complex weed control. The purpose of this study was to investigate the effect of selected plant species, containing allelopathic active substances, on germination, growth and biomass of some widespread weeds in wheat. Experiments were carried out at laboratory conditions using seeds of wheat (Triticum aestivum L., sort Sadovo 1 and most common weeds therein: Johnson grass (Sorghum halepense (L Pers, white pigweed (Chenopodium album L., twitch (Cynodon dactylon L. and curly dock (Rumex crispus L.. Allelopathic substances were extracted with distilled water from flowers of lavender (Lavandula angustifolia Mill., leaves of basil (Ocimum basilicum L., leaves of spearmint (Mentha longifolia (L Huds., and leaves of peppermint (Mentha piperita L.. Of the tested active allelopathic plants, the most negative impact on germination of all weeds seeds (including wheat, as well as on the development of plants exhibited the water extract of lavender. Lavender and basil had a stronger negative effect on white pigweed and twitch compared with both mint species. A significant inhibitory effect of spearmint even at low concentrations was recorded on the germination of all weed species tested while the wheat was slightly affected, which manifests this plant as a potential effective species in strategies for weed control management.

  2. Broomrape Weeds. Underground Mechanisms of Parasitism and Associated Strategies for their Control: A Review.