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Based on the perspective of flight technology and flight safety, the unsaturated clayey foundation soil of a high plateau airport in the mountainous area of southwest China is taken as the research object, and the calculation method of the composite modulus of CFG pile composite foundation with the soil between the piles as the unsaturated soil is established according to the relevant characteristics of unsaturated soil, and the calculation method of the composite foundation's settlement is carried out on the basis of this method. At the same time, Plaxis finite element analysis software is used to model the actual project and numerically analyze the settlement characteristics of the composite foundation. Finally, the calculation results of the two methods are compared and studied with the actual settlement monitoring values on site. The study shows that: 1) the theoretical analysis method is able to consider the effects of pile length, pile modulus, and matrix suction in unsaturated soil of rigid piles on the composite modulus, which is more in line with the reality than the conventional composite modulus method that does not consider the unsaturated nature of the soil between the piles; 2) the resultant values computed by the theoretical and numerical analysis methods recommended in this paper are both smaller than those measured at the site but the difference is within the range of 10%, so that in the actual plateau of the High Plains airports can choose the two analysis methods recommended in this paper to conduct related research. [ABSTRACT FROM AUTHOR]

Natural source zone depletion (NSZD) is the main process of LNAPL (Light Non-Aqueous Phase Liquid) removal under natural conditions. The NSZD rates assessed ranged from 0.55 to 11.55 kg·m−2·a−1 (kilograms per square meter per year) in previous studies. However, most of these data were obtained from sandy sites, with few clayey sites. To gain knowledge of NSZD in clayey soil sites, the study assessed the NSZD of a petroleum hydrocarbon-contaminated clayey soil site in China, combining the concentration gradient method with metagenomic sequencing technology. The results show that the abundance of methane-producing key enzyme mcrA gene in the source zone was more abundant than in background areas, which suggests that there was methanogenesis, the key process of NSZD. The concentration gradients of oxygen and carbon dioxide existed only in shallow soil (<0.7 m), which suggests that there was a thin methane oxidation zone in the shallow zone. The calculated NSZD rates range from 0.23 to 1.15 kg·m−2·a−1, which fall within the moderate range compared to previous NSZD sites. This study expands the knowledge of NSZD in clayey soil and enriches the attenuation rate data for contaminated sites, which is of significant importance in managing petroleum contaminants. [ABSTRACT FROM AUTHOR]

Soil properties are crucial in forest ecological management and rare vegetation protection. In this study, Fanjing Mountain, a typical subtropical forest, was used to investigate and analyze the differences in soil properties and climate change characteristics of Fanjing Mountain in 1982 and 2014. Then redundancy analysis was used to analyze the influence of climate factors on soil properties. The results showed that: 1) Compared to 1982, the soil properties of Fanjian Mountain changed significantly in 2014. The soil texture evolved from a silty loam in 1982 to a silty clay loam in 2014. There was a significant increase in soil clay particles. In addition, the soil showed acidification, weakened cation exchange capacity, and relatively stable soil total nitrogen but significant loss of soil organic matter and total phosphorus nutrients. 2) In the past 32 years, the environmental climate of Fanjing Mountain has shown the characteristics of increasing annual average temperature and annual rainfall, frequent extreme temperature, widening the annual temperature range and decreasing annual relative humidity. 3) Soil type and maximum annual temperature have a highly significant effect on the evolution of soil properties, while annual rainfall and slope orientation significantly affect the evolution. Conclusion: The evolution of soil properties in subtropical forests is dominated by their type differences and climate warming. [ABSTRACT FROM AUTHOR]

• Calibration of red clay with different water contents based on EDEM software. • The Hertz-Mindlin with JKR Cohesion model was used to model red clay soil's physical properties. • Experimental studies provide insights into the impact of soil moisture content on its properties. • Technical references for future research on soil-tool interactions were provided. Distinct physical properties of red clay soil in hilly and mountainous regions of southwest China, including high adhesiveness and density, challenge the operation of agricultural machinery. A scarcity of accurate discrete element simulation parameters for this soil type restricts computational modeling. The study was focused on red clay soil with a moisture content of 12.50% ± 1% and a measured repose angle of 35.54°. The soil's inherent physical properties were identified through experimental assessments. Soil contact mechanical parameters were obtained from the GEMM database, and optimal contact parameter ranges were determined using Steepest Ascent Experiments, with the simulated soil particle repose angle serving as the response value. A second-order regression model was developed using a quadratic regression rotation orthogonal combination test. By taking the actual repose angle as the optimization criterion, parameters were optimized. The optimal contact mechanical parameters in EDEM simulations were identified as: JKR surface energy at 8.981 J/m2, recovery coefficient at 0.474, dynamic friction coefficient at 0.196, and static friction coefficient at 0.45. The model yielded a repose angle of 36.21°, closely corresponding with the observed value, with a relative error of 1.80%. The parameters calibrated in this study offer a valuable reference for future soil-tool interaction studies and tillage implement optimization in these regions. [ABSTRACT FROM AUTHOR]

Background and aims: The accumulation of soil organic carbon (SOC) is a crucial process in mitigating climate change and ensuring soil quality. Subtropical plantations in China have shown high potential for enhancing SOC sequestration due to their high carbon sink capacity. However, the dynamics and compositions of SOC after long term afforestation are still poorly understood. Methods: We examined the dynamics of SOC and its fractions of different soil layers (0–5 cm, 5–10 cm, 10–20 cm, 20–40 cm, 40–80 cm, 80–100 cm) in a mixed broadleaf-conifer plantation (BCP), a Masson pine plantation (MP), and a Slash pine plantation (SP), and an enclosed forest (EF) in subtropical China. Both physical fractions (particulate organic carbon (POC), soil clay organic carbon (SOCclay), soil silt organic carbon (SOCsilt)) and chemical fractions (iron-aluminum-bound organic carbon (Fe/Al-OC), and calcium-bound organic carbon (Ca-OC)) were determined. Additionally, soil physicochemical properties were further analyzed. Results: Our results showed the SOC storage in the EF, BCP, MP, and SP in 2019 increased by 82%, 238%, 126%, and 103% respectively compared to 1984. The proportions of MAOC to SOC were respectively as follows: SP (65.9%) > BCP (64.9%) > EF (61.6%) > MP (53.9%). The mean proportions of SOCclay to MAOC were as follows: BCP (71.1%) > EF (66.9%) > MP (58.5%) > SP (51.0%). The mean proportions of Fe/Al-OC to MAOC were as follows: EF (53.3%) > SP (48.3%) > MP (47.9%) > BCP (39.8%). All these proportion increased with soil depth. RDA and PLS-SEM analysis revealed that soil nitrogen content and electrochemical properties (pH and EC) were the main factors that controlled SOC content and fractions. Conclusions: Subtropical plantations have significant soil carbon sequestration capabilities, but they are currently nearing saturation. Soil nitrogen content may be key factor limiting further enhancement of carbon sequestration. Due to the high proportion of MAOC and relative consistent SOC storage, BCP and SP are recommended as priorities for plantation regeneration in subtropical China. [ABSTRACT FROM AUTHOR]

The acidification of agricultural soil in the southern part of the North China Plain has become more obvious, which is particularly true for the heavy clay soil types, such as yellow-cinnamon and lime concretion black soils. To understand the spatial variability of the pH value and nutrients on the vertical agricultural soil profile of heavy clay soils in this area, we measured pH values and available phosphorus (AP) in 63 farmland sample points from Xiping County in the southern Henan Province. Geostatistical methods and ArcGIS technology were used to map soil pH values along three soil depths (0-10, 10-20, and 20-30 cm) and the spatial distribution of soil AP in the tillage layer (0-20 cm). Furthermore, the correlation between pH and AP was analyzed. The results showed that mean pH values of typical yellow-cinnamon and typical fluvo-aquic soils from three soil layers were 4.98, 4.93, 5.31, and 5.46, 5.81, 6.26, respectively, which gradually increased with soil depths. However, there was no significant difference among the three soil layers. Mean pH values of typical lime concretion black soil from the three soil layers were 5.23, 5.43 and 6.03, respectively, and that of the 20-30 cm soil layer was significantly higher than that of the 0-10 cm (by 0.8-1 pH unit) and the 10-20 cm layers. The pH of the 20-30 cm soil layer of the calcareous lime concretion black and moist soils were also significantly higher than that of the 0-10 and 10-20 cm soil layers. The AP contents of the typical yellow-cinnamon, typical lime concretion black, moist, typical fluvo-aquic and calcareous lime concretion black soils in 0-20 cm soil layer were 8.85-54.75, 4.27-37.49, 8.22-51.80, 6.07-34.82, and 13.22-22.85 mg·kg -1 , respectively. The results of the map indicated that the areas with low AP were distributed in the middle of the study area in blocks, and the areas with high AP were distributed around the study area in dots and flakes. The pH values of the typical yellow-cinnamon, typical lime concretion black, and moist soils positively correlated with the content of AP in the 0-20 cm soil layer. In conclusion, the heavy clay soil in southern Henan Province became stratified acidification, which slowed down along the soil depth. Soil AP contents in the tillage layer were distributed unevenly in the study area, and were affected by soil types and soil pH. These results would be useful for the improvement of heavy clay soil acidification in the southern part of the North China Plain.

Soil texture affects rice nutrient uptake and yield formation by influencing soil structure, microbial activity, and soil nutrient supply capacity. Analyzing the relationship between soil texture, nutrient content, and rice agronomic traits is of great significance for precise and efficient fertilizer application. The tillage layer (0–20 cm) of 31 paddy fields in China's main rice-producing areas was collected to perform rice pot experiments, and soil texture characteristics, physicochemical properties, microbial-related indicators, and rice agronomic traits were measured and analyzed. The results showed that these soils could be classified into four types of soil texture: loamy sandy soil, sandy loam soil, silty loam soil, and silty soil. Analysis of variance showed that the available nitrogen (AN), available potassium (AK), and available phosphorus (AP) contents were the highest in silty loam, silty, and sandy loam soils, respectively, and silt loamy soil had the highest CEC. Principal component analysis (PCA) also showed that soil physicochemical properties can be distinguished to a certain extent according to soil texture types. For the relationship of soil texture parameters and soil physicochemical properties, soil organic matter (OM), total nitrogen (TN), AN, ammonium nitrogen (NH4+-N), and microbial carbon (MBC) contents were positively correlated with soil clay content, AK was positively correlated with silt content, and soil phosphorus status was significantly related to pH. Mantel's test revealed significant correlations between rice N, P, and K nutrient status, dry matter accumulation, and yield, and soil available nutrient content, MBC, pH, and soil texture parameters. Structural equation modeling (SEM) indicated that sand affected soil available nutrients by regulating pH, while clay can positively influence soil available nutrients by affecting soil organic matter mineralization and microbial activity, thus influencing nutrient absorption and yield formation in rice. Overall, in rice production, the silty and silty loam paddy soil with fine texture and higher clay content facilitates the mineralization of soil organic matter and the activity of soil microbes, resulting in more available soil nutrients, which benefits the rice absorption and accumulation of nutrients. Furthermore, a higher content of clay also promotes the distribution of dry matter to the panicle, thereby promoting rice yield formation. [ABSTRACT FROM AUTHOR]

Aims: Soil organic carbon (SOC) storage is mainly governed by inputs from plant and microbial sources. How the relative contributions of these two sources in forest soils vary along broad-scale environmental gradients is poorly understood. The contributions of these two carbon sources in different soil layers are also elusive. Methods: We used amino sugar and lignin phenol as biomarkers to indicate microbial- and plant-derived soil carbon. The concentrations of amino sugar and lignin phenol in topsoil (0–10 cm) and subsoil (30–60 cm) of major forest types along a latitude gradient in China were investigated. Results: The concentration of soil amino sugar decreased along the latitude in topsoil, which is mainly controlled by the variations in mean annual temperature and soil nitrogen. The concentration of lignin phenols decreased along latitude in topsoil, mainly controlled by soil carbon/nitrogen ratio. The microbial-derived carbon was mainly composed of fungi-derived in topsoil, while bacteria-derived dominated in subsoil. Climate and soil properties are primary factors controlling the persistence of microbial residues and lignin phenols in topsoil, and soil clay is the crucial factor in the subsoil. Conclusions: Both microbial residuals and lignin phenols in topsoil showed a decreasing trend with increasing latitude, but controlled by different sets of environmental factors. Subsoil microbial residues and lignin phenols showed no trend along the latitude and are mainly influenced by soil clay content.These findings provide new insights on how climate and vegetation affect soil carbon persistence, revealing significant distribution patterns of forest soil microbial residuals and lignin phenols along a latitude gradient. [ABSTRACT FROM AUTHOR]

Vegetation restoration in dryland regions may be a powerful way to control desertification and promote local habitat recovery. In these artificial revegetation systems, ecosystem processes and functioning are strongly determined by nitrogen (N) availability, while soil inorganic N (SIN) is the major available N form and is absorbed as a main N source for plants. However, SIN dynamics, their influencing factors, and their relative importance to the ecosystem of these N‐limited systems are not well understood. A field investigation was conducted to examine the monthly variations in SIN and its response to planting age and vegetation type in a typical artificial sand‐fixing system in northwestern China. The SIN content in topsoil (0–20 cm) during the growing season ranged from 7.10 to 95.65 mg kg−1, with a mean value of 27.14 mg kg−1. Soil nitrate N had a dominant role in determining SIN monthly dynamics, which showed a fluctuating trend with two peak values in early July and late August. SIN showed a significant increasing trend with the planting age of sand‐fixing vegetation, and it was highest for Nitraria sphaerocarpa (55.66 ± 5.76 mg kg−1), followed by Haloxylon ammodendron (29.81 ± 3.47 mg kg−1) and interspace (11.39 ± 1.13 mg kg−1). SIN displayed a hump‐shaped relationship with air temperature (R2 = 0.96, p < 0.01) and had a maximum at 19.88°C. The change rate of SIN was positively correlated with accumulated precipitation (R2 = 0.99, p < 0.05). SIN was correlated significantly with soil organic carbon (SOC), total nitrogen (TN), and soil clay content. Our results revealed that climatic (air temperature and precipitation), abiotic (soil texture), plant (planting age and vegetation type), and nutrient‐related (SOC and TN) factors regulate SIN dynamics in artificial sand‐fixing vegetation systems. Climate was the predominant factor affecting soil ammonium N, and soil nutrients (SOC and TN) were the predominant factor affecting soil nitrate N. Therefore, these factors should be integrated into optimizing regional vegetation establishment and improving ecosystem management practices in sand‐fixing lands. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is a crucial medium of the global carbon cycle and is profoundly affected by multiple factors, such as climate and management practices. However, interactions between different SOC fractions and land-use change have remained largely unexplored in karst ecosystems with widespread rock outcrops. Owing to the inherent heterogeneity and divergent response of SOC to land-use change, soil samples with close depth were collected from four typical land-use types (cropland, grassland, shrubland, and forestland) in the karst rocky desertification area of China. The aim of this study was to explore the responses of SOC dynamics to land-use types and underlying mechanism. The results showed that land-use type significantly affected SOC contents and its fractions. Compared with cropland, the other three land uses increased the total organic carbon (TOC), microbial biomass carbon (MBC), and non-labile organic carbon (NLOC) contents by 6.11–129.44%, 32.58–173.73%, and 90.98–347.00%, respectively; this demonstrated that a decrease in both labile and recalcitrant carbon resulted in SOC depletion under agricultural land use. Readily oxidized organic carbon (ROC) ranged from 42 to 69%, accounting for almost half of the TOC in the 0–40-cm soil layer. Cropland soil showed significantly higher ROC:TOC ratios than other land-use types. These results indicated that long-term vegetation restoration decreased SOC activity and improved SOC stability. Greater levels of soil exchangeable calcium (ECa) and clay contents were likely responsible for higher stabilization and then accumulation of SOC after vegetation restoration. The carbon pool index (CPI) rather than the carbon pool management index (CPMI) exhibited consistent variation trend with soil TOC contents among land-use types. Thus, further study is needed to validate the CPMI in evaluating land use effects on soil quality in karst ecosystems. Our findings suggest that land-use patterns characterized by grass or forest could be an effective approach for SOC-sequestration potential and ensure the sustainable use of soil resources in the karst area. [ABSTRACT FROM AUTHOR]

Abstract: The red clay soils which are widespread in China are known to be highly sensitive to drought during the dry season but the origin of this high sensitivity to drought remains unclear. Several red clay soils were selected in the Hunan province for study. We studied their basic physico-chemical properties and clay mineralogy, their structure and shrinkage properties, as well as their water retention properties. Results show that the amount of water available between −330 and −15,000hPa water potential is consistent with that recorded in many other clay soils from different parts of the world and thus cannot explain the high sensitivity of the red clay soils to drought. This high sensitivity to drought might be related to the high proportion of poorly available water which was characterized by the amount of available water between −3,300 and −15,000hPa water potential. Comparison with clay soils located in different parts of the world and for which the sensitivity to drought was not identified showed that this proportion of poorly available water is indeed much higher in the red clay soils studied than in clay soils representing a large range of both clay content and mineralogy. This specific behavior of the red clay soils studied is thought to be related to the history of their parent materials: these materials are continental sediments which may have been submitted to great hydric stress, thus leading to strongly consolidated soils with consequences such as a high proportion of poorly available water, strong aggregation and weak shrinkage properties. [Copyright &y& Elsevier]

To achieve the carbonization utilization of Triarrhena lutarioriparia straw and relieve the environmental pressure caused by improper disposal in the Dongting Lake area, the agricultural efficiency of biochar derived from Triarrhena lutarioriparia was clarified. Two typical paddy soils in southern China, namely reddish clayey soil developed from a Quaternary laterite parent material and granitic sandy soil developed from a granite parent material, were selected. Six treatments with different dosage of biochar (0, 1%, 2%, 4%, 6%, and 8% of the soil mass，0-20 cm soil depth) were set. Rice pot experiments were conducted in 2020 to study the effects of different application rates of Triarrhena lutarioriparia biochar on rice nutrient utilization characteristics in two typical soils. The results showed different application rates of Triarrhena lutarioriparia biochar and soil types had certain effects on dry matter accumulation and nutrient uptake by rice organs and aboveground structures. With the addition of biochar, compared with the treatment without biochar, the accumulation of dry matter of rice increased from 0.6% to 18.6% and from 15.5% to 42.4% in the granitic sandy soil and reddish clayey soil, respectively. With the addition of 4% biochar, the accumulation of nitrogen, phosphorus, and potassium nutrients in the rice plant of the treatment increased by 8.6%, 10.5%, and 82.5% in the granitic sandy soil and by 33.8%, 100.0%, and 125.3% in the reddish clayey soil, respectively. The quadratic regression equation and fertilizer – carbon coupling model fitting showed that the optimal addition amounts of biochar in the granitic sandy soil and reddish clayey soil were 2.51% and 4.80% for nitrogen utilization, 4.33% and 7.03% for phosphorus utilization, and 4.67% and 4.81% for potassium utilization, respectively. Therefore, the application of Triarrhena lutarioriparia biochar is conducive to promoting the accumulation and growth of nitrogen, phosphorus and potassium nutrients in rice, and the amount of biochar added and soil conditions are important factors affecting the coupling effect of fertilizer and carbon. [ABSTRACT FROM AUTHOR]

Soil salinization affects more than 25% of land globally. Subsurface pipe drainage is known for its effectiveness in improving saline–alkali land. The red clay layer (RCL) hinders soil improvement in the Hetao Irrigation District of Inner Mongolia, China. The soil water and salt migration rules at different buried depths and RCL were studied based on the field subsurface pipe drainage test and simulation using the DRAINMOD-S model (Version 6.1). The following implications can be drawn from the results: (1) Although the RCL affected the accuracy of the model, the calibrated statistical results met the application requirements, and the DRAINMOD-S model can be used to analyze subsurface pipe drainage under different distribution conditions of the RCL. (2) The RCL can reduce the drainage efficiency of the subsurface pipe, specifically when the distribution is shallow. (3) The soil desalting rate increased with an increase in the buried depth of the subsurface pipe. The desalination effect of shallow soil was better than that of deep soil. The RCL reduced the drainage and salt removal efficiency of the subsurface pipe. Burying the subsurface pipe as far above the RCL as possible should be considered. Thus, it is feasible to apply the DRAINMOD-S model to relevant studies. [ABSTRACT FROM AUTHOR]

Over-fertilization has a significant impact on soil microbial properties and its ecological environment. However, the effects of long-term fertilization on microbial properties on a large scale are still vague. This meta-analysis collected 6211 data points from 109 long-term experimental sites in China to evaluate the effects of fertilizer type and fertilization duration, as well as soil and climate conditions, on the effect sizes on various microbial properties and indices. The organic fertilizers combined with straw (NPKS) and manure (NPKM) had the highest effect sizes, while the chemical fertilizers N (sole N fertilizer) and NPK (NPK fertilizer) had the lowest. When compared with the control, NPKM treatment had the highest effect size, while N treatment had the lowest effect size on MBN (111% vs. 19%), PLFA (110% vs. −7%), fungi (88% vs. 43%), Actinomycetes (97% vs. 44%), urease (77% vs. 25%), catalase (15% vs. −11%), and phosphatase (58% vs. 4%). NPKM treatment had the highest while NPK treatment had the lowest effect size on bacteria (123% vs. 33%). NPKS treatment had the highest while N treatment had the lowest effect sizes on MBC (77% vs. 8%) and invertase (59% vs. 0.2%). NPKS treatment had the highest while NPK treatment had the lowest effect size on the Shannon index (5% vs. 1%). The effect sizes of NPKM treatment were the highest predominantly in arid regions because of the naturally low organic carbon in soils of these regions. The effect sizes on various microbial properties were also highly dependent on soil texture. In coarse-textured soils the effect sizes on MBC and MBN peaked sooner compared with those of clayey or silty soils, although various enzymes were most active in silty soils during the first 10 years of fertilization. Effect sizes on microbial properties were generally higher under NPKM and NPKS treatments than under NPK or N treatments, with considerable effects due to climate conditions. The optimal field fertilizer regime could be determined based on the effects of fertilizer type on soil microorganisms under various climate conditions and soil textures. This will contribute to the microbial biodiversity and soil health of agricultural land. Such controls should be used for adaptation of fertilization strategies to global changes. [ABSTRACT FROM AUTHOR]

White clay soils (Alfisols) are distributed widely in Heilongjiang Province, China, and are important agricultural soils in the province. However, only limited research has been done on the characteristics of these soils. Three representative profiles of these soils were selected to determine the uniformity of parent geological materials by evaluating the elemental ratios [zirconium/strontium (Zr/Sr) and titanium/zirconium (Ti/Zr)] in resistant minerals, mass ratios of different silt fractions, the mineralogy of clay and silt, and chondrite-normalized curves of rare earth elements (REE). The concentrations of Sr, Ti, and Zr were determined by x-ray fluorescence and REE were determined by instrumental neutron activation analysis. Minerals of clay and silt particles were identified by x-ray diffraction methods. The results showed low coefficients of variability associated with ratios of medium/coarse silt (8.3–13), Zr/Sr (5–10), and Ti/Zr (7.5–8.3) in the silt fractions between horizons. The types of minerals present in the clay and silt were the same among horizons. Chondrite-normalized REE curve patterns were very similar between horizons. Taken together, all these results indicate that the parent materials of each horizon of the white clay soils in this study were from the same source of geological material. The uniformity of parent geological materials between soil horizons is important for evaluating any change of soil properties during pedogenesis or caused by soil management. [ABSTRACT FROM AUTHOR]

Chloramphenicol, a broad-spectrum antibiotic employed for controlling bacterial infections, presents an intriguing aspect in terms of its environmental fate in soils. 14C-labeled chloramphenicol was used to explore its mineralization and residue characteristics in three distinct agricultural soils in China. The findings revealed a nuanced pattern in the fate of 14C-chloramphenicol, with notable variations among the different soils under investigation. The chloramphenicol extract residue exhibited a reduction of 18.04% in sandy clay soil, 23.04% in clay loam soil, and 21.73% in loamy clay soil. Notably, the mineralization rate in sandy clay soil was 25.22% surpassed that in the other two soils, particularly during the initial stages of incubation. Over time, the diminishing extract residue underwent conversion into minerals and bound residue. The formation rate of bound residue was increased from 44.59 to 53.65% after adding 10% manure, suggesting that chloramphenicol easily binds with soils rich in organic matter. The bound residue is predominantly localized in the humin fraction across all soils. Additionally, the sterilized soil experiments indicated the pivotal role of microorganisms in influencing the fate of chloramphenicol under the specified experimental conditions. In conclusion, this study offers valuable insights into the environmental dynamics of chloramphenicol in soils, emphasizing the importance of soil composition, organic matter content, and microbial activity. The findings contribute to a scientific understanding of the environmental safety implications associated with chloramphenicol usage. [ABSTRACT FROM AUTHOR]

Water-level fluctuation (WLF) can destroy soil aggregates and induce soil organic carbon (SOC) loss, potentially triggering impacts on the concentration of atmospheric carbon dioxide. However, responses of soil aggregate content and aggregate-associated organic carbon to WLF have not been well studied, especially in the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR). Therefore, samples from different elevations (145 m, 155 m and 165 m) in the WLFZ of the TGR were collected for experiments. The wet sieving method was used to divide soil into silt and clay (<0.053 mm), micro-aggregate (0.053–0.25 mm) and macro-aggregate (>0.25 mm). The K2Cr2O7-H2SO4 oxidation method was used to measure total SOC content in different soil aggregates. A modified Walkley and Black method was used to measure labile carbon in different soil aggregates. Results showed that macro-aggregate content substantially decreased, while micro-aggregate content remained stable and silt and clay fraction accumulated with a decrease in water-level elevations. Moreover, total SOC content and labile carbon in macro-aggregate were obviously higher than those in the micro-aggregate and the silt and clay fraction. Macro-aggregate contributed the most to SOC sequestration, while micro-aggregate contributed the least, and the contribution of macro-aggregate increased with a decrease in water-level elevations. We concluded that the macro-aggregate was the most active participant in the SOC sequestration process, and preferentially increasing the macro-aggregate content of the lowest water-level elevation was conducive to an improvement in soil carbon sequestration potential and would mitigate climate change. [ABSTRACT FROM AUTHOR]

The Mg isotopic compositions of siliciclastic components (δ26Mgsili) of sediments and sedimentary rocks have been commonly used to constrain the intensity of continental weathering, based on observations of, (1) an upward enrichment of 26Mg in modern weathering profiles, (2) preferential uptake of 26Mg in soil clays, and (3) general positive correlations between weathering intensities and δ26Mgsili values. However, not all weathering profiles display an upward increase of δ26Mgsili, and not all soil clays enrich in 26Mg, complicating the interpretations of δ26Mgsili data of sediments and sedimentary rocks. To further explore the controls of δ26Mgsili of sediments and sedimentary rocks, here we measured δ26Mgsili, mineralogical compositions and major element compositions of deep sea sediments from South China Sea (SCS) and carbonate rock samples from two late Paleozoic sections in South China. Carbonate samples show decreasing trends of both normalized Mg concentration (Mgnorm) and δ26Mgsili values with the increase of weathering intensity, while SCS sediments samples do not show any correlation between Mgnorm or δ26Mgsili values and weathering intensity. A three-stages weathering model is developed to explain the observed Mgnorm and δ26Mgsili data. In the new model, weathering can be divided into three stages, (1) the preliminary weathering stage characterized by dissolution of primary minerals and formation of secondary clay minerals in saprolite, (2) the transitional stage with massive vermiculite and chlorite formation on the bottom of soil, and (3) the advanced stage showing dissolution of vermiculite and chlorite in the top of soil. The new model explains an δ26Mgsili increase and Mgnorm decrease with an increase weathering intensity in preliminary weathering stage and decrease of Mgnorm and δ26Mgsiliwith increase weathering intensity in advanced weathering stage. The revised weathering model warrants the application of Mg isotope in the study of continental weathering in deep time. [ABSTRACT FROM AUTHOR]

Identifying the impact path of climate and soil factors on soil δ15N is very crucial for better understanding the N turnover in soils and the integrated information about ecosystem N cycling. Many studies have showed that climate and soil variables influence the change of soil δ15N. However, most of the existing studies focused on the overall impact of factor on soil δ15N, without distinguishing between the direct and indirect effect. Although scholars have studied the relationships among temperature, precipitation, soil N, soil pH, and soil δ15N rather than estimating all the causal relationships simultaneously. To answer the above-mentioned questions, a regional-scale soil collection was conducted across a temperate grassland in northern China. Meanwhile, a PLS-PATH analysis was utilized to evaluate the direct and indirect effects of various factors on soil δ15N and to explore the causal relationships among variables. The results showed that along the transect, mean annual precipitation (MAP) and mean annual temperature (MAT) directly and significantly reduced soil δ15N, and indirectly affected soil δ15N through their effects on soil pH, soil clay, soil N and soil C/N. Soil C/N ratio has a significant direct impact on soil δ15N with a negative correlation. Soil clay, soil N content, and soil pH have a total positive effect on soil δ15N, but the total positive impact of soil pH is very weak because it has a negative indirect impact on soil δ15N by affecting soil clay, soil N and soil C/N ratio. The total influence is, in order, MAP > MAT > soil C/N > soil clay > soil N > soil pH (in absolute value). The above results will provide valuable information about ecosystem N cycle in temperate grassland of northern China. [ABSTRACT FROM AUTHOR]

High potential toxic element (PTE) concentrations in soils that exceed local regulatory threshold values have been reported in non-polluted mountainous areas worldwide. However, there have been few studies that have comprehensively investigated the contribution of natural factors including the parental material, pedogenesis processes and physiochemical properties of soils on the distribution of PTEs in these soils. Therefore, in this study, we studied the distribution of 13 PTEs in sloping farmland soils collected from a mountainous watershed in Guizhou Province, Southwest China. The contributions of natural influencing factors were analyzed using a geostatistical analysis and a geographic detector method. All of the PTEs were unevenly distributed, especially Sb, and the average contents of V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Tl, Pb and Hg were 57.15, 36.20, 4.61, 12.61, 13.36, 63.50, 11.94, 0.78, 0.37, 6.44, 0.48, 27.42 and 0.36mg/kg, respectively. The proportion of samples with Cd, Hg and As exceeding the screening value of the soil pollution risk of agricultural land in China was 46.7%, 5.9% and 4.4%, respectively. Except for Cd and Pb, the q values of the PTEs calculated from the geographical detector were above 0.05, indicating that altitude changes, which affect the pedogenesis process, have a great impact on the spatial distribution. Stratigraphic factors contributed greatly to the distribution of Co, Ni and Cu, which indicates their similarity in parental material. The combined effect of clay content, topographic factors and agricultural land types had the strongest explanatory power for V, Cr, Mo and Pb. The distributions of As, Sb, Tl and Hg are strongly associated with a potential source of mercury ore, and their accumulation is also enhanced by the adsorption on soil clay. Agricultural As also contributes to its distribution. [ABSTRACT FROM AUTHOR]

Soil erosion and surface pollution near reservoirs can adversely affect water quality and safety. Soil aggregate stability is an important predictor of soil water loss and erosion resistance that is strongly influenced by land use. This study therefore aimed to identify factors affecting soil aggregate stability near reservoirs to provide empirical and theoretical insights that could guide the development of management measures to increase land quality, optimize land use, and maximize sustainability. This study focuses on the land around the Shitoukoumen Reservoir in China and examines the effects of six land use types, eleven soil physicochemical properties, and five environmental factors. Ninety-four sets of soil samples were collected in 2021 for analysis of soil aggregates and properties. Particle size classification of soil aggregates was carried out using the wet sieve method and four indicators were calculated to evaluate the effects of land use, soil physicochemical properties, and environmental factors on soil aggregate stability: water stable aggregates (WSA), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (D). Descriptive statistics and geostatistics were used to explore the spatial distributions of soil aggregate stability around the reservoir and the influence of soil properties was studied using correlation analysis and path analysis. The conclusion indicates that land use type significantly affects aggregate stability. The most stable aggregates were found in paddy fields (WSA = 0.77, MWD = 0.76, GMD = 0.57) and forests (WSA = 0.75, MWD = 0.76, GMD = 0.55), followed by an orchard, irrigated land, and grassland. Aggregate stability was worst in upland sites (WSA = 0.61, D = 2.28), where soil aggregates were highly fragmented. There were clear spatial correlations between all four stability indicators. The environmental factors and soil physicochemical characteristics with the strongest influence on aggregate stability were soil organic matter, pH, soil clay content, total nitrogen, and temperature changes. Path analysis revealed that some soil properties affect aggregate stability indirectly, with particularly complex relationships between clay, soil organic matter, and pH. In conclusion, land use type, soil organic matter, pH, soil clay content, total nitrogen, these soil physicochemical properties, and environmental factors, especially temperature, significantly affect soil aggregate stability around reservoirs. In the future, it is necessary to appropriately change upland into paddy land, increase forest land, and appropriately add organic fertilizer to improve soil quality. [ABSTRACT FROM AUTHOR]

Determining the best management practices (BMPs) for farmland under different soil textures can provide technical support for improving maize yield, water- and nitrogen-use efficiencies (WUE and NUE), and reducing environmental N losses. In this study, a two-year (2013–2014) maize cultivation experiment was conducted on two pieces of farmland with different textural soils (loamy clay and sandy loam) in the Phaeozems zone of Northeast China. Three N fertilizer treatments were designed for each farmland: N168, N240, and N312, with N rates of 168, 240, and 312 kg ha−1, respectively. The WHCNS (soil Water Heat Carbon Nitrogen Simulator) model was calibrated and validated using the observed soil water content, soil nitrate concentration, and crop biological indicators. Then, the effects of soil texture combined with different N rates on maize yield, water consumption, and N fates were simulated. The integrated index considering the agronomic, economic, and environmental impacts was used to determine the BMPs for two textural soils. Results indicated that simulated soil water content and nitrate concentration at different soil depths, leaf area index, dry matter, and grain yield all agreed well with the measured values. Both soil texture and N rates significantly affected maize yield, N fates, WUE, and NUE. The annual average grain yield, WUE, and NUE under three N rates in sandy loam soil were 8257 kg ha−1, 1.9 kg m−3, and 41.2 kg kg−1, respectively, which were lower than those of loam clay, 11440 kg ha−1, 2.7 kg m−3, and 46.7 kg kg−1. The order of annual average yield and WUE under two textural soils was N240 > N312 > N168. The average evapotranspiration of sandy loam (447.3 mm) was higher than that of loamy clay (404.9 mm). The annual average N-leaching amount of different N treatments for sandy loam ranged from 5.1 to 13.2 kg ha−1, which was higher than that of loamy clay soil, with a range of 1.8–5.0 kg ha−1. The gaseous N loss in sandy loam soil accounted for 14.7% of the fertilizer N application rate, while it was 11.1%in loamy clay soil. The order of the NUEs of two textural soils was: N168 > N240 > N312. The recommended N fertilizer rates for sandy loam and loamy clay soils determined by the integrated index were 180 and 200 kg ha−1, respectively. [ABSTRACT FROM AUTHOR]

In order to provide a theoretical basis for the evaluation of carbon sequestration potential, we analyzed the adsorption characteristics and influencing factors of dissolved organic carbon（DOC）in typical farmland soils with different fertilization treatments in China. Four typical farmland soils, namely black soil, gray desert soil, fluvo-aquic soil, and red soil, were selected to apply different fertilizer levels of no fertilizer（CK）, chemical N fertilizer（N）, chemical NP fertilizer（NP）, chemical NPK fertilizer（NPK）, and NPK plus organic manure（NPKM）to determine the DOC adsorption capacities by the equilibrium adsorption method. The results showed that the DOC adsorption capacities of different types of soils at the same equilibrium concentration were very different, and were generally in the order of gray desert soil and red soil>black soil>fluvo-aquic soil.Q max appeared in the order of red soil>gray desert soil>black soil>fluvoaquic soil in various soils. Among them, the adsorption characteristics of each soil type were quite different under different fertilization treatments. The general trend ofQ max in the gray desert soil and fluvo-aquic soil under different fertilization treatments were NPKM>NPK> NP>N>CK and in red soil was NPKM>N>NPK>NP

The sandy clayey purple soil is widely distributed in the middle and upper reaches of the Yangtze River, serving as one of the main soil resources in the mountainous areas of southwest China. Intense physical weathering, loose structure, and low erosion resistance are the main characteristics of sandy clayey purple soil. Therefore, environmental disturbance, such as the water fluctuation near reservoirs, heavy rainfall, and groundwater, often induces soil erosion, landslide, settlement, and soil-water disasters of purple soil. A serious threat has been posed on the village buildings and roads, even the agricultural production. The properties of water immersion disintegration with the sandy clayey purple soil can also be an important reason for water and soil disasters in the southwest mountainous areas. It is necessary to clarify the disintegration characteristics and reinforcement for the water-soil disasters prevention and control. In this study, a disintegration test was performed on the purple soil samples with different initial dry densities, water content, and grain gradation using a self-developed instrument. Meanwhile, the disintegration and evolution of sandy clayey purple soil were also analyzed from the perspective of unsaturated effective stress. Bacillus megaterium was selected to reinforce the soil samples with the Microbial Induced Calcite Precipitation (MICP), as the more suitable as Sporosarcina pasteurii in the sandy clayey purple soil areas. A Scanning Electron Microscope (SEM) was then utilized to characterize the morphologies of the soil sample, thereby determining the MICP improvement on the disintegration characteristics of sandy clayey purple soil. The results show that: 1) Four stages were divided in the whole process of immersion and disintegration of sandy clayey purple soil, including the air-water conversion, equilibrium, disintegration development, and disintegration residual stage. 2) The initial dry density, water content, and grain gradation obviously affected the disintegration characteristics of sandy clayey purple soil. Specifically, the disintegration rate and the average disintegration velocity decreased, with the increase of initial dry density and water content. In addition, the average disintegration velocity of soil increased by the content of fine particles. 3) The evolution of water and air was ranging from the pore water closed, double connected, and pore air closed morphology, with the increasing of the initial saturation. Water was rapidly absorbed into the pores under the matric suction, where the pore pressure was changed significantly. Subsequently, the effective stress of unsaturated soil rapidly reduced to the negative, leading to an interparticle compressive stress (the negative tensile stress). Once the tensile stress reached the value of effective cohesion, the unsaturated strength of purple soil was lost completely. Finally, the soil sample was then destroyed under disintegration. The more severe disintegration was also obtained with the decrease in the initial saturation of a soil sample. The decay process of the unsaturated effective stress depended greatly on the initial saturation after the purple soil was immersed in water. Specifically, the average disintegration velocity attenuated exponentially with the increase of the initial saturation. 4) The disintegration rate and the average disintegration velocity of the MICP treated soil samples decreased by 73 to 97 percentage points and 84%-99%, respectively, compared with the untreated soil. Calcium carbonate crystals formed by solidification and deposition greatly reduced the micro-cracks and large pores in the soil structure. As such, a denser pore structure was achieved to enhance the strength of intergranular cementation for the higher resistance to the disintegration of the soil. Consequently, the MICP technology can serve as an effective measure to prevent the water and soil disasters of the sandy clayey purple soil in southwest mountainous areas. [ABSTRACT FROM AUTHOR]

As one of the physical quantities concerned in agricultural production, soil moisture can effectively guide field irrigation and evaluate the distribution of water resources for crop growth in various regions. However, the spatial variability of soil moisture is dramatic, and its time series data are highly noisy, nonlinear, and nonstationary, and thus hard to predict accurately. In this study, taking Jiangsu Province in China as an example, the data of 70 meteorological and soil moisture automatic observation stations from 2014 to 2022 were used to establish prediction models of 0–10 cm soil relative humidity (RHs10cm) via the extreme gradient boosting (XGBoost) algorithm. Before constructing the model, according to the measured soil physical characteristics, the soil moisture observation data were divided into three categories: sandy soil, loam soil, and clay soil. Based on the impacts of various factors on the soil water budget balance, 14 predictors were chosen for constructing the model, among which atmospheric and soil factors accounted for 10 and 4, respectively. Considering the differences in soil physical characteristics and the lagged effects of environmental impacts, the best influence times of the predictors for different soil types were determined through correlation analysis to improve the rationality of the model construction. To better evaluate the importance of soil factors, two sets of models (Model_soil&atmo and Model_atmo) were designed by taking soil factors as optional predictors put into the XGBoost model. Meanwhile, the contributions of predictors to the prediction results were analyzed with Shapley additive explanation (SHAP). Six prediction effect indicators, as well as a typical drought process that happened in 2022, were analyzed to evaluate the prediction accuracy. The results show that the time with the highest correlations between environmental predictors and RHs10cm varied but was similar between soil types. Among these predictors, the contribution rates of maximum air temperature (Tamax), cumulative precipitation (Psum), and air relative humidity (RHa) in atmospheric factors, which functioned as a critical factor affecting the variation in soil moisture, are relatively high in both models. In addition, adding soil factors could improve the accuracy of soil moisture prediction. To a certain extent, the XGBoost model performed better when compared with artificial neural networks (ANNs), random forests (RFs), and support vector machines (SVMs). The values of the correlation coefficient (R), root mean square error (RMSE), mean absolute error (MAE), mean absolute relative error (MARE), Nash–Sutcliffe efficiency coefficient (NSE), and accuracy (ACC) of Model_soil&atmo were 0.69, 11.11, 4.87, 0.12, 0.50, and 88%, respectively. This study verified that the XGBoost model is applicable to the prediction of soil moisture at the provincial level, as it could reasonably predict the development processes of the typical drought event. [ABSTRACT FROM AUTHOR]

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Soft marine deposits are widely distributed in the coastal region of China. The marine soft clays have high water content and high sensitivity, which shows high compressibility and low strength. The installation of precast piles for wind turbines over soft marine clay will generate high excess pore water pressure (EPWP) with very low dissipation rate, resulting in low bearing capacity and large postconstruction settlement, which will affect long-term stability. This study investigated the generation and dissipation of the EPWP correlated with the change in soil structure during the installation of pile foundations in a project of 100 MW wind-power generation in Lianyungang, Jiangsu, China. The results show that the marine soft clay soils feature strong natural structures based on the intrinsic compression concept. The EPWP decreases with increasing distance from the pile, whose influence reaches a distance of 6 m (about 10 times the pile side length). The structural strength of natural sedimentary clay has a remarkable impact on the generated EPWP. The dissipation rate of the EPWP is very slow in mucky clay with more than half the residual value after 30 days, which is mainly attributed to the sharp decline of consolidation coefficient induced by the disturbance of natural clay soils from pile driving. Moreover, hydraulic fracturing can well explain the dissipation characteristics of the EPWP in clay. This phenomenon is actually an ongoing process especially in marine soft clay soils with a strong cementation effect. [ABSTRACT FROM AUTHOR]

Purpose: Land subsidence has caused serious geological damage in many countries, including China. Soil pore number, size, shape, and pore size distribution affect soil deformation and thus land subsidence. Quantification of complex pore structures in different soil types and at various soil depths, however, remains cumbersome. The objective of this study was to quantify pore characteristics of three different soil types using computed tomography (CT) technique, investigate the effects of soil depth, examine the relationships between various parameters, and preliminarily determine the pore deformation pattern. Materials and methods: Undisturbed soil samples (70 mm diameter × 50 mm height) of clay, silt, and silty clay soils were collected from two 300-m-deep engineering geological boreholes on both sides of the Xi'an D7 ground fissure. One hundred CT images were acquired for each soil sample. Soil pore characteristics and morphological parameters, including porosity, macroporosity, coarse mesoporosity, microporosity, number of pores, number of macropores (diameter > 1000 μm), number of coarse mesopores (diameter 200–1000 μm), number of micropores (diameter < 200 μm), circularity, structure model index, degree of anisotropy, and the Euler number, were analyzed. Results and discussion: Micropores were generally regularly shaped and the main contributors to the total number of pores, whereas macropores were mostly elongated and contributed to total porosity. With increasing depth, the most noticeable changes appeared in silt soil and the least noticeable in clay soil. The alternate pore deformation pattern was significant in silt and silty clay soils. Conclusions: Soil depth significantly influenced all soil pore parameters, whereas soil type significantly affected the remaining parameters, except circularity and degree of anisotropy. The elongated macropores in silt and silty clay soils favor land subsidence in the Xi'an area. The present results can help optimize the groundwater exploitation layer, reducing soil compaction and land subsidence in this area. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: Environmental controls of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in the subsoil are important for understanding nutrient cycles; however, these are poorly understood in subtropical paddy soils, especially lacking systematic regional soil profile investigations in the subsoil. The study aims to evaluate the role of environmental factors on concentrations and ratios of SOC, TN, and TP in subsoil (20–100 cm) vs. topsoil (0–20 cm). Methods: We sampled 166 soil cores (1-m depth) from paddy fields across 10 typical counties in 4 provinces of subtropical China. Soil properties of SOC, TN, TP, pH, bulk density, and clay were determined in each soil layer. Spearman correlation analysis and random forest model were performed to correlate environmental factors with soil nutrients and to rank their relative importance throughout the soil profile. Results: SOC was strongly coupled with TN and both decreased with soil depth. However, TP was high in topsoil and did not change in the subsoil. Thus, the soil C to N ratio (12.88–14.93) exhibited minimal variation, whereas N to P (30.93–68.99) and C to P (2.52–5.59) ratios decreased markedly with the soil depth. As compared with topsoil, subsoil revealed similar dominant negative effects of climate (temperature, precipitation) and bulk density on the concentrations and ratios of SOC, TN, and TP. The soil clay had no effect on SOC and TN, but was the dominant control on TP throughout the soil profile. The influences of straw incorporation and chemical fertilization on SOC and TN were primarily observed in topsoil. Conclusions: There were dominant climate controls (temperature and precipitation) of soil C–N–P concentrations and ratios in the subsoil, although different soil factors control SOC and TN vs. TP. These findings highlight the importance of managing subsoil nutrients in subtropical paddy soils, since they are consistently sensitive to climate as topsoil nutrients. [ABSTRACT FROM AUTHOR]

Soil moisture content (SWC) can change the diversity and composition of soil fungal communities by affecting soil texture and soil nutrients. To explore the response of soil fungal communities to moisture in the grassland ecosystem on the south shore of Hulun Lake, we set up a natural moisture gradient that was subdivided into high (HW), medium (MW), and low (LW) water contents. Vegetation was investigated by quadrat method, and aboveground biomass was collected by the mowing method. Soil physicochemical properties were obtained by internal experiments. The composition of the soil fungal community was determined using high-throughput sequencing technology. The results showed significant differences in soil texture, nutrients, and fungal species diversity under the moisture gradients. Although there was significant clustering of fungal communities in different treatments, the fungal community composition was not significantly different. According to the phylogenetic tree, the Ascomycota and Basidiomycota were the most important branches. The fungal species diversity was smaller when SWC was higher, and in this environment (HW), the fungal-dominant species were significantly related to SWC and soil nutrients. At this time, soil clay formed a protective barrier for the survival of the dominant classes Sordariomycetes and Dothideomycetes and increased their relative abundance. In summary, the fungal community responded significantly to SWC on the southern shore of the Hulun Lake ecosystem in Inner Mongolia, China, and the fungal community composition of the HW group was stable and easier to survive. [ABSTRACT FROM AUTHOR]

Although a number of studies have provided information on soil texture, soil classification, and depth to bedrock throughout China, few studies have combined this information, which is the basis for agricultural field management. A total of 81% of China's cultivated lands are distributed among the Middle–Lower Yangtze Plain (18.2%), arid and semiarid North China Plain (18.2%), Northeast Plain (17%), Huang-Huai-Hai Plain (16.1%), and Yunnan–Guizhou Plateau (11.6%). The Huang-Huai-Hai Plain has the highest density of agricultural land (58.5%) and the greatest depth to bedrock of cultivated land (243–402 m). The lowest cultivated depth to bedrock (4–84 m) is concentrated in the Sichuan Basin and its surrounding regions. The main cultivated soil types are Anthrosols, Fluvisols, Cambisols, Phaeozems, Luvisols, Kastanozems, Leptosols, and Acrisols, under the main topsoil texture classes of loam, clay loam, silty clay loam, silt loam, sandy loam, and clay. The Fluvisols had the largest depth to bedrock (156 m) on the Middle–Lower Yangtze Plain and Huang-Huai-Hai Plain, with the highest silt soil distributions but comparable lower sand contents. The Yunnan–Guizhou Plateau had the highest clay soil content. The cultivation under Kastanozems and Leptosols on the Qinghai–Tibet Plateau and in arid and semiarid North China and under Phaeozems on the Northeast Plain should be restricted and managed very cautiously facing erosion risk. The higher percentages of Anthrosols are on the Middle–Lower Yangtze Plain (37%), in Southern China (32%), and on the Yunnan–Guizhou Plateau (26%). The same cultivation aim (i.e., more crop 0production) has produced a similar range of properties over time among the soils developed on agricultural fields, which are classified as Anthrosols. However, various soil types can still be found in agroecosystems because of the variations in climate and topography. Our results highlight that the agriculture-based soil climate and topography shape the interaction of the soil development and not only the pedogenic history of the soil development under variations in the soil depth to bedrock but also the cultivation of distinct pedogenic features. This study provides cultivated soil information on the depth to bedrock, soil classification, and soil texture in China, as well as instructions for field strategies for sustainable agricultural development. [ABSTRACT FROM AUTHOR]

The article examines an important problem of studying greenhouse gas emissions in forest ecosystems. The CH4 emission and absorption dynamics in the soil have been studied based on the physical–chemical and microbiological analysis of forest products. The changes in forest methanogenesis in relation concerning the value of the hydrothermal coefficient have been examined. It was established that the most intensive emission of greenhouse gases was observed within the value of the hydrothermal coefficient (HTC) of 1.8 ... 2. For soils with the HTC value of <1.3, almost no increase in greenhouse gases level was observed. It was found that fluctuations of methane levels in soil were seasonal. Statistical analysis of the obtained results showed sufficient convergence of the results. Thus, the determination coefficient of the obtained results was R2 > 0.7, the Pearson criterion – χ2 ∼ 1, and the Student's t-criterion >0.8. The results showed that methane is almost completely absorbed by forest soils, while CO2 and N2O are released into the atmosphere. Laboratory studies of soil's adsorption capacity relative to hydrocarbon under dynamic conditions have been performed and it has been established that soils with a high composition of organic matter showed significantly higher absorption capacity in comparison with sandy and clayey soils. [ABSTRACT FROM AUTHOR]

In the design of reclamation, long-term settlement is seriously concerned. This paper presents a case study on the ground settlement of a reclamation project in Nansha, China. Fourteen undisturbed soil samples were taken at different depths from this site. Both oedometer tests on fourteen specimens and triaxial hydraulic conductivity tests on nine specimens were conducted. Finite element (FE) modelings using soft soil creep (SSC) model or soft soil (SS) model for modeling clayey soils with or without creep and the calculation using a new simplified method were performed to analyze the consolidation settlement of clay deposits subjected to filled loadings. The FE simulated results and calculated results from the new simplified method were compared with the monitored data in the field. Results show that the curves of the FE modeling using SSC model and the calculation from new simplified method have the same trends as those of the measured settlements. The creep contributes to excess pore pressure dissipation during the consolidation. Furthermore, ground settlements of the reclamation are predicted with the aid of the FE and new simplified method analysis. These predictions can provide the essential information for engineers to control or reduce the settlement in future. [ABSTRACT FROM AUTHOR]

Conventional X-ray diffraction spectrum and synchrotron radiation X-ray diffraction spectrum were used to study the characteristics of soil clay mineral in the terrestrial ecosystem of northern China. The former showed that mineral composition was mainly 2:1 type secondary clay mineral. The existence of clay mineral in the forest soils was identified in the synchrotron radiation X-ray diffraction spectrum, whereas there was no evidence for their presence in the other spectrum. Compared with the conventional method, the synchrotron radiation X-ray diffraction had better resolution, compactedness and scanning range. Therefore, it seemed more suitable for the soil spectroscopy study of terrestrial ecosystem. [ABSTRACT FROM AUTHOR]

Conventionally, red clay is used for agricultural purposes in southern China. Fertilizers, especially urea, are commonly introduced into the red clay to improve the crop yields. However, due to the rapid urbanization in China, large areas of lands with red clays have been converted into sites for domestic and industrial constructions. Nevertheless, few researchers focused on the effect of urea on the strength and compressibility of red clay. In this research, the shear strength and compressibility of the red clay saturated by different concentrations of the (NH4)2CO3 solution (urea's hydrolysates) were experimentally investigated using direct shear as well as oedometer tests, respectively. It was noticed that both the shear strength and stiffness of the red clay significantly decreased after exposure to the urea solution. In addition, the micromechanisms of the strength and compressibility of the red clay treated by the (NH4)2CO3 were studied by the scanning electron microscope test and X‐ray diffraction test. Based on the test results, a new model was developed to simulate the chemomechanical behavior of saturated clayey soil by modifying the Barcelona basic model (BBM) for unsaturated soils. The proposed model introduces four additional parameters, compared to the BBM, to account for the nonlinear shear strength behavior of the red clay. This model accounts for most of the complex features related to the strength and stiffness behavior of clayey soils. The parameter calibration procedures, by using the oedometer and direct shear test results, are also presented. To validate the proposed model, experimental results from the literature are considered in which illite clay samples were either mechanically or chemically or both mechanically and chemically loaded. Part of the experimental results is used to calibrate the model parameters and the other part along with the calibrated parameters is used to verify the proposed model. A comparison between experimental data and predicted results demonstrated that the proposed model is able to capture the main features related to the chemomechanical coupling behavior of saturated soils. [ABSTRACT FROM AUTHOR]

Rhizosphere bacterial community plays a crucial role in diverse biochemical processes, soil type modulates the composition of rhizosphere bacterial community, affects crop yields. In this study, four soil types including Grey clayey soil (GCS), Yellow clayey soil (YCS), Granitic sandy soil (GSS), and Purple clayey soil (PCS) in four rice growth stages were investigated for their impact on bacterial community related to rice rhizosphere and grain yield. The results showed that rice rhizosphere bacterial communities changed with both soil type and growth stage. Diversity index and OTUs number of bacterial community were more heavily influenced by soil type. The results of high-throughput sequencing showed that the bacterial phyla of Bacteroidetes, Chloroflexi, Firmicutes, Proteobacteria, Actinobacteria, Gemmatimonadetes and Acidobacteria were commonly inhabited in the rhizosphere of rice. Among them, Acidobacteria showed the greatest effect on grain yield (λ=0.71, R2=0.51). Based on unweighted pair-group method with arithmetic means (UPGMA) clustering and principal component analysis, the influence of soil type on bacterial community structure was higher than rice growth stage. The physical and chemical properties and bacterial community of soil under YCS treatment were the best. Soil properties had a significant positive effect on rice yield. Bacterial community had a certain effect on rice yield, but the effect did not reach the significant level. [ABSTRACT FROM AUTHOR]

Soil parent material can strongly influence soil's physical and chemical properties, significantly affecting soil organic carbon (SOC) stabilization. However, the importance of different soil parent materials on the amount and composition of subsoil carbon in subtropical soils remains poorly qualified. Subsoil SOC (below A horizon) is chosen for this study because of its higher proportion of stable carbon than surface soils in A horizon. Here, we investigated the dependence of soil mineral‐associated organic carbon (MAOC) and its three mineral‐stabilized fractions on soil physical and chemical parameters (clay content, cation exchange capacity (CEC) and metal oxides) in the subsoil soil (B and C horizons) originating from three contrasting parent materials (sandshale, granite, limestone). The results showed that MAOC accounts for an average of 88% of total SOC, of which organo‐metal complexes (extracted with sodium pyrophosphate) are the dominant form at all three sites. MAOC and its three fractions were significantly correlated with soil clay, CEC, sodium pyrophosphate extractable Fe and oxalate extractable Fe concentrations (P < 0.05), which varied significantly with soil parent material. Since the sodium pyrophosphate plus oxalate‐ extracted mineral‐associated carbon accounted for more than 70% of MAOC, and the molar ratio between sodium pyrophosphate or oxalate‐ extracted mineral‐associated carbon and Fe (C:Fe) ranged from 2.7 to 17.1. The formation of Fe‐associated organic complex is dominated by co‐precipitation when C:Fe is >1. Therefore we conclude that non‐sorptive interactions with the mineral phase through co‐precipitation are the dominant mechanism for SOC stabilization in subtropical forest soils. Plain Language Summary: Identifying the mechanisms for the accumulation and stabilization of forest soil organic carbon (SOC) is particularly important for increasing land‐based carbon mitigation as a part of the solution toward carbon neutrality by 2060 in China. However, our understanding of the mechanism of SOC stabilization is still limited, particularly how soil carbon stabilization is influenced by soil parent material, which has been shown to have strong influences on soil's physical and chemical properties, therefore on SOC stabilization. By analyzing the carbon content and composition of the soils developed from the different parent materials, we showed that soil parent material indirectly affected SOC through soil physical and chemical properties, of which soil clay content, CEC and soil Fe oxides played an important role in SOC stabilization. Both sorptive and co‐precipitation interactions between Fe and SOC contributed to SOC stabilization in subtropical forest soil with co‐precipitation as the dominant mechanism. Key Points: Mineral‐associated organic carbon accounts for >80% of soil organic carbon (SOC) in southern China forest soilsCo‐precipitation with Fe is the dominant SOC stabilization mechanismParent material is a significant contributor to the observed SOC variations [ABSTRACT FROM AUTHOR]

Determining response patterns of plant leaf elements to environmental variables would be beneficial in understanding plant adaptive strategies and in predicting ecosystembiogeochemistry processes. Despite the vital role of microelements in life chemistry and ecosystem functioning, little is known about how plant microelement concentrations, especially their bioconcentration factors (BCFs, the ratio of plant to soil concentration of elements), respond to large-scale environmental gradients, such as aridity, soil properties and anthropogenic activities, in drylands. The aim of the present study was to fill this important gap. We determined leaf microelement BCFs by measuring the concentrations of Mn, Fe, Ni, Cu and Zn in soils from 33 sites and leaves of 111 plants from 67 species across the drylands of China. Leaf microelement concentrations were maintained within normal ranges to satisfy the basic requirements of plants, even in nutrient-poor soil. Aridity, soil organic carbon (SOC) and electrical conductivity (EC) had positive effects, while soil pH had a negative effect on leaf microelement concentrations. Except for Fe, aridity affected leaf microelement BCFs negatively and indirectly by increasing soil pH and SOC. Anthropogenic activities and soil clay contents had relatively weak impacts on both leaf microelement concentrations and BCFs. Moreover, leaf microelement concentrations and BCFs shifted with thresholds at 0.89 for aridity and 7.9 and 8.9 for soil pH. Woody plants were positive indicator species and herbaceous plants were mainly negative indicator species of leaf microelement concentrations and BCFs for aridity and soil pH. Our results suggest that increased aridity limits the absorption of microelements by plant leaves and enhances leaf microelement concentrations. The identification of indicator species for the response of plant microelements to aridity and key soil characteristics revealed that woody species in drylands were more tolerant to environmental changes than herbaceous species. [ABSTRACT FROM AUTHOR]

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Soil total carbon (STC) and total nitrogen (TN) play important roles in providing essential nutrients for vegetation growth, improving soil structural properties, dissipating organic pollutants, and reflecting the fertility of black soils. Based on 1,057 soil samples collected 0 to 20 cm below the surface, geostatistical analysis was used to explore the spatial distribution and factors influencing STC, TN, and C/N ratios in the study area, which is a typical black soil area in northeast China measuring 83,439.04 km2. The soil sampling points were based on randomness and accessibility, spaced 1.25 km apart. The average STC and TN contents and C/N ratios in typical black soil areas of northeast China were 19.25 and 1.88 g kg–1 and 10.07, respectively, and the STC and TN were significantly higher than the national averages (13.26 and 1.32 g kg–1, respectively). The spatial distribution showed a decreasing trend from northeast to southwest, and the nucleation density of STC and TN was highest in the central part and decreased to the north and south. The STC and TN contents and C/N ratio were highest in clayey soil and were 46.11 and 4.23 g kg–1 and 11.39, respectively. The sandy soils had the lowest STC, TN, and C/N ratios. The distribution of STC and TN content is governed by multiple factors, such as human activities, soil type, climate, topography, soil acidity and alkalinity, and land use changes. This study provides the benchmark needed for the development and conservation of China's black soil resources. Core Ideas: Soils in typical black soil areas of northeast China have high total C and N concentrations.The soil total C and total N content increases gradually from southwest to northeast.Soil total C, total N, and the C/N ratio are related to soil pH and precipitation. [ABSTRACT FROM AUTHOR]

The dynamic penetration test (DPT) and the Menard pressuremeter test (PMT) have been widely used in geotechnical survey of deep soils for megadam foundations in western China. The DPT measures are not well utilized due to the lack of correction factors and of empirical relationships for deep soils. This study investigates the relationships between the corrected DPT blow counts (N 120 ′), pressuremeter modulus (EPMT), limit pressure (pL), deformation modulus (E0), and bearing capacity (fak) derived from the PMT results. Meanwhile, a nonlinear regression model is developed to predict the DPT correction factor (a) based on the raw DPT blow counts (N120) and the rod length (L) by integrating the available correction factors for shallow gravelly soils suggested by the code provisions and the deep soil data in this work. It is concluded that the proposed DPT correction factors match well with the code suggestions and the new compiled dataset, and the corrected DPT blow counts can be used to reasonably predict the engineering properties of deep sand and clay soils. Although the proposed correlations need to be tested among different soil types and regions, the results shed the light on in situ geotechnical tests and data utilization for deep and thick overburden. [ABSTRACT FROM AUTHOR]

Many studies have shown that climatic and edaphic factors influence the variations in nitrogen isotopes (δ15N) in terrestrial ecosystems. However, the relative importance of co-varying climatic and edaphic controls on plant δ15N remains somewhat unclear. To address this issue, regional-scale plant (L. chinensis) and soil samples were collected along a longitudinal transect across the temperate grasslands in northern China. The influences of climatic and edaphic factors on the plant δ15N were disentangled using the variable importance in projection (VIP) approach. We found that the climatic and edaphic variables explained 52.4% and 31.2%, respectively, of the variation in plant δ15N. The mean annual precipitation (MAP), soil N, and mean annual temperature (MAT) were the most important variables, but the soil water content (SWC), aridity index (AI), and soil clay content were also important variables. The soil pH and soil C: N ratios were identified as unimportant variables. Furthermore, a high-performance model for simulating plant δ15N values was constructed based on the important variables (VIP > 0.8). Further investigations should focus on the effects of the interaction between the climatic and edaphic variables on the N cycles in the temperate grasslands to provide more reliable predictions of plant δ15N. [ABSTRACT FROM AUTHOR]

Based on the soil temperature and humidity data of soybean farmland under conservation tillage in Northeast China in the published article, the impact of conservation tillage measures on the soil hydrothermal status of soybean farmland in Northeast China was quantitatively assessed by using conventional tillage (CT) as a control, no-tillage (NT), reduced tillage (RT), straw mulching (SM), and no-till straw mulching (NTSM) as treatments. The results showed: compared with CT, conservation tillage increased the soil volume water content of 0-170cm soil layer in soybean farmland in Northeast China by 9.2%, and reduced the temperature of the shallow soil layer (0-30cm) by 8.2%. Four conservation tillage could increase soil moisture under different climatic conditions; straw mulching could increase soil moisture content throughout the growth period of soybeans, and the effect on soil hydrothermal was greatest during the nutrition period of soybean, and soil temperature increased with the increase of straw mulching; the magnitude of soil temperature reduction by conservation tillage decreases with the decrease of soil clay particles, the magnitude of soil moisture increased by conservation tillage decreases with the increase of soil depth. Among them, NTSM at different soil depths was the most obvious effect of water storage and moisture retention, and the soil moisture in the soil layer of 0-20cm was increased by 32.9%. In summary, conservation tillage could increase soil moisture but reduce soil temperatures. Temperature, precipitation, growth period, straw mulching amount, soil type and soil depth all had an impact on soil hydro-thermality in soybean farmland under conservation tillage. [ABSTRACT FROM AUTHOR]

The spatial variability in soil water content in the Daliuta mining area in western China was studied before and after coal mining using ground penetrating radar and geostatistical methods. The relationships among soil water content, soil physical properties, topographical factors, and vegetation density were analysed using classical statistics. The average surface soil water content changed slightly between the two detection events at the centre of the subsidence, from 0.084 cm3/cm3 to 0.079 cm3/cm3; there, the distribution of the soil water content was more closely related to terrain than any of the other factors being considered. Along the subsidence boundary, the surface soil water content decreased significantly after mining, from 0.099 cm3/cm3 to 0.083 cm3/cm3 at one location. The total soil porosity, soil organic matter, and soil clay content were positively correlated with soil water content before mining. However, after mining, the relationship between total soil porosity and soil water content significantly strengthened while the relationships between other soil physical and chemical properties and soil water content weakened. Vegetation was determined to be the main factor controlling the surface soil water content before and after coal mining at one location in a small (1,600 m2) area of the subsidence boundary. [ABSTRACT FROM AUTHOR]

The fractal characteristics of soil particle-size distribution (PSD) constitute an important soil physical property, and fractal models of soil PSD are increasingly used to describe the effects of vegetation on the improvement of soil-related properties. Based on the fractal theory, this paper selected four typical vegetation restoration types (Quercus acutissima, QAC; Robinia pseudoacacia, RPL; Pinus densiflora, PDS; QAC × PDS) in the Taiyi mountainous area as the research object, and the single-fractal dimension (D) and multi-fractal parameters of PSD and its correlation with soil-associated properties were studied. The results show that (1) QAC × PDS reduced the heterogeneity of soil sand distribution, which also increased the range and concentration of soil PSD in the dense area. Soil clay and silt contents showed QAC × PDS > RPL > QAC > PDS. QAC × PDS significantly increased clay and silt content in 0–20 cm soil. (2) D varies among different vegetation restoration types, which was QAC × PDS > RPL > QAC > PDS, and the D of 0–20 cm soil was greater than that of 20–40 cm. For the multi-fractal parameters of PSD, the capacity dimension (D0), information dimension (D1), correlation dimension (D2) and D1/D0 in 0–20 cm soil of different vegetation restoration types showed significant differences. (3) D and multi-fractal parameters were significantly positively correlated with clay and silt contents, which were significantly negatively correlated with sand contents. (4) QAC × PDS had the smallest soil bulk density and largest porosity. Fractal dimension was negatively correlated with soil bulk density and positively correlated with soil total porosity and capillary porosity. These results indicate that the soil fractal dimension can well characterize the vegetation improvement on soil structure and properties in the earthy-rocky mountain areas of northern China. [ABSTRACT FROM AUTHOR]

Unconventional water is an important water resource for agricultural utilization in the drought and water shortage of Northeast China. Additionally, exploration in making full use of it is an important way to alleviate water shortage in China. This paper analyzed the effects of unconventional water through field trials on the accumulation of heavy metals in both cucumbers and the typical black clay soil (expressed as black soil) around the Anshan metallic ore. By exploring the effects of unconventional water after secondary treatment on the accumulation characteristics of heavy metals in cucumbers and the heavy metal balance in the soil–crop system under different conditions, the study shows that there are no significant differences in the heavy metal content when the quantity of unconventional water for irrigation varies. Unconventional water for short-term irrigation does not cause pollution to either the soil environment or the crops. Nor will it cause the accumulation of heavy metals, and the index for the heavy metal content is far below the critical value of the trade standard and national standard, which indicates that the crops irrigated with unconventional water during their growth turn out to be free of pollutants. Unconventional water brings less heavy metals into the black soil than crops. The input and output quantities have only small effects on the heavy metal balance in the black soil. This paper provides a reference for the safety control and evaluation of unconventional agricultural utilization. [ABSTRACT FROM AUTHOR]

The effects of irrigation on winter wheat yield and water use efficiency (WUE) were mostly explored based on site-based experiments in North China Plain (NCP) region. However, due to the influences of contrasting environmental factors (e.g. climate and soil properties), these results cannot be accurately cross-compared among different studies, resulting in the difficulty to get the generalizable pattern at regional scale. Here meta-analysis was conducted to comprehensively evaluate the effects of irrigation on winter wheat yield and WUE in NCP region, with the observation data of 1876 pairs from 186 field experimental papers totally. The differences of the irrigation effects in different regions, precipitation year types, soil texture, and nitrogen (N) application levels were explored, and the corresponding optimal irrigation amounts for reaching high yield and WUE were ascertained. Results showed that compared with non-irrigation during the winter wheat growing period, irrigation increased the yield of winter wheat in NCP by 32.0%-38.3%, and reduced the WUE by 27.1%-30.1%. The yield increment due to irrigation in the northwest of NCP (39.6%-53.5%) with total precipitation during the winter wheat growing period below 150mm was higher than that in the southeast of NCP (24.3%-27.1%) with total precipitation during the winter wheat growing period higher than 150mm, while the decrease of WUE due to irrigation in northwest of NCP (32.4%-37.5%) was higher than that in the southeast of NCP (22.0%-24.3%). The optimum irrigation amount for high yield and WUE of winter wheat was 150-180mm in the northwest and 120-150mm in the southeast. Specifically, for different precipitation year types, the optimum irrigation amounts were 120-150mm with 2 times during jointing and flowering stages for dry year, during jointing and heading stages for normal year, and during jointing and booting stages for wet year. For different soil texture, irrigation under loamy soil had the highest increases in yield, while clay soil had the lowest decreases in WUE; the optimum irrigation amounts of winter wheat with four different soil texture of sandy soil, loam, clay loam and clay were 60-90mm, 120-150mm, 180-210mm, and 150-180mm, respectively. For different N application levels, N application of 120-240kg.ha-1 led to the highest yield and WUE under the irrigation amounts of 80-140mm, of which the higher yield was obtained under irrigation amounts of 110-140mm, and the higher WUE was obtained under the irrigation amounts of 80-110mm. Collectively, the NCP region can achieve the goals of high yield and WUE when irrigation amount was 120-150mm with 2 times but at different stages during different precipitation year types (i.e. dry year, normal year and wet year). Meanwhile, the combination of loam conditions with the N application of 120-240kg.ha-1 can synergistically improve the yield and water use efficiency of winter wheat. [ABSTRACT FROM AUTHOR]

In order to obtain the interaction parameters which can be used for discrete element simulation between the soil-engaging components and clayey black soil in northeast China, the Hertz-Mindlin with JKR Cohesion contact model in EDEM2.7 was used to simulate the clayey black soil. Aiming at the actual working environment with moisture content of 10%-20%, 2 kinds of clayey black soil with moisture content of 12.46%±1% and 17.15%±1% were prepared respectively. The rolling friction coefficient, recovery coefficient, JKR surface energy parameter and the static friction coefficient between the soil particles were used as the model calibrated parameters. The soil repose angle simulated under the simulation parameters was set as the response value. The regression model of the soil repose angle was established based on the Box-Behnken response surface method, and the regression model was optimized by using the soil repose angles under 2 moisture contents obtained by physical experiments. The optimal solution of the contact model parameters of the clayey black soil particles with 2 moisture contents was obtained. The parameter range of the discrete element contact model of clayey black soil with moisture content between 10%-20% were given. The soil repose angle and stacked shape obtained by the simulation experiment with the optimized solution had a high similarity with that of the physical test. At the same time, the static friction coefficients of 3 kinds of soil contact materials such as 65Mn plate, UHMW-PE plate and PTFE plate were tested under the conditions of 4 kinds of moisture content, which were 0, 12.46%, 17.15% and 23.5% respectively. Then for the 2 typical soil contact materials such as 65Mn and PTFE, the slope physical test bench were constructed for the clayey black soil with moisture content of 17.15%±1%. The slope simulation models of 65Mn and PTFE materials were established under the EDEM2.7 software platform. Based on the critical simulation parameters such as JKR surface energy parameter, static friction coefficient, rolling friction coefficient and recovery coefficient between soil particle and soil contact material, the simulated rolling distance of the soil ball on different soil contact materials was set as the response value. The excellent fit regression model of rolling distance for the 2 kinds of typical soil contact materials were established based on the response surface optimization method of Box-Behnkende. The 2 regression models were optimized by the sliding distance obtained by the physical experiment. Then the optimized solution of the contact model parameters of different materials was obtained. The simulation results showed that when the surface energy of JKR between soil and 65Mn was 5.5 J/m2, the recovery coefficient was 0.61, the static friction coefficient was 0.57 and the rolling friction coefficient was 0.056, the rolling distance simulation result was 153.56 mm, which was close to the average rolling distance obtained from physical experiments of 155.93 mm, and the relative error was 1.52%; When the surface energy of JKR between soil and PTFE was 4.08 J/m2, the recovery coefficient was 0.6, the static friction coefficient was 0.52 and the rolling friction coefficient was 0.045, the simulation result of rolling distance was 269.35 mm, which was close to the average rolling distance of 269.55 mm obtained from physical experiment, and the relative error was 0.07%. And the optimized parameters can be used to simulate the discrete parameters between the clayey black soil and the soil-engaging components. The study provides credible basic data for the design and simulation of agricultural machinery under clayey black soil conditions. [ABSTRACT FROM AUTHOR]

Earth pressure balance shield (EPBS) has become the mainstream construction method for metro tunnels in China, which inevitably generates a large amount of discharged soil, putting enormous pressure on the environment and the cost. In order to realize the resource utilization of shield dregs, this paper explored the feasibility of recycling the waste silty clay as a soil conditioner in EPBS tunnel construction. Mixtures of bentonite, wasted silty clay, carboxymethyl cellulose (CMC), and tap water in different ratios were prepared. Defining the substituted ratio as the mass ratio of silty clay to (bentonite + silty clay), the effect of the substituted ratio on the apparent viscosity, flow curve, rheological model and physical stability of bentonite-silty clay composite slurry were investigated. Furthermore, the relationship between slurry microstructures and macroscopic rheological properties was revealed by scanning electron microscopy (SEM). The results show that the constitutive relationship of bentonite slurry (0% substituted ratio) can be well described by Herschel-Bulkley model. The silty clay has a deteriorating effect on the rheological behavior and physical stability, and changes the flow pattern of the composite slurry. Microscopically, CMC makes the clay particles in slurries form agglomerates with larger particle sizes, and can absorb excess free water from the slurry, thus significantly increasing the yield stress and apparent viscosity. The recycling scheme proposed in this study can not only greatly reduce the procurement cost of raw materials, but also eliminate the transportation and disposal costs of discharged soil, which has significant environmental benefits and promising application prospects. [ABSTRACT FROM AUTHOR]