Abstract:In order to guide future applications for soil science grants, the NSFC proposals and grants of soil science in 2023 were analyzed which mainly focused on three secondary application codes related to soil science in Environmental Geoscience discipline, including D0701 Environmental Soil Science, D0709 Fundamental Soil Science, and D0710 Soil Erosion and Soil Fertility. Furthermore, the applications, acceptances, peer reviews, project recommendations, grant funding, research teams, project's scientific attributes and keywords data cloud for various types of NSFC projects were also analyzed comprehensively.

Abstract:Soil extracellular respiration is the engine driving the global biogeochemical cycle, in which microbial nanowires serve as an important pathway for microbes to realize it. Microbial nanowires are electrically conductive fibrous structures that can be tens of microns long and grow on the surface of microorganisms. It directly works on the electron transfer between microorganisms and soil minerals, biomethanation and methanogens, etc, thus affecting the migration and transformation of soil minerals and the emission reduction of greenhouse gases. Microbial nanowires were originally discovered on the surface of Geobacter sulfurreducens when the strain was reducing ferrihydrite. G. sulfurreducens is widely distributed in paddy fields, wetlands, reducing soil, and surface sediments. Due to the abundant extracellular nanowires, G. sulfurreducens occupies a key niche in the food chain of anaerobic microorganisms and participates in the global biogeochemical cycling of some key elements, such as C, N, S and Fe. Because of the accessibility to complete genomic information and genetic maneuverability, G. sulfurreducens has become the model microorganism for studying microbial nanowires. For a long time, experimental evidence based on molecular biology has shown that G. sulfurreducens nanowires are conductive type IV PilA-N pili composed of PilA monomeric subunits and multiple conceived models of electron transfer in PilA-N pili have been developed. However, the recent nanowire structure analysis based on cryo-electron microscopy(cryo-EM) found that G. sulfurreducens expressed various c-type cytochrome nanowires, including but may not be limited to OmcS nanowire, OmcZ nanowire and OmcE nanowire, which were anatomically different conductive cytochrome nanowires with their specific electron transfer roles in G. sulfurreducens. Furthermore, the cryo-EM also showed the expression of PilA-N-C pili, which was located in periplasm, hardly had electronic conductivity, and mainly functioned at assisting the secretion of cytochrome nanowires. The lack of either conductivity or typical type IV nanowire functions indicated that the biological role of PilA-N-C pili is completely different from the previously described PilA-N pili of G. sulfurreducens but is pseudo-pili-like. All these findings constantly questioned and challenged the theory of PilA-N pili. Since then, the issue of "the nature of nanowires" has become the focus of academic debate. As the saying goes, "the more the truth is debated, the clearer it will be." Here, the timeline of G. sulfurreducens nanowires' theoretic studies is taken to summarize the understanding of the structure and function of nanowires. Also, the evidence based on the "nature of nanowires" dispute is systematically analyzed, which will promote the early settlement of the dispute, as well as help mature the theory of soil extracellular respiration and the application of microbial nanowires.

Abstract:In the past twenty years, the emerging and rising of the "Earth's Critical Zone" study has provided a new perspective for re-examining the functions of water, soil, air, life, rock and their intrinsic interactions in earth's surface system. By collecting relevant researche literature on Earth's Critical Zone from 2001~2021 at home and abroad, we conducted a bibliometric analysis using CiteSpace. We introduced the history and current status of Earth's Critical Zone research, in order to provide a theoretical and decision-making support for the comprehensive management of natural resources and ecological restoration of territorial space. The results show that:(i) Earth's Critical Zone have received widespread academic attention from developed countries in Europe, the United States and China; (ii) The research priorities are obviously different among the three stages (i.e. germination, early and rapid development stage); (iii) Soil is the link and core connecting surface and underground processes; (iv) Geophysical technology has become an important tool for understanding the structure and processes of Earth's Critical Zone; (v) Networked observations and model simulations are important directions in the next stage; (vi) The quantification, trade-off, and improvement of functions and services in Earth's Critical Zone are expected to become important decision- support tools. In the future, there is still a need to strengthen research aimed at (i) Boosting infrastructure construction and building a more collaborative network of Earth's Critical Zone observatory; (ii) Construction of interdisciplinary research and talent teams and training new generations of critical zone scientists; (iii) Serving the social needs of sustainable development, apply and develop the Earth's Critical Zone science in practice; (iv) Developing new technologies and methods, and improve theories, models and methodological systems; (v) Revealing the coupling mechanisms of the Earth's Critical Zone processes and their environmental effects, and strengthen the research on the impacts of human activities on water and soil processes, material cycles and energy exchange.

Abstract:Global soil thickness is only about 1 m. Its spatial distribution is nevertheless crucial in many hydrological and ecological processes, and it also determines hillslope stability and channel initiation in geomorphological fields. Due to its significant spatial heterogeneity, it is difficult to obtain the soil thickness distribution on a catchment scale based on existing soil survey databases, geophysical investigations, or empirical models. Therefore, it is urgent to develop a process-based model for soil thickness prediction. In this study, methodologies and theories were comprehensively reviewed, and the applicability of different soil production and soil transport models were evaluated. This study pointed out that the mechanism of soil production by chemical weathering is still unclear and is a theoretical bottleneck restricting the development of soil thickness evolution models. Moreover, the methodology of the model still needs to be further developed, and it is urgent to develop and improve the parameter estimation methods and the adoption of equation forms for describing soil production and soil transport in such models upon applications. From our analysis, we inferred that a hybrid model combining stochastic and process-based models as well as mathematical physically-based methods for determining parameters may help solve many difficulties faced in model applications. Finally, we discussed the possible integration of soil thickness evolution models and soil pedogenesis models based on the theoretical frame of catchment coevolution for predicting soil thickness, texture, layering and organic carbon content variation in the landscape.

Abstract:Soil health is the central theme of sustainable agricultural development. Soil microorganisms cooperatively drive the soil life system by regulating soil ecological functions, environmental functions and immunologic functions, which are the keys to maintaining soil health. Understanding the mechanisms of soil microorganisms mediated soil health is essential to effectively utilize these core microorganisms to maintain and improve soil health. Thus, soil functions, such as soil carbon cycling, nutrient cycling, soil structure regulation, plant disease and insect inhibition and contamination control mediated by soil microorganisms are reviewed to summarize their roles in maintaining or enhancing soil health. Furthermore, as a sensitive indicator of soil health, the roles of soil microorganisms in soil health indication and warning were also studied. Research about mining, construction and application of the core microbiome information database that drives the specific function of soil health and multiple biological processes should be strengthened in the future. This will help to provide a scientific basis for improving the function of agricultural soil ecosystems using soil microorganisms, maintaining soil health and soil sustainable development.

Abstract:Cadmium (Cd) pollution is dispersed over a wide area in farmland soils and seriously threatens the safety of agricultural produce and sustainable development of agriculture due to rapid industrialization and inadequate environmental protection in China. Compared to other toxic elements, Cd is highly carcinogenic and readily accumulates in edible portions of plants to levels that are toxic to humans. Traditional technologies of chemical remediation, physical remediation and phytoremediation have been widely applied to remediate Cd-polluted arable soil, especially in acid soil in some areas of southern China. However, little is known about the remediation technologies of Cd for alkaline arable soils. Alkaline soils are mainly distributed in North China. This area is an important hub for both the crop growing and animal breeding industries, and is suffering from severe Cd pollution as well. To ensure food safety, it is necessary to establish the technology and theory of Cd purification in alkaline soils. This paper reviews the domestic and foreign research trends of Cd remediation strategies, hot technologies, Cd geochemical cycle, and Cd transport and accumulation mechanisms in wheat grains, and analyzes the scientific and technological issues of Cd management and control in alkaline soils. The Web of Science core collection database (WOS) were employed to conduct a bibliometric analysis of the literature on remediation technologies of Cd in alkaline arable soils from 2000-2021 via VOSviewer software. The immobilization technology is popular to remediate Cd contamination in alkaline soils and the top three countries in the number of publications are China, the United States and Australia because of their abundant agricultural resources. Besides, soil acidification is the main reason for the increasing grain concentrations of Cd in alkaline arable soils. Meanwhile, lower soil Eh can increase Cd bioavailability by flooding in alkaline soils, suggesting that irrigation and drainage projects should be built in dry-land soil in North China. However, compared with acidic soil, the research on Cd remediation technology in alkaline arable soils is relatively weak. Currently, alkaline amendments such as clay minerals, biochar and lime are usually applied to lower Cd bioavailability in alkaline soils. However, it is difficult to inhibit the accumulation of Cd in crop grains by improving soil pH due to the large amount of carbonate in alkaline soils. Moreover, the excessive addition of alkaline amendments can destroy the soil structure, leading to soil hardening. Also, in phytoremediation, the high pH of alkaline soil will reduce the uptake of Cd by plant roots, resulting in low remediation efficiency and high cost. The accumulation of Cd in wheat grains is affected by both biotic and abiotic factors, and the complex molecular mechanism of its uptake and transport also limits the development of low-accumulation varieties. Thus, local governments should monitor the Cd concentration and it is imperative to explore and develop new technologies for inhibiting the transfer of Cd to food crops in alkaline soils.

Abstract:【Objective】 Soil magnetic susceptibility is a commonly used proxy index for paleoenvironment reconstruction. The study on the relationship between topsoil magnetic susceptibility and the modern environment is helpful to understand the reasons for the difference in magnetic susceptibility. Researchers around the world had conducted numerous studies on the correlation between soil magnetic susceptibility of sediments and modern soils in different regions and environmental factors. However, previous studies mainly focused on the correlation between soil magnetic susceptibility and climate. This correlation between soil magnetic susceptibility and climate was inconsistently recognized by different researchers because climate is only one of the influencing factors for the variation of soil magnetization rate. The main controlling factors of soil development and soil magnetic susceptibility may vary from region to region, and the magnetic susceptibility reflects the combined effect of multiple environmental factors. At present, the lack of understanding of the causes of soil magnetic susceptibility changes at the regional scale limits the accurate application of magnetic susceptibility as an important proxy index for paleoenvironmental reconstruction. Thus, we hypothesized that(1) the spatial distribution patterns of soil magnetic susceptibility in different regions can respond to environmental variables besides climate and(2) the Normalized Difference Vegetation Index(NDVI), which is the result of the combined effect of climate, topography and soil, can better respond to magnetization rates. 【Method】 The Qinghai-Tibet Plateau is the youngest natural geographic unit in the world with closely integrated horizontal and vertical zonation, influencing regional and global energy and water cycles. It is one of the areas where global changes have had the most significant impact on the land surface because it had undergone six major geological tectonic events and has a variety of parent rock types. The natural environment of the Qinghai-Tibet Plateau is harsh and large-scale soil sampling is very difficult, so regional magnetic studies are limited. In this study, 254 soil samples from the surface layer(layer a of the occurrence layer) of the Qinghai-Tibet Plateau were systematically investigated to determine the soil magnetic susceptibility and other soil properties. Combined with the data of parent material, climate, topography and vegetation, the spatial variation characteristics of soil magnetic susceptibility in the Qinghai-Tibet plateau were clarified and its main influencing factors were analyzed. 【Result】 The results showed that:(a) There was no significant difference in low-frequency magnetic susceptibility χ_lf of topsoil between different parent materials and the difference of percentage frequency magnetic susceptibility χ_fd% was significant. Specifically, the weathering of loess and sand shale > weathering of aeolian sand, moraine and crystalline salt, and there was no significant difference between other parent material types. Among different land uses, there was no significant difference in topsoil, but a significant difference in topsoil χ_fd%:forest and upland > grassland > wasteland.(b) The influence of each principal component on soil magnetic susceptibility was of the order vegetation component > soil physical property component > terrain component > parent material component.(c) Spatially, the variation law of soil magnetic susceptibility was most consistent with that of vegetation normalization index, χ_lf and χ_fd% in the Southeast both showed higher values. Also, the spatial distribution of χ_lf decreased from Southeast to Northwest, the high-value area was located on the southeast edge while the low-value area was located in the middle. Similarly, the spatial distribution of χ_fd% showed a high value in the southeast area and a low value in the western area. 【Conclusion】 Our study shows that magnetic susceptibility can better reflect the spatial distribution characteristics of the vegetation index.

Abstract:【Objective】 This study aimed to grasp the multidimensional spatial distribution characteristics of soil salinization, analyze the factors influencing salinization risk, implement risk area zoning control and improve the efficiency of saline land use. 【Method】 In this study, the Yellow River old riverway in Hekou District, Dongying City, Shandong Province, was selected as the study area. Descriptive statistics on soil salinization status were conducted using classical statistical methods, the two-dimensional spatial distribution pattern of salinization in the study area was analyzed based on GIS interpolation, the three-dimensional spatial distribution of salinity and its change trends were visualized using GMS three-dimensional inverse distance weight interpolation, and a soil salinization risk evaluation model was constructed to quantitatively analyze the risk. 【Result】 The results show that the average salinity of the soil in the study area was 5.84 g·kg^-1, representing severe salinization; and the average pH value was 7.82, indicating weakly alkaline. In two-dimensional space, the areas with high salinity (≥ 6 g·kg^-1) were mainly located in the north of the study area, and the overall trend was decreasing from the coast to the inland. In three-dimensional space, the distribution characteristics of the soil salinity profile were mainly homogeneous, with local surface aggregation and clustering at both ends, showing a complex coexistence of three types:surface aggregation, homogeneous, and clustering at both ends. The risk degree of salinization was divided into four levels and the extremely high-risk areas were mainly distributed in the north-central and northeast of the study area. Also, high-risk areas were mainly distributed in the middle and northeast, moderate-risk areas in the west and southeast, and low-risk areas in the southwest of the study area. 【Conclusion】 We recommend that the following measures should be employed to minimize the risk of salinization and improve the efficiency of resource utilization:preventive measures in extremely high-risk areas, control measures in high-risk areas, and improvement measures in moderate and low-risk areas.

Abstract:【Objective】 High~precision soil organic carbon mapping is the basis for studying the spatiotemporal pattern of cultivated soil organic carbon and its influencing mechanism. Results of the relevant research can provide decision support for the designation of farmland management regarding "carbon sequestration and emission reduction". Agricultural management activities are an important influencing factor of soil organic carbon changes in farmland, but soil organic carbon mapping based on agricultural management activities is relatively rare. The phenological parameters extracted from remote sensing images are a direct reflection of agricultural management activities and have great application potential in studying the impact of agricultural management activities on farmland soil organic carbon. 【Method】 This study selected the paddy fields in Zhangzhou City, Fujian Province as the research object. We used the random forest algorithm, based on five different variable combinations (Group A:only natural environment variables; Group B:natural environment variables + early rice phenological parameters:Group C:natural environment variables + late rice phenological parameters; Group D:natural environment variables + early rice phenological parameters + late rice phenological parameters; Group E:early rice phenological parameters + late rice phenological parameters), to build soil organic carbon content prediction models. By comparing the prediction accuracy of the five groups of models, the spatial distribution characteristics of predicted values, the importance of related influencing factors, and the influence of phenological parameters on the accuracy of soil organic carbon mapping were analyzed. Also, the main influencing factors of soil organic carbon mapping in paddy fields in Zhangzhou City were excavated. Agricultural management activities that have an important impact on soil organic carbon in paddy fields in Zhangzhou City were also identified. 【Result】 The results showed that the differences in the spatial distribution of soil organic carbon in paddy fields in Zhangzhou resulted from the combined effect of natural environmental factors and agricultural management measures. Phenological parameters can effectively improve the mapping accuracy of soil organic carbon in paddy fields in Zhangzhou City. Compared with the prediction model based only on natural factors, the addition of phenological parameters can reduce the error of the prediction model and improve the ability of the model to explain variance. The phenological parameters that had the greatest impact on soil organic carbon in paddy fields in Zhangzhou City were the rate of increase at the beginning of the early rice growing season (h1), the time for the start of the early rice growing season (a1), and the rate of decrease at the end of the early rice growing season (i1). These three most important phenological parameters were positively, negatively, and negatively correlated with soil organic carbon content, respectively. 【Conclusion】 The adoption of water and fertilizer management measures that can promote early growth and rapid germination of the early rice, accelerate the tillering rate of the early rice, and slow down the senescence rate of the early rice will increase the soil organic carbon content in the cultivated land. Building a prediction model based on phenological parameters can effectively improve the accuracy of farmland soil organic carbon mapping. The research on farmland soil organic carbon mapping based on phenological parameters can provide decision support for farmland management. The results of this study can provide a theoretical basis for related research.

Abstract:【Objective】 The study of the groundwater seepage process in saturated soil media is of great importance in many fields, and the differences in the pore-scale structure of soil media have a significant effect on the properties of groundwater seepage. Soil grains cementation degree is one of the basic properties of soil media, but there are few studies on the effect of pore-scale structure differences of soil media with different cementation degrees on the properties of the groundwater seepage process. 【Method】 In this paper, related research is carried out based on pore-scale simulation. Soil media with different cementation degrees are constructed based on the global rearrangement algorithm, and the finite element software package is adopted to simulate the flow fields. 【Result】 The results showed that as the percentage of cemented soil particles Pc increased from 0 to 60.20%, the variation function of the flow field increased by 70.15% (from 1.233 to 2.098). Namely, the spatial heterogeneity of the flow velocity was significantly increased with increasing cementation degree. In addition, the probability density distribution of the flow velocity along the main groundwater flow direction and perpendicular to the main flow direction were increasingly divergent. The area where the flow velocity was close to the mean velocity decreased, and the stagnant regions and the preferential flow areas extend significantly at the same time. When Pc increased from 0 to 60.20%, the proportion of stagnant regions in the groundwater rose 23 times (from 2.06% to 48.31%), while the proportion of dominant flow areas increased nearly 9 times (from 0.27% to 2.41%). Also, when the average velocity of fluid was different, the above change trends of the seepage characteristics with rising cementation degrees remained the same. 【Conclusion】 These findings indicate that the cementation degree of soil particles has a significant effect on the characteristics of the groundwater flow field in saturated soil media. Besides, this paper found that the pore-scale structure differences of soil media with different cementation degrees are the internal reason for the above changes in groundwater seepage process characteristics. The dead-end pore structure formed by cementation, the irregular boundary of the cementation group, and the areas with poor connectivity upstream but connected to the flow area downstream often lead to the appearance of stagnant flow regions. With the increase of the stagnant regions, the fluid flows into the well-connected pores and flows rapidly along these pores. As a result, the dominant flow areas also increased with the rising cementation degree and even formed continuous dominant seepage channels. Under the influence of the simultaneous increase of stagnant regions and the dominant flow areas, the spatial heterogeneity of velocity was significantly enhanced.

Abstract:【Objective】 The "source" and "sink" landscape pattern reflects the land use allocation and spatial element distribution. It equally controls the energy flow and water sediment process of the watershed, which is an important factor affecting nutrient loss in small watersheds. The purpose of this research was to investigate the effect of landscape patterns on the transport of dissolved nutrients in agricultural small watersheds under different rainfall types. 【Method】 The traditional agricultural catchments and agroforestry catchments in the Shipanqiu watershed of the Three Gorges Reservoir Area were selected as the research objects. The concentrations of dissolved nitrogen and phosphorus in the runoff at the outlet section of the catchments were monitored during different intensities of erosive rainfall events. Also, aerial survey data combined with the minimum cumulative resistance model were used to identify the "source" and "sink" landscape spatial pattern. The location-weighted landscape index(LWLI) was used to analyze the impact of the "source" and "sink" landscape pattern on dissolved nutrient transport in the small watershed. On this basis, the response mechanism of dissolved nutrient transport in the small watershed to the "source" and "sink" landscape pattern was further clarified. 【Result】 The results showed that:① In the traditional agricultural catchment area, the landscape area ratio of "source" and "sink" was 1.8:1, which was dominated by "source" landscape, and the vertical differentiation of landscape was obvious. In the agroforestry composite catchments, the landscape ratio of "source" and "sink" was about 1:1, which was evenly distributed, but the high and steep slope area accounted for a high proportion and the average slope was large. ② In the two catchments, the loss load of dissolved nitrogen and phosphorus was rainstorm > moderate rain > heavy rain. In different rainfall events, the nutrient output load and its coefficient of variation in the traditional agricultural catchments were higher than those in agroforestry catchments. The nutrient transport had strong volatility and was more vulnerable to the change in rainfall intensity. ③ Agricultural land was the main source of nutrient loss in both catchments, but due to the limitation of a slope, other woodlands may be important nutrient migration areas in the agroforestry composite catchments. The LWLI of the traditional agricultural catchment was as high as 0.75, which indicated the risk of high nitrogen and phosphorus loss in this catchment. Also, the LWLI of the agroforestry catchment area was 0.28 and with a low nutrient output. This was attributed to the joint action of reasonable landscape spatial patterns and the agroforestry management model. 【Conclusion】 The "source" and "sink" landscape patterns had a significant impact on nutrient loss in small watersheds. The risk of nutrient loss in small watersheds can be judged by the "source" and "sink" location-weighted landscape contrast index. Accordingly, it can provide a basis for the optimization of "source" and "sink" landscape pattern and the prevention and control of non-point source pollution in small watersheds.

Abstract:Purple soil is one of the unique soils in China. Because of its low degree of soil development and poor soil erosion resistance, soil erosion in the purple soil area is very serious, which seriously hinders local agriculture and economic development. 【Objective】 To accurately predict soil erosion changes, we need to scientifically and rationally prevent the occurrence of soil erosion, provide a reference for the prevention and control of soil erosion on purple soil slopes, and promote research on soil and water conservation in purple soil areas. 【Method】 Based on the rainfall data of 43 typical purple soil run-off communities, rainfall, duration and I30 are used as characteristic indicators, and the K-means clustering algorithm was used to classify rainfall; the Random forest (RF) algorithm was used to evaluate the importance of each influencing factor on the depth of run-off (H) and soil loss (S), and the important factor screening was carried out in combination with the path analysis method. The key factors obtained from the screening were used as the input variables of the model, with H and S as the outputs. Also, a predictive model was constructed using BP neural network. 【Result】 The results showed that:(1) The erosive rainfall in the purple mound area in the southwest can be divided into three categories. Among them, the A rain type had a long duration, medium rain intensity, heavy rain volume, the lowest frequency of occurrence, and the greatest erosion, which was an important rain type that caused slope erosion in the area; the B rain type had a short duration, heavy rain, and light rain volume, and the most frequent occurrence, which was the main rain type that caused slope erosion in the area; and the C rain type, which had a medium duration, medium rain intensity, and medium rainfall, which occurred more frequently and also made a greater contribution to slope erosion in the area. (2) The importance of characteristic factors to H and S under each rain type was significantly different. For rain type A, the rain duration (T) was the most important to S (31%), and the importance of each factor to H was relatively uniform. Under rain type B, the influence of each factor on S was small, and the rainfall erosion force (F) was the most important to H (29%). Also, the degree of importance was the highest (29%). Under the rain type C, rainfall (Pr) was the most important to H and S(33%, 36%). (3) The H and S under the three rain types were significantly affected by Pr and the H and S under the B and C rain types were most significantly affected by F, vegetation cover (Vs), and average plant height (Ph) at the same time. (4) The prediction accuracy of H and S using the BP neural network was high, the efficiency coefficient of Nash-Suttclife is higher than 0.95, and the accuracy of the prediction model for H was higher than that of the prediction model for S. 【Conclusion】 Research on the purple soil mound area in the southwest needs to focus on preventing soil erosion caused by high-frequency heavy rainfall. In this study, the two models that used rainfall and other factors to calculate H and S had high forecasting capabilities, which provide technical support for soil erosion prediction to achieve accurate forecasting of soil erosion.

Abstract:【Objective】 Based on the current situation and severity of soil and water loss, it is vital to investigate the nature and extent of surface structure degradation of slope farmland and long-duration rainfall characteristics in the red soil region of southern China.【Method】 The method of long-term rainfall simulation were adopted to test the effects of topsoil structure and rainfall intensity on rainfall redistribution, runoff and sediment yield. In this paper, three rainfall intensities, 30 mm·h^-1, 60 mm·h^-1 and 90 mm·h^-1, respectively, and three cultivation depths, 10 cm, 20 cm and 30 cm, respectively, were set to study the effects of tillage lager depth and rainfall intensity on surface flow, subsurface flow, soil loss rate and erosion pattern.【Result】 The results showed that:(1) The topsoil structure significantly changed the redistribution process of runoff. Higher tillage layer depth can mitigate the effects of rainfall intensity, reduce the surface flow coefficient, and increase subsurface flow. Under the condition of 60 mm·h^-1 and 90 mm·h^-1 rainfall intensity, the average surface flow coefficient decreased in the sequence of 70.5% (TLD10 cm), 62.9% (TLD20 cm), and 56.8% (TLD30 cm), and the average subsurface flow ratio increased in the sequence of 7.1% (TLD10 cm), 12.3% (TLD20 cm), and 18.1% (TLD30 cm). (2) The soil loss rate was enhanced with the increase in rainfall intensity but decreased with the depth of the tillage layer. Under 60 mm·h^-1 rainfall intensity, the peak soil loss rate of 10 cm, 20 cm and 30 cm tillage depth were 35.1, 25.6 and 20.5 g·m^-2 min^-1, respectively. For 90 mm·h^-1 rainfall intensity, these values were 68.7, 55.8 and 48.4 g·m^-2 min^-1, respectively. (3) Rainfall intensity and topsoil structure significantly affect the final slope erosion forms. With the increase of tillage layer depth, the erosion degree decreased significantly. Under the condition of 30 mm·h^-1 rainfall intensity, the surface of the soil was relatively intact, and the soil erosion type was splash erosion. Also, under the condition of 60 mm·h^-1 rainfall intensity, the soil erosion was all sheet flow erosion, under 10 cm and 20 cm tillage depth, spot erosion appeared in the lower part of the slope, and the soil erosion degree was lower for sheet flow erosion at 30 cm tillage depth. For the 90 mm·h^-1 rainfall intensity, rill erosion appeared on the slope while at 10 cm tillage depth, rill erosion was well developed. In addition, at 20 cm tillage layer depth, rill erosion development was significant while at 30 cm tillage depth, slope erosion was mainly sheet flow erosion.【Conclusion】 The top soil structure can significantly change the relationship between rainfall and runoff. Higher tillage layer depth can reduce surface erosion, promote the deep infiltration of soil moisture, and increase the soil's deep-water holding capacity. Also, this research can serve as a reference for the rational layout of topsoil structure, improvement of rainfall utilization rate and enhancement of soil erosion resistance in the southern red soil area.

Abstract:【Objective】 With the rapid development of industrialization and urbanization, heavy metal pollution in soil has attracted worldwide attention. Natural soil colloids, as well as engineered nanoparticles introduced into soil by direct or indirect pathways, play an important role in the migration and bioavailability of heavy metals. However, there is a lack of research on the current status and frontier trends of soil colloids' effect on the behavior of heavy metals. 【Method】 Based on the Web of Science(WoS) core collection database, a bibliometric study on the effect of soil colloids on the behavior of heavy metals during 1990-2021 was carried out using analysis tools self-provided by WoS, HisCite citation analysis software, VOSviewer and Citespace visual analysis software. 【Result】 Results indicated that the number of publications increased steadily year by year worldwide, with an average increase of two publications per year. The research in this field started late in China but it showed a momentum of rapid development in recent years which may be due to a series of important measures for soil pollution control implemented in China. The countries and research institutions with the most publications in this field were the United States and the Chinese Academy of Sciences, respectively. Environmental Science & Technology was the most published journal. The major subjects involved in this field were the intersection of environmental sciences and ecology. The results of keywords cluster analysis indicated that "particle size fractionation and heavy metal speciation distribution of soil colloids", "release, deposition of soil colloids and adsorption of heavy metals" and "migration mechanism and migration model of soil colloids" were the dominating research topics. Also, the first dominating research topic tended to describe the state of distribution and morphology of heavy metals in soil with different particle sizes. Furthermore, the second and third dominating research topics tended to focus on the dynamic process of release, migration and deposition of soil colloids, the binding effect of soil colloids on heavy metals and their cooperative transport behavior. The current research hotspot involves the study of the behavior, migration, transformation and bioavailability of engineered nanoparticles in soil using advanced characterization techniques such as field flow-fractionation technology. 【Conclusion】 These results provide important insights into the research direction, growing trend and research hotspots in the field of soil colloids affecting the behavior of heavy metals. In the future, it should be prioritized that the application of field-flow fractionation technology combined with single particle inductively coupled plasma mass spectrometry or other technologies to further study the complex interaction between soil colloids and engineering nanoparticles. Also, the influence on the migration and environmental fate of engineered nanoparticles is expected to be a future research direction.

Abstract:【Objective】 Tire wear particles (TWPs), as one of the important types of microplastics (MPs), have received a lot of attention from ecologists for their ecological risk in recent times. Usually, the environmental behavioral processes of particulate pollutants are important influencing factors of their ecological risk. However, the migration process and influencing mechanisms of TWPs in porous media such as soil have not been reported so far. 【Method】 In this paper, C-TWPs prepared by freezing crushing and R-TWPs (rolling friction) and S-TWPs (sliding friction) produced by road wear were selected as typical research objects, and quartz sand columns were used to simulate and study the migration behavior of TWPs in environmental porous media such as soil, and to investigate the effects of natural organic matter humic acid (HA) and different pH (4, 7 and 10) environments on the migration behavior of the above three types of TWPs.【Result】 The results showed that HA (50 mg·L^-1) significantly enhanced the mobility of the three types of TWPs, and the migration behavior of TWPs was differently affected by different pH (4, 7 and 10) environmental conditions in the presence of HA (50 mg·L^-1), with the medium-alkaline environment(pH=7/10) being more favorable for the migration of TWPs. This was mainly due to an increase in the negative zeta potentials of the surfaces of TWPs and quartz sand particles in the presence of HA and/or the medium alkaline environment (simultaneously). Also, the dispersion of TWPs was improved for smaller particle size distribution while the electrostatic repulsion between TWPs and quartz sand particles was increased, which contributed to the migration of TWPs. It is worth noting that the migration of C-TWPs prepared by low-temperature crushing was stronger than that of R-TWPs and S-TWPs in the presence of HA and under different environmental pH conditions. This was mainly attributed to the fact that C-TWPs carried a larger negative charge, smaller isoelectric point and stronger hydrophobicity, and these properties also contributed to the adsorption of more HA, thus enhancing their electronegativity. Nevertheless, R-TWPs and S-TWPs had less electronegativity on the surface due to the adhesion of road minerals, metal salts or dust that reduced the magnitude of the mentioned properties.【Conclusion】 These results reveal the variability of the geochemical transport behavior of different types of TWPs in nature and suggest the necessity of studying the source properties (discharge mode) to determine the inherent differences in environmental behaviors and ecological risks of microplastics of the same material.

Abstract:【Objective】 In recent years, more attention has been paid to the persistence of glyphosate and its degradation product, ammethylphosphoric acid (AMPA), in soil, as well as their environmental risks. However, with a similar structure as phosphate and with a positive charge, glyphosate may compete with phosphate for adsorption sites on the surface of soil particles, thereby affecting its environmental behavior and the bioavailability of phosphorus in soil. Our aim was to investigate the degradation kinetics of glyphosate pesticide, soil available phosphorus and soil enzyme activity in Loess soil.【Method】 Laboratory experiments were carried out under different phosphate application levels (0, 50, and 100 mg^.kg^-1) and water conditions (20% field water capacity (20FC) and 60% field water capacity (60FC)).【Result】 The results showed that:1) The degradation rate of glyphosate was fast at the initial stage of spraying and gradually slowed down at the later stage under different levels of phosphate application and soil moisture. Different phosphate levels had no significant effect on glyphosate degradation while different soil moisture did. Also, the content of AMPA increased with the degradation of glyphosate, and there was no significant difference in the content of AMPA under different phosphate levels. However, the peak and variation characteristics of AMPA under different soil moisture significantly differed. The peak was reached on day 14 after spraying for 20FC and on day 7 for 60FC. In addition, the quantitative characteristics of glyphosate residues fitted the first-order kinetic degradation model, with a half-life time of 69.3~77.0 d (20FC) and 10.5~12.8 d (60FC). 2) After spraying glyphosate, the content of available phosphorus decreased first and then increased with the degradation of glyphosate, which was significantly affected by soil moisture. In addition, phosphatase activity was significantly inhibited after glyphosate application, while the activities of N-acetylamino-β-glucosidase, β-glucosidase and leucine aminopeptidase changed dynamically. Phosphate levels showed no significant effects on soil enzymes' activities while soil moisture did.【Conclusion】 The findings indicate that phosphorus level in Loess soil had no significant effect on the degradation characteristics of glyphosate, but soil moisture significantly affected the degradation rate of glyphosate and the residual level of its metabolite. Meanwhile, glyphosate application had a significant effect on the activities of available phosphorus and phosphatase, which may affect soil phosphorus cycling and plant utilization. Therefore, the feed-effects of glyphosate and soil phosphorus components as well as the related enzyme activities should be considered in follow-up studies, especially the relationship between the persistence of glyphosate and its metabolite and soil health indicators under drought conditions. This will provide scientific-based information to guide glyphosate use in Loess soil regions.

Abstract:【Objective】 The aggregation of soil colloids is closely related to the formation of soil aggregates. Fertilization can change the environment of soil solution, and affect the formation of soil aggregates, soil structure and soil mineral composition. It is necessary to explore the relationship between the long-term effects of different fertilization on the microscopic properties and interactions of soil colloids and thus the macroscopic phenomena of soils. 【Method】 Based on a 35-year long-term fertilization monitoring experiment in the experimental station of brown earth, soils treated with no fertilization(CK), nitrogen fertilizer(N), organic fertilizer(M) and the combination of nitrogen fertilizer and organic fertilizer(N+M) were selected as the research objects in this study. Dynamic light scattering technology was used to monitor the dynamic aggregation process of soil colloids with different fertilization treatments. The effects of fertilization treatments on colloid aggregation were comparatively analyzed through the organic matter content, soil mineral composition and surface chemical properties. 【Result】 The soil colloids of the four treatments showed the characteristics of slow aggregation(RLCA) at low electrolyte concentration and fast aggregation(DLCA) at high electrolyte concentration. The order of critical coagulation concentration of four different fertilization treatments was M > N+M > CK > N. Also the long-term application of organic fertilizer increased soil organic matter, thereby increasing the electric field strength near the surface of colloidal particles and the electrostatic repulsion between colloidal particles. Furthermore, the steric hindrance effects of humus weakened the phenomenon of colloid aggregation; On the other hand, long-term fertilization did not change the soil clay mineral composition type, but had an impact on its relative content. The application of organic fertilizer increased the relative content of 2:1 type illite and decreased the relative content of 1:1 type kaolinite. The application of nitrogen fertilizer reduced the relative content of illite and increased the relative content of kaolinite. 【Conclusion】 Different fertilization treatments for a long time changed the basic physicochemical properties and mineral composition ratio of brown earth colloids, which in turn affected the aggregation kinetics of brown earth colloids.

Abstract:【Objective】 This study aimed to clarify the effects of fertilizer and organic fertilizer combined with biomass charcoal on the forms of nutrients and nitrogen in rhizosphere/non-rhizosphere soil, which is helpful for the efficient utilization and scientific management of farmland nitrogen.【Method】 Taking the pot experiment of lemon as the research object, this paper set up six treatments:no fertilizer (CK), chemical fertilizer (CF), manure (M), chemical fertilizer with biomass charcoal (CFB), manure with biomass charcoal (MB) and fresh manure with biomass charcoal (FMB). By measuring the changes of nutrient content in the rhizosphere and non-rhizosphere soils and the transformation of soil nitrogen storage forms, the effects of organic fertilizer combined with biomass charcoal on the forms of soil nutrients and nitrogen in rhizosphere and non-rhizosphere were studied.【Result】 The results showed that compared with CK treatment, MB treatment increased non rhizosphere and rhizosphere soil pH by 0.32 and 0.28 units, and FMB treatment increased rhizosphere soil pH by 0.63 units; MB and FMB treatments increased the content of organic matter in rhizosphere soil by 25.4% and 84.9% respectively, and significantly increased the content of total nitrogen in rhizosphere soil by 25.4% and 50.9%, showing obvious rhizosphere effect. Fertilization can significantly increase the content of soil ion-exchange nitrogen (IEF-N), and CF and CFB treatments had the best effect. Applying manure and biomass charcoal can significantly increase the content of carbonate-bound nitrogen (CF-N) in soil, and M and MB treatments are the best, and CF-N has a rhizosphere enrichment effect. The combined application of biomass charcoal (CFB, MB and FMB) can promote the transformation of soil non-convertible nitrogen (NTF-N) to two more active nitrogen forms, iron manganese oxide bound nitrogen (IMOF-N) and organic sulfide bound nitrogen (OSF-N). IMOF-N and OSF-N account for 35.9%-61.7% and 26.7%-46.6% of convertible nitrogen, respectively, and are the main components of rhizosphere and non-rhizosphere soils convertible nitrogen (TF-N).【Conclusion】 Therefore, manure combined with biomass charcoal is an effective way to improve rhizosphere and non-rhizosphere soil nutrients and regulate nitrogen transformation.

Abstract:【Objective】 Investigating the fate of fertilizer nitrogen in a two-season crop system under different straw returning methods can provide an important basis for nitrogen management under black soil protection.【Method】 This study conducted a ¹⁵N micro-plot experiment in 2020-2021 at Lishu County of Jilin Province using the ¹⁵N tracer technique. Three straw-returning methods were set up:no straw returning(CK), straw deep tillage returning(DTS) and straw mulching with no tillage(NTS). Under each method, two nitrogen levels were set:180 kg·hm^-2(N1) and 270 kg·hm^-2(N2). 【Result】 At maturity stage, 38.0%-46.8% and 12.9%-18.6% of plant nitrogen in the current season and the second season were derived from ¹⁵N labeled nitrogen fertilizer, respectively, and fertilizer nitrogen was mainly distributed in grains (59.8%-68.5% in the current season and 59.3%-79.6% in the second season). The utilization, residual and loss rates of fertilizer nitrogen in the current season were 32.4%-43.9%, 32.8%-51.4% and 13.2%-32.7%, respectively. The NTS combined with an appropriate amount of nitrogen fertilizer (180 kg·hm^-2) significantly increased the utilization rate of fertilizer nitrogen by 29.5%, while DTS significantly increased the residual rate of fertilizer nitrogen in soil by 18.6%. Also, the utilization and loss rates of fertilizer nitrogen in the second season were 8.5%-14.9% and 5.1%-14.6%, respectively. The cumulative utilization, residual and loss rates were 40.9%-58.8%, 10.4%-26.4% and 18.4%-47.3%, respectively. Compared with CK, NTS treatment significantly increased fertilizer nitrogen utilization efficiency by 18.3% (N1) and 45.9% (N2) in the second season, while the DTS treatment significantly increased fertilizer nitrogen utilization efficiency in the second season by 42.3% under N2. For the total fate of fertilizer nitrogen in two crops, compared with CK, NTS treatment significantly increased the cumulative utilization efficiency of fertilizer nitrogen by 26.4% (N1) and 21.8% (N2), while DTS treatment significantly increased the total residual rate of fertilizer nitrogen by 64.0% (N1) and 72.9% (N2). In addition, the NTS and DTS treatments significantly reduced the total losses of fertilizer nitrogen. Compared with N2, the N1 treatment significantly increased the utilization and residual rates of fertilizer nitrogen and reduced the loss rate of fertilizer nitrogen in two seasons.【Conclusion】 Straw mulching combined with an appropriate amount of nitrogen fertilizer is beneficial to improve fertilizer use efficiency while straw deep plowing is more conducive for the maintenance of fertilizer nitrogen in the soil, especially under high nitrogen application rate, and increases the use efficiency by next crop. Both straw mulching and straw deep plowing could significantly reduce nitrogen loss.

Abstract:【Objective】 Phosphorus is an essential nutrient element that affects the growth, yield and quality of crops. Due to the application of a large amount of phosphate fertilizer and the lack of scientific management, the utilization rate of phosphate fertilizer is low and the environmental risk increases. Thus, it is important to know the effects of different amounts of exogenous phosphorus(P) addition on P bioavailability components in paddy soil under flooding conditions.【Method】 Three soil samples were collected from the new paddy field (NP, 2-3 years), medium-term paddy field (MP, 20-30 years) and old paddy field (OP, 400-500 years) in Sunjia small watershed of Yingtan, Jiangxi Province. Based on the flooding culture experiment (0-80 days) with different concentrations of exogenous P addition [0(CK), 125(P1), 250(P2), 500(P3), 625(P4), 750(P5) mg·kg^-1], the test for simulating the bioactivation process of biologically based P(BBP method) was adopted. The dynamic changes in the increment(Δ) of soluble P(Ca-P), easily activated and released P(Ci-P), easily mineralizable acid phosphatase (En-P), and the potential inorganic P(HC-P) were analyzed, and the correlation between all P components and influencing factors were evaluated.【Result】 The results showed that under flooding conditions, exogenous P addition could significantly increase the available P(Bray-P) and BBP components such as Ca-P, En-P, Ci-P and HC-P in paddy soil, and the increment of P contents of each component increased significantly with an extension of P addition. The increment of BBP components was changed by the order:ΔCa-P < ΔEn-P < ΔCi-P < ΔHC-P. On day 15 of incubation, the ΔCa-P and ΔCi-P in the new paddy field reached a maximum value while on day 60, the ΔCa-P, ΔEn-P, ΔHC-P and ΔBray-P in the medium-term paddy field reached their maximum value. However, the P content of each component did not change significantly in the old paddy field. The ratio of ΔBray-P to ΔTP(ΔBray-P/ΔTP) in paddy soil after exogenous P addition showed the same trend as that of ΔBray-P, but there was no significant difference among different P additions. Path analysis showed that exogenous P addition had a significant direct positive effect on ΔBray-P in new and old paddy soil; ΔCi-P had a significant direct positive effect on ΔBray-P in new paddy field; ΔHC-P and ΔCa-P had a significant direct positive effect on ΔBray-P in medium-term paddy field, and ΔEn-P had a significant direct positive effect on ΔBray-P in old paddy field.【Conclusion】 Although exogenous P addition can significantly increase the components of the bioavailability of P in paddy soil, the emergence stage of the maximum increment bioavailability of P in paddy soil is different. Therefore, it is of great significance to timely and appropriately apply P fertilizers for the improvement of P fertility and the risk control of P loss in paddy fields.

Abstract:【Objective】 Soil salinization affects the quality of arable land and threatens the sustainable development of agriculture. As an important indicator of soil environment, soil microbes play important roles in driving soil nutrient cycling and maintaining ecosystem productivity. Therefore, deciphering the response of microbial communities and their potential functions to the degrees of soil salinization and land use type is of great significance for understanding the elemental cycling processes and interactions with plants in a saline-affected agroecosystem.【Method】 In this study, we explored the composition and potential functions of prokaryotic communities and their environmental drivers in saline soils from farmlands and wastelands with different salinization degrees, by combining prokaryotic high-throughput sequencing and soil physicochemical analysis methods in a typical saline area of Hetao Irrigation District of China. 【Result】 Compared with wastelands, the farmlands exhibited a lower soil salinity but a higher content of soil organic matter (SOM) (P < 0.05). In farmlands with different salinity levels, mild saline soil had a significantly higher yield of sunflower than the moderate and severe saline soils. Meanwhile, the saline soils in farmland exhibited a higher prokaryotic α diversity than that in the salinized wasteland, with a large number of unique ASVs (Amplicon sequence variants). The prokaryotic α diversity indexes were positively associated with SOM contents but negatively correlated with soil pH, EC, moisture and bulk density. Non-metric multidimensional scaling (NMDS) analysis based on the β diversity of prokaryotes further indicated that the prokaryotic community was mainly differentiated between farmland and wasteland, followed by the soil salinity level in each land use type. Specifically, the prokaryotic community was dominantly driven by environmental factors including EC, pH and SOM, as suggested by canonical correlation analysis (CCA) and Mantel test. Moreover, the phylum including Acidobacteriota, Chloroflexi, Planctomycetota, Crenarchaeota, and Myxococcota in farmlands showed significantly higher abundance than wastelands, whereas Halobacterota and Bacteroidota showed an opposite trend, with Halobacterota only detectable in wastelands and relative abundance ranging from 10.13% to 39.41%. Through predicting the potential functions of the prokaryotic community, we found that there were high abundances of nitrogen cycling-related microbes like Nitrososphaeraceae and Nitrososmonadaceae, and potential plant growth-promoting bacteria including Nocardioidaceae and Sphingomonadaceae in salinized farmlands. By contrast, the salinized wasteland enriched prokaryotic groups with potential hydrocarbon decomposition function.【Conclusion】 Our study indicates strong selection effects of different land use types on prokaryotic communities in salinized soil of Hetao Irrigation District, which has important implications for clarifying the feedback between prokaryotic community and physicochemical properties of saline soils, as well as revealing the synergy effect among soil-plant-microorganism for soil nutrient turnover and agricultural sustainability.

Abstract:【Objective】 Paddy fields are important anthropogenic sources of atmospheric methane. This study is to investigate the methane production and oxidation potentials and their responses to temperature under different rice-based land use types. 【Method】 Soil samples from four typical land use types in Jurong City, Jiangsu Province, including conventional rice area(CR), rice-crayfish rice area(R-CR), rice-crayfish crayfish area(R-CC) and conventional crayfish area(CC) were collected. Laboratory culture experiments were conducted at 5℃, 15℃, 25℃ and 35℃ for 30 days. 【Result】 The results showed that land use transformation had significant effects on methane production potential and methane oxidation potential. The methane production potential was 1.14 μg·g^-1·d^-1 in the R-CC area, 0.33 μg·g^-1·d^-1 in the CC area, 0.25 μg·g^-1·d^-1 in the R-CR area and 0.17 μg·g^-1·d^-1 in CR area. Also, the values of methane oxidation potential were 1.38 μg·g^-1·d^-1 in the CR area, 1.01 μg·g^-1·d^-1 in the CC area, 1.00 μg·g^-1·d^-1 in the R-CR area and 0.71 μg·g^-1·d^-1 R-CC area. The methane production potential increased exponentially with the increase in temperature. The average values of methane production potential at 5℃, 15℃, 25℃ and 35℃ were 0.13, 0.26, 0.55 and 0.95 μg·g^-1·d^-1, respectively. However, the methane oxidation potential was sensitive only at low temperatures. Specifically, the methane oxidation potential at 15℃, 25℃ and 35℃ were significantly different from the methane oxidation potential at 5℃, while there was no significant difference between the three culture temperatures. The average values of methane oxidation potential at 5℃, 15℃, 25℃ and 35℃ are 0.71, 1.14, 1.14 and 1.11 μg·g^-1·d^-1, respectively.【Conclusion】 Due to differences in water management, feed and nitrogen fertilizer input, substrate and environmental factors led to differences in the activities of methanogenic bacteria and methane-oxidizing bacteria. Therefore, soils with different land use types presented different characteristics of methane production and oxidation potentials. Generally, the methane production potential was more sensitive to temperature than the methane oxidation potential. The soil methane production potential and oxidation potential were significantly affected by temperature or land use type(P < 0.01), but the interaction between the two factors only had a significant impact on soil methane production potential but not on methane oxidation potential.

Abstract:【Objective】 As a by-product of fruit tree shaping and pruning, pear branches are important biomass resources. The use of crushed branches for soil mulch under trees is one of the effective ways to utilize waste resources, which is conducive to increasing soil organic matter and improving soil fertility in pear orchards. 【Method】 In order to assess the effects of short-term pear branch mulching on soil properties and structure of microbial community, soil samples were collected from five pear orchards in different latitudes (Bijie City of Guizhou Province, Changli City of Hebei Province, Harbin City of Heilongjiang Province, Zhijiang City of Hubei Province and Xuchang City of Henan Province) after 1-2 years of mulching. Soil basic physiochemical characteristics of the soil and the bacterial, fungal and protist communities were detected. 【Result】 Results showed that the soil organic matter and available phosphorus content were significantly increased in pear branches mulching treatment in general, and the soil bacterial, fungal and protists community structure also changed significantly. Specifically, the mulching of pear branches significantly enriched the relative abundance of taxa such as Proteobacteria and Acidobacteria in bacteria, Basidiomycota in fungi, and Rhizaria and Alveolata in protists. The model prediction accuracy was as high as 94.44%, and the key species were mainly bacteria, including Acidibacter, Xanthobacteraceae, Nitrosomonadacee and other microorganisms related to the degradation of organic residues. Soil-available phosphorus content was found to be the main driver of variations in soil microbial community structure. 【Conclusion】 The study preliminarily assessed the effect of pear tree branch mulching on soil nutrients and microbiome and excavated potential key microorganisms. The findings can serve as a reference for managing the health and fertility of orchard soils.

Abstract:【Objective】 The frequent redox alternations in paddy soils make the biochemical reactions of different forms of sulfur active, which has a significant influence on rice production.【Method】 This study aimed to explore the characteristics of sulfur cycling pathways in red paddy soils with different parent materials. Also, the influence of parent materials on the characteristics of sulfur cycling pathways, sulfur metabolizing microorganisms, and the main functional microbial communities responsible for each sulfur cycling pathway; including the organic sulfur transformation pathway, other (transfer) pathway, assimilate sulfate reduction pathway, sulfur oxidation pathway, alienation sulfate sulfur reduction approach and disproportionation. 【Result】 The two kinds of parent material developed red paddy soils had the same characteristics of the sulfur cycle pathway. The frequency of microbial functional gene abundance in the organic sulfur transformation pathway was the highest, with an average of 16 000 organic sulfur transformation functional genes detected per million annotated bacterial sequences. Also, the frequency of the abundance of sulfur disambiguation pathway functional genes was the lowest, and only 116 genes were detected per million annotated bacterial sequences. At the level of phylum classification, there was no significant difference in the composition of microorganisms leading the sulfur cycle in the two parent soils. Proteobacteria, Acidobacteria and Chloroflexi were the dominant groups, accounting for 55.19%, 10.61% and 7.18%, respectively. There were significant differences in species classification, and the relative abundance of sulfur-cycling microorganisms in paddy soils developed from granitic parent material was higher. The dominant bacteria in all the channels were the Deltaproteobacteria, Acidobacteria, and Betaproteobacteria, and this abundance accounted for more than 40% of the sulfur-circulating microorganisms in granitic parent paddy soil. However, dominant functional microorganisms involved in each pathway of the sulfur cycle were more abundant in paddy soil developed from Quaternary red clay parent material, for example, Gemmatirosa kalamazoonesis had the highest abundance in organic sulfur transformation pathway while Azoarcus sp. was found in other(transport) pathways. The microorganisms with the highest abundance in the assimilation sulfate reduction pathway are Anaeromyxobacter sp. 【Conclusion】 The same sulfur cycling pathway was observed in paddy soils derived from red earth with two different parent materials. There was no significant difference in the dominant sulfur-cycling microorganisms in paddy soils derived from red earth with two parent materials at the phylum level. However, there were significant differences in species-level classification, indicating that there is unique dominant sulfur transformation functional flora in soils of different parent materials.

Abstract:【Objective】 The use of arbuscular mycorrhizal fungi (AMF) to obtain nutrients from agricultural ecosystems is an effective way for red soil crops to acquire soil phosphorus (P). Given the problems of biological function degradation, low phosphorus bioavailability, and low crop yield in red soil in southern Southern China, how to regulate the AMF community in the rhizosphere of crops and optimize the mutualistic symbiotic relationship with the host is the key to breaking the bottleneck of crop phosphorus uptake in the red soil regions.【Method】 In this study, four diversified fertilization measures were combined with ecological intercropping in red soil dryland with organic (straw, pig manure, bio-fertilizer) and inorganic fertilizers, and the optimal fertilization mode was screened based on crop yield and phosphorus activation level in red soil. Further, we used amplicon high-throughput sequencing and microscopic observation techniques to analyze the effect of optimal fertilization measures in red soil dryland on the composition of the AMF community. Also, a deduction of the mechanism through which the optimized AMF community stimulates the host maize phosphorus uptake was performed.【Result】 The results showed that the organic-inorganic application of peanut/maize intercropping combined with straw/biofertilizer (In+NPKSB) increased total phosphorus (TP) and available phosphorus (AP) by 29.07% and 1.35 times in red soil dryland compared with maize monocropping combined with conventional fertilizers (Mo+NPK). Moreover, the relationship between AMF family levels in maize roots was enhanced.The AMF colonization rate of this measure was 2.24 times higher than that of the traditional fertilization measures, the activities of acid/alkaline phosphatase (ACP/ALP) in the maize rhizosphere were increased by 32.18% and 41.66%, and maize biomass and yield was increased by 34.98% and 67.27%, respectively.【Conclusion】 The study confirmed that the fertilization measures of peanut/maize ecological intercropping in red soil dryland combined with the organic and inorganic application of straw/bio-fertilizer can optimize the AMF community composition in maize roots, activate soil phosphorus availability, and improve the phosphorus transport efficiency of host roots. This study, therefore, provides a theoretical basis for promoting the integrated application of sustainable agricultural development in red soil dryland according to local conditions.