Soil and Soil Water Relationships

OpenAIRE

Easton, Zachary M.; Bock, Emily

2017-01-01

Discusses the relationships between soil, water and plants. Discusses different types of soil, and how these soils hold water. Provides information about differences in soil drainage. Discusses the concept of water balance.

Effects of soil management techniques on soil water erosion in apricot orchards.

Science.gov (United States)

Keesstra, Saskia; Pereira, Paulo; Novara, Agata; Brevik, Eric C; Azorin-Molina, Cesar; Parras-Alcántara, Luis; Jordán, Antonio; Cerdà, Artemi

2016-05-01

Soil erosion is extreme in Mediterranean orchards due to management impact, high rainfall intensities, steep slopes and erodible parent material. Vall d'Albaida is a traditional fruit production area which, due to the Mediterranean climate and marly soils, produces sweet fruits. However, these highly productive soils are left bare under the prevailing land management and marly soils are vulnerable to soil water erosion when left bare. In this paper we study the impact of different agricultural land management strategies on soil properties (bulk density, soil organic matter, soil moisture), soil water erosion and runoff, by means of simulated rainfall experiments and soil analyses. Three representative land managements (tillage/herbicide/covered with vegetation) were selected, where 20 paired plots (60 plots) were established to determine soil losses and runoff. The simulated rainfall was carried out at 55mmh(-1) in the summer of 2013 (soil moisture) for one hour on 0.25m(2) circular plots. The results showed that vegetation cover, soil moisture and organic matter were significantly higher in covered plots than in tilled and herbicide treated plots. However, runoff coefficient, total runoff, sediment yield and soil erosion were significantly higher in herbicide treated plots compared to the others. Runoff sediment concentration was significantly higher in tilled plots. The lowest values were identified in covered plots. Overall, tillage, but especially herbicide treatment, decreased vegetation cover, soil moisture, soil organic matter, and increased bulk density, runoff coefficient, total runoff, sediment yield and soil erosion. Soil erosion was extremely high in herbicide plots with 0.91Mgha(-1)h(-1) of soil lost; in the tilled fields erosion rates were lower with 0.51Mgha(-1)h(-1). Covered soil showed an erosion rate of 0.02Mgha(-1)h(-1). These results showed that agricultural management influenced water and sediment dynamics and that tillage and herbicide

Characteristics of soil under variations in clay, water saturation, and water flow rates, and the implications upon soil remediation

International Nuclear Information System (INIS)

Aikman, M.; Mirotchnik, K.; Kantzas, A.

1997-01-01

A potential remediation method for hydrocarbon contaminated soils was discussed. The new method was based on the use of proven and economic petroleum reservoir engineering methods for soil remediation. The methods that were applied included water and gas displacement methods together with horizontal boreholes as the flow inlet and outlets. This system could be used in the case of spills that seep beneath a plant or other immovable infrastructure which requires in-situ treatment schemes to decontaminate the soil. A study was conducted to characterize native soils and water samples from industrial plants in central Alberta and Sarnia, Ontario and to determine the variables that impact upon the flow conditions of synthetic test materials. The methods used to characterize the soils included X-Ray computed tomographic analysis, grain size and density measurements, and X-Ray diffraction. Clay content, initial water saturation, and water and gas flow rate were the variables that impacted on the flow conditions

Theory study of global density influence and soils chemical composition at neutron probes response

International Nuclear Information System (INIS)

Crispino, M.L.

1980-06-01

Three energy group diffusion theory is applied to calculate the thermal neutron flux through a soil-water mixture at the neutron source. The soils studies are taken from two horizons of different composition, of a representative soil of the Litoral-Mata Zone of Pernambuco State. The thermal flux is obtained taking into consideration increasing values of the water volume percent, H, and the bulk density of the soil. The cross-sections of the mixture are calculated from the chemical composition of the soils. (author)

Concurrent temporal stability of the apparent electrical conductivity and soil water content

Science.gov (United States)

Knowledge of spatio-temporal soil water content (SWC) variability within agricultural fields is useful to improve crop management. Spatial patterns of soil water contents can be characterized using the temporal stability analysis, however high density sampling is required. Soil apparent electrical c...

Physical and water properties of selected Polish heavy soils of various origins

Directory of Open Access Journals (Sweden)

Kaczmarek Zbigniew

2015-12-01

Full Text Available The paper presents the characteristics of selected physical, chemical, and water properties of four mineral arable soils characterized with heavy and very heavy texture. Soil samples from genetic horizons of black earths from areas near Kętrzyn, Gniew and Kujawy, and alluvial soils from Żuławy were used. The following properties were determined in the samples of undisturbed and disturbed structure: texture, particle density, bulk density, porosity, natural and hygroscopic moistures, maximal hygroscopic capacity, saturated hydraulic conductivity, potential of water bonding in soil, total and readily available water, total retention in the horizon of 0–50 cm, drainage porosity, content of organic carbon and total nitrogen Parent rocks of these soils were clays, silts and loams of various origin. High content of clay fraction strongly influenced the values of all the analyzed properties. All the examined soils had high content of organic carbon and total nitrogen and reaction close to neutral or alkaline. High content of mineral and organic colloids and, what follows, beneficial state of top horizons’ structure, determined – apart from heavy texture – low soil bulk density and high porosity. The investigated soils were characterized by high field water capacity and wide scopes of total and readily available water. The saturated hydraulic conductivity was low and characteristic to heavy mineral arable soils. The parameter which influenced the variability of analyzed parameters most was texture.

Soil water repellency at old crude oil spill sites

International Nuclear Information System (INIS)

Roy, J.L.

1999-08-01

This thesis presents the current state of knowledge regarding the cause of soil water repellency and characterizes disaggregated nonwettable surface soils found at old crude oil spill sites. Pollution-induced water repellency generally develops following prolonged exposures of soil to liquid- or vapour-phase petroleum hydrocarbons. The condition varies significantly in terms of severity and persistence. Soil water repellency retards plant growth and disturbs the hydrological balance of ecosystems. Disaggregated water-repellent soils are also very susceptible to dispersal by erosion, posing a threat to the productivity of surrounding soils. The author described the probable causes of soil water repellency under the following three main themes: (1) accumulation of hydrophobic organic material in soil, (2) redistribution and re-organisation of this material in soil, and (3) stabilisation of the hydrophobic organic material. This final process is necessary to ensure persistence of induced water repellency symptoms. Petroleum residues as water-repellent substances in weathered nonwettable oil-contaminated soils were also discussed and a hypothesis about soil water repellency was presented which deals with flexible conformation in organic matter coatings. Processes leading to the development of soil water repellency following crude oil contamination were also described. It was determined that soil water repellency is a function of the packing density and the chain conformation of amphiphilic organic molecules in the outermost layer of soil organic matter coatings. This research suggests that the fractional coverage of alkyl chains on soil particle surfaces determines the degree of water repellency that is displayed by soil. It was shown that prompt remediation of some oil-contaminated plots can effectively prevent the development of soil water repellency. 4 refs., 32 tabs., 22 figs., 5 appendices

Density and water content measurement with two dual detector probes

International Nuclear Information System (INIS)

Cariou, J.; Menard, J.

1980-01-01

The ''Laboratoires des Ponts et Chaussees'' have developed an electronic device for geological prospections. This system includes gamma-gamma and neutron-neutron probes for continuous measurement in borehole down to one hundred meters. It is used, as well to measure the density and the water content in the field of soil mechanic engineering. When the diameter is not constant all along the borehole the two probes have to use a dual detector procedure. When constant, a simple detector procedure is sufficient to obtain density and water content. Two examples show the possibilities of this apparatus, particularly to control the borehole diameter and the soil chemical composition [fr

DOES EARTHWORMS DENSITY REALLY MODIFY SOIL'S HYDRODYNAMIC PROPERTIES IN IRRIGATED SYSTEMS WITH RECYCLED WATER?

Directory of Open Access Journals (Sweden)

N. Ababsa

2016-05-01

Full Text Available Our study has the general objective to understand the impact of the valuation of treated water on earthworm abundance and total porosity of the soil and the effect of the interaction between these two physical-biological components of the hydrological functioning of soils. It was carried out on the meadows soils of the valley of Wadi Bousselam.Although the treated water has high organic and particulate filler, it improved the earthworm abundance, total porosity and hydraulic conductivity of the soil.

Three Principles of Water Flow in Soils

Science.gov (United States)

Guo, L.; Lin, H.

2016-12-01

Knowledge of water flow in soils is crucial to understanding terrestrial hydrological cycle, surface energy balance, biogeochemical dynamics, ecosystem services, contaminant transport, and many other Critical Zone processes. However, due to the complex and dynamic nature of non-uniform flow, reconstruction and prediction of water flow in natural soils remain challenging. This study synthesizes three principles of water flow in soils that can improve modeling water flow in soils of various complexity. The first principle, known as the Darcy's law, came to light in the 19th century and suggested a linear relationship between water flux density and hydraulic gradient, which was modified by Buckingham for unsaturated soils. Combining mass balance and the Buckingham-Darcy's law, L.A. Richards quantitatively described soil water change with space and time, i.e., Richards equation. The second principle was proposed by L.A. Richards in the 20th century, which described the minimum pressure potential needed to overcome surface tension of fluid and initiate water flow through soil-air interface. This study extends this principle to encompass soil hydrologic phenomena related to varied interfaces and microscopic features and provides a more cohesive explanation of hysteresis, hydrophobicity, and threshold behavior when water moves through layered soils. The third principle is emerging in the 21st century, which highlights the complex and evolving flow networks embedded in heterogeneous soils. This principle is summarized as: Water moves non-uniformly in natural soils with a dual-flow regime, i.e., it follows the least-resistant or preferred paths when "pushed" (e.g., by storms) or "attracted" (e.g., by plants) or "restricted" (e.g., by bedrock), but moves diffusively into the matrix when "relaxed" (e.g., at rest) or "touched" (e.g., adsorption). The first principle is a macroscopic view of steady-state water flow, the second principle is a microscopic view of interface

Root water extraction and limiting soil hydraulic conditions estimated by numerical simulation

NARCIS (Netherlands)

Jong van Lier, de Q.; Metselaar, K.; Dam, van J.C.

2006-01-01

Root density, soil hydraulic functions, and hydraulic head gradients play an important role in the determination of transpiration-rate-limiting soil water contents. We developed an implicit numerical root water extraction model to solve the Richards equation for the modeling of radial root water

Correcting the error in neutron moisture probe measurements caused by a water density gradient

International Nuclear Information System (INIS)

Wilson, D.J.

1988-01-01

If a neutron probe lies in or near a water density gradient, the probe may register a water density different to that at the measuring point. The effect of a thin stratum of soil containing an excess or depletion of water at various distances from a probe in an otherwise homogeneous system has been calculated, producing an 'importance' curve. The effect of these strata can be integrated over the soil region in close proximity to the probe resulting in the net effect of the presence of a water density gradient. In practice, the probe is scanned through the point of interest and the count rate at that point is corrected for the influence of the water density on each side of it. An example shows that the technique can reduce an error of 10 per cent to about 2 per cent

Estimating the amount and distribution of radon flux density from the soil surface in China

International Nuclear Information System (INIS)

Zhuo Weihai; Guo Qiuju; Chen Bo; Cheng Guan

2008-01-01

Based on an idealized model, both the annual and the seasonal radon ( 222 Rn) flux densities from the soil surface at 1099 sites in China were estimated by linking a database of soil 226 Ra content and a global ecosystems database. Digital maps of the 222 Rn flux density in China were constructed in a spatial resolution of 25 km x 25 km by interpolation among the estimated data. An area-weighted annual average 222 Rn flux density from the soil surface across China was estimated to be 29.7 ± 9.4 mBq m -2 s -1 . Both regional and seasonal variations in the 222 Rn flux densities are significant in China. Annual average flux densities in the southeastern and northwestern China are generally higher than those in other regions of China, because of high soil 226 Ra content in the southeastern area and high soil aridity in the northwestern one. The seasonal average flux density is generally higher in summer/spring than winter, since relatively higher soil temperature and lower soil water saturation in summer/spring than other seasons are common in China

Fly ash dynamics in soil-water systems

International Nuclear Information System (INIS)

Sharma, S.; Fulekar, M.H.; Jayalakshmi, C.P.

1989-01-01

Studies regarding the effluents and coal ashes (or fly ash) resulting from coal burning are numerous, but their disposal and interactions with the soil and water systems and their detailed environmental impact assessment with concrete status reports on a global scale are scanty. Fly ash dynamics in soil and water systems are reviewed. After detailing the physical composition of fly ash, physicochemical changes in soil properties due to fly ash amendment are summarized. Areas covered include texture and bulk density, moisture retention, change in chemical equilibria, and effects of fly ash on soil microorganisms. Plant growth in amended soils is discussed, as well as plant uptake and accumulation of trace elements. In order to analyze the effect of fly ash on the physicochemical properties of water, several factors must be considered, including surface morphology of fly ash, pH of the ash sluice water, pH adjustments, leachability and solubility, and suspended ash and settling. The dynamics of fly ash in water systems is important due to pollution of groundwater resources from toxic components such as trace metals. Other factors summarized are bioaccumulation and biomagnification, human health effects of contaminants, and the impact of radionuclides in fly ash. Future research needs should focus on reduction of the environmental impact of fly ash and increasing utilization of fly ash as a soil amendment. 110 refs., 2 figs., 10 tabs

Seasonal variations in soil water in two woodland savannas of central Brazil with different fire history.

Science.gov (United States)

Quesada, Carlos Alberto; Hodnett, Martin G; Breyer, Lacê M; Santos, Alexandre J B; Andrade, Sérgio; Miranda, Heloisa S; Miranda, Antonio Carlos; Lloyd, Jon

2008-03-01

Changes in soil water content were determined in two cerrado (sensu stricto) areas with contrasting fire history and woody vegetation density. The study was undertaken near Brasília, Brazil, from 1999 to 2001. Soil water content was measured with a neutron probe in three access tubes per site to a depth of 4.7 m. One site has been protected from fire for more than 30 years and, as a consequence, has a high density of woody plants. The other site had been frequently burned, and has a high herbaceous vegetation density and less woody vegetation. Soil water uptake patterns were strongly seasonal, and despite similarities in hydrological processes, the protected area systematically used more water than the burned area. Three temporarily contiguous patterns of water absorption were differentiated, characterized by variation in the soil depth from which water was extracted. In the early dry season, vegetation used water from throughout the soil profile but with a slight preference for water in the upper soil layers. Toward the peak of the dry season, vegetation had used most or all available water from the surface to a depth of 1.7 m, but continued to extract water from greater depths. Following the first rains, all water used was from the recently wetted upper soil layers only. Evaporation rates were a linear function of soil water availability, indicating a strong coupling of atmospheric water demand and the physiological response of the vegetation.

Predicting soil particle density from clay and soil organic matter contents

DEFF Research Database (Denmark)

Schjønning, Per; McBride, R.A.; Keller, T.

2017-01-01

Soil particle density (Dp) is an important soil property for calculating soil porosity expressions. However, many studies assume a constant value, typically 2.65Mgm−3 for arable, mineral soils. Fewmodels exist for the prediction of Dp from soil organic matter (SOM) content. We hypothesized...

Percolation behavior of tritiated water into a soil packed bed

Energy Technology Data Exchange (ETDEWEB)

Honda, T.; Katayama, K.; Uehara, K.; Fukada, S. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka (Japan); Takeishi, T. [Faculty of Engineering, Kyushu University, Motooka Nishi-ku, Fukuoka (Japan)

2015-03-15

A large amount of cooling water is used in a D-T fusion reactor. The cooling water will contain tritium with high concentration because tritium can permeate metal walls at high temperature easily. A development of tritium handling technology for confining tritiated water in the fusion facility is an important issue. In addition, it is also important to understand tritium behavior in environment assuming severe accidents. In this study, percolation experiments of tritiated water in soil packed bed were carried out and tritium behavior in soil was discussed. Six soil samples were collected in Hakozaki campus of Kyushu University. These particle densities were of the same degree as that of general soils and moisture contents were related to BET surface area. For two soil samples used in the percolation experiment of tritiated water, saturated hydraulic conductivity agreed well with the estimating value by Creager. Tritium retention ratio in the soil packed bed was larger than water retention. This is considered to be due to an effect of tritium sorption on the surface of soil particles. The isotope exchange capacity estimated by assuming that H/T ratio of supplied tritiated water and H/T ratio of surface water of soil particle was equal was comparable to that on cement paste and mortar which were obtained by exposure of tritiated water vapor. (authors)

Percolation behavior of tritiated water into a soil packed bed

International Nuclear Information System (INIS)

Honda, T.; Katayama, K.; Uehara, K.; Fukada, S.; Takeishi, T.

2015-01-01

A large amount of cooling water is used in a D-T fusion reactor. The cooling water will contain tritium with high concentration because tritium can permeate metal walls at high temperature easily. A development of tritium handling technology for confining tritiated water in the fusion facility is an important issue. In addition, it is also important to understand tritium behavior in environment assuming severe accidents. In this study, percolation experiments of tritiated water in soil packed bed were carried out and tritium behavior in soil was discussed. Six soil samples were collected in Hakozaki campus of Kyushu University. These particle densities were of the same degree as that of general soils and moisture contents were related to BET surface area. For two soil samples used in the percolation experiment of tritiated water, saturated hydraulic conductivity agreed well with the estimating value by Creager. Tritium retention ratio in the soil packed bed was larger than water retention. This is considered to be due to an effect of tritium sorption on the surface of soil particles. The isotope exchange capacity estimated by assuming that H/T ratio of supplied tritiated water and H/T ratio of surface water of soil particle was equal was comparable to that on cement paste and mortar which were obtained by exposure of tritiated water vapor. (authors)

Gamma-ray attenuation to measure water contents and/or bulk densities of porous materials

International Nuclear Information System (INIS)

Ferraz, E.S.B.

1983-01-01

Attenuation of gamma radiation during transmission through soil and porous materials has been used for approximately three decades as a method for determining volumetric water content, theta, and bulk density, rho. This method is particularly suited for laboratory determinations of theta and rho in soil columns but it also has been used with success under field conditions. Measurements of attentuation of a collimated beam of monoernergetic gamma-rays has been used successfully by many investigators to provide rapid, non-destructive determinations for small volumes of soil. For stable soils, i.e. soils which do not swell upon wetting or shrink upon drying, rho may be assumed to remain constant during water flow through the soil, and thus changes in intensity or transmitted radiation may be attributed to changes in water content, theta. However, for unstable soils, the dry bulk density is subject to change with time during water flow through the soil and cannot be assumed to be a constant. Several investigators have utilized either a single beam of dual-energy gamma photons or two separate monoenergetic photon beams with greatly different energies to simultaneously determine theta and rho in these soils. A general review of gamma-ray attenuation methods for determining theta and rho in laboratory soil cores and in field soil profiles is reported in this paper. Theoretical equations for transmission and attenuation of gamma radiation in soils are presented for both single and double beams of gamma photons. Sensitivity, precision, accuracy, and experimental errors for the method are evaluated and discussed with respect to the theory. (author)

Soil tension mediates isotope fractionation during soil water evaporation

Science.gov (United States)

Gaj, Marcel; McDonnell, Jeffrey

2017-04-01

Isotope tracing of the water cycle is increasing in its use and usefulness. Many new studies are extracting soil waters and relating these to streamflow, groundwater recharge and plant transpiration. Nevertheless, unlike isotope fractionation factors from open water bodies, soil water fractionation factors are poorly understood and until now, only empirically derived. In contrast to open water evaporation where temperature, humidity and vapor pressure gradient define fractionation (as codified in the well-known Craig and Gordon model), soil water evaporation includes additionally, fractionation by matrix effects. There is yet no physical explanation of kinetic and equilibrium fraction from soil water within the soil profile. Here we present a simple laboratory experiment with four admixtures of soil grain size (from sand to silt to clay). Oven-dried samples were spiked with water of known isotopic composition at different soil water contents. Soils were then stored in sealed bags and the headspace filled with dry air and allowed to equilibrate for 24hours. Isotopic analysis of the headspace vapor was done with a Los Gatos Inc. water vapor isotope analyzer. Soil water potential of subsamples were measured with a water potential meter. We show for the first time that soil tension controls isotope fractionation in the resident soil water. Below a Pf 3.5 the δ-values of 18O and 2H of the headspace vapor is more positive and increases with increasing soil water potential. Surprisingly, we find that the relationship between soil tension and equilibrium fractionation is independent of soil type. However, δ-values of each soil type plot along a distinct evaporation line. These results indicate that equilibrium fractionation is affected by soil tension in addition to temperature. Therefore, at high soil water tension (under dry conditions) equilibrium fractionation is not consistent with current empirical formulations that ignore these effects. These findings may have

Modelling soil-water dynamics in the rootzone of structured and water-repellent soils

Science.gov (United States)

Brown, Hamish; Carrick, Sam; Müller, Karin; Thomas, Steve; Sharp, Joanna; Cichota, Rogerio; Holzworth, Dean; Clothier, Brent

2018-04-01

In modelling the hydrology of Earth's critical zone, there are two major challenges. The first is to understand and model the processes of infiltration, runoff, redistribution and root-water uptake in structured soils that exhibit preferential flows through macropore networks. The other challenge is to parametrise and model the impact of ephemeral hydrophobicity of water-repellent soils. Here we have developed a soil-water model, which is based on physical principles, yet possesses simple functionality to enable easier parameterisation, so as to predict soil-water dynamics in structured soils displaying time-varying degrees of hydrophobicity. Our model, WEIRDO (Water Evapotranspiration Infiltration Redistribution Drainage runOff), has been developed in the APSIM Next Generation platform (Agricultural Production Systems sIMulation). The model operates on an hourly time-step. The repository for this open-source code is https://github.com/APSIMInitiative/ApsimX. We have carried out sensitivity tests to show how WEIRDO predicts infiltration, drainage, redistribution, transpiration and soil-water evaporation for three distinctly different soil textures displaying differing hydraulic properties. These three soils were drawn from the UNSODA (Unsaturated SOil hydraulic Database) soils database of the United States Department of Agriculture (USDA). We show how preferential flow process and hydrophobicity determine the spatio-temporal pattern of soil-water dynamics. Finally, we have validated WEIRDO by comparing its predictions against three years of soil-water content measurements made under an irrigated alfalfa (Medicago sativa L.) trial. The results provide validation of the model's ability to simulate soil-water dynamics in structured soils.

Soil map density and a nation's wealth and income

NARCIS (Netherlands)

Hartemink, A.E.

2008-01-01

Little effort has been made to link soil mapping and soil data density to a nation’s welfare. Soil map density in 31 European countries and 44 low and middle income countries is linked to Gross Domestic Product (GDP) per capita and the number of soil scientists per country.

Fertilization increases paddy soil organic carbon density*

Science.gov (United States)

Wang, Shao-xian; Liang, Xin-qiang; Luo, Qi-xiang; Fan, Fang; Chen, Ying-xu; Li, Zu-zhang; Sun, Huo-xi; Dai, Tian-fang; Wan, Jun-nan; Li, Xiao-jun

2012-01-01

Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC. PMID:22467369

Fertilization increases paddy soil organic carbon density.

Science.gov (United States)

Wang, Shao-xian; Liang, Xin-qiang; Luo, Qi-xiang; Fan, Fang; Chen, Ying-xu; Li, Zu-zhang; Sun, Huo-xi; Dai, Tian-fang; Wan, Jun-nan; Li, Xiao-jun

2012-04-01

Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC.

Soil water availability and rooting depth as determinants of hydraulic architecture of Patagonian woody species

Science.gov (United States)

Sandra J. Bucci; Fabian G. Scholz; Guillermo Goldstein; Frederick C. Meinzer; Maria E. Arce

2009-01-01

We studied the water economy of nine woody species differing in rooting depth in a Patagonian shrub steppe from southern Argentina to understand how soil water availability and rooting depth determine their hydraulic architecture. Soil water content and potentials, leaf water potentials (Leaf) hydraulic conductivity, wood density (Pw), rooting depth, and specific leaf...

Use of in situ volumetric water content at field capacity to improve prediction of soil water retention properties

OpenAIRE

Al Majou , Hassan; Bruand , Ary; Duval , Odile

2008-01-01

International audience; Use of in situ volumetric water content at field capacity to improve prediction of soil water retention properties. Most pedotransfer functions (PTFs) developed over the last three decades to generate water retention characteristics use soil texture, bulk density and organic carbon content as predictors. Despite of the high number of PTFs published, most being class- or continuous-PTFs, accuracy of prediction remains limited. In this study, we compared the performance ...

The effects of forward speed and depth of conservation tillage on soil bulk density

Directory of Open Access Journals (Sweden)

A Mahmoudi

2015-09-01

Full Text Available Introduction: In recent years, production techniques and equipment have been developed for conservation of tillage systems that have been adopted by many farmers. With proper management, overall yield averages for conventional and reduced tillage systems are nearly identical. Sometimes, field operations can be combined by connecting two or more implements. Combined operations reduce both fuel consumption, and time and labor requirements by eliminating at least one individual trip over the field. Light tillage, spraying, or fertilizing operations can be combined with either primary or secondary tillage or planting operations. Tillage helps seed growth and germination through providing appropriate conditions for soil to absorb sufficient temperature and humidity. Moreover, it helps easier development of root through reducing soil penetration resistance. Tillage is a time-consuming and expensive procedure. With the application of agricultural operations, we can save substantial amounts of fuel, time and energy consumption. Conservation tillage loosens the soil without turning, but by remaining the plant left overs, stems and roots. Bulk density reflects the soil’s ability to function for structural support, water and solute movement, and soil aeration. Bulk densities above thresholds indicate impaired function. Bulk density is also used to convert between weight and volume of soil. It is used to express soil physical, chemical and biological measurements on a volumetric basis for soil quality assessment and comparisons between management systems. This increases the validity of comparisons by removing the error associated with differences in soil density at the time of sampling. The aim of conservation tillage is to fix the soil structure. This investigation was carried out considering the advantages of conservation tillage and less scientific research works on imported conservation tillage devices and those which are made inside the country

Soil physics and the water management of spatially variable soils

International Nuclear Information System (INIS)

Youngs, E.G.

1983-01-01

The physics of macroscopic soil-water behaviour in inert porous materials has been developed by considering water flow to take place in a continuum. This requires the flow region to consist of an assembly of representative elementary volumes, repeated throughout space and small compared with the scale of observations. Soil-water behaviour in swelling soils may also be considered as a continuum phenomenon so long as the soil is saturated and swells and shrinks in the normal range. Macroscale heterogeneity superimposed on the inherent microscale heterogeneity can take many forms and may pose difficulties in the definition and measurement of soil physical properties and also in the development and use of predictive theories of soil-water behaviour. Thus, measurement techniques appropriate for uniform soils are often inappropriate, and criteria for soil-water management, obtained from theoretical considerations of behaviour in equivalent uniform soils, are not applicable without modification when there is soil heterogeneity. The spatial variability of soil-water properties is shown in results from field experiments concerned with water flow measurements; these illustrate both stochastic and deterministic heterogeneity in soil-water properties. Problems of water management of spatially variable soils when there is stochastic heterogeneity appear to present an insuperable problem in the application of theory. However, for soils showing deterministic heterogeneity, soil-water theory has been used in the solution of soil-water management problems. Thus, scaling using similar media theory has been applied to the infiltration of water into soils that vary over a catchment area. Also, the drain spacing to control the water-table height in soils in which the hydraulic conductivity varies with depth has been calculated using groundwater seepage theory. (author)

Comparison Of Selected Pedotransfer Functions For The Determination Of Soil Water Retention Curves

Directory of Open Access Journals (Sweden)

Kupec Michal

2015-09-01

Full Text Available Soil water retention curves were measured using a sandbox and the pressure plate extractor method on undisturbed soil samples from the Borská Lowland. The basic soil properties (e.g. soil texture, dry bulk density of the samples were determined. The soil water retention curve was described using the van Genuchten model (Van Genuchten, 1980. The parameters of the model were obtained using the RETC program (Van Genuchten et al., 1991. For the determination of the soil water retention curve parameters, two pedotransfer functions (PTF were also used that were derived for this area by Skalová (2003 and the Rosetta computer program (Schaap et al., 2001. The performance of the PTFs was characterized using the mean difference and root mean square error.

Sample sizes to control error estimates in determining soil bulk density in California forest soils

Science.gov (United States)

Youzhi Han; Jianwei Zhang; Kim G. Mattson; Weidong Zhang; Thomas A. Weber

2016-01-01

Characterizing forest soil properties with high variability is challenging, sometimes requiring large numbers of soil samples. Soil bulk density is a standard variable needed along with element concentrations to calculate nutrient pools. This study aimed to determine the optimal sample size, the number of observation (n), for predicting the soil bulk density with a...

Thermo physical properties of lateritic soil bricks: Influence of water content

International Nuclear Information System (INIS)

Meukam, P.; Noumowe, A.; Kofane, T.C.

2002-11-01

This paper presents an experimental study carried out in order to determine the properties of local materials used as construction materials. Cement stabilized compressed bricks were tested. The thermal properties of lateritic soil based materials were determined. The objectives of work reported in this paper are to determine the effect of addition of pozzolan or sawdust in lateritic soil brick on the thermal properties. It was shown that the effect of the incorporation of pozzolan or sawdust is the decreasing of the thermal conductivity and density. The moisture content of these materials can modify their thermal performance. Thus a study of the influence of the water content on the thermal conductivity k and the thermal diffusivity a is presented. The thermal conductivity, as a function of water content, increases rapidly between O% and 12% for lateritic soil. The thermal diffusivity curve presents a maximum for values of water content of 15% for lateritic soil and 8% for lateritic soil-pozzolan or lateritic soil- sawdust. (author)

Errors in determination of soil water content using time-domain reflectometry caused by soil compaction around wave guides

Energy Technology Data Exchange (ETDEWEB)

Ghezzehei, T.A.

2008-05-29

Application of time domain reflectometry (TDR) in soil hydrology often involves the conversion of TDR-measured dielectric permittivity to water content using universal calibration equations (empirical or physically based). Deviations of soil-specific calibrations from the universal calibrations have been noted and are usually attributed to peculiar composition of soil constituents, such as high content of clay and/or organic matter. Although it is recognized that soil disturbance by TDR waveguides may have impact on measurement errors, to our knowledge, there has not been any quantification of this effect. In this paper, we introduce a method that estimates this error by combining two models: one that describes soil compaction around cylindrical objects and another that translates change in bulk density to evolution of soil water retention characteristics. Our analysis indicates that the compaction pattern depends on the mechanical properties of the soil at the time of installation. The relative error in water content measurement depends on the compaction pattern as well as the water content and water retention properties of the soil. Illustrative calculations based on measured soil mechanical and hydrologic properties from the literature indicate that the measurement errors of using a standard three-prong TDR waveguide could be up to 10%. We also show that the error scales linearly with the ratio of rod radius to the interradius spacing.

Assessment the effect of homogenized soil on soil hydraulic properties and soil water transport

Science.gov (United States)

Mohawesh, O.; Janssen, M.; Maaitah, O.; Lennartz, B.

2017-09-01

Soil hydraulic properties play a crucial role in simulating water flow and contaminant transport. Soil hydraulic properties are commonly measured using homogenized soil samples. However, soil structure has a significant effect on the soil ability to retain and to conduct water, particularly in aggregated soils. In order to determine the effect of soil homogenization on soil hydraulic properties and soil water transport, undisturbed soil samples were carefully collected. Five different soil structures were identified: Angular-blocky, Crumble, Angular-blocky (different soil texture), Granular, and subangular-blocky. The soil hydraulic properties were determined for undisturbed and homogenized soil samples for each soil structure. The soil hydraulic properties were used to model soil water transport using HYDRUS-1D.The homogenized soil samples showed a significant increase in wide pores (wCP) and a decrease in narrow pores (nCP). The wCP increased by 95.6, 141.2, 391.6, 3.9, 261.3%, and nCP decreased by 69.5, 10.5, 33.8, 72.7, and 39.3% for homogenized soil samples compared to undisturbed soil samples. The soil water retention curves exhibited a significant decrease in water holding capacity for homogenized soil samples compared with the undisturbed soil samples. The homogenized soil samples showed also a decrease in soil hydraulic conductivity. The simulated results showed that water movement and distribution were affected by soil homogenizing. Moreover, soil homogenizing affected soil hydraulic properties and soil water transport. However, field studies are being needed to find the effect of these differences on water, chemical, and pollutant transport under several scenarios.

Impact of urban contamination of the La Paz River basin on thermotolerant coliform density and occurrence of multiple antibiotic resistant enteric pathogens in river water, irrigated soil and fresh vegetables.

Science.gov (United States)

Poma, Violeta; Mamani, Nataniel; Iñiguez, Volga

2016-01-01

La Paz River in Andean highlands is heavily polluted with urban run-off and further contaminates agricultural lowlands and downstream waters at the Amazon watershed. Agricultural produce at this region is the main source of vegetables for the major Andean cities of La Paz and El Alto. We conducted a 1 year study, to evaluate microbial quality parameters and occurrence of multiple enteropathogenic bacteria (Enterohemorrhagic E. coli-EHEC, Enteroinvasive E. coli or Shigella-EIEC/Shigella, Enteroaggregative E. coli-EAEC, Enteropathogenic E. coli-EPEC Enterotoxigenic E. coli-ETEC and Salmonella) and its resistance to 11 antibiotics. Four sampling locations were selected: a fresh mountain water reservoir (un-impacted, site 1) and downstream sites receiving wastewater discharges (impacted, sites 2-4). River water (sites 1-4, N = 48), and soil and vegetable samples (site 3, N = 24) were collected during dry (April-September) and rainy seasons (October-March). Throughout the study, thermotolerant coliform density values at impacted sites greatly exceeded the guidelines for recreational and agricultural water uses. Seasonal differences were found for thermotolerant coliform density during dry season in water samples nearby a populated and hospital compound area. In contrast to the un-impacted site, where none of the tested enteropathogens were found, 100 % of surface water, 83 % of soil and 67 % of vegetable samples at impacted sites, were contaminated with at least one enteropathogen, being ETEC and Salmonella the most frequently found. ETEC isolates displayed different patterns of toxin genes among sites. The occurrence of enteropathogens was associated with the thermotolerant coliform density. At impacted sites, multiple enteropathogens were frequently found during rainy season. Among isolated enteropathogens, 50 % were resistant to at least two antibiotics, with resistance to ampicillin, nalidixic acid, trimethoprim-sulfamethoxazole and tetracycline commonly

Water repellent soils: the case for unsaturated soil mechanics

Directory of Open Access Journals (Sweden)

Beckett Christopher

2016-01-01

Full Text Available Water repellent (or “hydrophobic” or “non-wetting” soils have been studied by soil scientists for well over a century. These soils are typified by poor water infiltration, which leads to increased soil erosion and poor crop growth. However, the importance of water repellence on determining soil properties is now becoming recognised by geotechnical engineers. Water repellent soils may, for example, offer novel solutions for the design of cover systems overlying municipal or mine waste storage facilities. However, investigations into factors affecting their mechanical properties have only recently been initiated. This purpose of this paper is to introduce geotechnical engineers to the concept of water repellent soils and to discuss how their properties can be evaluated under an unsaturated soils framework. Scenarios in which water repellent properties might be relevant in geotechnical applications are presented and methods to quantify these properties in the laboratory and in the field examined.

Effect of biochar on soil structural characteristics: water retention and gas transport

DEFF Research Database (Denmark)

Sun, Zhencai; Møldrup, Per; Vendelboe, Anders Lindblad

Biochar addition to agricultural soil has been reported to reduce climate gas emission, as well as improve soil fertility and crop productivity. Little, however, is known about biochar effects on soil structural characteristics. This study investigates if biochar-application changes soil structural...... characteristics, as indicated from water retention and gas transport measurements on intact soil samples. Soil was sampled from a field experiment on a sandy loam with four control plots (C) without biochar and four plots (B) with incorporated biochar at a rate of 20 tons per hectare (plot size, 6 x 8 m). The C......-gas diffusivity on intact 100cm3 soil samples (5 replicates in each plot). We found that biochar application significantly decreased soil bulk density, hereby creating higher porosity. At the same soil-water matric potential, all the soil-gas phase parameters (air-filled porosity, air permeability and gas...

Static and dynamic 3 dimensional studies of water in soil using computed tomographic scanning

International Nuclear Information System (INIS)

Crestana, S.; Mascarenhas, S.; Pozzi-Mucelli, R.S.

1984-03-01

Previous work of Petrovic, Siebert and Rieke demonstrated the possibility of using X-ray transmission computed tomography (CT) scanning for soil bulk density analysis in soil. We show in the present work that CT can also be used for the measurement of water content in soil. In our case we also show that CT can be applied to measure and follow dynamically the motion of water in soil in 3-dimensions. Further, more inhomogeneities of water content and motion in soil can be observed with this technique. Using a third generation CT scanner several different techniques can be applied such as differential, real time and spatial distribution scanning modes. A linear dependence was demonstrated for the Hounsfield Units (HU) used in CT and water content. The use of CT for water content and motion in soil in 3-dimensions opens new possibilities in this area of investigations. (author)

Study on Relationship between Dielectric Constant and Water Content of Rock-Soil Mixture by Time Domain Reflectometry

Directory of Open Access Journals (Sweden)

Daosheng Ling

2016-01-01

Full Text Available It is important to test water content of rock-soil mixtures efficiently and accurately to ensure both the quality control of compaction and assessment of the geotechnical engineering properties. To overcome time and energy wastage and probe insertion problems when using the traditional calibration method, a TDR coaxial test tube calibration arrangement using an upward infiltration method was designed. This arrangement was then used to study the influence of dry density, pore fluid conductivity, and soil/rock ratio on the relationship between water content and the dielectric constant of rock-soil mixtures. The results show that the empirical calibration equation forms for rock-soil mixtures can be the same as for soil materials. The effect of dry density on the calibration equation has the most significance and the influence of pore fluid conductivity can be ignored. The impact of variation of the soil/rock ratio can be neutralized by considering the effect of dry density in the calibration equation for the same kind of soil and rock. The empirical equations proposed by Zhao et al. show a good accuracy for rock-soil mixtures, indicating that the TDR method can be used to test gravimetric water content conveniently and efficiently without calibration in the field.

The Influence of Soil Particle on Soil Condensation Water

OpenAIRE

Hou Xinwei; Chen Hao; Li Xiangquan; Cui Xiaomei; Liu Lingxia; Wang Zhenxing

2013-01-01

The experiment results showed that the indoor experiment formed from the volume of soil hygroscopic water increased gradually with decreasing size of soil particles. In the outdoor experiments, the results showed that the formed condensation water in medium sand was greater than it was in fine sand; the soil hot condensation water was mainly formed in the top layer of soil between 0-5 cm. We also found that covering the soil surface with stones can increase the volume of formed soil condensat...

Improved or Unimproved Urban Areas Effect on Soil and Water Quality

Directory of Open Access Journals (Sweden)

Sally D. Logsdon

2017-04-01

Full Text Available Construction in urban areas usually results in compacted soil, which restricts plant growth and infiltration. Nutrients may be lost in storm runoff water and sediment. The purpose of this study was to determine if existing lawns benefit from aeration and surface compost additions without the negative impact of nutrient loss in runoff. Four sets of lawns were compared, with or without compost plus aeration, as a paired comparison. Surface bulk density was significantly reduced in the treated lawns (1.32 versus 1.42 Mg·m−3. Visual evaluation of soil structure showed improvement in the treated lawns. Of fifteen measurement dates over four years, four dates showed significantly higher surface soil water contents in the treated lawns compared with the untreated lawns. When compared over time, three of the four treated lawns had significantly higher soil water content than the untreated lawns. Nutrient concentrations in rainfall simulator runoff were not significantly different between treated and control lawns, which showed that compost did not negatively impact water quality. Compost and aeration helped restore soil quality for urban soils of recent construction.

[Development and succession of artificial biological soil crusts and water holding characteristics of topsoil].

Science.gov (United States)

Wu, Li; Chen, Xiao-Guo; Zhang, Gao-Ke; Lan, Shu-Bin; Zhang, De-Lu; Hu, Chun-Xiang

2014-03-01

In order to understand the improving effects of cyanobacterial inoculation on water retention of topsoil in desert regions, this work focused on the development and succession of biological soil crusts and water holding characteristics of topsoil after cyanobacterial inoculation in Qubqi Desert. The results showed that after the artificial inoculation of desert cyanobacteria, algal crusts were quickly formed, and in some microenvironments direct succession of the algal crusts to moss crusts occurred after 2-3 years. With the development and succession of biological soil crusts, the topsoil biomass, polysaccharides content, crust thickness and porosity increased, while the soil bulk density decreased. At the same time, with crust development and succession, the topsoil texture became finer and the percents of fine soil particles including silt and clay contents increased, while the percents of coarse soil particles (sand content) decreased proportionately. In addition, it was found that with crust development and succession, the water holding capacity and water content of topsoil showed an increasing trend, namely: moss crust > algal crusts > shifting sand. The water content (or water holding capacity) in algal and moss crusts were 1.1-1.3 and 1.8-2.2 times of those in shifting sand, respectively. Correlation analysis showed that the water holding capacity and water content of topsoil were positively correlated with the crust biomass, polysaccharides content, thickness, bulk density, silt and clay content; while negatively correlated with the porosity and sand content. Furthermore, stepwise regression analysis showed that the main factor affecting water content was the clay content, while that affecting water holding capacity was the porosity.

Neutron Gauge Calibration Curve as Affected by Chloride Concentration and Bulk Density of Loam Soil

International Nuclear Information System (INIS)

AL-Hasani, A.A.; Fahad, A.A.; Shihab, R.M.

2010-01-01

chloride concentration and bulk density are considered among important factors affecting calibration curve of neutron gauge in the soil.The aim of this study was to investigate the effect of chloride concentration and bulk density of a loam soil on neutron gauge calibration curve.Sufficient amount of loam soil was air dried screened through a 2 mm sieve,and divided into three equal portions.Sodium chloride of 2.5 and 6.6g kg'-1 soil was added to the first and second portions,respectively.The third portion was left as a control.The soil then moistened and mixed well to make volumetric water content within the range of 0.01 to 0.24 cm 3 cm - 3. The moist soil was packed into an iron drum 0.80 m diameter and 1.00 m height to obtain bulk densities of 1.10 and 1.30 to 1.60 Mg m - 3 for uncompacted soil,respectively.Access tube 0.05 m inner diameter was installed in the center of the drum.Three readings from CPN 503 neutron gauge were taken at each 0.15,0.30, 0.45,and 0.75 m depth.Results indicated that the count (counts/standard count) for an aqueous solution decreased with the increase in chloride concentration.Similarly, the slope of the linear calibration curves of the investigated soil decreased with the increase in chloride concentration.Shifting of the curves was 9 to 10%for the uncompacted soil, whereas it was 12 to 14 % for the compacted of low and high concentration of chloride, respectively . Results of changing bulk density always reduced the slope value as compared with the uncorrected count ratio.

Spatial correlation between weed species densities and soil properties

DEFF Research Database (Denmark)

Walter, Mette; Christensen, Svend; Simmelsgaard, Svend Erik

2002-01-01

The spatial cross-correlation between weed species densities and six soil properties within fields was analysed using cross-semivariograms. The survey was carried out in three successive years in two fields. The most consistent relationship between weed species density (numbers m−2) and soil...... properties was negative cross-correlation between the density of Viola arvensis Murray and clay content. This correlation was found in both fields; however, the range of spatial dependence varied between fields. In one of the fields, the density of Lamium purpureum L. was positively cross......-correlated with the phosphorus content in the soil in all years. The density of Veronica spp. and Poa annua L. was negatively cross-correlated with pH in all three years. Other spatial cross-correlations that were found in this study were inconsistent over time or field site. The densities of some of the weed species were...

The Relations Between Soil Water Retention Characteristics, Particle Size Distributions, Bulk Densities and Calcium Carbonate Contents for Danish Soils

DEFF Research Database (Denmark)

Jensen, Niels H.; Balstrøm, Thomas; Breuning-Madsen, Henrik

2005-01-01

functions developed in HYPRES (Hydraulic Properties of European Soils). Introducing bulk density as a predictor improved the equation for pressure head –1 kPa but not for lower ones. The grouping of data sets in surface and subsurface horizons or in textural classes did not improve the equations. Based...

Performance evaluation of TDT soil water content and watermark soil water potential sensors

Science.gov (United States)

This study evaluated the performance of digitized Time Domain Transmissometry (TDT) soil water content sensors (Acclima, Inc., Meridian, ID) and resistance-based soil water potential sensors (Watermark 200, Irrometer Company, Inc., Riverside, CA) in two soils. The evaluation was performed by compar...

Sustainable Soil Water Management Systems

OpenAIRE

Basch, G.; Kassam, A.; Friedrich, T.; Santos, F.L.; Gubiani, P.I.; Calegari, A.; Reichert, J.M.; dos Santos, D.R.

2012-01-01

Soil quality and its management must be considered as key elements for an effective management of water resources, given that the hydrological cycle and land management are intimately linked (Bossio et al. 2007). Soil degradation has been described by Bossio et al. (2010) as the starting point of a negative cycle of soil-water relationships, creating a positive, self-accelerating feedback loop with important negative impacts on water cycling and water productivity. Therefore, sustainable soil...

In-situ measurements of soil-water conductivity

International Nuclear Information System (INIS)

Murphy, C.E.

1978-01-01

Radionuclides and other environmentally important materials often move in association with water. In terrestrial ecosystems, the storage and movement of water in the soil is of prime importance to the hydrologic cycle of the ecosystem. The soil-water conductivity (the rate at which water moves through the soil) is a necessary input to models of soil-water movement. In situ techniques for measurement of soil-water conductivity have the advantage of averaging soil-water properties over larger areas than most laboratory methods. The in situ techniques also cause minimum disturbance of the soil under investigation. Results of measurements using a period of soil-water drainage after initial wetting indicate that soil-water conductivity and its variation with soil-water content can be determined with reasonable accuracy for the plot where the measurements were made. Further investigations are being carried out to look at variability between plots within a soil type

Biochar Improves Soil Aggregate Stability and Water Availability in a Mollisol after Three Years of Field Application

Science.gov (United States)

Zhang, Yulan; Yang, Lijie; Yu, Chunxiao; Yin, Guanghua; Doane, Timothy A.; Wu, Zhijie; Zhu, Ping; Ma, Xingzhu

2016-01-01

A field experiment was carried out to evaluate the effect of organic amendments on soil organic carbon, total nitrogen, bulk density, aggregate stability, field capacity and plant available water in a representative Chinese Mollisol. Four treatments were as follows: no fertilization (CK), application of inorganic fertilizer (NPK), combined application of inorganic fertilizer with maize straw (NPK+S) and addition of biochar with inorganic fertilizer (NPK+B). Our results showed that after three consecutive years of application, the values of soil bulk density were significantly lower in both organic amendment-treated plots than in unamended (CK and NPK) plots. Compared with NPK, NPK+B more effectively increased the contents of soil organic carbon, improved the relative proportion of soil macro-aggregates and mean weight diameter, and enhanced field capacity as well as plant available water. Organic amendments had no obvious effect on soil C/N ratio or wilting coefficient. The results of linear regression indicated that the improvement in soil water retention could be attributed to the increases in soil organic carbon and aggregate stability. PMID:27191160

Biochar Improves Soil Aggregate Stability and Water Availability in a Mollisol after Three Years of Field Application.

Science.gov (United States)

Ma, Ningning; Zhang, Lili; Zhang, Yulan; Yang, Lijie; Yu, Chunxiao; Yin, Guanghua; Doane, Timothy A; Wu, Zhijie; Zhu, Ping; Ma, Xingzhu

2016-01-01

A field experiment was carried out to evaluate the effect of organic amendments on soil organic carbon, total nitrogen, bulk density, aggregate stability, field capacity and plant available water in a representative Chinese Mollisol. Four treatments were as follows: no fertilization (CK), application of inorganic fertilizer (NPK), combined application of inorganic fertilizer with maize straw (NPK+S) and addition of biochar with inorganic fertilizer (NPK+B). Our results showed that after three consecutive years of application, the values of soil bulk density were significantly lower in both organic amendment-treated plots than in unamended (CK and NPK) plots. Compared with NPK, NPK+B more effectively increased the contents of soil organic carbon, improved the relative proportion of soil macro-aggregates and mean weight diameter, and enhanced field capacity as well as plant available water. Organic amendments had no obvious effect on soil C/N ratio or wilting coefficient. The results of linear regression indicated that the improvement in soil water retention could be attributed to the increases in soil organic carbon and aggregate stability.

Biochar Improves Soil Aggregate Stability and Water Availability in a Mollisol after Three Years of Field Application.

Directory of Open Access Journals (Sweden)

Ningning Ma

Full Text Available A field experiment was carried out to evaluate the effect of organic amendments on soil organic carbon, total nitrogen, bulk density, aggregate stability, field capacity and plant available water in a representative Chinese Mollisol. Four treatments were as follows: no fertilization (CK, application of inorganic fertilizer (NPK, combined application of inorganic fertilizer with maize straw (NPK+S and addition of biochar with inorganic fertilizer (NPK+B. Our results showed that after three consecutive years of application, the values of soil bulk density were significantly lower in both organic amendment-treated plots than in unamended (CK and NPK plots. Compared with NPK, NPK+B more effectively increased the contents of soil organic carbon, improved the relative proportion of soil macro-aggregates and mean weight diameter, and enhanced field capacity as well as plant available water. Organic amendments had no obvious effect on soil C/N ratio or wilting coefficient. The results of linear regression indicated that the improvement in soil water retention could be attributed to the increases in soil organic carbon and aggregate stability.

The soil water balance in a mosaic of clumped vegetation

Science.gov (United States)

Pizzolla, Teresa; Manfreda, Salvatore; Caylor, Kelly; Gioia, Andrea; Iacobellis, Vito

2014-05-01

The spatio-temporal distribution of soil moisture influences the plant growth and the distribution of terrestrial vegetation. This effect is more evident in arid and semiarid ecosystems where the interaction between individuals and the water limited conditions play a fundamental role, providing environmental conditions which drive a variety of non-linear ecohydrological response functions (such as transpiration, photosynthesis, leakage). In this context, modeling vegetation patterns at multiple spatial aggregation scales is important to understand how different vegetation structures can modify the soil water distribution and the exchanged fluxes between soil and atmosphere. In the present paper, the effect of different spatial vegetation patterns, under different climatic scenarios, is investigated in a patchy vegetation mosaic generated by a random process of individual tree canopies and their accompanying root system. Vegetation pattern are generated using the mathematical framework proposed by Caylor et al. (2006) characterized by a three dimensional stochastic vegetation structure, based on the density, dispersion, size distribution, and allometry of individuals within a landscape. A Poisson distribution is applied to generate different distribution of individuals paying particular attention on the role of clumping on water distribution dynamics. The soil water balance is evaluated using the analytical expression proposed by Laio et al. (2001) to explore the influence of climate and vegetation patterns on soil water balance steady-state components (such as the average rates of evaporation, the root water uptake and leakage) and on the stress-weighted plant water uptake. Results of numerical simulations show that clumping may be beneficial for water use efficiency at the landscape scale. References Caylor, Kelly K., P. D'Odorico and I. Rodriguez Iturbe: On the ecohydrology of structurally heterogeneous semiarid landscape. Water Resour. Res., 28, W07424, 2006

Measured and simulated soil water evaporation from four Great Plains soils

Science.gov (United States)

The amount of soil water lost during stage one and stage two soil water evaporation is of interest to crop water use modelers. The ratio of measured soil surface temperature (Ts) to air temperature (Ta) was tested as a signal for the transition in soil water evaporation from stage one to stage two d...

Measuring Soil Water Potential for Water Management in Agriculture: A Review

Directory of Open Access Journals (Sweden)

Marco Bittelli

2010-05-01

Full Text Available Soil water potential is a soil property affecting a large variety of bio-physical processes, such as seed germination, plant growth and plant nutrition. Gradients in soil water potential are the driving forces of water movement, affecting water infiltration, redistribution, percolation, evaporation and plants’ transpiration. The total soil water potential is given by the sum of gravity, matric, osmotic and hydrostatic potential. The quantification of the soil water potential is necessary for a variety of applications both in agricultural and horticultural systems such as optimization of irrigation volumes and fertilization. In recent decades, a large number of experimental methods have been developed to measure the soil water potential, and a large body of knowledge is now available on theory and applications. In this review, the main techniques used to measure the soil water potential are discussed. Subsequently, some examples are provided where the measurement of soil water potential is utilized for a sustainable use of water resources in agriculture.

A calculation method of available soil water content : application to viticultural terroirs mapping of the Loire valley

Directory of Open Access Journals (Sweden)

Etienne Goulet

2004-12-01

Full Text Available Vine water supply is one of the most important elements in the determination of grape composition and wine quality. Water supply conditions are in relation with available soil water content, therefore this one has to be determined when vineyard terroir mapping is undertaken. The available soil water content depends on soil factors like water content at field capacity, water content at the permanent wilting point, apparent density and rooting depth. The aim of this study is to seek the relationship between these factors and a simple soil characteristic such as texture which could be easily measurable in routine cartography. Study area is located in the Loire valley, in two different geological regions. First results indicate that it is possible to determine available soil water content from clay percentage, then from soil texture. These results also show that available soil water content algorithms differ with geological properties. This calculation can be used at each auger boring and results can be spatialised within a Geographical Information System that allows the production of available water content maps.

A Comparison of Soil-Water Sampling Techniques

Science.gov (United States)

Tindall, J. A.; Figueroa-Johnson, M.; Friedel, M. J.

2007-12-01

The representativeness of soil pore water extracted by suction lysimeters in ground-water monitoring studies is a problem that often confounds interpretation of measured data. Current soil water sampling techniques cannot identify the soil volume from which a pore water sample is extracted, neither macroscopic, microscopic, or preferential flowpath. This research was undertaken to compare values of extracted suction lysimeters samples from intact soil cores with samples obtained by the direct extraction methods to determine what portion of soil pore water is sampled by each method. Intact soil cores (30 centimeter (cm) diameter by 40 cm height) were extracted from two different sites - a sandy soil near Altamonte Springs, Florida and a clayey soil near Centralia in Boone County, Missouri. Isotopically labeled water (O18? - analyzed by mass spectrometry) and bromide concentrations (KBr- - measured using ion chromatography) from water samples taken by suction lysimeters was compared with samples obtained by direct extraction methods of centrifugation and azeotropic distillation. Water samples collected by direct extraction were about 0.25 ? more negative (depleted) than that collected by suction lysimeter values from a sandy soil and about 2-7 ? more negative from a well structured clayey soil. Results indicate that the majority of soil water in well-structured soil is strongly bound to soil grain surfaces and is not easily sampled by suction lysimeters. In cases where a sufficient volume of water has passed through the soil profile and displaced previous pore water, suction lysimeters will collect a representative sample of soil pore water from the sampled depth interval. It is suggested that for stable isotope studies monitoring precipitation and soil water, suction lysimeter should be installed at shallow depths (10 cm). Samples should also be coordinated with precipitation events. The data also indicate that each extraction method be use to sample a different

Biochar effects on wet and dry regions of the soil water retention curve of a sandy loam

DEFF Research Database (Denmark)

Arthur, Emmanuel; Moldrup, Per; Sun, Zhencai

2014-01-01

Reported beneficial effects of biochar on soil physical properties and processes include decreased soil density, and increased soil water transport, water holding capacity and retention (mainly for the wet region). Research is limited on biochar effects on the full soil water retention curve (wet...... and dry regions) for a given soil and biochar amendment scenarios. This study evaluates how biochar applied to a sandy loam field at rates from 0 to 50 Mg ha−1 yr–1 in 2011, 2012, or both years (2011+2012) influences the full water retention curve. Inorganic fertilizer and pig slurry were added to all...... treatments. Six months after the last biochar application, intact and disturbed soil samples were collected for analyses. Soil water retention was measured from −1 kPa to −100 kPa using tension tables and ceramic plates and from −10 MPa to −480 MPa using a Vapor Sorption Analyzer. Soil specific area...

Explaining Air and Water Transport in Undisturbed Soils By X-Ray CT Derived Macroporosity and CT- Number-Derived Matrix Density

DEFF Research Database (Denmark)

Paradelo Pérez, Marcos; Katuwal, Sheela; Møldrup, Per

The characterization of soil pore space geometry is important to predict the fluxes of air, water and solutes through soil and understand soil hydrogeochemical functions. X-ray computed tomography (CT) -derived parameters were evaluated as predictors of water, air and solute transport through soil....... Forty five soil columns (20-cm × 20-cm) were collected at an agricultural field in Estrup, Denmark. The soil columns were scanned in a medical CT-scanner. Subsequent to this, non-reactive tracer leaching experiments were performed in the laboratory together with measurements of air permeability (Ka...... is considered a robust indicator of preferential flow. Meanwhile, CT-derived limiting macro-porosity was the best predictor for Ka and log10Ksat. A best subsets regression analysis was performed combining macroporosity, limiting macroporosity and CTmatrix. The predictions of water and air flow improved using...

Density and permeability of a loess soil: long-term organic matter effect and the response to compressive stress

DEFF Research Database (Denmark)

Arthur, Emmanuel; Schjønning, Per; Møldrup, Per

2013-01-01

to compressive stress, undisturbed soil cores were collected from a long-term fertilisation experiment in Bad Lauchstädt in Germany, including combinations of animal manure and mineral fertilisers. The cores were drained to -100 hPa matric potential and exposed to uniaxial confined compression (200k......Pa). Investigated indicators for compression resistance included compression index, precompression stress, and resistance and resilience indices based on measured soil physical properties (bulk density, air-filled porosity, air permeability, and void ratio). Soil resilience was assessed following exposure...... but the correlation was not significant. However, initial bulk density (ρbi) and initial gravimetric water content (wi) were significantly positively correlated to the indices of soil compression resistance, with the effect of ρbi being significantly stronger. Significant recovery of airfilled porosity and air...

[Soil seed bank and its correlations with aboveground vegetation and environmental factors in water level fluctuating zone of Danjiangkou Reservoir, Central China].

Science.gov (United States)

Liu, Rui-Xue; Zhan, Juan; Shi, Zhi-Hua; Chen, Long-qing

2013-03-01

Taking the water level fluctuating zone of the Danjiangkou Reservoir as a case, and by the method of hierarchical cluster analysis, the soil seed banks at 37 sampling plots within the areas of 140-145 m elevation were divided into 6 groups, and the species composition, density, and diversity of the soil seed banks among the groups were compared. The differences between the soil seed banks and the aboveground vegetations were analyzed by S0rensen similarity coefficient, and the correlations among the soil seed banks, aboveground vegetations, and environmental factors were explored by principal component analysis (PCA) and multivariable regression analysis. At the same altitudes of the water level fluctuating zone, the species composition of the soil seed banks had obvious heterogeneity, and the density and diversity indices of the soil seed banks among different groups were great. The similarity coefficient between the soil seed banks and aboveground vegetations was low, and the species number in the soil seed banks was obviously lesser than that in the aboveground vegetations. The density of the soil seed banks was highly positively correlated with the aboveground vegetations coverage and species number and the soil texture, but highly negatively correlated with the soil water-holding capacity and soil porosity.

The impact of land use on water loss and soil desiccation in the soil profile

Science.gov (United States)

Zhang, Jing; Wang, Li

2018-02-01

Farmlands have gradually been replaced by apple orchards in Shaanxi province, China, and there will be a risk of severe soil-water-storage deficit with the increasing age of the apple trees. To provide a theoretical basis for the sustainable development of agriculture and forestry in the Loess Plateau, soil water content in a 19-year-old apple orchard, a 9-year-old apple orchard, a cornfield and a wheat field in the Changwu Tableland was investigated at different depths from January to October 2014. The results showed that: (1) the soil moisture content is different across the soil profile—for the four plots, the soil moisture of the cornfield is the highest, followed by the 9-year-old apple orchard and the wheat field, and the 19-year-old apple orchard has the lowest soil moisture. (2) There are varying degrees of soil desiccation in the four plots: the most serious degree of desiccation is in the 19-year-old apple orchard, followed by the wheat field and the cornfield, with the least severe desiccation occurring in the 9-year-old apple orchard. Farmland should replace apple orchards for an indefinite period while there is an extremely desiccated soil layer in the apple orchard so as to achieve the purpose of sustainable development. It will be necessary to reduce tree densities, and to carry out other research, if development of the economy and ecology of Changwu is to be sustainable.

Characterization of soil water content variability and soil texture using GPR groundwave techniques

Energy Technology Data Exchange (ETDEWEB)

Grote, K.; Anger, C.; Kelly, B.; Hubbard, S.; Rubin, Y.

2010-08-15

Accurate characterization of near-surface soil water content is vital for guiding agricultural management decisions and for reducing the potential negative environmental impacts of agriculture. Characterizing the near-surface soil water content can be difficult, as this parameter is often both spatially and temporally variable, and obtaining sufficient measurements to describe the heterogeneity can be prohibitively expensive. Understanding the spatial correlation of near-surface soil water content can help optimize data acquisition and improve understanding of the processes controlling soil water content at the field scale. In this study, ground penetrating radar (GPR) methods were used to characterize the spatial correlation of water content in a three acre field as a function of sampling depth, season, vegetation, and soil texture. GPR data were acquired with 450 MHz and 900 MHz antennas, and measurements of the GPR groundwave were used to estimate soil water content at four different times. Additional water content estimates were obtained using time domain reflectometry measurements, and soil texture measurements were also acquired. Variograms were calculated for each set of measurements, and comparison of these variograms showed that the horizontal spatial correlation was greater for deeper water content measurements than for shallower measurements. Precipitation and irrigation were both shown to increase the spatial variability of water content, while shallowly-rooted vegetation decreased the variability. Comparison of the variograms of water content and soil texture showed that soil texture generally had greater small-scale spatial correlation than water content, and that the variability of water content in deeper soil layers was more closely correlated to soil texture than were shallower water content measurements. Lastly, cross-variograms of soil texture and water content were calculated, and co-kriging of water content estimates and soil texture

Pedotransfer functions to estimate water retention parameters of soils in northeastern Brazil

Directory of Open Access Journals (Sweden)

Alexandre Hugo Cezar Barros

2013-04-01

Full Text Available Pedotransfer functions (PTF were developed to estimate the parameters (α, n, θr and θs of the van Genuchten model (1980 to describe soil water retention curves. The data came from various sources, mainly from studies conducted by universities in Northeast Brazil, by the Brazilian Agricultural Research Corporation (Embrapa and by a corporation for the development of the São Francisco and Parnaíba river basins (Codevasf, totaling 786 retention curves, which were divided into two data sets: 85 % for the development of PTFs, and 15 % for testing and validation, considered independent data. Aside from the development of general PTFs for all soils together, specific PTFs were developed for the soil classes Ultisols, Oxisols, Entisols, and Alfisols by multiple regression techniques, using a stepwise procedure (forward and backward to select the best predictors. Two types of PTFs were developed: the first included all predictors (soil density, proportions of sand, silt, clay, and organic matter, and the second only the proportions of sand, silt and clay. The evaluation of adequacy of the PTFs was based on the correlation coefficient (R and Willmott index (d. To evaluate the PTF for the moisture content at specific pressure heads, we used the root mean square error (RMSE. The PTF-predicted retention curve is relatively poor, except for the residual water content. The inclusion of organic matter as a PTF predictor improved the prediction of parameter a of van Genuchten. The performance of soil-class-specific PTFs was not better than of the general PTF. Except for the water content of saturated soil estimated by particle size distribution, the tested models for water content prediction at specific pressure heads proved satisfactory. Predictions of water content at pressure heads more negative than -0.6 m, using a PTF considering particle size distribution, are only slightly lower than those obtained by PTFs including bulk density and organic matter

Linking Soil Physical Parameters Along a Density Gradient in a Loess-Soil Long-Term Experiment

DEFF Research Database (Denmark)

Eden, Marie; Møldrup, Per; Schjønning, Per

2012-01-01

It is important to understand the impact of texture and organic carbon (OC) on soil structure development. Only few studies investigated this for silt-dominated soils. In this study, soil physical properties were determined on samples from a controlled experiment (Static Fertilization Experiment...... hydraulic conductivity. The management resulted in a distinct gradient in OC. A bulk density gradient developed from differences in amount of clay not complexed with OC. This gradient in bulk density mainly affected content of pores larger than 3 [mu]m. The air-connected porosity measured by a pycnometer...

Soil Water: Advanced Crop and Soil Science. A Course of Study.

Science.gov (United States)

Miller, Larry E.

The course of study represents the fourth of six modules in advanced crop and soil science and introduces the agriculture student to the topic of soil water. Upon completing the three day module, the student will be able to classify water as to its presence in the soil, outline the hydrological cycle, list the ways water is lost from the soil,…

Spatial changes in soil organic carbon density and storage of cultivated soils in China from 1980 to 2000

Science.gov (United States)

Yu, Yanyan; Guo, Zhengtang; Wu, Haibin; Kahmann, Julia A.; Oldfield, Frank

2009-06-01

We address the spatial changes in organic carbon density and storage in cultivated soils in China from 1980 to 2000 on the basis of measured data from individual studies and those acquired during the second national soil survey in China. The results show a carbon gain in ˜66% of the cultivated area of China as a whole with the increase in soil organic carbon (SOC) density mostly ranging from 10% to 30%. Soil organic carbon density increased in fluvi-aquic soils (fluvisols, Food and Agriculture Organization (FAO) of the United Nations) in north China, irrigated silting soils (calcaric fluvisols) in northwest China, latosolic red earths (haplic acrisols/alisols), and paddy soils (fluvisols/cambisols) in south China. In contrast, significant decreases are observed in black soils (phaeozems) in northeast China and latosols (haplic acrisols) in southwest China. No significant changes are detected in loessial soils (calcaric regosols) and dark loessial soils (calcisols) in the loess plateau region. The total SOC storage and average density in the upper 20 cm in the late 1990s are estimated to be ˜5.37 Pg C and 2.77 kg/m2, respectively, compared with the values of ˜5.11 Pg C and 2.63 kg/m2 in the early 1980s. This reveals an increase of SOC storage of 0.26 Pg C and suggests an overall carbon sink for cultivated soils in China, which has contributed 2-3% to the global terrestrial ecosystem carbon absorption from 1980 to 2000. Statistical analyses suggest an insignificant contribution to the observed SOC increase from climate change, and we infer that it is mostly attributable to improved agricultural practices. Despite the SOC density increases over 20 years, the SOC density of the cultivated soils in China in the late 1990s is still ˜30% lower compared to their uncultivated counterparts in comparable soil types, suggesting a considerable potential for SOC restoration through improving management practices. Assuming a restoration of ˜50% of the lost SOC in the next 30

Does earthworms density really modify soil's hydrodynamic ...

African Journals Online (AJOL)

Our study has the general objective to understand the impact of the valuation of treated water on earthworm abundance and total porosity of the soil and the effect of the interaction between these two physical-biological components of the hydrological functioning of soils. It was carried out on the meadows soils of the valley ...

Soil-Water Repellency Characteristic Curves for Soil Profiles with Organic Carbon Gradients

DEFF Research Database (Denmark)

Wijewardana, Nadeeka Senani; Muller, Karin; Moldrup, Per

2016-01-01

Soil water repellency (SWR) of soils is a property with significant consequences for agricultural water management, water infiltration, contaminant transport, and for soil erosion. It is caused by the presence of hydrophobic agents on mineral grain surfaces. Soils were samples in different depths......, and the sessile drop method (SDM). The aim to (i) compare the methods, (ii) characterize the soil-water repellency characteristic curves (SWRCC) being SWR as a function of the volumetric soil-water content (θ) or matric potential (ψ), and (iii) find relationships between SWRCC parameters and SOC content. The WDPT...... at three forest sites in Japan and three pasture sites in New Zealand, covering soil organic carbon (SOC) contents between 1 and 26%. The SWR was measured over a range of water contents by three common methods; the water drop penetration time (WDPT) test, the molarity of an ethanol droplet (MED) method...

Abundance of plankton population densities in relation to bottom soil textural types in aquaculture ponds

Directory of Open Access Journals (Sweden)

F. Siddika

2012-06-01

Full Text Available Plankton is an important food item of fishes and indicator for the productivity of a water body. The present study was conducted to evaluate the effects of bottom soil textural conditions on abundance of plankton in aquaculture pond. The experiment was carried out using three treatments, i.e., ponds bottom with sandy loam (T1, with loam (T2 and with clay loam (T3. The ranges of water quality parameters analyzed were suitable for the growth of plankton during the experimental period. Similarly, chemical properties of soil were also within suitable ranges and every parameter showed higher ranges in T2. A total 20 genera of phytoplankton were recorded belonged to Chlorophyceae (7, Cyanophyceae (5, Bacillariophyceae (5, Euglenophyceae (2 and Dinophyceae (1. On the other hand, total 13 genera of zooplankton were recorded belonged to Crustacea (7 and Rotifera (6. The highest ranges of phytoplankton and zooplankton densities were found in T2 where low to medium-type bloom was observed during the study period. Consequently, the mean abundance of plankton (phytoplankton and zooplankton density was significantly highest in T2. The highest abundance of plankton in the T2 indicated that pond bottom with loamy soil is suitable for the growth and production of plankton in aquaculture ponds.

Estimating Soil Bulk Density and Total Nitrogen from Catchment ...

African Journals Online (AJOL)

Even though data on soil bulk density (BD) and total nitrogen (TN) are essential for planning modern farming techniques, their data availability is limited for many applications in the developing word. This study is designed to estimate BD and TN from soil properties, land-use systems, soil types and landforms in the ...

Sediment predictions in Wadi Al-Naft using soil water assessment tool

Directory of Open Access Journals (Sweden)

Alwan Imzahim Abdulkareem

2018-01-01

Full Text Available Sediment production is the amount of sediment in the unit area that is transported through the basin by water transfer over a specified period of time. The main aim of present study is to predict sediment yield of Wadi, Al-Naft watershed with 8820 Km2area, that is located in the North-East of Diyala Governorate in Iraq, using Soil-Water Assessment Tool, (SWAT and to predict the impact of land management and the input data including the land use, soil type, and soil texture maps which are obtained from Landsat-8 satellite image. Digital Elevation Model,(DEM with resolution (14 14 meter is used to delineate the watershed with the aid of model. Three Land-sat images were used to cover the study area which were mosaic processed and the study area masked- up from the mosaic, image. The area of study has been registries by Arc-GIS 10.2 and digitized the soil hydrologic group through assistant of Soil Plant Assistant Water Model, (SPAW which was progressed by USDA, Agricultural, Research Service, using the data of soil textural and organic matter from Food and Agriculture Organization (FAO, the available water content, saturated hydraulic conductivity, and bulk density. The results of average, sediment depth and the maximum upland sediment for simulation period (2010-2020 were predicted to be (1.7 mm, and (12.57 Mg/ha, respectively.

Salinity controls on plant transpiration and soil water balance

Science.gov (United States)

Perri, S.; Molini, A.; Suweis, S. S.; Viola, F.; Entekhabi, D.

2017-12-01

Soil salinization and aridification represent a major threat for the food security and sustainable development of drylands. The two problems are deeply connected, and their interplay is expected to be further enhanced by climate change and projected population growth. Salt-affected land is currently estimated to cover around 1.1 Gha, and is particularly widespread in semi-arid to hyper-arid climates. Over 900 Mha of these saline/sodic soils are potentially available for crop or biomass production. Salt-tolerant plants have been recently proposed as valid solution to exploit or even remediate salinized soils. However the effects of salinity on evapotranspiration, soil water balance and the long-term salt mass balance in the soil, are still largely unexplored. In this contribution we analyze the feedback of evapotranspiration on soil salinization, with particular emphasis on the role of vegetation and plant salt-tolerance. The goal is to introduce a simple modeling framework able to shed some light on how (a) soil salinity controls plant transpiration, and (b) salinization itself is favored/impeded by different vegetation feedback. We introduce at this goal a spatially lumped stochastic model of soil moisture and salt mass dynamics averaged over the active soil depth, and accounting for the effect of salinity on evapotranspiration. Here, the limiting effect of salinity on ET is modeled through a simple plant response function depending on both salt concentration in the soil and plant salt-tolerance. The coupled soil moisture and salt mass balance is hence used to obtain the conditional steady-state probability density function (pdf) of soil moisture for given salt tolerance and salinization level, Our results show that salinity imposes a limit in the soil water balance and this limit depends on plant salt-tolerance mainly through the control of the leaching occurrence (tolerant plants exploit water more efficiently than the sensitive ones). We also analyzed the

Tree density and permafrost thaw depth influence water limitations on stomatal conductance in Siberian Arctic boreal forests

Science.gov (United States)

Kropp, H.; Loranty, M. M.; Natali, S.; Kholodov, A. L.; Alexander, H. D.; Zimov, N.

2017-12-01

Boreal forests may experience increased water stress under global climate change as rising air temperatures increase evaporative demand and decrease soil moisture. Increases in plant water stress can decrease stomatal conductance, and ultimately, decrease primary productivity. A large portion of boreal forests are located in Siberia, and are dominated by deciduous needleleaf trees, Larix spp. We investigated the variability and drivers of canopy stomatal conductance in upland Larix stands with different stand density that arose from differing fire severity. Our measurements focus on an open canopy stand with low tree density and deep permafrost thaw depth, and a closed canopy stand with high tree density and shallow permafrost thaw depth. We measured canopy stomatal conductance, soil moisture, and micrometeorological variables. Our results demonstrate that canopy stomatal conductance was significantly lower in the closed canopy stand with a significantly higher sensitivity to increases in atmospheric evaporative demand. Canopy stomatal conductance in both stands was tightly coupled to precipitation that occurred over the previous week; however, the closed canopy stand showed a significantly greater sensitivity to increases in precipitation compared to the open canopy stand. Differences in access to deep versus shallow soil moisture and the physical characteristics of the soil profile likely contribute to differences in sensitivity to precipitation between the two stands. Our results indicate that Larix primary productivity may be highly sensitive to changes in evaporative demand and soil moisture that can result of global climate change. However, the effect of increasing air temperatures and changes in precipitation will differ significantly depending on stand density, thaw depth, and the hydraulic characteristics of the soil profile.

Importance of soil-water relation in assessment endpoint in bioremediated soils: Plant growth and soil physical properties

International Nuclear Information System (INIS)

Li, X.; Sawatsky, N.

1995-01-01

Much effort has been focused on defining the end-point of bioremediated soils by chemical analysis (Alberta Tier 1 or CCME Guideline for Contaminated Soils) or toxicity tests. However, these tests do not completely assess the soil quality, or the capability of soil to support plant growth after bioremediation. This study compared barley (Hordeum vulgare) growth on: (i) non-contaminated, agricultural topsoil, (2) oil-contaminated soil (4% total extractable hydrocarbons, or TEH), and (3) oil-contaminated soil treated by bioremediation (< 2% TEH). Soil physical properties including water retention, water uptake, and water repellence were measured. The results indicated that the growth of barley was significantly reduced by oil-contamination of agricultural topsoil. Furthermore, bioremediation did not improve the barley yield. The lack of effects from bioremediation was attributed to development of water repellence in hydrocarbon contaminated soils. There seemed to be a critical water content around 18% to 20% in contaminated soils. Above this value the water uptake by contaminated soil was near that of the agricultural topsoil. For lower water contents, there was a strong divergence in sorptivity between contaminated and agricultural topsoil. For these soils, water availability was likely the single most important parameter controlling plant growth. This parameter should be considered in assessing endpoint of bioremediation for hydrocarbon contaminated soils

Isotopic fractionation of soil water during evaporation

Energy Technology Data Exchange (ETDEWEB)

Leopoldo, P R [Faculdade de Ciencias Medicas e Biologicas de Botucatu (Brazil); Salati, E; Matsui, E [Centro de Energia Nuclear na Agricultura, Piracicaba (Brazil)

1974-07-01

The study of the variation of D/H relation in soil water during evaporation is studied. The isotopic fractionation of soil water has been observed in two soils of light and heavy texture. Soil columns were utilized. Soil water was extracted in a system operated under low pressure and the gaseous hydrogen was obtained by decomposition of the water and was analyzed in a GD-150 mass spectrometer for deuterium content. The variation of the delta sub(eta) /sup 0///sub 00/ value during evaporation showed that for water held at potentials below 15 atm, the deuterium content of soil water stays practically constant. For water held at potentials higher than 15 atm, corresponding to the third stage of evaporation, there is a strong tendency of a constant increase of delta sub(eta) /sup 0///sub 00/ of the remaining water.

Modelling soil water dynamics and crop water uptake at the field level

NARCIS (Netherlands)

Kabat, P.; Feddes, R.A.

1995-01-01

Parametrization approaches to model soil water dynamics and crop water uptake at field level were analysed. Averaging and numerical difficulties in applying numerical soil water flow models to heterogeneous soils are highlighted. Simplified parametrization approaches to the soil water flow, such as

Soil Water Retention Curve

Science.gov (United States)

Johnson, L. E.; Kim, J.; Cifelli, R.; Chandra, C. V.

2016-12-01

Potential water retention, S, is one of parameters commonly used in hydrologic modeling for soil moisture accounting. Physically, S indicates total amount of water which can be stored in soil and is expressed in units of depth. S can be represented as a change of soil moisture content and in this context is commonly used to estimate direct runoff, especially in the Soil Conservation Service (SCS) curve number (CN) method. Generally, the lumped and the distributed hydrologic models can easily use the SCS-CN method to estimate direct runoff. Changes in potential water retention have been used in previous SCS-CN studies; however, these studies have focused on long-term hydrologic simulations where S is allowed to vary at the daily time scale. While useful for hydrologic events that span multiple days, the resolution is too coarse for short-term applications such as flash flood events where S may not recover its full potential. In this study, a new method for estimating a time-variable potential water retention at hourly time-scales is presented. The methodology is applied for the Napa River basin, California. The streamflow gage at St Helena, located in the upper reaches of the basin, is used as the control gage site to evaluate the model performance as it is has minimal influences by reservoirs and diversions. Rainfall events from 2011 to 2012 are used for estimating the event-based SCS CN to transfer to S. As a result, we have derived the potential water retention curve and it is classified into three sections depending on the relative change in S. The first is a negative slope section arising from the difference in the rate of moving water through the soil column, the second is a zero change section representing the initial recovery the potential water retention, and the third is a positive change section representing the full recovery of the potential water retention. Also, we found that the soil water moving has traffic jam within 24 hours after finished first

Influence of shrub cover vegetal and slope length on soil bulk density

International Nuclear Information System (INIS)

Bienes, R.; Jimenez, R.; Ruiz, M.; Garcia-Estringana, P.; Marques, M. J.

2009-01-01

In arid and semiarid environments of the Mediterranean climate, the shrub species play an important role in the revegetation of abandoned lands, which enables to control the soil losses, organic material and water. In this article are compared the results obtained under different revegetation in abandoned lands in the central area of Spain. In these revegetation has been used two native shrubs: A triplex halimus (Ah) and Retama sphaerocarpa (Rs), and were analyzed the influence of these revegetation in the contents of organic material of soil and apparent density in 5 years time after planting. As control, have been considered the pieces of ground with spontaneous vegetation abandoned in the same date that the shrubs revegetation. Atriplex halimus gives to the soil a covering capable to intercept a big amount of water drops absorbing a great amount part of the kinetic energy of the rain, while provides a microclimates as a result of be able to soften the wind, the temperature and the evaporation-transpiration, which makes it efficient to control the erosion and the desertification (Le Houerou, 2000). Retama sphaerocarpa was chosen because it is a native shrub very characteristic, and, due to its symbiosis with the Bradyrhizobium, enriches the soil in nitrogen, which is taken by the nitrophilous species enhancing the spontaneous vegetal covering. (Author) 9 refs.

Field-scale evaluation of water fluxes and manure solution leaching in feedlot pen soils.

Science.gov (United States)

García, Ana R; Maisonnave, Roberto; Massobrio, Marcelo J; Fabrizio de Iorio, Alicia R

2012-01-01

Accumulation of beef cattle manure on feedlot pen surfaces generates large amounts of dissolved solutes that can be mobilized by water fluxes, affecting surface and groundwater quality. Our objective was to examine the long-term impacts of a beef cattle feeding operation on water fluxes and manure leaching in feedlot pens located on sandy loam soils of the subhumid Sandy Pampa region in Argentina. Bulk density, gravimetric moisture content, and chloride concentration were quantified. Rain simulation trials were performed to estimate infiltration and runoff rates. Using chloride ion as a tracer, profile analysis techniques were applied to estimate the soil moisture flux and manure conservative chemical components leaching rates. An organic stratum was found over the surface of the pen soil, separated from the underlying soil by a highly compacted thin layer (the manure-soil interface). The soil beneath the organic layer showed greater bulk density in the A horizon than in the control soil and had greater moisture content. Greater concentrations of chloride were found as a consequence of the partial sealing of the manure-soil interface. Surface runoff was the dominant process in the feedlot pen soil, whereas infiltration was the main process in control soil. Soil moisture flux beneath pens decreased substantially after 15 yr of activity. The estimated minimum leaching rate of chloride was 13 times faster than the estimated soil moisture flux. This difference suggests that chloride ions are not exclusively transported by advective flow under our conditions but also by solute diffusion and preferential flow. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Assessment of soil sample quality used for density evaluations through computed tomography

International Nuclear Information System (INIS)

Pires, Luiz F.; Arthur, Robson C.J.; Bacchi, Osny O.S.

2005-01-01

There are several methods to measure soil bulk density (ρ s ) like the paraffin sealed clod (PS), the volumetric ring (VR), the computed tomography (CT), and the neutron-gamma surface gauge (SG). In order to evaluate by a non-destructive way the possible modifications in soil structure caused by sampling for the PS and VR methods of ρ s evaluation we proposed to use the gamma ray CT method. A first generation tomograph was used having a 241 Am source and a 3 in x 3 in NaI(Tl) scintillation crystal detector coupled to a photomultiplier tube. Results confirm the effect of soil sampler devices on the structure of soil samples, and that the compaction caused during sampling causes significant alterations of soil bulk density. Through the use of CT it was possible to determine the level of compaction and to make a detailed analysis of the soil bulk density distribution within the soil sample. (author)

Differential growth responses to water balance of coexisting deciduous tree species are linked to wood density in a Bolivian tropical dry forest.

Science.gov (United States)

Mendivelso, Hooz A; Camarero, J Julio; Royo Obregón, Oriol; Gutiérrez, Emilia; Toledo, Marisol

2013-01-01

A seasonal period of water deficit characterizes tropical dry forests (TDFs). There, sympatric tree species exhibit a diversity of growth rates, functional traits, and responses to drought, suggesting that each species may possess different strategies to grow under different conditions of water availability. The evaluation of the long-term growth responses to changes in the soil water balance should provide an understanding of how and when coexisting tree species respond to water deficit in TDFs. Furthermore, such differential growth responses may be linked to functional traits related to water storage and conductance. We used dendrochronology and climate data to retrospectively assess how the radial growth of seven coexisting deciduous tree species responded to the seasonal soil water balance in a Bolivian TDF. Linear mixed-effects models were used to quantify the relationships between basal area increment and seasonal water balance. We related these relationships with wood density and sapwood production to assess if they affect the growth responses to climate. The growth of all species responded positively to water balance during the wet season, but such responses differed among species as a function of their wood density. For instance, species with a strong growth response to water availability averaged a low wood density which may facilitate the storage of water in the stem. By contrast, species with very dense wood were those whose growth was less sensitive to water availability. Coexisting tree species thus show differential growth responses to changes in soil water balance during the wet season. Our findings also provide a link between wood density, a trait related to the ability of trees to store water in the stem, and wood formation in response to water availability.

Multiscale Bayesian neural networks for soil water content estimation

Science.gov (United States)

Jana, Raghavendra B.; Mohanty, Binayak P.; Springer, Everett P.

2008-08-01

Artificial neural networks (ANN) have been used for some time now to estimate soil hydraulic parameters from other available or more easily measurable soil properties. However, most such uses of ANNs as pedotransfer functions (PTFs) have been at matching spatial scales (1:1) of inputs and outputs. This approach assumes that the outputs are only required at the same scale as the input data. Unfortunately, this is rarely true. Different hydrologic, hydroclimatic, and contaminant transport models require soil hydraulic parameter data at different spatial scales, depending upon their grid sizes. While conventional (deterministic) ANNs have been traditionally used in these studies, the use of Bayesian training of ANNs is a more recent development. In this paper, we develop a Bayesian framework to derive soil water retention function including its uncertainty at the point or local scale using PTFs trained with coarser-scale Soil Survey Geographic (SSURGO)-based soil data. The approach includes an ANN trained with Bayesian techniques as a PTF tool with training and validation data collected across spatial extents (scales) in two different regions in the United States. The two study areas include the Las Cruces Trench site in the Rio Grande basin of New Mexico, and the Southern Great Plains 1997 (SGP97) hydrology experimental region in Oklahoma. Each region-specific Bayesian ANN is trained using soil texture and bulk density data from the SSURGO database (scale 1:24,000), and predictions of the soil water contents at different pressure heads with point scale data (1:1) inputs are made. The resulting outputs are corrected for bias using both linear and nonlinear correction techniques. The results show good agreement between the soil water content values measured at the point scale and those predicted by the Bayesian ANN-based PTFs for both the study sites. Overall, Bayesian ANNs coupled with nonlinear bias correction are found to be very suitable tools for deriving soil

Stochastic estimation of plant-available soil water under fluctuating water table depths

Science.gov (United States)

Or, Dani; Groeneveld, David P.

1994-12-01

Preservation of native valley-floor phreatophytes while pumping groundwater for export from Owens Valley, California, requires reliable predictions of plant water use. These predictions are compared with stored soil water within well field regions and serve as a basis for managing groundwater resources. Soil water measurement errors, variable recharge, unpredictable climatic conditions affecting plant water use, and modeling errors make soil water predictions uncertain and error-prone. We developed and tested a scheme based on soil water balance coupled with implementation of Kalman filtering (KF) for (1) providing physically based soil water storage predictions with prediction errors projected from the statistics of the various inputs, and (2) reducing the overall uncertainty in both estimates and predictions. The proposed KF-based scheme was tested using experimental data collected at a location on the Owens Valley floor where the water table was artificially lowered by groundwater pumping and later allowed to recover. Vegetation composition and per cent cover, climatic data, and soil water information were collected and used for developing a soil water balance. Predictions and updates of soil water storage under different types of vegetation were obtained for a period of 5 years. The main results show that: (1) the proposed predictive model provides reliable and resilient soil water estimates under a wide range of external conditions; (2) the predicted soil water storage and the error bounds provided by the model offer a realistic and rational basis for decisions such as when to curtail well field operation to ensure plant survival. The predictive model offers a practical means for accommodating simple aspects of spatial variability by considering the additional source of uncertainty as part of modeling or measurement uncertainty.

Space-based passive microwave soil moisture retrievals and the correction for a dynamic open water fraction

Directory of Open Access Journals (Sweden)

B. T. Gouweleeuw

2012-06-01

Full Text Available The large observation footprint of low-frequency satellite microwave emissions complicates the interpretation of near-surface soil moisture retrievals. While the effect of sub-footprint lateral heterogeneity is relatively limited under unsaturated conditions, open water bodies (if not accounted for cause a strong positive bias in the satellite-derived soil moisture retrieval. This bias is generally assumed static and associated with large, continental lakes and coastal areas. Temporal changes in the extent of smaller water bodies as small as a few percent of the sensor footprint size, however, can cause significant and dynamic biases. We analysed the influence of such small open water bodies on near-surface soil moisture products derived from actual (non-synthetic data from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E for three areas in Oklahoma, USA. Differences between on-ground observations, model estimates and AMSR-E retrievals were related to dynamic estimates of open water fraction, one retrieved from a global daily record based on higher frequency AMSR-E data, a second derived from the Moderate Resolution Imaging Spectroradiometer (MODIS and a third through inversion of the radiative transfer model, used to retrieve soil moisture. The comparison demonstrates the presence of relatively small areas (<0.05 of open water in or near the sensor footprint, possibly in combination with increased, below-critical vegetation density conditions (optical density <0.8, which contribute to seasonally varying biases in excess of 0.2 (m³ m⁻³ soil water content. These errors need to be addressed, either through elimination or accurate characterisation, if the soil moisture retrievals are to be used effectively in a data assimilation scheme.

Soil warming increased whole-tree water use of Pinus cembra at the treeline in the Central Tyrolean Alps.

Science.gov (United States)

Wieser, Gerhard; Grams, Thorsten E E; Matyssek, Rainer; Oberhuber, Walter; Gruber, Andreas

2015-03-01

This study quantified the effect of soil warming on sap flow density (Qs) of Pinus cembra L. at the treeline in the Central Tyrolean Alps. To enhance soil temperature we installed a transparent roof construction above the forest floor around six trees. Six other trees served as controls in the absence of any manipulation. Roofing enhanced growing season mean soil temperature by 1.6, 1.3 and 1.0 °C at 5, 10 and 20 cm soil depth, respectively, while soil water availability was not affected. Sap flow density (using Granier-type thermal dissipation probes) and environmental parameters were monitored throughout three growing seasons. During the first year of treatment, no warming effect was detected on Qs. However, soil warming caused Qs to increase significantly by 11 and 19% above levels in control trees during the second and third year, respectively. This effect appeared to result from warming-induced root production, a reduction in viscosity and perhaps an increase also in root hydraulic conductivity. Hardly affected were leaf-level net CO2 uptake rate and conductance for water vapour, so that water-use efficiency stayed unchanged as confirmed by needle δ(13)C analysis. We conclude that tree water loss will increase with soil warming, which may alter the water balance within the treeline ecotone of the Central Austrian Alps in a future warming environment. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Contact resistance problems applying ERT on low bulk density forested stony soils. Is there a solution?

Science.gov (United States)

Deraedt, Deborah; Touzé, Camille; Robert, Tanguy; Colinet, Gilles; Degré, Aurore; Garré, Sarah

2015-04-01

Electrical resistivity tomography (ERT) has often been put forward as a promising tool to quantify soil water and solute fluxes in a non-invasive way. In our experiment, we wanted to determine preferential flow processes along a forested hillslope using a saline tracer with ERT. The experiment was conducted in the Houille watershed, subcatchment of the Meuse located in the North of Belgian Ardennes (50° 1'52.6'N, 4° 53'22.5'E). The climate is continental but the soil under spruce (Picea abies (L.) Karst.) and Douglas fire stand (Pseudotsuga menziesii (Mirb.) Franco) remains quite dry (19% WVC in average) during the whole year. The soil is Cambisol and the parent rock is Devonian schist covered with variable thickness of silty loam soil. The soil density ranges from 1.13 to 1.87 g/cm3 on average. The stone content varies from 20 to 89% and the soil depth fluctuates between 70 and 130 cm. The ERT tests took place on June 1st 2012, April 1st, 2nd and 3rd 2014 and May 12th 2014. We used the Terrameter LS 12 channels (ABEM, Sweden) in 2012 test and the DAS-1 (Multi-Phase Technologies, United States) in 2014. Different electrode configurations and arrays were adopted for different dates (transect and grid arrays and Wenner - Schlumberger, Wenner alpha and dipole-dipole configurations). During all tests, we systematically faced technical problems, mainly related to bad electrode contact. The recorded data show values of contact resistance above 14873 Ω (our target value would be below 3000 Ω). Subsequently, we tried to improve the contact by predrilling the soil and pouring water in the electrode holes. The contact resistance improved to 14040 Ω as minimum. The same procedure with liquid mud was then tested to prevent quick percolation of the water from the electrode location. As a result, the lower contact resistance dropped to 11745 Ω. Finally, we applied about 25 litre of saline solution (CaCl2, 0.75g/L) homogeneously on the electrode grid. The minimum value of

Estimating soil water-holding capacities by linking the Food and Agriculture Organization Soil map of the world with global pedon databases and continuous pedotransfer functions

Science.gov (United States)

Reynolds, C. A.; Jackson, T. J.; Rawls, W. J.

2000-12-01

Spatial soil water-holding capacities were estimated for the Food and Agriculture Organization (FAO) digital Soil Map of the World (SMW) by employing continuous pedotransfer functions (PTF) within global pedon databases and linking these results to the SMW. The procedure first estimated representative soil properties for the FAO soil units by statistical analyses and taxotransfer depth algorithms [Food and Agriculture Organization (FAO), 1996]. The representative soil properties estimated for two layers of depths (0-30 and 30-100 cm) included particle-size distribution, dominant soil texture, organic carbon content, coarse fragments, bulk density, and porosity. After representative soil properties for the FAO soil units were estimated, these values were substituted into three different pedotransfer functions (PTF) models by Rawls et al. [1982], Saxton et al. [1986], and Batjes [1996a]. The Saxton PTF model was finally selected to calculate available water content because it only required particle-size distribution data and results closely agreed with the Rawls and Batjes PTF models that used both particle-size distribution and organic matter data. Soil water-holding capacities were then estimated by multiplying the available water content by the soil layer thickness and integrating over an effective crop root depth of 1 m or less (i.e., encountered shallow impermeable layers) and another soil depth data layer of 2.5 m or less.

[Soil moisture dynamics and water balance of Salix psammophila shrubs in south edge of Mu Us Sandy Land].

Science.gov (United States)

An, Hui; An, Yu

2011-09-01

Taking the artificial sand-fixing Salix psammophila shrubs with different plant density (0.2, 0.6, and 0.8 plants x m(-2)) in Mu Us Sandy Land as test objects, this paper studied the soil moisture dynamics and evapotranspiration during growth season. There existed obvious differences in the soil moisture dynamics and evapotranspiration among the shrubs. The soil moisture content changed in single-hump-shape with the increase of plant density, and in "S" shape during growth season, being closely correlated with precipitation. The evapotranspiration was the highest (114.5 mm) in the shrubs with a density 0.8 plants x m(-1), accounting for 90.8% of the total precipitation during growth season, and the lowest (109.7 mm) in the shrubs with a density 0.6 plants x m(-2) Based on the soil moisture dynamics and water balance characteristics, the appropriate planting density of S. psammophila shrubs in Mu Us Sandy Land could be 0.6 plants x m(-2).

Effects of water salinity on the correlation scale of Root density and Evapotranspiration fluxes

Science.gov (United States)

Ajeel, Ali; Saeed, Ali; Dragonetti, Giovanna; Comegna, Alessandro; Lamaddalena, Nicola; Coppola, Antonio

2015-04-01

Spatial pattern and the correlation of different soil and plant parameters were examined in a green bean field experiment carried out at the Mediterranean Agronomic Institute of Bari, Italy. The experiment aimed to evaluate the role of local processes of salt accumulation and transport which mainly influences the evapotranspiration (and thus the root uptake) processes under different water salinity levels. The experiment consisted of three transects of 30m length and 4.2 m width, irrigated with three different salinity levels (1dSm-1, 3dSm-1, 6dSm-1). Soil measurements (electrical conductivity and soil water content) were monitored along transects in 24 sites, 1 m apart by using TDR probes and Diviner 2000. Water storage measured by TDR and Diviner sensor were coupled for calculating directly the evapotranspiration fluxes along the whole soil profile under the different salinity levels imposed during the experiment. In the same sites, crop monitoring involved measurements of Leaf Area Index (LAI), Osmotic Potential (OP), Leaf Water Potential (LWP), and Root length Density (RlD). Soil and plant properties were analyzed by classical statistics, geostatistics methods and spectral analysis. Results indicated moderate to large spatial variability across the field for soil and plant parameters under all salinity treatments. Furthermore, cross-semivariograms exhibited a strong positive spatial interdependence between electrical conductivity of soil solution ECw with ET and RlD in transect treated with 3dSm-1 as well as with LAI in transect treated with 6dSm-1 at all 24 monitoring sites. Spectral analysis enabled to identify the observation window to sample the soil salinity information responsible for a given plant response (ET, OP, RlD). It is also allowed a clear identification of the spatial scale at which the soil water salinity level and distribution and the crop response in terms of actual evapotranspiration ET, RlD and OP, are actually correlated. Additionally

An analytical solution for the estimation of the critical available soil water fraction for a single layer water balance model under growing crops

Directory of Open Access Journals (Sweden)

N. Brisson

1998-01-01

Full Text Available In the framework of simplified water balance models devoted to irrigation scheduling or crop modelling, the relative transpiration rate (the ratio of actual to maximal transpiration is assumed to decrease linearly when the soil dries out below a critical available water value. This value is usually expressed as a fraction, F, of the maximal available soil water content. The present work aims to use the basic laws governing water transfer through the plants at a daily time step to compute F dynamically as the crop grows. It can be regarded as an expansion of Slabbers' (1980 approach to crop growing conditions. Starting from the mathematical representation given by single-root models (Gardner, 1960, an analytical expression for F is derived, using simplified hypotheses. This expression accounts for plant attributes such as the mean root radius, the critical leaf water potential for stomatal closure and the root length density profile growing with the crop. Environmental factors such as soil type and atmospheric demand also influence F. The structural influence of soil comes from the required introduction of the bulk soil hydraulic conductivity in the single-root model. The shape of the root length density profile is assumed to be sigmoidal and a new profile is calculated at each value of the rooting depth. A sensitivity analysis of F to all those factors is presented. The first general result is that F decreases as the root system grows in depth. Differences in the shape of the root profile can be responsible for differential water stress sensitivity in the early stages of growth. Yet, low critical leaf water potential can compensate partially for a poor root profile. Conversely, F is relatively insensitive to the average root radius. F sensitivity to soil type seems somewhat artificial: given the bulk soil hydraulic conductivity formula, the soil sensitivity results from F being expressed as a fraction of the maximal available soil water content

Validation of a spatial–temporal soil water movement and plant water uptake model

KAUST Repository

HEPPELL, J.

2014-06-01

© 2014, (publisher). All rights reserved. Management and irrigation of plants increasingly relies on accurate mathematical models for the movement of water within unsaturated soils. Current models often use values for water content and soil parameters that are averaged over the soil profile. However, many applications require models to more accurately represent the soil–plant–atmosphere continuum, in particular, water movement and saturation within specific parts of the soil profile. In this paper a mathematical model for water uptake by a plant root system from unsaturated soil is presented. The model provides an estimate of the water content level within the soil at different depths, and the uptake of water by the root system. The model was validated using field data, which include hourly water content values at five different soil depths under a grass/herb cover over 1 year, to obtain a fully calibrated system for plant water uptake with respect to climate conditions. When compared quantitatively to a simple water balance model, the proposed model achieves a better fit to the experimental data due to its ability to vary water content with depth. To accurately model the water content in the soil profile, the soil water retention curve and saturated hydraulic conductivity needed to vary with depth.

does earthworms density really modify soil's hydrodynamic ...

African Journals Online (AJOL)

N. Ababsa,, M. Kribaa, D. Addad, L. Tamrabet and M. Baha

1 mai 2016 ... Journal of Fundamental and Applied Sciences is licensed under a Creative Commons Attribution-NonCommercial 4.0. International License. Libraries Resource Directory. We are listed under Research Associations category. DOES EARTHWORMS DENSITY REALLY MODIFY SOIL'S HYDRODYNAMIC.

Simultaneous bulk density and soil moisture determination by attenuation of 137 Cs and 241 Am

International Nuclear Information System (INIS)

Barros Ferraz, E.S. de.

1974-01-01

The method of simultaneous bulk density and soil moisture determination by attenuation of 241 Am and 137 Cs gamma-radiation is introduced and studied with detail. Theoretical considerations are made about the attenuation process in the absorbers, the form of solving the problem of two unknowns, the sensitivity of the method the influences of the resolution time of the electronic counting equipment, and of the Compton scattering in the sample. From the methodological point of view studies are made about the influence of the geometry, adjustment of counting system, choice of radiation sources, attenuation coefficient and the manner of obtaining reliable measurements. Data obtained are analysed, discussed and compared with those found in the literature. Finally the author presents some applications of the method, its use in soil-water movement studies, in soil profile compaction studies, and specially in swelling soils. (author)

Differential growth responses to water balance of coexisting deciduous tree species are linked to wood density in a Bolivian tropical dry forest.

Directory of Open Access Journals (Sweden)

Hooz A Mendivelso

Full Text Available A seasonal period of water deficit characterizes tropical dry forests (TDFs. There, sympatric tree species exhibit a diversity of growth rates, functional traits, and responses to drought, suggesting that each species may possess different strategies to grow under different conditions of water availability. The evaluation of the long-term growth responses to changes in the soil water balance should provide an understanding of how and when coexisting tree species respond to water deficit in TDFs. Furthermore, such differential growth responses may be linked to functional traits related to water storage and conductance. We used dendrochronology and climate data to retrospectively assess how the radial growth of seven coexisting deciduous tree species responded to the seasonal soil water balance in a Bolivian TDF. Linear mixed-effects models were used to quantify the relationships between basal area increment and seasonal water balance. We related these relationships with wood density and sapwood production to assess if they affect the growth responses to climate. The growth of all species responded positively to water balance during the wet season, but such responses differed among species as a function of their wood density. For instance, species with a strong growth response to water availability averaged a low wood density which may facilitate the storage of water in the stem. By contrast, species with very dense wood were those whose growth was less sensitive to water availability. Coexisting tree species thus show differential growth responses to changes in soil water balance during the wet season. Our findings also provide a link between wood density, a trait related to the ability of trees to store water in the stem, and wood formation in response to water availability.

Differential Growth Responses to Water Balance of Coexisting Deciduous Tree Species Are Linked to Wood Density in a Bolivian Tropical Dry Forest

Science.gov (United States)

Mendivelso, Hooz A.; Camarero, J. Julio; Royo Obregón, Oriol; Gutiérrez, Emilia; Toledo, Marisol

2013-01-01

A seasonal period of water deficit characterizes tropical dry forests (TDFs). There, sympatric tree species exhibit a diversity of growth rates, functional traits, and responses to drought, suggesting that each species may possess different strategies to grow under different conditions of water availability. The evaluation of the long-term growth responses to changes in the soil water balance should provide an understanding of how and when coexisting tree species respond to water deficit in TDFs. Furthermore, such differential growth responses may be linked to functional traits related to water storage and conductance. We used dendrochronology and climate data to retrospectively assess how the radial growth of seven coexisting deciduous tree species responded to the seasonal soil water balance in a Bolivian TDF. Linear mixed-effects models were used to quantify the relationships between basal area increment and seasonal water balance. We related these relationships with wood density and sapwood production to assess if they affect the growth responses to climate. The growth of all species responded positively to water balance during the wet season, but such responses differed among species as a function of their wood density. For instance, species with a strong growth response to water availability averaged a low wood density which may facilitate the storage of water in the stem. By contrast, species with very dense wood were those whose growth was less sensitive to water availability. Coexisting tree species thus show differential growth responses to changes in soil water balance during the wet season. Our findings also provide a link between wood density, a trait related to the ability of trees to store water in the stem, and wood formation in response to water availability. PMID:24116001

Correction of resistance to penetration by pedofunctions and a reference soil water content

Directory of Open Access Journals (Sweden)

Moacir Tuzzin de Moraes

2012-12-01

Full Text Available The soil penetration resistance is an important indicator of soil compaction and is strongly influenced by soil water content. The objective of this study was to develop mathematical models to normalize soil penetration resistance (SPR, using a reference value of gravimetric soil water content (U. For this purpose, SPR was determined with an impact penetrometer, in an experiment on a Dystroferric Red Latossol (Rhodic Eutrudox, at six levels of soil compaction, induced by mechanical chiseling and additional compaction by the traffic of a harvester (four, eight, 10, and 20 passes; in addition to a control treatment under no-tillage, without chiseling or additional compaction. To broaden the range of U values, SPR was evaluated in different periods. Undisturbed soil cores were sampled to quantify the soil bulk density (BD. Pedotransfer functions were generated correlating the values of U and BD to the SPR values. By these functions, the SPR was adequately corrected for all U and BD data ranges. The method requires only SPR and U as input variables in the models. However, different pedofunctions are needed according to the soil layer evaluated. After adjusting the pedotransfer functions, the differences in the soil compaction levels among the treatments, previously masked by variations of U, became detectable.

Physical Quality Indicators and Mechanical Behavior of Agricultural Soils of Argentina.

Science.gov (United States)

Imhoff, Silvia; da Silva, Alvaro Pires; Ghiberto, Pablo J; Tormena, Cássio A; Pilatti, Miguel A; Libardi, Paulo L

2016-01-01

Mollisols of Santa Fe have different tilth and load support capacity. Despite the importance of these attributes to achieve a sustainable crop production, few information is available. The objectives of this study are i) to assess soil physical indicators related to plant growth and to soil mechanical behavior; and ii) to establish relationships to estimate the impact of soil loading on the soil quality to plant growth. The study was carried out on Argiudolls and Hapludolls of Santa Fe. Soil samples were collected to determine texture, organic matter content, bulk density, water retention curve, soil resistance to penetration, least limiting water range, critical bulk density for plant growth, compression index, pre-consolidation pressure and soil compressibility. Water retention curve and soil resistance to penetration were linearly and significantly related to clay and organic matter (R2 = 0.91 and R2 = 0.84). The pedotransfer functions of water retention curve and soil resistance to penetration allowed the estimation of the least limiting water range and critical bulk density for plant growth. A significant nonlinear relationship was found between critical bulk density for plant growth and clay content (R2 = 0.98). Compression index was significantly related to bulk density, water content, organic matter and clay plus silt content (R2 = 0.77). Pre-consolidation pressure was significantly related to organic matter, clay and water content (R2 = 0.77). Soil compressibility was significantly related to initial soil bulk density, clay and water content. A nonlinear and significantly pedotransfer function (R2 = 0.88) was developed to predict the maximum acceptable pressure to be applied during tillage operations by introducing critical bulk density for plant growth in the compression model. The developed pedotransfer function provides a useful tool to link the mechanical behavior and tilth of the soils studied.

Density evaluation by computerized tomography in plain soils over different manipulation systems

International Nuclear Information System (INIS)

Pedrotti, Alceu

1996-08-01

The objective of this paper is the evaluation of a plain soil density in different culture systems determined by X ray computerized tomography.It was observed a larger variation in densities in soils profiles analysed. The identification of layers is better utilising computerized tomography than others technic

Soils and water [Chapter 18

Science.gov (United States)

Goran Berndes; Heather Youngs; Maria Victoria Ramos Ballester; Heitor Cantarella; Annette L. Cowie; Graham Jewitt; Luiz Antonio Martinelli; Dan Neary

2015-01-01

Bioenergy production can have positive or negative impacts on soil and water. To best understand these impacts, the effects of bioenergy systems on water and soil resources should be assessed as part of an integrated analysis considering environmental, social and economic dimensions. Bioenergy production systems that are strategically integrated in the landscape to...

Using soil water sensors to improve irrigation management

Science.gov (United States)

Irrigation water management has to do with the appropriate application of water to soils, in terms of amounts, rates, and timing to satisfy crop water demands while protecting the soil and water resources from degradation. In this regard, sensors can be used to monitor the soil water status; and som...

Governing equations of transient soil water flow and soil water flux in multi-dimensional fractional anisotropic media and fractional time

OpenAIRE

M. L. Kavvas; A. Ercan; J. Polsinelli

2017-01-01

In this study dimensionally consistent governing equations of continuity and motion for transient soil water flow and soil water flux in fractional time and in fractional multiple space dimensions in anisotropic media are developed. Due to the anisotropy in the hydraulic conductivities of natural soils, the soil medium within which the soil water flow occurs is essentially anisotropic. Accordingly, in this study the fractional dimensions in two horizontal and one vertical di...

Organic compounds in hot-water-soluble fractions from water repellent soils

Science.gov (United States)

Atanassova, Irena; Doerr, Stefan

2014-05-01

Water repellency (WR) is a soil property providing hydrophobic protection and preventing rapid microbial decomposition of organic matter entering the soil with litter or plant residues. Global warming can cause changes in WR, thus influencing water storage and plant productivity. Here we assess two different approaches for analysis of organic compounds composition in hot water extracts from accelerated solvent extraction (ASE) of water repellent soils. Extracts were lyophilized, fractionated on SiO2 (sand) and SPE cartridge, and measured by GC/MS. Dominant compounds were aromatic acids, short chain dicarboxylic acids (C4-C9), sugars, short chain fatty acids (C8-C18), and esters of stearic and palmitic acids. Polar compounds (mainly sugars) were adsorbed on applying SPE clean-up procedure, while esters were highly abundant. In addition to the removal of polar compounds, hydrophobic esters and hydrocarbons (alkanes and alkenes particle wettability and C dynamics in soils. Key words: soil water repellency, hot water soluble carbon (HWSC), GC/MS, hydrophobic compounds

Barrier erosion control test plan: Gravel mulch, vegetation, and soil water interactions

Energy Technology Data Exchange (ETDEWEB)

Waugh, W.J.; Link, S.O. (Pacific Northwest Lab., Richland, WA (USA))

1988-07-01

Soil erosion could reduce the water storage capacity of barriers that have been proposed for the disposal of near-surface waste at the US Department of Energy's Hanford Site. Gravel mixed into the top soil surface may create a self-healing veneer that greatly retards soil loss. However, gravel admixtures may also enhance infiltration of rainwater, suppress plant growth and water extraction, and lead to the leaching of underlying waste. This report describes plans for two experiments that were designed to test hypotheses concerning the interactive effects of surface gravel admixtures, revegetation, and enhanced precipitation on soil water balance and plant abundance. The first experiment is a factorial field plot set up on the site selected as a soil borrow area for the eventual construction of barriers. The treatments, arranged in a a split-split-plot design structure, include two densities of gravel admix, a mixture of native and introduced grasses, and irrigation to simulate a wetter climate. Changes in soil water storage and plant cover are monitored with neutron moisture probes and point intercept sampling, respectively. The second experiment consists of an array of 80 lysimeters containing several different barrier prototypes. Surface treatments are similar to the field-plot experiment. Drainage is collected from a valve at the base of each lysimeter tube, and evapotranspiration is estimated by subtraction. The lysimeters are also designed to be coupled to a whole-plant gas exchange system that will be used to conduct controlled experiments on evapotranspiration for modeling purposes. 56 refs., 6 figs., 8 tabs.

Soil aggregation and slope stability related to soil density, root length, and mycorrhiza

Science.gov (United States)

Graf, Frank; Frei, Martin

2013-04-01

Eco-engineering measures combine the use of living plants and inert mechanical constructions to protect slopes against erosion and shallow mass movement. Whereas in geotechnical engineering several performance standards and guidelines for structural safety and serviceability of construction exist, there is a lack of comparable tools in the field of ecological restoration. Various indicators have been proposed, including the fractal dimension of soil particle size distribution, microbiological parameters, and soil aggregate stability. We present results of an soil aggregate stability investigation and compare them with literature data of the angle of internal friction ?' which is conventionally used in slope stability analysis and soil failure calculation. Aggregate stability tests were performed with samples of differently treated moraine, including soil at low (~15.5 kN/m³) and high (~19.0 kN/m³) dry unit weight, soil planted with Alnus incana (White Alder) as well as the combination of soil planted with alder and inoculated with the mycorrhizal fungus Melanogaster variegatus s.l. After a 20 weeks growth period in a greenhouse, a total of 100 samples was tested and evaluated. Positive correlations were found between the soil aggregate stability and the three variables dry unit weight, root length per soil volume, and degree of mycorrhization. Based on robust statistics it turned out that dry unit weight and mycorrhization degree were strongest correlated with soil aggregate stability. Compared to the non-inoculated control plants, mycorrhized White Alder produced significantly more roots and higher soil aggregate stability. Furthermore, the combined biological effect of plant roots and mycorrhizal mycelia on aggregate stability on soil with low density (~15.5 kN/m³) was comparable to the compaction effect of the pure soil from 15.5 to ~19.0 kN/m³. Literature data on the effect of vegetation on the angle of internal friction ?' of the same moraine showed

Predicting Soil-Water Characteristics from Volumetric Contents of Pore-Size Analogue Particle Fractions

DEFF Research Database (Denmark)

Naveed, Muhammad; Møldrup, Per; Tuller, Markus

*-model) for the SWC, derived from readily available soil properties such as texture and bulk density. A total of 46 soils from different horizons at 15 locations across Denmark were used for models evaluation. The Xw-model predicts the volumetric water content as a function of volumetric fines content (organic matter...... and clay). It performed reasonably well for the dry-end (above a pF value of 2.0; pF = log(|Ψ|), where Ψ is the matric potential in cm), but did not do as well closer to saturated conditions. The Xw*-model gives the volumetric water content as a function of volumetric content of particle size fractions...... (organic matter, clay, silt, fine and coarse sand), variably included in the model depending on the pF value. The volumetric content of a particular soil particle size fraction was included in the model if it was assumed to contribute to the pore size fraction still occupied with water at the given p...

Geophysical surveys combined with laboratory soil column experiments to identify and explore risk areas for soil and water pollution in feedlots

Science.gov (United States)

Espejo-Pérez, Antonio Jesus; Sainato, Claudia Mabel; Jairo Márquez-Molina, John; Giráldez, Juan Vicente; Vanderlinden, Karl

2014-05-01

Changes of land use without a correct planning may produce its deterioration with their social, economical and environmental irreversible consequences over short to medium time range. In Argentina, the expansion of soybean fields induced a reduction of the area of pastures dedicated to stockbreeding. As cattle activity is being progressively concentrated on small pens, at feedlots farms, problems of soil and water pollution, mainly by nitrate, have been detected. The characterization of the spatial and temporal variability of soil water content is very important because the mostly advective transport of solutes. To avoid intensive soil samplings, very expensive, one has to recur to geophysical exploration methods. The objective of this work was to identify risk areas within a feedlot of the NW zone of Buenos Aires Province, in Argentina through geophysical methods. The surveys were carried out with an electromagnetic induction profiler EMI-400 (GSSI) and a Time domain Reflectometry (TDR) survey of depth 0-0.10 m with soil sampling and measurement of moisture content with gravimetric method (0-1.0 m). Several trenches were dug inside the pens and also at a test site, where texture, apparent density, saturated hydraulic conductivity (Ks), electrical conductivity of the saturation paste extract and organic matter content (OM) were measured. The water retention curves for these soils were also determined. At one of the pens undisturbed soil columns were extracted at 3 locations. Laboratory analysis for 0-1.0 m indicated that soil texture was classified as sandy loam, average organic matter content (OM) was greater than 2.3% with low values of apparent density in the first 10 cm. The range of spatial dependence of data suggested that the number of soil samples could be reduced. Soil apparent electrical conductivity (ECa) and soil moisture were well correlated and indicated a clear spatial pattern in the corrals. TDR performance was acceptable to identify the spatial

Manipulating Crop Density to Optimize Nitrogen and Water Use: An Application of Precision Agroecology

Science.gov (United States)

Brown, T. T.; Huggins, D. R.; Smith, J. L.; Keller, C. K.; Kruger, C.

2011-12-01

Rising levels of reactive nitrogen (Nr) in the environment coupled with increasing population positions agriculture as a major contributor for supplying food and ecosystem services to the world. The concept of Precision Agroecology (PA) explicitly recognizes the importance of time and place by combining the principles of precision farming with ecology creating a framework that can lead to improvements in Nr use efficiency. In the Palouse region of the Pacific Northwest, USA, relationships between productivity, N dynamics and cycling, water availability, and environmental impacts result from intricate spatial and temporal variations in soil, ecosystem processes, and socioeconomic factors. Our research goal is to investigate N use efficiency (NUE) in the context of factors that regulate site-specific environmental and economic conditions and to develop the concept of PA for use in sustainable agroecosystems and science-based Nr policy. Nitrogen and plant density field trials with winter wheat (Triticum aestivum L.) were conducted at the Washington State University Cook Agronomy Farm near Pullman, WA under long-term no-tillage management in 2010 and 2011. Treatments were imposed across environmentally heterogeneous field conditions to assess soil, crop and environmental interactions. Microplots with a split N application using 15N-labeled fertilizer were established in 2011 to examine the impact of N timing on uptake of fertilizer and soil N throughout the growing season for two plant density treatments. Preliminary data show that plant density manipulation combined with precision N applications regulated water and N use and resulted in greater wheat yield with less seed and N inputs. These findings indicate that improvements to NUE and agroecosystem sustainability should consider landscape-scale patterns driving productivity (e.g., spatial and temporal dynamics of water availability and N transformations) and would benefit from policy incentives that promote a PA

Field soil-water properties measured through radiation techniques

International Nuclear Information System (INIS)

1984-07-01

This report shows a major effort to make soil physics applicable to the behaviour of the field soils and presents a rich and diverse set of data which are essential for the development of effective soil-water management practices that improve and conserve the quality and quantity of agricultural lands. This piece of research has shown that the neutron moisture meter together with some complementary instruments like tensiometers, can be used not only to measure soil water contents but also be extremely handy to measure soil hydraulic characteristics and soil water flow. It is, however, recognized that hydraulic conductivity is highly sensitive to small changes in soil water content and texture, being extremely variable spatially and temporally

Influence of Height Waterlogging on Soil Physical Properties of Potential and Actual Acid Sulphate Soils

Directory of Open Access Journals (Sweden)

Arifin Fahmi

2014-06-01

Full Text Available Water management is main factor that determines the successful of rice cultivation in acid sulphate soil. Soil waterlogging determines the direction and rate of chemical, geochemical and biological reaction in the soil, indirectly these reactions may influence to the changes of soil psycal properties during soil waterlogging process. The experiment was aimed to study the changes of two type of acid sulphate soils physical properties during rice straw decomposition processes. The research was conducted in the greenhouse consisting of the three treatment factors using the completely randomized design with three replications. The first factor was soil type: potential acid sulphate soil (PASS and actual acid sulphate soil (AASS. The second factor was height of water waterlogging: 0.5-1.0 cm (muddy water–level condition and 4.0 cm from above the soil surface (waterlogged. The third factor was organic matter type: rice straw (RS, purun tikus (Eleocharis dulcis (PT and mixed of RS and PT (MX. Soil physical properties such as aggregate stability, total soil porosity, soil permeability, soil particle density and bulk density were observed at the end of experiment (vegetative maximum stage. The results showed that acid sulphate soil type had large effect on soil physicl properties, soil waterlogging decreased aggregate stability, soil particle density and bulk density both of soil type.

Water transport in desert alluvial soil

International Nuclear Information System (INIS)

Kearl, P.M.

1982-04-01

Safe storage of radioactive waste buried in an arid alluvial soil requires extensive site characterization of the physical process influencing moisture movement which could act as a transport medium for the migration of radionuclides. The field portion of this study included an infiltration plot instrumented with thermocouple psychrometers and neturon moisture probe access holes. Baseline information shows a zone of higher moisture content at approximately 1.5 m (5 ft) in depth. A sprinkler system simulated a 500-year precipitation event. Results revealed water penetrated the soil to 0.9 m (2.9 ft). Due to the low moisture content, vapor transport was primarily responsible for water movement at this depth. Temperature gradients are substantially responsible for vapor transport by preferentially sorting water-vapor molecules from the surrounding air by using the soil as a molecular sieve. Adsorbed and capillary water vapor pressure increases in response to a temperature increase and releases additional water to the soil pore atmosphere to be diffused away

Carbon storage potential in size–density fractions from semi-natural grassland ecosystems with different productivities over varying soil depths

International Nuclear Information System (INIS)

Breulmann, Marc; Boettger, Tatjana; Buscot, François; Gruendling, Ralf; Schulz, Elke

2016-01-01

Researchers have increasingly recognised a profound need for more information on SOC stocks in the soil and the factors governing their stability and dynamics. Many questions still remain unanswered about the interplay between changes in plant communities and the extent to which changes in aboveground productivity affect the carbon dynamics in soils through changes in its quantity and quality. Therefore, the main aim of this research was to examine the SOC accumulation potential of semi-natural grasslands of different productivities and determine the distribution of SOM fractions over varying soil depth intervals (0–10, 10–20, 20–30 30–50 50–80 and 80 + cm). SOM fractionation was considered as a relative measure of stability to separate SOM associated with clay minerals from SOM of specific light densities less than 2 g cm"−"3 (size-density fractionation). Two clay-associated fractions (CF1, < 1 μm; and CF2, 1–2 μm) and two light fractions (LF1, < 1.8 g cm"−"3; and LF2, 1.8–2.0 g cm"−"3) were separated. The stability of these fractions was characterised by their carbon hot water extractability (C_H_W_E) and stable carbon isotope composition. In the semi-natural grasslands studied, most OC was stored in the top 30 cm, where turnover is rapid. Effects of low productivity grasslands became only significantly apparent when fractional OC contributions of total SOM was considered (CF1 and LF1). In deeper soil depths OC was largely attributed to the CF1 fraction of low productivity grasslands. We suggest that the majority of OM in deeper soil depth intervals is microbially-derived, as evidenced by decreasing C/N ratios and decreasing δ"1"3C values. The hot water extraction and natural δ"1"3C abundance, employed here allowed the characterisation of SOM stabilisation properties, however how climatic changes affect the fate of OM within different soil depth intervals is still unknown. - Highlights: • OC stocks over varying soil depths in extensively

Carbon storage potential in size–density fractions from semi-natural grassland ecosystems with different productivities over varying soil depths

Energy Technology Data Exchange (ETDEWEB)

Breulmann, Marc [Helmholtz-Centre for Environmental Research – UFZ, Department of Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle (Germany); Helmholtz-Centre for Environmental Research – UFZ, Environmental and Biotechnology Centre (UBZ), Permoserstraße 15, 04318 Leipzig (Germany); Boettger, Tatjana [Helmholtz-Centre for Environmental Research – UFZ, Department of Isotope Hydrology, Theodor-Lieser-Str. 4, D-06120 Halle (Germany); Buscot, François [Helmholtz-Centre for Environmental Research – UFZ, Department of Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle (Germany); German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig (Germany); Gruendling, Ralf [Helmholtz-Centre for Environmental Research – UFZ, Department, Department of Soil Physics, Theodor-Lieser-Str. 4, D-06120 Halle (Germany); Schulz, Elke [Helmholtz-Centre for Environmental Research – UFZ, Department of Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle (Germany)

2016-03-01

Researchers have increasingly recognised a profound need for more information on SOC stocks in the soil and the factors governing their stability and dynamics. Many questions still remain unanswered about the interplay between changes in plant communities and the extent to which changes in aboveground productivity affect the carbon dynamics in soils through changes in its quantity and quality. Therefore, the main aim of this research was to examine the SOC accumulation potential of semi-natural grasslands of different productivities and determine the distribution of SOM fractions over varying soil depth intervals (0–10, 10–20, 20–30 30–50 50–80 and 80 + cm). SOM fractionation was considered as a relative measure of stability to separate SOM associated with clay minerals from SOM of specific light densities less than 2 g cm{sup −3} (size-density fractionation). Two clay-associated fractions (CF1, < 1 μm; and CF2, 1–2 μm) and two light fractions (LF1, < 1.8 g cm{sup −3}; and LF2, 1.8–2.0 g cm{sup −3}) were separated. The stability of these fractions was characterised by their carbon hot water extractability (C{sub HWE}) and stable carbon isotope composition. In the semi-natural grasslands studied, most OC was stored in the top 30 cm, where turnover is rapid. Effects of low productivity grasslands became only significantly apparent when fractional OC contributions of total SOM was considered (CF1 and LF1). In deeper soil depths OC was largely attributed to the CF1 fraction of low productivity grasslands. We suggest that the majority of OM in deeper soil depth intervals is microbially-derived, as evidenced by decreasing C/N ratios and decreasing δ{sup 13}C values. The hot water extraction and natural δ{sup 13}C abundance, employed here allowed the characterisation of SOM stabilisation properties, however how climatic changes affect the fate of OM within different soil depth intervals is still unknown. - Highlights: • OC stocks over varying

Soil water regime under homogeneous eucalyptus and pine forests

International Nuclear Information System (INIS)

Lima, W.P.; Reichardt, K.

1977-01-01

Measurement of precipitation and monthly soil water content during two consecutive years, in 6-year old plantations of eucalypt and pine, and also in an open plot containing natural herbaceous vegetation, were used to compare the soil water regime of these vegetation covers. Precipitation was measured in the open plot with a recording and a non-recording rain gage. Soil water was assessed by the neutron scattering technique to a depth of 1,80 meters. Results indicate that there was, in general, water available in the soil over the entire period of study in all three vegetation conditions. The annual range of soil water in eucalypt, pine, and in natural herbaceous vegetation was essentially similar. The analysis of the average soil water regime showed that the soil under herbaceous vegetation was, generally, more umid than the soil under eucalypt and pine during the period of soil water recharge (September through February); during the period of soil water depletion, the opposite was true. Collectively, the results permit the conclusion that there were no adverse effects on the soil water regime which could be ascribed to reflorestation with eucalypt or pine, as compared with that observed for the natural herbaceous vegetation [pt

Profiling water content in soils with TDR: Comparison with the neutron probe technique

International Nuclear Information System (INIS)

Laurent, J.P.

2000-01-01

In November 1996, at a site on the Grenoble campus a 1.2-m-long neutron access tube, a 0.8-m fibreglass Trime access tube and three sets of 1-m twin-rod TDR probes were installed. Weekly measurements were made over a 9-month period. In addition, soil samples were taken from time to time with an auger, to determine gravimetric water-contents. The soil bulk density profile was initially characterised by gammametry using a Campbell TM probe. A Troxler TM 4300 was used for the neutron-probe measurements. The TDR signals, for further processing by TDR-SSI, were logged using a Trase 2000 from Soil Moisture Equipment Corporation TM . TDR methods were employed without any special calibration of the permittivity/water-content relationship: standard internal calibrations of the devices or Topp polynomial relation were always applied. The results of all these water-content profiling methods were compared in three ways: (i) the water-content profiles were plotted directly on the same graph for different dates; (ii) all the water contents measured at all dates and all depths were plotted against a corresponding 'reference', namely neutron probe or gravimetry; (iii) water balances were calculated for each method and their respective time-profiles analysed. There was fairly good agreement among the three profiling methods, indicating that TDR is now a viable alternative to nuclear techniques for soil water-content profiling. (author)

Batch experiments versus soil pore water extraction--what makes the difference in isoproturon (bio-)availability?

Science.gov (United States)

Folberth, Christian; Suhadolc, Metka; Scherb, Hagen; Munch, Jean Charles; Schroll, Reiner

2009-10-01

Two approaches to determine pesticide (bio-)availability in soils (i) batch experiments with "extraction with an excess of water" (EEW) and (ii) the recently introduced "soil pore water (PW) extraction" of pesticide incubated soil samples have been compared with regard to the sorption behavior of the model compound isoproturon in soils. A significant correlation between TOC and adsorbed pesticide amount was found when using the EEW approach. In contrast, there was no correlation between TOC and adsorbed isoproturon when using the in situ PW extraction method. Furthermore, sorption was higher at all concentrations in the EEW method when comparing the distribution coefficients (K(d)) for both methods. Over all, sorption in incubated soil samples at an identical water tension (-15 kPa) and soil density (1.3 g cm(-3)) appears to be controlled by a complex combination of sorption driving soil parameters. Isoproturon bioavailability was found to be governed in different soils by binding strength and availability of sorption sites as well as water content, whereas the dominance of either one of these factors seems to depend on the individual composition and characteristics of the respective soil sample. Using multiple linear regression analysis we obtained furthermore indications that the soil pore structure is affected by the EEW method due to disaggregation, resulting in a higher availability of pesticide sorption sites than in undisturbed soil samples. Therefore, it can be concluded that isoproturon sorption is overestimated when using the EEW method, which should be taken into account when using data from this approach or similar batch techniques for risk assessment analysis.

Mechanical impedance of soil crusts and water content in loamy soils

Science.gov (United States)

Josa March, Ramon; Verdú, Antoni M. C.; Mas, Maria Teresa

2013-04-01

Soil crust development affects soil water dynamics and soil aeration. Soil crusts act as mechanical barriers to fluid flow and, as their mechanical impedance increases with drying, they also become obstacles to seedling emergence. As a consequence, the emergence of seedling cohorts (sensitive seeds) might be reduced. However, this may be of interest to be used as an effective system of weed control. Soil crusting is determined by several factors: soil texture, rain intensity, sedimentation processes, etc. There are different ways to characterize the crusts. One of them is to measure their mechanical impedance (MI), which is linked to their moisture level. In this study, we measured the evolution of the mechanical impedance of crusts formed by three loamy soil types (clay loam, loam and sandy clay loam, USDA) with different soil water contents. The aim of this communication was to establish a mathematical relationship between the crust water content and its MI. A saturated soil paste was prepared and placed in PVC cylinders (50 mm diameter and 10 mm height) arranged on a plastic tray. Previously the plastic tray was sprayed with a hydrophobic liquid to prevent the adherence of samples. The samples on the plastic tray were left to air-dry under laboratory conditions until their IM was measured. To measure IM, a food texture analyzer was used. The equipment incorporates a mobile arm, a load cell to apply force and a probe. The arm moves down vertically at a constant rate and the cylindrical steel probe (4 mm diameter) penetrates the soil sample vertically at a constant rate. The equipment is provided with software to store data (time, vertical distance and force values) at a rate of up to 500 points per second. Water content in crust soil samples was determined as the loss of weight after oven-drying (105°C). From the results, an exponential regression between MI and the water content was obtained (determination coefficient very close to 1). This methodology allows

Root growth, soil water variation, and grain yield response of winter wheat to supplemental irrigation

Directory of Open Access Journals (Sweden)

Jianguo Man

2016-04-01

Full Text Available Water shortage threatens agricultural sustainability in the Huang-Huai-Hai Plain of China. Thus, we investigated the effect of supplemental irrigation (SI on the root growth, soil water variation, and grain yield of winter wheat in this region by measuring the moisture content in different soil layers. Prior to SI, the soil water content (SWC at given soil depths was monitored to calculate amount of irritation water that can rehydrate the soil to target SWC. The SWC before SI was monitored to depths of 20, 40, and 60 cm in treatments of W20, W40, and W60, respectively. Rainfed treatment with no irrigation as the control (W0. The mean root weight density (RWD, triphenyl tetrazolium chloride reduction activity (TTC reduction activity, soluble protein (SP concentrations as well as catalase (CAT, and superoxide dismutase (SOD activities in W40 and W60 treatments were significantly higher than those in W20. The RWD in 60–100 cm soil layers and the root activity, SP concentrations, CAT and SOD activities in 40–60 cm soil layers in W40 treatment were significantly higher than those in W20 and W60. W40 treatment is characterized by higher SWC in the upper soil layers but lower SWC in the 60–100-cm soil layers during grain filling. The soil water consumption (SWU in the 60–100 cm soil layers from anthesis after SI to maturity was the highest in W40. The grain yield, water use efficiency (WUE, and irrigation water productivity were the highest in W40, with corresponding mean values of 9169 kg ha−1, 20.8 kg ha−1 mm−1, and 35.5 kg ha−1 mm−1. The RWD, root activities, SP concentrations, CAT and SOD activities, and SWU were strongly positively correlated with grain yield and WUE. Therefore, the optimum soil layer for SI of winter wheat after jointing is 0–40 cm.

Pore water sampling in acid sulfate soils: a new peeper method.

Science.gov (United States)

Johnston, Scott G; Burton, Edward D; Keene, Annabelle F; Bush, Richard T; Sullivan, Leigh A; Isaacson, Lloyd

2009-01-01

This study describes the design, deployment, and application of a modified equilibration dialysis device (peeper) optimized for sampling pore waters in acid sulfate soils (ASS). The modified design overcomes the limitations of traditional-style peepers, when sampling firm ASS materials over relatively large depth intervals. The new peeper device uses removable, individual cells of 25 mL volume housed in a 1.5 m long rigid, high-density polyethylene rod. The rigid housing structure allows the device to be inserted directly into relatively firm soils without requiring a supporting frame. The use of removable cells eliminates the need for a large glove-box after peeper retrieval, thus simplifying physical handling. Removable cells are easily maintained in an inert atmosphere during sample processing and the 25-mL sample volume is sufficient for undertaking multiple analyses. A field evaluation of equilibration times indicates that 32 to 38 d of deployment was necessary. Overall, the modified method is simple and effective and well suited to acquisition and processing of redox-sensitive pore water profiles>1 m deep in acid sulfate soil or any other firm wetland soils.

[Effects of canopy density on the functional group of soil macro fauna in Pinus massoniana plantations].

Science.gov (United States)

Zhou, Hong Yang; Zhang, Dan Ju; Zhang, Jie; Zhao, Yan Bo; Zhao, Bo; Wei, Da Ping; Zhang, Jian

2017-06-18

In order to understand the effects of canopy density on the functional group characteristics of soil macrofauna in Pinus massoniana plantations, we divided the captured soil fauna into five types including xylophages, predators, saprophages, omnivores and fungal feeders. The results showed that 1) Saprozoic feeders had the highest percentage of total individuals, and the omnivores and xylophages occupied higher percentages of total taxa. 2) The individual and group number of the predators, and the group number of xylophages did not change significantly under 0.5-0.6 and then decreased significantly under 0.6-0.9 canopy density. 3) With the increasing canopy density, the individual an dgroup number of predators in litter layer decreased significantly, the saprozoic individual number in 5-10 cm soil layer represented irregular trends. The individual number of xylophage increased with the depth of soil, and the group number in litter layer, the individual and group number in 5-10 cm soil layer decreased significantly. 4) Pielou evenness of xylophage had no significant changes with the canopy density, all the other diversity index of xylophage and saprophage were various with the increasing canopy density. The predatory Simpson index was stable under 0.5-0.8, and then decreased significantly under 0.8-0.9 canopy density. 5) The CCA (canonical correlation analysis) indicated that soil bulk density and moisture content were the main environmental factors affecting functional groups of soil macro fauna. Moisture content greatly impacted on the number of saprophagous individuals. But xylophage and predators were mostly affected by soil bulk density, and the predatory Simpson index was mainly affected by soil pH value and total phosphorus. Our research indicated that the structure of soil macro faunal functional group under 0.7 canopy density was comparatively stable, which would facilitate the maintenance of soil fertility and ecological function in Pinus massoniana

Characterization of field-measured soil-water properties

International Nuclear Information System (INIS)

Nielsen, D.R.; Reichardt, K.; Wierenga, P.J.

1983-01-01

As part of a five-year co-ordinated research programme of the International Atomic Energy Agency, the Use of Radiation and Isotope Techniques in Studies of Soil-Water Regimes, soil physicists examined soil-water properties of one or two field sites in 11 different countries (Brazil, Belgium, Cyprus, Chile, Israel, Japan, Madagascar, Nigeria, Senegal, Syria and Thailand). The results indicate that the redistribution method yields values of soil-water properties that have a large degree of uncertainty, and that this uncertainty is not necessarily related to the kind of soil being analysed. Regardless of the fundamental cause of this uncertainty (experimental and computational errors versus natural soil variability), the conclusion is that further developments of field technology depend upon stochastic rather than deterministic concepts

[Effects of soil wetting pattern on the soil water-thermal environment and cotton root water consumption under mulched drip irrigation].

Science.gov (United States)

Li, Dong-wei; Li, Ming-si; Liu, Dong; Lyu, Mou-chao; Jia, Yan-hui

2015-08-01

Abstract: To explore the effects of soil wetting pattern on soil water-thermal environment and water consumption of cotton root under mulched drip irrigation, a field experiment with three drip intensities (1.69, 3.46 and 6.33 L · h(-1)), was carried out in Shihezi, Xinjiang Autonomous Region. The soil matric potential, soil temperature, cotton root distribution and water consumption were measured during the growing period of cotton. The results showed that the main factor influencing the soil temperature of cotton under plastic mulch was sunlight. There was no significant difference in the soil temperature and root water uptake under different treatments. The distribution of soil matrix suction in cotton root zone under plastic mulch was more homogeneous under ' wide and shallow' soil wetting pattern (W633). Under the 'wide and shallow' soil wetting pattern, the average difference of cotton root water consumption between inner row and outer row was 0.67 mm · d(-1), which was favorable to the cotton growing trimly at both inner and outer rows; for the 'narrow and deep' soil wetting pattern (W169), the same index was 0.88 mm · d(-1), which was unfavorable to cotton growing uniformly at both inner and outer rows. So, we should select the broad-shallow type soil wetting pattern in the design of drip irrigation under mulch.

Soil Water Balance and Vegetation Dynamics in two Water-limited Mediterranean Ecosystem on Sardinia under past and future climate change

Science.gov (United States)

Corona, R.; Montaldo, N.; Albertson, J. D.

2016-12-01

hydrometeorological scenarios in the two contrasting ecosystems. Results demonstrate that vegetation dynamics are influenced by the inter-annual variability of atmospheric forcing, with vegetation density changing significantly according to seasonal rainfall amount. At the same time the vegetation dynamics affect the soil water balance.

Non-destructive estimates of soil carbonic anhydrase activity and associated soil water oxygen isotope composition

Science.gov (United States)

Jones, Sam P.; Ogée, Jérôme; Sauze, Joana; Wohl, Steven; Saavedra, Noelia; Fernández-Prado, Noelia; Maire, Juliette; Launois, Thomas; Bosc, Alexandre; Wingate, Lisa

2017-12-01

The contribution of photosynthesis and soil respiration to net land-atmosphere carbon dioxide (CO2) exchange can be estimated based on the differential influence of leaves and soils on budgets of the oxygen isotope composition (δ18O) of atmospheric CO2. To do so, the activity of carbonic anhydrases (CAs), a group of enzymes that catalyse the hydration of CO2 in soils and plants, needs to be understood. Measurements of soil CA activity typically involve the inversion of models describing the δ18O of CO2 fluxes to solve for the apparent, potentially catalysed, rate of CO2 hydration. This requires information about the δ18O of CO2 in isotopic equilibrium with soil water, typically obtained from destructive, depth-resolved sampling and extraction of soil water. In doing so, an assumption is made about the soil water pool that CO2 interacts with, which may bias estimates of CA activity if incorrect. Furthermore, this can represent a significant challenge in data collection given the potential for spatial and temporal variability in the δ18O of soil water and limited a priori information with respect to the appropriate sampling resolution and depth. We investigated whether we could circumvent this requirement by inferring the rate of CO2 hydration and the δ18O of soil water from the relationship between the δ18O of CO2 fluxes and the δ18O of CO2 at the soil surface measured at different ambient CO2 conditions. This approach was tested through laboratory incubations of air-dried soils that were re-wetted with three waters of different δ18O. Gas exchange measurements were made on these soils to estimate the rate of hydration and the δ18O of soil water, followed by soil water extraction to allow for comparison. Estimated rates of CO2 hydration were 6.8-14.6 times greater than the theoretical uncatalysed rate of hydration, indicating that CA were active in these soils. Importantly, these estimates were not significantly different among water treatments, suggesting

Simultaneous determination of soil density and moisture by gamma ray attenuation from Cs137 and Am241

International Nuclear Information System (INIS)

Barros Ferraz, E.S. de.

1974-09-01

The method of simultaneous bulk density and soil moisture determination by attenuation of 241 Am and 137 Cs gamma-radiation is introduced and studied with details. Theoretical considerations are made about the attenuation process in the absorbers, the form of solving the problem of two unknowns; the sensitivity of the method; the influences of the resolution time of the electronic counting equipment, and of the compton scattering in the sample. From the methodological point of view studies are made about the influence of the geometry, adjustment of counting system, choice of radiation sources, attenuation coeficients and the manner of obtaining reliable measurements. It is also presented some applications of the method, its use in soil-water movement studies, in soil profile compaction studies, and specially in swelling soils

[Composition and Density of Soil Fauna in the Region with Enhanced Radioactivity Level (Komi Republic, Vodnyi)].

Science.gov (United States)

Kolesnikova, A A; Kudrin, A A; Konakova, T N; Taskaeva, A A

2015-01-01

Studies on the influence of high levels of radiation on soil fauna were carried out in 2012 in the territory formed as a result of the activity of the enterprise for extraction and production of radium from reservoir water and waste of uranium ore from 1931 to 1956. At present the local radioactive pollution in this area is caused by the presence of heavy natural radionuclides 226Ra, 238U and products of their disintegration in soils. The oppression of soil invertebrate.fauna in pine forests and meadows with high levels of radionuclides and heavy metals is revealed. Also shown is the decrease in the number and density of different taxonomic groups of invertebrates, reduction of the diversity and spectrum of trophic groups and vital forms in the area with a high content of radionuclides in soil. Our results are in agreement with the results obtained by the similar studies showing negative influence of high-level ionizing radiation on soil fauna.

Large zero-tension plate lysimeters for soil water and solute collection in undisturbed soils

Directory of Open Access Journals (Sweden)

A. Peters

2009-09-01

Full Text Available Water collection from undisturbed unsaturated soils to estimate in situ water and solute fluxes in the field is a challenge, in particular if soils are heterogeneous. Large sampling devices are required if preferential flow paths are present. We present a modular plate system that allows installation of large zero-tension lysimeter plates under undisturbed soils in the field. To investigate the influence of the lysimeter on the water flow field in the soil, a numerical 2-D simulation study was conducted for homogeneous soils with uni- and bimodal pore-size distributions and stochastic Miller-Miller heterogeneity. The collection efficiency was found to be highly dependent on the hydraulic functions, infiltration rate, and lysimeter size, and was furthermore affected by the degree of heterogeneity. In homogeneous soils with high saturated conductivities the devices perform poorly and even large lysimeters (width 250 cm can be bypassed by the soil water. Heterogeneities of soil hydraulic properties result into a network of flow channels that enhance the sampling efficiency of the lysimeter plates. Solute breakthrough into zero-tension lysimeter occurs slightly retarded as compared to the free soil, but concentrations in the collected water are similar to the mean flux concentration in the undisturbed soil. To validate the results from the numerical study, a dual tracer study with seven lysimeters of 1.25×1.25 m area was conducted in the field. Three lysimeters were installed underneath a 1.2 m filling of contaminated silty sand, the others deeper in the undisturbed soil. The lysimeters directly underneath the filled soil material collected water with a collection efficiency of 45%. The deeper lysimeters did not collect any water. The arrival of the tracers showed that almost all collected water came from preferential flow paths.

X-ray CT-Derived Soil Characteristics Explain Varying Air, Water, and Solute Transport Properties across a Loamy Field

DEFF Research Database (Denmark)

Paradelo Pérez, Marcos; Katuwal, Sheela; Møldrup, Per

2016-01-01

-derived parameters by using a best subsets regression analysis. The regression coefficients improved using CTmatrix, limiting macroporosity, and genus density, while the best model for t0.05 used CTmatrix only. The scanning resolution and the time for soil structure development after mechanical activities could......The characterization of soil pore space geometry is important for explaining fluxes of air, water, and solutes through soil and understanding soil hydrogeochemical functions. X-ray computed tomography (CT) can be applied for this characterization, and in this study CT-derived parameters were used...... to explain water, air, and solute transport through soil. Forty-five soil columns (20 by 20 cm) were collected from an agricultural field in Estrup, Denmark, and subsequently scanned using a medical CT scanner. Nonreactive tracer leaching experiments were performed in the laboratory along with measurements...

Characteristics of water infiltration in layered water repellent soils

Science.gov (United States)

Hydrophobic soil can influence soil water infiltration, but information regarding the impacts of different levels of hydrophobicity within a layered soil profile is limited. An infiltration study was conducted to determine the effects of different levels of hydrophobicity and the position of the hyd...

Laboratory Performance of Five Selected Soil Moisture Sensors Applying Factory and Own Calibration Equations for Two Soil Media of Different Bulk Density and Salinity Levels

Science.gov (United States)

Matula, Svatopluk; Báťková, Kamila; Legese, Wossenu Lemma

2016-01-01

Non-destructive soil water content determination is a fundamental component for many agricultural and environmental applications. The accuracy and costs of the sensors define the measurement scheme and the ability to fit the natural heterogeneous conditions. The aim of this study was to evaluate five commercially available and relatively cheap sensors usually grouped with impedance and FDR sensors. ThetaProbe ML2x (impedance) and ECH2O EC-10, ECH2O EC-20, ECH2O EC-5, and ECH2O TE (all FDR) were tested on silica sand and loess of defined characteristics under controlled laboratory conditions. The calibrations were carried out in nine consecutive soil water contents from dry to saturated conditions (pure water and saline water). The gravimetric method was used as a reference method for the statistical evaluation (ANOVA with significance level 0.05). Generally, the results showed that our own calibrations led to more accurate soil moisture estimates. Variance component analysis arranged the factors contributing to the total variation as follows: calibration (contributed 42%), sensor type (contributed 29%), material (contributed 18%), and dry bulk density (contributed 11%). All the tested sensors performed very well within the whole range of water content, especially the sensors ECH2O EC-5 and ECH2O TE, which also performed surprisingly well in saline conditions. PMID:27854263

X-ray measurements of water fog density

International Nuclear Information System (INIS)

Camp, A.L.

1982-11-01

Water-fog densities were measured in a laboratory experiment using x-ray diagnostics. Fog densities were measured, varying the flow rate, nozzle type, nozzle configuration, nozzle height above the x-ray beam, and water surface tension. Suspended water volume fractions between 0.0008 and 0.0074 percent were measured. The fog density increases approximately as the square root of the flow rate; the other parameters had little effect on the density

Soil chemical factors and grassland species density in Emas National Park (central Brazil).

Science.gov (United States)

Amorim, P K; Batalha, M A

2008-05-01

Studies of grasslands on specific soil types suggest that different nutrients can limit biomass production and, hence, species composition and number. The Brazilian cerrado is the major savanna region in America and once covered about 2 million km(2), mainly in the Brazilian Central Plateau, under seasonal climate, with wet summer and dry winter. In view of the importance of soil chemical factors in the distribution of the vegetation forms within the Cerrado domain and which may influence the number of species, we analyzed some soil characteristics in three herbaceous vegetation forms -- hyperseasonal cerrado, seasonal cerrado, and wet grassland -- in Emas National Park, a core cerrado site, to investigate the relationship between number of species and soil characteristics. We collected vegetation and soil samples in these three vegetation forms and submitted the obtained data to multiple linear regression. We found out that aluminum and pH were the best predictors of species density, the former positively related to species density and the latter negatively related. Since the predictable variation in species density is important in determining areas of conservation, we can postulate that these two soil factors are indicators of high species density areas in tropical grasslands, which could be used in selecting priority sites for conservation.

Influence of salinity and water content on soil microorganisms

Directory of Open Access Journals (Sweden)

Nan Yan

2015-12-01

Full Text Available Salinization is one of the most serious land degradation problems facing world. Salinity results in poor plant growth and low soil microbial activity due to osmotic stress and toxic ions. Soil microorganisms play a pivotal role in soils through mineralization of organic matter into plant available nutrients. Therefore it is important to maintain high microbial activity in soils. Salinity tolerant soil microbes counteract osmotic stress by synthesizing osmolytes which allows them to maintain their cell turgor and metabolism. Osmotic potential is a function of the salt concentration in the soil solution and therefore affected by both salinity (measured as electrical conductivity at a certain water content and soil water content. Soil salinity and water content vary in time and space. Understanding the effect of changes in salinity and water content on soil microorganisms is important for crop production, sustainable land use and rehabilitation of saline soils. In this review, the effects of soil salinity and water content on microbes are discussed to guide future research into management of saline soils.

Soil Water and Temperature System (SWATS) Instrument Handbook

Energy Technology Data Exchange (ETDEWEB)

Cook, David R. [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-04-01

The soil water and temperature system (SWATS) provides vertical profiles of soil temperature, soil-water potential, and soil moisture as a function of depth below the ground surface at hourly intervals. The temperature profiles are measured directly by in situ sensors at the Central Facility and many of the extended facilities of the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility Southern Great Plains (SGP) site. The soil-water potential and soil moisture profiles are derived from measurements of soil temperature rise in response to small inputs of heat. Atmospheric scientists use the data in climate models to determine boundary conditions and to estimate the surface energy flux. The data are also useful to hydrologists, soil scientists, and agricultural scientists for determining the state of the soil.

Response of three soil water sensors to variable solution electrical conductivity in different soils

Science.gov (United States)

Commercial dielectric soil water sensors may improve management of irrigated agriculture by providing continuous field soil water information. Use of these sensors is partly limited by sensor sensitivity to variations in soil salinity and texture, which force expensive, time consuming, soil specific...

Moditored unsaturated soil transport processes as a support for large scale soil and water management

Science.gov (United States)

Vanclooster, Marnik

2010-05-01

The current societal demand for sustainable soil and water management is very large. The drivers of global and climate change exert many pressures on the soil and water ecosystems, endangering appropriate ecosystem functioning. The unsaturated soil transport processes play a key role in soil-water system functioning as it controls the fluxes of water and nutrients from the soil to plants (the pedo-biosphere link), the infiltration flux of precipitated water to groundwater and the evaporative flux, and hence the feed back from the soil to the climate system. Yet, unsaturated soil transport processes are difficult to quantify since they are affected by huge variability of the governing properties at different space-time scales and the intrinsic non-linearity of the transport processes. The incompatibility of the scales between the scale at which processes reasonably can be characterized, the scale at which the theoretical process correctly can be described and the scale at which the soil and water system need to be managed, calls for further development of scaling procedures in unsaturated zone science. It also calls for a better integration of theoretical and modelling approaches to elucidate transport processes at the appropriate scales, compatible with the sustainable soil and water management objective. Moditoring science, i.e the interdisciplinary research domain where modelling and monitoring science are linked, is currently evolving significantly in the unsaturated zone hydrology area. In this presentation, a review of current moditoring strategies/techniques will be given and illustrated for solving large scale soil and water management problems. This will also allow identifying research needs in the interdisciplinary domain of modelling and monitoring and to improve the integration of unsaturated zone science in solving soil and water management issues. A focus will be given on examples of large scale soil and water management problems in Europe.

Little effects on soil organic matter chemistry of density fractions after seven years of forest soil warming.

Science.gov (United States)

Schnecker, Jörg; Borken, Werner; Schindlbacher, Andreas; Wanek, Wolfgang

2016-12-01

Rising temperatures enhance microbial decomposition of soil organic matter (SOM) and thereby increase the soil CO 2 efflux. Elevated decomposition rates might differently affect distinct SOM pools, depending on their stability and accessibility. Soil fractions derived from density fractionation have been suggested to represent SOM pools with different turnover times and stability against microbial decomposition. To investigate the effect of soil warming on functionally different soil organic matter pools, we here investigated the chemical and isotopic composition of bulk soil and three density fractions (free particulate organic matter, fPOM; occluded particulate organic matter, oPOM; and mineral associated organic matter, MaOM) of a C-rich soil from a long-term warming experiment in a spruce forest in the Austrian Alps. At the time of sampling, the soil in this experiment had been warmed during the snow-free period for seven consecutive years. During that time no thermal adaptation of the microbial community could be identified and CO 2 release from the soil continued to be elevated by the warming treatment. Our results, which included organic carbon content, total nitrogen content, δ 13 C, Δ 14 C, δ 15 N and the chemical composition, identified by pyrolysis-GC/MS, showed no significant differences in bulk soil between warming treatment and control. Surprisingly, the differences in the three density fractions were mostly small and the direction of warming induced change was variable with fraction and soil depth. Warming led to reduced N content in topsoil oPOM and subsoil fPOM and to reduced relative abundance of N-bearing compounds in subsoil MaOM. Further, warming increased the δ 13 C of MaOM at both sampling depths, reduced the relative abundance of carbohydrates while it increased the relative abundance of lignins in subsoil oPOM. As the size of the functionally different SOM pools did not significantly change, we assume that the few and small

Attenuation coefficients of soils

International Nuclear Information System (INIS)

Martini, E.; Naziry, M.J.

1989-01-01

As a prerequisite to the interpretation of gamma-spectrometric in situ measurements of activity concentrations of soil radionuclides the attenuation of 60 to 1332 keV gamma radiation by soil samples varying in water content and density has been investigated. A useful empirical equation could be set up to describe the dependence of the mass attenuation coefficient upon photon energy for soil with a mean water content of 10%, with the results comparing well with data in the literature. The mean density of soil in the GDR was estimated at 1.6 g/cm 3 . This value was used to derive the linear attenuation coefficients, their range of variation being 10%. 7 figs., 5 tabs. (author)

Soil bulk density changes caused by mechanized harvesting: A case study in central Appalachia

Science.gov (United States)

Jingxin Wang; Chris B. LeDoux; Pam Edwards; Mark Jones; Mark Jones

2005-01-01

A mechanized harvesting system consisting of a feller-buncher and a grapple skidder was examined to quantify soil bulk density changes in a central Appalachian hardwood forest site. Soil bulk density was measured using a nuclear gauge pre-harvest and post-harvest systematically across the harvest unit and on transects across skid trails. Bulk density also was measured...

An automated microinfiltrometer to measure small-scale soil water infiltration properties

Directory of Open Access Journals (Sweden)

Gordon Dennis C.

2014-09-01

Full Text Available We developed an automated miniature constant-head tension infiltrometer that measures very small infiltration rates at millimetre resolution with minimal demands on the operator. The infiltrometer is made of 2.9 mm internal radius glass tube, with an integrated bubbling tower to maintain constant negative head and a porous mesh tip to avoid air-entry. In the bubbling tower, bubble formation and release changes the electrical resistance between two electrodes at the air-inlet. Tests were conducted on repacked sieved sands, sandy loam soil and clay loam soil, packed to a soil bulk density ρd of 1200 kg m-3 or 1400 kg m-3 and tested either air-dried or at a water potential ψ of -50 kPa. The change in water volume in the infiltrometer had a linear relationship with the number of bubbles, allowing bubble rate to be converted to infiltration rate. Sorptivity measured with the infiltrometer was similar between replicates and showed expected differences from soil texture and ρd, varying from 0.15 ± 0.01 (s.e. mm s-1/2 for 1400 kg m-3 clay loam at ψ = -50 kPa to 0.65 ± 0.06 mm s-1/2 for 1200 kg m-3 air dry sandy loam soil. An array of infiltrometers is currently being developed so many measurements can be taken simultaneously.

Soil atmosphere exchange of carbonyl sulfide (COS regulated by diffusivity depending on water-filled pore space

Directory of Open Access Journals (Sweden)

H. Van Diest

2008-04-01

Full Text Available The exchange of carbonyl sulfide (COS between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS concentration, soil water content (WC and air temperature. All investigated soils acted as sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil WC, respectively, indicating that the soil WC acts as an important biological and physical parameter for characterizing the exchange of COS between soils and the atmosphere. Different optima of deposition velocities (V_d as observed for the Chinese, Finnish and Siberian boreal soil types in relation to their soil WC, aligned at 19% in relation to the water-filled pore space (WFPS, indicating the dominating role of gas diffusion. This interpretation was supported by the linear correlation between V_d and bulk density. We suggest that the uptake of COS depends on the diffusivity dominated by WFPS, a parameter depending on soil WC, soil structure and porosity of the soil.

Water erosion and soil water infiltration in different stages of corn development and tillage systems

Directory of Open Access Journals (Sweden)

Daniel F. de Carvalho

2015-11-01

Full Text Available ABSTRACTThis study evaluated soil and water losses, soil water infiltration and infiltration rate models in soil tillage systems and corn (Zea mays, L. development stages under simulated rainfall. The treatments were: cultivation along contour lines, cultivation down the slope and exposed soil. Soil losses and infiltration in each treatment were quantified for rains applied using a portable simulator, at 0, 30, 60 and 75 days after planting. Infiltration rates were estimated using the models of Kostiakov-Lewis, Horton and Philip. Based on the obtained results, the combination of effects between soil tillage system and corn development stages reduces soil and water losses. The contour tillage system promoted improvements in soil physical properties, favoring the reduction of erosion in 59.7% (water loss and 86.6% (soil loss at 75 days after planting, and the increase in the stable infiltration rate in 223.3%, compared with the exposed soil. Associated to soil cover, contour cultivation reduces soil and water losses, and the former is more influenced by management. Horton model is the most adequate to represent soil water infiltration rate under the evaluated conditions.

Flow of gasoline-in-water microemulsion through water-saturated soil columns

International Nuclear Information System (INIS)

Ouyang, Y.; Mansell, R.S.; Rhue, R.D.

1995-01-01

Much consideration has been given to the use of surfactants to clean up nonaqueous phase liquids (NAPLs) from contaminated soil and ground water. Although this emulsification technique has shown significant potential for application in environmental remediation practices, a major obstacle leading to low washing efficiency is the potential formation of macroemulsion with unfavorable flow characteristics in porous media. This study investigated influences of the flow of leaded-gasoline-in-water (LG/W) microemulsion upon the transport of gasoline and lead (Pb) species in water-saturated soil columns. Two experiments were performed: (1) the immiscible displacement of leaded gasoline and (2) the miscible displacement of LG/W microemulsion through soil columns, followed by sequentially flushing with NaCl solution and a water/surfactant/cosurfactant (W/S/CoS) mixture. Comparison of breakthrough curves (BTC) for gasoline between the two experiments shows that about 90% of gasoline and total Pb were removed from the soil columns by NaCl solution in the LG/W microemulsion experiment as compared to 40% removal of gasoline and 10% removal of total Pb at the same process in the leaded gasoline experiment. Results indicate that gasoline and Pb species moved much more effectively through soil during miscible flow of LG/W microemulsion than during immiscible flow of leaded gasoline. In contrast to the adverse effects of macroemulsion on the transport of NAPLs, microemulsion was found to enhance the transport of gasoline through water-saturated soil. Mass balance analysis shows that the W/S/CoS mixture had a high capacity for removing residual gasoline and Pb species from contaminated soil. Comparison of water-pressure differences across the soil columns for the two experiments indicates that pore clogging by gasoline droplets was greatly minimized in the LG/W microemulsion experiment

Adult trees cause density-dependent mortality in conspecific seedlings by regulating the frequency of pathogenic soil fungi.

Science.gov (United States)

Liang, Minxia; Liu, Xubing; Gilbert, Gregory S; Zheng, Yi; Luo, Shan; Huang, Fengmin; Yu, Shixiao

2016-12-01

Negative density-dependent seedling mortality has been widely detected in tropical, subtropical and temperate forests, with soil pathogens as a major driver. Here we investigated how host density affects the composition of soil pathogen communities and consequently influences the strength of plant-soil feedbacks. In field censuses of six 1-ha permanent plots, we found that survival was much lower for newly germinated seedlings that were surrounded by more conspecific adults. The relative abundance of pathogenic fungi in soil increased with increasing conspecific tree density for five of nine tree species; more soil pathogens accumulated around roots where adult tree density was higher, and this greater pathogen frequency was associated with lower seedling survival. Our findings show how tree density influences populations of soil pathogens, which creates plant-soil feedbacks that contribute to community-level and population-level compensatory trends in seedling survival. © 2016 John Wiley & Sons Ltd/CNRS.

Soil and plant responses from land application of saline-sodic waters: Implications of management

Energy Technology Data Exchange (ETDEWEB)

Vance, G.F.; King, L.A.; Ganjegunte, G.K. [University of Wyoming, Laramie, WY (United States). Department for Renewable Resources

2008-09-15

Land application of co-produced waters from coalbed natural gas (CBNG) wells is one management option used in the Powder River Basin (PRB) of Wyoming and Montana. Unfortunately the co-produced CBNG waters may be saline and/or sodic. The objective of this study was to examine the effects of irrigation with CBNG waters on soils and plants in the PRB. Soil properties and vegetation responses resulting from 1 to 4 yr of saline sodic water (electrical conductivity (EC) 1.6-4.8 dS m{sup -1} sodium adsorption ratio (SAR), 17-57 mmol L- applications were studied during 2003 and 2004 field seasons on sites (Ustic Torriorthent Haplocambid, Haplargid and Paleargid) representing native range grasslands seeded grass hayfields and alfalfa hayfields. Parameters measured from each irrigated site were compared directly with representative non-irrigated sites. Soil chemical and physical parameters including pH, EC, SAR, exchangeable sodium percent, texture, bulk density, infiltration and Darcy flux rates, were measured at various depth intervals to 120 cm. Mulitple-year applications of saline sodic water produced consistent trends of increased soil EC AND SAR values to depths of 30 cm reduced surface infiltration rates and lowered Darcy flux rates to 120 cm. Significant differences (p {le} 0.05) were determined between irrigated and non-irrigated areas for EC, SAR infiltration rates and Darcy flux (p {le} 0.10) at most sites. Saline sodic CBNG water applications significantly increased native perennial grass biomass production and cover on irrigated as compared with non-irrigated sites; however overall species evenness decreased. Biological effects were variable and complex reflecting site-specific conditions and water and soil management strategies.

Spatial variability of physical properties of tropical soil

International Nuclear Information System (INIS)

Reichardt, K.; Libardi, P.L.; Queiroz, S.V.; Grohmann, F.

1976-04-01

A basic study with objectives of improving the use of soil and water resources under a particular condition and of developing means for controlling the dynamics of soil-water movement are presented. Special emphasis is given to the variability in space of geometric soil properties such as bulk density, particle density and texture in order to make it possible to define representative means which ideed will be usable to describe the movement of water and of salt in the entire field

Water table fluctuations and soil biogeochemistry: An experimental approach using an automated soil column system

Science.gov (United States)

Rezanezhad, F.; Couture, R.-M.; Kovac, R.; O'Connell, D.; Van Cappellen, P.

2014-02-01

Water table fluctuations significantly affect the biological and geochemical functioning of soils. Here, we introduce an automated soil column system in which the water table regime is imposed using a computer-controlled, multi-channel pump connected to a hydrostatic equilibrium reservoir and a water storage reservoir. The potential of this new system is illustrated by comparing results from two columns filled with 45 cm of the same homogenized riparian soil. In one soil column the water table remained constant at -20 cm below the soil surface, while in the other the water table oscillated between the soil surface and the bottom of the column, at a rate of 4.8 cm d-1. The experiment ran for 75 days at room temperature (25 ± 2 °C). Micro-sensors installed at -10 and -30 cm below the soil surface in the stable water table column recorded constant redox potentials on the order of 600 and -200 mV, respectively. In the fluctuating water table column, redox potentials at the same depths oscillated between oxidizing (∼700 mV) and reducing (∼-100 mV) conditions. Pore waters collected periodically and solid-phase analyses on core material obtained at the end of the experiment highlighted striking geochemical differences between the two columns, especially in the time series and depth distributions of Fe, Mn, K, P and S. Soil CO2 emissions derived from headspace gas analysis exhibited periodic variations in the fluctuating water table column, with peak values during water table drawdown. Transient redox conditions caused by the water table fluctuations enhanced microbial oxidation of soil organic matter, resulting in a pronounced depletion of particulate organic carbon in the midsection of the fluctuating water table column. Denaturing Gradient Gel Electrophoresis (DGGE) revealed the onset of differentiation of the bacterial communities in the upper (oxidizing) and lower (reducing) soil sections, although no systematic differences in microbial community structure

Linking air and water transport in intact soils to macropore characteristics inferred from X-ray computed tomography

DEFF Research Database (Denmark)

Katuwal, S.; Nørgaard, Trine; Møldrup, Per

2015-01-01

Soil macropores often control fluid flow and solute transport, and quantification of macropore characteristics including their variability in space and time are essential to predict soil hydraulic and hydrogeochemical functions. In this study, measurements of air and solute transport properties...... and direct macropore visualization by X-ray CT scanning were carried out on 17 large (19-cm diam.; 20-cm length) undisturbed soil columns sampled across a field site (Silstrup, Denmark) with natural gradients in texture and density. Air permeability (ka) at in-situ water content and -20 hPa of matric......-porosity, suggesting that density is the main control of functional soil structure and gas and solute transport at the Silstrup site. Linking gas transport and chemical tracer experiments with X-ray CT based visualization and quantification of macro-porosity was found to be a powerful method to understand field scale...

Lead accumulation in the roadside soils from heavy density motor ...

African Journals Online (AJOL)

The levels of lead pollution in the roadside soils of the heavy density motor ways of Eastern Ethiopia, in particular; Modjo, Bishoftu and Adama towns were studied. Soil samples were collected from a total of 22 sampling sites while the control samples were obtained from places about 1 km away from the main roads of each ...

Theory of evapotranspiration. 2. Soil and intercepted water evaporation

OpenAIRE

Budagovskyi, Anatolij Ivanovič; Novák, Viliam

2011-01-01

Evaporation of water from the soil is described and quantified. Formation of the soil dry surface layer is quantitatively described, as a process resulting from the difference between the evaporation and upward soil water flux to the soil evaporating level. The results of evaporation analysis are generalized even for the case of water evaporation from the soil under canopy and interaction between evaporation rate and canopy transpiration is accounted for. Relationships describing evapotranspi...

Compaction comparison testing using a modified impact soil tester and nuclear density gauge

Energy Technology Data Exchange (ETDEWEB)

Erchul, R.A.

1999-07-01

The purpose of this paper is to compare test results of a modified Impact Soil Tester (IST) on compacted soil with data obtained from the same soil using a nuclear density gauge at the US Army Corp of Engineer's Buena Vista Flood Wall project in Buena Vista, Virginia. The tests were run during construction of the earth flood wall during the summer of 1996. This comparison testing demonstrated the credibility of the procedure developed for the IST as a compacting testing device. The comparison data was obtained on a variety of soils ranging from silty sands to clays. The Flood Wall comparison compaction data for 90% Standard Proctor shows that the results of the IST as modified are consistent with the nuclear density gauge 89% of the time for all types of soil tested. However, if the soils are more cohesive than the results are consistent with the nuclear density gauge 97% of the time. In addition these comparison tests are in general agreement with comparison compaction testing using the same testing techniques and methods of compacted backfill in utility trenches conducted earlier for the Public Works Department, Chesterfield County, Virginia.

Compaction comparison testing using a modified impact soil tester and nuclear density gauge

International Nuclear Information System (INIS)

Erchul, R.A.

1999-01-01

The purpose of this paper is to compare test results of a modified Impact Soil Tester (IST) on compacted soil with data obtained from the same soil using a nuclear density gauge at the US Army Corp of Engineer's Buena Vista Flood Wall project in Buena Vista, Virginia. The tests were run during construction of the earth flood wall during the summer of 1996. This comparison testing demonstrated the credibility of the procedure developed for the IST as a compacting testing device. The comparison data was obtained on a variety of soils ranging from silty sands to clays. The Flood Wall comparison compaction data for 90% Standard Proctor shows that the results of the IST as modified are consistent with the nuclear density gauge 89% of the time for all types of soil tested. However, if the soils are more cohesive than the results are consistent with the nuclear density gauge 97% of the time. In addition these comparison tests are in general agreement with comparison compaction testing using the same testing techniques and methods of compacted backfill in utility trenches conducted earlier for the Public Works Department, Chesterfield County, Virginia

Improvement of Water Movement in an Undulating Sandy Soil Prone to Water Repellency

NARCIS (Netherlands)

Oostindie, K.; Dekker, L.W.; Wesseling, J.G.; Ritsema, C.J.

2011-01-01

The temporal dynamics of water repellency in soils strongly influence water flow. We investigated the variability of soil water content in a slight slope on a sandy fairway exhibiting water-repellent behavior. A time domain reflectometry (TDR) array of 60 probes measured water contents at 3-h

NUTRIENT BALANCE IN WATER HARVESTING SOILS

Directory of Open Access Journals (Sweden)

Díaz, F

2005-05-01

Full Text Available Dryland farming on Fuerteventura and Lanzarote (Canary Islands, Spain, which has an annual rainfall of less than 150 mm/year, has been based traditionally on water harvesting techniques (known locally as “gavias”. Periods of high productivity alternate with those of very low yield. The systems are sustainable in that they reduce erosive processes, contribute to soil and soil-water conservation and are largely responsible for maintaining the soil’s farming potential. In this paper we present the chemical fertility status and nutrient balance of soils in five “gavia” systems. The results are compared with those obtained in adjacent soils where this water harvesting technique is not used. The main crops are wheat, barley, maize, lentils and chick-peas. Since neither organic nor inorganic fertilisers are used, nutrients are derived mainly from sediments carried by runoff water. Nutrients are lost mainly through crop harvesting and harvest residues. The soils where water harvesting is used have lower salt and sodium in the exchange complex, are higher in carbon, nitrogen, copper and zinc and have similar phosphorous and potassium content. It is concluded that the systems improve the soil’s natural fertility and also that natural renovation of nutrients occurs thanks to the surface deposits of sediments, which mix with the arable layer. The system helps ensure adequate fertility levels, habitual in arid regions, thus allowing dryland farming to be carried out.

Degradation process modelization in of metallic drink containers, in soil, in water and in water-soil interaction

International Nuclear Information System (INIS)

Rieiro, I.; Trivino, V.; Gutierrez, T.; Munoz, J.; Larrea, M. T.

2013-01-01

This study asses the environmental pollution by metal release that takes place during prolonged exposures when metallic drink containers are accidentally settle in the soil in a uncontrolled way, For comparative purposes, the F111 steel and the aluminium alloy 3003, widely used for the fabrication of these containers, are also considered. A experimental design is proposed to simulate the environmental pollution during prolonged exposures. Analytical indicators have been obtained determining the metallic concentration from three types of mediums; water, water in presence of soil, and absorption-adsorption in soil. An analytical methodology has been developed by Atomic Emission Spectrometry with ICP as exciting source (ICP-OES) for metallic quantification. The method was validated using Certified Reference Materials (CRMs) of soil and water and the precision obtained varies from 5.39 to 5.86% and from 5.75 to 6.27%, respectively according to of the element studied. A statistical descriptive study followed by a factorial analysis (linear general model) has been carried out for the treatment of the experimental data packages. The metallic quantification for the three mediums shows that the soil inhibits metallic solubility in water. The process to make packages reduces in both cases their metallic cession. (Author)

Effects of fire ash on soil water retention

NARCIS (Netherlands)

Stoof, C.R.; Wesseling, J.G.; Ritsema, C.J.

2010-01-01

Despite the pronounced effect of fire on soil hydrological systems, information on the direct effect of fire on soil water retention characteristics is limited and contradictory. To increase understanding in this area, the effect of fire on soil water retention was evaluated using laboratory burning

Field, laboratory and estimated soil-water content limits

African Journals Online (AJOL)

2005-01-21

Jan 21, 2005 ... silt (0.002 to 0.05 mm) percentage to estimate the soil-water content at a given soil-water .... ar and br are the intercept and slope values of the regres- .... tions use the particle size classification of the South African Soil.

Using machine learning to predict soil bulk density on the basis of visual parameters

NARCIS (Netherlands)

Bondi, Giulia; Creamer, Rachel; Ferrari, Alessio; Fenton, Owen; Wall, David

2018-01-01

Soil structure is a key factor that supports all soil functions. Extracting intact soil cores and horizon specific samples for determination of soil physical parameters (e.g. bulk density (Bd) or particle size distribution) is a common practice for assessing indicators of soil structure. However,

Wetting properties of fungi mycelium alter soil infiltration and soil water repellency in a γ-sterilized wettable and repellent soil.

Science.gov (United States)

Chau, Henry Wai; Goh, Yit Kheng; Vujanovic, Vladimir; Si, Bing Cheng

2012-12-01

Soil water repellency (SWR) has a drastic impact on soil quality resulting in reduced infiltration, increased runoff, increased leaching, reduced plant growth, and increased soil erosion. One of the causes of SWR is hydrophobic fungal structures and exudates that change the soil-water relationship. The objective of this study was to determine whether SWR and infiltration could be manipulated through inoculation with fungi. The effect of fungi on SWR was investigated through inoculation of three fungal strains (hydrophilic -Fusarium proliferatum, chrono-amphiphilic -Trichoderma harzianum, and hydrophobic -Alternaria sp.) on a water repellent soil (WR-soil) and a wettable soil (W-soil). The change in SWR and infiltration was assessed by the water repellency index and cumulative infiltration respectively. F. proliferatum decreased the SWR on WR-soil and slightly increased SWR in W-soil, while Alternaria sp. increased SWR in both the W-soil and the WR-soil. Conversely T. harzianum increased the SWR in the W-soil and decreased the SWR in the WR-soil. All strains showed a decrease in infiltration in W-soil, while only the F. proliferatum and T. harzianum strain showed improvement in infiltration in the WR-soil. The ability of fungi to alter the SWR and enmesh soil particles results in changes to the infiltration dynamics in soil. Copyright © 2012 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Effect of restoring soil hydrological poperties on water conservation

NARCIS (Netherlands)

Moore, D.; Kostka, S.J.; Boerth, T.J.; Franklin, M.A.; Ritsema, C.J.; Dekker, L.W.; Oostindie, K.; Stoof, C.R.; Park, D.M.

2008-01-01

Water repellency in soil is more wide spread than previously thought ¿ and has a significant impact on irrigation efficiency and water conservation. Soil water repellency has been identified in many soil types under a wide array of climatic conditions world wide. Consequences include increased

Integrated water-crop-soil-management system for evaluating the quality of irrigation water

International Nuclear Information System (INIS)

Pla-Sentis, I.

1983-01-01

The authors make use of an independent balance of the salts and ions present in the water available for irrigation, based on the residence times in the soil solution that are allowed by solubility limits and drainage conditions, to develop an efficient system for evaluating the quality of such water which combines the factors: water, crop, soil and management. The system is based on the principle that such quality depends not only on the concentration and composition of the salts dissolved in the water, but also on existing possibilities and limitations in using and managing it in respect of the soil and crops, with allowance for the crop's tolerance of salinity, drainage conditions and hydrological properties of the soils, climate and current or potential practices for the management of the irrigation. If this system is used to quantify approximately the time behaviour of the concentration and composition of the salts in the soil solution, it is possible not only to predict the effects on soil, crops and drainage water, but also to evaluate the various combinations of irrigation water, soil, crops and management and to select the most suitable. It is also useful for fairly accurately diagnosing current problems of salinity and for identifying alternatives and possibilities for reclamation. Examples of its use for these purposes in Venezuela are presented with particular reference to the diagnosis of the present and future development of ''salino-sodic'' and ''sodic'' soils by means of low-salt irrigation water spread over agricultural soils with very poor drainage in a sub-humid or semi-arid tropical climate. The authors also describe the use of radiation techniques for gaining an understanding of the relations between the factors making up the system and for improving the quantitative evaluations required to diagnose problems and to select the best management methods for the available irrigation water. (author)

CO2 response to rewetting of hydrophobic soils - Can soil water repellency inhibit the 'Birch effect'?

Science.gov (United States)

Sanchez-Garcia, Carmen; Urbanek, Emilia; Doerr, Stefan

2017-04-01

Rewetting of dry soils is known to cause a short-term CO2 pulse commonly known as the 'Birch effect'. The displacement of CO2 with water during the process of wetting has been recognised as one of the sources of this pulse. The 'Birch effect' has been extensively observed in many soils, but some studies report a lack of such phenomenon, suggesting soil water repellency (SWR) as a potential cause. Water infiltration in water repellent soils can be severely restricted, causing overland flow or increased preferential flow, resulting in only a small proportion of soil pores being filled with water and therefore small gas-water replacement during wetting. Despite the suggestions of a different response of CO2 fluxes to wetting under hydrophobic conditions, this theory has never been tested. The aim of this study is to test the hypothesis that CO2 pulse does not occur during rewetting of water repellent soils. Dry homogeneous soils at water-repellent and wettable status have been rewetted with different amounts of water. CO2 flux as a response to wetting has been continuously measured with the CO2 flux analyser. Delays in infiltration and non-uniform heterogeneous water flow were observed in water repellent soils, causing an altered response in the CO2 pulse in comparison to typically observed 'Birch effect' in wettable systems. The main conclusion from the study is that water repellency not only affects water relations in soil, but has also an impact on greenhouse gas production and transport and therefore should be included as an important parameter during the sites monitoring and modelling of gas fluxes.

Application of time-lapse ERT to characterize soil-water-disease interactions of young citrus trees

Science.gov (United States)

Peddinti, S. R.; Kbvn, D. P.; Ranjan, S.; R M, P. G.

2016-12-01

Vidarbha region in Maharashtra, India is witnessing a continuous decrease in orange crop due to the propagation of `Phytopthora root rot', a water mold disease. Under favorable conditions, the disease causing bacteria can attack the plant root system and propagates to the surface (where first visual impression is made), making difficult to regain the plant health. This research aims at co-relating eco-hydrological fluxes with disease sensing parameters of orange trees. Two experimental plots around a healthy-young and declined-young orange trees were selected for our analysis. A 3-dimentional electrical resistivity tomography (ERT) (Figure) was carried at each plot to quantify the soil moisture distribution at a vadose zone. Pedo-electric relations were obtained considering modified Archie's law parameters. ERT derived moisture data was validated with time domain reflectometry (TDR) point observations. Soil moisture profiles derived from ERT were observed to be differ marginally between the two plots. Disease quantification was done by estimating the density of Phytopthora spp. inoculum in soils sampled along the root zone. Identification of Phytopthora spp. was done in the laboratory using taxonomic and morphologic criteria of the colonies. Spatio-temporal profiles of soil moisture and inoculum density were then co-related to comment on the eco-hydrological fluxes contributing to the health propagation of root rot in orange tree for implementing effective water management practices.

Contribution of soil electric resistivity measurements to the studies on soil/grapevine water relations

Directory of Open Access Journals (Sweden)

Etienne Goulet

2006-06-01

Full Text Available The classical techniques that allow to quantify the soil water status such as the gravimetric method or the use of neutrons probes do not give access to the volume of soil explored by the plant root system. On the contrary, electric tomography can be used to have a global vision on the water exchange area between soil and plant. The measurement of soil electric resistivity, as a non destructive, spatially integrative technique, has recently been introduced into viticulture. The use of performing equipment and adapted software allows for rapid data processing and gives the possibility to spatialize the variations of soil texture or humidity in two or three dimensions. Soil electric resistivity has been tested for the last three years at the Experimental Unit on Grapevine and Vine, INRA, Angers, France, to study the water supply to the vine in different “terroir” conditions. Resistivity measurements were carried out with the resistivity meter Syscal R1+ (Iris Instruments, France equipped with 21 electrodes. Those electrodes were lined up on the soil surface in a direction perpendiculary to 5 grapevine rows with an electrode spacing of 0.5 m. and a dipole-dipole arrangement. Resistivity measurements were performed on the same place at different times in order to study soil moisture variations. This experimental set up has permitted to visualise the soil stratification and individualize some positive electric anomalies corresponding to preferential drying ; this desiccation could be attributed to grapevine root activity. The soil bulk subject to the water up-take could be defined more precisely and in some types of soil, available water may even be quantified. Terroir effect on grapevine root activity has also been shown up on two different experimental parcels through electric tomography and first results indicate that it is possible to monitor the effects of soil management (inter-row grassing or different rootstocks on the water supply to the

Net carbon allocation in soybean seedlings as influenced by soil water stress at two soil temperatures

International Nuclear Information System (INIS)

McCoy, E.L.; Boersma, L.; Ekasingh, M.

1990-01-01

The influence of water stress at two soil temperatures on allocation of net photoassimilated carbon in soybean (Glycine max [L.] Merr.) was investigated using compartmental analysis. The experimental phase employed classical 14 C labeling methodology with plants equilibrated at soil water potentials of -0.04, -0.25 and -0.50 MPa; and soil temperatures of 25 and 10C. Carbon immobilization in the shoot apex generally followed leaf elongation rates with decreases in both parameters at increasing water stress at both soil temperatures. However, where moderate water stress resulted in dramatic declines in leaf elongation rates, carbon immobilization rates were sharply decreased only at severe water stress levels. Carbon immobilization was decreased in the roots and nodules of the nonwater stressed treatment by the lower soil temperature. This relation was reversed with severe water stress, and carbon immobilization in the roots and nodules was increased at the lower soil temperature. Apparently, the increased demand for growth and/or carbon storage in these tissues with increased water stress overcame the low soil temperature limitations. Both carbon pool sizes and partitioning of carbon to the sink tissues increased with moderate water stress at 25C soil temperature. Increased pool sizes were consistent with whole plant osmotic adjustment at moderate water stress. Increased partitioning to the sinks was consistent with carbon translocation processes being less severely influenced by water stress than is photosynthesis

Moisture variability resulting from water repellency in Dutch soils

NARCIS (Netherlands)

Dekker, L.W.

1998-01-01

The present study suggests that many soils in the Netherlands, in natural as well as in agricultural areas, may be water repellent to some degree, challenging the common perception that soil water repellency is only an interesting aberration. When dry, water repellent soils resist or retard

SOIL WATER BALANCE APPROACH IN ROOT ZONE OF MAIZE (95 ...

African Journals Online (AJOL)

DR. AMINU

It is usual practice to use available soil water content as a criterion for deciding when irrigation is needed. Soil water content is determined by using soil measuring techniques (capacitance probe) that describe the depletion of available soil water see fig1 and 2. The irrigation scheduling is based on the water treatment (i.e. ...

Soil water sensor response to bulk electrical conductivity

Science.gov (United States)

Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

Theoretical study of soil water balance and process of soil moisture evaporation

Directory of Open Access Journals (Sweden)

Yu. A. Savel'ev

2017-01-01

Full Text Available Nearly a half of all grain production in the Russian Federation is grown in dry regions. But crop production efficiency there depends on amount of moisture, available to plants. However deficit of soil moisture is caused not only by a lack of an atmospheric precipitation, but also inefficient water saving: losses reach 70 percent. With respect thereto it is important to reveal the factors influencing intensity of soil moisture evaporation and to develop methods of decrease in unproductive moisture losses due to evaporation. The authors researched soil water balance theoretically and determined the functional dependences of moisture loss on evaporation. Intensity of moisture evaporation depends on physicomechanical characteristics of the soil, a consistence of its surface and weather conditions. To decrease losses of moisture for evaporation it is necessary, first, to improve quality of crumbling of the soil and therefore to reduce the evaporating surface of the soil. Secondly - to create the protective mulching layer which will allow to enhance albedo of the soil and to reduce its temperature that together will reduce unproductive evaporative water losses and will increase its inflow in case of condensation from air vapors. The most widespread types of soil cultivation are considered: disk plowing and stubble mulch plowing. Agricultural background «no tillage» was chosen as a control. Subsoil mulching tillage has an essential advantage in a storage of soil moisture. So, storage of soil moisture after a disking and in control (without tillage decreased respectively by 24.9 and 19.8 mm while at the mulching tillage this indicator revised down by only 15.6 mm. The mulching layer has lower heat conductivity that provides decrease in unproductive evaporative water losses.

Determination of unsaturated hydraulic conductivity of alfisol soil in ...

African Journals Online (AJOL)

The hydrolic conductivity of soil measures the ease at which water moves through the soil by determining the flux density of water passing through the soil. The estimation of hydraulic conductivity indicates how fluids flow throuhg a substance and thus determine the water balance in the soil profile. The trend lines of ...

Changes of the water isotopic composition in unsaturated soils

International Nuclear Information System (INIS)

Feurdean, Victor; Feurdean, Lucia

2001-01-01

Based on the spatial and temporal variations of the stable isotope content in precipitation - as input in subsurface - and the mixing processes, the deuterium content in the water that moves in unsaturated zones was used to determine the most conducive season to recharge, the mechanisms for infiltration of snow or rain precipitation in humid, semi-arid or arid conditions, the episodic cycles of infiltration water mixing with the already present soil water and water vapor and whether infiltration water is or is not from local precipitation. Oscillations in the isotopic profiles of soil moisture can be used to estimate the following aspects: where piston or diffusive flow is the dominant mechanisms of water infiltration; the average velocities of the water movement in vadose zone; the influence of vegetation cover, soil type and slope exposure on the dynamics of water movement in soil; the conditions required for infiltration such as: the matrix, gravity, pressure and osmotic potentials during drainage in unsaturated soil. (authors)

Pore-water chemistry explains zinc phytotoxicity in soil.

Science.gov (United States)

Kader, Mohammed; Lamb, Dane T; Correll, Ray; Megharaj, Mallavarapu; Naidu, Ravi

2015-12-01

Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn(2+)) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2 µM for Znpw and Zn(2+), respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn(2+) in pore-water. The EC10 (total loading) values ranged from 179 to 5214 mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC. Copyright © 2015 Elsevier Inc. All rights reserved.

Quantitative imaging of cation adsorption site densities in undisturbed soil

Science.gov (United States)

Keck, Hannes; Strobel, Bjarne W.; Gustafsson, Jon-Petter; Koestel, John

2017-04-01

The vast majority of present soil system models assume a homogeneous distribution and accessibility of cation adsorption sites (CAS) within soil structural units like e.g. soil horizons. This is however in conflict with several recent studies finding that CAS in soils are not uniformly but patchily distributed at and below the cm-scale. It is likely that the small-scale distribution of CAS has significant impact on the performance of these models. However, systematic approaches to map CAS densities in undisturbed soil with 3-D resolution that could lead to respective model improvements are still lacking. We therefore investigated the 3-D distribution of the CAS in undisturbed soils using X-ray scanning and barium ions as a contrast agent. We appraised the validity of the approach by comparing X-ray image-derived cation exchange coefficients (CEC) with ones obtained using the ammonium acetate method. In the process, we evaluated whether there were larger CAS concentrations at aggregate and biopore boundaries as it is often hypothesized. We sampled eight small soil cores (approx. 10 ccm) from different locations with contrasting soil texture and organic matter contents. The samples were first saturated with a potassium chloride solution (0.1 mol per liter), whereupon a 3-D X-ray image was taken. Then, the potassium chloride solution was flushed out with a barium chloride solution (0.3 mol per liter) with barium replacing the potassium from the CAS due to its larger exchange affinity. After X-ray images as well as electrical conductivity in the effluent indicated that the entire sample had been saturated with the barium chloride, the sample was again rinsed using the potassium chloride solution. When the rinsing was complete a final 3-D X-ray image was acquired. The difference images between final and initial 3-D X-ray images were interpreted as depicting the adsorbed barium as the density of barium exceeds the one of potassium by more than 2 times. The X-ray image

Connecting carbon and nitrogen storage in rural wetland soil to groundwater abstraction for urban water supply.

Science.gov (United States)

Lewis, David Bruce; Feit, Sharon J

2015-04-01

We investigated whether groundwater abstraction for urban water supply diminishes the storage of carbon (C), nitrogen (N), and organic matter in the soil of rural wetlands. Wetland soil organic matter (SOM) benefits air and water quality by sequestering large masses of C and N. Yet, the accumulation of wetland SOM depends on soil inundation, so we hypothesized that groundwater abstraction would diminish stocks of SOM, C, and N in wetland soils. Predictions of this hypothesis were tested in two types of subtropical, depressional-basin wetland: forested swamps and herbaceous-vegetation marshes. In west-central Florida, >650 ML groundwater day(-1) are abstracted for use primarily in the Tampa Bay metropolis. At higher abstraction volumes, water tables were lower and wetlands had shorter hydroperiods (less time inundated). In turn, wetlands with shorter hydroperiods had 50-60% less SOM, C, and N per kg soil. In swamps, SOM loss caused soil bulk density to double, so areal soil C and N storage per m(2) through 30.5 cm depth was diminished by 25-30% in short-hydroperiod swamps. In herbaceous-vegetation marshes, short hydroperiods caused a sharper decline in N than in C. Soil organic matter, C, and N pools were not correlated with soil texture or with wetland draining-reflooding frequency. Many years of shortened hydroperiod were probably required to diminish soil organic matter, C, and N pools by the magnitudes we observed. This diminution might have occurred decades ago, but could be maintained contemporarily by the failure each year of chronically drained soils to retain new organic matter inputs. In sum, our study attributes the contraction of hydroperiod and loss of soil organic matter, C, and N from rural wetlands to groundwater abstraction performed largely for urban water supply, revealing teleconnections between rural ecosystem change and urban resource demand. © 2014 John Wiley & Sons Ltd.

The critical soil water content and its relation to soil water dynamics A umidade crítica e sua relação com a dinâmica da água no solo

Directory of Open Access Journals (Sweden)

Q. de Jong Van Uer

1997-06-01

Full Text Available Using an edaphic model that describes the extraction of soil water by plant roots, the occurrence of depletion zones dose to plant roots is demonstrated. These depletion zones affect the root water potential that is needed to maintain a certain transpiration rate. The results show how the critical soil water content depends on soil's hydraulic properties, transpiration rate and root density.Através de am modelo edáfico que descreve a extração de água do solo por raízes, é comprovada a ocorrência de zonas de esgotamento de água próximo as raízes, influenciando no potencial necessário nas raízes para manter uma determinada taxa de transpiração. Em função dos resultados demonstra-se como a umidade crítica de um solo é função de suas propriedades hídricas, da taxa de transpiração e da densidade do sistema radicular.

Soil physical property changes at the North American long-term soil productivity study sites: 1 and 5 years after compaction

Science.gov (United States)

Deborah S. Page-Dumroese; Martin F. Jurgensen; Allan E. Tiarks; Felix Ponder; Felipe G. Sanchez; Robert L. Fleming; J. Marty Kranabetter; Robert F. Powers; Douglas M. Stone; John D. Elioff; D. Andrew. Scott

2006-01-01

The impact of forest management operations on soil physical properties is important to understand, since management can significantly change site productivity by altering root growth potential, water infiltration and soil erosion, and water and nutrient availability. We studied soil bulk density and strength changes as indicators of soil compaction before harvesting...

CS-137 transfer factors soil-plant and density of hyphae in soil of spruce forests

International Nuclear Information System (INIS)

Klemt, E.; Deuss, H.; Drissner, J.; Krapf, M.; Miller, R.; Zibold, G.

1999-01-01

Samples of soil and plants were taken at spruce stand sites in southern Baden-Wuerttemberg. Fern always had the highest aggregated Cs-137 transfer factor (T ag ) varying between 0.01 and 0.27 m 2 kg -1 . There is a tendency for higher T ag s in soils with thicker raw humus layers, lower pH, lower cation exchange capacity (CEC) in the O h horizon, and lower clay content below the organic deposit. The density of hyphae is determined by the season and its weather conditions and it usually decreases continuously from O f to top B horizon. In analyzing our data no correlation between aggregated or horizon-specific transfer factors of different plants and density of hyphae could be found. Refs. 5 (author)

Response of the water status of soybean to changes in soil water potentials controlled by the water pressure in microporous tubes

Science.gov (United States)

Steinberg, S. L.; Henninger, D. L.

1997-01-01

Water transport through a microporous tube-soil-plant system was investigated by measuring the response of soil and plant water status to step change reductions in the water pressure within the tubes. Soybeans were germinated and grown in a porous ceramic 'soil' at a porous tube water pressure of -0.5 kpa for 28 d. During this time, the soil matric potential was nearly in equilibrium with tube water pressure. Water pressure in the porous tubes was then reduced to either -1.0, -1.5 or -2.0 kPa. Sap flow rates, leaf conductance and soil, root and leaf water potentials were measured before and after this change. A reduction in porous tube water pressure from -0.5 to -1.0 or -1.5 kPa did not result in any significant change in soil or plant water status. A reduction in porous tube water pressure to -2.0 kPa resulted in significant reductions in sap flow, leaf conductance, and soil, root and leaf water potentials. Hydraulic conductance, calculated as the transpiration rate/delta psi between two points in the water transport pathway, was used to analyse water transport through the tube-soil-plant continuum. At porous tube water pressures of -0.5 to-1.5 kPa soil moisture was readily available and hydraulic conductance of the plant limited water transport. At -2.0 kPa, hydraulic conductance of the bulk soil was the dominant factor in water movement.

Development of soil water regime under spruce stands

Directory of Open Access Journals (Sweden)

Tužinský Ladislav

2017-06-01

Full Text Available The aim of this paper is to analyse the water regime of soils under spruce ecosystems in relation to long-lasting humid and drought periods in the growing seasons 1991-2013. The dominant interval humidity in observing growing seasons is semiuvidic interval with soil moisture between hydro-limits maximal capillary capacity (MCC and point of diminished availability (PDA. Gravitationally seepage concentrated from accumulated winter season, water from melting snow and existing atmospheric precipitation occurs in the soil only at the beginning of the growing season. The supplies of soil water are significantly decreasing in the warm climate and precipitant deficient days. The greatest danger from drought threatens Norway spruce during the summer months and it depends on the duration of dry days, water supply at the beginning of the dry days, air temperature and the intensity of evapotranspiration. In the surface layers of the soil, with the maximum occurrence of active roots, the water in semiarid interval area between hydro-limits PDA and wilting point (WP decreases during the summer months. In the culminating phase occurs the drying to moisture state with capillary stationary and the insufficient supply of available water for the plants. Physiological weakening of Norway spruce caused by set of outlay components of the water balance is partially reduced by delivering of water by capillary action from deeper horizons. In extremely dry periods, soil moisture is decreasing also throughout the soil profile (0-100 cm into the bottom third of the variation margin hydro-limits MCC-PDA in the category of capillary less moving and for plants of low supply of usable water (60-90 mm. The issue of deteriorated health state of spruce ecosystems is considered to be actual. Changes and developments of hydropedological conditions which interfere the mountain forests represent the increasing danger of the drought for the spruce.

Soil water sensors:Problems, advances and potential for irrigation scheduling

Science.gov (United States)

Irrigation water management has to do with the appropriate application of water to soils, in terms of amounts, rates, and timing to satisfy crop water demands, while protecting the soil and water resources from degradation. In this regard, sensors can be used to monitor the soil water status; and so...

Soil Aggregation, Organic Carbon Concentration, and Soil Bulk Density As Affected by Cover Crop Species in a No-Tillage System

Directory of Open Access Journals (Sweden)

Adriano Stephan Nascente

2015-06-01

Full Text Available Soil aggregation and the distribution of total organic carbon (TOC may be affected by soil tillage and cover crops. The objective of this study was to determine the effects of crop rotation with cover crops on soil aggregation, TOC concentration in the soil aggregate fractions, and soil bulk density under a no-tillage system (NTS and conventional tillage system (CTS, one plowing and two disking. This was a three-year study with cover crop/rice/cover crop/rice rotations in the Brazilian Cerrado. A randomized block experimental design with six treatments and three replications was used. The cover crops (treatments were: fallow, Panicum maximum, Brachiaria ruziziensis, Brachiaria brizantha, and millet (Pennisetum glaucum. An additional treatment, fallow plus CTS, was included as a control. Soil samples were collected at the depths of 0.00-0.05 m, 0.05-0.10 m, and 0.10-0.20 m after the second rice harvest. The treatments under the NTS led to greater stability in the soil aggregates (ranging from 86.33 to 95.37 % than fallow plus CTS (ranging from 74.62 to 85.94 %. Fallow plus CTS showed the highest number of aggregates smaller than 2 mm. The cover crops affected soil bulk density differently, and the millet treatment in the NTS had the lowest values. The cover crops without incorporation provided the greatest accumulation of TOC in the soil surface layers. The TOC concentration was positively correlated with the aggregate stability index in all layers and negatively correlated with bulk density in the 0.00-0.10 m layer.

Soil water status under perennial and annual pastures on an acid duplex soil

International Nuclear Information System (INIS)

Heng, L.K.; White, R.E.; Chen, D.

2000-01-01

A comprehensive field study of soil water balance, nitrogen (N) cycling, pasture management and animal production was carried out on an acid duplex soil at Book Book near Wagga Wagga in southern New South Wales. The experiment, carried out over a 3-year period, tested the hypothesis that sown perennial grass pastures improve the sustainability of a grazing system through better use of water and N. The treatments were: annual pastures without lime (AP-), annual pastures with lime (AP+), perennial pastures without lime (PP-) and perennial pastures with lime (PP+). Soil water measurement was made using a neutron probe on one set of the treatments comprising four adjacent paddocks. Over three winter and spring periods, the results showed that perennial grass pastures, especially PP+, consistently extracted about 40 mm more soil water each year than did the annual grass pastures. As a result, surface runoff, sub-surface flow and deep drainage (percolation below 180 cm depth) were about 40 mm less from the perennial pastures. The soil water status of the four pasture treatments was simulated reasonably well using a simple soil water model. Together with the long-term simulation of deep drainage, using past meteorological records, it is shown that proper management of perennial pastures can reduce recharge to groundwater and make pastoral systems more sustainable in the high rainfall zone. However, to completely reduce recharge, more-deeply rooted plants or trees are needed. (author)

[Effects of brackish water irrigation on soil enzyme activity, soil CO2 flux and organic matter decomposition].

Science.gov (United States)

Zhang, Qian-qian; Wang, Fei; Liu, Tao; Chu, Gui-xin

2015-09-01

Brackish water irrigation utilization is an important way to alleviate water resource shortage in arid region. A field-plot experiment was set up to study the impact of the salinity level (0.31, 3.0 or 5.0 g · L(-1) NaCl) of irrigated water on activities of soil catalase, invertase, β-glucosidase, cellulase and polyphenoloxidase in drip irrigation condition, and the responses of soil CO2 flux and organic matter decomposition were also determined by soil carbon dioxide flux instrument (LI-8100) and nylon net bag method. The results showed that in contrast with fresh water irrigation treatment (CK), the activities of invertase, β-glucosidase and cellulase in the brackish water (3.0 g · L(-1)) irrigation treatment declined by 31.7%-32.4%, 29.7%-31.6%, 20.8%-24.3%, respectively, while soil polyphenoloxidase activity was obviously enhanced with increasing the salinity level of irrigated water. Compared to CK, polyphenoloxidase activity increased by 2.4% and 20.5%, respectively, in the brackish water and saline water irrigation treatments. Both soil microbial biomass carbon and microbial quotient decreased with increasing the salinity level, whereas, microbial metabolic quotient showed an increasing tendency with increasing the salinity level. Soil CO2 fluxes in the different treatments were in the order of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) ≥ saline water irrigation (5.0 g · L(-1)). Moreover, CO2 flux from plastic film mulched soil was always much higher than that from no plastic film mulched soil, regardless the salinity of irrigated water. Compared with CK, soil CO2 fluxes in the saline water and brackish water treatments decreased by 29.8% and 28.2% respectively in the boll opening period. The decomposition of either cotton straw or alfalfa straw in the different treatments was in the sequence of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) > saline water treatment (5.0 g · L(-1)). The organic matter

[Effects of biochar addition into soils in semiarid land on water infiltration under the condition of the same bulk density].

Science.gov (United States)

Qi, Rui-Peng; Zhang, Lei; Yan, Yong-Hao; Wen, Man; Zheng, Ji-Yong

2014-08-01

Making clear the effects of biochar addition on soil water infiltration process can provide the scientific basis for the evaluation of the influence of biochar application on soil hydrology in semi-arid region. In this paper, through the soil column simulation method in laboratory, the effects of biochar of three sizes (1-2 mm, 0.25-1 mm and ≤ 0.25 mm) at 4 doses (10, 50, 100 and 150 g x kg(-1)) on the cumulative infiltration, the permeability and the stable infiltration rate of two different soils (anthrosol and aeolian sandy soil) were studied. The results showed that the infiltration capacity of the anthrosol was obviously increased compared to the control, however, the one in the aeolian sandy soil was decreased due to the biochar addition. At 100 minutes after infiltration starting, the averaged cumulative infiltration was increased by 25.1% in the anthrosol with comparison to the control. Contrarily, the averaged cumulative infiltration was decreased by 11.1% in the aeolian sandy soil at 15 minutes after infiltration starting. When the dose was the same, biochar with different particle sizes improved the infiltration for the anthrosol, but for the different dose treatments, the particle size of biochar which showed the greatest improvement was different. As for the aeolian sandy soil, the infiltration increased at the dose of 10 g x kg(-1) after the addition of biochar with different particle sizes, while decreased at the higher dose of 50, 100 and 150 g x kg(-1). The cumulative infiltration of the aeolian sandy soil was decreased with the increase in addition amount of biochar with the same particle size, while it was not so for the anthrosol. The determination coefficient fitted by the Philip infiltration model ranged from 0.965 to 0.999, suggesting this model was suitable for the simulation of soil water infiltration process after biochar application. Statistical analysis of main effects showed that the biochar particle size, the biochar addition amount

An overview of soil water sensors for salinity & irrigation management

Science.gov (United States)

Irrigation water management has to do with the appropriate application of water to soils, in terms of amounts, rates, and timing to satisfy crop water demands while protecting the soil and water resources from degradation. Accurate irrigation management is even more important in salt affected soils ...

Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil

KAUST Repository

Raddadi, Noura

2018-05-31

Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils.From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4-12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls.Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil

KAUST Repository

Raddadi, Noura; Giacomucci, Lucia; Marasco, Ramona; Daffonchio, Daniele; Cherif, Ameur; Fava, Fabio

2018-01-01

Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils.From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4-12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls.Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil.

Science.gov (United States)

Raddadi, Noura; Giacomucci, Lucia; Marasco, Ramona; Daffonchio, Daniele; Cherif, Ameur; Fava, Fabio

2018-05-31

Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils. From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4-12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls. Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

Complex linkage between soil, soil water, atmosphere and Eucalyptus Plantations

Science.gov (United States)

Shukla, C.; Tiwari, K. N.

2017-12-01

Eucalyptus is most widely planted genus grown in waste land of eastern region of India to meet the pulp industry requirements. Sustainability of these plantations is of concern because in spite of higher demand water and nutrients of plantations, they are mostly planted on low-fertility soils. This study has been conducted to quantify effect of 25 years old, a fully established eucalyptus plantations on i.) Alteration in physico-chemical and hydrological properties of soil of eucalyptus plantation in comparison to soil of natural grassland and ii.) Spatio-temporal variation in soil moisture under eucalyptus plantations. Soil physico-chemical properties of two adjacent plots covered with eucatuptus and natural grasses were analyzed for three consecutive depths (i.e. 0-30 cm, 30-60 cm and 60-90 cm) with five replications in each plot. Soil infiltration rate and saturated hydraulic conductivity (Ks) were measured in-situ to incorporate the influence of macro porosity caused due to roots of plantations. Daily soil moisture at an interval of 10 cm upto 160 cm depth with 3 replications and Leaf Area Index (LAI) at an interval of 15 days with 5 replications were recorded over the year. Significant variations found at level of 0.05 between soil properties of eucalyptus and natural grass land confirm the effect of plantations on soil properties. Comparative results of soil properties show significant alteration in soil texture such as percent of sand, organic matter and Ks found more by 20%, 9% and 22% respectively in eucalyptus plot as compare to natural grass land. Available soil moisture (ASM) was found constantly minimum in top soil excluding rainy season indicate upward movement of water and nutrients during dry season. Seasonal variation in temperature (T), relative humidity (RH) and leaf area index (LAI) influenced the soil moisture extraction phenomenon. This study clearly stated the impact of long term establishment of eucalyptus plantations make considerable

Local variation in conspecific plant density influences plant-soil feedback in a natural grassland

NARCIS (Netherlands)

Kos, M.; Veendrick, Johan; Bezemer, T.M.

2013-01-01

Several studies have argued that under field conditions plant–soil feedback may be related to the local density of a plant species, but plant–soil feedback is often studied by comparing conspecific and heterospecific soils or by using mixed soil samples collected from different locations and plant

Long-term effects of deep soil loosening on root distribution and soil physical parameters in compacted lignite mine soils

Science.gov (United States)

Badorreck, Annika; Krümmelbein, Julia; Raab, Thomas

2015-04-01

Soil compaction is a major problem of soils on dumped mining substrates in Lusatia, Germany. Deep ripping and cultivation of deep rooting plant species are considered to be effective ways of agricultural recultivation. Six years after experiment start, we studied the effect of initial deep soil loosening (i.e. down to 65 cm) on root systems of rye (Secale cereale) and alfalfa (Medicago sativa) and on soil physical parameters. We conducted a soil monolith sampling for each treatment (deep loosened and unloosened) and for each plant species (in three replicates, respectively) to determine root diameter, length density and dry mass as well as soil bulk density. Further soil physical analysis comprised water retention, hydraulic conductivity and texture in three depths. The results showed different reactions of the root systems of rye and alfalfa six years after deep ripping. In the loosened soil the root biomass of the rye was lower in depths of 20-40 cm and the root biomass of alfalfa was also decreased in depths of 20-50 cm together with a lower root diameter for both plant species. Moreover, total and fine root length density was higher for alfalfa and vice versa for rye. The soil physical parameters such as bulk density showed fewer differences, despite a higher bulk density in 30-40cm for the deep loosened rye plot which indicates a more pronounced plough pan.

Performance of chromatographic systems to model soil-water sorption.

Science.gov (United States)

Hidalgo-Rodríguez, Marta; Fuguet, Elisabet; Ràfols, Clara; Rosés, Martí

2012-08-24

A systematic approach for evaluating the goodness of chromatographic systems to model the sorption of neutral organic compounds by soil from water is presented in this work. It is based on the examination of the three sources of error that determine the overall variance obtained when soil-water partition coefficients are correlated against chromatographic retention factors: the variance of the soil-water sorption data, the variance of the chromatographic data, and the variance attributed to the dissimilarity between the two systems. These contributions of variance are easily predicted through the characterization of the systems by the solvation parameter model. According to this method, several chromatographic systems besides the reference octanol-water partition system have been selected to test their performance in the emulation of soil-water sorption. The results from the experimental correlations agree with the predicted variances. The high-performance liquid chromatography system based on an immobilized artificial membrane and the micellar electrokinetic chromatography systems of sodium dodecylsulfate and sodium taurocholate provide the most precise correlation models. They have shown to predict well soil-water sorption coefficients of several tested herbicides. Octanol-water partitions and high-performance liquid chromatography measurements using C18 columns are less suited for the estimation of soil-water partition coefficients. Copyright © 2012 Elsevier B.V. All rights reserved.

Soil volumetric water content measurements using TDR technique

Directory of Open Access Journals (Sweden)

S. Vincenzi

1996-06-01

Full Text Available A physical model to measure some hydrological and thermal parameters in soils will to be set up. The vertical profiles of: volumetric water content, matric potential and temperature will be monitored in different soils. The volumetric soil water content is measured by means of the Time Domain Reflectometry (TDR technique. The result of a test to determine experimentally the reproducibility of the volumetric water content measurements is reported together with the methodology and the results of the analysis of the TDR wave forms. The analysis is based on the calculation of the travel time of the TDR signal in the wave guide embedded in the soil.

Modeling benzene permeation through drinking water high density polyethylene (HDPE) pipes.

Science.gov (United States)

Mao, Feng; Ong, Say Kee; Gaunt, James A

2015-09-01

Organic compounds such as benzene, toluene, ethyl benzene and o-, m-, and p-xylene from contaminated soil and groundwater may permeate through thermoplastic pipes which are used for the conveyance of drinking water in water distribution systems. In this study, permeation parameters of benzene in 25 mm (1 inch) standard inside dimension ratio (SIDR) 9 high density polyethylene (HDPE) pipes were estimated by fitting the measured data to a permeation model based on a combination of equilibrium partitioning and Fick's diffusion. For bulk concentrations between 6.0 and 67.5 mg/L in soil pore water, the concentration-dependent diffusion coefficients of benzene were found to range from 2.0×10(-9) to 2.8×10(-9) cm2/s while the solubility coefficient was determined to be 23.7. The simulated permeation curves of benzene for SIDR 9 and SIDR 7 series of HDPE pipes indicated that small diameter pipes were more vulnerable to permeation of benzene than large diameter pipes, and the breakthrough of benzene into the HDPE pipe was retarded and the corresponding permeation flux decreased with an increase of the pipe thickness. HDPE pipes exposed to an instantaneous plume exhibited distinguishable permeation characteristics from those exposed to a continuous source with a constant input. The properties of aquifer such as dispersion coefficients (DL) also influenced the permeation behavior of benzene through HDPE pipes.

Effects of fine root length density and root biomass on soil preferential flow in forest ecosystems

Directory of Open Access Journals (Sweden)

Yinghu Zhang

2015-04-01

Full Text Available Aim of study: The study was conducted to characterize the impacts of plant roots systems (e.g., root length density and root biomass on soil preferential flow in forest ecosystems. Area of study: The study was carried out in Jiufeng National Forest Park, Beijing, China. Material and methods: The flow patterns were measured by field dye tracing experiments. Different species (Sophora japonica Linn,Platycladus orientalis Franco, Quercus dentata Thunbwere quantified in two replicates, and 12 soil depth were applied. Plant roots were sampled in the sieving methods. Root length density and root biomass were measured by WinRHIZO. Dye coverage was implied in the image analysis, and maximum depth of dye infiltration by direct measurement. Main results: Root length density and root biomass decreased with the increasing distance from soil surface, and root length density was 81.6% higher in preferential pathways than in soil matrix, and 66.7% for root biomass with respect to all experimental plots. Plant roots were densely distributed in the upper soil layers. Dye coverage was almost 100% in the upper 5-10 cm, but then decreased rapidly with soil depth. Root length density and root biomass were different from species: Platycladus orientalis Franco > Quercus dentata Thunb > Sophora japonica Linn. Research highlights: The results indicated that fine roots systems had strong effects on soil preferential flow, particularly root channels enhancing nutrition transport across soil profiles in forest dynamics.

[Foliar water use efficiency of Platycladus orientalis sapling under different soil water contents].

Science.gov (United States)

Zhang, Yong E; Yu, Xin Xiao; Chen, Li Hua; Jia, Guo Dong; Zhao, Na; Li, Han Zhi; Chang, Xiao Min

2017-07-18

The determination of plant foliar water use efficiency will be of great value to improve our understanding about mechanism of plant water consumption and provide important basis of regional forest ecosystem management and maintenance, thus, laboratory controlled experiments were carried out to obtain Platycladus orientalis sapling foliar water use efficiency under five different soil water contents, including instantaneous water use efficiency (WUE gs ) derived from gas exchange and short-term water use efficiency (WUE cp ) caculated using carbon isotope model. The results showed that, controlled by stomatal conductance (g s ), foliar net photosynthesis rate (P n ) and transpiration rate (T r ) increased as soil water content increased, which both reached maximum va-lues at soil water content of 70%-80% field capacity (FC), while WUE gs reached a maximum of 7.26 mmol·m -2 ·s -1 at the lowest soil water content (35%-45% FC). Both δ 13 C of water-soluble leaf and twig phloem material achieved maximum values at the lowest soil water content (35%-45% FC). Besides, δ 13 C values of leaf water-soluble compounds were significantly greater than that of phloem exudates, indicating that there was depletion in 13 C in twig phloem compared with leaf water-soluble compounds and no obvious fractionation in the process of water-soluble material transportation from leaf to twig. Foliar WUE cp also reached a maximum of 7.26 mmol·m -2 ·s -1 at the lowest soil water content (35%-45% FC). There was some difference between foliar WUE gs and WUE cp under the same condition, and the average difference was 0.52 mmol·m -2 ·s -1 . The WUE gs had great space-time variability, by contrast, WUE cp was more representative. It was concluded that P. orientalis sapling adapted to drought condition by increasing water use efficiency and decreasing physiological activity.

Modeling Soil Water Retention Curves in the Dry Range Using the Hygroscopic Water Content

DEFF Research Database (Denmark)

Chen, Chong; Hu, Kelin; Arthur, Emmanuel

2014-01-01

Accurate information on the dry end (matric potential less than −1500 kPa) of soil water retention curves (SWRCs) is crucial for studying water vapor transport and evaporation in soils. The objectives of this study were to assess the potential of the Oswin model for describing the water adsorption...... curves of soils and to predict SWRCs at the dry end using the hygroscopic water content at a relative humidity of 50% (θRH50). The Oswin model yielded satisfactory fits to dry-end SWRCs for soils dominated by both 2:1 and 1:1 clay minerals. Compared with the Oswin model, the Campbell and Shiozawa model...... for soils dominated by 2:1 and 1:1 clays, respectively. Comparison of the Oswin model combined with the Kelvin equation, with water potential estimated from θRH50 (Oswin-KRH50), CS model combined with the Arthur equation (CS-A), and CS-K model, with water potential obtained from θRH50 (CS-KRH50) indicated...

Improved water density feedback model for pressurized water reactors

International Nuclear Information System (INIS)

Casadei, A.L.

1976-01-01

An improved water density feedback model has been developed for neutron diffusion calculations of PWR cores. This work addresses spectral effects on few-group cross sections due to water density changes, and water density predictions considering open channel and subcooled boiling effects. An homogenized spectral model was also derived using the unit assembly diffusion method for employment in a coarse mesh 3D diffusion computer program. The spectral and water density evaluation models described were incorporated in a 3D diffusion code, and neutronic calculations for a typical PWR were completed for both nominal and accident conditions. Comparison of neutronic calculations employing the open versus the closed channel model for accident conditions indicates that significant safety margin increases can be obtained if subcooled boiling and open channel effects are considered in accident calculations. This is attributed to effects on both core reactivity and power distribution, which result in increased margin to fuel degradation limits. For nominal operating conditions, negligible differences in core reactivity and power distribution exist since flow redistribution and subcooled voids are not significant at such conditions. The results serve to confirm the conservatism of currently employed closed channel feedback methods in accident analysis, and indicate that the model developed in this work can contribute to show increased safety margins for certain accidents

Observing plants dealing with soil water stress: Daily soil moisture fluctuations derived from polymer tensiometers

Science.gov (United States)

van der Ploeg, Martine; de Rooij, Gerrit

2014-05-01

Periods of soil water deficit often occur within a plant's life cycle, even in temperate deciduous and rain forests (Wilson et al. 2001, Grace 1999). Various experiments have shown that roots are able to sense the distribution of water in the soil, and produce signals that trigger changes in leaf expansion rate and stomatal conductance (Blackman and Davies 1985, Gollan et al. 1986, Gowing et al. 1990 Davies and Zhang 1991, Mansfield and De Silva 1994, Sadras and Milroy 1996). Partitioning of water and air in the soil, solute distribution in soil water, water flow through the soil, and water availability for plants can be determined according to the distribution of the soil water potential (e.g. Schröder et al. 2013, Kool et al. 2014). Understanding plant water uptake under dry conditions has been compromised by hydrological instrumentation with low accuracy in dry soils due to signal attenuation, or a compromised measurement range (Whalley et al. 2013). Development of polymer tensiometers makes it possible to study the soil water potential over a range meaningful for studying plant responses to water stress (Bakker et al. 2007, Van der Ploeg et al. 2008, 2010). Polymer tensiometer data obtained from a lysimeter experiment (Van der Ploeg et al. 2008) were used to analyse day-night fluctuations of soil moisture in the vicinity of maize roots. To do so, three polymer tensiometers placed in the middle of the lysimeter from a control, dry and very dry treatment (one lysimeter per treatment) were used to calculate water content changes over 12 hours. These 12 hours corresponded with the operation of the growing light. Soil water potential measurements in the hour before the growing light was turned on or off were averaged. The averaged value was used as input for the van Genuchten (1980) model. Parameters for the model were obtained from laboratory determination of water retention, with a separate model parameterization for each lysimeter setup. Results show daily

Relationship between root water uptake and soil respiration: A modeling perspective

Science.gov (United States)

Teodosio, Bertrand; Pauwels, Valentijn R. N.; Loheide, Steven P.; Daly, Edoardo

2017-08-01

Soil moisture affects and is affected by root water uptake and at the same time drives soil CO2 dynamics. Selecting root water uptake formulations in models is important since this affects the estimation of actual transpiration and soil CO2 efflux. This study aims to compare different models combining the Richards equation for soil water flow to equations describing heat transfer and air-phase CO2 production and flow. A root water uptake model (RWC), accounting only for root water compensation by rescaling water uptake rates across the vertical profile, was compared to a model (XWP) estimating water uptake as a function of the difference between soil and root xylem water potential; the latter model can account for both compensation (XWPRWC) and hydraulic redistribution (XWPHR). Models were compared in a scenario with a shallow water table, where the formulation of root water uptake plays an important role in modeling daily patterns and magnitudes of transpiration rates and CO2 efflux. Model simulations for this scenario indicated up to 20% difference in the estimated water that transpired over 50 days and up to 14% difference in carbon emitted from the soil. The models showed reduction of transpiration rates associated with water stress affecting soil CO2 efflux, with magnitudes of soil CO2 efflux being larger for the XWPHR model in wet conditions and for the RWC model as the soil dried down. The study shows the importance of choosing root water uptake models not only for estimating transpiration but also for other processes controlled by soil water content.

The computerized tomography as a new method for studing the physics of water in soil

International Nuclear Information System (INIS)

Crestana, S.

1985-08-01

In this thesis we present a new method for the investigation of water in Soil Physics using X-ray Computed Tomographic scanning. We show that the new method is in agreement with previous classical techniques such as γ-ray attenuation and gravimetric. We also demonstrate that the method allows new approaches quantitative analysis of problems such as bi and tridimensional dynamical studies as well as of heterogeneity in soil and water distributions. We apply the method to investigations of vertical infiltration of water in wet and compacted soil, simulation of drop irrigation and for preliminary studies of seed germination 'in situ'. These applicatons would not not be possible without these capabilities and advantages of this new method. Our results complement those of Perovic et al and Hainsworth et al in that we have investigated experimentally the complete dependence of H. U. (Hounsfield Units) on dry bulk density, water content and energy. Finally we also repeat some of our results obtained, using a non-medical X and γ-ray minitomograph of considerable simplicity wich will open new possibilities for the application of the proposed method. (Author) [pt

Effects of soil and water conservation practices on selected soil ...

African Journals Online (AJOL)

Although different types of soil and water conservation practices (SWCPs) were introduced, the sustainable use of these practices is far below expectations, and soil erosion continues to be a severe problem in Ethiopia. Therefore, this study was conducted at Debre Yakobe Micro-Watershed (DYMW), Northwest Ethiopia ...

Water Drainage from Unsaturated Soils in a Centrifuge Permeameter

Science.gov (United States)

Ornelas, G.; McCartney, J.; Zhang, M.

2013-12-01

This study involves an analysis of water drainage from an initially saturated silt layer in a centrifuge permeameter to evaluate the hydraulic properties of the soil layer in unsaturated conditions up to the point where the water phase becomes discontinuous. These properties include the soil water retention curve (SWRC) and the hydraulic conductivity function (HCF). The hydraulic properties of unsaturated silt are used in soil-atmosphere interaction models that take into account the role of infiltration and evaporation of water from soils due to atmospheric interaction. These models are often applied in slope stability analyses, landfill cover design, aquifer recharge analyses, and agricultural engineering. The hydraulic properties are also relevant to recent research concerning geothermal heating and cooling, as they can be used to assess the insulating effects of soil around underground heat exchangers. This study employs a high-speed geotechnical centrifuge to increase the self-weight of a compacted silt specimen atop a filter plate. Under a centrifuge acceleration of N times earth's gravity, the concept of geometric similitude indicates that the water flow process in a small-scale soil layer will be similar to those in a soil layer in the field that is N times thicker. The centrifuge acceleration also results in an increase in the hydraulic gradient across the silt specimen, which causes water to flow out of the pores following Darcy's law. The drainage test was performed until the rate of liquid water flow out of the soil layer slowed to a negligible level, which corresponds to the transition point at which further water flow can only occur due to water vapor diffusion following Fick's law. The data from the drainage test in the centrifuge were used to determine the SWRC and HCF at different depths in the silt specimen, which compared well with similar properties defined using other laboratory tests. The transition point at which liquid water flow stopped (and

CO2 efflux from soils with seasonal water repellency

Science.gov (United States)

Urbanek, Emilia; Doerr, Stefan H.

2017-10-01

Soil carbon dioxide (CO2) emissions are strongly dependent on pore water distribution, which in turn can be modified by reduced wettability. Many soils around the world are affected by soil water repellency (SWR), which reduces infiltration and results in diverse moisture distribution. SWR is temporally variable and soils can change from wettable to water-repellent and vice versa throughout the year. Effects of SWR on soil carbon (C) dynamics, and specifically on CO2 efflux, have only been studied in a few laboratory experiments and hence remain poorly understood. Existing studies suggest soil respiration is reduced with increasing severity of SWR, but the responses of soil CO2 efflux to varying water distribution created by SWR are not yet known.Here we report on the first field-based study that tests whether SWR indeed reduces soil CO2 efflux, based on in situ measurements carried out over three consecutive years at a grassland and pine forest sites under the humid temperate climate of the UK.Soil CO2 efflux was indeed very low on occasions when soil exhibited consistently high SWR and low soil moisture following long dry spells. Low CO2 efflux was also observed when SWR was absent, in spring and late autumn when soil temperatures were low, but also in summer when SWR was reduced by frequent rainfall events. The highest CO2 efflux occurred not when soil was wettable, but when SWR, and thus soil moisture, was spatially patchy, a pattern observed for the majority of the measurement period. Patchiness of SWR is likely to have created zones with two different characteristics related to CO2 production and transport. Zones with wettable soil or low persistence of SWR with higher proportion of water-filled pores are expected to provide water with high nutrient concentration resulting in higher microbial activity and CO2 production. Soil zones with high SWR persistence, on the other hand, are dominated by air-filled pores with low microbial activity, but facilitating O2

Characteristics of soil water retention curve at macro-scale

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

Scale adaptable hydrological models have attracted more and more attentions in the hydrological modeling research community, and the constitutive relationship at the macro-scale is one of the most important issues, upon which there are not enough research activities yet. Taking the constitutive relationships of soil water movement--soil water retention curve (SWRC) as an example, this study extends the definition of SWRC at the micro-scale to that at the macro-scale, and aided by Monte Carlo method we demonstrate that soil property and the spatial distribution of soil moisture will affect the features of SWRC greatly. Furthermore, we assume that the spatial distribution of soil moisture is the result of self-organization of climate, soil, ground water and soil water movement under the specific boundary conditions, and we also carry out numerical experiments of soil water movement at the vertical direction in order to explore the relationship between SWRC at the macro-scale and the combinations of climate, soil, and groundwater. The results show that SWRCs at the macro-scale and micro-scale presents totally different features, e.g., the essential hysteresis phenomenon which is exaggerated with increasing aridity index and rising groundwater table. Soil property plays an important role in the shape of SWRC which will even lead to a rectangular shape under drier conditions, and power function form of SWRC widely adopted in hydrological model might be revised for most situations at the macro-scale.

Biological soil attributes in oilseed crops irrigated with oilfield produced water in the semi-arid region

Directory of Open Access Journals (Sweden)

Ana Clarice Melo Azevedo de Meneses

Full Text Available ABSTRACT Wastewater from oil is the main residue of the oil industry. Studies have shown that wastewater, or produced water, can be treated and used as an alternative source for the irrigation of oilseed crops. The aim of this work was to evaluate the effect of treated produced water on the biological properties of soil cultivated with the castor bean cv. BRS Energy and the sunflower cv. BRS 321 respectively, for two and three successive cycles of grain production. The first cycle in the sunflower and castor bean corresponds to the dry season and the second cycle to the rainy season. The third crop cycle in the sunflower relates to the dry season. The research was carried out from August 2012 to October 2013, in the town of Aracati, in the State of Ceará (Brazil, where both crops were submitted to irrigation with filtered produced water (FPW, produced water treated by reverse osmosis (OPW, or groundwater water from the Açu aquifer (ACW, and to no irrigation (RFD. The treatments, with three replications, were evaluated during the periods of pre-cultivation and plant reproduction for soil respiration (Rs, total organic carbon (TOC and the population density of bacteria (Bact and filamentous fungi (Fung in the soil. In the sunflower crop, these soil attributes are sensitive to the irrigation water used. Irrigation of the castor bean affects soil respiration. Under the conditions of this study, irrigation with FPW may be a short-term alternative in the castor bean and sunflower crops.

Monitoring changes in soil water content on adjustable soil slopes of a soil column using time domain reflectometry (TDR) techniques

International Nuclear Information System (INIS)

Wan Zakaria Wan Muhd Tahir; Lakam Anak Mejus; Johari Abdul Latif

2004-01-01

Time Domain Reflectometry (TDR) is one of non-destructive methods and widely used in hydrology and soil science for accurate and flexible measurement of soil water content The TDR technique is based on measuring the dielectric constant of soil from the propagation of an electromagnetic pulse traveling along installed probe rods (parallel wire transmission line). An adjustable soil column i.e., 80 cm (L) x 35 cm (H) x 44 cm (W) instrumented with six pairs of vertically installed CS615 reflectometer probes (TDR rods) was developed and wetted under a laboratory simulated rainfall and their sub-surface moisture variations as the slope changes were monitored using TDR method Soil samples for gravimetric determination of water content, converted to a volume basis were taken at selected times and locations after the final TDR reading for every slope change made of the soil column Comparisons of water contents by TDR with those from grawmetric samples at different slopes of soil column were examined. The accuracy was found to be comparable and to some extent dependent upon the variability of the soil. This study also suggests that the response of slope (above 20 degrees) to the gradual increase in water content profile may cause soil saturation faster and increased overland flow (runoff especially on weak soil conditions

Soil variability and effectiveness of soil and water conservation in the Sahel.

NARCIS (Netherlands)

Hien, F.G.; Rietkerk, M.; Stroosnijder, L.

1997-01-01

Sahelian sylvopastoral lands often degrade into bare and crusted areas where regeneration of soil and vegetation is impossible in the short term unless soil and water conservation measures are implemented. Five combinations of tillage with and without mulch on three crust type/soil type combinations

Soil water repellency of the artificial soil and natural soil in rocky slopes as affected by the drought stress and polyacrylamide.

Science.gov (United States)

Chen, Zhang; Wang, Ruixin; Han, Pengyuan; Sun, Hailong; Sun, Haifeng; Li, Chengjun; Yang, Lixia

2018-04-01

Soil water repellency (SWR) causes reduced soil water storage, enhanced runoff and reduced ecosystem productivity. Therefore, characterization of SWR is a prerequisite for effective environmental management. SWR has been reported under different soils, land uses and regions of the world, particularly in forest land and after wildfires; however, the understanding of this variable in the artificial soil of rocky slope eco-engineering is still rather limited. This study presented the characterization of SWR in the artificial soil affected by the polyacrylamide (PAM) and drought stress. There were two molecular weights of PAM, and the CK was without PAM application. Three types of soil were studied: natural soil and two types of artificial soil which have been sprayed for 1y and 5y, respectively. The drought stress experiments had three drought gradients, lasted for three weeks. Water repellency index (WRI) and soil-water contact angle (β) were determined using intrinsic sorptivity method by measuring the water sorptivity (S W ) and ethanol sorptivity (S E ) in all soil samples. The results showed that (1) Polyacrylamide treatments significantly increased S W by 3% to 38%, and reduced S E by 1% to 15%, WRI by 6% to 38%, β by 3% to 23% compared to the control group. Polyacrylamide treatments also increased water-stable aggregates content and total porosity by 22% to 33%, 11% to 20% relative to the control, while PAM with a higher molecular weight performed best. (2) The interaction between PAM and drought stress had a significant effect on WRI and β for all soil types (Pnatural soil. Copyright © 2017 Elsevier B.V. All rights reserved.

Soil water content plays an important role in soil-atmosphere exchange of carbonyl sulfide (OCS)

Science.gov (United States)

Yi, Zhigang; Behrendt, Thomas; Bunk, Rüdiger; Wu, Dianming; Kesselmeier, Jürgen

2016-04-01

Carbonyl sulfide (OCS) is a quite stable gas in the troposphere and is transported up to the stratosphere, where it contributes to the sulfate aerosol layer (Crutzen 1976). The tropospheric concentration seems to be quite constant, indicating a balance between sinks and sources. Recent work by Sandoval-Soto et al. (2005) demonstrated the enormous strength of the vegetation sink and the urgent needs to understand the sinks and sources. The role of soils is a matter of discussion (Kesselmeier et al., 1999; Van Diest and Kesselmeier, 2008; Maseyk et al., 2014; Whelan et al., 2015). To better understand the influence of soil water content and OCS mixing ratio on OCS fluxes, we used an OCS analyzer (LGR COS/CO Analyzer 907-0028, Los Gatos, CA, USA) coupled with automated soil chamber system (Behrendt et al., 2014) to measure the OCS fluxes with a slow drying of four different types of soil (arable wheat soil in Mainz, blueberry soil in Waldstein, spruce soil in Waldstein and needle forest soil in Finland). Results showed that OCS fluxes as well as the optimum soil water content for OCS uptake varied significantly for different soils. The net production rates changed significantly with the soil drying out from 100% to about 5% water holding capacity (WHC), implying that soil water content play an important role in the uptake processes. The production and uptake processes were distinguished by the regression of OCS fluxes under different OCS mixing ratios. OCS compensation points (CP) were found to differ significantly for different soil types and water content, with the lowest CP at about 20% WHC, implying that when estimating the global budgets of OCS, especially for soils fluxes, soil water content should be taken into serious consideration. References Crutzen, P. J. 1976, Geophys. Res. Lett., 3, 73-76. Sandoval-Soto, L. et al., 2005, Biogeosciences, 2, 125-132. Kesselmeier, J. et al., 1999, J. Geophys. Res., 104, 11577-11584. Van Diest, H. and Kesselmeier, J. 2008

Soil density and moisture content on two unused forest roads during first 30 months after construction

Science.gov (United States)

J.D. Helvey; J.N. Kochenderfer; J.N. Kochenderfer

1990-01-01

Reports results of soil density and soil moisture measurements on two roads in the central Appalachians over a 30-month period. Density increased slightly during the measurement period at most locations. Almost all of the density changes occurred during the first few months after construction. Moisture content decreased during the first few months after construction,...

The dependence of water potential in shoots of Picea abies on air and soil water status

Directory of Open Access Journals (Sweden)

A. Sellin

Full Text Available Where there is sufficient water storage in the soil the water potential (Ψx in shoots of Norway spruce [Picea abies (L. Karst.] is strongly governed by the vapour pressure deficit of the atmosphere, while the mean minimum values of Ψx usually do not drop below –1.5 MPa under meteorological conditions in Estonia. If the base water potential (Ψb is above –0.62 MPa, the principal factor causing water deficiency in shoots of P. abies may be either limited soil water reserves or atmospheric evaporative demand depending on the current level of the vapour pressure deficit. As the soil dries the stomatal control becomes more efficient in preventing water losses from the foliage, and the leaf water status, in turn, less sensitive to atmospheric demand. Under drought conditions, if Ψb falls below –0.62 MPa, the trees' water stress is mainly caused by low soil water availability. Further declines in the shoot water potential (below –1.5 MPa can be attributed primarily to further decreases in the soil water, i.e. to the static water stress.Key words. Hydrology (evapotranspiration · plant ecology · soil moisture.

Water evaporation from bare soil at Paraiba, Brazil

International Nuclear Information System (INIS)

Lima, Jose Romualdo de Sousa; Antonino, Antonio Celso D.; Lira, Carlos A. Brayner de O.; Maciel Netto, Andre; Silva, Ivandro de Franca da; Souza, Jeffson Cavalcante de

2002-01-01

Measurements were accomplished in a 4,0 ha area in Centro de Ciencias Agrarias, UFPB, Areia City, Paraiba State, Brazil (6 deg C 58'S, 35 deg C 41'W and 645 m), aiming to determine water evaporation from bare soil, by energy and water balance approaches. Rain gauge, net radiometer, pyranometer and sensor for measuring the temperature and the relative humidity of the air and the speed of the wind, in two levels above the soil surface, were used to solve the energy balance equations. In the soil, two places were fitted with instruments, each one with two thermal probes, installed horizontally in the depths z1 = 2,0 cm and z2 = 8,0 cm, and a heat flux plate, for the measurement of the heat flux in the soil, the z1 = 5,0 cm. The measured data were stored every 30 minutes in a data logger. For the calculation of the water balance, three tensio-neutronics sites were installed, containing: an access tube for neutrons probe and eight tensiometers. The values of soil evaporation obtained by water balance were lower than obtained by energy balance because of the variability of the water balance terms. (author)

Soil and ground-water remediation techniques

International Nuclear Information System (INIS)

Beck, P.

1996-01-01

Urban areas typically contain numerous sites underlain by soils or ground waters which are contaminated to levels that exceed clean-up guidelines and are hazardous to public health. Contamination most commonly results from the disposal, careless use and spillage of chemicals, or the historic importation of contaminated fill onto properties undergoing redevelopment. Contaminants of concern in soil and ground water include: inorganic chemicals such as heavy metals; radioactive metals; salt and inorganic pesticides, and a range of organic chemicals included within petroleum fuels, coal tar products, PCB oils, chlorinated solvents, and pesticides. Dealing with contaminated sites is a major problem affecting all urban areas and a wide range of different remedial technologies are available. This chapter reviews the more commonly used methods for ground-water and soil remediation, paying particular regard to efficiency and applicability of specific treatments to different site conditions. (author). 43 refs., 1 tab., 27 figs

Evaluation of a simulation model for predicting soil-water ...

African Journals Online (AJOL)

The soils particle size distribution (specifically, percent clay and sand) and organic matter contents were inputted into the model to simulate soil moisture status at saturation, field capacity and wilting point, soil bulk density and saturated hydraulic conductivity. The model outputs were statistically compared with observed ...

Water infiltration into homogeneous soils: a new concept

International Nuclear Information System (INIS)

Manfredni, S.

1977-10-01

A new concept for the analytical description of the process of water infiltration into homogeneous soils is presented. The concept uses a new definition of a 'gravitational diffusivity' which permits the generalization of both cases, horizontal and vertical infiltration. The efficiency of the new concept in describing the infiltration process, for short and intermediate times, is proved through experimental data obtained during water infiltration into air-dry soil columns. Its advantages are discussed comparing soil water contents predicted by the numerical solution proposed by PHILLIP (1955, 1957) [pt

Validation of a spatial–temporal soil water movement and plant water uptake model

KAUST Repository

HEPPELL, J.; PAYVANDI, S.; ZYGALAKIS, K.C.; SMETHURST, J.; FLIEGE, J.; ROOSE, T.

2014-01-01

© 2014, (publisher). All rights reserved. Management and irrigation of plants increasingly relies on accurate mathematical models for the movement of water within unsaturated soils. Current models often use values for water content and soil

Water repellent soils: a state-of-the-art

Science.gov (United States)

Leonard F. DeBano

1981-01-01

Water repellency in soils was first described by Schreiner and Shorey (1910), who found that some soils in California could not be wetted and thereby were not suitable for agriculture. Waxy organic substances were responsible for the water repellency. Other studies in the early 1900's on the fairy ring phenomenon suggested that water repellency could be caused by...

Predictions of soil-water potentials in the north-western Sonoran Desert

Energy Technology Data Exchange (ETDEWEB)

Young, D.R.; Nobel, P.S.

1986-03-01

A simple computer model was developed to predict soil-water potential at a Sonoran Desert site. The variability of precipitation there, coupled with the low water-holding capacity of the sandy soil, result in large temporal and spatial variations in soil-water potential. Predicted soil-water potentials for depths of 5, 10 and 20 cm were in close agreement with measured values as the soil dried after an application of water. Predicted values at a depth of 10 cm, the mean rooting depth of Agave deserti and other succulents common at the study site, also agreed with soil-water potentials measured in the field throughout 1 year. Both soil-water potential and evaporation from the soil surface were very sensitive to simulated changes in the hydraulic conductivity of the soil. The annual duration of soil moisture adequate for succulents was dependent on the rainfall as well as on the spacing and amount of individual rainfalls. The portion of annual precipitation evaporated from the soil surface varied from 73% in a dry year (77 mm precipitation) to 59% in a wet year (597 mm). Besides using the actual precipitation events, simulations were performed using the figures for total monthly precipitation. Based on the average number of rainfalls for a particular month, the rainfall was distributed throughout the month in the model. Predictions using both daily and monthly inputs were in close agreement, especially for the number of days during a year when the soil-water potential was sufficient for water absorption by the succulent plants (above -0.5 MPa).

Model development for prediction of soil water dynamics in plant production.

Science.gov (United States)

Hu, Zhengfeng; Jin, Huixia; Zhang, Kefeng

2015-09-01

Optimizing water use in agriculture and medicinal plants is crucially important worldwide. Soil sensor-controlled irrigation systems are increasingly becoming available. However it is questionable whether irrigation scheduling based on soil measurements in the top soil could make best use of water for deep-rooted crops. In this study a mechanistic model was employed to investigate water extraction by a deep-rooted cabbage crop from the soil profile throughout crop growth. The model accounts all key processes governing water dynamics in the soil-plant-atmosphere system. Results show that the subsoil provides a significant proportion of the seasonal transpiration, about a third of water transpired over the whole growing season. This suggests that soil water in the entire root zone should be taken into consideration in irrigation scheduling, and for sensor-controlled irrigation systems sensors in the subsoil are essential for detecting soil water status for deep-rooted crops.

Estimation of areal soil water content through microwave remote sensing

NARCIS (Netherlands)

Oevelen, van P.J.

2000-01-01

In this thesis the use of microwave remote sensing to estimate soil water content is investigated. A general framework is described which is applicable to both passive and active microwave remote sensing of soil water content. The various steps necessary to estimate areal soil water content

Impacts of water erosion on soil physical properties of an Oxisol and an Inceptisol in the Eastern Plains of Colombia

International Nuclear Information System (INIS)

Obando, Franco H

1999-01-01

On the basis of soil losses records during 10 years, three levels of water erosion were established for two soil (Typical Hapludox and Oxic Dystropept) located on high and medium terraces of alluvial flat plain of piedmont in the Eastern Plains in La Libertad Research Center of CORPOICA. Eighteen 3 x 10 m 2 run-off plots were fitted out on a nonrandom arrangement of nine plots by landscape and three soil use and management treatments: zero grazing Brachiaria decumbens pasture for six years, up land rice, soybean and maize rotations for six years and bare soil for 10 years. Soil losses under these treatments allowed to define three degrees of erosion: slight (N 3 moderate (N 2 ) and severe (N 3 ) respectively. From each plot soil samples were taken at two depths for physical analyses. infiltration and resistance to cone penetration were measured in the field. Without exception water erosion produced a detrimental effect on soil physical properties and the hydrological function of both experimental soils. Water retention capacity for N 2 and N 3 erosion levels did not present significant differences. Weighed mean diameter, DPM, of water stable aggregates was significantly greater on in the slightly (N 1 ) erosion level. Bulk density presented values significantly higher at 0-1 cm depth on both a soils

Effect of inoculum density and soil tillage on the development and severity of rhizoctonia root rot.

Science.gov (United States)

Schroeder, K L; Paulitz, T C

2008-03-01

Rhizoctonia spp. cause substantial yield losses in direct-seeded cereal crops compared with conventional tillage. To investigate the mechanisms behind this increased disease, soils from tilled or direct-seeded fields were inoculated with Rhizoctonia spp. at population densities from 0.8 to 250 propagules per gram and planted with barley (Hordeum vulgare). The incidence and severity of disease did not differ between soils with different tillage histories. Both R. solani AG-8 and R. oryzae stunted plants at high inoculum densities, with the latter causing pre-emergence damping-off. High inoculum densities of both species stimulated early production of crown roots in barley seedlings. Intact soil cores from these same tilled and direct-seeded fields were used to evaluate the growth of Rhizoctonia spp. from colonized oat seeds. Growth of R. oryzae was not affected by previous tillage history. However, R. solani AG-8 grew more rapidly through soil from a long-term direct-seeded field compared to tilled soils. The differential response between these two experiments (mixed, homogenized soil versus intact soil) suggests that soil structure plays a major role in the proliferation of R. solani AG-8 through soils with different tillage histories.

A simplified Excel® algorithm for estimating the least limiting water range of soils

Directory of Open Access Journals (Sweden)

Leão Tairone Paiva

2004-01-01

Full Text Available The least limiting water range (LLWR of soils has been employed as a methodological approach for evaluation of soil physical quality in different agricultural systems, including forestry, grasslands and major crops. However, the absence of a simplified methodology for the quantification of LLWR has hampered the popularization of its use among researchers and soil managers. Taking this into account this work has the objective of proposing and describing a simplified algorithm developed in Excel® software for quantification of the LLWR, including the calculation of the critical bulk density, at which the LLWR becomes zero. Despite the simplicity of the procedures and numerical techniques of optimization used, the nonlinear regression produced reliable results when compared to those found in the literature.

Uranium in soils and water; Uran in Boden und Wasser

Energy Technology Data Exchange (ETDEWEB)

Dienemann, Claudia; Utermann, Jens

2012-07-15

The report of the Umweltbundesamt (Federal Environmental Agency) on uranium in soils and water covers the following chapters: (1) Introduction. (2) Deposits and properties: Use of uranium; toxic effects on human beings, uranium in ground water and drinking water, uranium in surface waters, uranium in soils, uranium in the air. (3) Legal regulations. (4) Uranium deposits, uranium mining, polluted area recultivation. (5) Diffuse uranium entry in soils and water: uranium insertion due to fertilizers, uranium insertion due to atmospheric precipitation, uranium insertion from the air. (6) Diffuse uranium release from soils and transfer in to the food chain. (7) Conclusions and recommendations.

Water Erosion in Different Slope Lengths on Bare Soil

Directory of Open Access Journals (Sweden)

Bárbara Bagio

Full Text Available ABSTRACT Water erosion degrades the soil and contaminates the environment, and one influential factor on erosion is slope length. The aim of this study was to quantify losses of soil (SL and water (WL in a Humic Cambisol in a field experiment under natural rainfall conditions from July 4, 2014 to June 18, 2015 in individual events of 41 erosive rains in the Southern Plateau of Santa Catarina and to estimate soil losses through the USLE and RUSLE models. The treatments consisted of slope lengths of 11, 22, 33, and 44 m, with an average degree of slope of 8 %, on bare and uncropped soil that had been cultivated with corn prior to the study. At the end of the corn cycle, the stalk residue was removed from the surface, leaving the roots of the crop in the soil. Soil loss by water erosion is related linearly and positively to the increase in slope length in the span between 11 and 44 m. Soil losses were related to water losses and the Erosivity Index (EI30, while water losses were related to rain depth. Soil losses estimated by the USLE and RUSLE model showed lower values than the values observed experimentally in the field, especially the values estimated by the USLE. The values of factor L calculated for slope length of 11, 22, 33, and 44 m for the two versions (USLE and RUSLE of the soil loss prediction model showed satisfactory results in relation to the values of soil losses observed.

Soil water content, runoff and soil loss prediction in a small ungauged agricultural basin in the Mediterranean region using the Soil and Water Assessment Tool

OpenAIRE

Ramos Martín, Ma. C. (Ma. Concepción); Martínez Casasnovas, José Antonio

2015-01-01

The aim of the present work was to evaluate the possibilities of using sub-basin data for calibration of the Soil and Water Assessment Tool (SWAT) model in a small (46 ha) ungauged basin (i.e. where the water flow is not systematically measured) and its response. This small basin was located in the viticultural Anoia-Penedès region (North-east Spain), which suffers severe soil erosion. The data sources were: daily weather data from an observatory located close to the basin; a detailed soil ma...

Measured soil water concentrations of cadmium and zinc in plant pots and estimated leaching outflows from contaminated soils

DEFF Research Database (Denmark)

Holm, P.E.; Christensen, T.H.

1998-01-01

Soil water concentrations of cadmium and zinc were measured in plant pots with 15 contaminated soils which differed in origin, texture, pH (5.1-7.8) and concentrations of cadmium (0.2-17 mg Cd kg(-1)) and zinc (36-1300 mg Zn kg(-1)). The soil waters contained total concentrations of 0.5 to 17 mu g...... to 0.1% per year of the total soil content of cadmium and zinc. The measured soil water concentrations of cadmium and zinc did not correlate linearly with the corresponding soil concentrations but correlated fairly well with concentrations measured in Ca(NO(3))(2) extracts of the soils and with soil...... water concentrations estimated from soil concentrations and pH. Such concentration estimates may be useful for estimating amounts of cadmium and zinc being leached from soils....

Evaluation of different field methods for measuring soil water infiltration

Science.gov (United States)

Pla-Sentís, Ildefonso; Fonseca, Francisco

2010-05-01

Soil infiltrability, together with rainfall characteristics, is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the direct measurement of water infiltration rates or its indirect deduction from other soil characteristics or properties has become indispensable for the evaluation and modelling of the previously mentioned processes. Indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, have demonstrated to be of limited value in most of the cases. Direct "in situ" field evaluations have to be preferred in any case. In this contribution we present the results of past experiences in the measurement of soil water infiltration rates in many different soils and land conditions, and their use for deducing soil water balances under variable climates. There are also presented and discussed recent results obtained in comparing different methods, using double and single ring infiltrometers, rainfall simulators, and disc permeameters, of different sizes, in soils with very contrasting surface and profile characteristics and conditions, including stony soils and very sloping lands. It is concluded that there are not methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the surface

A one-dimensional model for simulating soil water movement ...

African Journals Online (AJOL)

... regression analysis revealed the relati-onship to be exponential. The values of calculated and measured soil water content and total evapotranspiration decreased with number of days after rain or irrigation. The nodal soil water content also decreased with the soil depth. (Journal of Applied Science and Technology: 2001 ...

The impact of agriculture terraces on soil organic matter, aggregate stability, water repellency and bulk density. A study in abandoned and active farms in the Sierra de Enguera, Eastern Spain.

Science.gov (United States)

Cerdà, Artemi; Burguet, Maria; Keesstra, Saskia; Prosdocimi, Massimo; Di Prima, Simone; Brevik, Erik; Novara, Agata; Jordan, Antonio; Tarolli, Paolo

2016-04-01

Soil erosion, land degradation, lack of organic matter, erodible soils, rock outcrops… are a consequence of the human abuse and misuse of the soil resources. And this is a worldwide environmental issue (Novara et al., 2011; Vanlauwe et al., 2015; Musinguzi et al., 2015; Pereira et al., 2015; Mwagno et al., 2016). Agriculture terraces are a strategy to reduce the soil erosion, improve the soil fertility and allow the ploughing (Cerdà et al., 2010; Li et al., 2014). Although this idea is well accepted there are few scientific evidences that demonstrate that soils in the terraced areas are more stable, fertile and sustainable that the soil in non terraced areas. In fact, the ploughing in comparison to the abandoned or not ploughed land results in the soil degradation (Lieskovský and Kenderessy, 2014; Gao et al., 2015; Parras-Alcántara et al., 2014). This is mainly due to the lack of vegetation that increase the surface runoff (Cerdà et al., 1998; Keesstra et al., 2007). And why is necessary to develop also in terraced landscapes soil erosion control strategies (Mekonnen et al., 2015a; Mekonnen et al., 2015b; Prosdocimi et al., 2016). Our objective was to assess the soil organic matter content (Walkley and Black, 1934), the soil bulk density (ring method), the aggregate stabilility (drop impact) and the water repellency (Water Drop Penetration Time test) in four study sites in the Sierra de Enguera. Two sites were terraced: one abandoned 40 years before the measurements and the other still active with olive crops. And two control sites non-terraced. We used the paired plot strategy to compare the impact of terracing and abandonment. At each site we collected randomly 50 soil samples at 0-2 cm, 4-6 and 8-10 cm depth. At each sampling point 100 WDPT measurements where carried out, and one sample for the bulk density, and one for the organic matter, and one for the soil aggregate stability were collected. The soil surface samples shown the largest differences. The

Linking air and water transport in intact soils to macro-porosity by combining laboratory measurements and X-ray Computed Tomography

DEFF Research Database (Denmark)

Katuwal, Sheela; Norgaard, Trine; Møldrup, Per

-porosity (R2 = 0.80 for air permeability: R2= 0.61 for 5% arrival time) and macro-porosity of the restricting layer (R2=0.83 for air permeability: R2= 0.71 for 5% arrival time) over air-filled porosity and all the correlations were positive. The high positive correlation these air and water transport...... functions with macro-porosity stressed the importance of continuity and tortuosity of pores in air, water and solute flow and transport through the soils. Negative correlations of air permeability, 5% arrival time of tracer and macro-porosity were obtained with bulk density whereas with other soil physical......With an objective to link the hydraulic properties of soil with the soil structural properties, air permeability and 5% arrival time of a conservative tracer was measured for large undisturbed soil columns from the same agricultural field. The same soil columns were scanned with a medical scanner...

Assessment of produced water contaminated soils to determine remediation requirements

International Nuclear Information System (INIS)

Clodfelter, C.

1995-01-01

Produced water and drilling fluids can impact the agricultural properties of soil and result in potential regulatory and legal liabilities. Produced water typically is classified as saline or a brine and affects surface soils by increasing the sodium and chloride content. Sources of produced water which can lead to problems include spills from flowlines and tank batteries, permitted surface water discharges and pit areas, particularly the larger pits including reserve pits, emergency pits and saltwater disposal pits. Methods to assess produced water spills include soil sampling with various chemical analyses and surface geophysical methods. A variety of laboratory analytical methods are available for soil assessment which include electrical conductivity, sodium adsorption ratio, cation exchange capacity, exchangeable sodium percent and others. Limiting the list of analytical parameters to reduce cost and still obtain the data necessary to assess the extent of contamination and determine remediation requirements can be difficult. The advantage to using analytical techniques is that often regulatory remediation standards are tied to soil properties determined from laboratory analysis. Surface geophysical techniques can be an inexpensive method to rapidly determine the extent and relative magnitude of saline soils. Data interpretations can also provide an indication of the horizontal as well as the vertical extent of impacted soils. The following discussion focuses on produced water spills on soil and assessment of the impacted soil. Produced water typically contains dissolved hydrocarbons which are not addressed in this discussion

Effects of pH-Induced Changes in Soil Physical Characteristics on the Development of Soil Water Erosion

Directory of Open Access Journals (Sweden)

Shinji Matsumoto

2018-04-01

Full Text Available Soil water erosion is frequently reported as serious problem in soils in Southeast Asia with tropical climates, and the variations in pH affect the development of the erosion. This study investigated the effects of changes in pH on soil water erosion based on changes in the physical properties of the simulated soils with pH adjusted from 2.0 to 10.0 through artificial rainfall tests. The zeta potential was entirely shifted to positive direction at each pH condition due to Al, Ca, and Mg. In the pH range of 6.0 to 2.0, the aggregation of soil particles resulting from the release of Al3+ from clay minerals and/or molecular attraction between soil particles caused the plastic index (IP of the soil to decrease. The decrease in IP led to the development of soil water erosion at the pH range. When the pH exceeded 6.0, the repulsive force generated by the negative charges on soil particles decreased IP, resulting in accelerated erosion by water. The results suggest that changes in pH causes physical properties of the soil to change through changes of the zeta potential in the clayey soil rich in Al, Ca, and Mg, leading to the development of soil water erosion.

Evaluation of soil conservation technologies from the perspective of selected physical soil properties and infiltration capacity of the soil

Directory of Open Access Journals (Sweden)

Miroslav Dumbrovský

2011-01-01

Full Text Available This paper evaluates different technologies of soil cultivation (conventional and minimization in terms of physical properties and water regime of soils, where infiltration of surface water is a major component of subsurface water. Soil physical properties (the current humidity, reduced bulk density, porosity, water retention capacity of soil, pore distribution and soil aeration is determined from soil samples taken from the organic horizon according to standard methodology. To observe the infiltration characteristics of surface layers of topsoil, the drench method (double ring infiltrometers was used. For the evaluation of field measurements of infiltration, empirical and physically derived equations by Kostiakov and Philip and the three-parameter Philip-type equation were used. The Philip three-parameter equation provides physical based parameters near the theoretical values, a good estimation of saturated hydraulic conductivity Ks and sorptivity C1. The parameter S of Philip’s equation describes the real value of the sorptivity of the soil. Experimental research work on the experimental plots H. Meziříčko proceeded in the years 2005–2008.

Development of construction materials like concrete from lunar soils without water

Science.gov (United States)

Desai, Chandra S.; Saadatmanesh, H.; Frantziskonis, G.

1989-01-01

The development of construction materials such as concrete from lunar soils without the use of water requires a different methodology than that used for conventional terrestrial concrete. A unique approach is attempted that utilizes factors such as initial vacuum and then cyclic loading to enhance the mechanical properties of dry materials similar to those available on the moon. The application of such factors is expected to allow reorientation, and coming together, of particles of the materials toward the maximum theoretical density. If such a density can provide deformation and strength properties for even a limited type of construction, the approach can have significant application potential, although other factors such as heat and chemicals may be needed for specific construction objectives.

Impacts of fresh and aged biochars on plant available water and water use efficiency

Science.gov (United States)

The ability of soils to hold sufficient plant available water (PAW) between rainfall events is critical to crop productivity. Most studies indicate that biochar amendments decrease soil bulk density and increase soil water retention. However, limited knowledge exists regarding biochars ability to in...

Soil CO2 Dynamics in a Tree Island Soil of the Pantanal: The Role of Soil Water Potential

Science.gov (United States)

Johnson, Mark S.; Couto, Eduardo Guimarães; Pinto Jr, Osvaldo B.; Milesi, Juliana; Santos Amorim, Ricardo S.; Messias, Indira A. M.; Biudes, Marcelo Sacardi

2013-01-01

The Pantanal is a biodiversity hotspot comprised of a mosaic of landforms that differ in vegetative assemblages and flooding dynamics. Tree islands provide refuge for terrestrial fauna during the flooding period and are particularly important to the regional ecosystem structure. Little soil CO2 research has been conducted in this region. We evaluated soil CO2 dynamics in relation to primary controlling environmental parameters (soil temperature and soil water). Soil respiration was computed using the gradient method using in situ infrared gas analyzers to directly measure CO2 concentration within the soil profile. Due to the cost of the sensors and associated equipment, this study was unreplicated. Rather, we focus on the temporal relationships between soil CO2 efflux and related environmental parameters. Soil CO2 efflux during the study averaged 3.53 µmol CO2 m−2 s−1, and was equivalent to an annual soil respiration of 1220 g C m−2 y−1. This efflux value, integrated over a year, is comparable to soil C stocks for 0–20 cm. Soil water potential was the measured parameter most strongly associated with soil CO2 concentrations, with high CO2 values observed only once soil water potential at the 10 cm depth approached zero. This relationship was exhibited across a spectrum of timescales and was found to be significant at a daily timescale across all seasons using conditional nonparametric spectral Granger causality analysis. Hydrology plays a significant role in controlling CO2 efflux from the tree island soil, with soil CO2 dynamics differing by wetting mechanism. During the wet-up period, direct precipitation infiltrates soil from above and results in pulses of CO2 efflux from soil. The annual flood arrives later, and saturates soil from below. While CO2 concentrations in soil grew very high under both wetting mechanisms, the change in soil CO2 efflux was only significant when soils were wet from above. PMID:23762259

Natural and fire-induced soil water repellency in a Portugese Shrubland

NARCIS (Netherlands)

Stoof, C.R.; Moore, D.; Ritsema, C.J.; Dekker, L.W.

2011-01-01

Post-fire land degradation is often attributed to fire-induced soil water repellency, despite the fact that soil water repellency is a natural phenomenon in many soils and is therefore not necessarily caused by fire. To improve our understanding of the role of soil water repellency in causing

[Soil infiltration of snowmelt water in the southern Gurbantunggut Desert, Xinjiang, China].

Science.gov (United States)

Hu, Shun-jun; Chen, Yong-bao; Zhu, Hai

2015-04-01

Soil infiltration of snow-melt water is an important income item of water balance in arid desert. The soil water content in west slope, east slope and interdune of sand dune in the southern Gurbantunggut Desert was monitored before snowfall and after snow melting during the winters of 2012-2013 and 2013-2014. According to the principle of water balance, soil infiltration of snow-melt in the west slope, east slope, interdune and landscape scale was calculated, and compared with the results measured by cylinder method. The results showed that the soil moisture recharge from unfrozen layer of unsaturated soil to surface frozen soil was negligible because the soil moisture content before snowfall was lower, soil infiltration of snow-melt water was the main source of soil water of shallow soil, phreatic water did not evaporate during freezing period, and did not get recharge after the snow melting. Snowmelt water in the west slope, east slope, interdune and landscape scale were 20-43, 27-43, 32-45, 26-45 mm, respectively.

Effect of top soil wettability on water evaporation and plant growth.

Science.gov (United States)

Gupta, Bharat; Shah, D O; Mishra, Brijesh; Joshi, P A; Gandhi, Vimal G; Fougat, R S

2015-07-01

In general, agricultural soil surfaces being hydrophilic in nature get easily wetted by water. The water beneath the soil moves through capillary effect and comes to the surface of the soil and thereafter evaporates into the surrounding air due to atmospheric conditions such as sunlight, wind current, temperature and relative humidity. To lower the water loss from soil, an experiment was designed in which a layer of hydrophobic soil was laid on the surface of ordinary hydrophilic soil. This technique strikingly decreased loss of water from the soil. The results indicated that the evaporation rate significantly decreased and 90% of water was retained in the soil in 83 h by the hydrophobic layer of 2 cm thickness. A theoretical calculation based on diffusion of water vapour (gas phase) through hydrophobic capillaries provide a meaningful explanation of experimental results. A greater retention of water in the soil by this approach can promote the growth of plants, which was confirmed by growing chick pea (Cicer arietinum) plants and it was found that the length of roots, height of shoot, number of branches, number of leaves, number of secondary roots, biomass etc. were significantly increased upon covering the surface with hydrophobic soil in comparison to uncovered ordinary hydrophilic soil of identical depth. Such approach can also decrease the water consumption by the plants particularly grown indoors in residential premises, green houses and poly-houses etc. and also can be very useful to prevent water loss and enhance growth of vegetation in semi-arid regions. Copyright © 2015 Elsevier Inc. All rights reserved.

Grey water impact on soil physical properties

Directory of Open Access Journals (Sweden)

Miguel L. Murcia-Sarmiento

2014-01-01

Full Text Available Due to the increasing demand for food produced by the increase in population, water as an indispensable element in the growth cycle of plants every day becomes a fundamental aspect of production. The demand for the use of this resource is necessary to search for alternatives that should be evaluated to avoid potential negative impacts. In this paper, the changes in some physical properties of soil irrigated with synthetic gray water were evaluated. The experimental design involved: one factor: home water and two treatments; without treated water (T1 and treated water (T2. The variables to consider in the soil were: electrical conductivity (EC, exchangeable sodium percentage (ESP, average weighted diameter (MWD and soil moisture retention (RHS. The water used in drip irrigation high frequency was monitored by tensiometer for producing a bean crop (Phaseolous vulgaris L. As filtration system used was employed a unit composed of a sand filter (FLA and a subsurface flow wetland artificial (HFSS. The treatments showed significant differences in the PSI and the RHS. The FLA+HFSS system is an alternative to the gray water treatment due to increased sodium retention.

Squeezed Interstitial Water and Soil Properties in Pleistocene Blue Clays under Different Natural Environments

Directory of Open Access Journals (Sweden)

Maria Dolores Fidelibus

2018-03-01

Full Text Available Studies dating almost a century relate clay properties with the structure of the diffuse double layer (DDL, where the charged surfaces of clay crystal behave like an electric capacitor, whose dielectric is the interstitial fluid. The intensity of the inner electric field relates to the concentration and type of ions in the DDL. Other important implications of the model are less stressed: this part of the clay soil system, energetically speaking, is conservative. External contribution of energy, work of overburden or sun driven capillarity and long exposure to border low salinity waters can modify the concentration of pore-waters, thus affecting the DDL geometry, with electric field and energy storage variations. The study of clay soils coming from various natural geomorphological and hydrogeological contexts, determining a different salinity of interacting groundwater, shows how the clay interaction with freely circulating waters at the boundaries produces alterations in the native pore water salinity, and, at the nano-scale, variations of electric field and stored energy from external work. The swelling and the shrinkage of clay soil with their volumetric and geotechnical implications should be regarded as variations of the electrostatic and mechanical energy of the system. The study is based on tests on natural clay soil samples coming from a formation of stiff blue clays, widespread in southern Italy. Geotechnical identification and oedometer tests have been performed, and pore waters squeezed out from the specimens have been analyzed. Tested samples have similar grain size, clay fraction and plasticity; sorted according to the classified geomorphological/hydrogeological contexts, they highlight good correlations among dry density, mechanical work performed in selected stages of the oedometric test, swelling and non-swelling behaviour, and electrical conductivity of the squeezed pore waters. The work performed for swelling and non

Effect of soil properties on Hydraulic characteristics under subsurface drip irrigation

Science.gov (United States)

Fan, Wangtao; Li, Gang

2018-02-01

Subsurface drip irrigation (SDI) is a technique that has a high potential in application because of its high efficiency in water-saving. The hydraulic characteristics of SDI sub-unit pipe network can be affected by soil physical properties as the emitters are buried in soils. The related research, however, is not fully explored. The laboratory tests were carried out in the present study to determine the effects of hydraulic factors including operating pressure, initial soil water content, and bulk density on flow rate and its sensitivity to each hydraulic factor for two types of SDI emitters (PLASSIM emitter and Heping emitter). For this purpose, three soils with contrasting textures (i.e., light sand, silt loam, and light clay) were repacked with two soil bulk density (1.25 and1.40 g cm-3) with two initial soil water content (12% and 18%) in plexiglass columns with 40 cm in diameter and 40 cm in height. Drip emitters were buried at depth of 20 cm to measure the flow rates under seven operating pressures (60, 100, 150, 200, 250, 300, and 370 kPa). We found that the operating pressure was the dominating factor of flow rate of the SDI emitter, and flow rate increased with the increase of operating pressure. The initial soil water content and bulk density also affected the flow rate, and their effects were the most notable in the light sand soil. The sensitivity of flow rate to each hydraulic factor was dependent on soil texture, and followed a descending order of light sand>silt loam>light clay for both types of emitters. Further, the sensitivity of flow rate to each hydraulic factor decreased with the increase of operating pressure, initial soil water content, and bulk density. This study may be used to guide the soil specific-design of SDI emitters for optimal water use and management.

Density fractions versus size separates: does physical fractionation isolate functional soil compartments?

Directory of Open Access Journals (Sweden)

C. Moni

2012-12-01

Full Text Available Physical fractionation is a widely used methodology to study soil organic matter (SOM dynamics, but concerns have been raised that the available fractionation methods do not well describe functional SOM pools. In this study we explore whether physical fractionation techniques isolate soil compartments in a meaningful and functionally relevant way for the investigation of litter-derived nitrogen dynamics at the decadal timescale. We do so by performing aggregate density fractionation (ADF and particle size-density fractionation (PSDF on mineral soil samples from two European beech forests a decade after application of ¹⁵N labelled litter.

Both density and size-based fractionation methods suggested that litter-derived nitrogen became increasingly associated with the mineral phase as decomposition progressed, within aggregates and onto mineral surfaces. However, scientists investigating specific aspects of litter-derived nitrogen dynamics are pointed towards ADF when adsorption and aggregation processes are of interest, whereas PSDF is the superior tool to research the fate of particulate organic matter (POM.

Some methodological caveats were observed mainly for the PSDF procedure, the most important one being that fine fractions isolated after sonication can not be linked to any defined decomposition pathway or protective mechanism. This also implies that historical assumptions about the "adsorbed" state of carbon associated with fine fractions need to be re-evaluated. Finally, this work demonstrates that establishing a comprehensive picture of whole soil OM dynamics requires a combination of both methodologies and we offer a suggestion for an efficient combination of the density and size-based approaches.

Structure-Dependent Water-Induced Linear Reduction Model for Predicting Gas Diffusivity and Tortuosity in Repacked and Intact Soil

DEFF Research Database (Denmark)

Møldrup, Per; Chamindu, T. K. K. Deepagoda; Hamamoto, S.

2013-01-01

The soil-gas diffusion is a primary driver of transport, reactions, emissions, and uptake of vadose zone gases, including oxygen, greenhouse gases, fumigants, and spilled volatile organics. The soil-gas diffusion coefficient, Dp, depends not only on soil moisture content, texture, and compaction...... but also on the local-scale variability of these. Different predictive models have been developed to estimate Dp in intact and repacked soil, but clear guidelines for model choice at a given soil state are lacking. In this study, the water-induced linear reduction (WLR) model for repacked soil is made...... air) in repacked soils containing between 0 and 54% clay. With Cm = 2.1, the SWLR model on average gave excellent predictions for 290 intact soils, performing well across soil depths, textures, and compactions (dry bulk densities). The SWLR model generally outperformed similar, simple Dp/Do models...

Fluorescent probes for understanding soil water repellency: the novel application of a chemist's tool to soil science

Science.gov (United States)

Balshaw, Helen M.; Davies, Matthew L.; Doerr, Stefan H.; Douglas, Peter

2015-04-01

Food security and production is one of the key global issues faced by society. It has become essential to work the land efficiently, through better soil management and agronomy whilst protecting the environment from air and water pollution. The failure of soil to absorb water - soil water repellency can lead to major environmental problems such as increased overland flow and soil erosion, poor uptake of agricultural chemicals, and increased risk of groundwater pollution due to the rapid transfer of contaminants and nutrient leaching through uneven wetting and preferential flow pathways. Understanding the causes of soil hydrophobicity is essential for the development of effective methods for its amelioration, supporting environmental stability and food security. Organic compounds deposited on soil mineral or aggregate surfaces have long been recognised as a major factor in causing soil water repellency. It is widely accepted that the main groups of compounds responsible are long-chain acids, alkanes and other organic compounds with hydrophobic properties. However, when reapplied to sands and soils, the degree of water repellency induced by these compounds and mixtures varied widely with compound type, amount, and mixture, in a seemingly unpredictable way. Fluorescent and phosphorescent probes are widely used in chemistry and biochemistry due to their sensitive response to their physical and chemical environment, such as polarity, and viscosity. However, they have to-date not been used to study soil water repellency. Here we present preliminary work on the evaluation of fluorescent probes as tools to study two poorly understood features that determine the degree of wettability for water repellent soils: (i) the distribution of organics on soils; (ii) the changes in polarity at soil surfaces required for water drops to infiltrate. In our initial work we have examined probes adsorbed onto model soils, prepared by adsorption of specific organics onto acid washed sand

Estimating respiration of roots in soil: interactions with soil CO2, soil temperature and soil water content

NARCIS (Netherlands)

Bouma, T.J.; Nielsen, K.F.; Eissenstat, D.M.; Lynch, J.P.

1997-01-01

Little information is available on the variability of the dynamics of the actual and observed root respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil CO2 concentration, temperature, soil water content and root respiration, and II) the effect of

Differential controls on soil carbon density and mineralization among contrasting forest types in a temperate forest ecosystem

Science.gov (United States)

You, Ye-Ming; Wang, Juan; Sun, Xiao-Lu; Tang, Zuo-Xin; Zhou, Zhi-Yong; Sun, Osbert Jianxin

2016-01-01

Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes. We investigated tree species, soil, and site factors in relation to soil carbon density and mineralization in a temperate forest of central China. We found that soil microbial biomass and community structure, extracellular enzyme activities, and most of the site factors studied varied significantly across contrasting forest types, and that the associations between activities of soil extracellular enzymes and microbial community structure appeared to be weak and inconsistent across forest types, implicating complex mechanisms in the microbial regulation of soil carbon metabolism in relation to tree species. Overall, variations in soil carbon density and mineralization are predominantly accounted for by shared effects of tree species, soil, microclimate, and microbial traits rather than the individual effects of the four categories of factors. Our findings point to differential controls on soil carbon density and mineralization among contrasting forest types and highlight the challenge to incorporate microbial processes for constraining soil carbon dynamics in global carbon cycle models. PMID:26925871

Water repellency of clay, sand and organic soils in Finland

Directory of Open Access Journals (Sweden)

K. RASA

2008-12-01

Full Text Available Water repellency (WR delays soil wetting process, increases preferential flow and may give rise to surface runoff and consequent erosion. WR is commonly recognized in the soils of warm and temperate climates. To explore the occurrence of WR in soils in Finland, soil R index was studied on 12 sites of different soil types. The effects of soil management practice, vegetation age, soil moisture and drying temperature on WR were studied by a mini-infiltrometer with samples from depths of 0-5 and 5-10 cm. All studied sites exhibited WR (R index >1.95 at the time of sampling. WR increased as follows: sand (R = 1.8-5.0 < clay (R = 2.4-10.3 < organic (R = 7.9-undefined. At clay and sand, WR was generally higher at the soil surface and at the older sites (14 yr., where organic matter is accumulated. Below 41 vol. % water content these mineral soils were water repellent whereas organic soil exhibited WR even at saturation. These results show that soil WR also reduces water infiltration at the prevalent field moisture regime in the soils of boreal climate. The ageing of vegetation increases WR and on the other hand, cultivation reduces or hinders the development of WR.;

[Contribution of soil water at various depths to water consumption of rainfed winter wheat in the Loess tableland, China].

Science.gov (United States)

Cheng, Li Ping; Liu, Wen Zhao

2017-07-18

Soil water and stem water were collected in jointing and heading stages of the rainfed winter wheat in the Changwu Loess tableland, and the stable isotopic compositions of hydrogen and oxygen in water samples were measured to analyze the contribution of soil water at various depths to water consumption of winter wheat. The results showed that the isotopes were enriched in soil and wheat stem water in comparison with that in precipitation. Under the condition of no dry layer in soil profile, the contributions to wheat water consumption in jointing and heading stages were 5.4% and 2.6% from soil water at 0-30 cm depth, 73.4% and 67.3% at 60-90 cm depth (the main water source for winter wheat), and 7.9% and 13.5% below 120 cm depth, respectively. With the wheat growth, the contribution of soil water below the depth of 90 cm increased. It was concluded that soil evaporation mainly consumed soil water in 0-30 cm depth and wheat transpiration mainly consumed soil water below 60 cm depth in the experimental period. In the production practice, it is necessary to increase rainwater storage ratio during the summer fallow period, and apply reasonable combination of nitrogen and phosphorus fertilizers in order to increase soil moisture before wheat sowing, promote the wheat root developing deep downwards and raise the deep soil water utilization ratio.

Irrigation with saline-sodic water: effects on two clay soils

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Giovanna Cucci

2013-05-01

Full Text Available The results of a 4-year experiment aimed at evaluating the effect of irrigation with saline-sodic water on the soil are reported. The research was carried out at the Campus of the Agricultural Faculty of Bari University (Italy on 2 clay soils (Bologna – T1 and Locorotondo – T2. The soils were cropped to borlotto bean (Phaseolus vulgaris L., capsicum (Capsicum annuum L., sunflower (Helianthus annuus L., wheat (Triticum durum Desf grown in succession; the crops were irrigated with 9 saline-sodic types of water and subjected to two different leaching fractions (10% and 20% of the watering volume. The 9 solutions were obtained dissolving in de-ionised water weighted amounts of sodium chloride (NaCl and calcium chloride (CaCl2, deriving from the combination of 3 saline concentrations and 3 sodicity levels. The crops were irrigated whenever the water lost by evapotranspiration from the soil contained in the pots was equal to 30% of the soil maximum available water. The results showed that, though the soils were leached during the watering period, they showed a high salt accumulation. Consequently, the saturated soil extract electrical conductivity increased from initial values of 0.65 and 0.68 dS m-1 to 11.24 and 13.61 dS m-1 at the end of the experiment, for the soils T1 and T2, respectively. The saline concentration increase in irrigation water caused in both soils a progressive increase in exchangeable sodium, and a decrease in exchangeable calcium and non-significant variations in exchangeable potassium (K and magnesium (Mg.

The role of forest stand density in controlling soil erosion: implications to sediment-related disasters in Japan.

Science.gov (United States)

Razafindrabe, Bam H N; He, Bin; Inoue, Shoji; Ezaki, Tsugio; Shaw, Rajib

2010-01-01

The role of forest stand density in controlling soil erosion was investigated in Ehime Prefecture, Japan. The main objective was to compare soil erosion under different forest conditions including forest type, species composition, and stand density as influenced by thinning operations. Relative yield index (Ry) was used as an indicator of stand density to reflect the degree of management operations in the watershed. Eleven treatments were established based on the above forest conditions. Soil loss was collected in each of the 11 treatments after each rainfall event for a period of 1 year. The paper presents summary data on soil loss as affected by forest conditions and rainfall patterns. Findings showed that an appropriate forest management operation, which can be insured by stand density control, is needed to reduce soil loss. The present study plays an important role in clarifying technical processes related to soil erosion, while it helps linking these elements to current Japanese forestry issues and bringing new inputs to reducing sediment-related disasters in Japan.

Spatial distribution of Eucalyptus roots in a deep sandy soil in the Congo: relationships with the ability of the stand to take up water and nutrients.

Science.gov (United States)

Laclau, J P; Arnaud, M; Bouillet, J P; Ranger, J

2001-02-01

Spatial statistical analyses were performed to describe root distribution and changes in soil strength in a mature clonal plantation of Eucalyptus spp. in the Congo. The objective was to analyze spatial variability in root distribution. Relationships between root distribution, soil strength and the water and nutrient uptake by the stand were also investigated. We studied three, 2.35-m-wide, vertical soil profiles perpendicular to the planting row and at various distances from a representative tree. The soil profiles were divided into 25-cm2 grid cells and the number of roots in each of three diameter classes counted in each grid cell. Two profiles were 2-m deep and the third profile was 5-m deep. There was both vertical and horizontal anisotropy in the distribution of fine roots in the three profiles, with root density decreasing sharply with depth and increasing with distance from the stump. Roots were present in areas with high soil strength values (> 6,000 kPa). There was a close relationship between soil water content and soil strength in this sandy soil. Soil strength increased during the dry season mainly because of water uptake by fine roots. There were large areas with low root density, even in the topsoil. Below a depth of 3 m, fine roots were spatially concentrated and most of the soil volume was not explored by roots. This suggests the presence of drainage channels, resulting from the severe hydrophobicity of the upper soil.

The influence of rill density on soil erosion against USLE-soil erosion methode

OpenAIRE

Rizalihadi, A.M.; Faimah, B.E.; Nazia, C.L.

2013-01-01

Land and water is one of the major natural resource which has an important role for human life. Exploitation of land in catchment areas that not correspond to its carrying capacity will cause damage. One of the effect is increassing the soil erosion. Continuous erosion will also lead to increased sediment transport in rivers that disrupt the ship navigation on estuary due sediment accumulation. At present, soil erosion is estimated using USLE method, which is only limited to the erosion in th...

Association of water spectral indices with plant and soil water relations in contrasting wheat genotypes.

Science.gov (United States)

Gutierrez, Mario; Reynolds, Matthew P; Klatt, Arthur R

2010-07-01

Spectral reflectance indices can be used to estimate the water status of plants in a rapid, non-destructive manner. Water spectral indices were measured on wheat under a range of water-deficit conditions in field-based yield trials to establish their relationship with water relations parameters as well as available volumetric soil water (AVSW) to indicate soil water extraction patterns. Three types of wheat germplasm were studied which showed a range of drought adaptation; near-isomorphic sister lines from an elite/elite cross, advanced breeding lines, and lines derived from interspecific hybridization with wild relatives (synthetic derivative lines). Five water spectral indices (one water index and four normalized water indices) based on near infrared wavelengths were determined under field conditions between the booting and grain-filling stages of crop development. Among all water spectral indices, one in particular, which was denominated as NWI-3, showed the most consistent associations with water relations parameters and demonstrated the strongest associations in all three germplasm sets. NWI-3 showed a strong linear relationship (r(2) >0.6-0.8) with leaf water potential (psi(leaf)) across a broad range of values (-2.0 to -4.0 MPa) that were determined by natural variation in the environment associated with intra- and inter-seasonal affects. Association observed between NWI-3 and canopy temperature (CT) was consistent with the idea that genotypes with a better hydration status have a larger water flux (increased stomatal conductance) during the day. NWI-3 was also related to soil water potential (psi(soil)) and AVSW, indicating that drought-adapted lines could extract more water from deeper soil profiles to maintain favourable water relations. NWI-3 was sufficiently sensitive to detect genotypic differences (indicated by phenotypic and genetic correlations) in water status at the canopy and soil levels indicating its potential application in precision

Physical Properties of Sandy Soil Affected by Soil Conditioner Under Wetting and Drying cycles

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M.I. Choudhary

1998-06-01

Full Text Available Information on the effectiveness of soil conditioners over a prolonged period is scarce. A laboratory experiment was undertaken to evaluate the effectiveness of a polyacrylamide (Broadleaf P4 soil conditioner on the physical properties of sandy soil subjected to wetting and drying cycles. Four concentrations of Broadleaf P4 0, 0.2, 0.4, and 0.6% on dry weight basis were uniformly mixed with a calcareous sandy soil. Addition of Broadleaf P4 to sandy soil increased the water holding capacity, decreased the bulk density, and increased the porosity and void ratio at 0 and 16 wetting and drying cycles. The coefficient of linear extensibility increased considerably with increasing concentrations of the polymer. The addition of polymer at 0 and 16 cycles increased considerably the retention and availability of water in sandy soil. Saturated hydraulic conductivity decreased with increasing concentrations of Broadleaf P4 whereas unsaturated hydraulic conductivity at 0 and 16 cycles showed an increase with increasing soil moisture contents. After I6 wetting and drying cycles, the capacity of the soil to hold water was lost on average by 15.8% when compared to the 0 wetting and drying cycle. The effectiveness of the soil conditioner on bulk density, coefficient of linear extensibility, available water and saturated hydraulic conductivity was reduced on average by 14.1, 24.5, 21.l and 53.7% respectively. The significant changes in soil properties between 0 and 16 cycles suggested that the effectiveness of the conditioner decreased with the application of wetting and drying cycles. However, its effect was still considerable when compared to untreated soil under laboratory conditions.

The Effect of Community-Based Soil and Water Conservation Practices on Abundance and Diversity of Soil Macroinvertebrates in the Northern Highlands of Ethiopia

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Mengistu Welemariam

2018-04-01

Full Text Available Soil and water conservation (SWC practices in the northern highlands of Ethiopia have important implications for land restoration and biodiversity recovery. The present study determined soil macroinvertebrate (SMI abundance and diversity in response to spatial conditions i.e., generated by different conservation practices, soil depth, and temporal seasonality with the wet and dry season. The SWC practices considered were exclosure + terrace, exclosure alone, terraces, and non-conserved grazing lands. Each SWC measure was selected in three sites that were considered as replications due to low heterogeneity in terms of human and livestock disturbances and biophysical factors. Soil macroinvertebrates were collected using a monolith according to tropical soil biology and fertility (TSBF method. The highest density (55% of SMI was found in exclosures followed by terraces 26%. Non-conserved communal grazing lands account for only 19% of the total. Shannon diversity index was significantly (P < 0.05 higher (1.21 in the exclosures supported with terraces and the lowest (0.9 was observed in the non-conserved communal grazing lands. Diversity was also significantly (P < 0.05 higher (1.26 in wet than dry season (0.70. The highest (41% Sorensen similarity index among SMI was found between exclosures with terraces and exclosures alone during the wet season. The lowest (20% Sorensen similarity index was found between terraces alone and exclosures with terraces in dry season. Soil macroinvertebrate abundance was higher in upper (0–10 cm than lower (10–20 and 20–30 cm soil depth. Soil macroinvertebrate abundance was positively and strongly correlated with soil moisture (R2 = 0.85 and soil organic carbon stock (R2 = 0.95. However, it was negatively (R2 = −0.71 correlated with bulk density. Generally, the abundance and diversity of SMI increased as exclosures and communal grazing lands are supported with terraces.

Predicting oak density with ecological, physical, and soil indicators

Science.gov (United States)

Callie Jo Schweitzer; Adrian A. Lesak; Yong Wang

2006-01-01

We predicted density of oak species in the mid-Cumberland Plateau region of northeastern Alabama on the basis of basal area of tree associations based on light tolerances, physical site characteristics, and soil type. Tree basal area was determined for four species groups: oaks (Quercus spp.), hickories (Carya spp.), yellow-poplar...

Movement of Irrigation Water in Soil from a Surface Emitter

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Ibrahim Abbas Dawood

2016-09-01

Full Text Available rickle irrigation is one of the most conservative irrigation techniques since it implies supplying water directly on the soil through emitters. Emitters dissipate energy of water at the end of the trickle irrigation system and provide water at emission points. The area wetted by an emitter depends upon the discharge of emitter, soil texture, initial soil water content, and soil permeability. The objectives of this research were to predict water distribution profiles through different soils for different conditions and quantify the distribution profiles in terms of main characteristics of soil and emitter. The wetting patterns were simulated at the end of each hour for a total time of application of 12 hrs, emitter discharges of 0.5, 0.75, 1, 2, 3, 4, and 5 lph, and five initial volumetric soil water contents. Simulation of water flow from a single surface emitter was carried out by using the numerically-based software Hydrus-2D/3D, Version 2.04. Two approaches were used in developing formulas to predict the domains of the wetted pattern. In order to verify the results obtained by implementing the software Hydrus-2D/3D a field experiment was conducted to measure the wetted diameter and compare measured values with simulated ones. The results of the research showed that the developed formulas to express the wetted diameter and depth in terms of emitter discharge, time of application, and initial soil water content are very general and can be used with very good accuracy.

Measuring Low Concentrations of Liquid Water in Soil

Science.gov (United States)

Buehler, Martin

2009-01-01

An apparatus has been developed for measuring the low concentrations of liquid water and ice in relatively dry soil samples. Designed as a prototype of instruments for measuring the liquidwater and ice contents of Lunar and Martian soils, the apparatus could also be applied similarly to terrestrial desert soils and sands. The apparatus is a special-purpose impedance spectrometer: Its design is based on the fact that the electrical behavior of a typical soil sample is well approximated by a network of resistors and capacitors in which resistances decrease and capacitances increase (and, hence, the magnitude of impedance decreases) with increasing water content.

Effects of coal gangue content on water movement and solute transport in a China loess plateau soil

Energy Technology Data Exchange (ETDEWEB)

Beibei, Zhou; Quanjiu, Wang [Institute of Water Resources and Hydro-electric Engineering, Xi' an University of Technology, Xi' an (China); State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A and F University, Yangling, Shaanxi (China); Ming' an, Shao; Mingxia, Wen [State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A and F University, Yangling, Shaanxi (China); College of Resources and Environment, Northwest A and F University, Yangling, Shaanxi (China); Horton, Robert [Department of Agronomy, Iowa State University, Ames, Iowa (United States)

2010-11-15

The mining industry has grown strongly in China in recent decades, resulting in large amounts of coal gangues, which cause water and soil pollution, soil erosion, and various other environmental problems. They are often used in reclamation projects in attempts to restore land damaged by mining, hence they are frequently present (in widely varying proportions) in the topsoil in areas around mines. Their presence can strongly affect key soil variables, including its bulk density, structure, water retention, water movement, and solute transport rates. In the study presented here, the effects of gangue contents on infiltration, saturated hydraulic conductivity, and solute transport parameters of a Chinese Loess plateau soil were examined. The results show that infiltration rates and saturated hydraulic conductivity decreased with increasing gangue content. The Peck-Watson equation modeled these relationships well, but Bouwer-Rice equations provided poorer matches with the acquired data. Cumulative infiltration over time was described well by both the Philip equation and Kostiakov equation. Both the simplified convection-dispersion equation and a two-region model described the solute transport processes well. In addition, the dispersion increased, while both the Peclet number and mobile water fraction decreased, with increases in gangue contents. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Neutron probe measurement of soil water content close to soil surface

International Nuclear Information System (INIS)

Faleiros, M.C.; Ravelo S, A.; Souza, M.D. de

1993-01-01

The problem of neutron probe soil water content measurements close to soil surface is analysed from the spatial variability and also from the slow neutron loss to the atmosphere points of view. Results obtained on a dark red latosol of the county of Piracicaba, SP, indicate the possibility of precisely measuring the neutron sphere of influence when different media are used on soil surface. (author). 7 refs, 5 figs, 1 tab

Approaches and challenges of soil water monitoring in an irrigated vineyard

Science.gov (United States)

Nolz, Reinhard; Loiskandl, Willibald

2016-04-01

Monitoring of water content is an approved method to quantify certain components of the soil water balance, for example as basis for hydrological studies and soil water management. Temporal soil water data also allow controlling water status by means of demand-oriented irrigation. Regarding spatial variability of water content due to soil characteristics, plant water uptake and other non-uniformities, it is a great challenge to select a location that is most likely representing soil water status of a larger area (e.g. an irrigated field). Although such an approach might not satisfy the requirements of precision farming - which becomes more and more related to industrial agriculture - it can help improving water use efficiency of small-scale farming. In this regard, specific conditions can be found in typical vineyards in the eastern part of Austria, where grapes are grown for high quality wine production. Generally, the local dry-subhumid climate supports grape development. However, irrigation is temporarily essential in order to guarantee stable yields and high quality. As the local winegrowers traditionally control irrigation based on their experience, there is a potential to improve irrigation management by means of soil water data. In order to gain experience with regard to irrigation management, soil water status was determined in a small vineyard in Austria (47°48'16'' N, 17°01'57'' E, 118 m elevation). The vineyard was equipped with a subsurface drip irrigation system and access tubes for measuring water content in soil profiles. The latter was measured using a portable device as well as permanently installed multi-sensor capacitance probes. Soil samples were taken at chosen dates and gravimetrically analyzed in the laboratory. Water content data were analyzed using simple statistical procedures and the temporal stability concept. Soil water content was interpreted considering different environmental conditions, including rainfall and irrigation periods

Measuring and understanding soil water repellency through novel interdisciplinary approaches

Science.gov (United States)

Balshaw, Helen; Douglas, Peter; Doerr, Stefan; Davies, Matthew

2017-04-01

Food security and production is one of the key global issues faced by society. It has become evermore essential to work the land efficiently, through better soil management and agronomy whilst protecting the environment from air and water pollution. The failure of soil to absorb water - soil water repellency - can lead to major environmental problems such as increased overland flow and soil erosion, poor uptake of agricultural chemicals and increased risk of groundwater pollution due to the rapid transfer of contaminants and nutrient leaching through uneven wetting and preferential flow pathways. Understanding the causes of soil hydrophobicity is essential for the development of effective methods for its amelioration, supporting environmental stability and food security. Organic compounds deposited on soil mineral or aggregate surfaces have long been recognised as a major factor in causing soil water repellency. It is widely accepted that the main groups of compounds responsible are long-chain acids, alkanes and other organic compounds with hydrophobic properties. However, when reapplied to sands and soils, the degree of water repellency induced by these compounds and mixtures varied widely with compound type, amount and mixture, in a seemingly unpredictable way. Our research to date involves two new approaches for studying soil wetting. 1) We challenge the theoretical basis of current ideas on the measured water/soil contact angle measurements. Much past and current discussion involves Wenzel and Cassie-Baxter models to explain anomalously high contact angles for organics on soils, however here we propose that these anomalously high measured contact angles are a consequence of the measurement of a water drop on an irregular non-planar surface rather than the thermodynamic factors of the Cassie-Baxter and Wenzel models. In our analysis we have successfully used a much simpler geometric approach for non-flat surfaces such as soil. 2) Fluorescent and phosphorescent

Water erosion and soil water infiltration in different stages of corn development and tillage systems

OpenAIRE

Daniel F. de Carvalho; Eliete N. Eduardo; Wilk S. de Almeida; Lucas A. F. Santos; Teodorico Alves Sobrinho

2015-01-01

ABSTRACTThis study evaluated soil and water losses, soil water infiltration and infiltration rate models in soil tillage systems and corn (Zea mays, L.) development stages under simulated rainfall. The treatments were: cultivation along contour lines, cultivation down the slope and exposed soil. Soil losses and infiltration in each treatment were quantified for rains applied using a portable simulator, at 0, 30, 60 and 75 days after planting. Infiltration rates were estimated using the models...

The estimation of soil water fluxes using lysimeter data

Science.gov (United States)

Wegehenkel, M.

2009-04-01

The validation of soil water balance models regarding soil water fluxes in the field is still a problem. This requires time series of measured model outputs. In our study, a soil water balance model was validated using lysimeter time series of measured model outputs. The soil water balance model used in our study was the Hydrus-1D-model. This model was tested by a comparison of simulated with measured daily rates of actual evapotranspiration, soil water storage, groundwater recharge and capillary rise. These rates were obtained from twelve weighable lysimeters with three different soils and two different lower boundary conditions for the time period from January 1, 1996 to December 31, 1998. In that period, grass vegetation was grown on all lysimeters. These lysimeters are located in Berlin, Germany. One potential source of error in lysimeter experiments is preferential flow caused by an artificial channeling of water due to the occurrence of air space between the soil monolith and the inside wall of the lysimeters. To analyse such sources of errors, Hydrus-1D was applied with different modelling procedures. The first procedure consists of a general uncalibrated appli-cation of Hydrus-1D. The second one includes a calibration of soil hydraulic parameters via inverse modelling of different percolation events with Hydrus-1D. In the third procedure, the model DUALP_1D was applied with the optimized hydraulic parameter set to test the hy-pothesis of the existence of preferential flow paths in the lysimeters. The results of the different modelling procedures indicated that, in addition to a precise determination of the soil water retention functions, vegetation parameters such as rooting depth should also be taken into account. Without such information, the rooting depth is a calibration parameter. However, in some cases, the uncalibrated application of both models also led to an acceptable fit between measured and simulated model outputs.

Aggregating available soil water holding capacity data for crop yield models

Science.gov (United States)

Seubert, C. E.; Daughtry, C. S. T.; Holt, D. A.; Baumgardner, M. F.

1984-01-01

The total amount of water available to plants that is held against gravity in a soil is usually estimated as the amount present at -0.03 MPa average water potential minus the amount present at -1.5 MPa water potential. This value, designated available water-holding capacity (AWHC), is a very important soil characteristic that is strongly and positively correlated to the inherent productivity of soils. In various applications, including assessing soil moisture status over large areas, it is necessary to group soil types or series as to their productivity. Current methods to classify AWHC of soils consider only total capacity of soil profiles and thus may group together soils which differ greatly in AWHC as a function of depth in the profile. A general approach for evaluating quantitatively the multidimensional nature of AWHC in soils is described. Data for 902 soil profiles, representing 184 soil series, in Indiana were obtained from the Soil Characterization Laboratory at Purdue University. The AWHC for each of ten 150-mm layers in each soil was established, based on soil texture and parent material. A multivariate clustering procedure was used to classify each soil profile into one of 4, 8, or 12 classes based upon ten-dimensional AWHC values. The optimum number of classes depends on the range of AWHC in the population of oil profiles analyzed and on the sensitivity of a crop to differences in distribution of water within the soil profile.

Assessing interactions of hydrophilic nanoscale TiO{sub 2} with soil water

Energy Technology Data Exchange (ETDEWEB)

Priester, John H.; Ge, Yuan; Chang, Vivian [University of California, Santa Barbara, Bren School of Environmental Science and Management (United States); Stoimenov, Peter K. [University of California, Santa Barbara, Department of Chemistry and Biochemistry (United States); Schimel, Joshua P. [University of California, Santa Barbara, Earth Research Institute (United States); Stucky, Galen D. [University of California, Santa Barbara, UC Center for the Environmental Implications of Nanotechnology (United States); Holden, Patricia A., E-mail: holden@bren.ucsb.edu [University of California, Santa Barbara, Bren School of Environmental Science and Management (United States)

2013-09-15

The implications of manufactured nanoscale materials (MNMs) in unsaturated soil are mostly unknown. Owing to its widespread use, nanoscale (n) TiO{sub 2} is expected to enter soils where its accumulation could impact soil processes. Yet fundamental information is lacking regarding nTiO{sub 2} in situ wettability, i.e., interactions with soil water that relate to nTiO{sub 2} exposure and bioavailability. To probe nTiO{sub 2} interactions with soil water, we amended a natural soil with 20 mg per g of P25 nTiO{sub 2}, a high-production, hydrophilic MNM that, based on its small size (25 nm nominal), provides ample specific surface area (SSA) for water sorption. We then measured nTiO{sub 2}-amended soil SSA, and conducted a dynamic water vapor conditioning experiment. Early time-course water sorption into soil, with and without nTiO{sub 2}, was clearly diffusional. Over 9 months, soil water content asymptotically equilibrated. However, despite amending with nTiO{sub 2} levels that increased the soil SSA by 16 %, measured water sorption rates and endpoint soil water contents were mostly unchanged by P25 nTiO{sub 2}. Our results indicate that as-manufactured hydrophilic P25 nTiO{sub 2} was hydrophobic in soil, a finding relevant to nTiO{sub 2} bioavailability and transport.

WATER INFILTRATION IN TWO CULTIVATED SOILS IN SOUTHERN BRAZIL

Directory of Open Access Journals (Sweden)

Ildegardis Bertol

2015-04-01

Full Text Available Infiltration is the passage of water through the soil surface, influenced by the soil type and cultivation and by the soil roughness, surface cover and water content. Infiltration absorbs most of the rainwater and is therefore crucial for planning mechanical conservation practices to manage runoff. This study determined water infiltration in two soil types under different types of management and cultivation, with simulated rainfall of varying intensity and duration applied at different times, and to adjust the empirical model of Horton to the infiltration data. The study was conducted in southern Brazil, on Dystric Nitisol (Nitossolo Bruno aluminoférrico húmico and Humic Cambisol (Cambissolo Húmico alumínico léptico soils to assess the following situations: simulated rains on the Nitisol from 2001 to 2012 in 31 treatments, differing in crop type, sowing direction, type of soil opener on the seeder, amount and type of crop residue and amount of liquid swine manure applied; on the Cambisol, rains were simlated from 2006 to 2012 and 18 treatments were evaluated, differing in crop, seeding direction and crop residue type. The constant of the water infiltration rate into the soil varies significantly with the soil type (30.2 mm h-1 in the Nitisol and 6.6 mm h-1 in the Cambisol, regardless of the management system, application time and rain intensity and duration. At the end of rainfalls, soil-water infiltration varies significantly with the management system, with the timing of application and rain intensity and duration, with values ranging from 13 to 59 mm h-1, in the two studied soils. The characteristics of the sowing operation in terms of relief, crop type and amount and type of crop residue influenced soil water infiltration: in the Nitisol, the values of contour and downhill seeding vary between 27 and 43 mm h-1, respectively, with crop residues of corn, wheat and soybean while in the Cambisol, the variation is between 2 and 36 mm h-1

The recent similarity hypotheses to describe water infiltration into homogeneous soils

OpenAIRE

Reichardt,Klaus; Timm,Luís Carlos; Dourado-Neto,Durval

2016-01-01

ABSTRACT A similarity hypothesis recently presented to describe horizontal infiltration into homogeneous soils, developed for coarse-textured soils like sieved marine sand, implies that the soil water retention function θ(h) is the mirror image of an extended Boltzmann transform function θ(λ2). A second hypothesis applicable to vertical infiltration suggests that the soil water retention function θ(h) is also the mirror image of the soil water profile θ(z). Using prev...

Effects of past copper contamination and soil structure on copper leaching from soil

DEFF Research Database (Denmark)

Paradelo, M; Møldrup, Per; Arthur, Emmanuel

2013-01-01

Copper contamination affects biological, chemical, and physical soil properties and associated ecological functions. Changes in soil pore organization as a result of Cu contamination can dramatically affect flow and contaminant transport in polluted soils. This study assessed the influence of soil...... structure on the movement of water and Cu in a long-term polluted soil. Undisturbed soil cores collected along a Cu gradient (from about 20 to about 3800 mg Cu kg−1 soil) were scanned using X-ray computed tomography (CT). Leaching experiments were performed to analyze tracer transport, colloid leaching......, and dissolved organic carbon (DOC) and Cu losses. The 5% arrival time (t0.05) and apparent dispersivity (λapp) for tracer breakthrough were calculated by fitting the experimental data to a nonparametric, double-lognormal probability density function. Soil bulk density, which did not follow the Cu gradient...

Root-soil relationships and terroir

Science.gov (United States)

Tomasi, Diego

2015-04-01

Soil features, along with climate, are among the most important determinants of a succesful grape production in a certain area. Most of the studies, so far, investigated the above-ground vine response to differente edaphic and climate condition, but it is clearly not sufficient to explain the vine whole behaviour. In fact, roots represent an important part of the terroir system (soil-plant-atmosphere-man), and their study can provide better comprehension of vine responses to different environments. The root density and distribution, the ability of deep-rooting and regenerating new roots are good indicators of root well-being, and represents the basis for an efficient physiological activity of the root system. Root deepening and distribution are strongly dependent and sensitive on soil type and soil properties, while root density is affected mostly by canopy size, rootstock and water availability. According to root well-being, soil management strategies should alleviate soil impediments, improving aeration and microbial activity. Moreover, agronomic practices can impact root system performance and influence the above-ground growth. It is well known, for example, that the root system size is largely diminished by high planting densities. Close vine spacings stimulate a more effective utilization of the available soil, water and nutrients, but if the competition for available soil becomes too high, it can repress vine growth, and compromise vineyard longevity, productivity and reaction to growing season weather. Development of resilient rootstocks, more efficient in terms of water and nutrient uptake and capable of dealing with climate and soil extremes (drought, high salinity) are primary goals fore future research. The use of these rootstocks will benefit a more sustainable use of the soil resources and the preservation and valorisation of the terroir.

Development of a soil water dispersion index (SOWADIN) for testing the effectiveness of a soil-wetting agent

International Nuclear Information System (INIS)

Sawada, Y.; Aylmore, L.A.G.; Hainsworth, J.M.

1989-01-01

Computer-assisted tomography (CAT) applied to gamma-ray attenuation measurement has been used to develop an index termed the soil water dispersion index (SOWADIN), which describes quantitatively the amount and distribution of water in soil columns. The index, which is determined by classifying pixels in a scanned slice into three categories according to their attenuation coefficients, contains two numerical values. The first value corresponds to the water content of the scanned slice and the second value is a measure of the dispersion of the water throughout the slice. Artificially wetted zones were created in soil columns to give one-third of the scanned layer wetted with various patterns of wetted-area distribution. The SOWADIN values obtained accurately reflected the differences in water distribution associated with the different patterns. Application of SOWADIN to columns of a water-repellent sand before and after treatment with a soil-wetting agent clearly illustrates both the increase in water content and improvement in water distribution in the soil column following treatment. 33 refs., 3 figs., 2 tabs

Model for tritiated water transport in soil

International Nuclear Information System (INIS)

Galeriu, D.; Paunescu, N.

1999-01-01

Chemical forms of tritium released from nuclear facilities are mostly water (HTO) and hydrogen (HT, TT). Elemental tritium is inert in vegetation and superior animals, but the microorganisms from soil oxidize HT to HTO. After an atmospheric HT emission, in short time an equivalent quantity of HTO is re-emitted from soil. In the vicinity of a tritium source the spatial and temporary distribution of HTO is dependent on the chemical form of tritium releases. During routine tritium releases (continuously and constant releases), the local distribution of tritium reaches equilibrium, and specific activities of tritium in environmental compartments are almost equal. The situation is very different after an accidental emission. Having in view, harmful effects of tritium when it is incorporated into the body several models were developed for environmental tritium transport and dose assessment. The tritium transport into the soil is an important part of the environmental tritium behavior, but, unfortunately, in spite of the importance of this problem the corresponding modeling is unsatisfactory. The aim of this paper was the improvement of the TRICAIAP model, and the application of the model to BIOMOVS scenario. The BIOMOVS scenario predicts HTO concentrations in soil during 30 days, after one hour atmospheric HTO emission. The most important conclusions of the paper are: the principal carrier of tritium into the soil is water; the transfer processes are the reactions of water in soil and the diffusion due to concentration gradient; atmosphere-soil transport is dependent of surface characteristics (granulation, humidity, roughness, etc.); the conversion rate of HT to HTO is not well known and is dependent on active microorganism concentration in soil and on soil humidity. More experimental data are needed to decrease the uncertainty of transfer parameter, for the definition of the influence of vegetation, etc. (authors)

Modelling soil water content variations under drought stress on soil column cropped with winter wheat

Directory of Open Access Journals (Sweden)

Csorba Szilveszter

2014-12-01

Full Text Available Mathematical models are effective tools for evaluating the impact of predicted climate change on agricultural production, but it is difficult to test their applicability to future weather conditions. We applied the SWAP model to assess its applicability to climate conditions, differing from those, for which the model was developed. We used a database obtained from a winter wheat drought stress experiment. Winter wheat was grown in six soil columns, three having optimal water supply (NS, while three were kept under drought-stressed conditions (S. The SWAP model was successfully calibrated against measured values of potential evapotranspiration (PET, potential evaporation (PE and total amount of water (TSW in the soil columns. The Nash-Sutcliffe model efficiency coefficient (N-S for TWS for the stressed columns was 0.92. For the NS treatment, we applied temporally variable soil hydraulic properties because of soil consolidation caused by regular irrigation. This approach improved the N-S values for the wetting-drying cycle from -1.77 to 0.54. We concluded that the model could be used for assessing the effects of climate change on soil water regime. Our results indicate that soil water balance studies should put more focus on the time variability of structuredependent soil properties.

Thematic issue on soil water infiltration

Science.gov (United States)

Infiltration is the term applied to the process of water entry into the soil, generally by downward flow through all or part of the soil surface. Understanding of infiltration concept and processes has greatly improved, over the past 30 years, and new insights have been given into modeling of non-un...

Water management in sandy soil using neutron scattering method

International Nuclear Information System (INIS)

Mohamed, K.M.

2011-01-01

This study was carried out during 2008/2009 at the Experimental Field of Soil and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Inshas in a newly reclaimed sandy soil. The aims of this work are,- determine soil moisture tension within the active root zone and - detecting the behavior of soil moisture within the active root zoon by defines the total hydraulic potential within the soil profile to predict both of actual evapotranspiration and rate of moisture depletion This work also is aimed to study soil water distribution under drip irrigation system.- reducing water deep percolation under the active root depth.This study included two factors, the first one is the irrigation intervals, and the second one is the application rate of organic manure. Irrigation intervals were 5, 10 and 15 days, besides three application rates of organic manure (0 m 3 /fed, 20 m 3 /fed. and 30 m 3 /fed.) in -three replicates under drip irrigation system, Onion was used as an indicator plant. Obtained data show, generally, that neutron scattering technique and soil moisture retention curve model helps more to study the water behavior in the soil profile.Application of organic manure and irrigation to field capacity is a good way to minimize evapotranspiration and deep percolation, which was zero mm/day in the treated treatments.The best irrigation interval for onion plant, in the studied soil, was 5 days with 30m 3 /fad. an application rate of organic manure.Parameter α of van Genuchent's 1980 model was affected by the additions of organic manure, which was decreased by addition of organic manure decreased it. Data also showed that n parameter was decreased by addition of organic manure Using surfer program is a good tool to describe the water distribution in two directions (vertical and horizontal) through soil profile.

Effect of Soil Water Content on the Distribution of Diuron into Organomineral Aggregates of Highly Weathered Tropical Soils.

Science.gov (United States)

Regitano, Jussara B; Rocha, Wadson S D; Bonfleur, Eloana J; Milori, Debora; Alleoni, Luís R F

2016-05-25

We evaluated the effects of soil water content on the retention of diuron and its residual distribution into organomineral aggregates in four Brazilian oxisols. (14)C-Diuron was incubated for days at 25, 50, and 75% of maximum water-holding capacity for each soil. After 42 days, the physical fractionation method was used to obtain >150, 53-150, 20-53, 2-20, and retention increased with increasing soil water content for all soils. At lower soil water content, diuron's retention was higher in the sandier soil. It was mostly retained in the fine (retention was higher in the coarse aggregates (>53 μm). The sorption coefficients (Kd and Koc) generated by batch studies should be carefully used because they do not provide information about aggregation and diffusion effects on pesticides soil sorption.

Difficulties in the evaluation and measuring of soil water infiltration

Science.gov (United States)

Pla-Sentís, Ildefonso

2013-04-01

Soil water infiltration is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the evaluation and measurement of water infiltration rates has become indispensable for the evaluation and modeling of the previously mentioned processes. Infiltration is one of the most difficult hydrological parameters to evaluate or measure accurately. Although the theoretical aspects of the process of soil water infiltration are well known since the middle of the past century, when several methods and models were already proposed for the evaluation of infiltration, still nowadays such evaluation is not frequently enough accurate for the purposes being used. This is partially due to deficiencies in the methodology being used for measuring infiltration, including some newly proposed methods and equipments, and in the use of non appropriate empirical models and approaches. In this contribution we present an analysis and discussion about the main difficulties found in the evaluation and measurement of soil water infiltration rates, and the more commonly committed errors, based on the past experiences of the author in the evaluation of soil water infiltration in many different soils and land conditions, and in their use for deducing soil water balances under variable and changing climates. It is concluded that there are not models or methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil

Links between matrix bulk density, macropore characteristics and hydraulic behavior of soils

DEFF Research Database (Denmark)

Katuwal, Sheela; Møldrup, Per; Lamandé, Mathieu

2013-01-01

characteristics on soil hydraulic functions has rarely been studied. With the objective of studying the links between these parameters we quantified macropore characteristics of intact soil columns (19 cm diameter x 20 cm high) from two agricultural field sites (Silstrup and Faardrup) in Denmark using coarse...... resolution X-ray CT and linked them with laboratory measurements of air permeability and leaching experiment. In addition to macropore characteristics, we also quantified the CT-number of the matrix as a measure of the bulk density of the matrix, i.e., excluding macropores in the soil. Soils from the two...

Isotope fractionation of sandy-soil water during evaporation - an experimental study.

Science.gov (United States)

Rao, Wen-Bo; Han, Liang-Feng; Tan, Hong-Bing; Wang, Shuai

2017-06-01

Soil samples containing water with known stable isotopic compositions were prepared. The soil water was recovered by using vacuum/heat distillation. The experiments were held under different conditions to control rates of water evaporation and water recovery. Recoveries, δ 18 O and δ 2 H values of the soil water were determined. Analyses of the data using a Rayleigh distillation model indicate that under the experimental conditions only loosely bound water is extractable in cases where the recovery is smaller than 100 %. Due to isotopic exchange between vapour and remaining water in the micro channels or capillaries of the soil matrix, isotopic fractionation may take place under near-equilibrium conditions. This causes the observed relationship between δ 2 H and δ 18 O of the extracted water samples to have a slope close to 8. The results of this study may indicate that, in arid zones when soil that initially contains water dries out, the slope of the relationship between δ 2 H and δ 18 O values should be close to 8. Thus, a smaller slope, as observed by some groundwater and soil water samples in arid zones, may be caused by evaporation of water before the water has entered the unsaturated zone.

Post-fire interactions between soil water repellency, soil fertility and plant growth in soil collected from a burned piñon-juniper woodland

Science.gov (United States)

Fernelius, Kaitlynn J.; Madsen, Matthew D.; Hopkins, Bryan G.; Bansal, Sheel; Anderson, Val J.; Eggett, Dennis L.; Roundy, Bruce A.

2017-01-01

Woody plant encroachment can increase nutrient resources in the plant-mound zone. After a fire, this zone is often found to be water repellent. This study aimed to understand the effects of post-fire water repellency on soil water and inorganic nitrogen and their effects on plant growth of the introduced annual Bromus tectorum and native bunchgrass Pseudoroegneria spicata. Plots centered on burned Juniperus osteosperma trees were either left untreated or treated with surfactant to ameliorate water repellency. After two years, we excavated soil from the untreated and treated plots and placed it in zerotension lysimeter pots. In the greenhouse, half of the pots received an additional surfactant treatment. Pots were seeded separately with B. tectorum or P. spicata. Untreated soils had high runoff, decreased soilwater content, and elevated NO3eN in comparison to surfactant treated soils. The two plant species typically responded similar to the treatments. Above-ground biomass and microbial activity (estimated through soil CO2 gas emissions) was 16.8-fold and 9.5-fold higher in the surfactant-treated soils than repellent soils, respectably. This study demonstrates that water repellency can influence site recovery by decreasing soil water content, promoting inorganic N retention, and impairing plant growth and microbial activity.

Effect of collimator size and absorber thickness on soil bulk density evaluation by gamma-ray attenuation

International Nuclear Information System (INIS)

Costa, J.C.; Borges, J.A.R.; Pires, L.F.

2014-01-01

Representative measurements of the soil bulk density (ρ s ) can be affected depending on the geometry selected for gamma-ray attenuation (GRA) measurements. In this study, the effect of collimator size (2–4 mm diameters) and absorber thickness (2–15 cm) on ρ s measurements of sandy and clayey soils was investigated. In summary, the results obtained for the 137 Cs show that ρ s remained fairly constant for values of thickness larger than 7 cm (both soils). The very same result was observed for collimator sizes 2–4 mm. Regarding the 241 Am source, ρ s values presented variations with the collimator size (both soils) for the different thicknesses. The best values of ρ s were obtained for samples smaller than 5 cm and also for the small collimator diameters. - Highlights: ► Representative measurements of the soil bulk density by gamma-ray attenuation. ► For 137 Cs the best bulk density values were obtained for samples larger than 7 cm. ► For 241 Am the best bulk density values were obtained for samples smaller than 5 cm

Adaptation Strategies of Soil and Water Conservation in Taiwan for Extreme Climate

Science.gov (United States)

Huang, Wen-Cheng; Lin, Cheng-Yu; Hsieh, Ting-Ju

2016-04-01

Due to global climate change, the impact caused by extreme climate has become more and more compelling. In Taiwan, the total rainfall stays in the same level, but it brings along changes to rain types. The rainfall with high recurrence interval happens frequently, leading to soil loss of slope-land, and it may further result in flooding and sediment hazards. Although Taiwan is a small island, the population density is ranked at the second highest around the world. Moreover, third-fourth of Taiwan is slope-land, so the soil and water conservation is rather important. This study is based on the international trend analysis approach to review the related researches worldwide and 264 research projects in Taiwan. It indicates that under the pressure of extreme climate and social economic changes, it has higher possibility of slope-land to face the impacts from extreme rainfall events, and meanwhile, the carrying capacity of slope-land is decreasing. The experts' brainstorming meetings were held three times, and it concluded the current problems of soil and water conservation and the goal in 2025 for sustainable resources. Also, the 20-year weather data set was adopted to screen out 3 key watersheds with the potential of flooding (Puzih River Watershed), droughts (Xindian River Watershed), and sediment hazards (Chishan River Watershed) according to the moisture index, and further, to propose countermeasures in order to realize the goal in 2025, which is "regarding to climate and socioeconomic changes, it is based on multiple use to manage watershed resources for avoiding disasters and sustaining soil and water conservation." Keyword: Extreme climate, International trend analysis, Brainstorming, Key watershed

Performance of neutron scattering relative to Diviner2000 for estimating soil water content in salt affected soils

International Nuclear Information System (INIS)

Al-Ain, F.; Attar, J.; Hussein, F.

2007-05-01

A field experiment was conducted on sandy clay and clayey soils at Deir Ezzor to compare the performance of Neutron Scattering (NS) relative to a capacitance probe (CP), Diviner2000, in our local conditions under saline soils. The effect of soil electrical conductivity (ECe) and bulk density (?b) on the precession, accuracy and sensitivity of the tested equipment s were evaluated. Also, the ability to improve the calibration equation for these equipment s, by including ECe and ?b as independent variables in the equation formula, was studied. The study showed that, Diviner2000 was very sensitive to soil bulk density and electrical conductivity of the soil (i.e. soil salinity) compared to the NS. Multiple non-linear regressions improved the fitting when both parameters (?b and ECe) were included in the equation, even though the correlation coefficient (R2) remained low in the case of Diviner2000.(author)

Implementing a physical soil water flow model with minimal soil characteristics and added value offered by surface soil moisture measurements assimilation.

Science.gov (United States)

Chanzy, André

2010-05-01

Soil moisture is a key variable for many soil physical and biogeochemical processes. Its dynamic results from water fluxes in soil and at its boundaries, as well as soil water storage properties. If the water flows are dominated by diffusive processes, modelling approaches based on the Richard's equation or the Philip and de Vries coupled heat and water flow equations lead to a satisfactory representation of the soil moisture dynamic. However, It requires the characterization of soil hydraulic functions, the initialisation and the boundary conditions, which are expensive to obtain. The major problem to assess soil moisture for decision making or for representing its spatiotemporal evolution over complex landscape is therefore the lack of information to run the models. The aim of the presentation is to analyse how a soil moisture model can be implemented when only climatic data and basic soil information are available (soil texture, organic matter) and what would be the added of making a few soil moisture measurements. We considered the field scale, which is the key scale for decision making application (the field being the management unit for farming system) and landscape modelling (field size being comparable to the computation unit of distributed hydrological models). The presentation is limited to the bare soil case in order to limit the complexity of the system and the TEC model based on Philip and De Vries equations is used in this study. The following points are addressed: o the within field spatial variability. This spatial variability can be induced by the soil hydraulic properties and/or by the amount of infiltrated water induced by water rooting towards infiltration areas. We analyse how an effective parameterization of soil properties and boundary conditions can be used to simulate the field average moisture. o The model implementation with limited information. We propose strategies that can be implemented when information are limited to soil texture and

Field-measured, hourly soil water evaporation stages in relation to reference evapotranspiration rate and soil to air temperature ratio

Science.gov (United States)

Soil water evaporation takes critical water supplies away from crops, especially in areas where both rainfall and irrigation water are limited. This study measured bare soil water evaporation from clay loam, silt loam, sandy loam, and fine sand soils. It found that on average almost half of the ir...

Effects of water level on three wetlands soil seed banks on the Tibetan Plateau.

Directory of Open Access Journals (Sweden)

Miaojun Ma

Full Text Available BACKGROUND: Although the effect of water level on germination in soil seed banks has been documented in many ecosystems, the mechanism is not fully understood, and to date no empirical studies on this subject exist. Further, no work has been done on the effect of water level on seed banks of drying and saline-alkaline wetlands in alpine areas on the Tibetan Plateau. METHODOLOGY: We examined the effects of water level (0 cm, 5 cm and 10 cm on seed germination and seedling establishment from soil seed banks at 0-5 cm and 5-10 cm depths in typical, drying, and saline-alkaline wetlands. We also explore the potential role of soil seed bank in restoration of drying and saline-alkaline wetlands. PRINCIPAL FINDINGS: Species richness decreased with increase in water level, but there almost no change in seed density. A huge difference exists in species composition of the seed bank among different water levels in all three wetlands, especially between 0 cm and 5 cm and 0 cm and 10 cm. Similarity of species composition between seed bank and plant community was higher in 0 cm water level in drying wetland than in the other two wetlands. The similarity was much higher in 0 cm water level than in 5 cm and 10 cm water levels in all three wetlands. Species composition of the alpine wetland plant community changed significantly after drying and salinization, however, species composition of the seed bank was unchanged regardless of the environment change. CONCLUSIONS/SIGNIFICANCE: Water level greatly affects seed bank recruitment and plant community establishment. Further, different water levels in restored habitats are likely to determine its species composition of the plant community. The seed bank is important in restoration of degraded wetlands. Successful restoration of drying and salinization wetlands could depend on the seed bank.