The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Chongfa Cai - One of the best experts on this subject based on the ideXlab platform.
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Aggregate Stability under Long-Term Fertilization Practices: The Case of Eroded Ultisols of South-Central China
MDPI AG, 2019Co-Authors: Zhonglu Guo, Lichao Zhang, Wei Yang, Li Hua, Chongfa CaiAbstract:Soil Aggregate Stability is an important aspect of soil function and health. Fertilization could potentially alter soil properties and thereby affect Aggregate Stability. To determine which fertilizer is useful for improving soil fertility and stabilizing soil Aggregates and thereby reducing soil erodibility, we examined three types of fertilizer, and measured how soil organic carbon, carbohydrates, and related soil properties influenced Aggregate Stability in eroded Ultisols. Treatments included control (CK), mineral fertilizer nitrogen (N), phosphorus (P), potassium (K) (NPK), fertilizer NPK plus straw (NPKS), and farmyard manure (FYM). Aggregate Stability was tested according to Le Bissonnais method, involving three disruptive tests: fast wetting (FW), slow wetting (SW), and mechanical breakdown (WS). Total organic carbon, particulate organic carbon, mineral-associated carbon, and cold-water-soluble carbohydrate, hot-water-soluble carbohydrate, and dilute acid hydrolysable carbohydrate were measured, as well as soil intrinsic properties (including pH, bulk density, iron and aluminum oxides). The 12-year fertilization had a larger effect on Aggregate Stability and related soil properties in a 0⁻15 cm soil layer, whereas no effect was evident at a soil depth of 15⁻40 cm. MWD (mean weight diameter) under the three tests decreased with increasing soil depth. Fertilization, especially farmyard manure evidently improved MWDFW and MWDWS at a depth of 0⁻15 cm. Slaking was the main mechanism of Aggregate breakdown in Ultisols studied, followed by mechanical breakdown. Correlation analysis showed that MWDFW and MWDWS at a depth of 0⁻15 cm increased with the increase of particulate organic carbon, total organic carbon, hot-water-soluble carbohydrate and pH. Furthermore, their interaction with amorphous iron oxides enhanced Aggregate Stability against slaking or, with amorphous aluminum oxides, modified Aggregate Stability against mechanical breakdown. Consequently, particulate organic carbon was the dominant cementing agent for aggregation in Ultisols studied, and its combination with pH, amorphous aluminum oxides, amorphous iron oxides, and free aluminum oxides play a synergetic role in stabilizing soil Aggregate. Accordingly, farmyard manure or fertilizer NPK plus straw improved soil fertility and the ability to resist slaking
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effects of soil physicochemical properties on Aggregate Stability along a weathering gradient
Catena, 2017Co-Authors: Yujie Wei, Junguang Wang, Di Wang, Li She, Jie Wang, Chongfa CaiAbstract:Abstract The mechanism of soil structure stabilization has been rarely investigated from the perspectives of both soil material composition and porosity due to the complexity of soil structure and its formation process. Here, the relative importance of soil physicochemical properties in Aggregate Stability was evaluated for soils with different weathering degrees. Typical zonal soils derived from quaternary clay were collected from central to south China with increasing precipitation and temperature. Aggregate Stability against slaking (MWDFW), mechanical breakdown (MWDWS) and swelling (MWDSW) was determined, as well as basic properties (including clay content, soil organic matter (SOM), different forms of sesquioxides and pore size distribution (PoSD)). The degrees of soil weathering increased from central to south China with increasing free oxides content. PoSD in the eluvium (A) horizon exhibited triple and double peaks, indicating the decreasing heterogeneity of pore structures, while that in parent material (C) horizon was dominantly characterized by textural pores (
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spatial variations of Aggregate Stability in relation to sesquioxides for zonal soils south central china
Soil & Tillage Research, 2016Co-Authors: Chongfa Cai, Yujie Wei, Junguang Wang, Shuo WangAbstract:Soil Aggregate Stability is an important soil property affecting soil functions and erosion. However, there exists some divergence on the relationship between different forms of sesquioxides and Aggregate Stability, and limited knowledge is available about spatial evolution of Aggregate Stability under climate conditions (temperature and precipitation) and anthropogenic activities. In this study, the spatial variation and profile distribution of soil Aggregate Stability and its relation to sesquioxides under cultivation in different zonal soils were investigated. Typical zonal soils in different weathering degrees were selected that were exposed to an increasing trend of annual average temperature and precipitation (from central to south China). These soils contained low organic matter (<3%) and high variation of sesquioxides in different forms (coefficient of variations CVs in 34–104%). Soil free oxides (Fed and Ald) contents showed an increasing trend across the zonal soils with the content of Fed higher than that of Ald. Both amorphous oxides (Feo and Alo) and complex oxides (Fep and Alp) did not present the obvious increasing variation unlike free oxides across the zonal soils. Soil Alp content was higher than Fep content and their complex degrees decreased with soil depth due to complexation with soil organic matter. Soil Aggregate Stability showed a distinct unimodal trend across the zonal soils and water Aggregate Stability decreased with soil depth. In general, slaking was the main disruptive force in disaggregation, followed by mechanical breakdown. Multiple stepwise regression analysis showed that complex oxides especially the Alp were strongly related with Aggregate Stability, synthetically contributing to dry Aggregate Stability logarithmically and to water Stability in a power function. Soil organic matter had a negative effect on dry Aggregate Stability. Interestingly, it was found that non-complex Fe oxides in amorphous oxides (Feo–Fep) improved water Aggregate Stability against slaking. More studies are needed to gain more insights into the interaction between soil Aggregate stabilization and sesquioxides in future.
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estimating interrill soil erosion from Aggregate Stability of ultisols in subtropical china
Soil & Tillage Research, 2008Co-Authors: Fengling Yan, Zhihua Shi, Chongfa CaiAbstract:Abstract During raindrop impact soil, Aggregates breakdown and produce finer, more transportable particles and micro-Aggregates. These particles and micro-Aggregates appreciably affect the processes of infiltration, seal and crust development, runoff, and soil erosion. Aggregate Stability is, therefore, an important property that may explain, quantify, and predict these processes. This study was designed to develop improved formulae for assessing interrill erosion rate by incorporating the Aggregate Stability index ( A s ) in the prediction evaluations for soil erodibilites of Ultisols in subtropical China. Field experiments of simulated rainfall involving rainstorm simulations with medium and high rainfall intensity were conducted on six cultivated soils for which the soil Aggregate Stability was determined by the LB-method. This study yielded two prediction equations D i = 0.23 A s I 2 (1.05 − 0.85 exp −4sin θ ) and D i = 0.34 A s qI (1.05 − 0.85 exp −4sin θ ) that allowed a comparison of their efficiency in assessing the interrill erosion rate. A s is an Aggregate Stability index, which reflected the main mechanisms of Aggregate breakdown in interrill erosion process, θ is the slope angle, I is the rainfall intensity, and q is the runoff rate. Relatively good agreement was obtained between predicted and measured values of erosion rates for each of the prediction models ( R 2 = 0.86 ** , and R 2 = 0.90 ** ). It was concluded that these formulae based on the Stability index, A s , have the potential to improve methodology for assessing interrill erosion rates for the subtropical Chinese Ultisols. Considering the time-consuming and costly experimentation of runoff rate measurements, the equation without runoff rate ( q ) was the more convenient and effective one to predict interrill erosion rates on Ultisols of subtropical China.
Gang Liu - One of the best experts on this subject based on the ideXlab platform.
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comparison of different methods for assessing effects of soil interparticle forces on Aggregate Stability
Geoderma, 2021Co-Authors: Jingfang Liu, Zilong Wang, Shiwei Zhao, Gang LiuAbstract:Abstract Soil interparticle forces, involving in van der Waals attractive force, and surface hydration and electrostatic repulsive forces, greatly influence the soil Aggregate Stability. However, current studies on methods for evaluating the impact of soil interparticle forces in Aggregate Stability are scarce. This research was aimed to examine the impact of soil interparticle forces on Aggregate Stability using diverse methods for different soil types. Soil Aggregate Stability was tested through the pipette method, wet sieving, and rainfall simulation, respectively characterized by Aggregate Stability index (ASI), mean weight diameter (MWD), and splash erosion mass (SE). Soil interparticle forces were adjusted by the changing concentrations of NaCl solution. The results showed that all three approaches can be applied to study the impact of soil interparticle forces on Aggregate Stability. The ASI, MWD, and SE showed little change below 10−2 mol L−1 NaCl concentration and then ASI and MWD increased at a high rate above 10−2 mol L−1 concentration of NaCl, while the SE showed the opposite trend. These results were as expected for soil interparticle forces. Moreover, for a single soil, a substantial correlation existed between the Aggregate Stability indicators obtained from three methods. However, the order of soil Aggregate Stability, measured by three methods were varied among soil types. Our results suggest that a single method cannot be applied to determine the Aggregate Stability of all soil types even if the breakdown mechanism was identical, because organic matter content and particle size distribution of soil are important factors influencing Aggregate Stability. Hence, in order to compare the difference in Aggregate Stability between various soils, multiple methods should be considered to investigate the impact of interparticle forces of soil on its Aggregate Stability. If a single method was to be chosen, wet sieving may be a good choice as it was not only relatively simple and time-saving but also reflected more comprehensive information about sizes and amount of fragments released from soil Aggregates.
R. J. Haynes - One of the best experts on this subject based on the ideXlab platform.
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Soil organic matter, microbial properties, and Aggregate Stability under annual and perennial pastures
Biology and Fertility of Soils, 2004Co-Authors: R. M. Milne, R. J. HaynesAbstract:The use of annually sown pastures to provide winter forage is common in dairy farming in many regions of the world. Loss of organic matter and soil structural Stability due to annual tillage under this management may be contributing to soil degradation. The comparative effects of annual ryegrass pastures (conventionally tilled and resown each year), permanent kikuyu pastures and undisturbed native vegetation on soil organic matter content, microbial size and activity, and Aggregate Stability were investigated on commercial dairy farms in the Tsitsikamma region of the Eastern Cape, South Africa. In comparison with soils under sparse, native grassy vegetation, those under both annual ryegrass and permanent kikuyu pasture had higher soil organic matter content on the very sandy soils of the eastern end of the region. By contrast, in the higher rainfall, western side, where the native vegetation was coastal forest, there was a loss of organic matter under both types of pasture. Nonetheless, soil organic C, K_2SO_4-extractable C, microbial biomass C, basal respiration, arginine ammonification and fluorescein diacetate hydrolysis rates and Aggregate Stability were less under annual than permanent pastures at all the sites. These results reflect the degrading effect of annual tillage on soil organic matter and the positive effect of grazed permanent pasture on soil microbial activity and aggregation. Soil organic C, microbial biomass C, K_2SO_4-extractable C, basal respiration and Aggregate Stability were significantly correlated with each other. The metabolic quotient and percentage of organic C present as microbial biomass C were generally poorly correlated with other measured properties but negatively correlated with one another. It was concluded that annual pasture involving conventional tillage results in a substantial loss of soil organic matter, soil microbial activity and soil physical condition under dairy pastures and that a system that avoids tillage needs to be developed.
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influence of agricultural land management on organic matter content microbial activity and Aggregate Stability in the profiles of two oxisols
Biology and Fertility of Soils, 2002Co-Authors: C S Dominy, R. J. HaynesAbstract:The effects of agricultural land use on organic matter content and related soil microbial and physical properties were compared with those under undisturbed native grassland in KwaZulu-Natal, South Africa. Two separate farms situated on Oxisols were used and both contained fields with continuous long-term (>20 y) cropping histories. At site 1, soil organic C content in the surface 30 cm followed the order permanent kikuyu pasture > annual ryegrass pasture > native grassland > sugarcane > maize under conventional tillage (CT). At site 2, organic C in the surface 30 cm decreased in the order kikuyu pasture > native grassland > annual ryegrass pasture > maize under zero tillage (ZT) > maize CT. Organic C, microbial biomass C, percentage organic C present as organic C, basal respiration and Aggregate Stability were substantially greater in the surface 5 cm under maize ZT than maize CT but this trend tended to be reversed in the 10- to 30-cm layer. In the undisturbed sites (e.g. native grassland and kikuyu pasture) the metabolic quotient increased with depth. By contrast, under maize CT and sugarcane there was no significant stratification of organic C, yet there was a sharp decrease in the metabolic quotient with depth. Aggregate Stability was high under both native grassland and kikuyu pasture and it remained high to 40 cm depth under the deep-rooted kikuyu pasture. Although soil organic C content was similar under maize CT and sugarcane, values for microbial biomass C, percentage of organic present as microbial biomass, basal respiration and Aggregate Stability were lower, and those for metabolic quotient and bulk density were higher, under sugarcane. This was attributed to the fallow nature of the soil in the interrows of sugarcane fields. It was concluded that the loss of organic matter, microbial activity and Aggregate Stability is potentially problematic under maize CT, sugarcane and annual pasture and measures that improve organic matter status should be considered.
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interactions between soil organic matter status cropping history method of quantification and sample pretreatment and their effects on measured Aggregate Stability
Biology and Fertility of Soils, 2000Co-Authors: R. J. HaynesAbstract:The effects of sample pretreatment (field-moist, air-dried or tension rewetted) on Aggregate Stability measured by wet sieving or turbidimetry were compared for a group of soil samples ranging in organic C content from 20 to 40 g C kg–1. Concentrations of total N, total and hot-water-extractable carbohydrate and microbial biomass C were linearly related to those of organic C. Aggregate Stability measured by wet sieving using air-dried or field-moist samples and that measured by turbidimetry, regardless of sample pretreatment, increased curvilinearly with increasing soil organic C content. However, when tension-rewetted samples were used for wet sieving, Aggregate Stability was essentially unaffected by soil organic C content. Measurements of Aggregate Stability (apart from wet sieving using rewetted soils) were closely correlated with one another and with organic C, total and extractable carbohydrate and microbial biomass C content of the soils. The short-term effects of Aggregate Stability were also studied. Soils from under long-term arable management and those under long-term arable followed by 1 or 3 years under pasture had similar organic C contents, but Aggregate Stability measured by turbidimetry and by wet sieving using air-dried or field-moist samples increased with increasing years under pasture. Light fraction C, microbial biomass and hot-water-extractable carbohydrate concentrations also increased. It was concluded that both total and labile soil organic C content are important in relation to water-stable aggregation and that the use of tension-rewetted samples to measure Stability by wet sieving is unsatisfactory since little separation of values is achieved.
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influence of six crop species on Aggregate Stability and some labile organic matter fractions
Soil Biology & Biochemistry, 1997Co-Authors: R. J. Haynes, M H BeareAbstract:The effect of the growth of barley, wheat, prairie grass, Italian ryegrass, white clover and lupin on the Aggregate Stability and related properties of a heavily cropped soil was investigated in a greenhouse experiment. For the non-leguminous crops, root mass and root length followed the order barley = wheat < prairie grass < Italian ryegrass. Less marked, but similar trends were found for microbial biomass C, cold and hot water-extractable carbohydrate content and Aggregate Stability. It was postulated that a higher root mass results in greater rhizodeposition of carbonaceous material and, therefore, a higher microbial biomass which in turn produces carbohydrate binding agents which increase Aggregate Stability. The hot water-extractable carbohydrate fraction was found to have a galactose plus mannose-to-arabinose plus xylose ratio of 2.1 confirming that it was predominantly of microbial origin. In comparison with the non-legumes, growth of white clover and lupin resulted in an unexpectedly high Aggregate Stability and to a lesser extent microbial biomass C content relative to their rather small root mass and length. Lupin, for example, had the highest Aggregate Stability of all the crops, while white clover had an Aggregate Stability similar to that of Italian ryegrass yet the two legumes had the lowest root length densities of all the crops studied. It was suggested that the rhizosphere microbial population of leguminous plants differed in some way to that of non-legumes (possibly due to the higher N content of rhizodeposited material) and that this contributed to the higher measured Aggregate Stability. A subsidiary experiment showed that fungal hyphal length in Aggregates affected by lupin growth was four times that under wheat. There is a need for further research into aggregation in the rhizosphere of a wider range of legumes.
Zhouping Shangguan - One of the best experts on this subject based on the ideXlab platform.
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variations in soil Aggregate Stability due to land use changes from agricultural land on the loess plateau china
Catena, 2021Co-Authors: Guangyu Zhu, Zhouping Shangguan, Lei DengAbstract:Abstract Soil Aggregate Stability is a feasible and effective factor to understand the complex interactions between physicochemical properties and soil structure. To reveal the distributions of soil Aggregate Stability and its influential factors following land use change from apple orchards abandonment and development in the Nangou watershed of the Loess Plateau, China, this study selected five ages of apple orchards and their planting years were 1 year, 3 years, 6 years, 8 years and 10 years, one 15-year grassland developed from an apple orchard, one 15- year grassland developed from farmland, one natural grassland and one 15-year locust. Results showed that restored vegetation had better soil Aggregate Stability, soil organic carbon (SOC), and nitrogen (N) than apple orchards, and the composition of soil particles with the best Aggregate Stability was clay 6%, silt 8%, and sand 86%. At a 0–10 cm soil depth, soil Aggregate Stability had a significant positive correlation with SOC and soil total nitrogen (STN), and a negative correlation with NO3− and NH4+. In addition, vegetation diversity and coverage only affected the soil Aggregate Stability of the 0–10 cm soil depth; however, soil pH, bulk density, and soil Aggregate-associated inorganic nitrogen were the main influential factors that drove the soil Aggregate Stability of the 0–30 cm soil depth. Further research discovered that macro-Aggregate associated NO3− and micro-Aggregate associated NH4+ may be the key factors affecting the soil Aggregate Stability. Therefore, it is essential to further explore the effect of soil Aggregate-associated inorganic nitrogen on soil Aggregate Stability.
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effects of soil Aggregate Stability on soil n following land use changes under erodible environment
Agriculture Ecosystems & Environment, 2018Co-Authors: Guangyu Zhu, Zhouping Shangguan, Lei DengAbstract:Abstract Soil nitrogen (N) dynamics have considerable effects on the terrestrial carbon cycle, and land use changes could affect soil N through impacts on soil Aggregate Stability. This study selected nine sites including apple orchards of different ages and restored sites to explore the effects of soil Aggregate Stability on soil total N (STN), ammonium N (AN), and nitrate N (NN) following different stages of apple orchard on the Loess Plateau of China. The results showed that when compared with apple orchard sites, the restored sites had higher contents of STN and lower contents of AN and NN, but when compared with restored sites, inorganic-N storage played a more important role in the apple orchards. Following different stages of apple orchards, the STN, AN and NN contents and mean weight diameter (MWD) of soil Aggregates were all improved. MWD had a negative effect on inorganic-N content at 10–30 cm soil depths but had a positive relationship with soil N at 0–10 cm soil depth. In addition, planting apple orchards destroyed soil Aggregate Stability in this erodible environment, but it could be restored soon after abandonment. Therefore, considering soil N and soil Aggregate Stability, it is feasible to plant apple trees in this area and we propose that the effects of trade-offs between soil Aggregate Stability and soil erosion on soil N in terraced agroecosystems should be a focus of future research.
Lei Deng - One of the best experts on this subject based on the ideXlab platform.
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variations in soil Aggregate Stability due to land use changes from agricultural land on the loess plateau china
Catena, 2021Co-Authors: Guangyu Zhu, Zhouping Shangguan, Lei DengAbstract:Abstract Soil Aggregate Stability is a feasible and effective factor to understand the complex interactions between physicochemical properties and soil structure. To reveal the distributions of soil Aggregate Stability and its influential factors following land use change from apple orchards abandonment and development in the Nangou watershed of the Loess Plateau, China, this study selected five ages of apple orchards and their planting years were 1 year, 3 years, 6 years, 8 years and 10 years, one 15-year grassland developed from an apple orchard, one 15- year grassland developed from farmland, one natural grassland and one 15-year locust. Results showed that restored vegetation had better soil Aggregate Stability, soil organic carbon (SOC), and nitrogen (N) than apple orchards, and the composition of soil particles with the best Aggregate Stability was clay 6%, silt 8%, and sand 86%. At a 0–10 cm soil depth, soil Aggregate Stability had a significant positive correlation with SOC and soil total nitrogen (STN), and a negative correlation with NO3− and NH4+. In addition, vegetation diversity and coverage only affected the soil Aggregate Stability of the 0–10 cm soil depth; however, soil pH, bulk density, and soil Aggregate-associated inorganic nitrogen were the main influential factors that drove the soil Aggregate Stability of the 0–30 cm soil depth. Further research discovered that macro-Aggregate associated NO3− and micro-Aggregate associated NH4+ may be the key factors affecting the soil Aggregate Stability. Therefore, it is essential to further explore the effect of soil Aggregate-associated inorganic nitrogen on soil Aggregate Stability.
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effects of soil Aggregate Stability on soil n following land use changes under erodible environment
Agriculture Ecosystems & Environment, 2018Co-Authors: Guangyu Zhu, Zhouping Shangguan, Lei DengAbstract:Abstract Soil nitrogen (N) dynamics have considerable effects on the terrestrial carbon cycle, and land use changes could affect soil N through impacts on soil Aggregate Stability. This study selected nine sites including apple orchards of different ages and restored sites to explore the effects of soil Aggregate Stability on soil total N (STN), ammonium N (AN), and nitrate N (NN) following different stages of apple orchard on the Loess Plateau of China. The results showed that when compared with apple orchard sites, the restored sites had higher contents of STN and lower contents of AN and NN, but when compared with restored sites, inorganic-N storage played a more important role in the apple orchards. Following different stages of apple orchards, the STN, AN and NN contents and mean weight diameter (MWD) of soil Aggregates were all improved. MWD had a negative effect on inorganic-N content at 10–30 cm soil depths but had a positive relationship with soil N at 0–10 cm soil depth. In addition, planting apple orchards destroyed soil Aggregate Stability in this erodible environment, but it could be restored soon after abandonment. Therefore, considering soil N and soil Aggregate Stability, it is feasible to plant apple trees in this area and we propose that the effects of trade-offs between soil Aggregate Stability and soil erosion on soil N in terraced agroecosystems should be a focus of future research.