Effects of long-term grassland management on the carbon and nitrogen pools of different soil aggregate fractions.

Science.gov (United States)

Egan, Gary; Crawley, Michael J; Fornara, Dario A

2018-02-01

Common grassland management practices include animal grazing and the repeated addition of lime and nutrient fertilizers to soils. These practices can greatly influence the size and distribution of different soil aggregate fractions, thus altering the cycling and storage of carbon (C) and nitrogen (N) in grassland soils. So far, very few studies have simultaneously addressed the potential long-term effect that multiple management practices might have on soil physical aggregation. Here we specifically ask whether and how grazing, liming and nutrient fertilization might influence C and N content (%) as well as C and N pools of different soil aggregate fractions in a long-term grassland experiment established in 1991 at Silwood Park, Berkshire, UK. We found that repeated liming applications over 23years significantly decreased the C pool (i.e. gCKg -1 soil) of Large Macro Aggregate (LMA>2mm) fractions and increased C pools within three smaller soil aggregate fractions: Small Macro Aggregate (SMA, 250μm-2mm), Micro Aggregate (MiA, 53-250μm), and Silt Clay Aggregate (SCAfractions was mainly caused by positive liming effects on aggregate fraction mass rather than on changes in soil C (and N) content (%). Liming effects could be explained by increases in soil pH, as this factor was significantly positively related to greater soil C and N pools of smaller aggregate fractions. Long-term grazing and inorganic nutrient fertilization had much weaker effects on both soil aggregate-fraction mass and on soil C and N concentrations, however, our evidence is that these practices could also contribute to greater C and N pools of smaller soil fractions. Overall our study demonstrates how agricultural liming can contribute to increase C pools of small (more stable) soil fractions with potential significant benefits for the long-term C balance of human-managed grassland soils. Copyright © 2017 Elsevier B.V. All rights reserved.

The specific role of fungal community structure on soil aggregation and carbon sequestration: results from long-term field study in a paddy soil

Science.gov (United States)

Murugan, Rajasekaran; Kumar, Sanjay

2015-04-01

Soil aggregate stability is a crucial soil property that affects soil biota, biogeochemical processes and C sequestration. The relationship between soil aggregate stability and soil C cycling is well known but the influence of specific fungal community structure on this relationship is largely unknown in paddy soils. The aim of the present study was to evaluate the long-term fertilisation (mineral fertiliser-MIN; farmyard manure-FYM; groundnut oil cake-GOC) effects on soil fungal community shifts associated with soil aggregates under rice-monoculture (RRR) and rice-legume-rice (RLR) systems. Fungal and bacterial communities were characterized using phospholipid fatty acids, and glucosamine and muramic acid were used as biomarkers for fungal and bacterial residues, respectively. Microbial biomass C and N, fungal biomass and residues were significantly higher in the organic fertiliser treatments than in the MIN treatment, for all aggregate sizes under both crop rotation systems. In general, fungal/bacterial biomass ratio and fungal residue C/bacterial residue C ratio were significantly higher in macroaggregate fractions (> 2000 and 250-2000 μm) than in microaggregate fractions (53-250 and crop rotation systems, the long-term application of FYM and GOC led to increased accumulation of saprotrophic fungi (SF) in aggregate fractions > 2000 μm. In contrast, we found that arbuscular mycorrhizal fungi (AMF) was surprisingly higher in aggregate fractions > 2000 μm than in aggregate fraction 250-2000 μm under MIN treatment. The RLR system showed significantly higher AMF biomass and fungal residue C/ bacterial residue C ratio in both macroaggregate fractions compared to the RRR system. The strong relationships between SF, AMF and water stable aggregates shows the specific contribution of fungi community on soil aggregate stability. Our results highlight the fact that changes within fungal community structure play an important role in shaping the soil aggregate stability

A Novel Method to Quantify Soil Aggregate Stability by Measuring Aggregate Bond Energies

Science.gov (United States)

Efrat, Rachel; Rawlins, Barry G.; Quinton, John N.; Watts, Chris W.; Whitmore, Andy P.

2016-04-01

Soil aggregate stability is a key indicator of soil quality because it controls physical, biological and chemical functions important in cultivated soils. Micro-aggregates are responsible for the long term sequestration of carbon in soil, therefore determine soils role in the carbon cycle. It is thus vital that techniques to measure aggregate stability are accurate, consistent and reliable, in order to appropriately manage and monitor soil quality, and to develop our understanding and estimates of soil as a carbon store to appropriately incorporate in carbon cycle models. Practices used to assess the stability of aggregates vary in sample preparation, operational technique and unit of results. They use proxies and lack quantification. Conflicting results are therefore drawn between projects that do not provide methodological or resultant comparability. Typical modern stability tests suspend aggregates in water and monitor fragmentation upon exposure to an un-quantified amount of ultrasonic energy, utilising a laser granulometer to measure the change in mean weight diameter. In this project a novel approach has been developed based on that of Zhu et al., (2009), to accurately quantify the stability of aggregates by specifically measuring their bond energies. The bond energies are measured operating a combination of calorimetry and a high powered ultrasonic probe, with computable output function. Temperature change during sonication is monitored by an array of probes which enables calculation of the energy spent heating the system (Ph). Our novel technique suspends aggregates in heavy liquid lithium heteropolytungstate, as opposed to water, to avoid exposing aggregates to an immeasurable disruptive energy source, due to cavitation, collisions and clay swelling. Mean weight diameter is measured by a laser granulometer to monitor aggregate breakdown after successive periods of calculated ultrasonic energy input (Pi), until complete dispersion is achieved and bond

Symbiosis of Arbuscular Mycorrhizal Fungi and Robinia pseudoacacia L. Improves Root Tensile Strength and Soil Aggregate Stability.

Science.gov (United States)

Zhang, Haoqiang; Liu, Zhenkun; Chen, Hui; Tang, Ming

2016-01-01

Robinia pseudoacacia L. (black locust) is a widely planted tree species on Loess Plateau for revegetation. Due to its symbiosis forming capability with arbuscular mycorrhizal (AM) fungi, we explored the influence of arbuscular mycorrhizal fungi on plant biomass, root morphology, root tensile strength and soil aggregate stability in a pot experiment. We inoculated R. pseudoacacia with/without AM fungus (Rhizophagus irregularis or Glomus versiforme), and measured root colonization, plant growth, root morphological characters, root tensile force and tensile strength, and parameters for soil aggregate stability at twelve weeks after inoculation. AM fungi colonized more than 70% plant root, significantly improved plant growth. Meanwhile, AM fungi elevated root morphological parameters, root tensile force, root tensile strength, Glomalin-related soil protein (GRSP) content in soil, and parameters for soil aggregate stability such as water stable aggregate (WSA), mean weight diameter (MWD) and geometric mean diameter (GMD). Root length was highly correlated with WSA, MWD and GMD, while hyphae length was highly correlated with GRSP content. The improved R. pseudoacacia growth, root tensile strength and soil aggregate stability indicated that AM fungi could accelerate soil fixation and stabilization with R. pseudoacacia, and its function in revegetation on Loess Plateau deserves more attention.

Denitrification in Soil Aggregate Analogues-Effect of Aggregate Size and Oxygen Diffusion

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Steffen Schlüter

2018-04-01

Full Text Available Soil-borne nitrous oxide (N2O emissions have a high spatial and temporal variability which is commonly attributed to the occurrence of hotspots and hot moments for microbial activity in aggregated soil. Yet there is only limited information about the biophysical processes that regulate the production and consumption of N2O on microscopic scales in undisturbed soil. In this study, we introduce an experimental framework relying on simplified porous media that circumvents some of the complexities occuring in natural soils while fully accounting for physical constraints believed to control microbial activity in general and denitrification in particular. We used this framework to explore the impact of aggregate size and external oxygen concentration on the kinetics of O2 consumption, as well as CO2 and N2O production. Model aggregates of different sizes (3.5 vs. 7 mm diameter composed of porous, sintered glass were saturated with a defined growth medium containing roughly 109 cells ml−1 of the facultative anaerobic, nosZ-deficient denitrifier Agrobacterium tumefaciens with N2O as final denitrification product and incubated at five different oxygen levels (0–13 vol-%. We demonstrate that the onset of denitrification depends on the amount of external oxygen and the size of aggregates. Smaller aggregates were better supplied with oxygen due to a larger surface-to-volume ratio, which resulted in faster growth and an earlier onset of denitrification. In larger aggregates, the onset of denitrification was more gradual, but with comparably higher N2O production rates once the anoxic aggregate centers were fully developed. The normalized electron flow from the reduced carbon substrate to N-oxyanions (edenit-/etotal- ratio could be solely described as a function of initial oxygen concentration in the headspace with a simple, hyperbolic model, for which the two empirical parameters changed with aggregate size in a consistent way. These findings confirm the

Response of soil aggregate stability to storage time of soil samples

International Nuclear Information System (INIS)

Gerzabek, M.H.; Roessner, H.

1993-04-01

The aim of the present study was to investigate the well known phenomenon of changing aggregate stability values as result of soil sample storage. In order to evaluate the impact of soil microbial activity, the soil sample was split into three subsamples. Two samples were sterilized by means of chloroform fumigation and gamma irradiation, respectively. However, the aggregate stability measurements at three different dates were not correlated with the microbial activity (dehydrogenase activity). The moisture content of the aggregate samples seems to be of higher significance. Samples with lower moisture content (range: 0.4 to 1.9%) exhibited higher aggregate stabilities. Thus, airdried aggregate samples without further treatment don't seem to be suitable for standardized stability measurements. (authors)

Soil dehydrogenase activity of natural macro aggregates in a toposequence of forest soil

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Maira Kussainova

2013-01-01

Full Text Available The main objective of this study was to determine changes in soil dehydrogenase activity in natural macro aggregates development along a slope in forest soils. This study was carried out in Kocadag, Samsun, Turkey. Four landscape positions i.e., summit, shoulder backslope and footslope, were selected. For each landseape position, soil macro aggregates were separated into six aggregate size classes using a dry sieving method and then dehydrogenase activity was analyzed. In this research, topography influenced the macroaggregate size and dehydrogenase activity within the aggregates. At all landscape positions, the contents of macro aggregates (especially > 6.3 mm and 2.00–4.75 mm in all soil samples were higher than other macro aggregate contents. In footslope position, the soils had generally the higher dehydrogenase activity than the other positions at all landscape positions. In all positions, except for shoulder, dehydrogenase activity was greater macro aggregates of <1 mm than in the other macro aggregate size.

Microbial properties of soil aggregates created by earthworms and other factors: spherical and prismatic soil aggregates from unreclaimed post-mining sites

Energy Technology Data Exchange (ETDEWEB)

Frouz, J.; Kristufek, V.; Liveckova, M.; van Loo, D.; Jacobs, P.; Van Hoorebeke, L. [Charles University of Prague, Prague (Czech Republic). Inst. of Environmental Studies

2011-01-15

Soil aggregates between 2 and 5 mm from 35- and 45-year-old unreclaimed post-mining sites near Sokolov (Czech Republic) were divided into two groups: spherical and prismatic. X-ray tomography indicated that prismatic aggregates consisted of fragments of claystone bonded together by amorphous clay and roots while spherical aggregates consisted of a clay matrix and organic fragments of various sizes. Prismatic aggregates were presumed to be formed by plant roots and physical processes during weathering of Tertiary mudstone, while earthworms were presumed to contribute to the formation of spherical aggregates. The effects of drying and rewetting and glucose addition on microbial respiration, microbial biomass, and counts of bacteria in these aggregates were determined. Spherical aggregates contained a greater percentage of C and N and a higher C-to-N ratio than prismatic ones. The C content of the particulate organic matter was also higher in the spherical than in the prismatic aggregates. Although spherical aggregates had a higher microbial respiration and biomass, the growth of microbial biomass in spherical aggregates was negatively correlated with initial microbial biomass, indicating competition between bacteria. Specific respiration was negatively correlated with microbial biomass. Direct counts of bacteria were higher in spherical than in prismatic aggregates. Bacterial numbers were more stable in the center than in the surface layers of the aggregates. Transmission electron microscopy indicated that bacteria often occurred as individual cells in prismatic aggregates but as small clusters of cells in spherical aggregates. Ratios of colony forming units (cultivatable bacteria) to direct counts were higher in spherical than in prismatic aggregates. Spherical aggregates also contained faster growing bacteria.

Soil aggregate and organic carbon distribution at dry land soil and paddy soil: the role of different straws returning.

Science.gov (United States)

Huang, Rong; Lan, Muling; Liu, Jiang; Gao, Ming

2017-12-01

Agriculture wastes returning to soil is one of common ways to reuse crop straws in China. The returned straws are expected to improve the fertility and structural stability of soil during the degradation of straw it selves. The in situ effect of different straw (wheat, rice, maize, rape, and broad bean) applications for soil aggregate stability and soil organic carbon (SOC) distribution were studied at both dry land soil and paddy soil in this study. Wet sieving procedures were used to separate soil aggregate sizes. Aggregate stability indicators including mean weight diameter, geometric mean diameter, mean weight of specific surface area, and the fractal dimension were used to evaluate soil aggregate stability after the incubation of straws returning. Meanwhile, the variation and distribution of SOC in different-sized aggregates were further studied. Results showed that the application of straws, especially rape straw at dry land soil and rice straw at paddy soil, increased the fractions of macro-aggregate (> 0.25 mm) and micro-aggregate (0.25-0.053 mm). Suggesting the nutrients released from straw degradation promotes the growing of soil aggregates directly and indirectly. The application of different straws increased the SOC content at both soils and the SOC mainly distributed at  0.25 and 0.25-0.053 mm aggregates with dry land soil. Rape straw in dry land and rice straw in paddy field could stabilize soil aggregates and increasing SOC contents best.

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

Linkages between aggregate formation, porosity and soil chemical properties

NARCIS (Netherlands)

Regelink, I.C.; Stoof, C.R.; Rousseva, S.; Weng, L.; Lair, G.J.; Kram, P.; Nikolaidis, N.P.; Kercheva, M.; Banwart, S.; Comans, R.N.J.

2015-01-01

Linkages between soil structure and physical–chemical soil properties are still poorly understood due to the wide size-range at which aggregation occurs and the variety of aggregation factors involved. To improve understanding of these processes, we collected data on aggregate fractions, soil

Assessing the dynamics of the upper soil layer relative to soil management practices

Science.gov (United States)

Hatfield, J.; Wacha, K.; Dold, C.

2017-12-01

The upper layer of the soil is the critical interface between the soil and the atmosphere and is the most dynamic in response to management practices. One of the soil properties most reflective to changes in management is the stability of the aggregates because this property controls infiltration of water and exchange of gases. An aggregation model has been developed based on the factors that control how aggregates form and the forces which degrade aggregates. One of the major factors for this model is the storage of carbon into the soil and the interaction with the soil biological component. To increase soil biology requires a stable microclimate that provides food, water, shelter, and oxygen which in turn facilitates the incorporation of organic material into forms that can be combined with soil particles to create stable aggregates. The processes that increase aggregate size and stability are directly linked the continual functioning of the biological component which in turn changes the physical and chemical properties of the soil. Soil aggregates begin to degrade as soon as there is no longer a supply of organic material into the soil. These processes can range from removal of organic material and excessive tillage. To increase aggregation of the upper soil layer requires a continual supply of organic material and the biological activity that incorporates organic material into substances that create a stable aggregate. Soils that exhibit stable soil aggregates at the surface have a prolonged infiltration rate with less runoff and a gas exchange that ensures adequate oxygen for maximum biological activity. Quantifying the dynamics of the soil surface layer provides a quantitative understanding of how management practices affect aggregate stability.

[Research methods of carbon sequestration by soil aggregates: a review].

Science.gov (United States)

Chen, Xiao-Xia; Liang, Ai-Zhen; Zhang, Xiao-Ping

2012-07-01

To increase soil organic carbon content is critical for maintaining soil fertility and agricultural sustainable development and for mitigating increased greenhouse gases and the effects of global climate change. Soil aggregates are the main components of soil, and have significant effects on soil physical and chemical properties. The physical protection of soil organic carbon by soil aggregates is the important mechanism of soil carbon sequestration. This paper reviewed the organic carbon sequestration by soil aggregates, and introduced the classic and current methods in studying the mechanisms of carbon sequestration by soil aggregates. The main problems and further research trends in this study field were also discussed.

Quantifying the contribution of the root system of alpine vegetation in the soil aggregate stability of moraine

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Csilla Hudek

2017-03-01

Full Text Available One fifth of the world's population is living in mountains or in their surrounding areas. This anthropogenic pressure continues to grow with the increasing number of settlements, especially in areas connected to touristic activities, such as the Italian Alps. The process of soil formation on high mountains is particularly slow and these soils are particularly vulnerable to soil degradation. In alpine regions, extreme meteorological events are increasingly frequent due to climate change, speeding up the process of soil degradation and increasing the number of severe erosion processes, shallow landslides and debris flows. Vegetation cover plays a crucial role in the stabilization of mountain soils thereby reducing the risk of natural hazards effecting downslope areas. Soil aggregate stability is one of the main soil properties that can be linked to soil loss processes. Soils developed on moraines in recently deglaciated areas typically have low levels of soil aggregation, and a limited or discontinuous vegetation cover making them more susceptible to degradation. However, soil structure can be influenced by the root system of the vegetation. Roots are actively involved in the formation of water-stable soil aggregation, increasing the stability of the soil and its nutrient content. In the present study, we aim to quantify the effect of the root system of alpine vegetation on the soil aggregate stability of the forefield of the Lys glacier, in the Aosta Valley (NW-Italy. This proglacial area provides the opportunity to study how the root system of ten pioneer alpine species from different successional stages can contribute to soil development and soil stabilization. To quantify the aggregate stability of root permeated soils, a modified wet sieving method was employed. The root length per soil volume of the different species was also determined and later correlated with the aggregate stability results. The results showed that soil aggregate

Assessing the strength of soil aggregates produced by two types of organic matter amendments using the ultrasonic energy

Science.gov (United States)

Zhu, Zhaolong; minasny, Budiman; Field, Damien; Angers, Denis

2017-04-01

The presence of organic matter (OM) is known to stimulate the formation of soil aggregates, but the aggregation strength may vary with different amount and type/quality of OM. Conventionally wet sieving method was used to assess the aggregates' strength. In this study, we wish to get insight of the effects of different types of C inputs on aggregate dynamics using quantifiable energy via ultrasonic agitation. A clay soil with an inherently low soil organic carbon (SOC) content, was amended with two different sources of organic matter (alfalfa, C:N = 16.7 and barley straw, C:N = 95.6) at different input levels (0, 10, 20, & 30 g C kg-1 soil). The soil's inherent macro aggregates were first destroyed via puddling. The soils were incubated in pots at moisture content 70% of field capacity for a period of 3 months. The pots were housed in a 1.2L sealed opaque plastic container. The CO2 generated during the incubation was captured by a vial of NaOH which was placed in each of the sealed containers and sampled per week. At 14, 28, 56, and 84 days, soil samples were collected and the change in aggregation was assessed using a combination of wet sieving and ultrasonic agitation. The relative strength of aggregates exposed to ultrasonic agitation was modelled using the aggregate disruption characteristic curve (ADCC) and soil dispersion characteristic curve (SDCC). Both residue quality and quantity of organic matter input influenced the amount of aggregates formed and their relative strength. The MWD of soils amended with alfalfa residues was greater than that of barley straw at lower input rates and early in the incubation. In the longer term, the use of ultrasonic energy revealed that barley straw resulted in stronger aggregates, especially at higher input rates despite showing similar MWD as alfalfa. The use of ultrasonic agitation, where we quantify the energy required to liberate and disperse aggregates allowed us to differentiate the effects of C inputs on the size of

Aggregate-associated carbon and nitrogen in reclaimed sandy loam soils

Energy Technology Data Exchange (ETDEWEB)

Wick, A.F.; Stahl, P.D.; Ingram, L.J. [Virginia Polytechnic Institute & State University, Blacksburg, VA (United States)

2009-11-15

Minimal research has been conducted on aggregate, C, and N in coarse-textured soils used to reclaim surface coal mine lands. Furthermore, little is known about the contribution different plant communities make to the recovery of aggregation in these soils. Two chronosequences of semiarid reclaimed sites with sandy loam soils were sampled under shrub- and grass-dominated communities. Aggregation, aggregate fractions, and associated C and N were measured. No definitive trends of increasing macroaggregates between sites were observed undershrubs; however, macro- and microaggregation was greater in the 16-yr-old (0.20 and 0.23 kg aggregate kg{sup -1} soil, respectively) than in the 5-yr-old soils (0.02 and 0.08 kg aggregate kg{sup -1} soil, respectively) under grasses. Although C and N concentrations were drastically reduced (50-75%) with mining activity between the <1-yr-old and native soils, aggregate C and N concentrations tinder shrubs and grasses were similar to each other and to the native soils in the 5-yr-old site. Sods under grass in the 16-yr-old site had lower available and aggregate-occluded C and N concentrations than the 5-yr-old site, while C and N concentrations did not change between 5- and 16-yr-old soils under shrubs. Conversely, aggregate C and N pool sizes under shrubs and grasses both increased with site age to conditions similar to those observed in the native soil. Reclaimed shrub site soils had consistently higher C concentrations in the older reclaimed sites (10 and 16 yr old) than the soils under grasses, indicating greater accumulation and retention of C and N in organic material under shrub than grass communities in semiarid reclaimed sites.

Biochar Effects on Soil Aggregate Properties Under No-Till Maize

DEFF Research Database (Denmark)

Khademalrasoul, Ataalah; Naveed, Muhammad; Heckrath, Goswin Johann

2014-01-01

of biochar particles had higher TS and SRE probably because of bonding effects. Based on the improved soil aggregate properties, we suggest that biochar can be effective for increasing and sustaining overall soil quality, for example, related to minimizing the soil erosion potential.......Soil aggregates are useful indicators of soil structure and stability, and the impact on physical and mechanical aggregate properties is critical for the sustainable use of organic amendments in agricultural soil. In this work, we evaluated the short-term soil quality effects of applying biochar (0......–10 kg m−2), in combination with swine manure (2.1 and 4.2 kg m−2), to a no-till maize (Zea mays L.) cropping system on a sandy loam soil in Denmark. Topsoil (0–20 cm) aggregates were analyzed for clay dispersibility, aggregate stability, tensile strength (TS), and specific rupture energy (SRE) using end...

Polycyclic aromatic hydrocarbons (PAHs) in wetland soils under different land uses in a coastal estuary: toxic levels, sources and relationships with soil organic matter and water-stable aggregates.

Science.gov (United States)

Xiao, Rong; Bai, Junhong; Wang, Junjing; Lu, Qiongqiong; Zhao, Qingqing; Cui, Baoshan; Liu, Xinhui

2014-09-01

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in the soils from industrial, wharf, cropland, milldam and natural wetland sites to characterize their distributions, toxic levels and possible sources in the Pearl River Estuary and identify their relationships with soil organic matter (SOM) and water-stable aggregates (WSAs). Our results indicate that the average concentration of total PAHs in this region reached a moderate pollution level, which was higher than that in other larger estuaries in Asia. The average level of total PAHs in industrial soils was 1.2, 1.5, 1.6 and 2.3 times higher than those in soils from wharf, cropland, milldam and natural wetland sites, respectively. Greater accumulation of PAHs occurred in the middle and/or bottom soil layers where 3-ring PAHs were dominant. Industrial soils also exhibited the highest toxic levels with the highest toxic equivalent concentrations of PAHs, followed by wharf and milldam soils, and the cropland and wetland soils had the lowest toxicity. The diagnostic ratios suggested that PAHs primarily originated from biomass and coal combustion at industrial and milldam sites, and petroleum combustion was determined to be the primary source of PAHs at the wharf, cropland and wetland sites. Both 3-ring and 4-ring PAHs in the milldam and wharf soils were significantly positively correlated with the SOM, whereas the 4,5,6-ring PAHs and total PAHs in industrial soils and the 2-ring PAHs in cropland soils were significantly negatively correlated with the SOM. In addition, large WSAs also exhibited a significant positive correlation with PAHs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Pore structure of natural and regenerated soil aggregates

DEFF Research Database (Denmark)

Naveed, Muhammad; Arthur, Emmanuel; de Jonge, Lis Wollesen

2014-01-01

Quantitative characterization of aggregate pore structure can reveal the evolution of aggregates under different land use and management practices and their effects on soil processes and functions. Advances in X-ray Computed Tomography (CT) provide powerful means to conduct such characterization....... This study examined aggregate pore structure of three differently managed same textured Danish soils (mixed forage cropping, MFC; mixed cash cropping, MCC; cereal cash cropping, CCC) for (i) natural aggregates, and (ii) aggregates regenerated after 20 months of incubation. In total, 27 aggregates (8-16 mm...... pore diameter of 200 and 170 Hm, respectively. Pore shape analysis indicated that CCC and MFC aggregates had an abundance of rounded and elongated pores, respectively, and those of MCC were in-between CCC and MFC. Aggregate pore structure development in the lysimeters was nearly similar irrespective...

Total organic carbon in aggregates as a soil recovery indicator

Science.gov (United States)

Luciene Maltoni, Katia; Rodrigues Cassiolato, Ana Maria; Amorim Faria, Glaucia; Dubbin, William

2015-04-01

The soil aggregation promotes physical protection of organic matter, preservation of which is crucial to improve soil structure, fertility and ensure the agro-ecosystems sustainability. The no-tillage cultivation system has been considered as one of the strategies to increase total soil organic carbono (TOC) contents and soil aggregation, both are closely related and influenced by soil management systems. The aim of this study was to evaluate the distribution of soil aggregates and the total organic carbon inside aggregates, with regard to soil recovery, under 3 different soil management systems, i.e. 10 and 20 years of no-tillage cultivation as compared with soil under natural vegetation (Cerrado). Undisturbed soils (0-5; 5-10; and 10-20 cm depth) were collected from Brazil, Central Region. The soils, Oxisols from Cerrado, were collected from a field under Natural Vegetation-Cerrado (NV), and from fields that were under conventional tillage since 1970s, and 10 and 20 years ago were changed to no-tillage cultivation system (NT-10; NT-20 respectively). The undisturbed samples were sieved (4mm) and the aggregates retained were further fractionated by wet sieving through five sieves (2000, 1000, 500, 250, and 50 μm) with the aggregates distribution expressed as percentage retained by each sieve. The TOC was determined, for each aggregate size, by combustion (Thermo-Finnigan). A predominance of aggregates >2000 μm was observed under NV treatment (92, 91, 82 %), NT-10 (64, 73, 61 %), and NT-20 (71, 79, 63 %) for all three depths (0-5; 5-10; 10-20 cm). In addition greater quantities of aggregates in sizes 1000, 500, 250 and 50 μm under NT-10 and NT-20 treatments, explain the lower aggregate stability under these treatments compared to the soil under NV. The organic C concentration for NV in aggregates >2000 μm was 24,4; 14,2; 8,7 mg/g for each depth (0-5; 5-10; 10-20 cm, respectively), higher than in aggregates sized 250-50 μm (7,2; 5,5; 4,4 mg/g) for all depths

Aggregate stability and soil degradation in the tropics

International Nuclear Information System (INIS)

Mbagwu, J.S.C.

2004-01-01

Aggregate stability is a measure of the structural stability of soils. Factors that influence aggregate stability are important in evaluating the ease with which soils erode by water and/or wind, the potential of soils to crust and/or seal, soil permeability, quasi-steady state infiltration rates and seedling emergence and in predicting the capacity of soils to sustain long-term crop production. Aggregate stability of soils can be measured by the wet-sieving or raindrop techniques. A reduction in soil aggregate stability implies an increase in soil degradation. Hence aggregate stability and soil degradation are interwoven. The measures used can either be preventive or remedial. Preventive practices minimize the chances of soil degradation occurring or the magnitude or severity of the damage when the degradation manifests. These include in Nigeria, (i) manuring and mulching, (ii) planted fallows and cover crops, (iii) sustainable farming systems, (iv) adequate rotations, (v) home gardens or compound farms, (vi) alley cropping and related agro forestry systems, and (vii) chemical fertilizers which are mainly remedial measures. Because of alterations in soil properties that affect particular land uses, soils may degrade for one crop (maize rather sorghum). As long as some land use is possible soil degradation is not always an absolute concept. Decline in agricultural productivity should be evaluated in terms of inputs such as fertilizer use, water management and tillage methods. We can alleviate some types of soil degradation by use of micronutrients, inorganic fertilizers and organic residues. Soil that responds to management practices cannot be said to be degraded. Since crop growth depends on weather, degraded soils may be more sensitive to harsh weather (e.g. drought, temperature) than undegraded soils. A soil is degraded if its productivity falls below the economic threshold even under favourable weather conditions or with judicious inputs. All human

Material dynamics in polluted soils with different structures - comparative investigations of general soil and aggregates

International Nuclear Information System (INIS)

Taubner, H.

1992-01-01

In structured soils, a small-scale heterogeneity of physical and chemical properties will develop which results in a reduced availability of the reaction sites of the soil matrix. In view of the lack of knowledge on the conditions within the individual aggregates were carried out for characterizing the aggregates and comparing them with the soil in, general soil samples were taken from natural structure of a podzolic soil and a podazolic brown earth from two sites in the Fichtelgebirge mountains as well as a parabraun earth from East Holstein. The horizons differed with regard to their texture and structure; silty material tends to have a subpolyhedral structure and calyey material a polyhedral structure. The general soil samples and aggregate samples from the three B horizons were subjected, with comparable experimental conditions, to percolation experiments inducing a multiple acid load. The soil solution from the secondary pore system and aggregate pore system is more heterogeneus for the higher-structured subpolyhedral texture of the perdzolic soil than for the less strongly aggregated subpolyhedral structured of the podzolic brown earth. (orig.) [de

Infiltration Variability in Agricultural Soil Aggregates Caused by Air Slaking

Science.gov (United States)

Korenkova, L.; Urik, M.

2018-04-01

This article reports on variation in infiltration rates of soil aggregates as a result of phenomenon known as air slaking. Air slaking is caused by the compression and subsequent escape of air captured inside soil aggregates during water saturation. Although it has been generally assumed that it occurs mostly when dry aggregates are rapidly wetted, the measurements used for this paper have proved that it takes place even if the wetting is gradual, not just immediate. It is a phenomenon that contributes to an infiltration variability of soils. In measuring the course of water flow through the soil, several small aggregates of five agricultural soils were exposed to distilled water at zero tension in order to characterize their hydraulic properties. Infiltration curves obtained for these aggregates demonstrate the effect of entrapped air on the increase and decrease of infiltration rates. The measurements were performed under various moisture conditions of the A-horizon aggregates using a simple device.

Phosphorus content as a function of soil aggregate size and paddy cultivation in highly weathered soils.

Science.gov (United States)

Li, Baozhen; Ge, Tida; Xiao, Heai; Zhu, Zhenke; Li, Yong; Shibistova, Olga; Liu, Shoulong; Wu, Jinshui; Inubushi, Kazuyuki; Guggenberger, Georg

2016-04-01

Red soils are the major land resource in subtropical and tropical areas and are characterized by low phosphorus (P) availability. To assess the availability of P for plants and the potential stability of P in soil, two pairs of subtropical red soil samples from a paddy field and an adjacent uncultivated upland were collected from Hunan Province, China. Analysis of total P and Olsen P and sequential extraction was used to determine the inorganic and organic P fractions in different aggregate size classes. Our results showed that the soil under paddy cultivation had lower proportions of small aggregates and higher proportions of large aggregates than those from the uncultivated upland soil. The portion of >2-mm-sized aggregates increased by 31 and 20 % at Taoyuan and Guiyang, respectively. The total P and Olsen P contents were 50-150 and 50-300 % higher, respectively, in the paddy soil than those in the upland soil. Higher inorganic and organic P fractions tended to be enriched in both the smallest and largest aggregate size classes compared to the middle size class (0.02-0.2 mm). Furthermore, the proportion of P fractions was higher in smaller aggregate sizes (2 mm). In conclusion, soils under paddy cultivation displayed improved soil aggregate structure, altered distribution patterns of P fractions in different aggregate size classes, and to some extent had enhanced labile P pools.

Long-term manure amendments reduced soil aggregate stability via redistribution of the glomalin-related soil protein in macroaggregates

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Xie, Hongtu; Li, Jianwei; Zhang, Bin; Wang, Lianfeng; Wang, Jingkuan; He, Hongbo; Zhang, Xudong

2015-01-01

Glomalin-related soil protein (GRSP) contributes to the formation and maintenance of soil aggregates, it is however remains unclear whether long-term intensive manure amendments alter soil aggregates stability and whether GRSP regulates these changes. Based on a three-decade long fertilization experiment in northeast China, this study examined the impact of long-term manure input on soil organic carbon (SOC), total and easily extractable GRSP (GRSPt and GRSPe) and their respective allocations in four soil aggregates (>2000 μm; 2000–250 μm; 250–53 μm; and soil and SOC in each aggregate generally increased with increasing manure input, GRSPt and GRSPe in each aggregate showed varying changes with manure input. Both GRSP in macroaggregates (2000–250 μm) were significantly higher under low manure input, a pattern consistent with changes in soil aggregate stability. Constituting 38~49% of soil mass, macroaggregates likely contributed to the nonlinear changes of aggregate stability under manure amendments. The regulatory process of GRSP allocations in soil aggregates has important implications for manure management under intensive agriculture. PMID:26423355

Group living in squamate reptiles: a review of evidence for stable aggregations.

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Gardner, Michael G; Pearson, Sarah K; Johnston, Gregory R; Schwarz, Michael P

2016-11-01

How sociality evolves and is maintained remains a key question in evolutionary biology. Most studies to date have focused on insects, birds, and mammals but data from a wider range of taxonomic groups are essential to identify general patterns and processes. The extent of social behaviour among squamate reptiles is under-appreciated, yet they are a promising group for further studies. Living in aggregations is posited as an important step in the evolution of more complex sociality. We review data on aggregations among squamates and find evidence for some form of aggregations in 94 species across 22 families. Of these, 18 species across 7 families exhibited 'stable' aggregations that entail overlapping home ranges and stable membership in long-term (years) or seasonal aggregations. Phylogenetic analysis suggests that stable aggregations have evolved multiple times in squamates. We: (i) identify significant gaps in our understanding; (ii) outline key traits which should be the focus of future research; and (iii) outline the potential for utilising reproductive skew theory to provide insights into squamate sociality. © 2015 Cambridge Philosophical Society.

Intra-aggregate CO2 enrichment: a modelling approach for aerobic soils

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Schlotter, D.; Schack-Kirchner, H.

2013-02-01

CO2 concentration gradients inside soil aggregates, caused by the respiration of soil microorganisms and fungal hyphae, might lead to variations in the soil solution chemistry on a mm-scale, and to an underestimation of the CO2 storage. But, up to now, there seems to be no feasible method for measuring CO2 inside natural aggregates with sufficient spatial resolution. We combined a one-dimensional model for gas diffusion in the inter-aggregate pore space with a cylinder diffusion model, simulating the consumption/production and diffusion of O2 and CO2 inside soil aggregates with air- and water-filled pores. Our model predicts that for aerobic respiration (respiratory quotient = 1) the intra-aggregate increase in the CO2 partial pressure can never be higher than 0.9 kPa for siliceous, and 0.1 kPa for calcaric aggregates, independent of the level of water-saturation. This suggests that only for siliceous aggregates CO2 produced by aerobic respiration might cause a high small-scale spatial variability in the soil solution chemistry. In calcaric aggregates, however, the contribution of carbonate species to the CO2 transport should lead to secondary carbonates on the aggregate surfaces. As regards the total CO2 storage in aerobic soils, both siliceous and calcaric, the effect of intra-aggregate CO2 gradients seems to be negligible. To assess the effect of anaerobic respiration on the intra-aggregate CO2 gradients, the development of a device for measuring CO2 on a mm-scale in soils is indispensable.

Seasonal variability of soil aggregate stability

Czech Academy of Sciences Publication Activity Database

Rohošková, M.; Kodešová, R.; Jirků, V.; Žigová, Anna; Kozák, J.

2009-01-01

Roč. 11, - (2009), , , EGU2009-6341-3-EGU2009-6341-3 ISSN 1029-7006. [European Geosciences Union General Assembly. 19.04.2009-24.04.2009, Vienna] R&D Projects: GA ČR GA526/08/0434 Institutional research plan: CEZ:AV0Z30130516 Keywords : seasonal variability * soil aggregate stability * soil types Subject RIV: DF - Soil Science

Texture-contrast profile development across the prairie-forest ecotone in northern Minnesota, USA, and its relation to soil aggregation and clay dispersion.

Science.gov (United States)

Kasmerchak, C. S.; Mason, J. A.

2016-12-01

Along the prairie-forest ecotone, Alfisols with distinct clay-enriched B horizons are found under forest, established only within the past 4 ka, including outlying patches of prairie groves surrounded by prairie. Grassland soils only 5-10 km away from the vegetation boundary show much weaker texture-contrast. In order for clay to be dispersed it must first be released from aggregates upper horizons, which occurs when exposed top soil undergoes wetting and mechanical stress. The relationship between physiochemical soil characteristics and soil aggregation/clay dispersion is of particular interest in explaining texture-contrast development under forest. Soil samples were collected along a transect in northern Minnesota on gentle slopes in similar glacial sediment. Aggregate stability experiments show Mollisol A and B horizons have the most stable aggregates, while Alfisol E horizons have the weakest aggregates and disintegrate rapidly. This demonstrates the strong influence of OM and exchange chemistry on aggregation. Analysis of other physiochemical soil characteristics such as base saturation and pH follow a gradual decreasing eastward trend across the study sites, and do not abruptly change at the prairie-forest boundary like soil morphology does. Linear models show the strongest relationship between rapid aggregate disintegration and ECEC, although they only explain 47-50% of the variance. Higher surface charge enhances aggregation by allowing for greater potential of cation bridging between OM and clay particles. ECEC also represents multiple soil characteristics such as OC, clay, mineralogy, and carbonate presence, suggesting the relationship between aggregation stability and soil characteristics is not simple. Given the parent material consists of calcareous glacial sediment, abundant Ca2+ and Mg2+ from carbonates weathering also contributes to enhanced aggregation in upper horizons. Differences in the rates of bioturbation, most likely also contribute

Effects of Pedogenic Fe Oxides on Soil Aggregate-Associated Carbon

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Asefaw Berhe, A.; Jin, L.

2017-12-01

Carbon sequestration is intimately related to the soil structure, mainly soil aggregate dynamics. Carbon storage in soil aggregates has been recognized as an important carbon stabilization mechanism in soils. Organic matter and pedogenic Fe oxides are major binding agents that facilitate soil aggregate formation and stability. However, few studies have investigated how different forms of pedogenic Fe oxides can affect soil carbon distribution in different aggregate-size fractions. We investigated sequentially extracted pedogenic Fe oxides (in the order of organically complexed Fe extracted with sodium pyrophosphate, poorly-crystalline Fe oxides extracted with hydroxylamine hydrochloride, and crystalline Fe oxides extracted with dithionite hydrochloride) and determined the amount and nature of C in macroaggregates (2-0.25mm), microaggregates (0.25-0.053mm), and two silt and clay fractions (0.053-0.02mm, and soil from Sierra Nevada mountain in California. We also determined how pedogenic Fe oxides affect soil carbon distribution along soil depth gradients. Findings of our study revealed that the proportion of organic matter complexed Fe decreased, but the proportion of crystalline Fe increased with increasing soil depths. Poorly crystalline Fe oxides (e.g. ferrihydrite) was identified as a major Fe oxide in surface soil, whereas crystalline Fe oxides (e.g. goethite) were found in deeper soil layers. These results suggest that high concentration of organic matter in surface soil suppressed Fe crystallization. Calcium cation was closely related to the pyrophosphate extractable Fe and C, which indicates that calcium may be a major cation that contribute to the organic matter complexed Fe and C pool. Increasing concentrations of extractable Fe and C with decreasing aggregate size fractions also suggests that Fe oxides play an important role in formation and stability of silt and clay fractions, and leading to further stabilization of carbon in soil. Our findings provide

Effects of vegetation restoration on the aggregate stability and distribution of aggregate-associated organic carbon in a typical karst gorge region

Science.gov (United States)

Tang, F. K.; Cui, M.; Lu, Q.; Liu, Y. G.; Guo, H. Y.; Zhou, J. X.

2015-08-01

Changes in soil utilization significantly affect aggregate stability and aggregate-associated soil organic carbon (SOC). A field investigation and indoor analysis were conducted in order to study the soil aggregate stability and organic carbon distribution in the water-stable aggregates (WSA) of the bare land (BL), grassland (GL), shrubland (SL), and woodland (WL) in a typical karst gorge region. The results indicated that the BL, GL, SL, and WL were dominated by particles with sizes > 5 mm under dry sieving treatment, and that the soil aggregate contents of various sizes decreased as the particle size decreased. In addition, the BL, GL, SL, and WL were predominantly comprised of WSA sieving treatment, and that the WSA contents initially increased, then decreased, and then increased again as the particle size decreased. Furthermore, at a soil depth of 0-60 cm, the mean weight diameter (MWD), geometrical mean diameter (GMD), and fractal dimensions (D) of the dry aggregates and water-stable aggregates in the different types of land were ranked, in descending order, as WL > GL > SL > BL. The contents of WSA > 0.25 mm, MWD and GMD increased significantly, in that order, and the percentage of aggregate destruction (PAD) and fractal dimensions decreased significantly as the soil aggregate stability improved. The results of this study indicated that, as the SOC contents increased after vegetation restoration, the average SOC content of WL was 2.35, 1.37, and 1.26 times greater than that in the BL, GL, and SL, respectively. The total SOC and SOC associated in WSA of various sizes were the highest at a soil depth of 0-20 cm. In addition, the SOC contents of the WSA increased as the soil aggregate sizes decreased. The SOC contents of the WSA aggregates aggregate SOC contents. The woodland and grassland facilitated WSA stability and SOC protection, thus, promoting the natural restoration of vegetation by reducing artificial disturbances could effectively restore the ecology

Aggregation and C dynamics along an elevation gradient in carbonate-containing grassland soils of the Alps

Science.gov (United States)

Garcia-Franco, Noelia; Wiesmeier, Martin; Kiese, Ralf; Dannenmann, Michael; Wolf, Benjamin; Zistl-Schlingmann, Marcus; Kögel-Knabner, Ingrid

2017-04-01

C sequestration in mountainous grassland soils is regulated by physical, chemical and biological soil process. An improved knowledge of the relationship between these stabilization mechanisms is decisive to recommend the best management practices for climate change mitigation. In this regard, the identification of a successful indicator of soil structural improvement and C sequestration in mountainous grassland soils is necessary. Alpine and pre-alpine grassland soils in Bavaria represent a good example for mountainous grassland soils faced with climate change. We sampled grassland soils of the northern limestone alps in Bavaria along an elevation gradient from 550 to 1300 m above sea level. We analyzed C dynamics by a comparative analysis of the distribution of C according to aggregate size classes: large-macroaggregates (> 2000 µm), small-macroaggregates (250-2000 µm), microaggregates (63-250 µm), silt plus clay particles (soil. Our preliminary results showed higher C content and changed water-stable aggregate distribution in the high elevation sites compared to lower elevations. Magnesium carbonate seem to play an important role in stabilizing macroaggregates formed from fresh OM. In addition, the isolation of occluded microaggregates within macroaggregates will help us to improve our understanding on the effects of climate change on soil structure and on the sensitivity of different C stabilization mechanisms present in mountainous soils.

Nature and origin of the resistant carbonaceous polymorphs involved the fossilization of biogenic soil-aggregates

Science.gov (United States)

Courty, M.-A.

2012-04-01

which are all finely imbricated with phosphides, phosphates, sulphides, sulphates and native metals (Fe-Cr-Ni and Fe-Cr alloys, Ni, Al, Cu, Zn, Pb, As, Sn, Ag, Au, Bi). The 3D observations show that the carbonaceous filaments play a major role in the cohesion of the fine fraction. The carbonaceous components only start to decompose under HF attack and from 400°C heating. They do not display evidence of microbial degradation. The biogenic aggregates with high amount of carbonaceous polymorphs appear to have resisted to cryoturbation and to hard setting under water saturation. Biogenic micro-aggregates from present-day top soils only contain rare exotic components. In contrast to the ones of the soil archives, they display highly variable structural stability depending upon local edaphic conditions. The exotic assemblage of the stable biogenic micro-aggregates from the soil archives is shown to be similar to the range of terrestrial aerosols that are associated to meteor explosion (Courty et al., this volume). This suggests that the fossilized organic-rich surface horizons in soil archives would trace singular situations possibly marked by recurrent meteor explosion with high stratospheric aerosol production. Mechanisms explaining how the dual stratospheric/cosmic processes formed resistant carbon species from fossil combustible precursors yet remain to be investigated. Courty, Benoît and Vaillant (2012). Possible interaction of meteor explosion with stratospheric aerosols on cloud nucleation based on 2011 observations. Geophysical Research Abstracts Vol. 14, EGU2012.

Soil aggregate stability as an indicator for eco-engineering effectiveness?

Science.gov (United States)

Graf, Frank

2015-04-01

Eco-engineering aims at stabilising soil and slopes by applying technical and biological measures. Engineering structures are commonly well defined, immediately usable and operative, and their stability effects quantifiable and verifiable. Differently, the use of plants requires more restrictive boundary conditions and the protection potential is rarely easily calculable and develop-ing as a function of growth rate. Although the use of vegetation is widely appreciated and their stabilising effect recognised, there is an increasing demand on sound facts on its efficiency, in particular, in relation to time. Conclusively, a certain necessity has been recognised to monitor, assess and quantify the effectiveness of ecological restora-tion measures in order to facilitate the transfer of technology and knowledge. Recent theoretical models emphasize the im-portance of taking an integrated monitoring approach that considers multiple variables. However, limited financial and time resources often prevent such comprehensive assessments. A solution to this problem may be to use integrated indicators that reflect multiple aspects and, therefore, allow extensive information on ecosystem status to be gathered in a relatively short time. Among various other indicators, such as fractal dimension of soil particle size distribution or microbiological parameters, soil aggregate stability seems the most appropriate indicator with regard to protecting slopes from superficial soil failure as it is critical to both plant growth and soil structure. Soil aggregation processes play a crucial role in re-establishing soil structure and function and, conclusively, for successful and sustainable re-colonisation. Whereas the key role of soil aggregate stability in ecosystem functioning is well known concerning water, gas, and nutrient fluxes, only limited information is available with regard to soil mechanical and geotechnical aspects. Correspondingly, in the last couple of years several studies

Aggregate and soil organic carbon dynamics in South Chilean Andisols

Directory of Open Access Journals (Sweden)

D. Huygens

2005-01-01

Full Text Available Extreme sensitivity of soil organic carbon (SOC to climate and land use change warrants further research in different terrestrial ecosystems. The aim of this study was to investigate the link between aggregate and SOC dynamics in a chronosequence of three different land uses of a south Chilean Andisol: a second growth Nothofagus obliqua forest (SGFOR, a grassland (GRASS and a Pinus radiata plantation (PINUS. Total carbon content of the 0-10cm soil layer was higher for GRASS (6.7 kg C m-2 than for PINUS (4.3 kg C m-2, while TC content of SGFOR (5.8 kg C m-2 was not significantly different from either one. High extractable oxalate and pyrophosphate Al concentrations (varying from 20.3-24.4 g kg-1, and 3.9-11.1 g kg-1, respectively were found in all sites. In this study, SOC and aggregate dynamics were studied using size and density fractionation experiments of the SOC, δ13C and total carbon analysis of the different SOC fractions, and C mineralization experiments. The results showed that electrostatic sorption between and among amorphous Al components and clay minerals is mainly responsible for the formation of metal-humus-clay complexes and the stabilization of soil aggregates. The process of ligand exchange between SOC and Al would be of minor importance resulting in the absence of aggregate hierarchy in this soil type. Whole soil C mineralization rate constants were highest for SGFOR and PINUS, followed by GRASS (respectively 0.495, 0.266 and 0.196 g CO2-Cm-2d-1 for the top soil layer. In contrast, incubation experiments of isolated macro organic matter fractions gave opposite results, showing that the recalcitrance of the SOC decreased in another order: PINUS>SGFOR>GRASS. We deduced that electrostatic sorption processes and physical protection of SOC in soil aggregates were the main processes determining SOC stabilization. As a result, high aggregate carbon concentrations, varying from 148 till 48 g kg-1, were encountered for all land use

Modeling of Soil Aggregate Stability using Support Vector Machines and Multiple Linear Regression

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Ali Asghar Besalatpour

2016-02-01

Full Text Available Introduction: Soil aggregate stability is a key factor in soil resistivity to mechanical stresses, including the impacts of rainfall and surface runoff, and thus to water erosion (Canasveras et al., 2010. Various indicators have been proposed to characterize and quantify soil aggregate stability, for example percentage of water-stable aggregates (WSA, mean weight diameter (MWD, geometric mean diameter (GMD of aggregates, and water-dispersible clay (WDC content (Calero et al., 2008. Unfortunately, the experimental methods available to determine these indicators are laborious, time-consuming and difficult to standardize (Canasveras et al., 2010. Therefore, it would be advantageous if aggregate stability could be predicted indirectly from more easily available data (Besalatpour et al., 2014. The main objective of this study is to investigate the potential use of support vector machines (SVMs method for estimating soil aggregate stability (as quantified by GMD as compared to multiple linear regression approach. Materials and Methods: The study area was part of the Bazoft watershed (31° 37′ to 32° 39′ N and 49° 34′ to 50° 32′ E, which is located in the Northern part of the Karun river basin in central Iran. A total of 160 soil samples were collected from the top 5 cm of soil surface. Some easily available characteristics including topographic, vegetation, and soil properties were used as inputs. Soil organic matter (SOM content was determined by the Walkley-Black method (Nelson & Sommers, 1986. Particle size distribution in the soil samples (clay, silt, sand, fine sand, and very fine sand were measured using the procedure described by Gee & Bauder (1986 and calcium carbonate equivalent (CCE content was determined by the back-titration method (Nelson, 1982. The modified Kemper & Rosenau (1986 method was used to determine wet-aggregate stability (GMD. The topographic attributes of elevation, slope, and aspect were characterized using a 20-m

Effects of Combined Application of Biogas Slurry and Chemical Fertilizer on Soil Aggregation and C/N Distribution in an Ultisol

Science.gov (United States)

Zheng, Xuebo; Fan, Jianbo; Xu, Lei; Zhou, Jing

2017-01-01

Unreasonable use of chemical fertilizer (CF) on agricultural soil leads to massive losses of soil organic carbon (SOC) and total nitrogen (TN) in tropical and subtropical areas, where soil conditions are unfavorable for aggregate formation. This study evaluated the effects of combined application of biogas slurry (BS) plus CF on soil aggregation and aggregate—associated C/N concentration and storage in an Ultisol. Six treatments included: no fertilizer (T1), CF only (T2), partial (15% (T3), 30% (T4) and 45% (T5)) substitution of TN with BS and BS only (T6). Soil mechanical—stable aggregates (MSAs) formation and stability as well as MSAs—associated C/N concentration and storage were observed in different aggregate sizes (>5, 5–2, 2–1, 1.0–0.5, 0.50–0.25 and 5 mm significantly increased with BS substitution (T5), while the proportions of MSAs 1.0–0.5 mm, MSAs 0.50–0.25 mm and MSAs 0.5 mm that constituted 72–82% of MSAs. Stepwise regression analysis showed that MSAs >5 mm, SOC in MSAs >5 mm and TN in MSAs >5 mm were the dominant variables affecting aggregate stability. Meanwhile SOC in MSAs <0.25 mm and TN in MSAs 2–1 mm were independent variables affecting SOC and TN concentrations in bulk soils. Therefore, certain rate of combined application of BS plus CF is an effective, eco—friendly way to improve soil quality in an Ultisol. PMID:28125647

Aggregate stability in soils cultivated with eucalyptus

Science.gov (United States)

Eucalyptus cultivation has increased in many Brazilian regions. In order to recommend good management practices, it is necessary to understand changes in soil properties where eucalyptus is planted. Aggregate stability analyses have proved to be a useful tool to measure soil effects caused by change...

Effects of tillage on contents of organic carbon, nitrogen, water-stable aggregates and light fraction for four different long-term trials

Science.gov (United States)

Andruschkewitsch, R.; Geisseler, D.; Koch, H.-J.; Ludwig, B.

2012-04-01

Despite increasing interest in tillage techniques as a factor affecting organic carbon (Corg) dynamics and stabilization mechanisms little is known about the underlying processes. Our objectives were (i) to quantify the impact of different tillage treatments on the amount and distribution of of labile Corg pools, on the water-stable macro-aggregate (>250 µm) contents and on organic carbon (Corg) storage and (ii) to quantify the ability of soils under different tillage treatments, light fraction (LF) inputs and clay contents in macro-aggregate formation. Therefore four long-term tillage trials on loess soil in Germany with regular conventional tillage (CT, to 30 cm), mulch tillage (MT, to 10 cm), and no-tillage (NT) treatments. Samples were taken in 0-5 cm, 5-25 cm and 25-40 cm depth after 18-25 years of different tillage treatments and investigated on free and occluded LF (fLF and oLF, respectively) and on macro-aggregate contents. Furthermore an incubation experiment for the quantifcation of macro-aggregate formation was conducted. Macro-aggregates in soils from CT and NT treatments (0-5 and 5-25 cm soil depth) were destroyed and different amounts of light fraction (LF) and clay were applied. The four long-term tillage trials, differing in texture and climatic conditions, revealed consistent results in Corg storage among each other. Based on the equivalent soil mass approach (CT: 0-40, MT: 0-38, NT: 0-36 cm) the Corg stocks in the sampled profile were significantly higher for the MT treatment than for the CT and NT treatments. Significantly lower Corg, fLF, oLF, and macro-aggregate contents for the soils under CT treatment in comparison with the soils under NT and MT treatments were restricted on the top 5 cm. The correlation of the macro-aggregate content against the fLF and oLF contents suggested that the macro-aggregate content is influenced to a lesser extent directly by the physical impact of the different tillage treatments but by the contents of available

Applicability of recycled aggregates in concrete piles for soft soil improvement.

Science.gov (United States)

Medeiros-Junior, Ronaldo A; Balestra, Carlos Et; Lima, Maryangela G

2017-01-01

The expressive generation of construction and demolition waste is stimulating several studies for reusing this material. The improvement of soft soils by concrete compaction piles has been widely applied for 40 years in some Brazilian cities. This technique is used to improve the bearing capacity of soft soils, allowing executing shallow foundations instead of deep foundations. The compaction piles use a high volume of material. This article explored the possibility of using recycled aggregates from construction waste to replace the natural aggregates in order to improve the bearing capacity of the soft soil, regarding its compressive strength. Construction wastes from different stages of a construction were used in order to make samples of concrete with recycled aggregates. The strength of concretes with natural aggregates was compared with the strength of concretes with recycled (fine and coarse) aggregates. Results show that all samples met the minimum compressive strength specified for compaction piles used to improve the bearing capacity of soft soils. The concrete with recycled aggregate from the structural stage had even higher resistances than the concrete with natural aggregates. This behaviour was attributed to the large amount of cementitious materials in the composition of this type of concrete. It was also observed that concrete with recycled fine aggregate has a superior resistance to concrete with recycled coarse aggregate.

Arbuscular mycorrhizal fungi make a complex contribution to soil aggregation

Science.gov (United States)

McGee, Peter; Daynes, Cathal; Damien, Field

2013-04-01

Soil aggregates contain solid and fluid components. Aggregates develop as a consequence of the organic materials, plants and hyphae of arbuscular mycorrhizal (AM) fungi acting on the solid phase. Various correlative studies indicate hyphae of AM fungi enmesh soil particles, but their impact on the pore space is poorly understood. Hyphae may penetrate between particles, remove water from interstitial spaces, and otherwise re-arrange the solid phase. Thus we might predict that AM fungi also change the pore architecture of aggregates. Direct observations of pore architecture of soil, such as by computer-aided tomography (CT), is difficult. The refractive natures of solid and biological material are similar. The plant-available water in various treatments allows us to infer changes in pore architecture. Our experimental studies indicate AM fungi have a complex role in the formation and development of aggregates. Soils formed from compost and coarse subsoil materials were planted with mycorrhizal or non-mycorrhizal seedlings and the resultant soils compared after 6 or 14 months in separate experiments. As well as enmeshing particles, AM fungi were associated with the development of a complex pore space and greater pore volume. Even though AM fungi add organic matter to soil, the modification of pore space is not correlated with organic carbon. In a separate study, we visualised hyphae of AM fungi in a coarse material using CT. In this study, hyphae appeared to grow close to the surfaces of particles with limited ramification across the pore spaces. Hyphae of AM fungi appear to utilise soil moisture for their growth and development of mycelium. The strong correlation between moisture and hyphae has profound implications for soil aggregation, plant utilisation of soil water, and the distribution of water as water availability declines.

Temporal dynamics for soil aggregates determined using X-ray CT scanning

DEFF Research Database (Denmark)

Garbout, Amin; Munkholm, Lars Juhl; Hansen, Søren Baarsgaard

2013-01-01

Soil structure plays a key role in the ability of soil to fulfil essential soil functions and services in relation to e.g. root growth, gas and water transport and organic matter turnover. However, soils are not a very easy object to study as they are highly complex and opaque to the human eye...... aggregate properties such as volume, surface area and sphericity based on 3D images. We tested the methods on aggregates from different treatments and quantified changes over time. A total of 32 collections of aggregates, enclosed in mesocosms, were incubated in soil to follow the structural changes over....... Traditionally, they have been studied using invasive or destructive techniques. The advantage of using X-ray computed tomography (CT) in soil morphology is that it enables non-destructive quantification of soil structure in three dimensions (3D). The prime objective of the present study was to characterize soil...

Micro nutrient status and their distribution in aggregate-size fractions ...

African Journals Online (AJOL)

Micro nutrients are particularly sensitive to changes in land use and their availability in soil is influenced by their distribution and storage in stable aggregate fractions. Micro nutrient, (Fe, Mn and Zn) status and their storage in stable aggregate-size fractions in forested, rubber plantation, oil palm plantation, plantain plantation ...

Clay minerals, metallic oxides and oxy-hydroxides and soil organic carbon distribution within soil aggregates in temperate forest soils

Science.gov (United States)

Gartzia-Bengoetxea, Nahia; Fernández-Ugalde, Oihane; Virto, Iñigo; Arias-González, Ander

2017-04-01

Soil mineralogy is of primary importance for key environmental services provided by soils like carbon sequestration. However, current knowledge on the effects of clay mineralogy on soil organic carbon (SOC) stabilization is based on limited and conflicting data. In this study, we investigated the relationship between clay minerals, metallic oxides and oxy-hydroxides and SOC distribution within soil aggregates in mature Pinus radiata D.Don forest plantations. Nine forest stands located in the same geographical area of the Basque Country (North of Spain) were selected. These stands were planted on different parent material (3 on each of the following: sandstone, basalt and trachyte). There were no significant differences in climate and forest management among them. Moreover, soils under these plantations presented similar content of clay particles. We determined bulk SOC storage, clay mineralogy, the content of Fe-Si-Al-oxides and oxyhydroxides and the distribution of organic C in different soil aggregate sizes at different soil depths (0-5 cm and 5-20 cm). The relationship between SOC and abiotic factors was investigated using a factor analysis (PCA) followed by stepwise regression analysis. Soils developed on sandstone showed significantly lower concentration of SOC (29 g C kg-1) than soils developed on basalts (97 g C kg-1) and trachytes (119 g C kg-1). The soils on sandstone presented a mixed clay mineralogy dominated by illite, with lesser amounts of hydroxivermiculite, hydrobiotite and kaolinite, and a total absence of interstratified chlorite/vermiculite. In contrast, the major crystalline clay mineral identified in the soils developed on volcanic rocks was interstratified chlorite/vermiculite. Nevertheless, no major differences were observed between basaltic and trachytic soils in the clay mineralogy. The selective extraction of Fe showed that the oxalate extractable iron was significantly lower in soils on sandstone (3.7%) than on basalts (11.2%) and

The stability of soil aggregates in tilled fallow areas in Hyderabad district, Pakistan

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Tagar Ahmed

2015-12-01

Full Text Available Arid areas are particularly susceptible to soil erosion due to long dry periods and sudden heavy downpours. This study investigates the aggregate size distribution and aggregate stability of twelve tilled fallow areas of Hyderabad district, Sindh, Pakistan. This study determined aggregate size distribution by dry sieving to evaluate the seedbed condition and aggregate stability using wet sieving to assess the susceptibility of tilled fallow areas to soil erosion. The aggregate size distribution of the soils of the selected areas was highly variable. Gulistan-e-Sarmast had the largest number of clods (51.0% followed by Kohsar (49.0%, Latifabad # 10 (41.10% and Daman-e-Kohsar (39.0%. Fazal Sun City, the left side of the Indus River, the Village Nooral Detha and the left side of the Abdullah Sports city had a greater number of large (>8.0 mm and small aggregates (<0.5 mm. The optimum aggregate size distribution was found in the left side of the channel, which had the largest number of aggregates (50.50% in the 0.5–8.0 mm sieve size range. Maximum aggregate stability (AS was found in Gulistan-e-Sarmast (46%, Kohsar (42% and Latifabad # 10 (34%, while all other soils had minimum aggregate stability (<14%. The minimum aggregate stabilities demonstrate that the tilled fallow areas of Hyderabad district are highly susceptible to erosion. Therefore, the present study suggests investigating potential ways to enhance the aggregate stabilities of soils.

Roundup Ready soybean gene concentrations in field soil aggregate size classes.

Science.gov (United States)

Levy-Booth, David J; Gulden, Robert H; Campbell, Rachel G; Powell, Jeff R; Klironomos, John N; Pauls, K Peter; Swanton, Clarence J; Trevors, Jack T; Dunfield, Kari E

2009-02-01

Roundup Ready (RR) soybeans containing recombinant Agrobacterium spp. CP4 5-enol-pyruvyl-shikimate-3-phosphate synthase (cp4 epsps) genes tolerant to the herbicide glyphosate are extensively grown worldwide. The concentration of recombinant DNA from RR soybeans in soil aggregates was studied due to the possibility of genetic transformation of soil bacteria. This study used real-time PCR to examine the concentration of cp4 epsps in four field soil aggregate size classes (>2000 microm, 2000-500 microm, 500-250 microm and 2000 mum fraction contained between 66.62% and 99.18% of total gene copies, although it only accounted for about 30.00% of the sampled soil. Aggregate formation may facilitate persistence of recombinant DNA.

Influence of pore structure on carbon retention/loss in soil macro-aggregates

Science.gov (United States)

Quigley, Michelle; Kravchenko, Alexandra; Rivers, Mark

2017-04-01

Carbon protection within soil macro-aggregates is an important component of soil carbon sequestration. Pores, as the transportation network for microorganisms, water, air and nutrients within macro-aggregates, are among the factors controlling carbon protection through restricting physical accessibility of carbon to microorganisms. The understanding of how the intra-aggregate pore structure relates to the degree of carbon physical protection, however, is currently lacking. This knowledge gap can lead to potentially inaccurate models and predictions of soil carbon's fate and storage in future changing climates. This study utilized the natural isotopic difference between C3 and C4 plants to trace the location of newly added carbon within macro-aggregates before and after decomposition and explored how location of this carbon relates to characteristics of intra-aggregate pores. To mimic the effect of decomposition, aggregates were incubated at 23˚ C for 28 days. Computed micro-tomographic images were used to determine pore characteristics at 6 μm resolution before and after incubation. Soil (0-10 cm depth) from a 20 year continuous corn (C4 plant) experiment was used. Two soil treatments were considered: 1) "destroyed-structure", where 1 mm sieved soil was used and 2) "intact-structure", where intact blocks of soil were used. Cereal rye (Secale cereale L.) (C3 plant) was grown in the planting boxes (2 intact, 3 destroyed, and one control) for three months in a greenhouse. From each box, ˜5 macro-aggregates of ˜5 mm size were collected for a total of 27 macro-aggregates. Half of the aggregates were cut into 5-11 sections, with relative positions of the sections within the aggregate recorded, and analyzed for δ13C. The remaining aggregates were incubated and then subjected to cutting and δ13C analysis. While there were no significant differences between the aggregate pore size distributions of the two treatments, the roles that specific pores sizes played in

Impact of Spatial Soil and Climate Input Data Aggregation on Regional Yield Simulations.

Science.gov (United States)

Hoffmann, Holger; Zhao, Gang; Asseng, Senthold; Bindi, Marco; Biernath, Christian; Constantin, Julie; Coucheney, Elsa; Dechow, Rene; Doro, Luca; Eckersten, Henrik; Gaiser, Thomas; Grosz, Balázs; Heinlein, Florian; Kassie, Belay T; Kersebaum, Kurt-Christian; Klein, Christian; Kuhnert, Matthias; Lewan, Elisabet; Moriondo, Marco; Nendel, Claas; Priesack, Eckart; Raynal, Helene; Roggero, Pier P; Rötter, Reimund P; Siebert, Stefan; Specka, Xenia; Tao, Fulu; Teixeira, Edmar; Trombi, Giacomo; Wallach, Daniel; Weihermüller, Lutz; Yeluripati, Jagadeesh; Ewert, Frank

2016-01-01

We show the error in water-limited yields simulated by crop models which is associated with spatially aggregated soil and climate input data. Crop simulations at large scales (regional, national, continental) frequently use input data of low resolution. Therefore, climate and soil data are often generated via averaging and sampling by area majority. This may bias simulated yields at large scales, varying largely across models. Thus, we evaluated the error associated with spatially aggregated soil and climate data for 14 crop models. Yields of winter wheat and silage maize were simulated under water-limited production conditions. We calculated this error from crop yields simulated at spatial resolutions from 1 to 100 km for the state of North Rhine-Westphalia, Germany. Most models showed yields biased by <15% when aggregating only soil data. The relative mean absolute error (rMAE) of most models using aggregated soil data was in the range or larger than the inter-annual or inter-model variability in yields. This error increased further when both climate and soil data were aggregated. Distinct error patterns indicate that the rMAE may be estimated from few soil variables. Illustrating the range of these aggregation effects across models, this study is a first step towards an ex-ante assessment of aggregation errors in large-scale simulations.

Impact of Spatial Soil and Climate Input Data Aggregation on Regional Yield Simulations.

Directory of Open Access Journals (Sweden)

Holger Hoffmann

Full Text Available We show the error in water-limited yields simulated by crop models which is associated with spatially aggregated soil and climate input data. Crop simulations at large scales (regional, national, continental frequently use input data of low resolution. Therefore, climate and soil data are often generated via averaging and sampling by area majority. This may bias simulated yields at large scales, varying largely across models. Thus, we evaluated the error associated with spatially aggregated soil and climate data for 14 crop models. Yields of winter wheat and silage maize were simulated under water-limited production conditions. We calculated this error from crop yields simulated at spatial resolutions from 1 to 100 km for the state of North Rhine-Westphalia, Germany. Most models showed yields biased by <15% when aggregating only soil data. The relative mean absolute error (rMAE of most models using aggregated soil data was in the range or larger than the inter-annual or inter-model variability in yields. This error increased further when both climate and soil data were aggregated. Distinct error patterns indicate that the rMAE may be estimated from few soil variables. Illustrating the range of these aggregation effects across models, this study is a first step towards an ex-ante assessment of aggregation errors in large-scale simulations.

Runoff and Sediment Production under the Similar Rainfall Events in Different Aggregate Sizes of an Agricultural Soil

Directory of Open Access Journals (Sweden)

S. F. Eslami

2016-09-01

soil loss (sediment. Ten same rainfall events with 60 mm h-1 in intensity for 30 min were applied using a designed rainfall simulator in the lab. The rainfall simulator had a rainfall plate with a dimension of 100 cm × 120 cm which has been fixed on a metal frame with 3m height from the ground surface. Runoff and sediment samples were collected using a plastic container placed the out-let of the flumes. Runoff generation of each flume was determined based on multiplying total content volume of the tank by volume proportion of water in the sample. Soil loss for each event was determined using multiply the container volume and sediment concentration of the uniform sample. Initial soil moisture was measured in the aggregate samples before each rainfall event in order to investigate its effect on the runoff and sediment variations in the event scales. Runoff, soil loss and initial soil moisture data were evaluated for normality before any statistical analysis using SPSS version 18 software. Differences of runoff and soil loss among different rainfall events were analyzed using the Duncan's test. Results and Discussion: Based on the results, the soil was calcareous having 16% equivalent calcium carbonate. Low amount of organic matter (0.6%. The measured aggregate stability showed to be very low, indicating high susceptibility of the aggregates to water erosion processes. Significant differences were found among the rainfall events in runoff (p< 0.05, sediment (p< 0.001 and sediment concentration (p< 0.001 which were associated with aggregate breakdown by raindrop impacts in the rainfall events. Runoff and sediment were strongly increased from each event to other event. Significant relationship was found between sediment and runoff in the events (R2= 0.89, p< 0.001. However, sediment showed to have higher increasing trend as compared to runoff variation pattern in the event scale. Sediment value was very low in the first rainfall event due to high portions of the water-stable

Testing the effect of a microbial-based soil amendment on aggregate stability and erodibility

DEFF Research Database (Denmark)

Malozo, Mponda; Iversen, Bo Vangsø; Heckrath, Goswin Johann

to the rainfall-runoff experiment where the microbial-based product had a clear effect on soil erodibility. In relation to measurement of aggregate stability as well as clay dispersion, the picture was less clear. Especially for the sandy Tanzania soil with a low content of organic matter, a clear effect was seen...... aggregate stability and erodibility. Two commercial products, gypsum and a microbial-based solution were used for the experiment and were tested on two Danish sandy loamy soils as well on a sandy soil from Tanzania. The carrier of the microbial-based product, a glycerol solution, was tested as well....... In the laboratory, soils were treated with the soil amendments in a two-step procedure at controlled water contents following aerobic incubation in closed containers. Water-aggregate stability and clay dispersion were measured on soil aggregates less than 8 mm in diameter. Aggregate stability was measured...

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.

Effects of chlorpyrifos on soil carboxylesterase activity at an aggregate-size scale.

Science.gov (United States)

Sanchez-Hernandez, Juan C; Sandoval, Marco

2017-08-01

The impact of pesticides on extracellular enzyme activity has been mostly studied on the bulk soil scale, and our understanding of the impact on an aggregate-size scale remains limited. Because microbial processes, and their extracellular enzyme production, are dependent on the size of soil aggregates, we hypothesized that the effect of pesticides on enzyme activities is aggregate-size specific. We performed three experiments using an Andisol to test the interaction between carboxylesterase (CbE) activity and the organophosphorus (OP) chlorpyrifos. First, we compared esterase activity among aggregates of different size spiked with chlorpyrifos (10mgkg -1 wet soil). Next, we examined the inhibition of CbE activity by chlorpyrifos and its metabolite chlorpyrifos-oxon in vitro to explore the aggregate size-dependent affinity of the pesticides for the active site of the enzyme. Lastly, we assessed the capability of CbEs to alleviate chlorpyrifos toxicity upon soil microorganisms. Our principal findings were: 1) CbE activity was significantly inhibited (30-67% of controls) in the microaggregates (1.0mm) compared with the corresponding controls (i.e., pesticide-free aggregates), 2) chlorpyrifos-oxon was a more potent CbE inhibitor than chlorpyrifos; however, no significant differences in the CbE inhibition were found between micro- and macroaggregates, and 3) dose-response relationships between CbE activity and chlorpyrifos concentrations revealed the capability of the enzyme to bind chlorpyrifos-oxon, which was dependent on the time of exposure. This chemical interaction resulted in a safeguarding mechanism against chlorpyrifos-oxon toxicity on soil microbial activity, as evidenced by the unchanged activity of dehydrogenase and related extracellular enzymes in the pesticide-treated aggregates. Taken together, these results suggest that environmental risk assessments of OP-polluted soils should consider the fractionation of soil in aggregates of different size to measure

Soil aggregate stability and rainfall-induced sediment transport on field plots as affected by amendment with organic matter inputs

Science.gov (United States)

Shi, Pu; Arter, Christian; Liu, Xingyu; Keller, Martin; Schulin, Rainer

2017-04-01

Aggregate stability is an important factor in soil resistance against erosion, and, by influencing the extent of sediment transport associated with surface runoff, it is thus also one of the key factors which determine on- and off-site effects of water erosion. As it strongly depends on soil organic matter, many studies have explored how aggregate stability can be improved by organic matter inputs into the soil. However, the focus of these studies has been on the relationship between aggregate stability and soil organic matter dynamics. How the effects of organic matter inputs on aggregate stability translate into soil erodibility under rainfall impacts has received much less attention. In this study, we performed field plot experiments to examine how organic matter inputs affect aggregate breakdown and surface sediment transport under field conditions in artificial rainfall events. Three pairs of plots were prepared by adding a mixture of grass and wheat straw to one of plots in each pair but not to the other, while all plots were treated in the same way otherwise. The rainfall events were applied some weeks later so that the applied organic residues had sufficient time for decomposition and incorporation into the soil. Surface runoff rate and sediment concentration showed substantial differences between the treatments with and without organic matter inputs. The plots with organic inputs had coarser and more stable aggregates and a rougher surface than the control plots without organic inputs, resulting in a higher infiltration rate and lower transport capacity of the surface runoff. Consequently, sediments exported from the amended plots were less concentrated but more enriched in suspended particles (selective sediment transport. In contrast to the amended plots, there was an increase in the coarse particle fraction (> 250 µm) in the runoff from the plots with no organic matter inputs towards the end of the rainfall events due to emerging bed-load transport

Aggregates morphometry in a Latosol (Oxisol under different soil management systems

Directory of Open Access Journals (Sweden)

Carla Eloize Carducci

2016-02-01

Full Text Available Changes in soil physical properties are inherent in land use, mainly in superficial layers. Structural alterations can directly influence distribution, stability and especially morphometry of soil aggregates, which hence will affect pore system and the dynamic process of water and air in soil. Among the methods used to measure these changes, morphometry is a complementary tool to the classic methods. The aim of this study was to evaluate structural quality of a Latosol (Oxisol, under different management systems, using morphometric techniques. Treatments consisted of soil under no-tillage (NT; pasture (P, in which both had been cultivated for ten years, and an area under native vegetation (NV – Savannah like vegetation. Aggregates were sampled at depths of 0-0.10 and 0.10-0.20 m, retained on sieves with 9.52 – 4.76 mm, 4.76 – 1.0mm, 1.0 – 0.5mm diameter ranges. Aggregate morphometry was assessed by 2D images from scanner via QUANTPORO software. The analyzed variables were: area, perimeter, aspect, roughness, Ferret diameter and compactness. Moreover, disturbed samples were collected at the same depths to determine particle size, aggregate stability in water, water-dispersible clay, clay flocculation index and organic matter content. It was observed that different soil management systems have modified soil aggregate morphology as well as physical attributes; and management effects’ magnitude increased from NT to P.

Impact of Spatial Soil and Climate Input Data Aggregation on Regional Yield Simulations

Science.gov (United States)

Hoffmann, Holger; Zhao, Gang; Asseng, Senthold; Bindi, Marco; Biernath, Christian; Constantin, Julie; Coucheney, Elsa; Dechow, Rene; Doro, Luca; Eckersten, Henrik; Gaiser, Thomas; Grosz, Balázs; Heinlein, Florian; Kassie, Belay T.; Kersebaum, Kurt-Christian; Klein, Christian; Kuhnert, Matthias; Lewan, Elisabet; Moriondo, Marco; Nendel, Claas; Priesack, Eckart; Raynal, Helene; Roggero, Pier P.; Rötter, Reimund P.; Siebert, Stefan; Specka, Xenia; Tao, Fulu; Teixeira, Edmar; Trombi, Giacomo; Wallach, Daniel; Weihermüller, Lutz; Yeluripati, Jagadeesh; Ewert, Frank

2016-01-01

We show the error in water-limited yields simulated by crop models which is associated with spatially aggregated soil and climate input data. Crop simulations at large scales (regional, national, continental) frequently use input data of low resolution. Therefore, climate and soil data are often generated via averaging and sampling by area majority. This may bias simulated yields at large scales, varying largely across models. Thus, we evaluated the error associated with spatially aggregated soil and climate data for 14 crop models. Yields of winter wheat and silage maize were simulated under water-limited production conditions. We calculated this error from crop yields simulated at spatial resolutions from 1 to 100 km for the state of North Rhine-Westphalia, Germany. Most models showed yields biased by data. The relative mean absolute error (rMAE) of most models using aggregated soil data was in the range or larger than the inter-annual or inter-model variability in yields. This error increased further when both climate and soil data were aggregated. Distinct error patterns indicate that the rMAE may be estimated from few soil variables. Illustrating the range of these aggregation effects across models, this study is a first step towards an ex-ante assessment of aggregation errors in large-scale simulations. PMID:27055028

Developing a Soil Aggregate Stability Standard For Use in Laboratory Proficiency Testing

OpenAIRE

Smith, Mackenzie

2018-01-01

Soil health is an important part of agriculture and is becoming an issue to which more and more people are paying attention. In evaluating soil health there are many factors proposed to determine healthy soils, and one of the most reliable indicators, as identified by both academic and soil testing industry experts, is macro-aggregate stability. There is a great need for a method to make standard macro-aggregate stability soil samples for commercial and public labs and other facilities to use...

Colloid Release from Soil Aggregates

DEFF Research Database (Denmark)

Vendelboe, Anders Lindblad; Møldrup, Per; Schjønning, Per

2012-01-01

The content of water-dispersible colloids (WDC) has a major impact on soil functions and structural stability. In addition, the presence of mobile colloids may increase the risk of colloid-facilitated transport of strongly sorbing environmental contaminants. The WDC content was measured in 39 soils......, using laser diffraction, by agitating the samples using a wet-dispersion unit. This approach eliminated the need for long sedimentation times required by the more classical end-over-end shaking approach and provided information about the time-dependent release of WDC. The total clay content of the soils...... ranged from 0.1 to 0.44 kg kg−1. The WDC content was measured on air-dry and moist 1- to 2-mm aggregates. The WDC content at a reference time was highly correlated to the total clay content (r > 0.91, P soils. Only for two sites was the WDC content correlated to the content of clay...

Physico-chemical and mineralogical properties influencing water-stability of aggregates of some Italian surface soils

International Nuclear Information System (INIS)

Mbagwu, J.S.C.; Bazzoffi, P.; Unamba Oparah, I.

1994-06-01

A laboratory study was conducted to determine the relationship between physical, chemical and mineralogical properties of some surface soils (developed in north central Italy) and the stability of their aggregates to water. The index of stability used is the mean-weight diameter of water-stable aggregates (MWD). The ratio of total sand to clay which correlated negatively with MWD (r=-0.638) is the physical property which explained most of the variability in aggregate stability. The chemical properties which correlated best with aggregate stability are FeO (r=0.671), CaO (R=0.635), CaCO 3 (r=0.651) and SiO 2 (r=-0.649). Feldspar, chlorite and calcite are the minerals which influence MWD most, with respective ''r'' values of -0.627, 0.588 and 0.550. The best-fit model developed from soil physical properties explained 59% of the variation in MWD with a standard error of 0.432, that developed from chemical properties explained 97% of the variation in MWD with a standard error of 0.136, whereas the model developed from mineralogical properties explained 78% of the variation in MWD with a standard error of 0.222. Also the closest relationship between measured and model-predicted MWD was obtained with the chemical properties-based model (r=0.985), followed by the mineralogical properties-based model (r=0.884) and then the physical properties-based model (r=0.656). This indicates that the most reliable inference on the stability of these soils in water can be made from a knowledge of the amount and composition of their chemical constituents. (author). 32 refs, 1 fig., 9 tabs

Bioaccessible Porosity in Soil Aggregates and Implications for Biodegradation of High Molecular Weight Petroleum Compounds.

Science.gov (United States)

Akbari, Ali; Ghoshal, Subhasis

2015-12-15

We evaluated the role of soil aggregate pore size on biodegradation of essentially insoluble petroleum hydrocarbons that are biodegraded primarily at the oil-water interface. The size and spatial distribution of pores in aggregates sampled from biodegradation experiments of a clayey, aggregated, hydrocarbon-contaminated soil with relatively high bioremediation end point were characterized by image analyses of X-ray micro-CT scans and N2 adsorption. To determine the bioaccessible pore sizes, we performed separate experiments to assess the ability of hydrocarbon degrading bacteria isolated from the soil to pass through membranes with specific sized pores and to access hexadecane (model insoluble hydrocarbon). Hexadecane biodegradation occurred only when pores were 5 μm or larger, and did not occur when pores were 3 μm and smaller. In clayey aggregates, ∼ 25% of the aggregate volume was attributed to pores larger than 4 μm, which was comparable to that in aggregates from a sandy, hydrocarbon-contaminated soil (~23%) scanned for comparison. The ratio of volumes of inaccessible pores (4 μm) in the clayey aggregates was 0.32, whereas in the sandy aggregates it was approximately 10 times lower. The role of soil microstructure on attainable bioremediation end points could be qualitatively assessed in various soils by the aggregate characterization approach outlined herein.

Increases in soil aggregation following phosphorus additions in a tropical premontane forest are not driven by root and arbuscular mycorrhizal fungal abundances

Science.gov (United States)

Camenzind, Tessa; Papathanasiou, Helena; Foerster, Antje; Dietrich, Karla; Hertel, Dietrich; Homeier, Juergen; Oelmann, Yvonne; Olsson, Pål Axel; Suárez, Juan; Rillig, Matthias

2015-12-01

Tropical ecosystems have an important role in global change scenarios, in part because they serve as a large terrestrial carbon pool. Carbon protection is mediated by soil aggregation processes, whereby biotic and abiotic factors influence the formation and stability of aggregates. Nutrient additions may affect soil structure indirectly by simultaneous shifts in biotic factors, mainly roots and fungal hyphae, but also via impacts on abiotic soil properties. Here, we tested the hypothesis that soil aggregation will be affected by nutrient additions primarily via changes in arbuscular mycorrhizal fungal (AMF) hyphae and root length in a pristine tropical forest system. Therefore, the percentage of water-stable macroaggregates (> 250µm) (WSA) and the soil mean weight diameter (MWD) was analyzed, as well as nutrient contents, pH, root length and AMF abundance. Phosphorus additions significantly increased the amount of WSA, which was consistent across two different sampling times. Despite a positive effect of phosphorus additions on extraradical AMF biomass, no relationship between WSA and extra-radical AMF nor roots was revealed by regression analyses, contrary to the proposed hypothesis. These findings emphasize the importance of analyzing soil structure in understudied tropical systems, since it might be affected by increasing nutrient deposition expected in the future.

Increases in soil aggregation following phosphorus additions in a tropical premontane forest are not driven by root and arbuscular mycorrhizal fungal abundances

Directory of Open Access Journals (Sweden)

Tessa eCamenzind

2016-01-01

Full Text Available Tropical ecosystems have an important role in global change scenarios, in part because they serve as a large terrestrial carbon pool. Carbon protection is mediated by soil aggregation processes, whereby biotic and abiotic factors influence the formation and stability of aggregates. Nutrient additions may affect soil structure indirectly by simultaneous shifts in biotic factors, mainly roots and fungal hyphae, but also via impacts on abiotic soil properties. Here, we tested the hypothesis that soil aggregation will be affected by nutrient additions primarily via changes in arbuscular mycorrhizal fungal (AMF hyphae and root length in a pristine tropical forest system. Therefore, the percentage of water-stable macroaggregates (> 250µm (WSA and the soil mean weight diameter (MWD was analyzed, as well as nutrient contents, pH, root length and AMF abundance. Phosphorus additions significantly increased the amount of WSA, which was consistent across two different sampling times. Despite a positive effect of phosphorus additions on extraradical AMF biomass, no relationship between WSA and extra-radical AMF nor roots was revealed by regression analyses, contrary to the proposed hypothesis. These findings emphasize the importance of analyzing soil structure in understudied tropical systems, since it might be affected by increasing nutrient deposition expected in the future.

Fourier and granulometry methods on 3D images of soil surfaces for evaluating soil aggregate size distribution

DEFF Research Database (Denmark)

Jensen, T.; Green, O.; Munkholm, Lars Juhl

2016-01-01

The goal of this research is to present and compare two methods for evaluating soil aggregate size distribution based on high resolution 3D images of the soil surface. The methods for analyzing the images are discrete Fourier transform and granulometry. The results of these methods correlate...... with a measured weight distribution of the soil aggregates. The results have shown that it is possible to distinguish between the cultivated and the uncultivated soil surface. A sensor system suitable for capturing in-situ high resolution 3D images of the soil surface is also described. This sensor system...

Effect of aggregate structure on VOC gas adsorption onto volcanic ash soil.

Science.gov (United States)

Hamamoto, Shoichiro; Seki, Katsutoshi; Miyazaki, Tsuyoshi

2009-07-15

The understanding of the gaseous adsorption process and the parameters of volatile organic compounds such as organic solvents or fuels onto soils is very important in the analysis of the transport or fate of these chemicals in soils. Batch adsorption experiments with six different treatments were conducted to determine the adsorption of isohexane, a gaseous aliphatic, onto volcanic ash soil (Tachikawa loam). The measured gas adsorption coefficient for samples of Tachikawa loam used in the first three treatments, Control, AD (aggregate destroyed), and AD-OMR (aggregate destroyed and organic matter removed), implied that the aggregate structure of volcanic ash soil as well as organic matter strongly enhanced gas adsorption under the dry condition, whereas under the wet condition, the aggregate structure played an important role in gas adsorption regardless of the insolubility of isohexane. In the gas adsorption experiments for the last three treatments, soils were sieved in different sizes of mesh and were separated into three different aggregate or particle size fractions (2.0-1.0mm, 1.0-0.5mm, and less than 0.5mm). Tachikawa loam with a larger size fraction showed higher gas adsorption coefficient, suggesting the higher contributions of macroaggregates to isohexane gas adsorption under dry and wet conditions.

The soil structure investigation for the interpreting radiocaesium behaviour in upper horizons of Chernobyl contaminated sandy soils

International Nuclear Information System (INIS)

Vazhinskij, A.G.

2002-01-01

The soil-composing particles in natural environment form aggregates of different stability. For soils (topsoil) of contrasting type from Chernobyl NPP area the particle size and microaggregate analyses have been performed and the distribution of Cs 137 in the obtained fractions has been studied. Results of long-term investigation of Cs 137 vertical migration in sandy soils of 50-km zone around Chernobyl NPP have been compared with data on radiocaesium distribution among water-stable aggregates and particles of various size in studied soils. On the basis of particle size analysis and aggregate soil composition the size of soil components with vertical migration potential, and the amount of Cs 137 potentially tending to migrate with the soil components along soil profile have been assessed. Based on findings showing Cs 137 partitioning among water-stable soil aggregates of diverse size and pattern of the radionuclide vertical distribution in top 0-10 cm soil layer, it was assumed that neither shift of peak radiocaesium level from upper soil layer downwards nor the so-called slow constituent of Cs 137 vertical migration (in terms of quasi diffusion description of Cs 137 profile in soil) could not be explained by self-motion of soil aggregates and particles with associated radiocaesium. Hypothesis of root intermixing as principal mechanism responsible for Cs 137 vertical transport in top 0-10 cm soil layer was postulated

[Ecological stoichiometry of soil carbon, nitrogen and phosphorus within soil aggregates in tea plantations with different ages].

Science.gov (United States)

Li, Wei; Zheng, Zi-cheng; Li, Ting-xuan

2015-01-01

This study selected 4 tea plantations with different ages (12-15, 20-22, 30-33 and >50 year-old) located in Ya' an, Sichuan Province, China to investigate the distribution patterns of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) , and to examine the ecological stoichiometric characteristics of C, N and P within soil aggregates. The results showed that the coefficients of variation of SOC, TN and TP were 17.5%, 16.3% and 9.4%, respectively in the 0-20 cm soil layer and were 24.0%, 21.0% and 9.2%, respectively in the 20-40 cm soil layer. The spatial variation of TP was lower than that of SOC and TN but there were significant positive correlations among them. SOC and TN were distributed in the small-size aggregates and both of them had the greatest values in the >50 year-old tea plantation, however, the distribution of TP was relatively uniform among aggregates and ages. The coefficients of variation of C/N, C/P, and N/P were 9.4%, 14.0% and 14.9%, respectively in the 0-20 cm soil layer and were 7.4%, 24.9% and 21.8%, respectively in the 20-40 cm soil layer. Variation of C/N was lower than that of C/P and N/P. Averaged C/P and N/P values in the small-size aggregates were higher than in aggregates of other sizes, and the maximum values were in the >50 year-old plantation. C/N, C/P and N/P had good indication for soil organic carbon storage.

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.

Effect of Carbonates and Bivalent Cations and Their Relationships with Soil Organic Matter from the View Point of Aggregate Formation

Directory of Open Access Journals (Sweden)

Vladimír Šimanský

2014-12-01

Full Text Available The effect of carbonates on soil structure has not been sufficiently studied yet, despite the fact that in the literature their positive impact is mentioned mostly. Carbonates are the source of bivalent cations in soil solution and may be involved in stabilization of the aggregates, because negatively charged organic materials can be adsorbed onto the surface of clay by bivalent or polyvalent cations. We studied the effect of carbonates and bivalent cations and their relationships with soil organic matter (SOM from the point of view of aggregate formation. The studies were carried out in several fields located on loamy Calcaric Chernozem, loamy Haplic and Mollic Fluvisols. The results showed that between exchangeable Mg2+ and water-stable macro-aggregates (WSAma in size fractions >2 mm, positive correlations were found; however, the content of Mg2+ negative correlated with the contents of WSAma in 2 mm; however, between SBC as well as CEC and smaller size fractions of WSAma >1 mm and WSAmi negative correlations were observed. Statistically significant negative correlations were observed between SOM content in WSA and carbonate content, and this effect was stronger in relation to the labile carbon. There were also positive correlations between SOM in WSA and SBC and CEC found if all loamy soils were assessed together.

Radiocesium distribution in aggregate-size fractions of cropland and forest soils affected by the Fukushima nuclear accident.

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Koarashi, Jun; Nishimura, Syusaku; Atarashi-Andoh, Mariko; Matsunaga, Takeshi; Sato, Tsutomu; Nagao, Seiya

2018-08-01

The Fukushima Daiichi nuclear power plant accident caused serious radiocesium ( 137 Cs) contamination in soils in a range of terrestrial ecosystems. It is well documented that the interaction of 137 Cs with soil constituents, particularly clay minerals, in surface soil layers exerts strong control on the behavior of this radionuclide in the environment; however, there is little understanding of how soil aggregation-the binding of soil particles together into aggregates-can affect the mobility and bioavailability of 137 Cs in soils. To explore this, soil samples were collected at seven sites under different land-use conditions in Fukushima and were separated into four aggregate-size fractions: clay-sized (fractions were then analyzed for 137 Cs content and extractability and mineral composition. In forest soils, aggregate formation was significant, and 69%-83% of 137 Cs was associated with macroaggregates and sand-sized aggregates. In contrast, there was less aggregation in agricultural field soils, and approximately 80% of 137 Cs was in the clay- and silt-sized fractions. Across all sites, the 137 Cs extractability was higher in the sand-sized aggregate fractions than in the clay-sized fractions. Mineralogical analysis showed that, in most soils, clay minerals (vermiculite and kaolinite) were present even in the larger-sized aggregate fractions. These results demonstrate that larger-sized aggregates are a significant reservoir of potentially mobile and bioavailable 137 Cs in organic-rich (forest and orchard) soils. Our study suggests that soil aggregation reduces the mobility of particle-associated 137 Cs through erosion and resuspension and also enhances the bioavailability of 137 Cs in soils. Copyright © 2018 Elsevier Ltd. All rights reserved.

Computed Microtomography Quantification of Internal Pore Geometry of Soil Aggregates from Contrasting Land Management Types

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Ananyeva, K.; Wang, W.; Smucker, A. J.; Kravchenko, A. N.; Chun, H. C.; Rivers, M. L.

2010-12-01

Structure of soil aggregate interiors controls intra-aggregate processes and provides important contributions to the biogeochemical processes of the soil profile. Applications of computed microtomography (CMT) to soil science have enabled the direct and nondestructive analyses of internal aggregate pore structures within soil volumes. The main objective of this study was to employ CMT to examine the internal pore structures of soil aggregates, 4 to 6.3 mm across, sampled at 0-20 cm depths from contrasting long-term land management types. Intra-aggregate pore-size distributions were compared among land management types. Porosity below CMT resolution (tillage, grass vegetation) than that of aggregates managed by conventional tillage (CT) used for agriculture. There was also greater percentage of intra-aggregate pores >400 µm in aggregates from NS than CT or NT management systems. In the range 15-100 µm, however, porosity of CT aggregates exceeded that of NS and NT aggregates. Total intra-aggregate porosities were similar and higher for both CT and NS (34.6 and 34.7%, correspondingly) than the 32.6% for NT aggregates. Although statistically significant, this difference (CT or NS vs. NT) was practically small, requiring at least 48 replications to be detected. These results indicate that long-term differences in management affected intra-aggregate pore size distributions. Increased 15-100 µm porosity in CT aggregates is probably related to their greater fragility. A combination of higher microporosity (400 µm in NS aggregates may generate more favorable conditions for microbial activity through a combination of larger intra-aggregate regions with high water-holding capacities and increased aeration and preferential flow pathways for intra-aggregate solute and gas transport. Our current focus is comparing and relating specifics of internal pore structures in the aggregates from contrasting land management types, to the measurements of solution and microbial flow

Variation in soil aggregate-size distribution affects the dissipation of polycyclic aromatic hydrocarbons in long-term field-contaminated soils.

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Wei, Ran; Ni, Jinzhi; Chen, Weifeng; Yang, Yusheng

2017-10-01

Soil organic matter (SOM) is the main adsorbent for polycyclic aromatic hydrocarbons (PAHs) and the principal aggregating agent for soil aggregation that can affect PAH bioavailability and bioaccessibility in soils. The objective of this study was to analyze the relationship between PAH dissipation and variation in soil aggregate-size distribution in two field-contaminated soils with different soil organic C (SOC) content (Anthrosols, 1.41% SOC; Phaeozems, 8.51% SOC) in phytoremediation with alfalfa. The results showed that there were significant reductions of 10.2 and 15.4% of the total PAHs in unplanted and planted treatments, respectively, for Anthrosols. However, there was no significant reduction of total PAHs in either unplanted or planted treatment for Phaeozems. For Anthrosols, mass percentages of coarse sand and fine sand were significantly reduced while coarse silt and fine silt were significantly increased for the planted soil compared to the initial soil (p soil was slightly reduced. The main reason for the dissipation of PAHs in Anthrosols could be that macroaggregates were broken into microaggregates, which made some trapped PAHs become bioaccessible to soil microorganisms.

Bacterial density and community structure associated with aggregate size fractions of soil-feeding termite mounds.

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Fall, S; Nazaret, S; Chotte, J L; Brauman, A

2004-08-01

The building and foraging activities of termites are known to modify soil characteristics such as the heterogeneity. In tropical savannas the impact of the activity of soil-feeding termites ( Cubitermes niokoloensis) has been shown to affect the properties of the soil at the aggregate level by creating new soil microenvironments (aggregate size fractions) [13]. These changes were investigated in greater depth by looking at the microbial density (AODC) and the genetic structure (automated rRNA intergenic spacer analysis: ARISA) of the communities in the different aggregate size fractions (i.e., coarse sand, fine sand, coarse silt, fine silt, and dispersible clays) separated from compartments (internal and external wall) of three Cubitermes niokoloensis mounds. The bacterial density of the mounds was significantly higher (1.5 to 3 times) than that of the surrounding soil. Within the aggregate size fractions, the termite building activity resulted in a significant increase in bacterial density within the coarser fractions (>20 mum). Multivariate analysis of the ARISA profiles revealed that the bacterial genetic structures of unfractionated soil and soil aggregate size fractions of the three mounds was noticeably different from the savanna soil used as a reference. Moreover, the microbial community associated with the different microenvironments in the three termite mounds revealed three distinct clusters formed by the aggregate size fractions of each mound. Except for the 2-20 mum fraction, these results suggest that the mound microbial genetic structure is more dependent upon microbial pool affiliation (the termite mound) than on the soil location (aggregate size fraction). The causes of the specificity of the microbial community structure of termite mound aggregate size fractions are discussed.

TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

OpenAIRE

Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

2015-01-01

In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP....

Aggregate Stability of Tropical Soils Under Long-Term Eucalyptus Cultivation

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Eucalyptus cultivation has increased in all Brazilian regions. Despite the large amount of cultivated area, little is known about how this kind of management system affects soil properties, mainly the aggregate stability. Aggregate stability analyses have proved to be a sensitive tool to measure soi...

Synchrotron-based micro and nanotomographic investigations of soil aggregate microbial and pore structure

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Kemner, K. M.; O'Brien, S.; Whiteside, M. D.; Sholto-Douglas, D.; Antipova, O.; Bailey, V.; Boyanov, M.; Dohnalkova, A.; Gursoy, D.; Kovarik, L.; Lai, B.; Roehrig, C.; Vogt, S.

2017-12-01

Soil is a highly complex network of pore spaces, minerals, and organic matter (e.g., roots, fungi, and bacteria), making it physically heterogeneous over nano- to macro-scales. Such complexity arises from feedbacks between physical processes and biological activity that generate a dynamic, self-organizing 3D complex. Since we first demonstrated the utility of synchrotron-based transmission tomography to image internal soil aggregate structure [Kemner et al., 1998], we and many other researchers have made use of and have advanced the application of this technique. However, our understanding of how microbes and microbial metabolism are distributed throughout soil aggregates is limited, because no technique is available to image the soil pore network and the life that inhabits it. X-ray transmission microtomography can provide highly detailed 3D renderings of soil structure but cannot distinguish cells from other electron-light material such as air or water. However, the use of CdSe quantum dots (QDs) as a reporter of bacterial presence enables us to overcome this constraint, instilling bacterial cells with enough contrast to detect them and their metabolic functions in their opaque soil habitat, with hard x-rays capable of penetrating 3D soil structures at high resolution. Previous transmission tomographic imaging of soil aggregates with high energy synchrotron x-rays has demonstrated 700 nm3 voxel spatial resolution. These and recent results from nanotomographic x-ray transmission imaging of soil aggregates with 30 nm3 voxel resolution will be presented. In addition, results of submicron voxel-sized x-ray fluorescence 3D imaging to determine microbial distributions within soil aggregates and the critical role to be played by the upgrade of the Advanced Photon Source for 100-1000X increases in hard x-ray brilliance will also be presented. *Kemner, et al., SPIE 3449, 45-53, 1998

CHARACTERIZATION OF BIOGENIC, INTERMEDIATE AND PHYSICOGENIC SOIL AGGREGATES OF AREAS IN THE BRAZILIAN ATLANTIC FOREST

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JÚLIO CÉSAR FEITOSA FERNANDES

2017-01-01

Full Text Available Aggregate formation and stability are related to soil quality, contributing significantly to the carbon storage and nutrient maintenance capacities of the soil. Soil aggregates are formed by two different process: physicogenic, related to moistening and drying cycles and input of organic matter; and biogenic, related to the action of macrofauna organisms and roots. The objective this work was to classify aggregates according to their formation process, quantify and compare organic carbon contents in humic substances and assess the stability of aggregates formed by different processes, in areas with different coverage in the Mid Paraiba Valley, Pinheiral, State of Rio de Janeiro, Brazil. Aggregated soil samples were collected at a depth of 0-10 cm, in a Cambisol (Cambissolo Háplico Tb Distrófico under four plant covers: secondary forest in advanced (SFAS, medium (SFMS and initial (SFIS successional stages and managed mixed pasture (MMP. Aggregates were classified and identified into three morphological classes (physicogenic, biogenic and intermediate. The variables evaluated were mean weight diameter (MWD and geometric mean diameter (GMD of aggregates, chemical fractions of organic matter, total organic carbon (TOC and humic substances: humin (C-HUM humic acid (C-FAH and fulvic acid (C-FAF. Biogenic aggregates were found in smaller quantities and showed higher TOC, C-HUM and C-FAH, compared to intermediate and physicogenic aggregates. Thus, biogenic aggregates have potential to be used as soil quality indicators for structured environments, which are able to maintain its intrinsic formation processes.

Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation

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Schomakers, Jasmin; Zehetner, Franz; Mentler, Axel; Ottner, Franz; Mayer, Herwig

2015-10-01

It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested highaccuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm-3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (aggregate stability and release of soil organic matter upon aggregate breakdown.

Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation**

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Schomakers, Jasmin; Zehetner, Franz; Mentler, Axel; Ottner, Franz; Mayer, Herwig

2016-01-01

It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested high-accuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm−3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (aggregate stability and release of soil organic matter upon aggregate breakdown. PMID:27099408

Topsoil and Deep Soil Organic Carbon Concentration and Stability Vary with Aggregate Size and Vegetation Type in Subtropical China

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Fang, Xiang-Min; Chen, Fu-Sheng; Wan, Song-Ze; Yang, Qing-Pei; Shi, Jian-Min

2015-01-01

The impact of reforestation on soil organic carbon (OC), especially in deep layer, is poorly understood and deep soil OC stabilization in relation with aggregation and vegetation type in afforested area is unknown. Here, we collected topsoil (0–15 cm) and deep soil (30–45 cm) from six paired coniferous forests (CF) and broad-leaved forests (BF) reforested in the early 1990s in subtropical China. Soil aggregates were separated by size by dry sieving and OC stability was measured by closed-jar alkali-absorption in 71 incubation days. Soil OC concentration and mean weight diameter were higher in BF than CF. The cumulative carbon mineralization (Cmin, mg CO2-C kg-1 soil) varied with aggregate size in BF and CF topsoils, and in deep soil, it was higher in larger aggregates than in smaller aggregates in BF, but not CF. The percentage of soil OC mineralized (SOCmin, % SOC) was in general higher in larger aggregates than in smaller aggregates. Meanwhile, SOCmin was greater in CF than in BF at topsoil and deep soil aggregates. In comparison to topsoil, deep soil aggregates generally exhibited a lower Cmin, and higher SOCmin. Total nitrogen (N) and the ratio of carbon to phosphorus (C/P) were generally higher in BF than in CF in topsoil and deep soil aggregates, while the same trend of N/P was only found in deep soil aggregates. Moreover, the SOCmin negatively correlated with OC, total N, C/P and N/P. This work suggests that reforested vegetation type might play an important role in soil OC storage through internal nutrient cycling. Soil depth and aggregate size influenced OC stability, and deep soil OC stability could be altered by vegetation reforested about 20 years. PMID:26418563

Recovery of MSWI and soil washing residues as concrete aggregates.

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Sorlini, Sabrina; Abbà, Alessandro; Collivignarelli, Carlo

2011-02-01

The aim of the present work was to study if municipal solid waste incinerator (MSWI) residues and aggregates derived from contaminated soil washing could be used as alternative aggregates for concrete production. Initially, chemical, physical and geometric characteristics (according to UNI EN 12620) of municipal solid waste incineration bottom ashes and some contaminated soils were evaluated; moreover, the pollutants release was evaluated by means of leaching tests. The results showed that the reuse of pre-treated MSWI bottom ash and washed soil is possible, either from technical or environmental point of view, while it is not possible for the raw wastes. Then, the natural aggregate was partially and totally replaced with these recycled aggregates for the production of concrete mixtures that were characterized by conventional mechanical and leaching tests. Good results were obtained using the same dosage of a high resistance cement (42.5R calcareous Portland cement instead of 32.5R); the concrete mixture containing 400 kg/m(3) of washed bottom ash and high resistance cement was classified as structural concrete (C25/30 class). Regarding the pollutants leaching, all concrete mixtures respected the limit values according to the Italian regulation. Copyright © 2010 Elsevier Ltd. All rights reserved.

[Effects of different cultivation patterns on soil aggregates and organic carbon fractions].

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Qiu, Xiao-Lei; Zong, Liang-Gang; Liu, Yi-Fan; Du, Xia-Fei; Luo, Min; Wang, Run-Chi

2015-03-01

Combined with the research in an organic farm in the past 10 years, differences of soil aggregates composition, distribution and organic carbon fractions between organic and conventional cultivation were studied by simultaneous sampling analysis. The results showed that the percentages of aggregates (> 1 mm, 1-0.5 mm, 0.5-0.25 mm and organic cultivation were 9.73%, 18.41%, 24.46% and 43.90%, respectively. The percentage of organic cultivation than that in conventional cultivation. Organic cultivation increased soil organic carbon (average of 17.95 g x kg(-1)) and total nitrogen contents (average of 1.51 g x kg(-1)). Among the same aggregates in organic cultivation, the average content of heavy organic carbon fraction was significantly higher than that in conventional cultivation. This fraction accumulated in organic carbon. In organic cultivation, the content of labile organic carbon in > 1 mm macro-aggregates was significantly higher than that in conventional cultivation, while no significant difference was found among the other aggregates, indicating that the labile organic carbon was enriched in > 1 mm macro-aggregates. Organic cultivation increased the amounts of organic carbon and its fractions, reduced tillage damage to aggregates, and enhanced the stability of organic carbon. Organic cultivation was therefore beneficial for soil carbon sequestration. The findings of this research may provide theoretical basis for further acceleration of the organic agriculture development.

Geotechnical characteristics and stability analysis of rock-soil aggregate slope at the Gushui Hydropower Station, southwest China.

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Zhou, Jia-wen; Shi, Chong; Xu, Fu-gang

2013-01-01

Two important features of the high slopes at Gushui Hydropower Station are layered accumulations (rock-soil aggregate) and multilevel toppling failures of plate rock masses; the Gendakan slope is selected for case study in this paper. Geological processes of the layered accumulation of rock and soil particles are carried out by the movement of water flow; the main reasons for the toppling failure of plate rock masses are the increasing weight of the upper rock-soil aggregate and mountain erosion by river water. Indoor triaxial compression test results show that, the cohesion and friction angle of the rock-soil aggregate decreased with the increasing water content; the cohesion and the friction angle for natural rock-soil aggregate are 57.7 kPa and 31.3° and 26.1 kPa and 29.1° for saturated rock-soil aggregate, respectively. The deformation and failure mechanism of the rock-soil aggregate slope is a progressive process, and local landslides will occur step by step. Three-dimensional limit equilibrium analysis results show that the minimum safety factor of Gendakan slope is 0.953 when the rock-soil aggregate is saturated, and small scale of landslide will happen at the lower slope.

Transformations in soil organic matter and aggregate stability after conversion of Mediterranean forest to agriculture

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Recio Vázquez, Lorena; Almendros, Gonzalo; Carral, Pilar; Knicker, Heike; González Pérez, José Antonio; González Vila, Francisco Javier

2013-04-01

Conversion of forest ecosystems into croplands often leads to severe decrease of the soil organic matter (SOM) levels with the concomitant deterioration of soil structure. The present research focuses on the effects of cultivation on the stability of soil macroaggregates, as well as on the total quantity and quality of SOM. Three representative soils from central Spain (i.e., Petric Calcisol, Cutanic Luvisol and Calcic Vertisol) were sampled. Each site had natural vegetation (NV) dominated either by characteristic Mediterranean forest (dehesa) or cereal crops (CC) under conventional tillage. For each site, three spatial replicates of the NV and CC were sampled. Soil aggregate stability was measured by the wet sieving method. The structural stability index was then calculated as the mass of aggregated soil (>250 μm) remaining after wet sieving, as a percent of total aggregate weight. The analytical characterization of the SOM was carried out after chemical fractionation for quantifying the different organic pools: free organic matter (FOM), humic acids (HA), fulvic acids (FA) and humin (H). Furthermore, whole soil samples pretreated with 10 % HF solution were analyzed by CP-MAS 13C NMR and the purified HA fraction was characterized by elementary analysis, visible and infrared spectroscopies and Py-GC/MS. A marked reduction in the proportion of stable aggregates when the natural ecosystem was converted to agriculture was observed. Values of the structural stability index (%) changed over from 96.2 to 38.1, 95.1 to 83.7 and 98.5 to 60.6 for the Calcisol, Luvisol and Vertisol respectively. Comparatively higher contents of SOM were found in the soils under NV (11.69 to 0.93, 3.29 to 2.72 and 9.51 to 0.79 g C100 g-1soil) even though a quantitative rearrangement of the SOM pools was noticed. In all sites, the relative contribution of the labile C (FOM) to the total SOM content decreased when the forest soils were converted into croplands, whereas the proportion of both

Water stability of soil aggregates in different systems of Chernozem tillage

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Jaroslava Bartlová

2011-01-01

Full Text Available Effects of various agrotechnical measures on macrostructural changes in the ploughing layer and subsoil were studied within the period of 2008–2010. Soil macrostructure was evaluated on the base of water stability of soil aggregates. Altogether three variants of soil tillage were established, viz. ploughing to the depth of 0.22 m (Variant 1, deep soil loosening to the depth of 0.35–0.40 m (Variant 2, and shallow tillage to the depth of 0.15 m (Variant 3. Experiments were established on a field with Modal Chernozem in the locality Hrušovany nad Jevišovkou (maize-growing region, altitude of 210 m, average annual sum of precipitation 461 mm. In the first experimental year, winter rape was the cultivated crop and it was followed by winter wheat, maize and spring wheat in subsequent years. The aim of this study was to evaluate effects of different methods of tillage on water stability of soil aggregates and on yields of individual crops. An overall analysis of results revealed a positive effect of cultivation without ploughing on water stability of soil aggregates. In the variant with ploughing was found out a statistically significant decrease of this stability. At the same time it was also found out that both minimum tillage and deep soil loosening showed a positive effect on yields of crops under study (above all of maize and winter wheat.

Linking soil permeability and soil aggregate stability with root development: a pots experiment (preliminary results)

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Vergani, Chiara; Graf, Frank; Gerber, Werner

2015-04-01

Quantifying and monitoring the contribution of vegetation to the stability of the slopes is a key issue for implementing effective soil bioengineering measures. This topic is being widely investigated both from the hydrological and mechanical point of view. Nevertheless, due to the high variability of the biological components, we are still far from a comprehensive understanding of the role of plants in slope stabilization, especially if the different succession phases and the temporal development of vegetation is considered. Graf et al., 2014, found within the scope of aggregate stability investigations that the root length per soil volume of alder specimen grown for 20 weeks under laboratory conditions is comparable to the one of 20 years old vegetation in the field. This means that already relatively short time scales can provide meaningful information at least for the first stage of colonization of soil bioengineering measures, which is also the most critical. In the present study we analyzed the effect of root growth on two soil properties critical to evaluate the performance of vegetation in restoring and re-stabilizing slopes: permeability and soil aggregate stability. We set up a laboratory experiment in order to work under controlled conditions and limit as much as possible the natural variability. Alnus incana was selected as the study species as it is widely used in restoration projects in the Alps, also because of its capacity to fix nitrogen and its symbiosis with both ecto and arbuscular mycorrhizal fungi. After the first month of growth in germination pots, we planted one specimen each in big quasi cylindrical pots of 34 cm diameter and 35 cm height. The pots were filled with the soil fraction smaller than 10 mm coming from an oven dried moraine collected in a subalpine landslide area (Hexenrübi catchment, central Switzerland). The targeted dry unit weight was 16 kN/m3. The plants have been maintained at a daily temperature of 25°C and relative

[Impact of land use type on stability and organic carbon of soil aggregates in Jinyun Mountain].

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Li, Jian-Lin; Jiang, Chang-Sheng; Hao, Qing-Ju

2014-12-01

Soil aggregates have the important effect on soil fertility, soil quality and the sustainable utilization of soil, and they are the mass bases of water and fertilizer retention ability of soil and the supply or release of soil nutrients. In this paper, in order to study the impact of land use type on stability and organic carbon of soil aggregates in Jinyun Mountain, we separated four land use types of soil, which are woodland, abandoned land, orchard and sloping farmland by wet sieving method, then we got the proportion of large macroaggregates (> 2 mm), small macroaggregates (0.25-2 mm), microaggregates (53 μm-0.25 mm) and silt + clay (soil depth of 0-60 cm and calculated the total content of organic carbon of all aggregates fraction in each soil. The results showed that reclamation of woodland will lead to fragmentation of macroaggregates and deterioration of soil structure, and the proportion of macroaggrgates (> 0.25 mm) were 44.62% and 32.28% respectively in the soils of orchard and sloping farmland, which reduced 38.58% (P soil fraction from silt + clay to large macroaggregates and small macroaggregates, so it will improve the soil structure. MWD (mean weight diameter) and GMD (geometric mean diameter) are important indicators of evaluating the stability of soil aggregates. We found the MWD and GWD in soil depth of 0-60 cm in orchards and sloping farmland were significantly lower than those in woodland (P soil aggregates, and they will be separated more easily by water. However, after changing the sloping farmland to abandoned land will enhance the stability of soil aggregates, and improve the ability of soil to resist external damage. The organic carbon content in each soil aggregate of four land use types decreased with the increase of soil depth. In soil depth of 0-60 cm, the storage of organic carbon of large macroaggregates in each soil are in orders of woodland (14.98 Mg x hm(-2)) > abandoned land (8.71 Mg x hm(-2)) > orchard (5.82 Mg x hm(-2

Aggregate Stability in Soil with Humic and Histic Horizons in a Toposequence under Araucaria Forest

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Daniel Hanke

Full Text Available ABSTRACT Aggregate stability is one of the most important factors in soil conservation and maintenance of soil environmental functions. The objective of this study was to investigate the aggregate stability mechanisms related to chemical composition of organic matter in soil profiles with humic and histic horizons in a toposequence under Araucaria moist forest in southern Brazil. The soils sampled were classified as Humic Hapludox (highest position, Fluvaquentic Humaquepts (lowest slope position, and Typic Haplosaprists (floodplain. The C and N contents were determined in bulk soil samples. The chemical composition of soil organic matter was evaluated by infrared spectroscopy. Aggregate stability was determined by applying increasing levels of ultrasound energy. Carbon content increased from the top of the slope to the alluvial plain. Higher ultrasonic energy values for clay dispersion were observed in the C-rich soils in the lower landscape positions, indicating that organic compounds play an important role in the structural stabilization of these profiles. Both aliphatic and carbohydrate-like structures were pertinent to aggregate stability. In the Oxisol, organo-mineral interaction between carbohydrates and the clay mineral surface was the most important mechanism affecting aggregation. In soils with a higher C content (Humaquepts and Haplosaprists, stabilization is predominantly conferred by the aliphatic groups, which is probably due to the structural protection offered by these hydrophobic organic groups.

Soil aggregation and the stabilization of organic carbon as affected by erosion and deposition

NARCIS (Netherlands)

Wang, X.; Cammeraat, E.L.H.; Cerli, C.; Kalbitz, K.

2014-01-01

The importance of soil aggregation in determining the dynamics of soil organic carbon (SOC) during erosion, transportation and deposition is poorly understood. Particularly, we do not know how aggregation contributes to the often-observed accumulation of SOC at depositional sites. Our objective was

Estimating the collapse of aggregated fine soil structure in a mountainous forested catchment.

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Mouri, Goro; Shinoda, Seirou; Golosov, Valentin; Chalov, Sergey; Shiiba, Michiharu; Hori, Tomoharu; Oki, Taikan

2014-06-01

This paper describes the relationship of forest soil dryness and antecedent rainfall with suspended sediment (SS) yield due to extreme rainfall events and how this relationship affects the survival of forest plants. Several phenomena contribute to this relationship: increasing evaporation (amount of water vapour discharged from soil) due to increasing air temperature, decreasing moisture content in the soil, the collapse of aggregates of fine soil particles, and the resulting effects on forest plants. To clarify the relationships among climate variation, the collapse of soil particle aggregates, and rainfall-runoff processes, a numerical model was developed to reproduce such aggregate collapse in detail. The validity of the numerical model was confirmed by its application to the granitic mountainous catchment of the Nagara River basin in Japan and by comparison with observational data. The simulation suggests that important problems, such as the collapse of forest plants in response to decreases in soil moisture content and antecedent rainfall, will arise if air temperature continues to increase. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

Soil aggregate formation: the role of wetting-drying cycles in the genesis of interparticle bonding

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Albalasmeh, Ammar; Ghezzehei, Teamrat

2013-04-01

Soil structure influences many soil properties including aeration, water retention, drainage, bulk density, and resistance to erosion and indirectly influences most biological and chemical processes that occur in and around soil. In nature, soil is continually exposed to wetting (e.g., rainfall and diffusive flow) and drying (e.g., evaporation, diffusive flow and plant uptake). These natural wetting and drying cycles of soils are physical events that profoundly affect the development of soil structure, aggregate stability, carbon (C) flux and mineralization. We hypothesize that drying of capillary water transports suspended and/or dissolved cementing agents toward inter-particle contacts and eventually deposits part of the colloidal mass forming inter-particle bonds. Here, we will show the role of wetting and drying cycles on soil aggregation and stabilization and how these cycles transport and deposit organic cementing agents at the inter-particle contact. We found that aggregates of sand and silt particles can be formed by subjecting loose particles to wetting-drying cycles in the presence of dilute solutions of organic matter that mimic root or microbial exudates. Moreover, majority of the organic matter was deposited in the contact region between the sand particles, where the water accumulates during drying. The model predictions and aggregate stability measurements are supported by scanning electron micrographs that clearly show the process of aggregate formation.

Adsorption and desorption of Cu2+ on paddy soil aggregates pretreated with different levels of phosphate.

Science.gov (United States)

Dai, Jun; Wang, Wenqin; Wu, Wenchen; Gao, Jianbo; Dong, Changxun

2017-05-01

Interactions between anions and cations are important for understanding the behaviors of chemical pollutants and their potential risks in the environment. Here we prepared soil aggregates of a yellow paddy soil from the Taihu Lake region, and investigated the effects of phosphate (P) pretreatment on adsorption-desorption of Cu 2+ of soil aggregates, free iron oxyhydrates-removed soil aggregates, goethite, and kaolinite with batch adsorption method. The results showed that Cu 2+ adsorption was reduced on the aggregates pretreated with low concentrations of P, and promoted with high concentrations of P, showing a V-shaped change. Compared with the untreated aggregates, the adsorption capacity of Cu 2+ was reduced when P application rates were lower than 260, 220, 130 and 110mg/kg for coarse, clay, silt and fine sand fractions, respectively. On the contrary, the adsorption capacity of Cu 2+ was higher on P-pretreated soil aggregates than on the control ones when P application rates were greater than those values. However, the desorption of Cu 2+ was enhanced at low levels of P, but suppressed at high levels of P, displaying an inverted V-shaped change over P adsorption. The Cu 2+ adsorption by the aggregate particles with and without P pretreatments was well described by the Freundlich equation. Similar results were obtained on P-pretreated goethite. However, such P effects on Cu 2+ adsorption-desorption were not observed on kaolinite and free iron oxyhydrates-removed soil aggregates. The present results indicate that goethite is one of the main soil substances responsible for the P-induced promotion and inhibition of Cu 2+ adsorption. Copyright © 2016. Published by Elsevier B.V.

Microflora and structural stability of soils

International Nuclear Information System (INIS)

Guckert, A.; Chone, Therese; Jacquin, F.; Institut National Polytechnique, 54 - Nancy; Centre National de la Recherche Scientifique, 54 - Vandoeuvre-les-Nancy

1975-01-01

Water stable aggregates produced during the incubation of a loamy soil amended with glucose 14 C show a quite differing evolution of their physical properties and their organic matter according to the time of incubation after which they have been isolated from the soil by water sieving. The aggregates, built up during the first week of incubation, therefore during the maximal activity stage of the microflora of the soil, present the highest stability against biodegradation induced by a second incubation process, even if this one has reached six weeks. This evolution of the physical properties of the aggregates, is essentially in relationship with the microbially synthetized organic matter and especially the polysaccharides preferentially incorporated into the humine fraction. This relatively labile microbial humine has a high aggregating effect, the polysaccharide chains forming several bonds between the neighbouring clay surfaces and building up stable structural units. The mechanical strength of these aggregates is related to the stabilization of the humine produced previously and whose evolution towards a relatively stable form seems to be the result of two mechanisms: a secundary biodegradation parallel to a higher humification process of the organic matter and a increase of the bonds between polysaccharides and clay surfaces favoured by the alternation of wetting and drying [fr

Conceptual Modeling of the Influence of Wetting and Drying Cycles on Soil Aggregation and Stabilization

Science.gov (United States)

Albalasmeh, A. A.; Ghezzehei, T.

2011-12-01

Soil structure directly determines important soil physical properties including porosity, hydraulic conductivity, water retention, and mechanical strength and indirectly influences most biological and chemical processes that occur in and around soil. The interaction of environmental and biotic agents influences the physical condition of the soil, particularly through soil structural evolution. Wetting and drying cycles are important environmental processes known to enhance aggregation, while clay minerals, sesquioxides and soil organic matter (SOM) are the soil solids most involved in soil structural development. We hypothesize that drying of capillary water transports suspended and/or dissolved cementing agents toward inter-particle contacts and eventually deposits part of the colloidal mass forming inter-particle bonds. Here, we will show the role of wetting and drying cycles on soil aggregation and stabilization and how these cycles transport and deposit organic cementing agents at the inter-particle contact. We will present results of the effect of particle size, number of wetting and drying cycles, viscosity, molecule length and concentration of suspended and/or dissolved cementing agents on soil aggregation and stabilization.

Dynamics of soil biogeochemical gas emissions shaped by remolded aggregate sizes and carbon configurations under hydration cycles.

Science.gov (United States)

Ebrahimi, Ali; Or, Dani

2018-01-01

Changes in soil hydration status affect microbial community dynamics and shape key biogeochemical processes. Evidence suggests that local anoxic conditions may persist and support anaerobic microbial activity in soil aggregates (or in similar hot spots) long after the bulk soil becomes aerated. To facilitate systematic studies of interactions among environmental factors with biogeochemical emissions of CO 2 , N 2 O and CH 4 from soil aggregates, we remolded silt soil aggregates to different sizes and incorporated carbon at different configurations (core, mixed, no addition). Assemblies of remolded soil aggregates of three sizes (18, 12, and 6 mm) and equal volumetric proportions were embedded in sand columns at four distinct layers. The water table level in each column varied periodically while obtaining measurements of soil GHG emissions for the different aggregate carbon configurations. Experimental results illustrate that methane production required prolonged inundation and highly anoxic conditions for inducing measurable fluxes. The onset of unsaturated conditions (lowering water table) resulted in a decrease in CH 4 emissions while temporarily increasing N 2 O fluxes. Interestingly, N 2 O fluxes were about 80% higher form aggregates with carbon placement in center (anoxic) core compared to mixed carbon within aggregates. The fluxes of CO 2 were comparable for both scenarios of carbon sources. These experimental results highlight the importance of hydration dynamics in activating different GHG production and affecting various transport mechanisms about 80% of total methane emissions during lowering water table level are attributed to physical storage (rather than production), whereas CO 2 emissions (~80%) are attributed to biological activity. A biophysical model for microbial activity within soil aggregates and profiles provides a means for results interpretation and prediction of trends within natural soils under a wide range of conditions. © 2017 John

Changes of Soil Aggregate Stability as a Result of the Effect of Freeze-thaw Cycles

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Aneta Žabenská

2015-01-01

Full Text Available The objective of the present research was to assess the changes in soil erodibility during the non-vegetation period as one of the factors affecting the snowmelt erosion. The temperature fluctuation was simulated with the use of a climatic chamber ex situ. The soil surface was for simplicity reasons considered without any plant or snow cover. The paper deals with the rate of soil erodibility determination – the soil erodibility should increase due to the decrease of soil aggregate stability depending on the number of freeze-thaw cycles and initial soil moisture. Soil samples (taken from three sites were subjected to freeze-thaw cycles under laboratory conditions. Changes in soil agreggate stability were monitored as one of the main soil characteristics which determine the soil erodibility. Two methods were used to determine the soil macroaggregate stability (soil aggregate fraction 1–2 mm: standard single-sieve method of wet sieving (Kemper and Rosenau, 1986, and dry aggregate analysis using a set of flat sieves with a diameter of 1 mm and 0.5 mm. The results of each method are controversial. Intended hypothesis has not been clearly confirmed.

Artificial climate warming positively affects arbuscular mycorrhizae but decreases soil aggregate water stability in an annual grassland

Energy Technology Data Exchange (ETDEWEB)

Rillig, M.C.; Wright, S.F.; Shaw, M.R.; Field, C.B.

2002-04-01

Despite the importance of arbuscular mycorrhizae to the functioning of terrestrial ecosystems (e.g. nutrient uptake, soil aggregation), and the increasing evidence of global warming, responses of arbuscular mycorrhizal fungi (AMF) to climate warming are poorly understood. In a field experiment using infrared heaters, we found effects of warming on AMF after one growing season in an annual grassland, in the absence of any effects on measured root parameters (weight, length, average diameter). AMF soil hyphal length was increased by over 40% in the warmed plots, accompanied by a strong trend for AMF root colonization increase. In the following year, root weight was again not significantly changed, and AMF root colonization increased significantly in the warmed plots. Concentration of the soil protein glomalin, a glycoprotein produced by AMF hyphae with importance in soil aggregation, was decreased in the warmed plots. Soil aggregate water stability, measured for five diameter size classes, was also decreased significantly. In the following year, soil aggregate weight in two size classes was decreased significantly, but the effect size was very small. These results indicate that ecosystem warming may have stimulated carbon allocation to AMF. Other factors either influenced glomalin decomposition or production, hence influencing the role of these symbionts in soil aggregation. The observed small changes in soil aggregation, if widespread among terrestrial ecosystems, could have important consequences for soil carbon storage and erosion in a warmed climate, especially if there are cumulative effects of warming. (au)

Behaviour of radioactive and stable isotopes of calcium in the soil-solution-plant system at different soil humidity

International Nuclear Information System (INIS)

Karavaeva, E.N.; Molchanova, I.V.

1976-01-01

The results of experiments performed to study the behaviour of radioactive and stable isotopes of Ca in soil - solution - plant system at different soil moistening are given. The experiments have been conducted in culture pans with two soils: soddy-meadow and soddy-podzolic differing in a number of physico-chemical properties. The solution of radioactive Ca( 45 CaCl 2 ) has been applied to soddy-meadow soil at the rate of 0.2 μcurie/kg, and to soddy-podzolic soil - at the rate of 0.1 μcurie/kg. The distribution and accumulation coefficients are estimated by the ratio to the total content of stable Ca and 45 Ca in soil. A direct relationship between distribution coefficients and the rate of soil moistening is observed. It has been established that 45 Ca and the natural stable isotopes of Ca applied to the soil differ in the type of distribution in soil - soil solution system and in accumulation by plants. However, a great similarity has been observed in behaviour of radioactive and stable isotopes of Ca depending on soil moistening

Temporal variations in organic carbon, soil reactivity and aggregate ...

African Journals Online (AJOL)

Administrator

2007-02-19

Feb 19, 2007 ... and aggregate stability in soils of contrasting cropping ... Samples for physical and chemical analysis were collected in triplicate after two and four weeks of .... passed through 2 mm sieve and composted under shade for about.

Chernozem aggregate waterstability loss investigation in a long-term bare fallow experiment

Science.gov (United States)

Vasilyeva, N. A.; Milanovskiy, E. Y.

2009-04-01

The research is focused on mechanisms of aggregate waterstability controlled by soil organic matter (SOM). The objects of the research are two contrast variants of typical chernozem - under native grassland and under a 60-year bare fallow experimental plot (100 m2) on the territory of Central Chernozem Biosphere Reserve, Russia. Seasonal plowing and deficiency of fresh plant residues (due to weeding out) resulted in a rapid mineralization of SOM. The Corg content in the 0-20 cm topsoil under native grassland is 6-4.5 %. For the last two decades Corg content under bare fallow has stabilized on the 2.6% level and is therefore assumed to represent stable SOM pool. However excellent aggregate waterstability of chernozem is completely lost under bare fallow. Therefore the aim of our study is to reveal the role of different SOM pools spatial and functional organization in aggregate waterstability formation. Bulk soil samples were collected from 2 m grassland profile and 1.5 m bare fallow profile with 10 cm interval and simultaneous measurements of soil field density and moisture. Following samples were analysed: bulk samples, dry and wet-sieving aggregates, undisturbed and pulverized aggregates, granule-densimetric fractions obtained by sedimentation of bulk samples (clay 5 mkm) with following densimetric fractionation in bromoform (light ? 2.4 g/cm3), and above mentioned samples after removal of SOM by hydrogen peroxide. Isolation of aggregates and granule-densimetric fractionation were carried out for bulk soils at 0-20, 40-50 and 80-90 cm depth. We use elemental analysis (C, H, N), size exclusion and hydrophobic interaction chromatography of humic substances (HS), laser diffraction particle size analysis, specific surface area (SSA) measurements by nitrogen adsorption and micromorphological examination of thin sections. Detailed characteristics obtained for aggregates and granule-densimetric fractions from a typical chernozem soil under native grassland and under 60

[Characteristics of soil organic carbon and enzyme activities in soil aggregates under different vegetation zones on the Loess Plateau].

Science.gov (United States)

Li, Xin; Ma, Rui-ping; An, Shao-shan; Zeng, Quan-chao; Li, Ya-yun

2015-08-01

In order to explore the distribution characteristics of organic carbon of different forms and the active enzymes in soil aggregates with different particle sizes, soil samples were chosen from forest zone, forest-grass zone and grass zone in the Yanhe watershed of Loess Plateau to study the content of organic carbon, easily oxidized carbon, and humus carbon, and the activities of cellulase, β-D-glucosidase, sucrose, urease and peroxidase, as well as the relations between the soil aggregates carbon and its components with the active soil enzymes were also analyzed. It was showed that the content of organic carbon and its components were in order of forest zone > grass zone > forest-grass zone, and the contents of three forms of organic carbon were the highest in the diameter group of 0.25-2 mm. The content of organic carbon and its components, as well as the activities of soil enzymes were higher in the soil layer of 0-10 cm than those in the 10-20 cm soil layer of different vegetation zones. The activities of cellulase, β-D-glucosidase, sucrose and urease were in order of forest zone > grass zone > forest-grass zone. The peroxidase activity was in order of forest zone > forest-grass zone > grass zone. The activities of various soil enzymes increased with the decreasing soil particle diameter in the three vegetation zones. The activities of cellulose, peroxidase, sucrose and urease had significant positive correlations with the contents of various forms of organic carbon in the soil aggregates.

C and N accumulations in soil aggregates determine nitrous oxide emissions from cover crop treated rice paddy soils during fallow season

International Nuclear Information System (INIS)

Pramanik, Prabhat; Haque, Md. Mozammel; Kim, Sang Yoon; Kim, Pil Joo

2014-01-01

Combination of leguminous and non-leguminous plant residues are preferably applied in rice paddy soils to increase the rate of organic matter mineralization and to improve plant growth. However, organic matter addition facilitates methane (CH 4 ) emission from rice paddy soil. Mineralization of organic nitrogen (N) increases NO 3 –N concentrations in soil, which are precursors for the formation of nitrous oxide (N 2 O). However, N 2 O is a minor greenhouse gas emitted from submerged rice field and hence is not often considered during calculation of total global warming potential (GWP) during rice cultivation. The hypothesis of this study was that fluxes of N 2 O emissions might be changed after removal of flooded water from rice field and the effect of cover crops on N 2 O emissions in the fallow season might be interesting. However, the effects of N-rich plant residues on N 2 O emission rates in the fallow season and its effect on annual GWP were not studied before. In this experiment, combination of barley (non-leguminous) and hairy vetch (leguminous) biomasses were applied at 9 Mg ha −1 and 27 Mg ha −1 rates in rice paddy soil. Cover crop application significantly increased CH 4 emission flux while decreased N 2 O emissions during rice cultivation. The lowest N 2 O emission was observed in 27 Mg ha −1 cover crop treated plots. Cover crop applications increased N contents in soil aggregates especially in smaller aggregates (< 250 μm), and that proportionately increased the N 2 O emission potentials of these soil aggregates. Fluxes of N 2 O emissions in the fallow season were influenced by the N 2 O emission potentials of soil aggregates and followed opposite trends as those observed during rice cultivation. Therefore, it could be concluded that the doses of cover crop applications for rice cultivation should not be optimized considering only CH 4 , but N 2 O should also be considered especially for fallow season to calculate total GWP. - Highlights: �

Relationship between soil aggregate strength, shape and porosity for soils under different long-term management

DEFF Research Database (Denmark)

Munkholm, Lars Juhl; Heck, Richard J; Deen, Bill

2016-01-01

were mouldboard ploughing (MP) and no-tillage (NT). The soil coreswere exposed to a drop shatter test and airdried before separation into different size fractions. Ten aggregates fromthe 4–9.2mmsize fraction per core sample (i.e. 320 in all)were X-ray micro-CT scanned. The size, shape and porosity...... porosity and more rounded aggregates than the continuous corn rotation. Surprisingly, therewas no treatment effect on X-ray micro-CT resolvable porosities. Aggregate strength decreased with both total and X-ray micro-CT resolvable porosity even though the correlations were weak. Significant correlation...

The Effect of Aggregate-Size Fractions on the Availability of Cu in Some Contaminated Soils with Heavy Metals

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Akram Farshadirad

2017-06-01

Full Text Available Introduction: In recent years, because of the presence of industrial factories around the Isfahan province of Iran and high concentrations of heavy metals in the vicinity of them, and the gradual accumulation of heavy metals from various sources of pollution in urban areas over time, including gasoline combustion, and use of urban waste compost and sewage sludge as fertilizer, there has been widespread concerned regarding the human health problems with increasing heavy metals in soils around the Isfahan city. The variation of composition in the soil matrix may lead to variation of composition and behavior of soil heavy metals. Soil is a heterogeneous body of materials and soil components are obviously in interaction. Studies tacking this complexity often use aggregate measurements as surrogates of the complex soil matrix. So, it is important the understanding soil particle-size distribution of aggregates and its effects on heavy metal partitioning among the size fractions, the fate of metals and their toxicity potential in the soil environment. Therefore, the present study aimed to determine the Cu release potential from different size fractions of different polluted soils by different extractants and their availability for corn plant. Materials and Methods: Five soil samples were collected from the surface soils (0–15 cm of Isfahan province, in central of Iran. The soil samples were air-dried and ground to pass a 2-mm sieve for laboratory analysis. Air dried samples fractionated into four different aggregate size fractions 2.0–4.0 (large macro-aggregate, 0.25–2 (small macro-aggregate, 0.05–0.25 (micro-aggregate, and

Non-invasive localization of organic matter in soil aggregates using SR-μCT

Science.gov (United States)

Peth, Stephan; Mordhorst, Anneka; Chenu, Claire; Uteau Puschmann, Daniel; Garnier, Patricia; Nunan, Naoise; Pot, Valerie; Beckmann, Felix; Ogurreck, Malte

2014-05-01

Knowledge of the location of soil organic matter (SOM) and its spatial association to soil structure is an important step in improving modeling approaches for simulating organic matter turnover processes. Advanced models for carbon mineralization are able to account for the 3D distribution of SOM which is assumed to influence mineralisation. However, their application is still limited by the fact that no method exists to non-invasively determine the 3D spatial distribution of SOM in structured soils. SR-based X-ray microtomography (SR-µCT) is an advanced and promising tool in gaining knowledge on the 3-dimensional organization of soil phases (minerals, organic matter, water, air) which on a voxel level could be implemented into spatially explicit models. However, since the contrast of linear attenuation coefficients of soil organic matter on the one hand and mineral components and water on the other hand are relatively low, especially when materials are finely dispersed, organic matter within the soil pore space is often not resolved in ordinary X-ray absorption contrast imaging. To circumvent this problem we have developed a staining procedure for organic matter using Osmium-tetroxide since Osmium is an element with an absorption edge at a higher X-ray energy level. Osmium is known from transmission electron microscopy analysis (TEM) to stain organic matter specifically and irreversibly while having an absorption edge at approximately 74 keV. We report on the application of a novel Osmium vapor staining method to analyze differences in organic matter content and identify small scale spatial distribution of SOM in soil aggregates. To achieve this we have taken soil aggregate samples (6-8 mm across) obtained from arable soils differing in soil management. Aggregate samples were investigated by synchrotron-based X-ray microtomography (SR-µCT) after staining the sample with Osmium-tetroxide (OsO4) vapor. We utilized the monochromatic X-ray beam to locate osmium

Potential Carbon Transport: Linking Soil Aggregate Stability and Sediment Enrichment for Updating the Soil Active Layer within Intensely Managed Landscapes

Science.gov (United States)

Wacha, K.; Papanicolaou, T.; Abban, B. K.; Wilson, C. G.

2014-12-01

Currently, many biogeochemical models lack the mechanistic capacity to accurately simulate soil organic carbon (SOC) dynamics, especially within intensely managed landscapes (IMLs) such as those found in the U.S. Midwest. These modeling limitations originate by not accounting for downslope connectivity of flowpathways initiated and governed by landscape processes and hydrologic forcing, which induce dynamic updates to the soil active layer (generally top 20-30cm of soil) with various sediment size fractions and aggregates being transported and deposited along the downslope. These hydro-geomorphic processes, often amplified in IMLs by tillage events and seasonal canopy, can greatly impact biogeochemical cycles (e.g., enhanced mineralization during aggregate breakdown) and in turn, have huge implications/uncertainty when determining SOC budgets. In this study, some of these limitations were addressed through a new concept, Potential Carbon Transport (PCT), a term which quantifies a maximum amount of material available for transport at various positions of the landscape, which was used to further refine a coupled modeling framework focused on SOC redistribution through downslope/lateral connectivity. Specifically, the size fractions slaked from large and small aggregates during raindrop-induced aggregate stability tests were used in conjunction with rainfall-simulated sediment enrichment ratio (ER) experiments to quantify the PCT under various management practices, soil types and landscape positions. Field samples used in determining aggregate stability and the ER experiments were collected/performed within the historic Clear Creek Watershed, home of the IML Critical Zone Observatory, located in Southeastern Iowa.

Carbohydrates and thermal properties indicate a decrease in stable aggregate carbon following forest colonization of mountain grassland

DEFF Research Database (Denmark)

Guidi, Claudia; Cannella, David; Leifeld, Jens

2015-01-01

and thermally labile C showed similar patterns in bulk soil, suggesting that thermal analysis can be used to complement chemical analysis although a straightforward relationship could not be established. Following forest expansion on abandoned grassland, ratios of microbially to plant-derived carbohydrates......In mountainous areas of Europe, the abandonment of grasslands followed by forest expansion is the dominant land-use change. Labile (i.e. easily decomposable) litter represents the major source for soil microbial products, which promote soil aggregation and long-term C stabilization. Our objective...... was to investigate changes in the content and origin of soil C components involved into aggregate stabilization (i.e. carbohydrates) following forest expansion on abandoned grassland in the Alps, where only few studies have been conducted. Changes in carbohydrates and thermally labile C were assessed along a land...

C and N accumulations in soil aggregates determine nitrous oxide emissions from cover crop treated rice paddy soils during fallow season

Energy Technology Data Exchange (ETDEWEB)

Pramanik, Prabhat, E-mail: prabhat2003@gmail.com; Haque, Md. Mozammel; Kim, Sang Yoon; Kim, Pil Joo, E-mail: pjkim@gnu.ac.kr

2014-08-15

Combination of leguminous and non-leguminous plant residues are preferably applied in rice paddy soils to increase the rate of organic matter mineralization and to improve plant growth. However, organic matter addition facilitates methane (CH{sub 4}) emission from rice paddy soil. Mineralization of organic nitrogen (N) increases NO{sub 3}–N concentrations in soil, which are precursors for the formation of nitrous oxide (N{sub 2}O). However, N{sub 2}O is a minor greenhouse gas emitted from submerged rice field and hence is not often considered during calculation of total global warming potential (GWP) during rice cultivation. The hypothesis of this study was that fluxes of N{sub 2}O emissions might be changed after removal of flooded water from rice field and the effect of cover crops on N{sub 2}O emissions in the fallow season might be interesting. However, the effects of N-rich plant residues on N{sub 2}O emission rates in the fallow season and its effect on annual GWP were not studied before. In this experiment, combination of barley (non-leguminous) and hairy vetch (leguminous) biomasses were applied at 9 Mg ha{sup −1} and 27 Mg ha{sup −1} rates in rice paddy soil. Cover crop application significantly increased CH{sub 4} emission flux while decreased N{sub 2}O emissions during rice cultivation. The lowest N{sub 2}O emission was observed in 27 Mg ha{sup −1} cover crop treated plots. Cover crop applications increased N contents in soil aggregates especially in smaller aggregates (< 250 μm), and that proportionately increased the N{sub 2}O emission potentials of these soil aggregates. Fluxes of N{sub 2}O emissions in the fallow season were influenced by the N{sub 2}O emission potentials of soil aggregates and followed opposite trends as those observed during rice cultivation. Therefore, it could be concluded that the doses of cover crop applications for rice cultivation should not be optimized considering only CH{sub 4}, but N{sub 2}O should also be

Differences in SOM decomposition and temperature sensitivity among soil aggregate size classes in a temperate grasslands.

Directory of Open Access Journals (Sweden)

Qing Wang

Full Text Available The principle of enzyme kinetics suggests that the temperature sensitivity (Q10 of soil organic matter (SOM decomposition is inversely related to organic carbon (C quality, i.e., the C quality-temperature (CQT hypothesis. We tested this hypothesis by performing laboratory incubation experiments with bulk soil, macroaggregates (MA, 250-2000 μm, microaggregates (MI, 53-250 μm, and mineral fractions (MF, MF>bulk soil >MI(P <0.05. The Q10 values were highest for MA, followed (in decreasing order by bulk soil, MF, and MI. Similarly, the activation energies (Ea for MA, bulk soil, MF, and MI were 48.47, 33.26, 27.01, and 23.18 KJ mol-1, respectively. The observed significant negative correlations between Q10 and C quality index in bulk soil and soil aggregates (P<0.05 suggested that the CQT hypothesis is applicable to soil aggregates. Cumulative C emission differed significantly among aggregate size classes (P <0.0001, with the largest values occurring in MA (1101 μg g-1, followed by MF (976 μg g-1 and MI (879 μg g-1. These findings suggest that feedback from SOM decomposition in response to changing temperature is closely associated withsoil aggregation and highlights the complex responses of ecosystem C budgets to future warming scenarios.

Nitrogen-mediated effects of elevated CO2 on intra-aggregate soil pore structure.

Science.gov (United States)

Caplan, Joshua S; Giménez, Daniel; Subroy, Vandana; Heck, Richard J; Prior, Stephen A; Runion, G Brett; Torbert, H Allen

2017-04-01

Soil pore structure has a strong influence on water retention, and is itself influenced by plant and microbial dynamics such as root proliferation and microbial exudation. Although increased nitrogen (N) availability and elevated atmospheric CO 2 concentrations (eCO 2 ) often have interacting effects on root and microbial dynamics, it is unclear whether these biotic effects can translate into altered soil pore structure and water retention. This study was based on a long-term experiment (7 yr at the time of sampling) in which a C 4 pasture grass (Paspalum notatum) was grown on a sandy loam soil while provided factorial additions of N and CO 2 . Through an analysis of soil aggregate fractal properties supported by 3D microtomographic imagery, we found that N fertilization induced an increase in intra-aggregate porosity and a simultaneous shift toward greater accumulation of pore space in larger aggregates. These effects were enhanced by eCO 2 and yielded an increase in water retention at pressure potentials near the wilting point of plants. However, eCO 2 alone induced changes in the opposite direction, with larger aggregates containing less pore space than under control conditions, and water retention decreasing accordingly. Results on biotic factors further suggested that organic matter gains or losses induced the observed structural changes. Based on our results, we postulate that the pore structure of many mineral soils could undergo N-dependent changes as atmospheric CO 2 concentrations rise, having global-scale implications for water balance, carbon storage, and related rhizosphere functions. © 2016 John Wiley & Sons Ltd.

Highly Stable Trypsin-Aggregate Coatings on Polymer Nanofibers for Repeated Protein Digestion

Energy Technology Data Exchange (ETDEWEB)

Kim, Byoung Chan; Lopez-Ferrer, Daniel; Lee, Sang-mok; Ahn, Hye-kyung; Nair, Sujith; Kim, Seong H.; Kim, Beom S.; Petritis, Konstantinos; Camp, David G.; Grate, Jay W.; Smith, Richard D.; Koo, Yoon-mo; Gu, Man Bock; Kim, Jungbae

2009-04-01

A stable and robust trypsin-based biocatalytic system was developed and demonstrated for proteomic applications. The system utilizes polymer nanofibers coated with trypsin aggregates for immobilized protease digestions. After covalently attaching an initial layer of trypsin to the polymer nanofibers, highly concentrated trypsin molecules are crosslinked to the layered trypsin by way of a glutaraldehyde treatment. This new process produced a 300-fold increase in trypsin activity compared with a conventional method for covalent trypsin immobilization and proved to be robust in that it still maintained a high level of activity after a year of repeated recycling. This highly stable form of immobilized trypsin was also resistant to autolysis, enabling repeated digestions of bovine serum albumin over 40 days and successful peptide identification by LC-MS/MS. Finally, the immobilized trypsin was resistant to proteolysis when exposed to other enzymes (i.e. chymotrypsin), which makes it suitable for use in “real-world” proteomic applications. Overall, the biocatalytic nanofibers with enzyme aggregate coatings proved to be an effective approach for repeated and automated protein digestion in proteomic analyses.

Long-term rice cultivation stabilizes soil organic carbon and promotes soil microbial activity in a salt marsh derived soil chronosequence

Science.gov (United States)

Wang, Ping; Liu, Yalong; Li, Lianqing; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Joseph, Stephen; Pan, Genxing

2015-01-01

Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist. PMID:26503629

Continuous soil maps - a fuzzy set approach to bridge the gap between aggregation levels of process and distribution models

NARCIS (Netherlands)

Gruijter, de J.J.; Walvoort, D.J.J.; Gaans, van P.F.M.

1997-01-01

Soil maps as multi-purpose models of spatial soil distribution have a much higher level of aggregation (map units) than the models of soil processes and land-use effects that need input from soil maps. This mismatch between aggregation levels is particularly detrimental in the context of precision

Bacterial exopolysaccharide and biofilm formation stimulate chickpea growth and soil aggregation under salt stress

Directory of Open Access Journals (Sweden)

Aisha Waheed Qurashi

2012-09-01

Full Text Available To compensate for stress imposed by salinity, biofilm formation and exopolysaccharide production are significant strategies of salt tolerant bacteria to assist metabolism. We hypothesized that two previously isolated salt-tolerant strains Halomonas variabilis (HT1 and Planococcus rifietoensis (RT4 have an ability to improve plant growth, These strains can form biofilm and accumulate exopolysacharides at increasing salt stress. These results showed that bacteria might be involved in developing microbial communities under salt stress and helpful in colonizing of bacterial strains to plant roots and soil particles. Eventually, it can add to the plant growth and soil structure. We investigated the comparative effect of exopolysacharide and biofilm formation in two bacterial strains Halomonas variabilis (HT1 and Planococcus rifietoensis (RT4 in response to varying salt stress. We found that biofilm formation and exopolysaccharide accumulation increased at higher salinity. To check the effect of bacterial inoculation on the plant (Cicer arietinum Var. CM-98 growth and soil aggregation, pot experiment was conducted by growing seedlings under salt stress. Inoculation of both strains increased plant growth at elevated salt stress. Weight of soil aggregates attached with roots and present in soil were added at higher salt concentrations compared to untreated controls. Soil aggregation was higher at plant roots under salinity. These results suggest the feasibility of using above strains in improving plant growth and soil fertility under salinity.

Microbial properties of soil aggregates created by earthworms and other factors: spherical and prismatic soil aggregates from unreclaimed post-mining sites

Czech Academy of Sciences Publication Activity Database

Frouz, J.; Krištůfek, Václav; Livečková, M.; van Loo, D.; Jacobs, P.; van Hoorebeke, L.

2011-01-01

Roč. 56, č. 1 (2011), s. 36-43 ISSN 0015-5632 R&D Projects: GA MŠk LC06066; GA MŠk 2B08023; GA AV ČR 1QS600660505 Institutional research plan: CEZ:AV0Z60660521 Keywords : microbial properties * earthworms * spherical and prismatic soil aggregates Subject RIV: EH - Ecology, Behaviour Impact factor: 0.677, year: 2011

Modification of strength properties of soil-aggregate system on ...

African Journals Online (AJOL)

Introduction. India is currently having a road network of 4.69 million kilometers. ... National Highways and State Highways, comprising only 3% of total road length, each carrying ... Two types of mixtures are specified in the code for soil – aggregate ..... performance of sabkha subgrade, Building and Environment, Vol. 41, No.

Predicting aggregate properties of soil communities vs. comunity structure in an agricultural setting

DEFF Research Database (Denmark)

Demšar, D.; Džeroski, S.; Debeljak, M.

2006-01-01

approach of producing one model for the aggregate target variable is worse than the more complex approach of producing multiple models and then calculating the aggregate variable from the model outputs. We do this by taking a dataset describing the agricultural events and soil biological parameters...

From Turnover-Oriented to Functional Soil Organic Matter Pools: a Lesson Learned from Stable Isotope Tracing

Science.gov (United States)

Cotrufo, M. F.

2016-12-01

Globally soils contain three times the amount of carbon (C) stored in the atmosphere, and 68% of this is stored in soil below 30cm. Changes to the size of the soil C stocks could significantly impact the net terrestrial-atmosphere CO2 exchange and thus either mitigate or increase concentrations of CO2. Yet we are currently unable to conduct reliable predictions of the direction and magnitude of soil C stock changes, since current soil C models fail to accurately capture the current understanding of how soil organic matter (SOM) forms and persists, and (2) the vertical movement and deep soil processing of SOM. We propose shifting soil C modelling approaches from a turnover-oriented approach to a more functional-oriented approach, where measurable SOM pools with specific function in soils, with respect to their physical structure (soluble versus particulate), microbial accessibility (free versus mineral or aggregate protection) and ability to transfer along the soil profile (through water flow or by mass transport) are represented. We will present experimental evidence from a number of studies conducted in the past few years using stable isotope tracing in support of incorporating a dissolved organic matter (DOM)-microbial path and a physical transfer of particulate organic matter path in SOM models. We will also show how, through the DOM-microbial path, fresh plant inputs quickly result in the formation of new mineral-associated organic matter.

Earthworms, soil-aggregates and organic matter decomposition in agro-ecosystems in the Netherlands

NARCIS (Netherlands)

Marinissen, J.C.

1995-01-01

The relationships between earthworm populations, soil aggregate stability and soil organic matter dynamics were studied at an experimental farm in The Netherlands.

Arable land in general is not favourable for earthworm growth. In the Lovinkhoeve fields under conventional management

Contrasting responses of bacterial and fungal communities to aggregate-size fractions and long-term fertilizations in soils of northeastern China.

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Liao, Hao; Zhang, Yuchen; Zuo, Qinyan; Du, Binbin; Chen, Wenli; Wei, Dan; Huang, Qiaoyun

2018-04-20

Soils, with non-uniform distribution of nutrients across different aggregate-size fractions, provide spatially heterogeneous microhabitats for microorganisms. However, very limited information is available on microbial distributions and their response to fertilizations across aggregate-size fractions in agricultural soils. Here, we examined the structures of bacterial and fungal communities across different aggregate-size fractions (2000-250 μm, 250-53 μm and fractions (>53 μm), especially 250-53 μm aggregates, which contain more soil C and N, are associated with greater microbial biomass and higher fungi/bacteria ratio. We firstly reported the fungal community composition in different aggregate-size fractions by HTS technology and found more Ascomycota but less Zygomycota in larger fractions with higher C content across all fertilization regimes. Fertilization and aggregate-size fractions significantly affect the compositions of bacterial and fungal communities although their effects are different. The bacterial community is mainly driven by fertilization, especially chemical fertilizers, and is closely related to the shifts of soil P (phosphorus). The fungal community is preferentially impacted by different aggregate-size fractions and is more associated with the changes of soil C and N. The distinct responses of microbial communities suggest different mechanisms controlling the assembly of soil bacterial and fungal communities at aggregate scale. The investigations of both bacterial and fungal communities could provide a better understanding on nutrient cycling across aggregate-size fractions. Copyright © 2018. Published by Elsevier B.V.

The Effect of Thermal Convection on Earth-Atmosphere CO2 Gas Exchange in Aggregated Soil

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Ganot, Y.; Weisbrod, N.; Dragila, M. I.

2011-12-01

Gas transport in soils and surface-atmosphere gas exchange are important processes that affect different aspects of soil science such as soil aeration, nutrient bio-availability, sorption kinetics, soil and groundwater pollution and soil remediation. Diffusion and convection are the two main mechanisms that affect gas transport, fate and emissions in the soils and in the upper vadose zone. In this work we studied CO2 soil-atmosphere gas exchange under both day-time and night-time conditions, focusing on the impact of thermal convection (TCV) during the night. Experiments were performed in a climate-controlled laboratory. One meter long columns were packed with matrix of different grain size (sand, gravel and soil aggregates). Air with 2000 ppm CO2 was injected into the bottom of the columns and CO2 concentration within the columns was continuously monitored by an Infra Red Gas Analyzer. Two scenarios were compared for each soil: (1) isothermal conditions, representing day time conditions; and (2) thermal gradient conditions, i.e., atmosphere colder than the soil, representing night time conditions. Our results show that under isothermal conditions, diffusion is the major mechanism for surface-atmosphere gas exchange for all grain sizes; while under night time conditions the prevailing mechanism is dependent on the air permeability of the matrix: for sand and gravel it is diffusion, and for soil aggregates it is TCV. Calculated CO2 flux for the soil aggregates column shows that the TCV flux was three orders of magnitude higher than the diffusive flux.

Dynamic aspects of soil organic matter and its relationship to the physical properties and fertility of soils

International Nuclear Information System (INIS)

Wagner, G.H.

1980-01-01

Soil organic matter plays a critical role in determining the physical, chemical, and biological nature of soils. Its dynamic nature is explored with reference to the cycling of C and N in the biosphere. Optimum soil structure is developed under a grass sod, but adequate water stable aggregates can be maintained under proper cultivation to ensure deep root penetration, rapid water infiltration for storage in the rooting zone, and the prevention of surface crusting. Perhaps the most important role of organic material is its prevention of soil erosion by directly stabilizing the soil during the growing season, providing residues for protection between crops, and improving surface aggregation to make the soil less subject to erosion. (author)

Contact angles of wetting and water stability of soil structure

Science.gov (United States)

Kholodov, V. A.; Yaroslavtseva, N. V.; Yashin, M. A.; Frid, A. S.; Lazarev, V. I.; Tyugai, Z. N.; Milanovskiy, E. Yu.

2015-06-01

From the soddy-podzolic soils and typical chernozems of different texture and land use, dry 3-1 mm aggregates were isolated and sieved in water. As a result, water-stable aggregates and water-unstable particles composing dry 3-1 mm aggregates were obtained. These preparations were ground, and contact angles of wetting were determined by the static sessile drop method. The angles varied from 11° to 85°. In most cases, the values of the angles for the water-stable aggregates significantly exceeded those for the water-unstable components. In terms of carbon content in structural units, there was no correlation between these parameters. When analyzing the soil varieties separately, the significant positive correlation between the carbon content and contact angle of aggregates was revealed only for the loamy-clayey typical chernozem. Based on the multivariate analysis of variance, the value of contact wetting angle was shown to be determined by the structural units belonging to water-stable or water-unstable components of macroaggregates and by the land use type. In addition, along with these parameters, the texture has an indirect effect.

Effects of Straw Incorporation on Soil Nutrients, Enzymes, and Aggregate Stability in Tobacco Fields of China

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Jiguang Zhang

2016-07-01

Full Text Available To determine the effects of straw incorporation on soil nutrients, enzyme activity, and aggregates in tobacco fields, we conducted experiments with different amounts of wheat and maize straw in Zhucheng area of southeast Shandong province for three years (2010–2012. In the final year of experiment (2012, straw incorporation increased soil organic carbon (SOC and related parameters, and improved soil enzyme activity proportionally with the amount of straw added, except for catalase when maize straw was used. And maize straw incorporation was more effective than wheat straw in the tobacco field. The percentage of aggregates >2 mm increased with straw incorporation when measured by either dry or wet sieving. The mean weight diameter (MWD and geometric mean diameter (GMD in straw incorporation treatments were higher than those in the no-straw control (CK. Maize straw increased soil aggregate stability more than wheat straw with the same incorporation amount. Alkaline phosphatase was significantly and negatively correlated with soil pH. Sucrase and urease were both significantly and positively correlated with soil alkali-hydrolysable N. Catalase was significantly but negatively correlated with soil extractable K (EK. The MWD and GMD by dry sieving had significantly positive correlations with SOC, total N, total K, and EK, but only significantly correlated with EK by wet sieving. Therefore, soil nutrients, metabolic enzyme activity, and aggregate stability might be increased by increasing the SOC content through the maize or wheat straw incorporation. Moreover, incorporation of maize straw at 7500 kg·hm−2 was the best choice to enhance soil fertility in the tobacco area of Eastern China.

Quantitative analysis of liquid penetration kinetics and slaking of aggregates as related to solid-liquid interfacial properties

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Goebel, Marc-O.; Woche, Susanne K.; Bachmann, Jörg

2012-06-01

SummaryAggregate stability is frequently shown to be enhanced by strong soil water repellency, however, there is limited systematic evidence on this effect for moderately (subcritically) water repellent soils. This study aimed to investigate the specific effects of interfacial properties on the liquid penetration kinetics in relation to the stability of subcritically water repellent aggregates (4-6.3 mm) from various arable and forest soils against breakdown by slaking. In contrast to many other studies, where aggregate stability was determined by wet sieving, we here assessed the stability by immersion of air-dry aggregates in water-ethanol solutions with surface tensions ranging from 30 to 70 mN m-1. This approach allowed a highly sensitive discrimination of different stability levels and the determination of breakdown kinetics also for less stable aggregates. Interfacial properties were characterized in terms of contact angle measured on crushed aggregates, θc, and calculated for intact aggregates, θi, based on infiltration measurements with water and ethanol. Aggregate stability turned out to be higher in forest soils compared to arable soils with topsoil aggregates generally found to be more stable than subsoil aggregates. For water repellent aggregates, characterized by contact angles >40° and low water infiltration rates (aggregates after 30 s of immersion was generally below 10%, whereas in case of the more wettable aggregates, characterized by contact angles 0.25 mm3 s-0.5) more than 80% of the aggregates were disrupted. In accordance, we found a close relationship between aggregate stability and wettability with differences between θc and θi being generally small. In addition, aggregate stability turned out to be related to organic carbon content. However, correlation analysis revealed that both persistence of aggregate stability and kinetics of aggregate breakdown were more strongly affected by the contact angle, θc (r = 0.90 and r = -0

Influence of low temperatures on aggregate disruption of heavy clay soils

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Jana Kozlovsky Dufková

2010-01-01

Full Text Available Heavy clay soils that are normally resistant to wind erosion, from study site Ostrožská Nová Ves si­tua­ted in the foothills of the Bílé Karpaty Mountains, Czech Republic, were a subject of laboratory analyses. The analyses should found out the influence of overwinter processes on disruption of soil aggregates and thus reason of vulnerability to soil loss by wind. Two overwinter processes were observed – freezing and thawing, and freeze-drying of the soil. Both processes have indicated the increasing of erodible fraction in dependence of water content of analysed soils. Exposed frozen clay soils that freeze-dries during the winter in the foothills of Bílé Karpaty, leaves soils highly erodible in late winter and early spring.

Afforestation impacts microbial biomass and its natural {sup 13}C and {sup 15}N abundance in soil aggregates in central China

Energy Technology Data Exchange (ETDEWEB)

Wu, Junjun; Zhang, Qian; Yang, Fan; Lei, Yao; Zhang, Quanfa; Cheng, Xiaoli, E-mail: xlcheng@fudan.edu.cn

2016-10-15

We investigated soil microbial biomass and its natural abundance of δ{sup 13}C and δ{sup 15}N in aggregates (> 2000 μm, 250–2000 μm, 53–250 μm and < 53 μm) of afforested (implementing woodland and shrubland plantations) soils, adjacent croplands and open area (i.e., control) in the Danjiangkou Reservoir area of central China. The afforested soils averaged higher microbial biomass carbon (MBC) and nitrogen (MBN) levels in all aggregates than in open area and cropland, with higher microbial biomass in micro-aggregates (< 250 μm) than in macro-aggregates (> 2000 μm). The δ{sup 13}C of soil microbial biomass was more enriched in woodland soils than in other land use types, while δ{sup 15}N of soil microbial biomass was more enriched compared with that of organic soil in all land use types. The δ{sup 13}C and δ{sup 15}N of microbial biomass were positively correlated with the δ{sup 13}C and δ{sup 15}N of organic soil across aggregates and land use types, whereas the {sup 13}C and {sup 15}N enrichment of microbial biomass exhibited linear decreases with the corresponding C:N ratio of organic soil. Our results suggest that shifts in the natural {sup 13}C and {sup 15}N abundance of microbial biomass reflect changes in the stabilization and turnover of soil organic matter (SOM) and thereby imply that afforestation can greatly impact SOM accumulation over the long-term. - Highlights: • Afforested soils averaged higher microbial biomass in all aggregates than cropland. • Microbial biomass was higher in micro-aggregates than in macro-aggregates. • δ{sup 13}C and δ{sup 15}N of microbe positively correlated with δ{sup 13}C and δ{sup 15}N of organic soil. • {sup 13}C and {sup 15}N enrichment of microbe was negatively related to with soil C:N ratio.

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.

Changes in soil aggregate stability under different irrigation doses of waste water

Science.gov (United States)

Morugán, Alicia; García-Orenes, Fuensanta; Mataix-Solera, Jorge; Arcenegui, Victoria; Bárcenas, Gema

2010-05-01

Freshwater availability and soil degradation are two of the most important environmental problems in the Mediterranean area acerbated by incorrect agricultural use of irrigation in which organic matter is not correctly managed, the use of low quality water for irrigation, and the inefficiency of dose irrigation. For these reasons strategies for saving water and for the restoration of the mean properties of soil are necessary. The use of treated waste water for the irrigation of agricultural land could be a good solution to these problems, as it reduces the utilization of fresh water and could potentially improve key soil properties. In this work we have been studying, for more than three years, the effects on soil properties of different doses of irrigation with waste water. Here we show the results on aggregate stability. The study is located in an agricultural area at Biar (Alicante, SE of Spain), with a crop of grape (Vitis labrusca). Three types of waters are being used in the irrigation of the soil: fresh water (control) (TC), and treated waste water from secondary (T2) and tertiary treatment (T3). Three different doses of irrigation have been applied to fit the efficiency of the irrigation to the crop and soil type: D10 (10 L m-2 every week during 17 months), D50 (50 L m-2 every fifteen days during 14 moths) and D30 (30 L m-2 every week during 6 months up to present day). The results showed a clear decrease of aggregate stability during the period we used the second dose (D50) independent of the type of water used. That dose of irrigation and frequency produced strong wetting and drying cycles (WD) in the soil, and this is suspected to be the main factor responsible for the results. When we changed the dose of irrigation to D30, reducing the quantity per event and increasing the frequency, the soil aggregate stability started to improve. This dose avoids strong drying periods between irrigation events and the aggregate stability is confirmed to be slowly

Experimental evidence and modelling of drought induced alternative stable soil moisture states

Science.gov (United States)

Robinson, David; Jones, Scott; Lebron, Inma; Reinsch, Sabine; Dominguez, Maria; Smith, Andrew; Marshal, Miles; Emmett, Bridget

2017-04-01

The theory of alternative stable states in ecosystems is well established in ecology; however, evidence from manipulation experiments supporting the theory is limited. Developing the evidence base is important because it has profound implications for ecosystem management. Here we show evidence of the existence of alternative stable soil moisture states induced by drought in an upland wet heath. We used a long-term (15 yrs) climate change manipulation experiment with moderate sustained drought, which reduced the ability of the soil to retain soil moisture by degrading the soil structure, reducing moisture retention. Moreover, natural intense droughts superimposed themselves on the experiment, causing an unexpected additional alternative soil moisture state to develop, both for the drought manipulation and control plots; this impaired the soil from rewetting in winter. Our results show the coexistence of three stable states. Using modelling with the Hydrus 1D software package we are able to show the circumstances under which shifts in soil moisture states are likely to occur. Given the new understanding it presents a challenge of how to incorporate feedbacks, particularly related to soil structure, into soil flow and transport models?

Role of wetting and drying cycles in formation and growth of soil aggregates

Science.gov (United States)

Ghezzehei, T. A.; Lopez, J. P.

2009-12-01

Soil structure directly determines important soil physical properties including porosity, hydraulic conductivity, water retention, and mechanical strength and indirectly influences most biological and chemical processes that occur in and around soil. In response to the various processes that occur within it, soil structure evolves continuously at multiple spatial and temporal scales. We hypothesize that the rhythm of the evolution is controlled by wetting and drying cycles. Here, we will present a mathematical description of the role of wetting and drying cycles in the formation and stabilization of soil aggregates with emphasis on two important roles of wetting and drying cycles: (1) transport and deposition of organic and inorganic cementing agents at the most effective locations, (2) chemical and physical alteration of cementing agents during desiccation and the resultant semi-permanent bonding (or bond hardening). Our results demonstrate that size and strength of aggregates are determined by particle size, degree of dryness, number of wetting-drying cycles, as well as concentration and solubility of dissolved and/or colloidal cementing agents. These results are in general agreement with experimental observations obtained from the literature.

ORGANIC CARBON AND CARBON STOCK: RELATIONS WITH PHYSICAL INDICATORS AND SOIL AGGREGATION IN AREAS CULTIVATED WITH SUGAR CANE

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Diego Tolentino de Lima

2017-08-01

Full Text Available Soil organic carbon and carbon stock influence, directly or indirectly, most of soil aggregate stability indicators. The objective of this study was to quantify the production of dry biomass (DB, total organic carbon (TOC and carbon stock (CStk in soil, and to evaluate their influence on some indicators of aggregation in an Oxisol at a Cerrado biome in Uberaba-MG, Brazil. The design was completely randomized blocks, in two evaluation periods: three and six cuts, at six depths (0-0.1, 0.1-0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5 and 0.5-0.6 m. It was evaluated: soil density (SD, volumetric humidity (VH, aggregate stability index (AEI, weighted mean diameter (WDA, mean diameter (GDA, index of aggregates with diameter greater than 2 mm (AI and sensitivity index (SI, replicated by 4. The best AEI of the soil and the highest TOC contents were found in the most superficial layers, 0 to 0.2 m, for both cuttings. The greater values of TOC and CStk, occurred at the sixth cut area, where there was a higher amount of DB on soil surface. The higher levels of organic matter did not provide higher AEI in the area of sixth cut, when compared to that of the third cut. The TOC and CStk levels in both areas generally had a positive influence on soil aggregation indicators for both cuts.

Effect of long-term combined application of organic and inorganic fertilizers on soil nematode communities within aggregates.

Science.gov (United States)

Zhang, Zhiyong; Zhang, Xiaoke; Mahamood, Md; Zhang, Shuiqing; Huang, Shaomin; Liang, Wenju

2016-08-09

A long-term fertilization experiment was conducted to examine the effects of different fertilization practices on nematode community composition within aggregates in a wheat-maize rotation system. The study was a randomized complete block design with three replicates. The experiment involved the following four treatments: no fertilizer, inorganic N, P and K fertilizer (NPK), NPK plus manure (NPKM) and NPK plus maize straw (NPKS). Soil samples were taken at 0-20 cm depth during the wheat harvest stage. Based on our results, NPKS contributed to soil aggregation and moisture retention, with a positive effect on soil total nitrogen accumulation, particularly within small macroaggregates (0.25-1 mm) and microaggregates (fertilizer application effectively improved soil physicochemical properties and were also beneficial for nematode survival within small aggregate size fractions.

The effects of arbuscular mycorrhizal fungi on glomalin-related soil protein distribution, aggregate stability and their relationships with soil properties at different soil depths in lead-zinc contaminated area.

Science.gov (United States)

Yang, Yurong; He, Chuangjun; Huang, Li; Ban, Yihui; Tang, Ming

2017-01-01

Glomalin-related soil protein (GRSP), a widespread glycoprotein produced by arbuscular mycorrhizal fungi (AMF), is crucial for ecosystem functioning and ecological restoration. In the present study, an investigation was conducted to comprehensively analyze the effects of heavy metal (HM) contamination on AMF status, soil properties, aggregate distribution and stability, and their correlations at different soil depths (0-10, 10-20, 20-30, 30-40 cm). Our results showed that the mycorrhizal colonization (MC), hyphal length density (HLD), GRSP, soil organic matter (SOM) and soil organic carbon (SOC) were significantly inhibited by Pb compared to Zn at 0-20 cm soil depth, indicating that HM had significant inhibitory effects on AMF growth and soil properties, and that Pb exhibited greater toxicity than Zn at shallow layer of soil. Both the proportion of soil large macroaggregates (>2000 μm) and mean weight diameter (MWD) were positively correlated with GRSP, SOM and SOC at 0-20 cm soil depth (P soil particles together into large macroaggregates and improving aggregate stability. Furthermore, MC and HLD had significantly positive correlation with GRSP, SOM and SOC, suggesting that AMF played an essential role in GRSP, SOM and SOC accumulation and subsequently influencing aggregate formation and particle-size distribution in HM polluted soils. Our study highlighted that the introduction of indigenous plant associated with AMF might be a successful biotechnological tool to assist the recovery of HM polluted soils, and that proper management practices should be developed to guarantee maximum benefits from plant-AMF symbiosis during ecological restoration.

Equivalent cylinder systems representing the soil matrix in diffusion-reaction models for an aggregated soil

NARCIS (Netherlands)

Rappoldt, C; Verhagen, JHG

1999-01-01

The structure of an aggregated soil or a dual-porosity medium is characterized by a function called the generalized surface-area-to-volume ratio, which can be measured as a distance distribution. For an isotropic structure the distance measurements may be done in the digitized image of a

Texture and organic carbon contents do not impact amount of carbon protected in Malagasy soils

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Tantely Razafimbelo

2013-06-01

Full Text Available Soil organic carbon (SOC is usually said to be well correlated with soil texture and soil aggregation. These relations generally suggest a physical and physicochemical protection of SOC within soil aggregates and on soil fine particles, respectively. Because there are few experimental evidences of these relations on tropical soils, we tested the relations of soil variables (SOC and soil aggregate contents, and soil texture with the amount of SOC physically protected in aggregates on a set of 15 Malagasy soils. The soil texture, the SOC and water stable macroaggregate (MA contents and the amount of SOC physically protected inside aggregates, calculated as the difference of C mineralized by crushed and intact aggregates, were characterized. The relation between these variables was established. SOC content was significantly correlated with soil texture (clay+fine silt fraction and with soil MA amount while protected SOC content was not correlated with soil MA amount. This lack of correlation might be attributed to the highest importance of physicochemical protection of SOC which is demonstrated by the positive relation between SOC and clay+fine silt fraction.

Quantifying and isolating stable soil organic carbon using long-term bare fallow experiment

DEFF Research Database (Denmark)

Barré, P; Eglin, T; Christensen, Bent Tolstrup

2010-01-01

. We analyzed data from six bare fallow experiments of long-duration (>30 yrs), covering a range of soil types and climate conditions, and sited at Askov (Denmark), Grignon and Versailles (France), Kursk (Russia), Rothamsted (UK), and Ultuna (Sweden). A conceptual three pool model dividing soil C...... into a labile pool (turnover time of a several years), an intermediate pool (turnover time of a several decades) and a stable pool (turnover time of a several centuries or more) fits well with the long term C decline observed in the bare fallow soils. The estimate of stable C ranged from 2.7 g C kg−1...... at Rothamsted to 6.8 g C kg−1 at Grignon. The uncertainty associated with estimates of the stable pool was large due to the short duration of the fallow treatments relative to the turnover time of stable soil C. At Versailles, where there is least uncertainty associated with the determination of a stable pool...

The Microbial Efficiency-Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter?

Science.gov (United States)

Cotrufo, M Francesca; Wallenstein, Matthew D; Boot, Claudia M; Denef, Karolien; Paul, Eldor

2013-04-01

The decomposition and transformation of above- and below-ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been largely uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling and storage. We present the current understanding of the importance of microbial substrate use efficiency and C and N allocation in controlling the proportion of plant-derived C and N that is incorporated into SOM, and of soil matrix interactions in controlling SOM stabilization. We synthesize this understanding into the Microbial Efficiency-Matrix Stabilization (MEMS) framework. This framework leads to the hypothesis that labile plant constituents are the dominant source of microbial products, relative to input rates, because they are utilized more efficiently by microbes. These microbial products of decomposition would thus become the main precursors of stable SOM by promoting aggregation and through strong chemical bonding to the mineral soil matrix. © 2012 Blackwell Publishing Ltd.

Soil aggregation and organic carbon of Oxisols under coffee in agroforestry systems

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Gabriel Pinto Guimarães

2014-02-01

Full Text Available Intensive land use can lead to a loss of soil physical quality with negative impacts on soil aggregates, resistance to root penetration, porosity, and bulk density. Organic and agroforestry management systems can represent sustainable, well-balanced alternatives in the agroecosystem for promoting a greater input of organic matter than the conventional system. Based on the hypothesis that an increased input of organic matter improves soil physical quality, this study aimed to evaluate the impact of coffee production systems on soil physical properties in two Red-Yellow Oxisols (Latossolos Vermelho-Amarelos in the region of Caparaó, Espirito Santo, Brazil. On Farm 1, we evaluated the following systems: primary forest (Pf1, organic coffee (Org1 and conventional coffee (Con1. On Farm 2, we evaluated: secondary forest (Sf2, organic coffee intercropped with inga (Org/In2, organic coffee intercropped with leucaena and inga (Org/In/Le2, organic coffee intercropped with cedar (Org/Ced2 and unshaded conventional coffee (Con2. Soil samples were collected under the tree canopy from the 0-10, 10-20 and 20-40 cm soil layers. Under organic and agroforestry coffee management, soil aggregation was higher than under conventional coffee. In the agroforestry system, the degree of soil flocculation was 24 % higher, soil moisture was 80 % higher, and soil resistance to penetration was lower than in soil under conventional coffee management. The macroaggregates in the organic systems, Org/In2, Org/In/Le2, and Org/Ced2 contained, on average, 29.1, 40.1 and 34.7 g kg-1 organic carbon, respectively. These levels are higher than those found in the unshaded conventional system (Con2, with 20.2 g kg-1.

Nitrite-Oxidizing Bacteria Community Composition and Diversity Are Influenced by Fertilizer Regimes, but Are Independent of the Soil Aggregate in Acidic Subtropical Red Soil.

Science.gov (United States)

Han, Shun; Li, Xiang; Luo, Xuesong; Wen, Shilin; Chen, Wenli; Huang, Qiaoyun

2018-01-01

Nitrification is the two-step aerobic oxidation of ammonia to nitrate via nitrite in the nitrogen-cycle on earth. However, very limited information is available on how fertilizer regimes affect the distribution of nitrite oxidizers, which are involved in the second step of nitrification, across aggregate size classes in soil. In this study, the community compositions of nitrite oxidizers ( Nitrobacter and Nitrospira ) were characterized from a red soil amended with four types of fertilizer regimes over a 26-year fertilization experiment, including control without fertilizer (CK), swine manure (M), chemical fertilization (NPK), and chemical/organic combined fertilization (MNPK). Our results showed that the addition of M and NPK significantly decreased Nitrobacter Shannon and Chao1 index, while M and MNPK remarkably increased Nitrospira Shannon and Chao1 index, and NPK considerably decreased Nitrospira Shannon and Chao1 index, with the greatest diversity achieved in soils amended with MNPK. However, the soil aggregate fractions had no impact on that alpha-diversity of Nitrobacter and Nitrospira under the fertilizer treatment. Soil carbon, nitrogen and phosphorus in the soil had a significant correlation with Nitrospira Shannon and Chao1 diversity index, while total potassium only had a significant correlation with Nitrospira Shannon diversity index. However, all of them had no significant correlation with Nitrobacter Shannon and Chao1 diversity index. The resistance indices for alpha-diversity indexes (Shannon and Chao1) of Nitrobacter were higher than those of Nitrospira in response to the fertilization regimes. Manure fertilizer is important in enhancing the Nitrospira Shannon and Chao1 index resistance. Principal co-ordinate analysis revealed that Nitrobacter - and Nitrospira -like NOB communities under four fertilizer regimes were differentiated from each other, but soil aggregate fractions had less effect on the nitrite oxidizers community. Redundancy analysis

Creating a soil-like profile for plant growth using tailings sand and fine tails

International Nuclear Information System (INIS)

Li, X.; Fung, M. P. Y.

1996-01-01

Development of a technology to create stable aggregates with a soil-like profile capable of supporting a stable plant community, was discussed as the major challenge and primary task in restoring oil sands processing wastes, and in re-creating a self-sustaining ecosystem. A procedure for creating a soil-like profile using oil sands mining wastes, was described. Clay and water content were critical factors in the aggregation procedure. A study to evaluate the physical, chemical and biological properties of these soils and their suitability as a plant growth medium is currently underway. 6 refs., 3 figs

Which soil tillage is better in terms of the soil organic matter and soil structure changes?

Directory of Open Access Journals (Sweden)

VLADIMÍR ŠIMANSKÝ

2016-06-01

Full Text Available This study was performed to evaluate effects of minimum (MT and conventional tillage (CT on soil organic matter and soil structure in haplic Chernozems and mollic Fluvisols. The content of soil organic carbon (Corg as well as parameters of stability and vulnerability of soil structure were quantified. The results showed that soil type had statistically significant influence on Corg. In haplic Chernozems the Corg content near the surface (0–0.1 m was significantly higher under MT (by 6% compared to CT, however, in layer 0–0.3 m under CT the average Corg content was by 16% higher than under MT. In mollic Fulvisols under MT, the average Corg content (17.5 ± 5.4 g*kg-1 was significantly less for the 0–0.3 m layer than the CT (22.7 ± 0.4 g*kg-1. In Chernozems, total content of water-stable micro-aggregates (WSAmi was higher in MT (90.8% than in CT (69.5%. In mollic Fluvisols, the average content of WSAmi was higher in CT (62.5% than in MT (53.2%. The low aggregate stability and the high structure vulnerability were reflected also due to the high contents of WSAmi in both soils. The stability of aggregates was a higher in mollic Fluvisols than in haplic Chernozems. In haplic Chernozems, better soil structure stability was under CT than MT, on the other hand, in mollic Fluvisols, the average value of coefficient of aggregate stability was lower by 32% in CT than MT.

Food choice of Antarctic soil arthropods clarified by stable isotope signatures

NARCIS (Netherlands)

Bokhorst, S.F.; Ronfort, C.; Huiskes, A.H.L.; Convey, P.; Aerts, R.A.M.

2007-01-01

Antarctic soil ecosystems are amongst the most simplified on Earth and include only few soil arthropod species, generally believed to be opportunistic omnivorous feeders. Using stable isotopic analyses, we investigated the food choice of two common and widely distributed Antarctic soil arthropod

Soil quality indicator responses to row crop, grazed pasture, and agroforestry buffer management

Science.gov (United States)

Incorporation of trees and establishment of grass buffers within agroecosystems are management practices shown to enhance soil quality. Soil enzyme activities and water stable aggregates (WSA) have been identified as sensitive soil quality indicators to evaluate early responses to soil management. ...

The effects of arbuscular mycorrhizal fungi on glomalin-related soil protein distribution, aggregate stability and their relationships with soil properties at different soil depths in lead-zinc contaminated area.

Directory of Open Access Journals (Sweden)

Yurong Yang

Full Text Available Glomalin-related soil protein (GRSP, a widespread glycoprotein produced by arbuscular mycorrhizal fungi (AMF, is crucial for ecosystem functioning and ecological restoration. In the present study, an investigation was conducted to comprehensively analyze the effects of heavy metal (HM contamination on AMF status, soil properties, aggregate distribution and stability, and their correlations at different soil depths (0-10, 10-20, 20-30, 30-40 cm. Our results showed that the mycorrhizal colonization (MC, hyphal length density (HLD, GRSP, soil organic matter (SOM and soil organic carbon (SOC were significantly inhibited by Pb compared to Zn at 0-20 cm soil depth, indicating that HM had significant inhibitory effects on AMF growth and soil properties, and that Pb exhibited greater toxicity than Zn at shallow layer of soil. Both the proportion of soil large macroaggregates (>2000 μm and mean weight diameter (MWD were positively correlated with GRSP, SOM and SOC at 0-20 cm soil depth (P < 0.05, proving the important contributions of GRSP, SOM and SOC for binding soil particles together into large macroaggregates and improving aggregate stability. Furthermore, MC and HLD had significantly positive correlation with GRSP, SOM and SOC, suggesting that AMF played an essential role in GRSP, SOM and SOC accumulation and subsequently influencing aggregate formation and particle-size distribution in HM polluted soils. Our study highlighted that the introduction of indigenous plant associated with AMF might be a successful biotechnological tool to assist the recovery of HM polluted soils, and that proper management practices should be developed to guarantee maximum benefits from plant-AMF symbiosis during ecological restoration.

Relationship between chemical structure of soil organic matter and intra-aggregate pore structure: evidence from X-ray computed micro-tomography

Science.gov (United States)

Kravchenko, Alexandra; Grandy, Stuart A.

2014-05-01

Understanding chemical structure of soil organic matter (SOM) and factors that affect it are vital for gaining understanding of mechanisms of C sequestration by soil. Physical protection of C by adsorption to mineral particles and physical disconnection between C sources and microbial decomposers is now regarded as the key component of soil C sequestration. Both of the processes are greatly influenced by micro-scale structure and distribution of soil pores. However, because SOM chemical structure is typically studied in disturbed (ground and sieved) soil samples the experimental evidence of the relationships between soil pore structure and chemical structure of SOM are still scarce. Our study takes advantage of the X-ray computed micro-tomography (µ-CT) tools that enable non-destructive analysis of pore structure in intact soil samples. The objective of this study is to examine the relationship between SOM chemical structure and pore-characteristics in intact soil macro-aggregates from two contrasting long-term land uses. The two studied land use treatments are a conventionally tilled corn-soybean-wheat rotation treatment and a native succession vegetation treatment removed from agricultural use >20 years ago. The study is located in southwest Michigan, USA, on sandy-loam Typic Hapludalfs. For this study we used soil macro-aggregates 4-6 mm in size collected at 0-15 cm depth. The aggregate size was selected so as both to enable high resolution of µ-CT and to provide sufficient amount of soil for C measurements. X-ray µ-CT scanning was conducted at APS Argonne at a scanning resolution of 14 µm. Two scanned aggregates (1 per treatment) were used in this preliminary study. Each aggregate was cut into 7 "geo-referenced" sections. Analyses of pore characteristics in each section were conducted using 3DMA and ImageJ image analysis tools. SOM chemistry was analyzed using pyrolysis/gas chromatography-mass spectroscopy. Results demonstrated that the relationships

In Situ Earthworm Breeding to Improve Soil Aggregation, Chemical Properties, and Enzyme Activity in Papayas

Directory of Open Access Journals (Sweden)

Huimin Xiang

2018-04-01

Full Text Available The long-term use of mineral fertilizers has decreased the soil fertility in papaya (Carica papaya L. orchards in South China. In situ earthworm breeding is a new sustainable practice for improving soil fertility. A field experiment was conducted to compare the effects of four treatments consisting of the control (C, chemical fertilizer (F, compost (O, and in situ earthworm breeding (E on soil physico-chemical properties and soil enzyme activity in a papaya orchard. The results showed that soil chemical properties, such as pH, soil organic matter (SOM, total nitrogen (TN, available nitrogen (AN, and total phosphorus (TP were significantly improved with the E treatment but declined with the F treatment. On 31 October 2008, the SOM and TN with the O and E treatments were increased by 26.3% and 15.1%, respectively, and by 32.5% and 20.6% compared with the F treatment. Furthermore, the O and E treatments significantly increased the activity of soil urease and sucrase. Over the whole growing season, soil urease activity was 34.4%~40.4% and 51.1%~58.7% higher with the O and E treatments, respectively, than that with the C treatment. Additionally, the activity of soil sucrase with the E treatment was always the greatest of the four treatments, whereas the F treatment decreased soil catalase activity. On 11 June 2008 and 3 July 2008, the activity of soil catalase with the F treatment was decreased by 19.4% and 32.0% compared with C. Soil bulk density with the four treatments was in the order of O ≤ E < F < C. The O- and E-treated soil bulk density was significantly lower than that of the F-treated soil. Soil porosity was in the order of C < F < E < O. Soil porosity with the O and E treatments was 6.0% and 4.7% higher, respectively, than that with the F treatment. Meanwhile, the chemical fertilizer applications significantly influenced the mean weight diameter (MWD of the aggregate and proportion of different size aggregate fractions. The E treatment

Soil quality parameters for row-crop and grazed pasture systems with agroforestry buffers

Science.gov (United States)

Incorporation of trees and establishment of buffers are practices that can improve soil quality. Soil enzyme activities and water stable aggregates are sensitive indices for assessing soil quality by detecting early changes in soil management. However, studies comparing grazed pasture and row crop...

Results of field studies on 90SR and stable SR soil-to-plant transfer

International Nuclear Information System (INIS)

Gerzabek, M.H.; Artner, C.; Horak, O.; Mueck, K.

1992-01-01

In 1987 and 1988 at 35 sites plants ready to harvest and the corresponding soils (0 - 20 cm) were collected for 90 Sr and stable strontium analyses. Sample preparation and measurement led to a detection limit of 0.008 Bq 90 Sr kg -1 . The 90 Sr-contamination of Austrian soils ranged from 396 to 1998 Bq m -2 . Known from literature the contribution of the Chernobyl fallout amounted to app. 25 % of the total contamination. Stable strontium contents of the soils were between 6 and 62.5 mg kg -1 . Bariumtriethanolamine extracted 17.7 to 62.3 % of the total stable Sr in soil. 90 Sr-concentrations in cereal grains ranged from 0.03 to 0.67 Bq kg -1 (fresh wight) for maize and barley, respectively. The values for other foodstuff were between 0.15 (white cabbage) and 0.91 Bq kg -1 (spinach). Stable strontium contents were between 0.079 mg kg -1 (maize) and 72.5 mg kg -1 (celery shoot). The following mean 90 Sr soil-to-plant transfer factors for cereal grains were obtained: 0.010 (maize), 0.097 (rye), 0.049 (wheat), 0.095 (barley). Transfer factors for straw were up to 50 times higher (maize). The transfer of 90 Sr into vegetables and potatoes reached the same order of magnitude compared to the cereals. In all cases soil-to-plant transfer of stable Sr was clearly lower up to 60 % of the respective values for 90 Sr. Thus natural stable strontium is less plant available than 90 Sr. The influence of soil parameters on the 90 Sr transfer into plants was examinated by correlation analyses. Increasing exchangeable calcium contents of the soils resulted in a significant reduction of Sr soil-to-barley straw transfer. (authors)

Composition and structure of aggregates from compacted soil horizons in the southern steppe zone of European Russia

Science.gov (United States)

Sorokin, A. S.; Abrosimov, K. N.; Lebedeva, M. P.; Kust, G. S.

2016-03-01

The composition and structure of aggregates from different agrogenic soils in the southern steppe zone of European Russia have been studied. It is shown that the multi-level study (from the macro- to microlevel) of these horizons makes it possible to identify soil compaction caused by different elementary soil processes: solonetz-forming, vertisol-forming, and mechanical (wheel) compaction in the rainfed and irrigated soils. The understanding of the genesis of the compaction of soil horizons (natural or anthropogenic) is important for the economic evaluation of soil degradation. It should enable us to make more exact predictions of the rates of degradation processes and undertake adequate mitigation measures. The combined tomographic and micromorphological studies of aggregates of 1-2 and 3-5 mm in diameter from compacted horizons of different soils have been performed for the first time. Additional diagnostic features of negative solonetz- forming processes (low open porosity of aggregates seen on tomograms and filling of a considerable part of the intraped pores with mobile substance) and the vertisol-forming processes (large amount of fine intraaggregate pores seen on tomograms and a virtual absence of humus-clay plasma in the intraped zone)—have been identified. It is shown that the combination of microtomographic and micromorphological methods is helpful for studying the pore space of compacted horizons in cultivated soils.

Neutral hydrolysable sugars, OC and N content across soil aggregate size fractions, as an effect of two different crop rotations

Science.gov (United States)

Angeletti, Carlo; Giannetta, Beatrice; Kölbl, Angelika; Monaci, Elga; Kögel-Knabner, Ingrid; Vischetti, Costantino

2016-04-01

This paper presents the results regarding the effects of two 13 years long crop rotations, on the composition of mineral associated neutral sugars, organic carbon (OC) and N concentration, across different aggregate size fractions. The two cropping sequences were characterized by different levels of N input from plant residues and tillage frequency. We also analysed the changes that occurred in soil organic matter (SOM) chemical composition following the cultivation in the two soils of winter wheat and chickpea on the same soils. The analysis of OC and N content across soil aggregate fractions allowed getting an insight into the role played by SOM chemical composition in the formation of organo-mineral associations, while neutral sugars composition provided information on mineral associated SOM origin and decomposition processes, as pentoses derive mostly from plant tissues and hexoses are prevalently of microbial origin. Soil samples were collected from two adjacent fields, from the 0-10 cm layer, in November 2011 (T0). For 13 years before the beginning of the experiment, one soil was cultivated mostly with alfalfa (ALF), while a conventional cereal-sunflower-legume rotation (CON) was carried out on the other. Winter wheat and chickpea were sown on the two soils during the following 2 growing seasons and the sampling was repeated after 18 months (T1). A combination of aggregates size and density fractionation was used to isolate OM associated with mineral particles in: macro-aggregates (>212 μm), micro-aggregates ( 63 μm) and silt and clay size particles (carbohydrates contributions in every other fraction. GM/AX varied slightly between the soils. In conclusion, the crop rotation determined the accumulation of different levels of SOM in the two soils. The 18-months cultivation experiment determined an increase in the tillage intensity in ALF, and the introduction of N rich chickpea residues in CON. Consequently SOM chemical composition responded divergently in

Differences in SOM decomposition and temperature sensitivity among soil aggregate size classes in a temperate grasslands.

Science.gov (United States)

Wang, Qing; Wang, Dan; Wen, Xuefa; Yu, Guirui; He, Nianpeng; Wang, Rongfu

2015-01-01

The principle of enzyme kinetics suggests that the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition is inversely related to organic carbon (C) quality, i.e., the C quality-temperature (CQT) hypothesis. We tested this hypothesis by performing laboratory incubation experiments with bulk soil, macroaggregates (MA, 250-2000 μm), microaggregates (MI, 53-250 μm), and mineral fractions (MF, temperature and aggregate size significantly affected on SOM decomposition, with notable interactive effects (Ptemperature in the following order: MA>MF>bulk soil >MI(P classes (P temperature is closely associated withsoil aggregation and highlights the complex responses of ecosystem C budgets to future warming scenarios.

Stable and radioactive carbon in Indian soils: implications to soil carbon dynamics

International Nuclear Information System (INIS)

Laskar, A.H.; Yadava, M.G.; Ramesh, R.

2011-01-01

Radiocarbon is a very useful tool to study soil carbon dynamic. The mean residence time of SOC in Indian soils is about a century at the top 0-15 cm, increases linearly to reach values ranging from 2000 to 4000 yrs at a depth of 100 cm. It mainly depends on the clay content indicating that the clay is the main governing factor for SOC stabilization. Stable carbon and oxygen isotopes in soil carbonates and SOC are good proxies for paleoclimate and paleovegetation reconstruction. The present day sub-humid climate in the lower Narmada valley has been established prior to ∼ 3 ka. Two comparatively arid phases around 2.1 and 1.3 ka are recorded by oxygen isotopes of soil carbonates; consistent with other proxy records showing its regional significance

Treated wastewater irrigation effects on soil hydraulic conductivity and aggregate stability of loamy soils in Israel

Directory of Open Access Journals (Sweden)

Schacht Karsten

2015-03-01

Full Text Available The use of treated wastewater (TWW for agricultural irrigation becomes increasingly important in water stressed regions like the Middle East for substituting fresh water (FW resources. Due to elevated salt concentrations and organic compounds in TWW this practice has potential adverse effects on soil quality, such as the reduction of hydraulic conductivity (HC and soil aggregate stability (SAS. To assess the impact of TWW irrigation in comparison to FW irrigation on HC, in-situ infiltration measurements using mini disk infiltrometer were deployed in four different long-term experimental orchard test sites in Israel. Topsoil samples (0-10 cm were collected for analyzing SAS and determination of selected soil chemical and physical characteristics.

Modeling Soil Carbon Dynamics in Northern Forests: Effects of Spatial and Temporal Aggregation of Climatic Input Data.

Science.gov (United States)

Dalsgaard, Lise; Astrup, Rasmus; Antón-Fernández, Clara; Borgen, Signe Kynding; Breidenbach, Johannes; Lange, Holger; Lehtonen, Aleksi; Liski, Jari

2016-01-01

Boreal forests contain 30% of the global forest carbon with the majority residing in soils. While challenging to quantify, soil carbon changes comprise a significant, and potentially increasing, part of the terrestrial carbon cycle. Thus, their estimation is important when designing forest-based climate change mitigation strategies and soil carbon change estimates are required for the reporting of greenhouse gas emissions. Organic matter decomposition varies with climate in complex nonlinear ways, rendering data aggregation nontrivial. Here, we explored the effects of temporal and spatial aggregation of climatic and litter input data on regional estimates of soil organic carbon stocks and changes for upland forests. We used the soil carbon and decomposition model Yasso07 with input from the Norwegian National Forest Inventory (11275 plots, 1960-2012). Estimates were produced at three spatial and three temporal scales. Results showed that a national level average soil carbon stock estimate varied by 10% depending on the applied spatial and temporal scale of aggregation. Higher stocks were found when applying plot-level input compared to country-level input and when long-term climate was used as compared to annual or 5-year mean values. A national level estimate for soil carbon change was similar across spatial scales, but was considerably (60-70%) lower when applying annual or 5-year mean climate compared to long-term mean climate reflecting the recent climatic changes in Norway. This was particularly evident for the forest-dominated districts in the southeastern and central parts of Norway and in the far north. We concluded that the sensitivity of model estimates to spatial aggregation will depend on the region of interest. Further, that using long-term climate averages during periods with strong climatic trends results in large differences in soil carbon estimates. The largest differences in this study were observed in central and northern regions with strongly

Infiltration of water in disturbed soil columns as affected by clay dispersion and aggregate slaking

OpenAIRE

Amezketa, E.; Aragües, R.; Gazol, R.

2004-01-01

Soil crusting negatively affects the productivity and sustainability of irrigated agriculture, reducing water infiltration and plant emergence, and enhancing surface runoff and erosion. Clay dispersion and slaking of the aggregates at the soil surface are the main processes responsible for crusting. The infiltration rates (IR) of ten arid-zone soils in disturbed soil columns were measured and their relative susceptibilities to dispersion and slaking were determined. It was also examined wheth...

Colloid Release From Differently Managed Loess Soil

DEFF Research Database (Denmark)

Vendelboe, Anders Lindblad; Schjønning, Per; Møldrup, Per

2012-01-01

The content of water-dispersible colloids (WDC) in a soil can have a major impact on soil functions, such as permeability to water and air, and on soil strength, which can impair soil fertility and workability. In addition, the content of WDC in the soil may increase the risk of nutrient loss...... and of colloid-facilitated transport of strongly sorbing compounds. In the present study, soils from the Bad Lauchsta¨dt longterm static fertilizer experiment with different management histories were investigated to relate basic soil properties to the content of WDC, the content of water-stable aggregates (WSA......), and aggregate tensile strength. Our studies were carried out on soils on identical parent material under controlled management conditions, enabling us to study the long-term effects on soil physical properties with few explanatory variables in play. The content of WDC and the amount of WSA were measured...

TGP, an extremely stable, non-aggregating fluorescent protein created by structure-guided surface engineering

Science.gov (United States)

Close, Devin W.; Don Paul, Craig; Langan, Patricia S.; Wilce, Matthew C.J.; Traore, Daouda A.K.; Halfmann, Randal; Rocha, Reginaldo C.; Waldo, Geoffery S.; Payne, Riley J.; Rucker, Joseph B.; Prescott, Mark; Bradbury, Andrew R.M.

2014-01-01

In this paper we describe the engineering and X-ray crystal structure of Thermal Green Protein (TGP), an extremely stable, highly soluble, non-aggregating green fluorescent protein. TGP is a soluble variant of the fluorescent protein eCGP123, which despite being highly stable, has proven to be aggregation-prone. The X-ray crystal structure of eCGP123, also determined within the context of this paper, was used to carry out rational surface engineering to improve its solubility, leading to TGP. The approach involved simultaneously eliminating crystal lattice contacts while increasing the overall negative charge of the protein. Despite intentional disruption of lattice contacts and introduction of high entropy glutamate side chains, TGP crystallized readily in a number of different conditions and the X-ray crystal structure of TGP was determined to 1.9 Å resolution. The structural reasons for the enhanced stability of TGP and eCGP123 are discussed. We demonstrate the utility of using TGP as a fusion partner in various assays and significantly, in amyloid assays in which the standard fluorescent protein, EGFP, is undesirable because of aberrant oligomerization. PMID:25287913

State-Space Estimation of Soil Organic Carbon Stock

Science.gov (United States)

Ogunwole, Joshua O.; Timm, Luis C.; Obidike-Ugwu, Evelyn O.; Gabriels, Donald M.

2014-04-01

Understanding soil spatial variability and identifying soil parameters most determinant to soil organic carbon stock is pivotal to precision in ecological modelling, prediction, estimation and management of soil within a landscape. This study investigates and describes field soil variability and its structural pattern for agricultural management decisions. The main aim was to relate variation in soil organic carbon stock to soil properties and to estimate soil organic carbon stock from the soil properties. A transect sampling of 100 points at 3 m intervals was carried out. Soils were sampled and analyzed for soil organic carbon and other selected soil properties along with determination of dry aggregate and water-stable aggregate fractions. Principal component analysis, geostatistics, and state-space analysis were conducted on the analyzed soil properties. The first three principal components explained 53.2% of the total variation; Principal Component 1 was dominated by soil exchange complex and dry sieved macroaggregates clusters. Exponential semivariogram model described the structure of soil organic carbon stock with a strong dependence indicating that soil organic carbon values were correlated up to 10.8m.Neighbouring values of soil organic carbon stock, all waterstable aggregate fractions, and dithionite and pyrophosphate iron gave reliable estimate of soil organic carbon stock by state-space.

Wettability, soil organic matter and structure-properties of typical chernozems under the forest and under the arable land

Science.gov (United States)

Bykova, Galina; Umarova, Aminat; Tyugai, Zemfira; Milanovskiy, Evgeny; Shein, Evgeny

2017-04-01

Intensive tillage affects the properties of soil: decrease in content of soil organic matter and in hydrophobicity of the soil's solid phase, the reduction of amount of water stable aggregates - all this leads to deterioration of the structure of the soil and affects the process of movement of moisture in the soil profile. One of the hypotheses of soil's structure formation ascribes the formation of water stable aggregates with the presence of hydrophobic organic substances on the surface of the soil's solid phase. The aim of this work is to study the effect of tillage on properties of typical chernozems (pachic Voronic Chernozems, Haplic Chernozems) (Russia, Kursk region), located under the forest and under the arable land. The determination of soil-water contact angle was performed by a Drop Shape Analyzer DSA100 (Krüss GmbH, Germany) by the static sessile drop method. For all samples the content of total and organic carbon by dry combustion in oxygen flow and the particle size distribution by the laser diffraction method on the device Analysette 22 comfort, FRITCH, Germany were determined. The estimation of aggregate composition was performed by dry sieving (AS 200, Retsch, Germany), the content of water stable aggregates was estimated by the Savvinov method. There was a positive correlation between the content of organic matter and soil's wettability in studied soils, a growth of contact angle with the increasing the content of organic matter. Under the forest the content of soil organic matter was changed from 6,41% on the surface up to 1,9% at the depth of 100 cm. In the Chernozem under the arable land the organic carbon content in arable horizon is almost two times less. The maximum of hydrophobicity (78.1o) was observed at the depth of 5 cm under the forest. In the profile under the arable land the contact angle value at the same depth was 50o. The results of the structure analysis has shown a decrease in the content of agronomically valuable and water

The SAWO (Small And Well Organized) avatar teaches the importance of the aggregates on the soil system and how to determine their stability

Science.gov (United States)

Mataix-Solera, Jorge; Cerdà, Artemi; Jordán, Antonio; Úbeda, Xavier; Pereira, Paulo

2015-04-01

Soil structure is the key factor that determine the soil quality as control the organic matter turnnover, soil biology and soil erodibility (Cerdà, 1996; 1998; Wick et al., 2014; Gelaw, 2015). There is a need to understand better the factors and the processes that act on the soil aggregation and the dynamics of the soil aggregation, which will make easier to understand the soil system functioning (Jordán et al., 2011; Jordán et al., 2012; Pulido Moncada et al., 2013). Fire, mines, grazing and agricultura (Cerdà, 2000; Mataix Solera et al., 2011; Cerdà et al., 2012; Hallett et al., 2014; Lozano et al., 2013) determines how the soil structure is highly affected by the humankind. And this determines the sustainability of the land managements (García Orenes et al., 2012; K¨ropfl et al., 2013; Mekuria and Aynekulu, 2013; Taguas et al., 2013; Zhao et al., 2013). Aggregates are Small And Well Organized (SAWO) structures that allow the water to flow, the air fill the porous and the life to be diverse and abundant in the soil. The SAWO avatar will teach the importance of the functions and the services of the aggregates to students and other scientists, but also to any audience. This means that the experiments and the vocabulary to be used by SAWO will be very wide and rich. The Avatar SAWO will use different strategies and skills to teach the soil aggregation properties and characteristics. And also, how to measure. Easy to carry out experiments will be shown by SAWO to measure the aggregate stability in the field and in the laboratory, and the soil sampling in the field. The SAWO avatar will play a special attention to the impact of forest fires on aggregate stability changes and how to measure. The SAWO avatar will teach how to take samples in the field, how to transport and manage in the laboratory, and finally which measurements and test can be done to determine the aggregate stability. Acknowledgements To the "Ministerio de Economía and Competitividad" of

'Fingerprints' of four crop models as affected by soil input data aggregation

DEFF Research Database (Denmark)

Angulo, Carlos; Gaiser, Thomas; Rötter, Reimund P

2014-01-01

for all models. Further analysis revealed that the small influence of spatial resolution of soil input data might be related to: (a) the high precipitation amount in the region which partly masked differences in soil characteristics for water holding capacity, (b) the loss of variability in hydraulic soil...... properties due to the methods applied to calculate water retention properties of the used soil profiles, and (c) the method of soil data aggregation. No characteristic “fingerprint” between sites, years and resolutions could be found for any of the models. Our results support earlier recommendation....... In this study we used four crop models (SIMPLACE, DSSAT-CSM, EPIC and DAISY) differing in the detail of modeling above-ground biomass and yield as well as of modeling soil water dynamics, water uptake and drought effects on plants to simulate winter wheat in two (agro-climatologically and geo...

[Effect of L-arginine on platelet aggregation, endothelial function adn exercise tolerance in patients with stable angina pectoris].

Science.gov (United States)

Sozykin, A V; Noeva, E A; Balakhonova, T V; Pogorelova, O A; Men'shikov, M Iu

2000-01-01

Examination of the action of donor NO (L-arginine) on platelet aggregation, endothelial function and exercise tolerance in patients with stable angina of effort (SAE). 42 patients with SAE (functional class I-II) and 10 healthy volunteers (control group) were assigned to two groups. 22 patients of group 1 were randomized to cross-over. They received cardiket (60 mg/day for 10 days or cardiket (60 mg/day) in combination with L-arginine (15 g/day for 10 days). 20 SAE patients of group 2 and control group received L-arginine (15 g/day for 10 days). In each group blood lipids were examined, and bicycle exercise test (BET) was performed. In addition, platelet aggregation and endothelial function were studied in group 2 and control group before and after the course of L-arginine. Compared to control group, endothelial function significantly improved in group 2 (from 5.0 +/- 2.9 to 7.8 +/- 4.1% vs 7.1 +/- 1.9 to 6.6 +/- 4.8%) (M +/- SD). BET duration increased in all the patients. After ADP addition in concentrations 1.5, 2.0, and 5.0 micromol/l platelet aggregation declined in 17 patients except 3 in whom the aggregation remained unchanged. Positive effect of L-arginine on endothelial function, exercise tolerance and platelet aggregation was observed in patients with stable angina of effort (functional class I-II). Therefore, arginine can be recommended as an adjuvant in the treatment of patients with ischemic heart disease.

Abundant and stable char residues in soils: implications for soil fertility and carbon sequestration.

Science.gov (United States)

Mao, J-D; Johnson, R L; Lehmann, J; Olk, D C; Neves, E G; Thompson, M L; Schmidt-Rohr, K

2012-09-04

Large-scale soil application of biochar may enhance soil fertility, increasing crop production for the growing human population, while also sequestering atmospheric carbon. But reaching these beneficial outcomes requires an understanding of the relationships among biochar's structure, stability, and contribution to soil fertility. Using quantitative (13)C nuclear magnetic resonance (NMR) spectroscopy, we show that Terra Preta soils (fertile anthropogenic dark earths in Amazonia that were enriched with char >800 years ago) consist predominantly of char residues composed of ~6 fused aromatic rings substituted by COO(-) groups that significantly increase the soils' cation-exchange capacity and thus the retention of plant nutrients. We also show that highly productive, grassland-derived soils in the U.S. (Mollisols) contain char (generated by presettlement fires) that is structurally comparable to char in the Terra Preta soils and much more abundant than previously thought (~40-50% of organic C). Our findings indicate that these oxidized char residues represent a particularly stable, abundant, and fertility-enhancing form of soil organic matter.

The fate of silver nanoparticles in soil solution--Sorption of solutes and aggregation.

Science.gov (United States)

Klitzke, Sondra; Metreveli, George; Peters, Andre; Schaumann, Gabriele E; Lang, Friederike

2015-12-01

Nanoparticles enter soils through various pathways. In the soil, they undergo various interactions with the solution and the solid phase. We tested the following hypotheses using batch experiments: i) the colloidal stability of Ag NP increases through sorption of soil-borne dissolved organic matter (DOM) and thus inhibits aggregation; ii) the presence of DOM suppresses Ag oxidation; iii) the surface charge of Ag NP governs sorption onto soil particles. Citrate-stabilized and bare Ag NPs were equilibrated with (colloid-free) soil solution extracted from a floodplain soil for 24h. Nanoparticles were removed through centrifugation. Concentrations of free Ag ions and DOC, the specific UV absorbance at a wavelength of 254 nm, and the absorption ratio α254/α410 were determined in the supernatant. Nanoparticle aggregation was studied using time-resolved dynamic light scattering (DLS) measurement following the addition of soil solution and 1.5mM Ca(2+) solution. To study the effect of surface charge on the adsorption of Ag NP onto soil particles, bare and citrate-stabilized Ag NP, differing in the zeta potential, were equilibrated with silt at a solid-to-solution ratio of 1:10 and an initial Ag concentration range of 30 to 320 μg/L. Results showed that bare Ag NPs sorb organic matter, with short-chained organic matter being preferentially adsorbed over long-chained, aromatic organic matter. Stabilizing effects of organic matter only come into play at higher Ag NP concentrations. Soil solution inhibits the release of Ag(+) ions, presumably due to organic matter coatings. Sorption to silt particles was very similar for the two particle types, suggesting that the surface charge does not control Ag NP sorption. Besides, sorption was much lower than in comparable studies with sand and glass surfaces. Copyright © 2014. Published by Elsevier B.V.

[Impact of Land Utilization Pattern on Distributing Characters of Labile Organic Carbon in Soil Aggregates in Jinyun Mountain].

Science.gov (United States)

Li, Rui; Jiang, Chang-sheng; Hao, Qing-ju

2015-09-01

Four land utilization patterns were selected for this study in Jinyun mountain, including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land. Soil samples were taken every 10 cm in the depth of 60 cm soil and proportions of large macroaggregates (> 2 mm), small macroaggregates (0. 25-2 mm), microaggregates (0. 053 - 0. 25 mm) and silt + clay (organic carbon and labile organic carbon in each aggregate fraction and analyze impacts of land uses on organic carbon and labile organic carbon of soil aggregates. LOC content of four soil aggregates were significantly reduced with the increase of soil depth; in layers of 0-60 cm soil depth, our results showed that LOC contents of forest and abandoned land were higher than orchard and sloping farmland. Reserves of labile organic carbon were estimated by the same soil quality, it revealed that forest (3. 68 Mg.hm-2) > abandoned land (1. 73 Mg.hm-2) > orchard (1. 43 Mg.hm-2) >sloping farmland (0.54 Mg.hm-2) in large macroaggregates, abandoned land (7.77, 5. 01 Mg.hm-2) > forest (4. 96, 2.71 Mg.hm-2) > orchard (3. 33, 21. 10 Mg.hm-2) > sloping farmland (1. 68, 1. 35 Mg.hm-2) in small macroaggregates and microaggregates, and abandoned land(4. 32 Mg.hm-2) > orchard(4. 00 Mg.hm-2) > forest(3. 22 Mg.hm-2) > sloping farmland (2.37 Mg.hm-2) in silt + clay, forest and abandoned land were higher than orchard and sloping farmland in other three soil aggregates except silt + clay. It was observed that the level of organic carbon and labile organic carbon were decreased when bringing forest under cultivation to orchard or farmland, and augments on organic carbon and labile organic carbon were found after exchanging farmland to abandoned land. The most reverses of forest and abandoned land emerged in small macroaggregates, orchard and sloping farmland were in microaggregates. That was, during the transformations of land utilization pattern, soil aggregates with bigger size were

[Aluminum dissolution and changes of pH in soil solution during sorption of copper by aggregates of paddy soil].

Science.gov (United States)

Xu, Hai-Bo; Zhao, Dao-Yuan; Qin, Chao; Li, Yu-Jiao; Dong, Chang-Xun

2014-01-01

Size fractions of soil aggregates in Lake Tai region were collected by the low-energy ultrasonic dispersion and the freeze-desiccation methods. The dissolution of aluminum and changes of pH in soil solution during sorption of Cu2+ and changes of the dissolution of aluminum at different pH in the solution of Cu2+ by aggregates were studied by the equilibrium sorption method. The results showed that in the process of Cu2+ sorption by aggregates, the aluminum was dissoluted and the pH decreased. The elution amount of aluminum and the decrease of pH changed with the sorption of Cu2+, both increasing with the increase of Cu2+ sorption. Under the same conditions, the dissolution of aluminum and the decrease of pH were in the order of coarse silt fraction > silt fraction > sand fraction > clay fraction, which was negatively correlated with the amount of iron oxide, aluminum and organic matter. It suggested that iron oxide, aluminum and organic matters had inhibitory and buffering effect on the aluminum dissolution and the decrease of pH during the sorption of Cu2+.

Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition.

Science.gov (United States)

Potapov, Anton M; Tiunov, Alexei V; Scheu, Stefan

2018-06-19

Despite the major importance of soil biota in nutrient and energy fluxes, interactions in soil food webs are poorly understood. Here we provide an overview of recent advances in uncovering the trophic structure of soil food webs using natural variations in stable isotope ratios. We discuss approaches of application, normalization and interpretation of stable isotope ratios along with methodological pitfalls. Analysis of published data from temperate forest ecosystems is used to outline emerging concepts and perspectives in soil food web research. In contrast to aboveground and aquatic food webs, trophic fractionation at the basal level of detrital food webs is large for carbon and small for nitrogen stable isotopes. Virtually all soil animals are enriched in 13 C as compared to plant litter. This 'detrital shift' likely reflects preferential uptake of 13 C-enriched microbial biomass and underlines the importance of microorganisms, in contrast to dead plant material, as a major food resource for the soil animal community. Soil organic matter is enriched in 15 N and 13 C relative to leaf litter. Decomposers inhabiting mineral soil layers therefore might be enriched in 15 N resulting in overlap in isotope ratios between soil-dwelling detritivores and litter-dwelling predators. By contrast, 13 C content varies little between detritivores in upper litter and in mineral soil, suggesting that they rely on similar basal resources, i.e. little decomposed organic matter. Comparing vertical isotope gradients in animals and in basal resources can be a valuable tool to assess trophic interactions and dynamics of organic matter in soil. As indicated by stable isotope composition, direct feeding on living plant material as well as on mycorrhizal fungi is likely rare among soil invertebrates. Plant carbon is taken up predominantly by saprotrophic microorganisms and channelled to higher trophic levels of the soil food web. However, feeding on photoautotrophic microorganisms and non

Litter quality impacts short- but not long-term soil carbon dynamics in soil aggregate fractions.

Science.gov (United States)

Gentile, Roberta; Vanlauwe, Bernard; Six, Johan

2011-04-01

Complex molecules are presumed to be preferentially stabilized as soil organic carbon (SOC) based on the generally accepted concept that the chemical composition of litter is a major factor in its rate of decomposition. Hence, a direct link between litter quality and SOC quantity has been assumed, accepted, and ultimately incorporated in SOC models. Here, however, we present data from an incubation and field experiment that refutes the influence of litter quality on the quantity of stabilized SOC. Three different qualities of litter (Tithonia diversifolia, Calliandra calothyrsus, and Zea mays stover; 4 Mg C x ha(-1) yr(-1)) with and without the addition of mineral N fertilizer (0 or 120 kg N x ha(-1)season(-1) were added to a red clay Humic Nitisol in a 3-yr field trial and a 1.5-yr incubation experiment. The litters differed in their concentrations of N, lignin, and polyphenols with the ratio of (lignin + polyphenols): N ranging from 3.5 to 9.8 for the field trial and from 2.3 to 4.0 for the incubation experiment in the order of T. diversifolia stabilized after three annual additions in the field trial. Even within the most sensitive soil aggregate fractions, SOC contents and C:N ratios did not differ with litter quality, indicating that litter quality did not influence the mechanisms by which SOC was stabilized. While increasing litter quality displayed faster decomposition and incorporation of C into soil aggregates after 0.25 yr in the incubation study, all litters resulted in equivalent amounts of C stabilized in the soil after 1.5 yr, further corroborating the results of the field trial. The addition of N fertilizer did not affect SOC stabilization in either the field or the incubation trial. Thus, we conclude that, while litter quality controls shorter-term dynamics of C decomposition and accumulation in the soil, longer-term SOC patterns cannot be predicted based on initial litter quality effects. Hence, the formation and stabilization of SOC is more

Carbon sequestration potential of soils in southeast Germany derived from stable soil organic carbon saturation.

Science.gov (United States)

Wiesmeier, Martin; Hübner, Rico; Spörlein, Peter; Geuß, Uwe; Hangen, Edzard; Reischl, Arthur; Schilling, Bernd; von Lützow, Margit; Kögel-Knabner, Ingrid

2014-02-01

Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global CO2 mitigation. However, the potential of soils to sequester soil organic carbon (SOC) in a stable form, which is limited by the stabilization of SOC against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential SOC saturation of silt and clay particles according to Hassink [Plant and Soil 191 (1997) 77] on the basis of 516 soil profiles. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long-term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse-textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395 Mt CO2 -equivalents could theoretically be stored in A horizons of cultivated soils - four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to CO2 mitigation. Moreover, increasing SOC stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity. © 2013 John Wiley & Sons Ltd.

Structure and organic matter under different soil management conditions in the center of Argentina

International Nuclear Information System (INIS)

Bricchi, E.

2004-01-01

In Central Argentina, Cordoba Province, as in different parts of the world, the equilibrium state of soil under natural condition has been modified by both the replacement of natural vegetation and by tillage. With time, these two disturbing factors have led to a new soil state whose main characteristic is an important decrease of chemical, physical and biological soil functions. The degree of these changes is directly related to soil resistance according to soil genesis. The soil organic matter and the structure of the superficial profile of soil are suitable indicators mainly for physical functions. Recently, it became necessary to look for a combination of technologies leading to an energy input throughout conservation tillage systems, soil covering and agro-chemicals which tend to improve soil quality in order to obtain a sustainable production. The removal of natural vegetation and tillage systems have caused the following effects on the first centimetres of soils: A 77 to 80% loss of organic matter during a period of about 80 years. Changes in the water stable aggregates distribution. A 77% loss of large aggregates and a 55% gain of fine aggregates. Our results would indicate that the disturbance level was higher to the natural resistance of soil. The organic carbon content in the first centimetres of soil is increased when all crop stubble remains on the field and conservationist tillage is applied. Conservation tillages are more efficient in the lower position of relief, meaning the beginning of a change of organic matter tendency that would possibly tend to new equilibrium state. On the other hand, the percentage of water stable aggregates would also be increased as consequence of a higher organic carbon content

Soil aggregates, organic matter turnover and carbon balance in a Mediterranean eroded vineyard

Science.gov (United States)

Novara, Agata; Lo Papa, Giuseppe; Dazzi, Carmelo; Gristina, Luciano; Cerdà, Artemi

2014-05-01

The carbon cycle is being affected by the human impacts (Novara et al., 2011; Yan-Gui et al., 2013), and one of those is the intensification in the soil erosion in agriculture land (Cerdà et al., 2009; García Orenes et al., 2009). Vineyards also are affected by the human activities (Fernández Calviño, 2012). Vineyards in Sicily are cultivated on 110.000 ha, 10% of which on >10% slope. Deficiencies of soil organic matter are typical of the semi arid Mediterranean environment especially where traditional intensive cropping practices are adopted (Novara et al., 2012; 2013). These practices in vineyards could lead soil to intensive erosion processes (Novara et al., 2011). The fate of SOC under erosion processes is difficult to understand because of the influence of the erosion impact on SOC pathway, which depends on the different features of the process involved (detachment, transport and/or deposition). Soil erosion must be considered a net C source (Lal, 2003), as eroded soils have lower net primary productivity (NPP) (Dick and Gregorich, 2004) caused by reduction in the effective rooting depth and all in all determining decline in soil quality. Breakdown of aggregates and soil dispersion expose SOM to microbial/enzymatic processes and chemical soil properties (Dimoyiannis, 2012; Kocyigit and Demirci, 2012). Moreover the light fraction, transported by runoff, is labile and easily mineralized determining CO2 emission in the atmosphere (Jacinthe and Lal, 2004). Therefore, the carbon pool is lower in eroded than in un-eroded soil scapes and the rate of mineralization of soil organic matter is higher in sediments than in original soil. In this survey we show a research conducted on a slope sequence of three soil profiles in an irrigated vineyard located in Sambuca di Sicilia, Italy (UTM33-WGS84: 4169367N; 325011E). The SOC content was measured at depth intervals of 10 cm up to a depth of 60 cm in each pedon. Wet aggregate-size fractions with no prior chemical

[Relationship between Fe, Al oxides and stable organic carbon, nitrogen in the yellow-brown soils].

Science.gov (United States)

Heng, Li-Sha; Wang, Dai-Zhang; Jiang, Xin; Rao, Wei; Zhang, Wen-Hao; Guo, Chun-Yan; Li, Teng

2010-11-01

The stable organic carbon and nitrogen of the different particles were gained by oxidation of 6% NaOCl in the yellow-brown soils. The relationships between the contents of selective extractable Fe/Al and the stable organic carbon/nitrogen were investigated. It shown that amounts of dithionite-citrate-(Fe(d)) and oxalate-(Fe(o)) and pyrophosphate extractable (Fe(p)) were 6-60.8 g x kg(-1) and 0.13-4.8 g x kg(-1) and 0.03-0.47 g x kg(-1) in 2-250 microm particles, respectively; 43.1-170 g x kg(-1) and 5.9-14.0 g x kg(-1) and 0.28-0.78 g x kg(-1) in soils than in arid yellow-brown soils, and that of selective extractable Al are lower in the former than in the latter. Amounts of the stable organic carbon and nitrogen, higher in paddy yellow-brown soils than in arid yellow-brown soils, were 0.93-6.0 g x kg(-1) and 0.05-0.36 g x kg(-1) in 2-250 microm particles, respectively; 6.05-19.3 g x kg(-1) and 0.61-2.1 g x kg(-1) in stabilization index (SI(C) and SI(N)) of the organic carbon and nitrogen were 14.3-50.0 and 11.9-55.6 in 2-250 microm particles, respectively; 53.72-88.80 and 40.64-70.0 in soils than in paddy yellow-brown soils. The organic carbon and nitrogen are advantageously conserved in paddy yellow-brown soil. An extremely significant positive correlation of the stable organic carbon and nitrogen with selective extractable Fe/Al is observed. The most amounts between the stable organic carbon and nitrogen and selective extractable Fe/Al appear in clay particles, namely the clay particles could protect the soil organic carbon and nitrogen.

CFG-7-P3 : potential of aggregate-associated biodegradation of high-molecular-weight hydrocarbon fractions in crude-oil contaminated soils from a northern Canadian site

Energy Technology Data Exchange (ETDEWEB)

Chang, W.; Snelgrove, J.; Akbari, A.; Ghoshal, S. [McGill Univ., Montreal, PQ (Canada). Dept. of Civil Engineering and Applied Mechanics

2010-07-01

Soil aggregation can limit aerobic hydrocarbon biodegradation rates due to the slower intra-pore diffusion of nutrients, oxygen and hydrocarbons. This study investigated the influence of soil aggregation at a pilot-scale biopile of crude oil-contaminated soil shipped from a site in the Northwest Territories. Attempts were made to stimulate indigenous microbial activity of the hydrocarbon-degrading bacteria through soil aeration and nutrient amendments in a tank maintained at 15 degrees C. Results showed that nutrient amendment significantly enhanced aggregation. After 60 days, approximately 50 per cent of the initial total hydrocarbon productivity (TPH) was reduced in both the treated and untreated biopile. However, a TPH analysis of soil aggregate levels showed that the biodegradation of high weight hydrocarbon fractions in macroaggregates was more significantly reduced in the nutrient-amended soils. Results suggested that the soil particles in the macroaggregates were more loosely clustered, and may have supported enhanced hydrocarbon biodegradation.

Effect of aggregate size and superficial horizon differentiation on the friability index of soils cultivated with sugar cane: a multivariate approach

Directory of Open Access Journals (Sweden)

Edgar Alvaro Avila P.

2015-04-01

Full Text Available Soil friability is a physical property that provides valuable information for minimizing energy consumption during soil tillage and for preparing the edaphic medium for plant development. Its quantitative determination is generally carried out with aggregates obtained from soil blocks taken at fixed depths of profiles without considering the superficial horizons of the soil. The objective of the this study was to determine the effect of aggregate size and superficial horizon differentiation on the friability index (FI of some soils cultivated with sugar cane in the Geographic Valley of the Cauca River (Colombia, using univariate (CVu and multivariate (CVm coefficients of variation. The FI was evaluated using a compression test with four aggregate-size ranges taken from the Ap and A1 superficial horizons of 182 sampling sites located on 18 sugar cane farms. Of the five types of studied soils (Inceptisols, Mollisols, Vertisols, Alfisols and Ultisols, 7,280 aggregates were collected that were air dried and subsequently dried in a low-temperature oven before determining the tensile strength (TS, which was in turn used to calculate the FI using the coefficient of variation method. This study found that the FI varied with the aggregate size and the soil depth (first two horizons. Only three of the four size ranges initially selected were relevant. The CVm proved to be very useful for the selection of a more relevant value from the confidence interval of the TS from the CVu method for friability and established that the lower limit value (FIi of the TS CVu was the FI value that was closest to the multivariate measurement.

Effects of earthworms on soil aggregate stability and carbon and nitrogen storage in a legume cover crop agroecosystem.

NARCIS (Netherlands)

Ketterings, Q.M.; Blair, J.M.; Marinissen, J.C.Y.

1997-01-01

We investigated the effects of earthworms on soil aggregate size-distribution, water-stability, and the distribution of total C and N among aggregates of different sizes. Earthworm populations were experimentally manipulated (reduced, unaltered or increased) in field enclosures cropped to soybean

Magnetic engineering of stable rod-shaped stem cell aggregates: circumventing the pitfall of self-bending.

Science.gov (United States)

Du, V; Fayol, D; Reffay, M; Luciani, N; Bacri, J-C; Gay, C; Wilhelm, C

2015-02-01

A current challenge for tissue engineering while restoring the function of diseased or damaged tissue is to customize the tissue according to the target area. Scaffold-free approaches usually yield spheroid shapes with the risk of necrosis at the center due to poor nutrient and oxygen diffusion. Here, we used magnetic forces developed at the cellular scale by miniaturized magnets to create rod-shaped aggregates of stem cells that subsequently matured into a tissue-like structure. However, during the maturation process, the tissue-rods spontaneously bent and coiled into sphere-like structures, triggered by the increasing cell-cell adhesion within the initially non-homogeneous tissue. Optimisation of the intra-tissular magnetic forces successfully hindered the transition, in order to produce stable rod-shaped stem cells aggregates.

Changes in carbon stability and microbial activity in size fractions of micro-aggregates in a rice soil chronosequence under long term rice cultivation

Science.gov (United States)

Pan, Genxing; Liu, Yalong; Wang, Ping; Li, Lianqinfg; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Bian, Rongjun; Ding, Yuanjun; Ma, Chong

2016-04-01

Recent studies have shown soil carbon sequestration through physical protection of relative labile carbon intra micro-aggregates with formation of large sized macro-aggregates under good management of soil and agricultural systems. While carbon stabilization had been increasingly concerned as ecosystem properties, the mechanisms underspin bioactivity of soil carbon with increased carbon stability has been still poorly understood. In this study, topsoil samples were collected from rice soils derived from salt marsh under different length of rice cultivation up to 700 years from eastern China. Particle size fractions (PSF) of soil aggregates were separated using a low energy dispersion protocol. Carbon fractions in the PSFs were analyzed either with FTIR spectroscopy. Soil microbial community of bacterial, fungal and archaeal were analyzed with molecular fingerprinting using specific gene primers. Soil respiration and carbon gain from amended maize as well as enzyme activities were measured using lab incubation protocols. While the PSFs were dominated by the fine sand (200-20μm) and silt fraction (20-2μm), the mass proportion both of sand (2000-200μm) and clay (soil aggregates (also referred to aggregate stability). Soil organic carbon was found most enriched in coarse sand fraction (40-60g/kg), followed by the clay fraction (20-24.5g/kg), but depleted in the silt fraction (~10g/kg). Phenolic and aromatic carbon as recalcitrant pool were high (33-40% of total SOC) in both coarse sand and clay fractions than in both fine sand and silt fractions (20-29% of total SOC). However, the ratio of LOC/total SOC showed a weak decreasing trend with decreasing size of the aggregate fractions. Total gene content in the size fractions followed a similar trend to that of SOC. Bacterial and archaeal gene abundance was concentrated in both sand and clay fractions but that of fungi in sand fraction, and sharply decreased with the decreasing size of aggregate fraction. Gene abundance

Tillage System and Cover Crop Effects on Soil Quality

DEFF Research Database (Denmark)

Abdollahi, Lotfollah; Munkholm, Lars Juhl

2014-01-01

), and moldboard plowing (MP) with and without a cover crop were evaluated in a long-term experiment on a sandy loam soil in Denmark. Chemical, physical, and biological soil properties were measured in the spring of 2012. The field measurements included mean weight diameter (MWD) after the drop-shatter test......, penetration resistance, and visual evaluation of soil structure (VESS). In the laboratory, aggregate strength, water-stable aggregates (WSA), and clay dispersibility were measured. The analyzed chemical and biological properties included soil organic C (SOC), total N, microbial biomass C, labile P and K......Optimal use of management systems including tillage and winter cover crops is recommended to improve soil quality and sustain agricultural production. The effects on soil properties of three tillage systems (as main plot) including direct drilling (D), harrowing to a depth of 8 to 10 cm (H...

Influence of Scots pine encroachment into alpine grassland in the quality and stability of soil organic matter aggregation

Science.gov (United States)

Ortiz, Carlos; Díaz-Pinés, Eugenio; Benito, Marta; José Fernández, María; Rubio, Agustín

2013-04-01

Ecotone areas are dynamic zones potentially suitable for detecting ecosystem sensitivity to climate change effects. Climate change scenarios proposed by IPCC predict a temperature increase in Mediterranean areas with the consequent altitudinal advance of Scots pine treeline (Pinus sylvestris L.) at the extent of grassland-shrubland areas. Therefore, variations in physical, chemical and biological properties of soils due to plant dynamics are expected. We present a study located in the grassland-forest ecotone of Scots pine on a Mediterranean mountain in Central Spain, considering three different vegetation types: high mountain grassland-shrubland, shrubland-Scots pine high mountain forest and Scots pine mountain forest. We worked on the hypothesis that different plant species compositions influence both the size distribution and aggregate protection of the organic carbon (C), as a result of the different quality of C inputs to the soil from different vegetation types. To test this assumption, topsoil samples were firstly separated into four aggregate fractions (6-2 mm, 2-0.250 mm, 0.250-0.053 mm and centrifuging and decanting the supernatants; and thirdly, different iPOM (coarse iPOM and fine iPOM) and mineral associated soil organic C were released from each remaining aggregate fraction by sonication at 300 J ml-1 and further quantified by wet sieving. We expect differences between light fraction, different iPOM and mineral associated soil organic C from the different aggregates fractions obtained among vegetation types as a result of different quality and quantity organic matter inputs to the soil. Thus, we will be able to predict (i) the evolution of protected soil organic matter with the encroachment of Scots pine on Mediterranean mountains due to climate change effects, (ii) the rate of macroaggregate formation and degradation in those vegetation areas, and (iii) whether they will behave as source or sink of atmospheric C.

FATTY ACID STABLE ISOTOPE INDICATORS OF MICROBIAL CARBON SOURCE IN TROPICAL SOILS

Science.gov (United States)

The soil microbial community plays an important role in tropical ecosystem functioning because of its importance in the soil organic matter (SOM) cycle. We have measured the stable carbon isotopic ratio (delta13C) of individual phospholipid fatty acids (PLFAs) in a variety of tr...

Factors influencing soil aggregation and particulate organic matter responses to bioenergy crops across a topographic gradient

Science.gov (United States)

Todd A. Ontl; Cynthia A. Cambardella; Lisa A. Schulte; Randall K. Kolka

2015-01-01

Bioenergy crops have the potential to enhance soil carbon (C) pools from increased aggregation and the physical protection of organic matter; however, our understanding of the variation in these processes over heterogeneous landscapes is limited. In particular, little is known about the relative importance of soil properties and root characteristics for the physical...

[Soil infiltration capacity under different vegetations in southern Ningxia Loess hilly region].

Science.gov (United States)

Yang, Yong-Hui; Zhao, Shi-Wei; Lei, Ting-Wu; Liu, Han

2008-05-01

A new apparatus for measuring the run off-on-out under simulated rainfall conditions was used to study the soil infiltration capacity under different rainfall intensities and vegetations in loess hilly region of southern Ningxia, with the relationships between soil water-stable aggregate content and soil stable infiltration rate under different vegetations analyzed. The results showed that the regression equations between rainfall duration and soil infiltration rate under different vegetations all followed y = a + be(-cx), with R2 ranged from 0.9678 to 0.9969. With the increase of rainfall intensity, the soil stable infiltration rate on slope cropland decreased, while that on Medicago lupulina land, natural grassland, and Caragana korshinskii land increased. Under the rainfall intensity of 20 mm h(-1), the rainfall infiltration translation rate (RITR) was decreased in the order of M. lupulina land > slope cropland > natural grassland > C. korshinskii land; while under the rainfall intensity of 40 mm h(-1) and 56 mm h(-1), the RITR was in the sequence of M. lupulina land > natural grassland > slope cropland > C. korshinskii land, and decreased with increasing rainfall intensity. After the reversion of cropland to grassland and forest land, and with the increase of re-vegetation, the amount of >0.25 mm soil aggregates increased, and soil infiltration capacity improved. The revegetation in study area effectively improved soil structure and soil infiltration capacity, and enhanced the utilization potential of rainfall on slope.

Dynamic equilibrium of radiocesium with stable cesium within the soil-mushroom system in Turkish pine forest

International Nuclear Information System (INIS)

Karadeniz, Ozlem; Yaprak, Guenseli

2007-01-01

Mushrooms and soils collected from pine forests in Izmir, Turkey were measured for radiocesium and stable Cs in 2002. The ranges of 137 Cs and stable Cs concentrations in mushrooms were 9.84 ± 1.67 to 401 ± 3.85 Bq kg -1 dry weight and 0.040 ± 0.004 to 11.3 ± 1.09 mg kg -1 dry weight, respectively. The concentrations of 137 Cs and stable Cs in soils were 0.29 ± 0.18 to 161 ± 1.12 Bq kg -1 dry weight and 0.14 ± 0.004 to 1.44 ± 0.045 mg kg -1 dry weight, respectively. Even though different species were included, the concentration ratios of 137 Cs to stable Cs were fairly constant for samples collected at the same forest site, and were in the same order of magnitude as the 137 Cs to stable Cs ratios for the organic soil layers. The soil-to-mushroom transfer factors of 137 Cs and stable Cs were in the range of 0.19-3.15 and 0.17-12.3, respectively. The transfer factors of 137 Cs were significantly correlated to those of stable Cs. - The 137 Cs/ 133 Cs ratios observed in mushroom samples and in organic layers shows that 137 Cs is well mixed with stable Cs within the biological cycle in the studied pine forest

The influence of mass transfer on solute transport in column experiments with an aggregated soil

Science.gov (United States)

Roberts, Paul V.; Goltz, Mark N.; Summers, R. Scott; Crittenden, John C.; Nkedi-Kizza, Peter

1987-06-01

The spreading of concentration fronts in dynamic column experiments conducted with a porous, aggregated soil is analyzed by means of a previously documented transport model (DFPSDM) that accounts for longitudinal dispersion, external mass transfer in the boundary layer surrounding the aggregate particles, and diffusion in the intra-aggregate pores. The data are drawn from a previous report on the transport of tritiated water, chloride, and calcium ion in a column filled with Ione soil having an average aggregate particle diameter of 0.34 cm, at pore water velocities from 3 to 143 cm/h. The parameters for dispersion, external mass transfer, and internal diffusion were predicted for the experimental conditions by means of generalized correlations, independent of the column data. The predicted degree of solute front-spreading agreed well with the experimental observations. Consistent with the aggregate porosity of 45%, the tortuosity factor for internal pore diffusion was approximately equal to 2. Quantitative criteria for the spreading influence of the three mechanisms are evaluated with respect to the column data. Hydrodynamic dispersion is thought to have governed the front shape in the experiments at low velocity, and internal pore diffusion is believed to have dominated at high velocity; the external mass transfer resistance played a minor role under all conditions. A transport model such as DFPSDM is useful for interpreting column data with regard to the mechanisms controlling concentration front dynamics, but care must be exercised to avoid confounding the effects of the relevant processes.

Arbuscular mycorrhizal fungal communities and soil aggregation as affected by cultivation of various crops during the sugarcane fallow period

Directory of Open Access Journals (Sweden)

Priscila Viviane Truber

2014-04-01

Full Text Available Management systems involving crop rotation, ground cover species and reduced soil tillage can improve the soil physical and biological properties and reduce degradation. The primary purpose of this study was to assess the effect of various crops grown during the sugarcane fallow period on the production of glomalin and arbuscular mycorrhizal fungi in two Latosols, as well as their influence on soil aggregation. The experiment was conducted on an eutroferric Red Latosol with high-clay texture (680 g clay kg-1 and an acric Red Latosol with clayey texture (440 g kg-1 clay in Jaboticabal (São Paulo State, Brazil. A randomized block design involving five blocks and four crops [soybean (S, soybean/fallow/soybean (SFS, soybean/millet/soybean (SMS and soybean/sunn hemp/soybean (SHS] was used to this end. Soil samples for analysis were collected in June 2011. No significant differences in total glomalin production were detected between the soils after the different crops. However, total external mycelium length was greater in the soils under SMS and SHS. Also, there were differences in easily extractable glomalin, total glomalin and aggregate stability, which were all greater in the eutroferric Red Latosol than in the acric Red Latosol. None of the cover crops planted in the fallow period of sugarcane improved aggregate stability in either Latosol.

[Effect of mineral N fertilizer reduction and organic fertilizer substitution on soil biological properties and aggregate characteristics in drip-irrigated cotton field.

Science.gov (United States)

Li, Rui; Tai, Rui; Wang, Dan; Chu, Gui-Xin

2017-10-01

A four year field study was conducted to determine how soil biological properties and soil aggregate stability changed when organic fertilizer and biofertilizer were used to reduce chemical fertilizer application to a drip irrigated cotton field. The study consisted of six fertilization treatments: unfertilized (CK); chemical fertilizer (CF, 300 kg N·hm -2 ; 90 kg P2O5 · hm -2 , 60 kg K2 O·hm -2 ); 80% CF plus 3000 kg·hm -2 organic fertilizer (80%CF+OF); 60% CF plus 6000 kg·hm -2 organic fertilizer (60%CF+OF); 80% CF plus 3000 kg·hm -2 biofertilizer (80%CF+BF); and 60% CF plus 6000 kg·hm -2 biofertilizer (60%CF+BF). The relationships among soil organic C, soil biological properties, and soil aggregate size distribution were determined. The results showed that organic fertilizer and biofertilizer both significantly increased soil enzyme activities. Compared with CF, the biofertilizer treatments increased urease activity by 55.6%-84.0%, alkaline phosphatise activity by 53.1%-74.0%, invertase activity by 15.1%-38.0%, β-glucosidase activity by 38.2%-68.0%, polyphenoloxidase activity by 29.6%-52.0%, and arylsulfatase activity by 35.4%-58.9%. Soil enzyme activity increased as the amount of organic fertilizer and biofertilizer increased (i.e., 60%CF+OF > 80%CF+OF, 60%CF+BF > 80%CF+BF). Soil basal respiration decreased significantly in the order BF > OF > CF > CK. Soil microbial biomass C and N were 22.3% and 43.5% greater, respectively, in 60%CF+BF than in CF. The microbial biomass C:N was significantly lower in 60%CF+BF than in CF. The organic fertilizer and the biofertilizer both improved soil aggregate structure. Soil mass in the >0.25 mm fraction was 7.1% greater in 80%CF+OF and 8.0% greater in (60%CF+OF) than in CF. The geometric mean diameter was 9.2% greater in 80%CF+BF than in 80%CF+OF. Redundancy analysis and cluster analysis both demonstrated that soil aggregate structure and biological activities increased when organic fertilizer and biofertilizer were

INTERACTION’S EFFECT OF ORGANIC MATERIAL AND AGGREGATION ON EXTRACTION EFFICIENCY OF TPHS FROM PETROLEUM CONTAMINATED SOILS WITH MAE

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H. Ganjidoust and Gh. Naghizadeh

2005-10-01

Full Text Available Microwave-Assisted Extraction (MAE is a type of low-temperature thermal desorption process that its numerous advantages have caused a wide spread use of it. Microwave heating is a potentially attractive technique as it provides volumetric heating process to improve heating efficiencies as compared with conventional techniques. The ability to rapidly heat the sample solvent mixture is inherent to MAE and the main advantage of this technique. Presently MAE has been shown to be one of the best technologies for removing environmental pollutants specially PAHs, phenols and PCBs from soils and sediments. Five different mixtures and types of aggregation (Sand, Top soil, Kaolinite besides three concentrations of crude oil as a contaminant (1000, 5000 and 10000 mg/L were considered. The results indicated that regardless of aggregation, the presence of humus component in soil reduces the efficiency. Minimum and maximum efficiencies were for sandy soil (containing organic components and kaolinite (without any organic content, respectively. According to the results of this research when some amount of humus and organic materials are available in the matrix, it causes the extraction efficiency to perform as a function of just humus materials but not aggregation. Increasing the concentration of crude oil reduced the efficiency with a sharp steep for higher concentration (5000-10000 mg/L and less steeper for lower concentration (1000-5000 mg/L. The concentration of the contaminant, works just as an independent function with extraction time and aggregation factors. The extraction period of 10 min. can be suggested as an optimum extraction time in FMAE for PAHs contaminated soils.

Fingerprints of four crop models as affected by soil input data aggregation

Czech Academy of Sciences Publication Activity Database

Angulo, C.; Gaiser, T.; Rötter, R. P.; Børgesen, C. D.; Hlavinka, Petr; Trnka, Miroslav; Ewert, F.

2014-01-01

Roč. 61, NOV 2014 (2014), s. 35-48 ISSN 1161-0301 R&D Projects: GA MŠk(CZ) EE2.3.20.0248; GA MŠk(CZ) EE2.4.31.0056; GA MZe QJ1310123 Institutional support: RVO:67179843 Keywords : crop model * soil data * spatial resolution * yield distribution * aggregation Subject RIV: EH - Ecology, Behaviour Impact factor: 2.704, year: 2014

[Effects of land use and environmental factors on the variability of soil quality indicators in hilly Loess Plateau region of China].

Science.gov (United States)

Xu, Ming-Xiang; Liu, Guo-Bin; Zhao, Yun-Ge

2011-02-01

Classical statistics methods were adopted to analyze the soil quality variability, its affecting factors, and affecting degree at a regional scale (700 km2) in the central part of hilly Loess Plateau region of China. There existed great differences in the variability of test soil quality indicators. Soil pH, structural coefficient, silt content, specific gravity, bulk density, total porosity, capillary porosity, and catalase activity were the indicators with weak variability; soil nutrients (N, P, and K) contents, CaCO3 content, cation exchange capacity (CEC), clay content, micro-aggregate mean mass diameter, aggregate mean mass diameter, water-stable aggregates, respiration rate, microbial quotient, invertase and phosphatase activities, respiratory quotient, and microbial carbon and nitrogen showed medium variation; while soil labile organic carbon and phosphorus contents, erosion-resistance, permeability coefficient, and urease activity were the indicators with strong variability. The variability of soil CaCO3, total P and K, CEC, texture, and specific gravity, etc. was correlated with topography and other environmental factors, while the variability of dynamic soil quality indicators, including soil organic matter content, nitrogen content, water-stable aggregates, permeability, microbial biomass carbon and nitrogen, enzyme activities, and respiration rate, was mainly correlated with land use type. Overall, land use pattern explained 97% of the variability of soil quality indicators in the region. It was suggested that in the evaluation of soil quality in hilly Loess Plateau region, land use type and environmental factors should be fully considered.

Measurement of particle size distribution of soil and selected aggregate sizes using the hydrometer method and laser diffractometry

Science.gov (United States)

Guzmán, G.; Gómez, J. A.; Giráldez, J. V.

2010-05-01

Soil particle size distribution has been traditionally determined by the hydrometer or the sieve-pipette methods, both of them time consuming and requiring a relatively large soil sample. This might be a limitation in situations, such as for instance analysis of suspended sediment, when the sample is small. A possible alternative to these methods are the optical techniques such as laser diffractometry. However the literature indicates that the use of this technique as an alternative to traditional methods is still limited, because the difficulty in replicating the results obtained with the standard methods. In this study we present the percentages of soil grain size determined using laser diffractometry within ranges set between 0.04 - 2000 μm. A Beckman-Coulter ® LS-230 with a 750 nm laser beam and software version 3.2 in five soils, representative of southern Spain: Alameda, Benacazón, Conchuela, Lanjarón and Pedrera. In three of the studied soils (Alameda, Benacazón and Conchuela) the particle size distribution of each aggregate size class was also determined. Aggregate size classes were obtained by dry sieve analysis using a Retsch AS 200 basic ®. Two hundred grams of air dried soil were sieved during 150 s, at amplitude 2 mm, getting nine different sizes between 2000 μm and 10 μm. Analyses were performed by triplicate. The soil sample preparation was also adapted to our conditions. A small amount each soil sample (less than 1 g) was transferred to the fluid module full of running water and disaggregated by ultrasonication at energy level 4 and 80 ml of sodium hexametaphosphate solution during 580 seconds. Two replicates of each sample were performed. Each measurement was made for a 90 second reading at a pump speed of 62. After the laser diffractometry analysis, each soil and its aggregate classes were processed calibrating its own optical model fitting the optical parameters that mainly depends on the color and the shape of the analyzed particle. As a

The Effect of Zeolite on Aggregate Stability Indices

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F. Sohrab

2016-02-01

Full Text Available Introduction: Soil structural stability affects the profitability and sustainability of agricultural systems. Particle size distribution (PSD and aggregate stability are the important characteristics of soil. Aggregate stability has a significant impact on the development of the root system, water and carbon cycle and soil resistance against soil erosion. Soil aggregate stability, defined as the ability of the aggregates to remain intact when subject to a given stress, is an important soil property that affects the movement and storage of water, aeration, erosion, biological activity and growth of crops. Dry soil aggregate stability (Mean Weight Diameter (MWD, Geometric Mean Diameter (GMD and Wet Aggregate Stability (WAS are important indices for evaluating soil aggregate stability.To improve soil physical properties, including modifying aggregate, using various additives (organic, inorganic and chemicals, zeolites are among what has been studied.According to traditional definition, zeolites are hydratealuminosilicates of alkaline and alkaline-earth minerals. Their structure is made up of a framework of[SiO4]−4 and [AlO4]−5 tetrahedron linked to each other's cornersby sharing oxygen atoms. The substitution of Si+4 by Al+3 intetrahedral sites results inmore negative charges and a high cation exchange capacity.Zeolites, as natural cation exchangers, are suitable substitutes to remove toxic cations. Among the natural zeolites,Clinoptilolite seems to be the most efficient ion exchanger and ion-selective material forremoving and stabilizing heavy metals.Due to theexisting insufficient technical information on the effects of using different levels of zeolite on physical properties of different types of soils in Iran, the aim of this research was to assess the effects of two different types of zeolite (Clinoptilolite natural zeolite, Z4, and Synthetic zeolite, A4 on aggregate stability indicesof soil. Materials and Methods: In this study at first

Extraction of pores from microtomographic reconstructions of intact soil aggregates

Energy Technology Data Exchange (ETDEWEB)

Albee, P. B.; Stockman, G. C.; Smucker, A. J. M.

2000-02-29

Segmentation of features is often a necessary step in the analysis of volumetric data. The authors have developed a simple technique for extracting voids from irregular volumetric data sets. In this work they look at extracting pores from soil aggregates. First, they identify a threshold that gives good separability of the object from the background. They then segment the object, and perform connected components analysis on the pores within the object. Using their technique pores that break the surface can be segmented along with pores completely contained in the initially segmented object.

Population structure of manganese-oxidizing bacteria in stratified soils and properties of manganese oxide aggregates under manganese-complex medium enrichment.

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Weihong Yang

Full Text Available Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II-oxidizing activities at the range of 1 µM to 240 µM of the equivalent MnO2. The high Mn(II-oxidizing isolates (>50 mM MnO2 were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II-oxidizing bacterial genera (species, namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II to Mn(III/IV by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the

Contribution of arbuscular mycorrhizal fungi of sedges to soil aggregation along an altitudinal alpine grassland gradient on the Tibetan Plateau.

Science.gov (United States)

Li, Xiaoliang; Zhang, Junling; Gai, Jingping; Cai, Xiaobu; Christie, Peter; Li, Xiaolin

2015-08-01

The diversity of arbuscular mycorrhizal fungi (AMF) in sedges on the Tibetan Plateau remains largely unexplored, and their contribution to soil aggregation can be important in understanding the ecological function of AMF in alpine ecosystems. Roots of Kobresia pygmaea C.B. Clarke and Carex pseudofoetida Kük. in alpine Kobresia pastures along an elevational transect (4149-5033 m) on Mount Mila were analysed for AMF diversity. A structural equation model was built to explore the contribution of biotic factors to soil aggregation. Sedges harboured abundant AMF communities covering seven families and some operational taxonomic units are habitat specific. The two plant species hosted similar AMF communities at most altitudes. The relative abundance of the two sedges contributed largely to soil macroaggregates, followed by extraradical mycorrhizal hyphae (EMH) and total glomalin-related soil protein (T-GRSP). The influence of plant richness was mainly due to its indirect influence on T-GRSP and EMH. There was a strong positive correlation between GRSP and soil total carbon and nitrogen. Our results indicate that mycorrhization might not be a major trait leading to niche differentiation of the two co-occurring sedge species. However, AMF contribute to soil aggregation and thus may have the potential to greatly influence C and N cycling in alpine grasslands. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Linking plants, fungi and soil mechanics

Science.gov (United States)

Yildiz, Anil; Graf, Frank

2017-04-01

their plant partners, the fungi themselves need to have access to water and nutrients. For this purpose, a resilient soil matrix consisting of stable micro- and macro-aggregates is an indispensable prerequisite. Luckily, the fungi are among the pioneers in assembling stable aggregates. The fungal hyphae intensively penetrate the unstructured soil body, enmeshing small organic and inorganic soil particles and form and cement them to micro- and macro-aggregates. On the one hand, growing hyphae are able to align primary particles and, on the other hand, exert pressure on surrounding particles and compounds forcing them together, such as clay and organic matter. Under physiological (or neutral) pH values, the fungal mycelia have a net negative charge. It is suggested that negatively charged fungal polysaccharides are bound to negatively charged clay minerals by bridges of polyvalent cations which have been proven to be stronger than some direct bonds between clay and organic matter. The formation of aggregates up to a size of 2 mm is associated with hyphal length of fungi. With regard to the assemblage of aggregates >2 mm both fungal mycelia and roots are involved. Indirectly, the mycorrhizal fungi affect the aggregate establishment through their host plants, particularly by accelerating the development of their root network and by serving as a distribution vector for associated micro-organisms, mainly bacteria and archaea, additionally contributing to cementation. Therefore, root-reinforcement as addressed for quantification of vegetation effects on slope stability almost ever is a combined contribution of fungal mycelia and root networks. With soil aggregates as the "bricks" for building a stable soil matrix and pore structure, root-reinforcement strongly depends on aggregate strength controlling potential, efficiency, and sustainability of growth and development of the protective vegetation. From a geotechnical point of view, aggregation of fines may be such pronounced

Direct and indirect effects of glomalin, mycorrhizal hyphae, and roots on aggregate stability in rhizosphere of trifoliate orange.

Science.gov (United States)

Wu, Qiang-Sheng; Cao, Ming-Qin; Zou, Ying-Ning; He, Xin-hua

2014-07-25

To test direct and indirect effects of glomalin, mycorrhizal hyphae, and roots on aggregate stability, perspex pots separated by 37-μm nylon mesh in the middle were used to form root-free hyphae and root/hyphae chambers, where trifoliate orange (Poncirus trifoliata) seedlings were colonized by Funneliformis mosseae or Paraglomus occultum in the root/hyphae chamber. Both fungal species induced significantly higher plant growth, root total length, easily-extractable glomalin-related soil protein (EE-GRSP) and total GRSP (T-GRSP), and mean weight diameter (an aggregate stability indicator). The Pearson correlation showed that root colonization or soil hyphal length significantly positively correlated with EE-GRSP, difficultly-extractable GRSP (DE-GRSP), T-GRSP, and water-stable aggregates in 2.00-4.00, 0.50-1.00, and 0.25-0.50 mm size fractions. The path analysis indicated that in the root/hyphae chamber, aggregate stability derived from a direct effect of root colonization, EE-GRSP or DE-GRSP. Meanwhile, the direct effect was stronger by EE-GRSP or DE-GRSP than by mycorrhizal colonization. In the root-free hyphae chamber, mycorrhizal-mediated aggregate stability was due to total effect but not direct effect of soil hyphal length, EE-GRSP and T-GRSP. Our results suggest that GRSP among these tested factors may be the primary contributor to aggregate stability in the citrus rhizosphere.

Using fourier-transform mid-infrared spectroscopy to distinguish soil organic matter composition dynamics in aggregate fractions of two agroecosystems

Science.gov (United States)

The relationship between soil organic carbon (SOC) content and quality of SOC as impacted by land management is not well understood and may influence long-term storage of SOC. To better understand the potential for SOC storage in specific aggregate pools (i.e. physically protected intra-aggregate C)...

Plant litter chemistry alters the content and composition of organic carbon associated with soil mineral and aggregate fractions in invaded ecosystems.

Science.gov (United States)

Tamura, Mioko; Suseela, Vidya; Simpson, Myrna; Powell, Brian; Tharayil, Nishanth

2017-10-01

Through the input of disproportionate quantities of chemically distinct litter, invasive plants may potentially influence the fate of organic matter associated with soil mineral and aggregate fractions in some of the ecosystems they invade. Although context dependent, these native ecosystems subjected to prolonged invasion by exotic plants may be instrumental in distinguishing the role of plant-microbe-mineral interactions from the broader edaphic and climatic influences on the formation of soil organic matter (SOM). We hypothesized that the soils subjected to prolonged invasion by an exotic plant that input recalcitrant litter (Japanese knotweed, Polygonum cuspidatum) would have a greater proportion of plant-derived carbon (C) in the aggregate fractions, as compared with that in adjacent soil inhabited by native vegetation that input labile litter, whereas the soils under an invader that input labile litter (kudzu, Pueraria lobata) would have a greater proportion of microbial-derived C in the silt-clay fraction, as compared with that in adjacent soils that receive recalcitrant litter. At the knotweed site, the higher C content in soils under P. cuspidatum, compared with noninvaded soils inhabited by grasses and forbs, was limited to the macroaggregate fraction, which was abundant in plant biomarkers. The noninvaded soils at this site had a higher abundance of lignins in mineral and microaggregate fractions and suberin in the macroaggregate fraction, partly because of the greater root density of the native species, which might have had an overriding influence on the chemistry of the above-ground litter input. At the kudzu site, soils under P. lobata had lower C content across all size fractions at a 0-5 cm soil depth despite receiving similar amounts of Pinus litter. Contrary to our prediction, the noninvaded soils receiving recalcitrant Pinus litter had a similar abundance of plant biomarkers across both mineral and aggregate fractions, potentially because of

Effects of Land Use on Concentrations and Chemical Forms of Phosphorus in Different-Size Aggregates

Science.gov (United States)

Ahmad, E. H.; Demisie, W.; Zhang, M.

2017-12-01

Land use has been recognized as an important driver of environmental change on all spatial and temporal scales. This study was conducted to determine the effects of land uses on phosphorus concentration in bulk soil and in water-stable aggregates in different soils. The study was conducted on three soil types (Ferrosols, Cambosols, and Primosols), which were collected from three different locations from southeast China and under three land uses (Uncultivated, Vegetable and forest land) the region is characterized as a hill and plain area. Accordingly, a total of 24 soil samples were collected. The results showed that average contents of total P were 0.55-1.55 g/kg, 0.28-1.03 g/kg and 0.14-0.8 g/kg for the soils: Cambosols, Ferrosols and Primosols respectively. Vegetable and forest land led to higher total phosphorus contents in these soils than in the uncultivated land. An aggregate fraction of >2 mm under forest land made up the largest percentage (30 up to 70%), whereas the size fraction phosphorus, organic phosphorus and Olsen P and phosphorus forms in the soils. It implies that the conversion of natural ecosystem to vegetable land increased the phosphorus proportion in the soils, which could have negative impact on the environmental quality.

Comparação entre métodos para o estudo da estabilidade de agregados em solos Comparison of methods for aggregate stability studies in soils

Directory of Open Access Journals (Sweden)

MARCOS AURÉLIO CAROLINO DE SÁ

2000-09-01

wet sieving and the two other methods. The DRL samples had more stable aggregates than did SDR samples. The resistance to sonication was related to amount of organic matter, Fe oxides and gibbsite. The results of weighted mean diameter and amount of aggregates larger than 2 mm were the same for the A horizons of both soils. Water dropping caused more disruption on DRL B than on SDR B-horizon material which was more affected by the wet sieving method. The level of 15.88 J mL-1 allowed to detect more differences between the soils.

Perennial grasses for recovery of the aggregation capacity of a reconstructed soil in a coal mining area in southern Brazil

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Lizete Stumpf

2014-02-01

Full Text Available The construction of a soil after surface coal mining involves heavy machinery traffic during the topographic regeneration of the area, resulting in compaction of the relocated soil layers. This leads to problems with water infiltration and redistribution along the new profile, causing water erosion and consequently hampering the revegetation of the reconstructed soil. The planting of species useful in the process of soil decompaction is a promising strategy for the recovery of the soil structural quality. This study investigated the influence of different perennial grasses on the recovery of reconstructed soil aggregation in a coal mining area of the Companhia Riograndense de Mineração, located in Candiota-RS, which were planted in September/October 2007. The treatments consisted of planting: T1- Cynodon dactylon cv vaquero; T2 - Urochloa brizantha; T3 - Panicum maximun; T4 - Urochloa humidicola; T5 - Hemarthria altissima; T6 - Cynodon dactylon cv tifton 85. Bare reconstructed soil, adjacent to the experimental area, was used as control treatment (T7 and natural soil adjacent to the mining area covered with native vegetation was used as reference area (T8. Disturbed and undisturbed soil samples were collected in October/2009 (layers 0.00-0.05 and 0.10-0.15 m to determine the percentage of macro- and microaggregates, mean weight diameter (MWD of aggregates, organic matter content, bulk density, and macro- and microporosity. The lower values of macroaggregates and MWD in the surface than in the subsurface layer of the reconstructed soil resulted from the high degree of compaction caused by the traffic of heavy machinery on the clay material. After 24 months, all experimental grass treatments showed improvements in soil aggregation compared to the bare reconstructed soil (control, mainly in the 0.00-0.05 m layer, particularly in the two Urochloa treatments (T2 and T4 and Hemarthria altissima (T5. However, the great differences between the

Stable isotopes in plant nutrition, soil fertility and environmental studies

International Nuclear Information System (INIS)

1991-01-01

The individual contributions in these proceedings are indexed separately. Main topics covered include the measurement of biological nitrogen fixation, studies of soil organic matter, investigations of nutrient uptake and use by plants, studies of plant metabolism and new methodologies in the analysis of stable isotopes. Refs, figs and tabs

Using soil organic matter fractions as indicators of soil physical quality

DEFF Research Database (Denmark)

Pulido Moncada, Mansonia A.; Lozano, Z; Delgado, M

2018-01-01

The objective of this study was to evaluate the use of chemical and physical fractions of soil organic matter (SOM), rather than SOM per se, as indicators of soil physical quality (SPQ) based on their effect on aggregate stability (AS). Chemically extracted humic and fulvic acids (HA and FA) were...... used as chemical fractions, and heavy and light fractions (HF and LF) obtained by density separation as physical fractions. The analyses were conducted on medium-textured soils from tropical and temperate regions under cropland and pasture. Results show that soil organic carbon (SOC), SOM fractions...... and AS appear to be affected by land use regardless of the origin of the soils. A general separation of structurally stable and unstable soils between samples of large and small SOC content, respectively, was observed. SOM fractions did not show a better relationship with AS than SOC per se. In both...

IMPACT OF BRACHIARIA, ARBUSCULAR MYCORRHIZA, AND POTASSIUM ENRICHED RICE STRAW COMPOST ON ALUMINIUM, POTASSIUM AND STABILITY OF ACID SOIL AGGREGATES

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Bariot Hafif

2013-04-01

Full Text Available Acid soil is commonly grown with cassava, which in general, tolerate low soil  fertility and aluminum (Al toxicity. However, without any improvement efforts such soil will become worse. Intercropping cassava with Brachiaria decumbens (BD which adapts to acid soil and tolerates low fertility soils as well as application of arbuscular mycorrhiza (AM and organic matters are among the important efforts to rehabilitate this soil. The experiment was conducted to  examine the impact of BD, AM, and potassium (K enriched rice straw compost on exchangeable Al, available K, and stability of soil aggregates. Experiment was arranged in a completely randomized design with three factors and three replications. The first factor was BD as cassava intercropping, the second factor was AM, and the third factor was 2 t ha-1 rice straw compost enriched with 0 kg, 50 kg, 100 kg, and 200 kg KCl ha-1. Brick pots (1 m length x 1 m width x 0.45 m depth filled with Kanhapludult soil was used for growing cassava in which row of BD was planted at 60 cm from cassava stem. K-enriched rice straw compost and AM (10 g per stem were applied around cassava stem at 2 and 12 days after planting, respectively. BD was cut every 30 days and the cutting was returned to the soil. Soil exchangeable Al was analyzed at 0, 3, 6 and 9 months after planting (MAP, while Al and K contents as well as aggregate stability were measured at 6 MAP. The results showed that planting BD decreased 33% exchangeable Al, which means that the root exudates of this grass was effective in detoxifying Al3+. Treatment of BD and/or in combination with AM was effective in preserving K added to the soil, increasing total polysaccharides, and improving soil aggregate stability. This indicated that planting BD and applying AM and Kenriched rice straw compost improved acid soil fertility, and therefore can be recommended in cassava cultivation.

Uptake of radionuclides and stable elements from paddy soil to rice: a review

International Nuclear Information System (INIS)

Uchida, S.; Tagami, K.; Shang, Z.R.; Choi, Y.H.

2009-01-01

The critical paths for radionuclides and the critical foods in Asian countries differ from those in Western countries because agricultural products and diets are different. Consequently, safety assessments for Asian countries must consider rice as a critical food. As most rice is produced under flooded conditions, the uptake of radionuclides by rice is affected by soil conditions. In this report, we summarize radionuclide and stable element soil-to-plant transfer factors (TFs) for rice. Field observation results for fallout 137 Cs and stable Cs TFs indicated that while fallout 137 Cs had higher TF than stable Cs over several decades, the GM (geometric mean) values were similar with the GM of TF value for 137 Cs being 3.6 x 10 -3 and that for stable Cs being 2.5 x 10 -3 . Although there are some limitations to the use of TF for stable elements under some circumstances, these values can be used to evaluate long-term transfer of long-lived radionuclides in the environment. The compiled data showed that TF values were higher in brown rice than in white rice because distribution patterns for elements were different in the bran and white parts of rice grains.

Use of morphometric soil aggregates parameters to evaluate the reclamation process in mined areas located at amazon forest - Brazil

Science.gov (United States)

Ribeiro, A. I.; Fengler, F. H.; Longo, R. M.; Mello, G. F.; Damame, D. B.; Crowley, D. E.

2015-12-01

Brazil has a high mineral potential that have been explored over the years. A large fraction of these mineral resources are located in Amazon region, which is known for its large biodiversity and world climate importance. As the policies that control the Amazon preservation are relatively new, several mining activities have been exploring the Amazon territory, promoting a large process of degradation. Once the mining activities have a high potential of environmental changes the government created polices to restrain the mining in Amazon forests and obligate mining companies to reclaim theirs minded areas. However, the measurement of reclamation development still is a challenging task for the Professionals involved. The volume and complexity of the variables, allied to the difficulty in identifying the reclamation of ecosystem functionalities are still lack to ensure the reclamation success. In this sense this work aims to investigate the representativeness of morphometric soil aggregates parameters in the understanding of reclamation development. The study area is located in the National Forest of Jamari, State of Rondônia. In the past mining companies explored the region producing eight closed mines that are now in reclamation process. The soil aggregates morphometric measurements: geometric mean diameter (GMD), aggregate circularity index, and aggregate roundness, were choose based in its obtaining facility, and their association to biological activity. To achieve the proposed objective the aggregates of eight sites in reclamation, from different closed mines, where chosen and compared to Amazon forest and open mine soil aggregates. The results were analyzed to one way ANOVA to identifying differences between areas in reclamation, natural ecosystem, and open mine. It was obtained differences for GMD and circularity index. However, only the circularity index allowed to identifying differences between the reclamation sites. The results allowed concluding: (1

Effects of experimental repeated fires in the soil aggregation and its temporal evolution

Science.gov (United States)

Campo, Julian; Gimeno, Eugenia; Andreu, Vicente; Gonzalez, Oscar; Rubio, Jose Luis

2013-04-01

Forest fires are an important problem in the Mediterranean and change our forest topsoils with still unknown consequences for important ecosystem services, such as water availability, plant growth and carbon sequestration. The total area affected by forest fires in Mediterranean countries of the European Union has declined since 1980, and the number of fires in this region tends to stabilize. However, in countries like Spain and Portugal the number of fires tends to increase. This fact seems to support future predictions indicating a general tendency to increase the number of forest fires, related to the climate change. According to European Forest Fire Information System (EFFIS), 102349 ha of the Spanish forest surface were burned in the summer of 2012 (01/06- 11/08/), of which 54186 ha were registered in the Valencia region. In this sense, to assess post-fire soil recovery aggregate stability has been used as an indicator in the Experimental Station of La Concordia (Valencia, Spain), where experimental fires were carried out in1995 and 2003, in a set of nine plots (20x4m). The soil studied is a Rendzic Leptosol. The stability of macroaggregates (SMS, Ø >250 μm), soil organic matter (SOM) and calcium carbonate contents, aggregates size and water erosion processes, were analysed in relation to fire severity and its recurrence, in two environments (under canopy, UC, and bare soils, BS), and in the short- and medium-term of two fires. In 1995, different fire treatments were applied to obtain different fire severities: three plots were burned with high severity fire, other three plots with moderate one, and the remainder plots were left unburned (control). In 2003, the same plots were burned again with low severity fires. The study was performed until summer of 2007. In general, soil environment explained significant differences in the soil properties between under canopy and bare soils. Only in the short-term of repeated fires, CaCO3 content, macroaggregate mean

Feedbacks Between Soil Structure and Microbial Activities in Soil

Science.gov (United States)

Bailey, V. L.; Smith, A. P.; Fansler, S.; Varga, T.; Kemner, K. M.; McCue, L. A.

2017-12-01

Soil structure provides the physical framework for soil microbial habitats. The connectivity and size distribution of soil pores controls the microbial access to nutrient resources for growth and metabolism. Thus, a crucial component of soil research is how a soil's three-dimensional structure and organization influences its biological potential on a multitude of spatial and temporal scales. In an effort to understand microbial processes at scale more consistent with a microbial community, we have used soil aggregates as discrete units of soil microbial habitats. Our research has shown that mean pore diameter (x-ray computed tomography) of soil aggregates varies with the aggregate diameter itself. Analyzing both the bacterial composition (16S) and enzyme activities of individual aggregates showed significant differences in the relative abundances of key members the microbial communities associated with high enzyme activities compared to those with low activities, even though we observed no differences in the size of the biomass, nor in the overall richness or diversity of these communities. We hypothesize that resources and substrates have stimulated key populations in the aggregates identified as highly active, and as such, we conducted further research that explored how such key populations (i.e. fungal or bacterial dominated populations) alter pathways of C accumulation in aggregate size domains and microbial C utilization. Fungi support and stabilize soil structure through both physical and chemical effects of their hyphal networks. In contrast, bacterial-dominated communities are purported to facilitate micro- and fine aggregate stabilization. Here we quantify the direct effects fungal versus bacterial dominated communities on aggregate formation (both the rate of aggregation and the quality, quantity and distribution of SOC contained within aggregates). A quantitative understanding of the different mechanisms through which fungi or bacteria shape aggregate

On stable ground: Tackling soil erosion with nuclear techniques in Viet Nam

International Nuclear Information System (INIS)

Gaspar, Miklos

2015-01-01

Dao Thanh Canh never studied physics or chemistry in school, but he understands a thing or two about nuclear isotopes. Until a couple of years ago, much of his five acre farm on the hills of central Viet Nam was gradually sliding away. Thanks to nuclear techniques used in determining the exact cause and source of soil erosion, his land is now stable, and his coffee plantation profitable. “We were very worried as uncertainty loomed,” he said. “A few centimetres of the soil disappeared every year when we had big hail storms.” Thanh Canh is not alone. Soil degradation affects 1.9 billion hectares of land worldwide, close to two thirds of global soil resources.

Óxidos de hierro libres asociados a carbono orgánico en agregados de suelos del partido de Balcarce Free iron oxides associated to organic carbon in soils aggregates in Balcarce county

Directory of Open Access Journals (Sweden)

Fabián Néstor Cabria

2005-07-01

of aggregates drives to seclude the organic carbon in stable macroaggregates. This concept comes from research about the way as tillage alters the rate of formation and degradation of aggregates and, consequently, the natural dynamic of particulate organic matter and organomineral associations. There is no local information that corroborate within aggregates organic carbon associated to minerals and better information on the nature and dynamics of organomineral associations will lead to a greater understanding of soil structure dynamics and of carbon cycling and sequestration in soils. These were the aims of this research and free iron oxides associated to organic compounds were chemically removed from soil aggregates in three soil series under continuous cropping with conventional tillage (CCCT and non-grazed crop-pasture (NGCP. The results showed that ferrihydrite, a low crystallinity oxide, would be part of organomineral associations. The quantity of this mineral would diminish under CCCT, but the magnitude of this result in the three soil series was different. In both management systems, the iron removed of free iron oxides associated to organic compounds was more abundant in macroaggregates than in microaggregates. Under conventional tillage, the iron diminished in macroaggregates and increased in microaggregates. We suggest that in undisturbed soils the organic carbon associated to mineral sequestration, ferrihydrite, among others, would occur within microaggregates finally confined in stable macroaggregates.

Soils, County-wide soils cover - an aggregation of section-wide soil coverages with additional attributes. Primary attributes include mu symbol and ID, state symbol, name, category, percolation rate and passing percentage., Published in 2008, 1:1200 (1in=100ft) scale, Sedgwick County Government.

Data.gov (United States)

NSGIC Local Govt | GIS Inventory — Soils dataset current as of 2008. County-wide soils cover - an aggregation of section-wide soil coverages with additional attributes. Primary attributes include mu...

Aggregation of surface mine soil by interaction between VAM fungi and lignin degradation products of lespedeza

Energy Technology Data Exchange (ETDEWEB)

Rothwell, F.M. (USDA Forest Service, Berea, KY (USA). Northeastern Forest Experiment Station, Forestry Sciences Laboratory)

1984-01-01

The external mycelium of a vesicular-arbuscular mycorrhizal (VAM) fungus was effective in aggregating a sandy loam minesoil. The polysaccharide nature of the soil binding agent on hyphal surfaces and on the surfaces of sand particles in contact with the hyphae within the aggregate was demonstrated with the periodic acid-Schiff reagent staining reaction. A possible stabilizing mechanism for macroaggregates was proposed that involves a coupling reaction between glucosamines in the hyphal walls of the fungus with phenolic compounds released during lignin degradation of sericea lespedeza root tissue. 28 refs.

An alternative method for determining particle-size distribution of forest road aggregate and soil with large-sized particles

Science.gov (United States)

Hakjun Rhee; Randy B. Foltz; James L. Fridley; Finn Krogstad; Deborah S. Page-Dumroese

2014-01-01

Measurement of particle-size distribution (PSD) of soil with large-sized particles (e.g., 25.4 mm diameter) requires a large sample and numerous particle-size analyses (PSAs). A new method is needed that would reduce time, effort, and cost for PSAs of the soil and aggregate material with large-sized particles. We evaluated a nested method for sampling and PSA by...

Effects of land use and management on aggregate stability and hydraulic conductivity of soils within River Njoro Watershed in Kenya

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Zachary G. Mainuri

2013-09-01

Full Text Available There has been tremendous changes in land use and management in the River Njoro Watershed during the last three decades. Formerly large scale farms have been converted into smallholder farms and plantation forests have gradually been lost. These changes in land use and management have brought in different approaches that have triggered soil erosion and other forms of land degradation. The objective of this study was to trace the changes in land use and determine their effects on aggregate stability and hydraulic conductivity. A semi detailed soil survey of the watershed was undertaken following a three-tier approach comprising image interpretation, field surveys and laboratory analysis. The measured variables in the soil were analysed using ANOVA and correlation analysis. The major land uses were found to be forestland, agricultural land, grassland, and wetland. A strong soil type _ landscape relationship was observed within the watershed. Soils of slopes were moderately to severely eroded, shallow and less developed whereas those on summits, pen plains, uplands, plateaus and valleys were deep and well developed. Aggregate stability was the highest in forestland and decreased in the order of grassland, agricultural land and wetland respectively. The mean weight diameter under the various land use conditions was 0.68, 0.64, 0.58, and 0 41 respectively. Hydraulic conductivity was the highest in forest-land and decreased in the order of agricultural land, grassland and wetland respectively. There was significant negative correlation between hydraulic conductivity and the bulk density and clay content of the soils. Reduced aggregate stability and lowered hydraulic conductivity is likely to be responsible for some of the severe soil erosion and other forms of land degradation observed in the River Njoro Watershed.

The structure of microbial community in aggregates of a typical chernozem aggregates under contrasting variants of its agricultural use

Science.gov (United States)

Ivanova, E. A.; Kutovaya, O. V.; Tkhakakhova, A. K.; Chernov, T. I.; Pershina, E. V.; Markina, L. G.; Andronov, E. E.; Kogut, B. M.

2015-11-01

The taxonomic structure of microbiomes in aggregates of different sizes from typical chernozems was investigated using sequencing of the 16S rRNA gene. The aggregate fractions of 7 mm obtained by sieving of the soil samples at natural moisture were used for analysis. The highest prokaryote biomass (bacteria, archaea) was determined in the fractions permanent black fallow > permanent winter wheat. The greatest number of fungi was recorded in the fraction wheat. The system of agricultural use affected more significantly the structure of the prokaryote community in the chernozem than the size of aggregate fractions did. The most diverse microbial community was recorded in the soil samples of the fallow; the statistically significant maximums of the Shannon diversity indices and indices of phylogenetic diversity (PD) were recorded in the fractions <0.25 and 2-5 mm from the fallow soil. On the whole, the fine soil fractions (<0.25 mm) were characterized by higher diversity indices in comparison with those of the coarser aggregate fractions.

Tillage-induced changes to soil structure and organic carbon fractions in New Zealand soils

International Nuclear Information System (INIS)

Shepherd, T. G.; Saggar, S.; Ross, C. W.; Dando, J. L.; Newman, R. H.

2001-01-01

The effects of increasing cropping and soil compaction on aggregate stability and dry-sieved aggregate-size distribution, and their relationship to total organic C (TOC) and the major functional groups of soil organic carbon, were investigated on 5 soils of contrasting mineralogy. All soils except the allophanic soil showed a significant decline in aggregate stability under medium- to long-term cropping. Mica-rich, fine-textured mineral and humic soils showed the greatest increase in the mean weight diameter (MWD) of dry aggregates, while the oxide-rich soils, and particularly the allophanic soils, showed only a slight increase in the MWD after long-term cropping. On conversion back to pasture, the aggregate stability of the mica-rich soils increased and the MWD of the aggregate-size distribution decreased, with the humic soil showing the greatest recovery. Aggregate stability and dry aggregate-size distribution patterns show that soil resistance to structural degradation and soil resilience increased from fine-textured to coarse-textured to humic mica-rich soils to oxide-rich soils to allophanic soils. Coarse- and fine-textured mica-rich and oxide-rich soils under pasture contained medium amounts of TOC, hot-water soluble carbohydrate (WSC), and acid hydrolysable carbohydrate (AHC), all of which declined significantly under cropping. The rate of decline varied with soil type in the initial years of cropping, but was similar under medium- and long-term cropping. TOC was high in the humic mica-rich and allophanic soils, and levels did not decline appreciably under medium- and long-term cropping. 13 C-nuclear magnetic resonance evidence also indicates that all major functional groups of soil organic carbon declined under cropping, with O-alkyl C and alkyl C showing the fastest and slowest rate of decline, respectively. On conversion back to pasture, both WSC and AHC returned to levels originally present under long-term pasture. TOC recovered to original pasture

Solid-state 13C NMR experiments reveal effects of aggregate size on the chemical composition of particulate organic matter in grazed steppe soils

Science.gov (United States)

Steffens, M.; Kölbl, A.; Kögel-Knabner, I.

2009-04-01

Grazing is one of the most important factors that may reduce soil organic matter (SOM) stocks and subsequently deteriorate aggregate stability in grassland topsoils. Land use management and grazing reduction are assumed to increase the input of OM, improve the soil aggregation and change species composition of vegetation (changes depth of OM input). Many studies have evaluated the impact of grazing cessation on SOM quantity. But until today little is known about the impact of grazing cessation on the chemical quality of SOM in density fractions, aggregate size classes and different horizons. The central aim of this study was to analyse the quality of SOM fractions in differently sized aggregates and horizons as affected by increased inputs of organic matter due to grazing exclusion. We applied a combined aggregate size, density and particle size fractionation procedure to sandy steppe topsoils with different organic matter inputs due to different grazing intensities (continuously grazed = Cg, winter grazing = Wg, ungrazed since 1999 = Ug99, ungrazed since 1979 = Ug79). Three different particulate organic matter (POM; free POM, in aggregate occluded POM and small in aggregate occluded POM) and seven mineral-associated organic matter fractions were separated for each of three aggregate size classes (coarse = 2000-6300 m, medium = 630-2000 m and fine =

Measurement of organic carbon stable isotope composition of different soil types by EA-IRMS system

International Nuclear Information System (INIS)

Qi Biao; Ding Lingling; Cui Jiehua; Wang Yanhong

2009-01-01

Element analyzer-isotope ratio mass spectrometers (EA-IRMS) is a rapid and precise method for measuring stable carbon isotope. Pure CO 2 reference gas was calibrated via international standard-Urea, and the δ 13 C us PDB value of pure CO 2 is (-29.523 ± 0.0181)%. Stability and linearity of the EA-IRMS system, precision of δ 13 C measurement for samples were tested through experimental comparison. Moreover, determination method of organic carbon stable isotope in soil was based on the system. The EA-IRMS system had well linearity when ion intensity ranged from 1.0 to 7.0V, and it excelled the total linearity when the ion intensity was from 1.5 to 5.0V, and the accurate result of δ 13 C for sample analysis could be obtained with precision of 0.015%. If carbon content in sample is more than 5μg, the requirement for analyzing accurate result of δ 13 C could be achieved. The organic carbon stable isotope was measured in 18 different types soil samples, the average natural abundance of 13 C was 1.082%, and the organic carbon stable isotope composition was significantly different among different type soils. (authors)

Stable, metastable, and kinetically trapped amyloid aggregate phases.

Science.gov (United States)

Miti, Tatiana; Mulaj, Mentor; Schmit, Jeremy D; Muschol, Martin

2015-01-12

Self-assembly of proteins into amyloid fibrils plays a key role in a multitude of human disorders that range from Alzheimer's disease to type II diabetes. Compact oligomeric species, observed early during amyloid formation, are reported as the molecular entities responsible for the toxic effects of amyloid self-assembly. However, the relation between early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. We show that these different structures occupy well-defined regions in a peculiar phase diagram. Lysozyme amyloid oligomers and their curvilinear fibrils only form after they cross a salt and protein concentration-dependent threshold. We also determine a boundary for the onset of amyloid oligomer precipitation. The oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. These experimentally determined boundaries match well with colloidal model predictions that account for salt-modulated charge repulsion. The model also incorporates the metastable and kinetic character of oligomer phases. Similarities and differences of amyloid oligomer assembly to metastable liquid-liquid phase separation of proteins and to surfactant aggregation are discussed.

Use of stable isotope techniques in soil organic matter studies

International Nuclear Information System (INIS)

Gerzabek, M.H.

1998-01-01

Plants differ distinctly in their C-isotopic composition. The largest differences occur between plant species with different photosynthetic pathways. C 3 - and C 4 -plants are differentiated by approximately 1.4% on the δ-scale (approx. -2.7% 13 C versus -1.3% 13 C). Modern elemental analyser - mass spectrometer combinations reach accuracies of at least 0.01% δ 13 C. Therefore, the difference between C 3 and C 4 plants is sufficient to be used for tracer studies. Several investigations of soil organic mater (SOM) turnover under field conditions were undertaken using the fact that the vegetation cover changed between C 3 and C 4 plants. The discrimination between SOM originating from indigenous vegetation (forest, C 3 ) and sugar cane (C 4 ) after 50 years of cropping introducing two SOM compartments of different stability was described. Another example is the change from prairie vegetation (C 4 ) to different C 3 -crops and the evaluation of the carbon origin at or near equilibrium. More recent studies use 15 N-labelled C 4 -plant residues or 13 C-labelled C 3 -plants to elucidate the fate of carbon and nitrogen in soils developed under C 3 -vegetation. Both in situ experiments and laboratory incubations were used to evaluate carbon and nitrogen fluxes from crop residues. Physical fractionation of bulk soil into particle sizes proved to be of advantage to follow short and long-term dynamics of crop residues within SOM. Changes in the natural abundance of 13 C and 15 N within soil profiles can elucidate leaching or mineralization of humic substances. Changes in the natural abundance of stable isotopes are also possible due to the application of organic manures, quantification, however is not easy because of the small isotopic differences between soil and manure carbon and nitrogen. 15 N labelling of soil nitrogen has been widely used in the last two decades to quantify biological nitrogen fixation. Considerable progress has been made due to the isotope dilution

Automatic Sieve-Shaker for Determining Soil Aggregate Stability and Dimensional Distribution Using a Vertical Oscillation System

Directory of Open Access Journals (Sweden)

Rosario Dell’Aquila

Full Text Available The soil aggregate stability is determined generally by sifting the soil samples in water using a sieve-shaker (wet sieving. The Author has developed an original model of automatic sieve-shaker using a vertical oscillation system to the aim of an its possible use to determine the soil aggregate stability and dimensional distribution. The purpose of this note is to describe the construction and performance of the prototype currently used in the Laboratory for the Soil Structure Study of the ISAFOM – CNR. The proposed sieve-shaker, with the introduction of some innovations (protected by Italy Patent 0001332102, realizes the submersion and levelling of the soil samples using a lifter to support the containers with the water. With 6 workplaces it allows to process simultaneously up to 6 soil samples according to different test cycles. By means of the control panel it is possible to set up various determinations with the stroke of 3 cm and the oscillation frequency from 4 up to 80 oscillations per minute. The performance of the proposed sieve-shaker was verified with a technical test to verify the performance of the 6 workplaces to oscillation speed increasing up to 60 oscillations per minute and an agronomic test. The results have been submitted to analysis of variance considering the plots of the field from which have been taken the samples for repetitions and the six workplaces of the proposed sieve-shaker for experimental theses. The differences between the various workplaces have not been significant. This demonstrates that the behavior of the various workplaces is uniform. The dispersion in water at constant shaking time and increasing oscillation speed has evidenced a very significant inverse relation between the index of aggregate stability in water (IASW and number of oscillations per minute. This result demonstrates a constant performance of the proposed sieve-shaker to varying of the oscillation speed. The agnonomic test has demonstrated

Automatic Sieve-Shaker for Determining Soil Aggregate Stability and Dimensional Distribution Using a Vertical Oscillation System

Directory of Open Access Journals (Sweden)

Rosario Dell’Aquila

2007-12-01

Full Text Available The soil aggregate stability is determined generally by sifting the soil samples in water using a sieve-shaker (wet sieving. The Author has developed an original model of automatic sieve-shaker using a vertical oscillation system to the aim of an its possible use to determine the soil aggregate stability and dimensional distribution. The purpose of this note is to describe the construction and performance of the prototype currently used in the Laboratory for the Soil Structure Study of the ISAFOM – CNR. The proposed sieve-shaker, with the introduction of some innovations (protected by Italy Patent 0001332102, realizes the submersion and levelling of the soil samples using a lifter to support the containers with the water. With 6 workplaces it allows to process simultaneously up to 6 soil samples according to different test cycles. By means of the control panel it is possible to set up various determinations with the stroke of 3 cm and the oscillation frequency from 4 up to 80 oscillations per minute. The performance of the proposed sieve-shaker was verified with a technical test to verify the performance of the 6 workplaces to oscillation speed increasing up to 60 oscillations per minute and an agronomic test. The results have been submitted to analysis of variance considering the plots of the field from which have been taken the samples for repetitions and the six workplaces of the proposed sieve-shaker for experimental theses. The differences between the various workplaces have not been significant. This demonstrates that the behavior of the various workplaces is uniform. The dispersion in water at constant shaking time and increasing oscillation speed has evidenced a very significant inverse relation between the index of aggregate stability in water (IASW and number of oscillations per minute. This result demonstrates a constant performance of the proposed sieve-shaker to varying of the oscillation speed. The agnonomic test has demonstrated

Effects of long-term fertilisation on aggregates and dynamics of soil organic carbon in a semi-arid agro-ecosystem in China

Directory of Open Access Journals (Sweden)

Jiaoyang Zhang

2018-05-01

Full Text Available Background Long-term fertilisation has a large influence on soil physical and chemical properties in agro-ecosystems. The effects on the distribution of aggregates, however, are not fully understood. We determined the dynamic change of the distribution of aggregates and soil organic carbon (SOC content over time in a long-term field experiment established in 1998 on the Loess Plateau of China and illustrated the relationship between them. Methods We determined SOC content and the distribution of aggregates in nine fertiliser treatments: manure (M; nitrogen (N; phosphorus (P; M and N; M, N, and P; M and P; N and P; bare land; and an unfertilised control. These parameters were then used for a path analysis and to analyse the fractal dimension (Dv. Results The organic fertiliser increased SOC content. The proportions of 0.1–0.25 mm microaggregates and 0.25–0.5 mm macroaggregates were higher and the proportion of the 0.01–0.05 mm size class of the silt + clay fraction was lower in the treatments receiving organic fertiliser (M, MN, MNP, and MP than that in the control, indicating that the addition of organic fertiliser promoted aggregation. The distribution of aggregates characterised by their fractal dimension (Dv, however, did not differ among the treatments. Discussion Dv was strongly correlated with the proportion of the <0.002 mm size class of the silt + clay fraction that did not differ significantly among the treatments. The change in the distribution of aggregates was strongly correlated with SOC content, which could produce organic polymer binding agents to increase the proportion of larger particles. Long-term application of organic fertiliser is thus necessary for the improvement and maintenance of soil quality in semi-arid agricultural land when residues are removed.

Copper in soil fractions and runoff in a vineyard catchment: Insights from copper stable isotopes

Energy Technology Data Exchange (ETDEWEB)

Babcsányi, Izabella; Chabaux, François; Granet, Mathieu; Meite, Fatima; Payraudeau, Sylvain; Duplay, Joëlle; Imfeld, Gwenaël, E-mail: imfeld@unistra.fr

2016-07-01

Understanding the fate of copper (Cu) fungicides in vineyard soils and catchments is a prerequisite to limit the off-site impact of Cu. Using Cu stable isotopes, Cu retention in soils and runoff transport was investigated in relation to the use of Cu fungicides and the hydrological conditions in a vineyard catchment (Rouffach, Haut-Rhin, France; mean slope: 15%). The δ{sup 65}Cu values of the bulk vineyard soil varied moderately through the depth of the soil profiles (− 0.12 to 0.24‰ ± 0.08‰). The values were in the range of those of the fungicides (− 0.21 to 0.11‰) and included the geogenic δ{sup 65}Cu value of the untreated soil (0.08‰). However, δ{sup 65}Cu values significantly differed between particle-size soil fractions (− 0.37 ± 0.10‰ in fine clays and 0.23 ± 0.07‰ in silt). Together with the soil mineralogy, the results suggested Cu isotope fractionation primarily associated with the clay and fine clay fractions that include both SOM and mineral phases. The vegetation did not affect the Cu isotope patterns in the vineyard soils. Cu export by runoff from the catchment accounted for 1% of the applied Cu mass from 11th May to 20{sup th} July 2011, covering most of the Cu use period. 84% of the exported Cu mass was Cu bound to suspended particulate matter (SPM). The runoff displayed δ{sup 65}Cu values from 0.52 to 1.35‰ in the dissolved phase (< 0.45 μm) compared to − 0.34 to − 0.02‰ in the SPM phase, indicating that clay and fine clay fractions were the main vectors of SPM-bound Cu in runoff. Overall, this study shows that Cu stable isotopes may allow identifying the Cu distribution in the soil fractions and their contribution to Cu export in runoff from Cu-contaminated catchments. - Highlights: • We investigated Cu sorption processes in vineyard soils and runoff transport. • Cu export by runoff from the catchment accounted for 1% of the applied Cu mass. • δ{sup 65}Cu values differed between the particle-size soil

Copper in soil fractions and runoff in a vineyard catchment: Insights from copper stable isotopes

International Nuclear Information System (INIS)

Babcsányi, Izabella; Chabaux, François; Granet, Mathieu; Meite, Fatima; Payraudeau, Sylvain; Duplay, Joëlle; Imfeld, Gwenaël

2016-01-01

Understanding the fate of copper (Cu) fungicides in vineyard soils and catchments is a prerequisite to limit the off-site impact of Cu. Using Cu stable isotopes, Cu retention in soils and runoff transport was investigated in relation to the use of Cu fungicides and the hydrological conditions in a vineyard catchment (Rouffach, Haut-Rhin, France; mean slope: 15%). The δ"6"5Cu values of the bulk vineyard soil varied moderately through the depth of the soil profiles (− 0.12 to 0.24‰ ± 0.08‰). The values were in the range of those of the fungicides (− 0.21 to 0.11‰) and included the geogenic δ"6"5Cu value of the untreated soil (0.08‰). However, δ"6"5Cu values significantly differed between particle-size soil fractions (− 0.37 ± 0.10‰ in fine clays and 0.23 ± 0.07‰ in silt). Together with the soil mineralogy, the results suggested Cu isotope fractionation primarily associated with the clay and fine clay fractions that include both SOM and mineral phases. The vegetation did not affect the Cu isotope patterns in the vineyard soils. Cu export by runoff from the catchment accounted for 1% of the applied Cu mass from 11th May to 20"t"h July 2011, covering most of the Cu use period. 84% of the exported Cu mass was Cu bound to suspended particulate matter (SPM). The runoff displayed δ"6"5Cu values from 0.52 to 1.35‰ in the dissolved phase (< 0.45 μm) compared to − 0.34 to − 0.02‰ in the SPM phase, indicating that clay and fine clay fractions were the main vectors of SPM-bound Cu in runoff. Overall, this study shows that Cu stable isotopes may allow identifying the Cu distribution in the soil fractions and their contribution to Cu export in runoff from Cu-contaminated catchments. - Highlights: • We investigated Cu sorption processes in vineyard soils and runoff transport. • Cu export by runoff from the catchment accounted for 1% of the applied Cu mass. • δ"6"5Cu values differed between the particle-size soil fractions. • The clay soil

Impact of monovalent cations on soil structure. Part I. Results of an Iranian soil

Science.gov (United States)

Farahani, Elham; Emami, Hojat; Keller, Thomas; Fotovat, Amir; Khorassani, Reza

2018-01-01

This study investigated the impact of monovalent cations on clay dispersion, aggregate stability, soil pore size distribution, and saturated hydraulic conductivity on agricultural soil in Iran. The soil was incubated with treatment solutions containing different concentrations (0-54.4 mmol l-1) of potassium and sodium cations. The treatment solutions included two levels of electrical conductivity (EC=3 or 6 dS m-1) and six K:Na ratios per electrical conductivity level. At both electrical conductivity levels, spontaneously dispersible clay increased with increasing K concentration, and with increasing K:Na ratio. A negative linear relationship between percentage of water-stable aggregates and spontaneously dispersible clay was observed. Clay dispersion generally reduced the mean pore size, presumably due to clogging of pores, resulting in increased water retention. At both electrical conductivity levels, hydraulic conductivity increased with increasing exchangeable potassium percentage at low exchangeable potassium percentage values, but decreased with further increases in exchangeable potassium percentage at higher exchangeable potassium percentage. This is in agreement with earlier studies, but seems in conflict with our data showing increasing spontaneously dispersible clay with increasing exchangeable potassium percentage. Our findings show that clay dispersion increased with increasing K concentration and increasing K:Na ratio, demonstrating that K can have negative impacts on soil structure.

Evaluating effects of sewage sludge and household compost on soil physical, chemical and microbiological properties

DEFF Research Database (Denmark)

Debosz, K.; Petersen, S.O.; Kure, L.K.

2002-01-01

Recycling of organic wastes within agriculture may help maintain soil fertility via effects on physical, chemical and biological properties. Efficient use, however, requires an individual assessment of waste products, and effects should be compared with natural variations due to climate and soil......C, as well as in the field. The following properties were monitored: wet-stability of soil aggregates, clay dispersibility, hot-water extractable carbohydrates, resin-extractable P-i, inorganic N, biomass C and N, PLFA profiles, FDA hydrolysis activity, beta-glucosidase activity and CO2 evolution. In general...... amendment on the fraction of soil in wet-stable aggregates, or on the microbiological properties tested, which supported the observation from the incubation study that effects of organic wastes were transient. (C) 2002 Elsevier Science B.V. All rights reserved....

Nematode grazing promotes bacterial community dynamics in soil at the aggregate level.

Science.gov (United States)

Jiang, Yuji; Liu, Manqiang; Zhang, Jiabao; Chen, Yan; Chen, Xiaoyun; Chen, Lijun; Li, Huixin; Zhang, Xue-Xian; Sun, Bo

2017-12-01

Nematode predation has important roles in determining bacterial community composition and dynamics, but the extent of the effects remains largely rudimentary, particularly in natural environment settings. Here, we investigated the complex microbial-microfaunal interactions in the rhizosphere of maize grown in red soils, which were derived from four long-term fertilization regimes. Root-free rhizosphere soil samples were separated into three aggregate fractions whereby the abundance and community composition were examined for nematode and total bacterial communities. A functional group of alkaline phosphomonoesterase (ALP) producing bacteria was included to test the hypothesis that nematode grazing may significantly affect specific bacteria-mediated ecological functions, that is, organic phosphate cycling in soil. Results of correlation analysis, structural equation modeling and interaction networks combined with laboratory microcosm experiments consistently indicated that bacterivorous nematodes enhanced bacterial diversity, and the abundance of bacterivores was positively correlated with bacterial biomass, including ALP-producing bacterial abundance. Significantly, such effects were more pronounced in large macroaggregates than in microaggregates. There was a positive correlation between the most dominant bacterivores Protorhabditis and the ALP-producing keystone 'species' Mesorhizobium. Taken together, these findings implicate important roles of nematodes in stimulating bacterial dynamics in a spatially dependent manner.

Soil aggregate stability and size-selective sediment transport with surface runoff as affected by organic residue amendment.

Science.gov (United States)

Shi, Pu; Arter, Christian; Liu, Xingyu; Keller, Martin; Schulin, Rainer

2017-12-31

Aggregate breakdown influences the availability of soil particles for size-selective sediment transport with surface runoff during erosive rainfall events. Organic matter management is known to affect aggregate stability against breakdown, but little is known about how this translates into rainfall-induced aggregate fragmentation and sediment transport under field conditions. In this study, we performed field experiments in which artificial rainfall was applied after pre-wetting on three pairs of arable soil plots (1.5×0.75m) six weeks after incorporating a mixture of grass and wheat straw into the topsoil of one plot in each pair (OI treatment) but not on the other plot (NI treatment). Artificial rainfall was applied for approximately 2h on each pair at an intensity of 49.1mmh -1 . In both treatments, discharge and sediment concentration in the discharge were correlated and followed a similar temporal pattern after the onset of surface runoff: After a sharp increase at the beginning both approached a steady state. But the onset of runoff was more delayed on the OI plots, and the discharge and sediment concentration were in average only roughly half as high on the OI as on the NI plots. With increasing discharge the fraction of coarse sediment increased. This relationship did not differ between the two treatments. Thus, due to the lower discharge, the fraction of fine particles in the exported sediment was larger in the runoff from the OI plots than from the NI plots. The later runoff onset and lower discharge rate was related to a higher initial aggregate stability on the OI plots. Terrestrial laser scanning proved to be a very valuable method to map changes in the micro-topography of the soil surfaces. It revealed a much less profound decrease in surface roughness on the OI than on the NI plots. Copyright © 2017 Elsevier B.V. All rights reserved.

Disentangling drought-induced variation in ecosystem and soil respiration using stable carbon isotopes.

Science.gov (United States)

Unger, Stephan; Máguas, Cristina; Pereira, João S; Aires, Luis M; David, Teresa S; Werner, Christiane

2010-08-01

Combining C flux measurements with information on their isotopic composition can yield a process-based understanding of ecosystem C dynamics. We studied the variations in both respiratory fluxes and their stable C isotopic compositions (delta(13)C) for all major components (trees, understory, roots and soil microorganisms) in a Mediterranean oak savannah during a period with increasing drought. We found large drought-induced and diurnal dynamics in isotopic compositions of soil, root and foliage respiration (delta(13)C(res)). Soil respiration was the largest contributor to ecosystem respiration (R (eco)), exhibiting a depleted isotopic signature and no marked variations with increasing drought, similar to ecosystem respired delta(13)CO(2), providing evidence for a stable C-source and minor influence of recent photosynthate from plants. Short-term and diurnal variations in delta(13)C(res) of foliage and roots (up to 8 and 4 per thousand, respectively) were in agreement with: (1) recent hypotheses on post-photosynthetic fractionation processes, (2) substrate changes with decreasing assimilation rates in combination with increased respiratory demand, and (3) decreased phosphoenolpyruvate carboxylase activity in drying roots, while altered photosynthetic discrimination was not responsible for the observed changes in delta(13)C(res). We applied a flux-based and an isotopic flux-based mass balance, yielding good agreement at the soil scale, while the isotopic mass balance at the ecosystem scale was not conserved. This was mainly caused by uncertainties in Keeling plot intercepts at the ecosystem scale due to small CO(2) gradients and large differences in delta(13)C(res) of the different component fluxes. Overall, stable isotopes provided valuable new insights into the drought-related variations of ecosystem C dynamics, encouraging future studies but also highlighting the need of improved methodology to disentangle short-term dynamics of isotopic composition of R (eco).

Soil compaction: Evaluation of stress transmission and resulting soil structure

Science.gov (United States)

Naveed, Muhammad; Schjønning, Per; Keller, Thomas; Lamande, Mathieu

2016-04-01

Accurate estimation of stress transmission and resultant deformation in soil profiles is a prerequisite for the development of predictive models and decision support tools for preventing soil compaction. Numerous studies have been carried out on the effects of soil compaction, whilst relatively few studies have focused on the cause (mode of stress transmission in the soil). We have coupled both cause and effects together in the present study by carrying out partially confined compression tests on (1) wet aggregates, (2) air dry aggregates, and (3) intact soils to quantify stress transmission and compaction-resulted soil structure at the same time. Stress transmission was quantified using both X-ray CT and Tactilus sensor mat, and soil-pore structure was quantified using X-ray CT. Our results imply that stress transmission through soil highly depends on the magnitude of applied load and aggregate strength. As soon as the applied load is lower than the aggregate strength, the mode of stress transmission is discrete as stresses were mainly transmitted through chain of aggregates. With increasing applied load soil aggregates start deforming that transformed heterogeneous soil into homogenous, as a result stress transmission mode was shifted from discrete towards more like a continuum. Continuum-like stress transmission mode was better simulated with Boussinesq (1885) model based on theory of elasticity compared to discrete. The soil-pore structure was greatly affected by increasing applied stresses. Total porosity was reduced 5-16% and macroporosity 50-85% at 620 kPa applied stress for the intact soils. Similarly, significant changes in the morphological indices of the macropore space were also observed with increasing applied stresses.

Soil compaction: Evaluation of stress transmission and resulting soil structure

DEFF Research Database (Denmark)

Naveed, Muhammad; Schjønning, Per; Keller, Thomas

strength. As soon as the applied load is lower than the aggregate strength, the mode of stress transmission is discrete as stresses were mainly transmitted through chain of aggregates. With increasing applied load soil aggregates start deforming that transformed heterogeneous soil into homogenous......, as a result stress transmission mode was shifted from discrete towards more like a continuum. Continuum-like stress transmission mode was better simulated with Boussinesq (1885) model based on theory of elasticity compared to discrete. The soil-pore structure was greatly affected by increasing applied...... and compaction-resulted soil structure at the same time. Stress transmission was quantified using both X-ray CT and Tactilus sensor mat, and soil-pore structure was quantified using X-ray CT. Our results imply that stress transmission through soil highly depends on the magnitude of applied load and aggregate...

Combined use of stable isotopes and fallout radionuclides as soil erosion indicators in a forested mountain site, South Korea

International Nuclear Information System (INIS)

Meusburger, K.; Mabit, L.; Alewell, C.; Park, J.H.; Sandor, T.

2013-01-01

The aim of this study is to assess and to validate the suitability of the stable nitrogen and carbon isotope signature as soil erosion indicators in a mountain forest site in South Korea. Our approach is based on the comparison of the isotope signature of ''stable'' landscape positions (reference sites), which are neither affected by erosion nor deposition, with eroding sites. For undisturbed soils we expect that the enrichment of δ 15 N and δ 13 C with soil depth, due to fractionation during decomposition, goes in parallel with a decrease in nitrogen and carbon content. Soil erosion processes potentially weaken this correlation. The 137 Cs method and the Revised Universal Soil Loss Equation (RUSLE) were applied for the soil erosion quantification. Erosion rates obtained with the 137 Cs method range from 0.9 t ha -1 yr -1 to 7 t ha -1 yr -1 . Considering the steep slopes of up to 40 and the erosive monsoon events (R factor of 6600 MJ mm ha -1 h -1 yr -1 ), the rates are plausible and within the magnitude of the RUSLE-modeled soil erosion rates, varying from 0.02 t ha -1 yr -1 to 5.1 t ha -1 yr -1 . The soil profiles of the reference sites showed significant (p < 0.0001) correlations between nitrogen and carbon content and its corresponding δ 15 N and δ 13 C signatures. In contrast, for the eroding sites this relationship was weaker and for the carbon not significant. These results confirm the usefulness of the stable carbon isotope signature as a qualitative indicator for soil disturbance. We could show further that the δ 15 N isotope signature can be used similarly for uncultivated sites. We thus propose that the stable δ 15 N and δ 13 C signature of soil profiles could serve as additional indicators confirming the accurate choice of the reference site in soil erosion studies using the 137 Cs method.

On-line stable isotope measurements during plant and soil gas exchange

International Nuclear Information System (INIS)

Yakir, D.

2001-01-01

Recent techniques for on-line stable isotope measurements during plant and soil exchange of CO 2 and/or water vapor are briefly reviewed. For CO 2 , these techniques provide means for on-line measurements of isotopic discrimination during CO 2 exchange by leaves in the laboratory and in the field, of isotopic discrimination during soil respiration and during soil-atmosphere CO 2 exchange, and of isotopic discrimination in O 2 during plant respiration. For water vapor, these techniques provide means to measure oxygen isotopic composition of water vapor during leaf transpiration and for the analysis of sub microliter condensed water vapor samples. Most of these techniques involve on-line sampling of CO 2 and water vapor from a dynamic, intact soil or plant system. In the laboratory, these systems also allow on-line isotopic analysis by continuous-flow isotope ratio mass spectrometry. The information obtained with these on-line techniques is becoming increasingly valuable, and often critical, for ecophysiologial research and in the study of biosphere-atmosphere interactions. (author)

Sodium Contents in Dairy Cow Urine and Soil Aggregate Sizes Influence the Amount of Nitrogen Lost from Soil

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Toru Hamamoto

2015-01-01

Full Text Available Cow urine deposition on pasture soils is a major source of N-related environmental impacts in the dairy farming systems. The urine-N can potentially be lost to the ground water as nitrate (NO3- and to the atmosphere as nitrous oxide (N2O. These N-related environmental impacts are possibly related to the sodium (Na+ concentrations in urine. We sampled a pasture soil and separated it into three aggregate size groups (0–3, 3–5, and 5–7 mm. Then, cow urine with variable Na+ concentrations (4.3–6.1 g Na+ L−1 was added to the soil cores. We treated the cores with simulated heavy rains and measured the amounts of calcium (Ca2+, Na+, potassium (K+, and inorganic-N leached from the soils. N2O emission rates were also determined throughout the experimental period. Increasing Na+ concentration in urine decreased the loss of NO3- (−20%, after repeatedly applied simulated rain treatments (30 mm × 3, whereas it increased the loss of ammonium (31% and K+ (19%. For the loss of Ca2+ and the emissions of N2O, the effect of the Na+ concentrations was unclear. Field level studies and studies focusing on the mechanisms behind the changes in nutrient losses are needed.

Efficacy of Natural Polymer Derivatives on Soil Physical Properties and Erosion on an Experimental Loess Hillslope.

Science.gov (United States)

Liu, Jun'e; Wang, Zhanli; Li, Yuanyuan

2017-12-22

Raindrops disperse large soil aggregates into smaller particles, which can clog soil pores, cause soil crusting, reduce rainfall infiltration and increase soil loss. It was found that natural polymer derivatives were effective in improving soil physical properties and decreasing soil erosion on an experimental loess hillslope. This study investigated the effect of new natural polymer derivatives (Jag S and Jag C162) on soil properties, rainfall infiltration and sediment yield at four rates of sprayed polymers (0, 1, 3 and 5 g/m²), three rainfall intensities (1, 1.5 and 2 mm/min) and a slope gradient of 15° with a silt loam soil through simulated rain. The results showed that both Jag S and Jag C162 significantly increased the shear strength and improved the aggregates composition of the soil surface. The water-stable soil aggregates >0.25 mm increased from 9% to 50% with increasing rates of Jag S and Jag C162. Jag S and Jag C162 also effectively increased rainfall infiltration and final infiltration rate, and reduced erosion compared to controls without natural polymer derivatives added. However, higher rates of Jag S produced lower infiltration rates. Although both Jag S and Jag C162 effectively influenced soil physical properties and erosion, the effect of Jag C162 was more significant than that of Jag S.

Efficacy of Natural Polymer Derivatives on Soil Physical Properties and Erosion on an Experimental Loess Hillslope

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Jun’e Liu

2017-12-01

Full Text Available Raindrops disperse large soil aggregates into smaller particles, which can clog soil pores, cause soil crusting, reduce rainfall infiltration and increase soil loss. It was found that natural polymer derivatives were effective in improving soil physical properties and decreasing soil erosion on an experimental loess hillslope. This study investigated the effect of new natural polymer derivatives (Jag S and Jag C162 on soil properties, rainfall infiltration and sediment yield at four rates of sprayed polymers (0, 1, 3 and 5 g/m2, three rainfall intensities (1, 1.5 and 2 mm/min and a slope gradient of 15° with a silt loam soil through simulated rain. The results showed that both Jag S and Jag C162 significantly increased the shear strength and improved the aggregates composition of the soil surface. The water-stable soil aggregates >0.25 mm increased from 9% to 50% with increasing rates of Jag S and Jag C162. Jag S and Jag C162 also effectively increased rainfall infiltration and final infiltration rate, and reduced erosion compared to controls without natural polymer derivatives added. However, higher rates of Jag S produced lower infiltration rates. Although both Jag S and Jag C162 effectively influenced soil physical properties and erosion, the effect of Jag C162 was more significant than that of Jag S.

Efficacy of Natural Polymer Derivatives on Soil Physical Properties and Erosion on an Experimental Loess Hillslope

Science.gov (United States)

Liu, Jun’e; Wang, Zhanli; Li, Yuanyuan

2017-01-01

Raindrops disperse large soil aggregates into smaller particles, which can clog soil pores, cause soil crusting, reduce rainfall infiltration and increase soil loss. It was found that natural polymer derivatives were effective in improving soil physical properties and decreasing soil erosion on an experimental loess hillslope. This study investigated the effect of new natural polymer derivatives (Jag S and Jag C162) on soil properties, rainfall infiltration and sediment yield at four rates of sprayed polymers (0, 1, 3 and 5 g/m2), three rainfall intensities (1, 1.5 and 2 mm/min) and a slope gradient of 15° with a silt loam soil through simulated rain. The results showed that both Jag S and Jag C162 significantly increased the shear strength and improved the aggregates composition of the soil surface. The water-stable soil aggregates >0.25 mm increased from 9% to 50% with increasing rates of Jag S and Jag C162. Jag S and Jag C162 also effectively increased rainfall infiltration and final infiltration rate, and reduced erosion compared to controls without natural polymer derivatives added. However, higher rates of Jag S produced lower infiltration rates. Although both Jag S and Jag C162 effectively influenced soil physical properties and erosion, the effect of Jag C162 was more significant than that of Jag S. PMID:29271899

Mobility and plant availability of radioactive Cs in natural soil in relation to stable Cs, other alkali elements and soil fertility

International Nuclear Information System (INIS)

Varskog, P.; Steinnes, E.; Naeumann, R.

1994-01-01

The mobility and plant availability of radioactive Cs from the Chernobyl accident in natural soil-plant systems of varying fertility were studied at three sampling locations situated in subalpine areas of central Norway. The soil samples included litter, humus (0-2 cm and 2-5 cm depth), and mineral soil (8-12 cm and 20-30 cm depth), and the plant species studied were Betula nana, Empetrum hermaphroditum and Juncus trifidus. The lichen Cetraria nivalis was also sampled. The sampling took place in the middle of the growth season during the period 1987-1989. The soil and vegetation samples were analysed with respect to total radiocaesium ( 137 Cs and 134 Cs), Rb, stable Cs and exchangeable 137 Cs (in soil only), K, Ca and Mg. (Author)

Effects of Soil Compaction on Carbon and Nitrogen Sequestration in Soil and Wheat, Soil Physical Properties and Aggregates Stability (Case study: Northern of Aq Qala

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Z. Saieedifar

2016-09-01

Full Text Available Introduction: Soil compaction has become a widespread problem in the world and it is considered as one of the main factors affecting land degradation in arid and semi-arid agricultural land. Compaction in arable soils is a gradual phenomenon that appearing over time and most important factors that influence it include: soil properties, high clay content, low organic matter, and frequency of wet-dry in the soil, impervious layer of soil, load heavy agricultural implements and soil and water mismanagement. Compaction induced soil degradation affects about 68 million hectares of land globally. The vast majority of compaction in modern agriculture is caused by vehicular traffic. Carbon sequestration by long-term management operation of the plant and soil, not only increase the soil carbon storage but also lead to reduce the carbon exchange and greenhouse gases emissions like CO2 from the soil profile. The aim of this study was evaluating the effect of soil compaction on carbon and nitrogen sequestration of wheat and soil and some soil physical properties such as: aggregate stability, saturated soil moisture content, bulk density and soil porosity. Materials and Methods: This experiment was accomplished in which is located near Aq Qala in a randomized completely block design (with 4 treatments and 3 replications. Soil compaction was artificially created by using a 5/7 ton heavy tractor. The treatments arrangements were: 1 T1: control, 2 T2: twice passing of tractor, 3 T3: four time of passing tractor, and 4 T4: six time of passing heavy tractor. Utilize of all agricultural inputs (fertilizers, herbicides, etc. has been identical for all treatments. Since rain-fed farming is the common method to cultivation of cereals in the study area, so no complementary irrigation was carried out in this period. In this study, after the measurement of the parameters, the data were analyzed by using SPSS 16.0 Software. LSD test was used for comparison of means

Disruption of mycorrhizal extraradical mycelium and changes in leaf water status and soil aggregate stability in rootbox-grown trifoliate orange

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Ying-Ning eZou

2015-03-01

Full Text Available Arbuscular mycorrhizas possess well developed extraradical mycelium (ERM network that enlarge the surrounding soil for better acquisition of water and nutrients, besides soil aggregation. Distinction in ERM functioning was studied under a rootbox system, which consisted of root+hyphae and root-free hyphae compartments separated by 37-μm nylon mesh with an air gap. Trifoliate orange (Poncirus trifoliata seedlings were inoculated with Funneliformis mosseae in root+hyphae compartment, and the ERM network was established between the two compartments. The ERM network of air gap was disrupted before 8 h of the harvest (one time disruption or multiple disruptions during seedlings acclimation. Our results showed that mycorrhizal inoculation induced a significant increase in growth (plant height, stem diameter, and leaf, stem, and root biomass and physiological characters (leaf relative water content, leaf water potential, and transpiration rate, irrespective of ERM status. Easily-extractable glomalin-related soil protein (EE-GRSP and total GRSP (T-GRSP concentration and mean weight diameter (MWD, an indicator of soil aggregate stability were significantly higher in mycorrhizosphere of root+hyphae and root-free hyphae compartments than non-mycorrhizosphere. One time disruption of ERM network did not influence plant growth and soil properties but only notably decreased leaf water. Periodical disruption of ERM network at weekly interval markedly inhibited the mycorrhizal roles on plant growth, leaf water, GRSP production, and MWD in root+hyphae and hyphae chambers. EE-GRSP was the most responsive GRSP fraction to changes in leaf water and MWD under root+hyphae and hyphae conditions. It suggests that effect of peridical disruption of ERM network was more impactful than one-time disruption of ERM network with regard to leaf water, plant growth, and aggregate stability responses, thereby, implying ERM network aided in developing the host plant metabolically

RECIPROCAL RELATIONSHIPS BETWEEN AGGREGATE STABILITY AND ORGANIC CARBON CHARACTERISTICS IN A FORESTED ECOSYSTEM OF NORTHERN NIGERIA

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Halima Mohammed Lawal

2012-10-01

Full Text Available Soil organic matter associated with different size aggregates differ in structure and function; therefore, play different roles in soil organic carbon (SOC turnover. This study assessed the relationship between aggregate stability and soil organic carbon fractions in a forested soil. Aggregate stability characterized by mean weight diameter (MWD was correlated with the various pools of SOC in a regression model. Mean weight diameter presented a 46% influence on total organic carbon (TOC while, TOC accounts for 21.8% 0f aggregate stability. The unprotected and physically protected soil organic carbon did not significantly dictate stability of these soils. However, chemically protected and biochemically protected SOC influenced significantly aggregate stability of these forested soils.

Microbial degradation of alpha-cypermethrin in soil by compound-specific stable isotope analysis

Energy Technology Data Exchange (ETDEWEB)

Xu, Zemin [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Shen, Xiaoli [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Department of Environmental Engineering, Quzhou University, Quzhou 324000 (China); Zhang, Xi-Chang [Laboratory for Teaching in Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Liu, Weiping [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Yang, Fangxing, E-mail: fxyang@zju.edu.cn [MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Department of Effect-Directed Analysis, Helmholtz Center for Environmental Research – UFZ, Leipzig 04318 (Germany)

2015-09-15

Highlights: • Alpha-cypermethrin (α-CP) can be degraded by microorganisms in soil. • Biodegradation of α-CP resulted in carbon isotope fractionation. • A relationship was found between carbon isotope ratios and concentrations of α-CP. • An enrichment factor ϵ of α-CP was determined as −1.87‰. • CSIA is applicable to assess biodegradation of α-CP. - Abstract: To assess microbial degradation of alpha-cypermethrin in soil, attenuation of alpha-cypermethrin was investigated by compound-specific stable isotope analysis. The variations of the residual concentrations and stable carbon isotope ratios of alpha-cypermethrin were detected in unsterilized and sterilized soils spiked with alpha-cypermethrin. After an 80 days’ incubation, the concentrations of alpha-cypermethrin decreased to 0.47 and 3.41 mg/kg in the unsterilized soils spiked with 2 and 10 mg/kg, while those decreased to 1.43 and 6.61 mg/kg in the sterilized soils. Meanwhile, the carbon isotope ratios shifted to −29.14 ± 0.22‰ and −29.86 ± 0.33‰ in the unsterilized soils spiked with 2 and 10 mg/kg, respectively. The results revealed that microbial degradation contributed to the attenuation of alpha-cypermethrin and induced the carbon isotope fractionation. In order to quantitatively assess microbial degradation, a relationship between carbon isotope ratios and residual concentrations of alpha-cypermethrin was established according to Rayleigh equation. An enrichment factor, ϵ = −1.87‰ was obtained, which can be employed to assess microbial degradation of alpha-cypermethrin. The significant carbon isotope fractionation during microbial degradation suggests that CSIA is a proper approach to qualitatively detect and quantitatively assess the biodegradation during attenuation process of alpha-cypermethrin in the field.

Soil fertility management: Impacts on soil macrofauna, soil aggregation and soil organic matter allocation.

NARCIS (Netherlands)

Ayuke, F.O.; Brussaard, L.; Vanlauwe, B.; Six, J.; Lelei, D.K.; Kibunja, C.N.; Pulleman, M.M.

2011-01-01

Maintenance of soil organic matter through integrated soil fertility management is important for soil quality and agricultural productivity, and for the persistence of soil faunal diversity and biomass. Little is known about the interactive effects of soil fertility management and soil macrofauna

Aggregate hierarchy and chemical exchange reactions

International Nuclear Information System (INIS)

Gerzabek, M.H.

1994-01-01

Recent publications show that macroaggregates (> 250 μm) may consist of microaggregates (20-250 μm) in soils, which contain organic colloids. Roots and hyphae have a potential role in the formation of macroaggregates. Fragments of roots and hyphae may serve as nuclei for smaller aggregates. This implicates that aggregate factions contain organic material of different characteristics. Especially humus in microaggregates may play a keyrole for the mobility of elements in the soil. E.g. radiocaesium extractability in the silt fraction of a Calcic Chemozem and soil-to-plant transfer was distinctly enhanced due to seven times higher C org -contents as compared to an Eutric Cambisol

Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals

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M. Schrumpf

2013-03-01

Full Text Available Conceptual models suggest that stability of organic carbon (OC in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Density fractionation is a useful tool to study the relevance of OC stabilization in aggregates and in association with minerals, but it has rarely been applied to full soil profiles. We aim to determine factors shaping the depth profiles of physically unprotected and mineral associated OC and test their relevance for OC stability across a range of European soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF were analysed for OC, total nitrogen (TN, δ14C, and Δ14C. Bulk samples were also incubated to determine CO2 evolution per g OC in the samples (specific mineralization rates as an indicator for OC stability. Depth profiles of OC in the light fraction (LF-OC matched those of roots for undisturbed grassland and forest sites, suggesting that roots are shaping the depth distribution of LF-OC. Organic C in the HF declined less with soil depth than LF-OC and roots, especially at grassland sites. The decrease in Δ14C (increase in age of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the Δ14C profiles. The LF at three sites were rather depleted in 14C, indicating the presence of fossil material such as coal and lignite, probably inherited from the parent material. At the other sites, modern Δ14C signatures and positive correlations between specific mineralization rates and fLF-OC indicate the fLF is a potentially available energy and

Morfologia de agregados do solo avaliada por meio de análise de imagens Morphology of soil aggregates evaluated by images analysis

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N. Olszevski

2004-10-01

deterioration of soil physical properties, mainly due to modifications in the soil structure pattern. Once the structural changes could affect the morphology aggregates in different ways, the search for new methods of studying soil macro-morphological characteristics must be prioritized to allow the observation of modified characteristics in cultivated soils. Therefore, this study was carried out to adapt and test a digital method for a qualitative macro-morphological analysis of soil aggregates of Rodhic Haplustox in samples taken in 1998, aiming to detect morphological modifications caused by human activities. From an original set of eleven, five replicated treatments were selected: no till, cinzel plow, heavy disk harrow, disk plow and chisel plow, carried out annually. The shape of the different soil aggregates was from images obtained using a scanner (HP 6100C with 1200 dpi optical resolution which were then processed by the computer program UTHSCSA Image Tool. This program furnishes values of different aggregate indexes: roundness, compactness and lengthiness. The roundness index depends on the perimeter measurement (external roughness and the compactness and lengthiness indexes depend on the measurement of the length of the longest axle (long edges. Generally, the management systems used during three consecutive years did not modify the aggregate morphology of the clayey Rodhic Haplustox for the analyzed variables. Image analysis sensitively detected alterations in soil aggregate morphology promising considerable usefulness as a novel tool for on soil structure studies.

Agregação e estabilidade de agregados do solo em sistemas agropecuários em Mato Grosso do Sul Soil aggregation and aggregate stability under crop-pasture systems in Mato Grosso do Sul state, Brazil

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Júlio Cesar Salton

2008-02-01

Full Text Available Sistemas de manejo do solo, incluindo lavouras em plantio direto, lavouras (soja em rotação com pastagens em plantio direto e pastagens permanentes (Brachiaria sp., foram avaliados quanto à agregação do solo e estabilidade dos agregados. Em três experimentos de longa duração (9 e 11 anos localizados em Mato Grosso do Sul, o solo foi amostrado nas camadas de 0 a 5, 5 a 10 e 10 a 20 cm, para determinação da estabilidade dos agregados em água e a seco. Foram calculados o diâmetro médio ponderado (DMP e o índice de estabilidade dos agregados (IEA. Em todos os experimentos, nos sistemas com pastagens, seja de forma isolada ou em rotação com lavouras, foi verificado maior volume do solo, constituindo agregados com tamanho superior a 4,76 mm. Os sistemas com pastagens também apresentaram maior DMP e maior IEA em todos os experimentos. O sistema apenas com lavouras apresentou, nos três experimentos, o maior volume de solo com agregados de tamanho entre 0,25 e 2,00 mm. Esses efeitos ocorreram de forma semelhante em todas as profundidades avaliadas. Entre os locais, observou-se o efeito do teor de argila na agregação, sendo maior em Maracaju e menor em Campo Grande. Foi observada estreita relação entre a estabilidade dos agregados e o teor de C no solo. A formação de macroagregados parece estar relacionada à presença de raízes, que são mais abundantes sob pastagem de gramíneas.Soil management systems, with crops under no-tillage (NT, crops (soybean in rotation with pastures under NT and permanent pastures (Brachiaria sp., were evaluated for soil aggregation and aggregate stability. Three long-term experiments (9 and 11 years in the state of Mato Grosso do Sul were sampled in the layers 0-5, 5-10 and 10-20 cm for determination of the aggregate stability in wet and dry sieving. The mean weight diameter (MWD and the aggregate stability index (IAS were calculated. In all experiments, the greatest soil volume was verified in the

Indicators of structural degradation on intensively cultivated soils of the Piedemonte Llanero

International Nuclear Information System (INIS)

Obando, Franco H

2000-01-01

In order to evaluate the validity of a diagnosis methodology of structural soil degradation based on the combination of internal morphology of aggregates and measurement of resistance to penetration, a reconnaissance survey of physical degradation processes on intensively cultivated soils in the Piedemonte Llanero was carried out. The internal morphology of soil aggregates was classified into five states; micro-aggregate (μ), compacted (∇ μ), very compacted (∇), cracked compacted (φ) and agglomerate (ψ) defined according to morphological characteristics derived from cultivation practices and wheel traffic. Two crops systems were selected: low-lying rice (mono-cropping) during 30 years) and upland rice, maize, soybean cotton crop rotations during 20 years in two landscapes of the alluvial plain of piedmont (medium terraces of the sub-recent piedmont, TM, and No-flooding Lowland Flats of the Recent Piedmont, PR). A natural forest and 20 years cacao tree plantation was include as benchmark systems. It was found that higher values of resistance to penetration and total density are associated to compact layers (∇ μ, ∇ and φ states) and lower values to the μ a ψ states. The ∇ state was particularly evident on TM under mono-cropping e low-lying rice crop. High values of resistance to penetration of topsoil on PR were rather associated to e textural resistance. Under natural forest and cacao e plantation it was found the micro-aggregate state (μ) o on surface soil. High values of weighed mean diameter of water stable aggregates, DMP, (≥ 5mm) were associated to compacted layers in the crop rotation e systems in PR. it was demonstrated that this methodology developed in France (temperate zone) can be applied to tropical soils

Copper in soil fractions and runoff in a vineyard catchment: Insights from copper stable isotopes.

Science.gov (United States)

Babcsányi, Izabella; Chabaux, François; Granet, Mathieu; Meite, Fatima; Payraudeau, Sylvain; Duplay, Joëlle; Imfeld, Gwenaël

2016-07-01

Understanding the fate of copper (Cu) fungicides in vineyard soils and catchments is a prerequisite to limit the off-site impact of Cu. Using Cu stable isotopes, Cu retention in soils and runoff transport was investigated in relation to the use of Cu fungicides and the hydrological conditions in a vineyard catchment (Rouffach, Haut-Rhin, France; mean slope: 15%). The δ(65)Cu values of the bulk vineyard soil varied moderately through the depth of the soil profiles (-0.12 to 0.24‰±0.08‰). The values were in the range of those of the fungicides (-0.21 to 0.11‰) and included the geogenic δ(65)Cu value of the untreated soil (0.08‰). However, δ(65)Cu values significantly differed between particle-size soil fractions (-0.37±0.10‰ in fine clays and 0.23±0.07‰ in silt). Together with the soil mineralogy, the results suggested Cu isotope fractionation primarily associated with the clay and fine clay fractions that include both SOM and mineral phases. The vegetation did not affect the Cu isotope patterns in the vineyard soils. Cu export by runoff from the catchment accounted for 1% of the applied Cu mass from 11th May to 20(th) July 2011, covering most of the Cu use period. 84% of the exported Cu mass was Cu bound to suspended particulate matter (SPM). The runoff displayed δ(65)Cu values from 0.52 to 1.35‰ in the dissolved phase (runoff. Overall, this study shows that Cu stable isotopes may allow identifying the Cu distribution in the soil fractions and their contribution to Cu export in runoff from Cu-contaminated catchments. Copyright © 2016 Elsevier B.V. All rights reserved.

Combined use of stable isotopes and fallout radionuclides as soil erosion indicators in a forested mountain site, South Korea

Energy Technology Data Exchange (ETDEWEB)

Meusburger, K.; Mabit, L.; Alewell, C. [Basel Univ. (Switzerland). Environmental Geosciences; Park, J.H. [Ewha Womans Univ., Seoul (Korea, Republic of). Dept. of Environmental Science and Engineering; Sandor, T. [Central Agricultural Office Food and Feed Safety Directorate (Hungary). Radioanalytical Reference Lab.

2013-07-01

The aim of this study is to assess and to validate the suitability of the stable nitrogen and carbon isotope signature as soil erosion indicators in a mountain forest site in South Korea. Our approach is based on the comparison of the isotope signature of ''stable'' landscape positions (reference sites), which are neither affected by erosion nor deposition, with eroding sites. For undisturbed soils we expect that the enrichment of δ{sup 15}N and δ{sup 13}C with soil depth, due to fractionation during decomposition, goes in parallel with a decrease in nitrogen and carbon content. Soil erosion processes potentially weaken this correlation. The {sup 137}Cs method and the Revised Universal Soil Loss Equation (RUSLE) were applied for the soil erosion quantification. Erosion rates obtained with the {sup 137}Cs method range from 0.9 t ha{sup -1} yr{sup -1} to 7 t ha{sup -1} yr{sup -1}. Considering the steep slopes of up to 40 and the erosive monsoon events (R factor of 6600 MJ mm ha{sup -1} h{sup -1} yr {sup -1}), the rates are plausible and within the magnitude of the RUSLE-modeled soil erosion rates, varying from 0.02 t ha{sup -1} yr{sup -1} to 5.1 t ha{sup -1} yr{sup -1}. The soil profiles of the reference sites showed significant (p < 0.0001) correlations between nitrogen and carbon content and its corresponding δ{sup 15}N and δ{sup 13}C signatures. In contrast, for the eroding sites this relationship was weaker and for the carbon not significant. These results confirm the usefulness of the stable carbon isotope signature as a qualitative indicator for soil disturbance. We could show further that the δ{sup 15}N isotope signature can be used similarly for uncultivated sites. We thus propose that the stable δ{sup 15}N and δ{sup 13}C signature of soil profiles could serve as additional indicators confirming the accurate choice of the reference site in soil erosion studies using the {sup 137}Cs method.

Effect of sustainable land management practices on soil aggregation and stabilization of organic carbon in semiarid mediterranean ecosystems

Science.gov (United States)

Garcia-Franco, Noelia; Albaladejo, Juan; Almagro, María; Wiesmeier, Martin; Martínez-Mena, María

2016-04-01

Arid and semiarid regions represent about 47% of the total land area of the world (UNEP, 1992). At present, there is a priority interest for carbon (C) sequestration in drylands. These areas are considered as very fragile ecosystems with low organic carbon (OC) saturation, and potentially, high capacity for soil OC sequestration. In addition, the restoration of these areas is one of the major challenges for scientists, who will be able to identify and recommended the best land uses and sustainable land management (SLM) practices for soil conservation and mitigation of climate change in these environments. In this regard, in semiarid Mediterranean ecosystems there is an urgent need for the implementation of SLM practices regardless of land-use type (forest, agricultural and shrubland) to maintain acceptable levels of soil organic matter (SOM) and the physico-chemical protection of the OC. Long- and short-term effects of SLM practices on soil aggregation and SOC stabilization were studied in two land uses. The long-term experiment was conducted in a reforestation area with Pinus halepensis Mill., where two afforestation techniques were implemented 20 years ago: a) mechanical terracing with a single application of organic waste of urban soil refuse, and b) mechanical terracing without organic amendment. An adjacent shrubland was considered as the reference plot. The short-term experiment was conducted in a rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard where two SLM practices were introduced 4 years ago: a) reduced tillage plus green manure, and b) no tillage. Reduced tillage was considered as the reference plot given that it is the habitual management practice. Four aggregate size classes were differentiated by sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, different organic C fractions corresponding with active

A comparison of the toluene distillation and vacuum/heat methods for extracting soil water for stable isotopic analysis

Science.gov (United States)

Ingraham, Neil L.; Shadel, Craig

1992-12-01

Hanford Loam, from Richland, Washington, was used as a test soil to determine the precision, accuracy and nature of two methods to extract soil water for stable isotopic analysis: azeotropic distillation using toluene, and simple heating under vacuum. The soil was oven dried, rehydrated with water of known stable isotopic compositions, and the introduced water was then extracted. Compared with the introduced water, initial aliquots of evolved water taken during a toluene extraction were as much as 30 ‰ more depleted in D and 2.7 ‰ more depleted in 18O, whereas final aliquots were as much as 40 ‰ more enriched in D and 14.3 ‰ more enriched in 18O. Initial aliquots collected during the vacuum/heat extraction were as much as 64 ‰ more depleted in D and 8.4 ‰ more depleted in 18O than was the introduced water, whereas the final aliquots were as much as 139 ‰ more enriched in D, and 20.8 ‰ more enriched in 18O. Neither method appears quantitative; however, the difference in stable isotopic composition between the first and last aliquots of water extracted by the toluene method is less than that from the vacuum/heat method. This is attributed to the smaller fractionation factors involved with the higher average temperatures of distillation of the toluene. The average stable isotopic compositions of the extracted water varied from that of the introduced water by up to 1.4 ‰ in δD and 4.2 ‰ in δ18O with the toluene method, and by 11.0 ‰ in δD and 1.8 ‰ in δ18O for the vacuum/heat method. The lack of accuracy of the extraction methods is thought to be due to isotopic fractionation associated with water being weakly bound (not released below 110°C) in the soil. The isotopic effect of this heat-labile water is larger at low water contents (3.6 and 5.2% water by weight) as the water bound in the soil is a commensurately larger fraction of the total. With larger soilwater contents the small volume of water bound with an associated fractionation is

No influence of CO2 on stable isotope analyses of soil waters with off-axis integrated cavity output spectroscopy (OA-ICOS).

Science.gov (United States)

Sprenger, Matthias; Tetzlaff, Doerthe; Soulsby, Chris

2017-03-15

It was recently shown that the presence of CO 2 affects the stable isotope (δ 2 H and δ 18 O values) analysis of water vapor via Wavelength-Scanned Cavity Ring-Down Spectroscopy. Here, we test how much CO 2 is emitted from soil samples and if the CO 2 in the headspace influences the isotope analysis with the direct equilibration method by Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS). The headspace above different amounts of sparkling water was sampled, and its stable isotopic composition (δ 2 H and δ 18 O values) and CO 2 concentration were measured by direct equilibration and by gas chromatography, respectively. In addition, the headspace above soil samples was analyzed in the same way. Furthermore, the gravimetric water content and the loss on ignition were measured for the soil samples. The experiment with the sparkling water showed that CO 2 does not influence the stable isotope analysis by OA-ICOS. CO 2 was emitted from the soil samples and correlated with the isotopic fractionation signal, but no causal relationship between the two was determined. Instead, the fractionation signal in pore water isotopes can be explained by soil evaporation and the CO 2 can be related to soil moisture and organic matter which both enhance microbial activity. We found, despite the high CO 2 emissions from soil samples, no need for a post-correction of the pore water stable isotope analysis results, since there is no relation between CO 2 concentrations and the stable isotope results of vapor samples obtained with OA-ICOS. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd.

Quantification of the proliferation of arbuscular mycorrhizal fungi in soil

Science.gov (United States)

Zhang, Ning; Lilje, Osu; McGee, Peter

2013-04-01

Good soil structure is important for sustaining agricultural production and preserving functions of the soil ecosystem. Soil aggregation is a critically important component of soil structure. Stable aggregates enable water infiltration, gas exchange for biological activities of plant roots and microorganisms, living space and surfaces for soil microbes, and contribute to stabilization of organic matter and storage of organic carbon (OC) in soil. Soil aggregation involves fine roots, organic matter and hyphae of arbuscular mycorrhizal (AM) fungi. Hyphal proliferation is essential for soil aggregation and sequestration of OC in soil. We do not yet have a mechanism to directly quantify the density of hyphae in soil. Organic materials and available phosphorus are two of the major factors that influence fungi in soil. Organic materials are a source of energy for saprotrophic microbes. Fungal hyphae increase in the presence of organic matter. Phosphorus is an important element usually found in ecosystems. The low availability of phosphorus limits the biological activity of microbes. AM fungi benefit plants by delivering phosphorus to the root system. However, the density and the length of hyphae of AM fungi do not appear to be influenced by available phosphorus. A number of indirect methods have been used to visualize distribution of fungi in soil. Reliable analyses of soil are limited because of soil characteristics. Soils are fragile, and fragility limits opportunity for non-destructive analysis. The soil ecosystem is complex. Soil particles are dense and the density obscures the visualization of fungal hyphae. Fungal hyphae are relatively fine and information at the small scale (hyphae of AM fungi. Hyphae were quantified in an artificial soil matrix using micro-computer aided tomography. Micro-computer aided tomography provides three dimensional images of hyphal ramification through electron lucent materials and enables the visualization and quantification of hyphae

Elevated CO2 and Tree Species Affect Microbial  Activity and Associated Aggregate Stability in Soil  Amended with Litter

Directory of Open Access Journals (Sweden)

Salwan M. J. Al‐Maliki

2017-03-01

Full Text Available (1 Elevated atmospheric CO2 (eCO2 may affect organic inputs to woodland soils with potential consequences for C dynamics and associated aggregation; (2 The Bangor Free Air Concentration Enrichment experiment compared ambient (330 ppmv and elevated (550 ppmv CO2 regimes over four growing seasons (2005–2008 under Alnus glutinosa, Betula pendula and Fagus sylvatica. Litter from the experiment (autumn 2008 and Lumbricus terrestris were added to mesocosm soils. Microbial properties and aggregate stability were investigated in soil and earthworm casts. Soils taken from the field experiment in spring 2009 were also investigated; (3 eCO2 litter had lower N and higher C:N ratios. F. sylvatica and B. pendula litter had lower N and P than A. glutinosa; F. sylvatica had higher cellulose. In mesocosms, eCO2 litter decreased respiration, mineralization constant (respired C:total organic C and soluble carbon in soil but not earthworm casts; microbial‐C and fungal hyphal length differed by species (A. glutinosa = B. pendula > F. sylvatica not CO2 regime. eCO2 increased respiration in field aggregates but increased stability only under F. sylvatica; (4 Lower litter quality under eCO2 may restrict its initial decomposition, affecting C stabilization in aggregates. Later resistant materials may support microbial activity and increase aggregate stability. In woodland, C and soil aggregation dynamics may alter under eCO2, but outcomes may be influenced by tree species and earthworm activity.

Sensitivity of soil carbon fractions and their specific stabilization mechanisms to extreme soil warming in a subarctic grassland.

Science.gov (United States)

Poeplau, Christopher; Kätterer, Thomas; Leblans, Niki I W; Sigurdsson, Bjarni D

2017-03-01

Terrestrial carbon cycle feedbacks to global warming are major uncertainties in climate models. For in-depth understanding of changes in soil organic carbon (SOC) after soil warming, long-term responses of SOC stabilization mechanisms such as aggregation, organo-mineral interactions and chemical recalcitrance need to be addressed. This study investigated the effect of 6 years of geothermal soil warming on different SOC fractions in an unmanaged grassland in Iceland. Along an extreme warming gradient of +0 to ~+40 °C, we isolated five fractions of SOC that varied conceptually in turnover rate from active to passive in the following order: particulate organic matter (POM), dissolved organic carbon (DOC), SOC in sand and stable aggregates (SA), SOC in silt and clay (SC-rSOC) and resistant SOC (rSOC). Soil warming of 0.6 °C increased bulk SOC by 22 ± 43% (0-10 cm soil layer) and 27 ± 54% (20-30 cm), while further warming led to exponential SOC depletion of up to 79 ± 14% (0-10 cm) and 74 ± 8% (20-30) in the most warmed plots (~+40 °C). Only the SA fraction was more sensitive than the bulk soil, with 93 ± 6% (0-10 cm) and 86 ± 13% (20-30 cm) SOC losses and the highest relative enrichment in 13 C as an indicator for the degree of decomposition (+1.6 ± 1.5‰ in 0-10 cm and +1.3 ± 0.8‰ in 20-30 cm). The SA fraction mass also declined along the warming gradient, while the SC fraction mass increased. This was explained by deactivation of aggregate-binding mechanisms. There was no difference between the responses of SC-rSOC (slow-cycling) and rSOC (passive) to warming, and 13 C enrichment in rSOC was equal to that in bulk soil. We concluded that the sensitivity of SOC to warming was not a function of age or chemical recalcitrance, but triggered by changes in biophysical stabilization mechanisms, such as aggregation. © 2016 John Wiley & Sons Ltd.

Effect of biochar on reclaimed tidal land soil properties and maize (Zea mays L.) response.

Science.gov (United States)

Kim, Hyuck-Soo; Kim, Kwon-Rae; Yang, Jae E; Ok, Yong Sik; Owens, Gary; Nehls, Thomas; Wessolek, Gerd; Kim, Kye-Hoon

2016-01-01

Reclaimed tidal land soil (RTLS) often contains high levels of soluble salts and exchangeable Na that can adversely affect plant growth. The current study examined the effect of biochar on the physicochemical properties of RTLS and subsequently the influence on plant growth performance. Rice hull derived biochar (BC) was applied to RTLS at three different rates (1%, 2%, and 5% (w/w)) and maize (Zea mays L.) subsequently cultivated for 6weeks. While maize was cultivated, 0.1% NaCl solution was supplied from the bottom of the pots to simulate the natural RTLS conditions. Biochar induced changes in soil properties were evaluated by the water stable aggregate (WSA) percentage, exchangeable sodium percentage (ESP), soil organic carbon contents, cation exchange capacity, and exchangeable cations. Plant response was measured by growth rate, nutrient contents, and antioxidant enzyme activity of ascorbate peroxidase (APX) and glutathione reductase (GR). Application of rice hull derived biochar increased the soil organic carbon content and the percentage of WSA by 36-69%, while decreasing the ESP. The highest dry weight maize yield was observed from soil which received 5% BC (w/w), which was attributed to increased stability of water-stable aggregates and elevated levels of phosphate in BC incorporated soils. Moreover, increased potassium, sourced from the BC, induced mitigation of Na uptake by maize and consequently, reduced the impact of salt stress as evidenced by overall declines in the antioxidant activities of APX and GR. Copyright © 2015 Elsevier Ltd. All rights reserved.

Changes on aggregation in mine waste amended with biochar and marble mud

Science.gov (United States)

Ángeles Muñoz, María; Guzmán, Jose; Zornoza, Raúl; Moreno-Barriga, Fabián; Faz, Ángel; Lal, Rattan

2016-04-01

Mining activities have produced large amounts of wastes over centuries accumulated in tailing ponds in Southeast Spain. Applications of biochar may have a high potential for reclamation of degraded soils. Distribution, size and stability of aggregates are important indices of soil physical quality. However, research data on aggregation processes at amended mining tailings with biochar are scanty. Therefore, the aim of this study was to determine the effects of seven different treatments involving biochar and marble mud (MM) on the aggregation in mine waste (MW). Seven different treatments were tested after 90 days of incubation in the laboratory. These treatments were the mix of MW and: biochar from solid pig manure (PM), biochar from cotton crop residues (CR), biochar from municipal solid waste (MSW), marble mud (MM), PM+MM, CR+MM, MSW+MM and control without amendment. High sand percentages were identified in the MW. The biochars made from wastes (PM, CR, MSW) were obtained through pyrolysis of feedstocks. The water stability of soil aggregates was studied. The data on total aggregation were corrected for the primary particles considering the sandy texture of the MW. Moreover, partial aggregation was determined for each fraction and the mean weight diameter (MWD) of aggregates was computed. Soil bulk density and total porosity were also determined. No significant differences were observed in total aggregation and MWD among treatments including the control. For the size range of >4.75 mm, there were significant differences in aggregates > 4.75 mm between CR+MM in comparison with that for CT. There were also significant differences between MSW and PM+MM for the 1-0.425 mm fraction, and between CT and MM and CR for 0.425-0.162 mm aggregate size fractions. Therefore, CR-derived biochar applied with MM enhanced stability of macro-aggregates. Furthermore, soil bulk density was also the lowest bulk density and total porosity the highest for the CR-derived biochar

[Effects of different tillage patterns on soil properties, maize yield and water use efficiency in Weibei Highland, China.

Science.gov (United States)

Liu, Dan; Zhang, Xia; Li, Jun; Wang, Xu-Dong

2018-02-01

An eight-year field experiment of straw returning was conducted on dark loessial soil in Weibei Highland to investigate the effects of tillage patterns on soil aggregate, soil organic carbon (SOC), corn yield and soil water use efficiency (WUE). There were six tillage patterns, including conventional tillage (CT/CT), no-tillage (NT/NT), subsoiling tillage (ST/ST), no-tillage/subsoiling tillage (NT/ST), conventional tillage/no-tillage (CT/NT) and conventional tillage/subsoiling tillage (CT/ST). The results showed that compared with CT/CT, the patterns of NT/NT, ST/ST and the rotational tillage patterns (NT/ST, CT/NT and CT/ST) decreased the mean mass diameter of soil mechanical stable aggregate. The patterns of NT/NT, ST/ST and NT/ST increased the content of soil water-stable aggregate with the particle size >0.25 mm (WR 0.25 ) and their mean mass diameter, especially in the depth of 20-50 cm. These patterns reduced the proportion of aggregate destruction (PAD). Compared with CT/CT, the patterns of NT/ST, CT/NT, NT/NT and ST/ST increased the content of SOC in 0-10 cm soil layer. The content of SOC decreased as the increases of soil depth for all tillage patterns, but the decrease in SOC of three single tillage patterns (ST/ST, NT/NT and CT/CT) was larger than that of three rotational tillage patterns. Compared with CT/CT, the other five tillage patterns increased soil water storage in 0-200 cm soil profile, crop yield and WUE in maize. The yield and WUE in NT/ST pattern were significantly increased by 15.1% and 27.5%, respectively. Both corn yield and WUE were significantly and positively correlated with soil water storage in 0-200 cm soil profile in field during the cropping and fallow periods. Moreover, soil water storage during the cropping period was positively correlated with WR 0.25 , but negatively correlated with PAD in 0-50 cm soil layer. Particularly, maize yield, WUE and soil water storage during the cropping period were closely related to WR 0.25 in 20

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

Disruption of soil aggregates by varied amounts of ultrasonic energy in fractionation of organic matter of a clay latosol : carbon, nitrogen and 13C distribution in particle-size fractions

NARCIS (Netherlands)

Roscoe, R.; Buurman, P.; Velthorst, E.J.

2000-01-01

Ultrasonic energy has been widely used to disrupt soil aggregates before fractionating soil physically when studying soil organic matter (SOM). Nevertheless, there is no consensus about the optimum energy desirable to disrupt the soil. We therefore aimed (i) to quantify the effect of varied

REGULATION OF deflationary stability OF Polissya agrolandscapes soil cover

Directory of Open Access Journals (Sweden)

Barvinskyi A.V.

2017-08-01

granulometric and mikroagregative analysis by methodology of B.A.Nikitin shows that aggregation of large particles in the test soil occurs solely at the expense of sludge.In particular the use of mineral and organic fertilizer sludge fraction in the formation of a macrostructure does not participate (relative rate of participation of fines in the formation of macrostructure is 0. When combined fertilizer, the figure is 0,24-0,30 on unlimestoneareas and 0,30-0,48 on limestone plots. The process of aggregation in sod-podzolic sandy-loamy soil uneven: more (65-100% in the intermediate fractions (0,25-0,001 mm than in coarse (1-0,25 mm. When combined lime and fertilizer alignment occurs of aggregation process.Application of CaCO3 at a dose of 1,5, calculated by hydrolytic acidity, together with organic-mineral system of crops fertilizer allows to 47,7% transfer this process in macroaggregates. As a result - increase of deflationary stable aggregates contents (diameter greater than 1 mm to 58%.

Soil aggregation under different management systems Agregação de solo com diferentes manejos

Directory of Open Access Journals (Sweden)

Cibele Mascioli Rebello Portella

2012-12-01

Full Text Available Considering that the soil aggregation reflects the interaction of chemical, physical and biological soil factors, the aim of this study was evaluate alterations in aggregation, in an Oxisol under no-tillage (NT and conventional tillage (CT, since over 20 years, using as reference a native forest soil in natural state. After analysis of the soil profile (cultural profile in areas under forest management, samples were collected from the layers 0-5, 5-10, 10-20 and 20-40 cm, with six repetitions. These samples were analyzed for the aggregate stability index (ASI, mean weighted diameter (MWD, mean geometric diameter (MGD in the classes > 8, 8-4, 4-2, 2-1, 1-0.5, 0.5-0.25, and Considerando que a agregação reflete na interação dos fatores químicos, físicos e biológicos dos solos, o objetivo deste trabalho foi avaliar a agregação de um Latossolo Vermelho distroférrico sob plantio direto (PD e preparo convencional (PC implantado há mais de 20 anos, utilizando-se como referência do estado natural uma mata nativa (M. Após análise do perfil de solo pelo método do perfil cultural nas áreas sob manejo e mata, foram coletadas amostras nas profundidades de 0-5, 5-10, 10-20 e 20-40 cm de profundidade, com seis repetições. A partir dessas amostras, foram determinados o índice de estabilidade dos agregados (IEA, o diâmetro médio ponderado (DMP, o diâmetro médio geométrico (DMG e as classes de diâmetro >8, 8-4, 4-2, 2-1, 1-0,5, 0,5-0,25 e < 0,25 mm, além das determinações físicas (granulometria, argila dispersa em água - AD, índice de floculação - IF e densidade do solo - Ds e químicas (carbono orgânico total - COT, nitrogênio total - N, cálcio trocável - Ca2+ e pH. Os resultados indicaram que o aumento da mobilização do solo (M < PD < PC resultou em diminuição da sua estabilidade, medida por meio de todos os indicadores de estabilidade analisados: DMP, DMG, IEA, distribuição de classes de agregados, AD e IF, concluindo

ORGANIC MATTER AND AGGREGATION OF A PLANOSOL UNDER DIFFERENT FOREST COVERINGS

Directory of Open Access Journals (Sweden)

Julia Kishida Bochner

2008-03-01

Full Text Available The litter quality can alter soil aggregation, modifying the transformation dynamics and allocation of soil carbon (Cin different compartments. This study evaluated the aggregate stability and its relation with litter chemical characteristics, organiccarbon and free light fraction (FLL from the organic matter under three different types of vegetation covering: secondary forest (FSand plantings of Mimosa Caesalpiniaefolia (PM and Carapa guianenses (PA with subsequently natural regeneration. Litter sampleswere characterized using polyfenols, lignin, suberine, tannin and holocelulose content and C/N relationship. Soil samples werecollected in two depths (0-10 and 10-20 cm and soil aggregation were estimate using mean weight diameter (DMP, mean geometricdiameter (DMG and index of aggregate stability (IEA analysis . Soil samples in the same depths were also characterized using C andFLL content. The highest suberine and polyfenols content of the litter found in the areas FS and PM reduced the speed of residuesdecomposition in the soil causing larger FLL content in both coverings. Those compositions contributed to the stabilization of C in themineral phase, because the highest C content was found in those areas. This fact is confirmed by the values of DMP, DMG and IEAamong the areas. They are higher in the coverings, PM and FS. It can be concluded that the polyfenols and suberine content weredecisive in the subdivision of C and in the aggregation of the soil in the areas of FS and PM.

Effects of plastic mulches and high tunnel raspberry production systems on soil physicochemical quality indicators

Science.gov (United States)

Domagała-Świątkiewicz, Iwona; Siwek, Piotr

2018-01-01

In horticulture, degradable materials are desirable alternatives to plastic films. Our aim was to study the impact of soil plastic mulching on the soil properties in the high tunnel and open field production systems of raspberry. The raised beds were mulched with a polypropylene non-woven and two degradable mulches: polypropylene with a photodegradant and non-woven polylactide. The results indicated that the system of raspberry production, as well as the type of mulching had significant impact on soil organic carbon stock, moisture content and water stable aggregate amount. Soils taken from the open field system had a lower bulk density and water stability aggregation index, but higher organic carbon and capillary water content as compared to soils collected from high tunnel conditions. In comparison with the open field system, soil salinity was also found to be higher in high tunnel, as well as with higher P, Mg, Ca, S, Na and B content. Furthermore, mulch covered soils had more organic carbon amount than the bare soils. Soil mulching also enhanced the water capacity expressed as a volume of capillary water content. In addition, mulching improved the soil structure in relation to the bare soil, in particular, in open field conditions. The impact of the compared mulches on soil quality indicators was similar.

Effect of soil moisture and treatment volume on bentazone mobility in soil

OpenAIRE

Guimont, Sophie; Perrin-Ganier, Corinne; Real, Benoit; Schiavon, Michel

2005-01-01

Soil moisture affects the leaching behaviour of pesticides by inducing their physical entrapment in the soil structure. Columns containing soil aggregates were dampened to specific initial moisture levels. Bentazon was dripped onto surface aggregates in different volumes. The columns were then percolated after an equilibration period. Soil water from the columns was divided arbitrarily among mobile and immobile regions in order to describe the herbicide redistribution processes in the soil. W...

Improving soil enzyme activities and related quality properties of reclaimed soil by applying weathered coal in opencast-mining areas of the Chinese loess plateau

Energy Technology Data Exchange (ETDEWEB)

Li, Hua [College of Environment and Resources, Shanxi University, Taiyuan (China); CAS/Shandong Provincial Key Laboratory of Coastal Environmental Process, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Yantai (China); Shao, Hongbo [CAS/Shandong Provincial Key Laboratory of Coastal Environmental Process, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Yantai (China); Institute for Life Sciences, Qingdao University of Science and Technology (QUST), Qingdao (China); Li, Weixiang; Bi, Rutian [Shanxi Agricultural University, Taigu (China); Bai, Zhongke [Department of Land Science Technology, University of Geosciences, Beijing (China)

2012-03-15

There are many problems for the reclaimed soil in opencast-mining areas of the Loess Plateau of China such as poor soil structure and extreme poverty in soil nutrients and so on. For the sake of finding a better way to improve soil quality, the current study was to apply the weathered coal for repairing soil media and investigate the physicochemical properties of the reclaimed soil and the changes in enzyme activities after planting Robinia pseucdoacacia. The results showed that the application of the weathered coal significantly improved the quality of soil aggregates, increased the content of water stable aggregates, and the organic matter, humus, and the cation exchange capacity of topsoil were significantly improved, but it did not have a significant effect on soil pH. Planting R. pseucdoacacia significantly enhanced the activities of soil catalase, urease, and invertase, but the application of the weathered coal inhibited the activity of catalase. Although the application of appropriate weathered coal was able to significantly increase urease activity, the activities of catalase, urease, or invertase had a close link with the soil profile levels and time. This study suggests that applying weathered coals could improve the physicochemical properties and soil enzyme activities of the reclaimed soil in opencast-mining areas of the Loess Plateau of China and the optimum applied amount of the weathered coal for reclaimed soil remediation is about 27 000 kg hm{sup -2}. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Variabilidade espacial da agregação do solo avaliada pela geometria fractal e geoestatística Spatial variability of soil aggregation evaluated by fractal geometry and geostatistics

Directory of Open Access Journals (Sweden)

J. R. P. Carvalho

2004-02-01

Full Text Available Este trabalho teve por objetivo explorar a aplicabilidade da teoria de fractais no estudo da variabilidade espacial em agregação de solo. A geometria de fractais tem sido proposta como um modelo para a distribuição de tamanho de partículas. A distribuição do tamanho de agregados do solo, expressos em termos de massa, é apresentada. Os parâmetros do modelo, tais como: a dimensão fractal D, medida representativa da fragmentação do solo (quanto maior seu valor, maior a fragmentação, e o tamanho do maior agregado R L foram definidos como ferramentas descritivas para a agregação do solo. Os agregados foram coletados em uma profundidade de 0-10 cm de um Latossolo Vermelho distrófico típico álico textura argilosa, em Angatuba, São Paulo. Uma grade regular de 100 x 100 m foi usada e a amostragem realizada em 76 pontos nos quais se determinou a distribuição de agregados por via úmida, usando água, álcool e benzeno como pré-tratamentos. Pelo exame de semivariogramas, constatou-se a ocorrência de dependência espacial. A krigagem ordinária foi usada como interpolador e mapas de contorno mostraram-se de grande utilidade na descrição da variabilidade espacial de agregação do solo.This work explored the applicability of the fractal theory for studies into space variability of soil aggregation. Fractal geometry has become a model for soil size particle distribution. The distribution of soil aggregates in terms of its mass was obtained, and model parameters such as the fractal dimension D, which is a representative measure of the soil fragmentation (the larger its value, the larger the fragmentation, and the largest aggregate size R L were defined as descriptive tools for soil aggregation. The aggregates were collected at a depth of 0-10 cm of a Clayey Ferrasol in Angatuba, São Paulo. A regular grid of 100 x 100 m was used and samples collected from 76 points, where the aggregate distribution was determined by humid way (water

In-situ studies of microbial CH4 oxidation efficiency in Arctic wetland soils. Applications of stable carbon isotopes

International Nuclear Information System (INIS)

Preuss, Inken-Marie

2013-01-01

Arctic wetland soils are significant sources of the climate-relevant trace gas methane (CH 4 ). The observed accelerated warming of the Arctic is expected to cause deeper permafrost thawing followed by increased carbon mineralization and CH 4 formation in water-saturated permafrost-affected tundra soils thus creating a positive feedback to climate change. Aerobic CH 4 oxidation is regarded as the key process reducing CH 4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. This study improved the in-situ quantification of microbial CH 4 oxidation efficiency in arctic wetland soils in Russia's Lena River Delta based on stable isotope signatures of CH 4 . In addition to the common practice of determining the stable isotope fractionation during oxidation, additionally the fractionation effect of diffusion, an important gas transport mechanism in tundra soils, was investigated for both saturated and unsaturated conditions. The isotopic fractionation factors α ox and α diff were used to calculate the CH 4 oxidation efficiency from the CH 4 stable isotope signatures of wet polygonal tundra soils of different hydrology. Further, the method was used to study the short-term effects of temperature increase with a climate manipulation experiment. For the first time, the stable isotope fractionation of CH 4 diffusion through water-saturated soils was determined with α diff = 1.001 ± 0.0002 (n = 3). CH 4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was α diff = 1.013 ± 0.003 (n = 18). For the studied sites the fractionation factor for diffusion under saturated conditions α diff = 1.001 seems to be of utmost importance for the quantification of the CH 4 oxidation efficiency, since most of the CH 4 is oxidized in the saturated part at the aerobic-anaerobic interface. Furthermore, it was found that α ox differs widely between sites and horizons (mean α ox = 1

High-resolution stable isotope monitoring reveals differential vegetation-soil water feedbacks among plant functional types

Science.gov (United States)

Volkmann, T. H. M.; Haberer, K.; Troch, P. A. A.; Gessler, A.; Weiler, M.

2016-12-01

Understanding the linked dynamics of rain water recharge to soils and its utilization by plants is critical for predicting the impact of climate and land use changes on the productivity of ecosystems and the hydrologic cycle. While plants require vast quantities of water from the soil to sustain growth and function, they exert important direct and indirect controls on the movement of water through the rooted soil horizons, thereby potentially affecting their own resource availability. However, the specific ecohydrological belowground processes associated with different plant types and their rooting systems have been difficult to quantify with traditional methods. Here, we report on the use of techniques for monitoring stable isotopes in soil and plant water pools that allow us to track water infiltration and root uptake dynamics non-destructively and in high resolution. The techniques were applied in controlled rain pulse experiments with distinct plant types (grass, deciduous trees, grapevine) that we let develop on an initially uniform soil for two years. Our results show that plant species and types differed widely in their plasticity and pattern of root uptake under variable water availability. Thereby, and through notably co-acting indirect effects related to differential root system traits and co-evolution of soil properties, the different plants induced contrasting hydrological dynamics in the soil they had inhabited for only a short period of time. Taken together, our data suggest that the studied soil-vegetation systems evolved a positive infiltration-uptake feedback in which hydrological flow pathways underlying different species diverged in a way that complemented their specific water utilization strategy. Such a feedback could present an indirect competitive mechanism by which plants improve their own water supply and modulate hydrological cycling at the land surface. The ability to directly measure this feedback using in situ isotope methodology

Hot regions of labile and stable soil organic carbon in Germany - Spatial variability and driving factors

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Vos, Cora; Jaconi, Angélica; Jacobs, Anna; Don, Axel

2018-06-01

Atmospheric carbon dioxide levels can be mitigated by sequestering carbon in the soil. Sequestration can be facilitated by agricultural management, but its influence is not the same on all soil carbon pools, as labile pools with a high turnover may be accumulated much faster but are also more vulnerable to losses. The aims of this study were to (1) assess how soil organic carbon (SOC) is distributed among SOC fractions on a national scale in Germany, (2) identify factors influencing this distribution and (3) identify regions with high vulnerability to SOC losses. The SOC content and proportion of two different SOC fractions were estimated for more than 2500 mineral topsoils (soil texture, bulk soil C / N ratio, total SOC content and pH. For some regions, the drivers were linked to the land-use history of the sites. Arable topsoils in central and southern Germany were found to contain the highest proportions and contents of stable SOC fractions, and therefore have the lowest vulnerability to SOC losses. North-western Germany contains an area of sandy soils with unusually high SOC contents and high proportions of light SOC fractions, which are commonly regarded as representing a labile carbon pool. This is true for the former peat soils in this area, which have already lost and are at high risk of losing high proportions of their SOC stocks. Those black sands can, however, also contain high amounts of stable SOC due to former heathland vegetation and need to be treated and discussed separately from non-black sand agricultural soils. Overall, it was estimated that, in large areas all over Germany, over 30 % of SOC is stored in easily mineralisable forms. Thus, SOC-conserving management of arable soils in these regions is of great importance.

Leaching characteristics of EDTA-enhanced phytoextraction of Cd and Pb by Zea mays L. in different particle-size fractions of soil aggregates exposed to artificial rain.

Science.gov (United States)

Lu, Yayin; Luo, Dinggui; Lai, An; Liu, Guowei; Liu, Lirong; Long, Jianyou; Zhang, Hongguo; Chen, Yongheng

2017-01-01

Chelator-assisted phytoextraction is an alternative and effective technique for the remediation of heavy metal-contaminated soils, but the potential for heavy metal leaching needs to be assessed. In the present study, a soil column cultivation-leaching experiment was conducted to investigate the Cd and Pb leaching characteristics during assisted phytoextraction of metal-contaminated soils containing different particle-size soil aggregates. The columns were planted with Zea mays "Zhengdan 958" seedlings and treated with combined applications of EDTA and simulated rainfall (pH 4.5 or 6.5). The results were as follows: (1) The greatest uptake of Cd and Pb by Z. mays was observed after treatment with EDTA (2.5 mmol kg -1 soil) and soil aggregates of  EDTA 2.5-1 (pH 6.5) > EDTA 2.5-2 (pH 4.5) > EDTA 2.5-4 (pH 4.5) > EDTA 2.5-2 (pH 6.5) > EDTA 2.5-4 (pH 6.5).

Nickel aggregates produced by radiolysis

International Nuclear Information System (INIS)

Marignier, J.L.; Belloni, J.

1988-01-01

Nickel aggregates with subcolloidal size and stable in water have been synthesized by inhibiting the corrosion by the medium. The protective effect of the surfactant is discussed in relation with the characteristics of various types of polyvinyl alcohol studied. The reactivity of aggregates towards oxidizing compounds, nitro blue tetrazolium, methylene blue, silver ions, oxygen, methylviologen, enables an estimation of the redox potential of nickel aggregates (E = - 04 ± 0.05 V). It has been applied to quantitative analysis of the particles in presence of nickel ions. 55 refs [fr

Influence of forest disturbance on stable nitrogen isotope ratios in soil and vegetation profiles

Science.gov (United States)

Jennifer D. Knoepp; Scott R. Taylor; Lindsay R. Boring; Chelcy F. Miniat

2015-01-01

Soil and plant stable nitrogen isotope ratios (15 N) are influenced by atmospheric nitrogen (N) inputs and processes that regulate organic matter (OM) transformation and N cycling. The resulting 15N patterns may be useful for discerning ecosystem differences in N cycling. We studied two ecosystems; longleaf pine wiregrass (...

Trophic position of soil nematodes in boreal forests as indicated by stable isotope analysis

Science.gov (United States)

Kudrin, Alexey; Tsurikov, Sergey

2016-04-01

Despite the well-developed trophic classification of soil nematodes, their position in soil food webs is still little understood. Observed deviations from the typical feeding strategy indicate that a simplified trophic classification probably does not fully reflect actual trophic interactions. Furthermore, the extent and functional significance of nematodes as prey for other soil animals remains unknown. Stable isotope analysis (SIA) is powerful tool for investigating the structure of soil food webs, but its application to the study of soil nematodes has been limited to only a few studies. We used stable isotope analysis to gain a better understanding of trophic links of several groups of soil nematodes in two boreal forests on albeluvisol. We investigated four taxonomic groups of nematodes: Mononchida, Dorylaimida, Plectidae and Tylenchidae (mostly from the genus Filenchus), that according to the conventional trophic classification represent predators, omnivores, bacterivores and root-fungal feeders, respectively. To assess the trophic position of nematodes, we used a comparison against a set of reference species including herbivorous, saprophagous and predatory macro-invertebrates, oribatid and mesostigmatid mites, and collembolans. Our results suggest that trophic position of the investigated groups of soil nematodes generally corresponds to the conventional classification. All nematodes were enriched in 13C relative to Picea abies roots and litter, and mycorrhizal fungal mycelium. Root-fungal feeders Tylenchidae had δ15N values similar to those of earthworms, enchytraeids and Entomobrya collembolans, but slightly lower δ13C values. Bacterivorous Plectidae were either equal or enriched in 15N compared with saprophagous macroinvertebrates and most mesofauna species. Omnivorous Dorylaimida and predatory Mononchida were further enriched in 15N and their isotopic signature was similar to that of predatory arthropods. These data confirm a clear separation of

Influence of Robinia pseudoacacia short rotation coppice on soil physical properties

Science.gov (United States)

Xavier, Morvan; Isabelle, Bertrand; Gwenaelle, Gibaud

2015-04-01

stability measurements showed that the SRC soil had the most stable aggregates compared to the other land uses. SRC also had the highest infiltration rates (656 mm.h-1) compared to NF (54 mm.h-1), GL (23 mm.h-1) and AL (8 mm.h-1). Analyses and explanation of these results are still under progress and will be presented in congress. Kodesova, R., Jirku, V., Kodes, V., Muhlhanselova, M., Nikodem, A., Žigová, A., 2011. Soil structure and soil hydraulic properties of Haplic Luvisol used as arable land and grassland. Soil and Tillage Research 111 (2), pp. 154-161. Le Bissonnais Y., 1996. Aggregate stability and assessment of soil crustability and erodibility: I theory and methodology. European Journal of Soil Science 47, 425-437.

Tracing anthropogenic thallium in soil using stable isotope compositions.

Science.gov (United States)

Kersten, Michael; Xiao, Tangfu; Kreissig, Katharina; Brett, Alex; Coles, Barry J; Rehkämper, Mark

2014-08-19

Thallium stable isotope data are used in this study, for the first time, to apportion Tl contamination in soils. In the late 1970s, a cement plant near Lengerich, Germany, emitted cement kiln dust (CKD) with high Tl contents, due to cocombustion of Tl-enriched pyrite roasting waste. Locally contaminated soil profiles were obtained down to 1 m depth and the samples are in accord with a binary mixing relationship in a diagram of Tl isotope compositions (expressed as ε(205)Tl, the deviation of the (205)Tl/(203)Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 10(4)) versus 1/[Tl]. The inferred mixing endmembers are the geogenic background, as defined by isotopically light soils at depth (ε(205)Tl ≈ -4), and the Tl emissions, which produce Tl-enriched topsoils with ε(205)Tl as high as ±0. The latter interpretation is supported by analyses of the CKD, which is also characterized by ε(205)Tl ≈ ± 0, and the same ε(205)Tl value was found for a pyrite from the deposit that produced the cocombusted pyrite roasting waste. Additional measurements for samples from a locality in China, with outcrops of Tl sulfide mineralization and associated high natural Tl backgrounds, reveal significant isotope fractionation between soils (ε(205)Tl ≈ +0.4) and locally grown green cabbage (ε(205)Tl between -2.5 and -5.4). This demonstrates that biological isotope fractionation cannot explain the isotopically heavy Tl in the Lengerich topsoils and the latter are therefore clearly due to anthropogenic Tl emissions from cement processing. Our results thus establish that isotopic data can reinforce receptor modeling for the toxic trace metal Tl.

Stable isotope analysis (δ (13)C and δ (15)N) of soil nematodes from four feeding groups.

Science.gov (United States)

Melody, Carol; Griffiths, Bryan; Dyckmans, Jens; Schmidt, Olaf

2016-01-01

Soil nematode feeding groups are a long-established trophic categorisation largely based on morphology and are used in ecological indices to monitor and analyse the biological state of soils. Stable isotope ratio analysis ((13)C/(12)C and (15)N/(14)N, expressed as δ (13)C and δ (15)N) has provided verification of, and novel insights into, the feeding ecology of soil animals such as earthworms and mites. However, isotopic studies of soil nematodes have been limited to date as conventional stable isotope ratio analysis needs impractically large numbers of nematodes (up to 1,000) to achieve required minimum sample weights (typically >100 µg C and N). Here, micro-sample near-conventional elemental analysis-isotopic ratio mass spectrometry (μEA-IRMS) of C and N using microgram samples (typically 20 µg dry weight), was employed to compare the trophic position of selected soil nematode taxa from four feeding groups: predators (Anatonchus and Mononchus), bacterial feeders (Plectus and Rhabditis), omnivores (Aporcelaimidae and Qudsianematidae) and plant feeder (Rotylenchus). Free-living nematodes were collected from conventionally and organically managed arable soils. As few as 15 nematodes, for omnivores and predators, were sufficient to reach the 20 µg dry weight target. There was no significant difference in δ (15)N (p = 0.290) or δ (13)C (p = 0.706) between conventional and organic agronomic treatments but, within treatments, there was a significant difference in N and C stable isotope ratios between the plant feeder, Rotylenchus (δ (15)N = 1.08 to 3.22 mUr‰, δ (13)C = -29.58 to -27.87 mUr) and all other groups. There was an average difference of 9.62 mUr in δ (15)N between the plant feeder and the predator group (δ (15)N = 9.89 to 12.79 mUr, δ (13)C = -27.04 to -25.51 mUr). Isotopic niche widths were calculated as Bayesian derived standard ellipse areas and were smallest for the plant feeder (1.37 mUr(2)) and the predators (1.73 mUr(2)), but largest for

Stable isotope analysis (δ13C and δ15N of soil nematodes from four feeding groups

Directory of Open Access Journals (Sweden)

Carol Melody

2016-09-01

Full Text Available Soil nematode feeding groups are a long-established trophic categorisation largely based on morphology and are used in ecological indices to monitor and analyse the biological state of soils. Stable isotope ratio analysis (13C/12C and 15N/14N, expressed as δ13C and δ15N has provided verification of, and novel insights into, the feeding ecology of soil animals such as earthworms and mites. However, isotopic studies of soil nematodes have been limited to date as conventional stable isotope ratio analysis needs impractically large numbers of nematodes (up to 1,000 to achieve required minimum sample weights (typically >100 µg C and N. Here, micro-sample near-conventional elemental analysis–isotopic ratio mass spectrometry (μEA–IRMS of C and N using microgram samples (typically 20 µg dry weight, was employed to compare the trophic position of selected soil nematode taxa from four feeding groups: predators (Anatonchus and Mononchus, bacterial feeders (Plectus and Rhabditis, omnivores (Aporcelaimidae and Qudsianematidae and plant feeder (Rotylenchus. Free-living nematodes were collected from conventionally and organically managed arable soils. As few as 15 nematodes, for omnivores and predators, were sufficient to reach the 20 µg dry weight target. There was no significant difference in δ15N (p = 0.290 or δ13C (p = 0.706 between conventional and organic agronomic treatments but, within treatments, there was a significant difference in N and C stable isotope ratios between the plant feeder, Rotylenchus (δ15N = 1.08 to 3.22 mUr‰, δ13C = –29.58 to –27.87 mUr and all other groups. There was an average difference of 9.62 mUr in δ15N between the plant feeder and the predator group (δ15N = 9.89 to 12.79 mUr, δ13C = –27.04 to –25.51 mUr. Isotopic niche widths were calculated as Bayesian derived standard ellipse areas and were smallest for the plant feeder (1.37 mUr2 and the predators (1.73 mUr2, but largest for omnivores (3.83 mUr2

Bromide as a tracer for studying water movement and nitrate displacement in soils: comparison with stable isotope tracers

International Nuclear Information System (INIS)

Russow, R.; Knappe, S.

1999-01-01

Tracers are an ideal means of studying water movement and associated nitrate displacement. Often bromide is preferred as a tracer because it is considered a representative tracer for water and because, being a conservative tracer (i.e. not involved in chemical and biological soil processes), it can be used for studying anion transport in soils. Moreover, it is less expensive and easier to measure than the stable isotopes deuterium and 15 N. Its great advantage over radioactive tracers (e.g. tritium), which outweighs their extreme sensitivity and ease of measurement and which it has in common with stable isotopes, is that it does not require radiation protection measures. However, there are also constraints on the use of bromide as a tracer in soil/water/plant systems. Our own studies on different soils using D 2 O, bromide and [ 15 N]-nitrate in lysimeters suggest that the above assumptions on bromide tracers need not always be valid under conditions as they prevail in biologically active soils. As the present paper shows, these studies permit a good assessment of the possibilities and limits to these tracers [de

Soil Organic Carbon Responses to Forest Expansion on Mountain Grasslands

DEFF Research Database (Denmark)

Guidi, Claudia

. Changes in labile soil C were assessed by carbohydrate and thermal analyses of soil samples and fractions. Forest expansion on mountain grasslands caused a decrease in SOC stocks within the mineral soil. The SOC accumulation within the organic layers following forest establishment could not fully...... and thermally labile to resistant components decreased from grassland to forest successional stages, and corresponded to decreased SOC protection within stable aggregates. This PhD thesis showed that mineral SOC stocks and physically protected SOC fractions decreased following forest expansion on mountain......Grassland abandonment followed by progressive forest expansion is the dominant land-use change in the European Alps. Contrasting trends in soil organic carbon (SOC) stocks have been reported for mountainous regions following forest expansion on grasslands. Moreover, its effects on SOC properties...

Soil resistance and resilience to mechanical stresses for three differently managed sandy loam soils

DEFF Research Database (Denmark)

Arthur, Emmanuel; Schjønning, Per; Møldrup, Per

2012-01-01

carbon (CCCsoils to compaction using air permeability (ka), void ratio (e) and air-filled porosity (ε) as functional indicators and to characterise aggregate stability, strength and friability. Aggregate tensile strength...... the compression index and a proposed functional index,was significantly greater for theMFC soil compared to the other two soils. The change in compression index with initial void ratio was significantly less for the MFC than the other soils. Plastic reorganisation of the soil particles immediately after......To improve our understanding of how clay-organic carbon dynamics affect soil aggregate strength and physical resilience, we selected three nearby soils (MFC,Mixed Forage Cropping; MCC,Mixed Cash Cropping; CCC, Cereal Cash Cropping)with identical clay content and increasing contents of organic...

Long-term Differences in Tillage and Land Use Affect Intra-aggregate Pore Heterogeneity

International Nuclear Information System (INIS)

Kravchenko, A.N.; Wang, A.N.W.; Smucker, A.J.M.; Rivers, M.L.

2011-01-01

Recent advances in computed tomography provide measurement tools to study internal structures of soil aggregates at micrometer resolutions and to improve our understanding of specific mechanisms of various soil processes. Fractal analysis is one of the data analysis tools that can be helpful in evaluating heterogeneity of the intra-aggregate internal structures. The goal of this study was to examine how long-term tillage and land use differences affect intra-aggregate pore heterogeneity. The specific objectives were: (i) to develop an approach to enhance utility of box-counting fractal dimension in characterizing intra-aggregate pore heterogeneity; (ii) to examine intra-aggregate pores in macro-aggregates (4-6 mm in size) using the computed tomography scanning and fractal analysis, and (iii) to compare heterogeneity of intra-aggregate pore space in aggregates from loamy Alfisol soil subjected to 20 yr of contrasting management practices, namely, conventional tillage (chisel plow) (CT), no-till (NT), and native succession vegetation (NS). Three-dimensional images of the intact aggregates were obtained with a resolution of 14.6 (micro)m at the Advanced Photon Source, Argonne National Laboratory, Argonne, IL. Proposed box-counting fractal dimension normalization was successfully implemented to estimate heterogeneity of pore voxel distributions without bias associated with different porosities in soil aggregates. The aggregates from all three studied treatments had higher porosity associated with large (>100 (micro)m) pores present in their centers than in their exteriors. Pores 15 to 60 (micro)m were equally abundant throughout entire aggregates but their distributions were more heterogeneous in aggregate interiors. The CT aggregates had greater numbers of pores 15 to 60 (micro)m than NT and NS. Distribution of pore voxels belonging to large pores was most heterogeneous in the aggregates from NS, followed by NT and by CT. This result was consistent with presence of

Impact of Amendments on the Physical Properties of Soil under Tropical Long-Term No Till Conditions.

Directory of Open Access Journals (Sweden)

Antonio C A Carmeis Filho

Full Text Available Tropical regions have been considered the world's primary agricultural frontier; however, some physico-chemical deficiencies, such as low soil organic matter content, poor soil structure, high erodibility, soil acidity, and aluminum toxicity, have affected their productive capacity. Lime and gypsum are commonly used to improve soil chemical fertility, but no information exists about the long-term effects of these products on the physical attributes and C protection mechanisms of highly weathered Oxisols. A field trial was conducted in a sandy clay loam (kaolinitic, thermic Typic Haplorthox under a no-tillage system for 12 years. The trial consisted of four treatments: a control with no soil amendment application, the application of 2.1 Mg ha-1 phosphogypsum, the application of 2.0 Mg ha-1 lime, and the application of lime + phosphogypsum (2.0 + 2.1 Mg ha-1, respectively. Since the experiment was established in 2002, the rates have been applied three times (2002, 2004, and 2010. Surface liming effectively increased water-stable aggregates > 2.0 mm at a depth of up to 0.2 m; however, the association with phosphogypsum was considered a good strategy to improve the macroaggregate stability in subsoil layers (0.20 to 0.40 m. Consequently, both soil amendments applied together increased the mean weight diameter (MWD and geometric mean diameter (GMD in all soil layers, with increases of up to 118 and 89%, respectively, according to the soil layer. The formation and stabilization of larger aggregates contributed to a higher accumulation of total organic carbon (TOC on these structures. In addition to TOC, the MWD and aggregate stability index were positively correlated with Ca2+ and Mg2+ levels and base saturation. Consequently, the increase observed in the aggregate size class resulted in a better organization of soil particles, increasing the macroporosity and reducing the soil bulk density and penetration resistance. Therefore, adequate soil chemical

Impact of Amendments on the Physical Properties of Soil under Tropical Long-Term No Till Conditions.

Science.gov (United States)

Carmeis Filho, Antonio C A; Crusciol, Carlos A C; Guimarães, Tiara M; Calonego, Juliano C; Mooney, Sacha J

2016-01-01

Tropical regions have been considered the world's primary agricultural frontier; however, some physico-chemical deficiencies, such as low soil organic matter content, poor soil structure, high erodibility, soil acidity, and aluminum toxicity, have affected their productive capacity. Lime and gypsum are commonly used to improve soil chemical fertility, but no information exists about the long-term effects of these products on the physical attributes and C protection mechanisms of highly weathered Oxisols. A field trial was conducted in a sandy clay loam (kaolinitic, thermic Typic Haplorthox) under a no-tillage system for 12 years. The trial consisted of four treatments: a control with no soil amendment application, the application of 2.1 Mg ha-1 phosphogypsum, the application of 2.0 Mg ha-1 lime, and the application of lime + phosphogypsum (2.0 + 2.1 Mg ha-1, respectively). Since the experiment was established in 2002, the rates have been applied three times (2002, 2004, and 2010). Surface liming effectively increased water-stable aggregates > 2.0 mm at a depth of up to 0.2 m; however, the association with phosphogypsum was considered a good strategy to improve the macroaggregate stability in subsoil layers (0.20 to 0.40 m). Consequently, both soil amendments applied together increased the mean weight diameter (MWD) and geometric mean diameter (GMD) in all soil layers, with increases of up to 118 and 89%, respectively, according to the soil layer. The formation and stabilization of larger aggregates contributed to a higher accumulation of total organic carbon (TOC) on these structures. In addition to TOC, the MWD and aggregate stability index were positively correlated with Ca2+ and Mg2+ levels and base saturation. Consequently, the increase observed in the aggregate size class resulted in a better organization of soil particles, increasing the macroporosity and reducing the soil bulk density and penetration resistance. Therefore, adequate soil chemical management

Soil, the orphan hydrological compartment: evidence from O and H stable isotopes?

Science.gov (United States)

Hissler, Christophe; Legout, Arnaud; Barnich, François; Pfister, Laurent

2015-04-01

O and H stable isotopes have been successfully used for decades for studying the exchange of waters between the hydrosphere, the pedosphere and the biosphere. They greatly contribute to improve our understanding of soil-water-plant interactions. In particular, the recent hydrological concept of "two water worlds" (separation of meteoric water that infiltrates the soil as (i) mobile water, which can reach the groundwater and can enter the stream, and as (ii) tightly bound water, which is trapped in the soil microporosity and used by plants) calls for a substantial revision of our perceptual models of runoff generation. Nevertheless, there is a need for testing the applicability of this concept over a large range of ecosystemic contexts (i.e.soil and vegetation types). To date, many investigations have focused on the relationship between the various processes triggering isotope fractionation within soils. So far, the dominating perception is that the isotope profile of water observed in soils is solely due to evaporative fractionation and its shape is dependent on climate and soil parameters. However, as of today the influence of biogeochemical processes on the spatio-temporal variability of δ18O and δD of the soil solutions has been rarely quantified. O and H exchanges between soil water and other soil compartments (living organisms, minerals, exchange capacity, organic matter) remain poorly known and require deeper investigations. Eventually, we need to better understand the distribution of O and H isotopes throughout the soil matrix. In order to address these issues, we have designed and carried out two complementary isotope experiments that use one liter soil columns of a 2mm-sieved and air-dried soil. Our objectives were (1) to observe the temporal evolution of the water O and H isotopic composition starting from the field capacity to the complete drying of the soil and (2) to determine the impact of soil biogeochemical properties on the isotopic composition

On-farm assessment of tillage impact on the vertical distribution of soil organic carbon and structural soil properties in a semiarid region in Tunisia.

Science.gov (United States)

Jemai, Imene; Ben Aissa, Nadhira; Ben Guirat, Saida; Ben-Hammouda, Moncef; Gallali, Tahar

2012-12-30

In semiarid areas, low and erratic rainfall, together with the intensive agricultural use of soils, has depleted soil organic carbon and degraded the soil's chemical, biological and physical fertility. To develop efficient soil-management practices for the rapid restoration of severely degraded soils, no-till, mulch-based cropping systems have been adopted. Thus, a study was conducted on a farm to evaluate the effect of a no-tillage system (NT) versus conventional tillage (CT) on the vertical (0-50 cm) distribution of soil organic carbon (SOC), bulk density (BD), total porosity (TP), structural instability (SI), stable aggregates and infiltration coefficient (Ks) in a clay loam soil under rain-fed conditions in a semiarid region of north-western Tunisia. CT consisting of moldboard plowing to a depth of 20 cm was used for continuous wheat production. NT by direct drilling under residue was used for 3 (NT3) and 7 (NT7) years in wheat/fava bean and wheat/sulla crop rotations, respectively. SOC was more significantly increased (p < 0.05) by NT3 and NT7 than by CT at respective depths of 0-10 and 0-20 cm, but a greater increase in the uppermost 10 cm of soil was observed in the NT7 field. NT3 management decreased BD and consequently increased TP at a depth of 0-10 cm. The same trend was observed for the NT7 treatment at a depth of 0-30 cm. Ks was not affected by the NT3 treatment but was improved at a depth of 0-30 cm by the NT7 treatment. Changes in BD, TP and Ks in the NT7 plot were significant only in the first 10 cm of the soil. Both NT3 and NT7 considerably reduced SI (p < 0.1) and enhanced stable aggregates (p < 0.05) across the soil profile. These differences were most pronounced under NT7 at a depth of 0-10 cm. The stratification ratio (SR) of the selected soil properties, except that of SI, showed significant differences between the CT and NT trials, indicating an improvement in soil quality. NT management in the farming systems of north-western Tunisia was

Estimation of soil saturated hydraulic conductivity by artificial neural networks ensemble in smectitic soils

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Sedaghat, A.; Bayat, H.; Safari Sinegani, A. A.

2016-03-01

The saturated hydraulic conductivity ( K s ) of the soil is one of the main soil physical properties. Indirect estimation of this parameter using pedo-transfer functions (PTFs) has received considerable attention. The Purpose of this study was to improve the estimation of K s using fractal parameters of particle and micro-aggregate size distributions in smectitic soils. In this study 260 disturbed and undisturbed soil samples were collected from Guilan province, the north of Iran. The fractal model of Bird and Perrier was used to compute the fractal parameters of particle and micro-aggregate size distributions. The PTFs were developed by artificial neural networks (ANNs) ensemble to estimate K s by using available soil data and fractal parameters. There were found significant correlations between K s and fractal parameters of particles and microaggregates. Estimation of K s was improved significantly by using fractal parameters of soil micro-aggregates as predictors. But using geometric mean and geometric standard deviation of particles diameter did not improve K s estimations significantly. Using fractal parameters of particles and micro-aggregates simultaneously, had the most effect in the estimation of K s . Generally, fractal parameters can be successfully used as input parameters to improve the estimation of K s in the PTFs in smectitic soils. As a result, ANNs ensemble successfully correlated the fractal parameters of particles and micro-aggregates to K s .

In-situ studies of microbial CH{sub 4} oxidation efficiency in Arctic wetland soils. Applications of stable carbon isotopes

Energy Technology Data Exchange (ETDEWEB)

Preuss, Inken-Marie

2013-07-05

Arctic wetland soils are significant sources of the climate-relevant trace gas methane (CH{sub 4}). The observed accelerated warming of the Arctic is expected to cause deeper permafrost thawing followed by increased carbon mineralization and CH{sub 4} formation in water-saturated permafrost-affected tundra soils thus creating a positive feedback to climate change. Aerobic CH{sub 4} oxidation is regarded as the key process reducing CH{sub 4} emissions from wetlands, but quantification of turnover rates has remained difficult so far. This study improved the in-situ quantification of microbial CH{sub 4} oxidation efficiency in arctic wetland soils in Russia's Lena River Delta based on stable isotope signatures of CH{sub 4}. In addition to the common practice of determining the stable isotope fractionation during oxidation, additionally the fractionation effect of diffusion, an important gas transport mechanism in tundra soils, was investigated for both saturated and unsaturated conditions. The isotopic fractionation factors α{sub ox} and α{sub diff} were used to calculate the CH{sub 4} oxidation efficiency from the CH{sub 4} stable isotope signatures of wet polygonal tundra soils of different hydrology. Further, the method was used to study the short-term effects of temperature increase with a climate manipulation experiment. For the first time, the stable isotope fractionation of CH{sub 4} diffusion through water-saturated soils was determined with α{sub diff} = 1.001 ± 0.0002 (n = 3). CH{sub 4} stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was α{sub diff} = 1.013 ± 0.003 (n = 18). For the studied sites the fractionation factor for diffusion under saturated conditions α{sub diff} = 1.001 seems to be of utmost importance for the quantification of the CH{sub 4} oxidation efficiency, since most of the CH{sub 4} is oxidized in the saturated part at the aerobic-anaerobic interface. Furthermore

Impacts of Cropping Systems on Aggregates Associated Organic Carbon and Nitrogen in a Semiarid Highland Agroecosystem.

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Jiashu Chu

Full Text Available The effect of cropping system on the distribution of organic carbon (OC and nitrogen (N in soil aggregates has not been well addressed, which is important for understanding the sequestration of OC and N in agricultural soils. We analyzed the distribution of OC and N associated with soil aggregates in three unfertilized cropping systems in a 27-year field experiment: continuously cropped alfalfa, continuously cropped wheat and a legume-grain rotation. The objectives were to understand the effect of cropping system on the distribution of OC and N in aggregates and to examine the relationships between the changes in OC and N stocks in total soils and in aggregates. The cropping systems increased the stocks of OC and N in total soils (0-40 cm at mean rates of 15.6 g OC m-2 yr-1 and 1.2 g N m-2 yr-1 relative to a fallow control. The continuous cropping of alfalfa produced the largest increases at the 0-20 cm depth. The OC and N stocks in total soils were significantly correlated with the changes in the >0.053 mm aggregates. 27-year of cropping increased OC stocks in the >0.053 mm size class of aggregates and N stocks in the >0.25 mm size class but decreased OC stocks in the 0.25 mm aggregate size class accounted for more than 97% of the total increases in the continuous wheat and the legume-grain rotation systems. These results suggested that long-term cropping has the potential to sequester OC and N in soils and that the increases in soil OC and N stocks were mainly due to increases associated with aggregates >0.053 mm.

Soil friability

DEFF Research Database (Denmark)

Munkholm, Lars Juhl

2011-01-01

This review gathers and synthesizes literature on soil friability produced during the last three decades. Soil friability is of vital importance for crop production and the impact of crop production on the environment. A friable soil is characterized by an ease of fragmentation of undesirably large...... aggregates/clods and a difficulty in fragmentation of minor aggregates into undesirable small elements. Soil friability has been assessed using qualitative field methods as well as quantitative field and laboratory methods at different scales of observation. The qualitative field methods are broadly used...... by scientists, advisors and farmers, whereas the quantitative laboratory methods demand specialized skills and more or less sophisticated equipment. Most methods address only one aspect of soil friability, i.e. either the strength of unconfined soil or the fragment size distribution after applying a stress. All...

Initiation of soil formation in weathered sulfidic Cu-Pb-Zn tailings under subtropical and semi-arid climatic conditions.

Science.gov (United States)

You, Fang; Dalal, Ram; Huang, Longbin

2018-08-01

Field evidence has been scarce about soil (or technosol) formation and direct phytostabilization of base metal mine tailings under field conditions. The present study evaluated key attributes of soil formation in weathered and neutral Cu-Pb-Zn tailings subject to organic amendment (WC: woodchips) and colonization of pioneer native plant species (mixed native woody and grass plant species) in a 2.5-year field trial under subtropical and semi-arid climatic conditions. Key soil indicators of engineered soil formation process were characterized, including organic carbon fractions, aggregation, microbial community and key enzymatic activities. The majority (64-87%) of the OC was stabilized in microaggregate or organo-mineral complexes in the amended tailings. The levels of OC and water soluble OC were elevated by 2-3 folds across the treatments, with the highest level in the treatment of WC and plant colonization (WC+P). Specifically, the WC+P treatment increased the proportion of water stable macroaggregates. Plants further contributed to the N rich organic matter in the tailings, favouring organo-mineral interactions and organic stabilization. Besides, the plants played a major role in boosting microbial biomass and activities in the treated tailings. WC and plants enhanced the contents of organic carbon (OC) associated with aggregates (e.g., physically protected OC), formation of water-stable aggregates (e.g., micro and macroaggregates), chemical buffering capacity (e.g., cation exchange capacity). Microbial community and enzymatic activities were also stimulated in the amended tailings. The present results showed that the formation of functional technosol was initiated in the eco-engineered and weathered Cu-Pb-Zn tailings under field conditions for direct phytostabilization. Copyright © 2018 Elsevier Ltd. All rights reserved.

Genetic and agroindustrial features of meadow brown irrigated soils of Republic of Armenia in terms of climate change and desertification

Directory of Open Access Journals (Sweden)

H.Gh. Ghazaryan

2016-12-01

In the case of prolonged and indiscriminate use the destruction of agronomically valuable structure and reduction of the content of water-stable aggregates occur in humus horizons. This paper provides suggestions of the ways for improving and increasing the fertility of these soils in the conditions of global climate change.

Aggregation and pH-temperature phase behavior for aggregates of an IgG2 antibody.

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Sahin, Erinc; Weiss, William F; Kroetsch, Andrew M; King, Kevin R; Kessler, R Kendall; Das, Tapan K; Roberts, Christopher J

2012-05-01

Monomer unfolding and thermally accelerated aggregation kinetics to produce soluble oligomers or insoluble macroscopic aggregates were characterized as a function of pH for an IgG2 antibody using differential scanning calorimetry (DSC) and size-exclusion chromatography (SEC). Aggregate size was quantified via laser light scattering, and aggregate solubility via turbidity and visual inspection. Interestingly, nonnative oligomers were soluble at pH 5.5 above approximately 15°C, but converted reversibly to visible/insoluble particles at lower temperatures. Lower pH values yielded only soluble aggregates, whereas higher pH resulted in insoluble aggregates, regardless of the solution temperature. Unlike the growing body of literature that supports the three-endotherm model of IgG1 unfolding in DSC, the results here also illustrate limitations of that model for other monoclonal antibodies. Comparison of DSC with monomer loss (via SEC) from samples during thermal scanning indicates that the least conformationally stable domain is not the most aggregation prone, and that a number of the domains remain intact within the constituent monomers of the resulting aggregates. This highlights continued challenges with predicting a priori which domain(s) or thermal transition(s) is(are) most relevant for product stability with respect to aggregation. Copyright © 2012 Wiley Periodicals, Inc.

Enhancement of physical and hydrological properties of a sandy loam soil via application of different biochar particle sizes during incubation period

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Leila Esmaeelnejad

2016-06-01

Full Text Available In spite of many studies that have been carried out, there is a knowledge-gap as to how different sizes of biochars alter soil properties. Therefore, the main objective of this study was to investigate the effects of different sizes of biochars on soil properties. The biochars were produced at two pyrolysis temperatures (350 and 550°C from two feedstocks (rice husk and apple wood chips. Produced biochars were prepared at two diameters (1-2 mm and <1 mm and mixed with soil at a rate of 2% (w/w. Multiple effects of type, temperature and size of biochars were significant, so as the mixture of soil and finer woodchip biochars produced at 550°C had significant effects on all soil properties. Soil aggregation and stabilization of macro-aggregates, values of mean weight diameter and water stable aggregates were improved due to increased soil organic matter as binding agents and microbial biomass. In addition, plant available water capacity, air capacity, S-index, meso-pores and water retention content were significantly increased compared to control. But, saturated hydraulic conductivity (Ks was reduced due to blockage of pores by biochar particles, reduction of pore throat size and available space for flow and also, high field capacity of biochars. So, application of biochar to soil, especially the finest particles of high-tempered woody biochars, can improve physical and hydrological properties of coarse-textured soils and reduce their water drainage by modification of Ks.

Enhancement of physical and hydrological properties of a sandy loam soil via application of different biochar particle sizes during incubation period

Energy Technology Data Exchange (ETDEWEB)

Esmaeelnejad, L.; Shorafa, M.; Gorji, M.; Hosseini, S.M.

2016-11-01

In spite of many studies that have been carried out, there is a knowledge-gap as to how different sizes of biochars alter soil properties. Therefore, the main objective of this study was to investigate the effects of different sizes of biochars on soil properties. The biochars were produced at two pyrolysis temperatures (350 and 550°C) from two feedstocks (rice husk and apple wood chips). Produced biochars were prepared at two diameters (1-2 mm and <1 mm) and mixed with soil at a rate of 2% (w/w). Multiple effects of type, temperature and size of biochars were significant, so as the mixture of soil and finer woodchip biochars produced at 550°C had significant effects on all soil properties. Soil aggregation and stabilization of macro-aggregates, values of mean weight diameter and water stable aggregates were improved due to increased soil organic matter as binding agents and microbial biomass. In addition, plant available water capacity, air capacity, S-index, meso-pores and water retention content were significantly increased compared to control. But, saturated hydraulic conductivity (Ks) was reduced due to blockage of pores by biochar particles, reduction of pore throat size and available space for flow and also, high field capacity of biochars. So, application of biochar to soil, especially the finest particles of high-tempered woody biochars, can improve physical and hydrological properties of coarse-textured soils and reduce their water drainage by modification of Ks. (Author)

Microhabitat Effects on N2O Emissions from Floodplain Soils under Controlled Conditions

Science.gov (United States)

Ley, Martin; Lehmann, Moritz F.; Niklaus, Pascal A.; Kuhn, Thomas; Luster, Jörg

2016-04-01

tendency to emit more N2O than small-aggregate soils. Salix viminalis strongly suppressed the N2O emissions, fully compensating for any aggregate effects. Litter accumulation on the other hand enhanced N2O emission from well-aggregated soils, but showed only a small effect in combination with small aggregates. In moments of highest emission rates, the measured δ15Nbulk of headspace N2O was considerably lower relative to atmospheric N2O (δ15N between -20 ‰ and -25 ‰) in the amended treatments, suggesting N2O production by denitrification or by nitrifier-denitrification. Untreated mesocosms produced an even lower δ15Nbulk (-40‰). Similarly, aggregate formation/size seemed to affect the N2O δ15Nbulk values, suggesting different net N2O production dynamics under different microhabitat conditions, which will be elucidated further, using 15N site preference SP data. Combining stable isotope techniques with quantitative flux data from a mesoscale laboratory experiment, our data highlight the importance of microhabitat effects in modulating N2O emission from floodplain soils. It also underscores their influence on the N2O production pathways involved in the occurrence of N2O emission hot spots and moments.

Stable carbon isotopes as an indicator for soil degradation in an alpine environment (Urseren Valley, Switzerland).

Science.gov (United States)