Abstract:Abstract：[Objective] With the intensification of human activities since the Industrial Revolution, there is a continuous rise in carbon dioxide concentration ([CO2]) in the atmosphere, which has become the main feature of global climate change. Rice being an important staple crop, it is important to explore its absorption and distribution of phosphorus under a long-term elevated CO2 environment. [method] In this study, a multigenerational experiment was carried out cultivating Yangdao 6 (indica) and Wuyungeng 23 (japonica) in the Free Atmospheric CO2 Enrichment System (FACE) in Changshu, Jiangsu Province. The experiment was carried out under ambient [CO2] and elevated [CO2] (increased by 200 μmol?mol-1) conditions for seven generations, and the differences in phosphorus concentration, phosphorus uptake, and phosphorus distribution ratio between the single-generation and multigenerational rice plants were evaluated. [Result] (1) Long-term elevated [CO2] had no significant effect on the phosphorus concentration of multigenerational rice plants in Yangdao 6 and Wuyungeng 23. (2) The long-term elevated [CO2] significantly increased the phosphorus uptake of shoots in single-generation and multigenerational rice plants. However, the average increase in phosphorus uptake of the shoot and panicle of the offspring plant of Yangdao 6 was lower than that of the single-generation plant. On the contrary, the average increase in phosphorus uptake of shoot, straw, and panicle of the offspring plant of Wuyungeng 23 was higher than that of the single-generation plant under elevated [CO2]. (3) The average increasing effect of elevated [CO2] on the distribution ratio of phosphorus in the straw of Wuyungeng 23 increased significantly with the increase in generations of maternal seeds under elevated [CO2] treatment. [Conclusion] The results indicate that in the past, based on the single-generation short-term FACE studies, the real effect of long-term elevated [CO2] on phosphorus uptake and distribution in rice plants could not be accurately predicted in the future. Therefore, this study provides guidelines for field-level phosphorus fertilizer management in a future high-CO2 world.

Abstract:Delving into the impacts of reduced chemical fertilizers (RCF) and organic fertilizer substitution (OFS) on soil organic carbon (SOC) is crucial for understanding the response processes of agricultural SOC pools to fertilization and achieving sustainable agricultural development early. This study aims to explore the impacts of RCF and OFS on SOC under different climatic conditions, initial soil properties, and land use patterns. Furthermore, it endeavors to estimate the key influencing factors and clarify the natural and anthropogenic conditions conducive to SOC accumulation.【Method】After collecting and sorting out 142 published literature, we analyzed the variation characteristics of SOC content under RCF and OFS using meta-analysis. Thereafter, the influence degrees of various factors on SOC were systematically investigated by the Random Forest Model.【Result】The results revealed that SOC decreased by 2.61% on average under RCF. Notably, greater SOC losses were observed in temperate regions (with annual mean temperature < 10°C and annual mean precipitation < 1000 mm), whereas SOC losses were not significant with changes in altitude. Soils with high initial SOC content favored SOC retention. With soil’s initial pH and available phosphorus content increasing, the overall loss of SOC tended to intensify, with the highest SOC reduction reaching 6.91%, however, the effect of initial available potassium was the opposite. The declines in SOC under RCF were similar in farmland and orchards, while changes in SOC in vegetable fields were not significant. In contrast, SOC significantly increased by 14.39% under OFS, with subtropical regions at low to medium altitudes and annual precipitation < 600 mm being more conducive to SOC accumulation. Except for low levels of initially available nitrogen (50 mg·kg-1), no significant differences in SOC were observed among soils with different initial SOC, total nitrogen, and available nitrogen contents. With initial pH and available phosphorus content increasing, the cumulative effect of SOC enhanced, whereas the effect of initially available potassium was the opposite. Among different land use types under OFS, paddy-upland rotation and vegetable field utilization were most favorable for SOC accumulation.【Conclusion】Under the two fertilization systems, the climatic and environmental conditions in subtropical regions are more conducive to SOC sequestration. Compared to the subsurface soil, the impact of RCF and OFS on SOC in the surface soil was more significant. The decline in SOC of RCF was similar in both farmland and orchards, while the change of SOC in vegetable fields was not significant. In contrast, paddy-upland rotation and vegetable fields were the most favorable practices for SOC accumulation under OFS. Additionally, pH and initially available nitrogen were the most critical factors influencing the changes in SOC with RCF and OFS, respectively. These research results are of great significance for achieving carbon neutrality and sustainable development in agriculture as soon as possible.

Abstract:Abstract: 【Objective】 As important carbon sources and sinks in terrestrial ecosystems, the accumulation process of paddy soil organic matter (SOM) is relatively well understood. However, changes in the molecular composition of SOM within soil aggregates and the mechanisms underlying SOM accumulation remain unclear.【Method】This investigation employed a paddy soil chronosequence in Cixi, utilizing Fourier Transform Infrared Spectroscopy (FTIR) and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM). These methods were implemented to elucidate the variation patterns of SOM molecular components across different aggregate sizes and their contributions to SOM sequestration processes within the paddy chronosequence.【Result】Our findings revealed distinct temporal patterns in soil organic carbon (SOC) dynamics. Both macroaggregates (>250 μm) and microaggregates (<250 μm) exhibited rapid SOC accumulation within the initial century, followed by a gradual stabilization. Aliphatic SOM components demonstrated a substantial decrease from 12%-13% to 1% within the first 100 years of rice cultivation, while aromatic SOM components showed a progressive increase from 16%-17% to 30%-38%. In dissolved organic matter (DOM) fractions, tryptophan-like DOM increased from 16%-17% to 33%, whereas fulvic acid and humic acid components decreased from 41%-42% to 36%-37% and 31%, respectively, subsequently maintaining relative stability. The fluorescence index (FI) and autochthonous index (BIX) of DOM displayed an initial increase followed by a decrease, while the humification index (HIX) showed the opposite trend. These observations suggest an initial period of microbial activity characterized by high metabolic substance content, followed by microbial community stabilization and continuous production of complex humic substances during prolonged rice cultivation.【Conclusion】Despite relatively minor differences in SOC molecular components across various aggregate sizes under extended rice cultivation, our results substantiate that SOC accumulation in paddy fields is influenced not only by chemical adsorption and physical protection within soil aggregates but also significantly by microbial transformations. These findings contribute to a comprehensive understanding of SOC accumulation mechanisms in paddy soils and provide valuable insights for enhancing soil fertility sustainability.

Abstract:【Objective】Soil colloid stability plays an important role in soil nutrient retention, structure formation and crop growth. The application of organic materials is an effective method for improving saline-alkali soil, but their effects on soil colloid stability in these conditions remain unclear.【Method】In this study, we investigated the effects of biochar (BC), cattle manure (CM), and maize straw (MS) on soil colloid stability at different salinity-alkalinity levels (non-saline-alkali, mild saline-alkali and moderate saline-alkali) through soil incubation and sedimentation experiments in the laboratory.【Result】(1) The addition of organic materials significantly reduced the diameter of saline-alkali soil colloidal particles, making it similar to the diameter of non-saline-alkali soil colloid. In mild saline-alkali soil, the effect of MS treatment was most effective, and the colloidal particles size decreased from 785.7 nm to 360.2 nm. In moderate saline-alkali soil, the effect of CM treatment was most effective, decreasing the colloidal particles size from 675.8 nm to 393.6 nm. (2) The stability of soil colloid is related to the degree of soil salinity. Compared with non-saline-alkali soil and mild saline-alkali soil, moderate saline-alkali soil colloid exhibited significantly high stability, likely due to elevated high pH and high alkalinity. (3) Organic materials had minimal effect on the colloid stability of non-saline-alkali soil and mild saline-alkali soil. However, CM and MS treatments significantly reduced the colloid stability of moderate saline-alkali soil, causing colloidal particles agglomerated. Therefore, in moderate saline-alkali soil, the application of cow manure and maize straw may be more effective than biochar for stability improvement.【Conclusion】The application of organic materials ameliorates the basic physicochemical properties of saline-alkali soil and optimizes the state of soil colloid. Compared with biochar, cattle manure and maize straw, due to their rich functional groups and nutrients, significantly reduced the colloid stability of moderate saline-alkali soil upon application, thereby inducing colloidal aggregation and promoting the formation of microaggregates.

Abstract:【Objective】 The soil organic carbon (SOC) pool is the largest carbon reservoir in terrestrial ecosystems, playing an essential role in mitigating climate change and maintaining soil fertility. Among the various components of SOC, microbial necromass carbon (MNC) constitutes a significant proportion, contributing approximately 30-80% to the total SOC, and playing a crucial role in stabilizing soil carbon stocks. Accumulation and stabilization of MNC in soil are closely linked to the formation and stability of soil aggregates, which provide physical protection against microbial decomposition. Despite the known connection between MNC and soil aggregation, no comprehensive studies have systematically explored the relationship between MNC and soil aggregate stability. This study aims to further explore the global association between MNC and soil aggregate stability.【Method】 To assess the relationship between MNC and soil aggregate stability, we compiled global observational datasets on soil amino sugars (biomarkers of MNC) and soil aggregates. Using machine learning techniques, we predicted the global distribution of MNC and analyzed its correlation with the stability of soil aggregates. The PLS-PM was employed to further investigate the pathways through which soil aggregate stability influences MNC sequestration, takin into account factors such as soil physical properties, nutrient availability. 【Result】 The results revealed that MWD is a key predictor of MNC, with a significant positive correlation between MNC and MWD on a global scale (P < 0.05). Further correlation analysis of global prediction data confirmed this relationship and showed that it is consistent across different ecosystems. The Partial Least Squares Path Model (PLS-PM) analysis revealed that soil aggregates protect MNC directly by forming physical barriers and indirectly by regulating soil physical properties and nutrient availability, which in turn influence MNC accumulation and stabilization. In particular, soil nutrients had the most significant positive impact on MNC (path coefficient = 0.67, P < 0.05). The process through which MWD influences MNC shows significant differences across different ecosystems, specifically in terms of the direction and strength of the pathways. For example, in agricultural ecosystems, the indirect effects through soil physical properties and nutrients are more pronounced, while in forest ecosystems, the direct effect is stronger. 【Conclusion】The findings of this study underscore the significant role of soil aggregates in stabilizing MNC, and highlight the potential of soil aggregation as a key factor in enhancing soil carbon storage. Also, the positive correlation between MNC and aggregate stability suggests that strategies aimed at improving soil structure; eg., practices that enhance aggregation and optimize nutrient management, can effectively contribute to greater carbon sequestration. By fostering more stable soil aggregates, we can improve MNC sequestration, mitigate climate change, and sustain soil fertility. Furthermore, these findings can inform the development of predictive models for MNC sequestration and the integration of soil aggregate stability as a critical indicator for assessing the carbon sequestration potential of soils.

Abstract:【Objective】Salinization leads to a decline in soil fertility and reduced agricultural productivity, significantly limiting the high-quality development of arid region agriculture. Bioorganic materials have shown promising effectiveness in land reclamation for salt-alkali-affected areas. 【Method】The effects of adding different biomass materials (8‰ biochar (B), 8‰ biochemical fulvic acid (BF), and a mixture of 4‰ biochar and 4‰ biochemical fulvic acid (BBF)) on the physicochemical properties and water-salt transport characteristics of soda saline-alkali soil was investigated, through one-dimensional vertical infiltration experiments. Each layer of soil was completely mixed with bioorganic materials and subjected to an equal volume treatment. 【Result】The results showed that the application of biochar and biochemical fulvic acid both significantly reduced soil bulk density and increased porosity, with significant differences between treatment B and other treatments (P<0.05). Under the same infiltration time,the wetting front depth of B, BF, and BBF treatments was significantly smaller than that of the CK, with the BF treatment showing the smallest wet front migration depth. Both the Kostiakov and Philip models could effectively simulate the infiltration process, and the infiltration rate (S) showed a variation pattern of CK > B > BBF > BF. The B, BF, and BBF treatments significantly increased the soil volumetric water content in the 0-15 cm soil layer, with significant differences among the treatments (P<0.05). At the 15 cm soil depth, the soil salt content in the B, BF, and BBF treatments was higher than that in the CK, and the soil salt content in the 20-30 cm soil layer gradually increased with depth. The BF treatment showed the most significant effect on salt content. Also, the soil pH in all treatments was lower than the initial pH, but in the 0-15 cm soil layer, the pH of the B, BF, and BBF treatments was higher than that of the CK. Additionally, the concentration of soil salt ions in the 0-15 cm soil layer was higher compared to CK, especially the water-soluble Na+ concentration, which significantly increased. 【Conclusion】The result indicates that bioorganic materials, such as B and BF, exhibit significant effects in land reclamation for salt-alkali affected areas by significantly reducing soil bulk density and increasing porosity. Additionally, these materials decreased infiltration rates while enhancing cumulative infiltration, though increased Na? concentrations may affect long-term outcomes. Therefore, when improving salt-alkali soils, emphasis should be placed on considering the physical properties of bioorganic materials. It is recommended to select materials with suitable physical properties and low sodium content, followed by salt leaching treatments, to optimize land reclamation efforts.

Abstract:【Objective】 Biochar and diatomite have gained considerable attention as soil amendments; however, their effects and underlying mechanisms on nitrification processes as well as ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in coastal saline soils remain poorly understood. 【Method】 A 42-day indoor incubation experiment was conducted using typical coastal saline soil from the Yellow River Delta. Five treatments were applied: control without fertilizer (CK), urea (U), urea with dicyandiamide (DCD), urea with diatomite (DE), and urea with biochar (BC). The effects of these treatments on soil nitrification were evaluated, and the abundance and community structure of AOA and AOB were analyzed using quantitative PCR and high-throughput sequencing. 【Result】 The results demonstrated that DCD significantly inhibited nitrification in the short term, with an inhibition rate of 73.1%, however, its inhibitory effect diminished over time. Biochar also showed short-term nitrification inhibition but subsequently promoted AOA abundance. In contrast, diatomite did not significantly inhibit nitrification but notably enhanced AOB abundance. Correlation analysis revealed that the amoA gene abundances of AOA and AOB exhibited significantly opposite regulatory effects on the nitrification process. AOA showed significant positive correlations with ammonium nitrogen (NH??-N) content and nitrification inhibition rate (NIR), but a significant negative correlation with nitrate nitrogen (NO??-N) content. Conversely, AOB demonstrated significant negative correlations with NH??-N content and NIR, but highly significant positive correlations with NO??-N content and net nitrification rate (NNR). Notably, the correlation between AOB and NNR was significantly stronger than that of AOA. Cluster analysis indicated that the community structures of AOA and AOB in the BC and DCD treatments were more similar, which may be related to the fact that both regulate the soil nitrogen transformation process and microbial activity. 【Conclusion】 This study elucidates the differential regulatory mechanisms of biochar and diatomite on ammonia-oxidizing microbial communities in coastal saline soils, offering a novel theoretical foundation for the amelioration of saline soils.

Abstract:【Objective】The rhizosphere is the interface between plants and soil, and plants affect the composition of soil microbial communities by secreting root exudates, while rhizosphere microorganisms can affect plant physiology and development through multiple mechanisms. Therefore, the development of accurate and applicable root exudate and soil sample collection methods are very important in understanding the ecological process of plant root-soil interface. However, the in-situ collection of rhizosphere soil and root exudates remains understudied. 【Method】This paper introduced a novel device for the in-situ dynamic visualization and accurate collection of rhizosphere soil and root exudates. The device comprises a plant growth compartment, a root growth compartment, a soil compartment, and a root exudate sampling system. The device is designed by partitions, planting seeds or seedlings in the plant growth compartment, allowing the root system to extend into the lower root growth compartment through a slit at the bottom. Also, the nylon membrane isolates the soil from the root system to ensure a two-way pure exchange. On the one hand, it allows soil nutrients to infiltrate, ensuring normal plant growth, and on the other hand, it prevents particle contamination. At the same time, a multi-interface connected sampling system is set up to realize the accurate partition collection of root exudates. The sampling process is automated, with a vacuum pump controlled by a solenoid switch and a program to regularly rinse and extract secretions into the sampling bottle. For soil sampling, the depth and distance from the root system are flexibly selected, and the soil quantity is estimated by the sampling tube scale to ensure the accuracy and comprehensiveness of the experimental data. For validation, root exudates of wheat during the grain-filling stage were collected by both the device collection method and the solution collection method. The content of quercetin in the root exudates was determined by high-performance liquid chromatography. A standard curve was prepared using quercetin as the standard substance, and the content of quercetin in the root exudates was calculated. 【Result】This device innovatively integrated the functions of plant growth, root exudates sampling and rhizosphere soil collection. It realized the accurate, in-situ, continuous and dynamic collection of plant root exudates and rhizosphere soil through ingenious design, and the collection range could be accurately concentrated in the root system and the soil environment in the same area, so as to ensure the simultaneous collection of exudates and rhizosphere soil. During collection of root exudates, the content of quercetin obtained by the device collection method was close to that by the solution collection method, and it eliminated the cumbersome operations such as root stripping, supported continuous sampling at multiple time points for the same plant, and significantly improved the research efficiency of individual plants. Moreover, this method ensured the normal growth of plants, and there was no interference with soil components, and provided high accuracy. 【Conclusion】This device, with its comprehensive functions, provides efficient sampling capacity and precise control mechanism, and can serve as a powerful tool in the field of plant physiological ecology, and is conducive for promoting the in-depth development of soil microbiology research.

Abstract:Soil serves as a crucial terrestrial reservoir of organic carbon, plays a significant role in mitigating climate change and ensures sustainable agricultural production. Iron oxides, as important active components in soil, are integral to the stabilization and turnover of soil organic carbon. These oxides interact with organic carbon through processes such as adsorption, co-precipitation, and other mechanisms, forming relatively stable iron-carbon complexes. Additionally, iron acts as a catalyst in the polymerization of organic carbon, facilitating the transformation of organic carbon into more stable forms via the Maillard reaction. However, these protective functions of iron oxides can be modulated by environmental factors, which may reduce their effectiveness under fluctuating conditions. During redox cycling of iron, iron oxides can also accelerate the organic carbon turnover by releasing reactive oxygen species and transferring electrons. This review provides a systematic examination of the mechanisms by which soil iron oxides influence carbon turnover and sequestration, while also exploring the reciprocal effects of organic carbon on iron cycling. This study further evaluates the role of environmental factors and key biological processes in regulating iron-carbon cycling. Particular emphasis is placed on the critical roles of mineral protection and biological activity constraints in maintaining soil carbon pool stability. Finally, the review proposes several directions for future research in the iron-carbon field. These include the verification and quantification of soil organic carbon polymerization reactions, understanding the regulatory role of soil microzone biological processes on iron-carbon coupling, exploring the trade-offs between organic carbon fixation and morphological transformation during iron redox processes, and integrating a cross-scale model for iron-carbon coupling and carbon sink potential assessment. Conducting these studies will facilitate the accurate analysis of physical-chemical-biological mechanisms of soil iron-carbon coupling and furnish insights to promote a more profound understanding of iron-carbon dynamics and formulate strategies for enhancing soil carbon sequestration.

Abstract:【Objective】Purple soil is a soil type unique to China, characterized by rapid weathering of the parent material, low permeability, and poor erosion resistance. A large number of slope conversions have been adopted to combat soil erosion, but the synergistic effect of this measure with crop types on the local organic carbon pools of sloping arable land and their composition is not clear. 【Method】In this study, Corn Slope, Corn Terracing, Citrus Slope, Citrus Terracing, Corn-Citrus Terracing in the East River sub-basin in Chongqing were selected as the research objects. Biomarker methods were used to compare the differences in soil microorganisms and organic carbon of plant origin from different types of sloping arable land and to reveal the effects of slope-to-staircase measures on soil organic carbon pools and their compositions.【Results】The results showed that: 1) The contents of SOC, POC, and MAOC in different types of sloping arable land was significantly decreased with the implementation of slope reclamation measures; 2) Slope reclamation significantly decreased the total lignin phenol content in maize sample plots compared to the significant decrease in the degree of oxidation of lignin phenol in citrus sample plots; 3) The main source of microbial organic carbon in all sample plots was fungal residue, which accounted for 74.50%~98.88%, and the slope conversion measures decreased the fungal content in the soil under the monocrop planting mode. 【Conclusion】Although slope conversion measures helped to reduce soil erosion, they had a complex impact on the soil organic carbon pool and its composition in sloping arable land in the purple soil zone. This provides a scientific basis for optimising agricultural management practices and achieving sustainable land use in the purple soil zone.

Abstract:【Objective】Soil salinization seriously restricts the sustainable development of agriculture, and the accurate monitoring of soil salinity is crucial for agricultural management and ecological protection. This study combined unmanned aerial vehicle (UAV) imaging spectroscopy with machine learning algorithms to explore the inversion and spatial mapping of soil salt content (SSC) in coastal areas.【Method】Feature bands were selected using the Competitive Adaptive Reweighted Sampling (CARS) algorithm, and spectral indices were calculated. Spectral indices were selected using the Recursive Feature Elimination (RFE) method. Utilizing PLSR, SVR, and RFR, this study developed prediction models for all spectral bands based on six different spectral transformations, and spectral index prediction models were built using SVR, RFR, XGBoost, and BPNN. The best model was chosen for SSC spatial mapping through accuracy evaluation.【Result】The results showed that the measured soil salt content (SSC) in the study area ranged from 1.23 to 8.96 g kg?1, with a mean of 3.12 g kg?1. Among the full-spectrum models, the random forest regression (RFR) model based on raw spectra processed with Savitzky-Golay (SG) smoothing demonstrated the highest accuracy. For the spectral index models, the extreme gradient boosting (XGBoost) model with feature selection performed the best. The inversion results revealed that low-to-moderate soil salinity was widely distributed across the study area, with high salinity values scattered sporadically. While XGBoost was well-suited for predicting the overall spatial distribution of soil salinity, the RFR model based on SG-smoothed raw spectra was more effective for mapping areas with low salinity.【Conclusion】This study innovatively combined full-spectrum optimized spectral indices with traditional ones to build a SSC prediction model, offering a new technical path for rapid SSC monitoring in coastal regions using UAV imaging spectroscopy.

Abstract:Soil microbial community drives biogeochemical cycles and is crucial for maintaining soil health and ecosystem sustainability. However, the complexity of microbial community composition and the diversity of microbial functions present significant challenges in classifying and understanding microbial community based on functional traits. Life history strategy theory links microbial metabolic characteristics with ecological processes, providing critical insights into the relationship between microbial communities and ecosystem services. This review systematically summarizes the theoretical frameworks and recent advances in soil microbial life history strategy, outlining the original theories and their developmental trajectory. It focuses on the two-way continuum (r-K life history strategy theory and oligotrophic-copiotrophy life history strategy theory) and the three-way continuum (C-S-R and Y-A-S life history strategy theories), highlighting their conceptual foundations and practical applications in soil microbial community researches. However, current studies primarily rely on descriptive analyses of microbial functional composition, lacking investigations into the dynamic expression and regulation mechanisms of microbial functions. Based on this, we propose future research directions on soil microbial life history strategies to support sustainable agriculture. First, integrating multi-omics technologies is essential for assessing the functional dynamics of microbial community. While current sequencing methods (e.g., amplicon and metagenomic sequencing) can identify potential microbial functions based on the genomic information, they fail to capture real-time microbial activity in fluctuating environments. A combined approach incorporating transcriptomics, proteomics, metabolomics, and single-cell Raman spectroscopy can provide deeper insights into real-time gene expression, metabolic processes, and other critical aspects of soil microbial communities. Second, elucidating the molecular mechanisms that regulating the microbial life history strategies is crucial. Microbes dynamically reprogram their functional traits in response to environmental changes, yet the signaling networks and genes governing this reprogramming remain largely unknown. Future research should focus on understanding the interactions among environmental factors, microbial gene expression, and microbial functional investments. Additionally, synthetic biology approaches can facilitate the engineering of programmable microbial strains, enabling precise control over microbial functions in complex ecosystems. Third, expanding current life history strategy theories to incorporate species interactions within ecosystems is necessary. Existing frameworks primarily emphasize microbe-environment interactions while neglecting biotic interactions, particularly in agricultural ecosystems. For example, rhizosphere microbes enhance plant stress resistance and growth by producing plant hormones such as cytokinins, yet these functions are not currently integrated into life history strategy frameworks. Future studies should explore how microbial life history strategies regulate soil-microbe-plant interactions and quantify their contributions to ecosystem services. We emphasize the need to establish a multidimensional, dynamic analytical framework for microbial life history strategies, elucidate the driving mechanisms underlying microbial life history transitions, and refine the response framework of soil microbial life history strategies in agricultural ecosystem services. We advocate for developing microbial life history classification into a core theoretical tool for ecosystem function regulation, providing microbiome-based solutions to address global change and food security challenges.

Abstract:[Objective] Biochar plays an important role in improving soil physicochemical properties and enhancing soil structural stability. It achieves this by increasing soil organic matter content, enhancing nutrient retention and availability, and improving soil structure changes that further promote soil aeration, water infiltration, and root penetration, thereby strengthening soil structural stability. Soil structural stability is critical for sustainable agricultural production, as it influences soil erosion resistance, water-holding capacity, and overall soil health. However, few studies have explored the effects of biochar addition on the mechanical stability of soil structure from the perspective of rheological methods. [Methods] To address this research gap, a two - year field experiment was conducted. Soil samples with different biochar addition rates (0%, 1%, 3%, 5%, and 10%) were tested for basic physicochemical properties. Additionally, amplitude sweep tests were used to measure soil shear strength and viscoelastic parameters under varying water contents (30%, 37.5%, 45%, and 60%), aiming to analyze how biochar addition levels affect the shear strength and viscoelastic properties of the soils. The amplitude sweep mode is a robust rheological technique that allows for the assessment of soil behavior under different deformation conditions, providing valuable insights into soil mechanical stability. [Results] The results showed that biochar addition significantly improved soil structural mechanical stability by enhancing soil basic physicochemical properties, such as increasing soil cation exchange capacity and organic carbon content, which in turn increased soil energy storage modulus and shear strength This effect was particularly pronounced at lower water contents ranging from 30% to 37.5%. At these water contents, the soil structure was more stable and better able to resist external forces. Furthermore, biochar addition also resulted in an increased range of the linear viscoelastic zone and higher soil yield stress, thereby improving its structural stability. Notably, at a 10% addition rate, the soil maintained strong stability even under high water content conditions. [Conclusion] Biochar addition enhances the mechanical stability of soil structure by improving soil shear strength and viscoelasticity. These findings clarify the mechanical mechanism underlying soil structure improvement via biochar application, and thus provide a scientific basis for formulating targeted soil structure optimization measures in the Loess Plateau region.

Abstract:The aim of this study was to explore the long-term effects of biochar on improving soil fertility in farmland in the northern Xinjiang irrigation area. A three-year field trial with three treatments: no biochar application (B0), low biochar application (10 thm-2, B1), and high biochar application (20 thm-2, B2), was conducted to systematically analyze the effects of biochar on soil aggregate carbon and nitrogen components, enzyme activities, and microbial community structure. The results showed that when the biochar application rate was 10 t·hm-2, it exhibited the optimal soil improvement effect. Specifically, the organic carbon content in aggregates larger than 2 mm and smaller than 0.25 mm demonstrated an upward trend with the application of biochar. Among them, in the aggregates larger than 2 mm, the organic carbon content in treatment B1 was significantly increased by 44.05% compared to treatment B0. In the aggregates smaller than 0.25 mm, the organic carbon content initially increased and then decreased with the application of biochar, reaching the maximum in B1. Also, the total nitrogen content in aggregates larger than 2 mm first increased and then decreased with the application of biochar, reaching the highest level in B1. Furthermore, the findings indicated that the application of biochar increased the microbial biomass carbon and nitrogen in aggregates larger than 2 mm and in the range of 2~0.25 mm, while reducing the microbial biomass nitrogen in aggregates smaller than 0.25 mm. Meanwhile, the urease activity in all three types of aggregates showed an upward trend with the application of biochar. Under the three aggregate conditions, compared to B0, B1 increased the activity of urease by 14.53%, 5.43%, and 1.08%, respectively. In addition, catalase activity was highest under the B1 condition, increasing by 10.64%, 21.43%, and 23.4% compared to B0, respectively. Although sucrase activity slightly decreased, it still remained at a relatively high level, ensuring the supply of carbon sources. The application of biochar significantly enhanced the α-diversity (Shannon and Chao1 indices) of the soil bacterial community. This promoting effect was strengthened as the aggregate particle size decreased. Moreover, under the application rate of 10 t·hm-2 (B1), the improvement effect was relatively balanced. In contrast, the impact of biochar on the α-diversity of fungi was relatively weak. The Shannon index only increased slightly, and the Chao1 index showed no significant change, indicating that the fungal community was less sensitive to the application of biochar compared to the bacterial community. Under the conditions of this study, applying 10 t·hm-2 of biochar (B1) can increase the content of carbon and nitrogen components in soil aggregates of wheat fields while enhancing the abundance of beneficial microbial communities.

Abstract:【Objective】Soil organic carbon (SOC) in cropland is an important component of the terrestrial ecosystem carbon pool. The application of organic manure, as a critical agricultural management practice, has been extensively validated to significantly enhance soil organic carbon (SOC) content and stock. However, Current research mainly focuses on the SOC fixation and mechanisms in the 0~20 cm surface soil layer, with little attention given to the carbon sequestration potential of deeper soil layers. 【Method】This study used a meta-analysis method to systematically analyze the impact of animal manure application on SOC distribution and stock in the soil profile of global croplands. 【Result】The results showed that the application of animal manure increased SOC stock in different soil layers. In the surface layer (0~20 cm), SOC stock increased from 28.3 t·hm-2 to 36.4 t·hm-2, with an increase of 28.6%. In the 20~40 cm layer, SOC stock increased from 23.6 t·hm-2 to 27.5 t·hm-2, with an increase of 16.5% while in the >40 cm layer, SOC stock increased from 45.6 t·hm-2 to 48.7 t·hm-2 (6.8%). The new SOC sequestration efficiency (NCE) was highest in the 0~20 cm layer (146.0%), significantly higher than in the 20~40 cm layer (117.2%) and the >40 cm layer (64.3%). Also, it was observed that soil carbon sequestration efficiency was co-regulated by both natural factors (annual mean temperature, annual mean precipitation) and anthropogenic factors (fertilizer type, nitrogen application rate, land use type, and application duration). Specifically, the impacts of annual mean temperature and annual mean precipitation on sequestration efficiency vary across different soil layers. Moreover, the combined application of animal manure and an appropriate amount of nitrogen fertilizer significantly enhanced SOC stock in the surface soil layer. 【Conclusion】This study provides a theoretical basis for developing differentiated carbon sequestration strategies based on soil profile characteristics. Furthermore, the study highlights the significance of optimizing agricultural management to enhance soil carbon stock, mitigate climate change, and achieve sustainable agricultural development.

Abstract:The Sodium Adsorption Ratio (SAR) is a critical indicator for characterizing the hazard of sodium ions and the degree of soil sodification in saline-alkali soils. However, in the coastal region of Hebei, the characteristics and key influencing factors of soil SAR remain unclear due to unique processes of salt formation and accumulation, as well as complex physicochemical interactions, which hinders its accurate prediction.【Objective】This study aims to elucidate the spatial distribution and profile variation patterns of SAR in representative coastal saline-alkali soils of Cangzhou, Hebei; to identify and quantify the key soil physicochemical factors influencing SAR dynamics. Also, the study seeks to develop and select an optimal machine learning model for accurately predicting SAR based on easily measurable parameters.【Method】Taking typical coastal saline-alkali land in Cangzhou City, Hebei Province as the research area, soil samples were collected from two layers (0–20 cm and 20–40 cm). A comprehensive set of properties was measured, including ionic composition, bulk density (BD), soil water content (SWC), soil organic matter (SOM), total porosity (STP), capillary porosity (SCP), saturated hydraulic conductivity (Ks), electrical conductivity (EC), and pH. The characteristics of SAR were analyzed, its main influencing factors were explored, and four machine learning models: Linear Regression (LR), Decision Tree (DT), Random Forest (RF), and K-Nearest Neighbors (KNN), were used to predict SAR. Model performance was evaluated using the coefficient of determination (R2) and Root Mean Square Error (RMSE).【Result】The mean SAR values in the upper (0–20 cm) and lower (20–40 cm) layers were 22.23 and 28.02, respectively, with no significant difference (P = 0.126). The soil in the study area was classified as moderately saline-sodic soil. Correlation analysis revealed that SAR was significantly correlated with K?, Cl?, SO?2?, EC, pH, BD, HCO??, SOM, SWC, STP, SCP, and Ks. Among these, the correlations with Cl?, SO?2?, and EC were the strongest, identifying them as the primary influencing factors. In the comparison of SAR prediction models, a model using both EC and pH as predictors achieved higher accuracy, and the RF model demonstrated the best predictive performance, with soil EC being the most significant feature.【Conclusion】The RF model can achieve robust prediction of SAR in the coastal saline-alkali soils of Hebei based on easily measurable indicators such as EC and pH. This study identified the key driving factors of SAR in the region and developed an effective predictive framework, providing a scientific basis and practical tools for the precise reclamation and sustainable utilization of local saline-alkali lands.

Abstract:【Objective】This study aimed to explore the effects of applying different amounts of wood vinegar in combination with sheep manure on the improvement of saline-alkali soil in the low plain of Hebei and the salt tolerance of winter wheat from 2022 to 2024. 【Method】There were five treatments including conventional fertilization (CK), sheep manure at 27 t?hm-2 (T0), T0 + wood vinegar at 270 kg?hm-2 (T1), T0 + wood vinegar at 540 kg?hm-2 (T2), and T0 + wood vinegar at 810 kg?hm-2 (T3). The effects of the combined application of sheep manure with different amounts of wood vinegar on soil nutrients, salt tolerance characteristics of winter wheat, nutrient absorption and utilization, and yield were analyzed. 【Result】The results showed that at soil depth of 0-20 cm, the soil bulk density and electrical conductivity value under T2 treatments were significantly reduced by an average of 8.03% and 13.17% compared with CK (P < 0.05), while the total porosity, organic matter and available potassium contents significantly increased. The nitrate nitrogen content and available phosphorus under T2 were significantly increased compared with CK and T0. At a soil depth of 20-40 cm, the content of available phosphorus under T2 was significantly increased compared with CK. Compared with CK, T0, and T1, the content of soluble sugar and the activity of superoxide dismutase (SOD) at each filling stage, the soluble protein content and the activity of peroxidase at the early and middle filling stages, and the free amino acid content at the early filling stage in the flag leaf of T2 were significantly increased. Also, the content of superoxide anions radicals showed an opposite trend to the SOD activity while the total accumulation of nitrogen, phosphorus, and potassium under T2 in the aboveground part was significantly increased by 8.30% to 25.79% compared with CK, T0, and T1. The stomatal characteristic parameters of the flag leaf under T2 were significantly increased compared with CK, among which the stomatal size of the flag leaf under T2 was significantly increased by 21.23% compared with CK. Moreover, the yield of winter wheat under T2 treatment was significantly increased by 5.93% to 17.29% compared with CK, T0, and T1. Using mathematical modeling, it was observed that the optimal dosage of wood vinegar liquid following a simulation for a two-year period was close to the application amount of 540 kg?hm-2 of wood vinegar. 【Conclusion】Based on these results, it was recommended that the optimal amount of sheep manure to be applied should be 27 t?hm-2 while the amount of wood vinegar should be in the range of 535.46-551.03 kg?hm-2. This, could contribute to mitigating the negative impacts of saline-alkali soils and enhance winter wheat productivity in this region.

Abstract:Saline-alkali land is an important agricultural land resource, and in recent years, China has adopted various improvement measures for the management of saline-alkali soil. However, the improvement and utilization of saline-alkali land still face challenges, including high costs, severe water resource constraints, poor stability of improved saline-alkali land with a tendency to revert, and the need for enhanced low-water-consumption and high-efficiency technical support. To address these significant issues, this study proposes the concept of "rhizosphere suitable microzones" (RSM) for crops in saline-alkali soils. Focusing on the problems of "difficult emergence and establishment" of crops in saline-alkali land, as opposed to the overall soil improvement strategy, it expounds the theoretical framework of RSM. RSM refers to creating a specific local environment with unique physical, chemical, and biological characteristics within the small space of plant root systems, which differs from the surrounding environment and can support specific biological communities or life activities. This study proposes the technical path construction concept centered around "activating soil to promote root growth, using ions to nourish roots, acidification to regulate roots, and biological agents to protect roots". This will be achieved through cross-innovation of multiple theories, including soil fertility enhancement with carbon addition and salt reduction, balanced nutrient supply for salt inhibition, physical structure optimization to eliminate compaction, and enhancement of rhizosphere biological functions. Thus, it depicts the exploration of the construction principles and technical paths of RSM from a systematic perspective. This study outlines the key directions and contents of research on RSM and saline-alkali land improvement, aiming to break through the technical bottlenecks of saline-alkali soil improvement and promote the development of related disciplines. Specifically, the study considers salt-tolerant high-value crop varieties as pioneers, promotes the migration of sodium ions in the rhizosphere through water regulation, and considers the research and development of the technical path of RSM for crops in saline-alkali soils. This is centered on new slow and controlled-release fertilizers supplemented by anti-salt, growth-promoting, and biological strengthening factors.

Abstract:【Objective】Mineral-associated organic carbon (MAOC) constitutes the largest and most stable fraction of soil organic carbon (SOC), and increasing its proportion is essential for improving soil quality. Although long-term fertilization has significantly increased the MAOC proportion in SOC in Shajiang black soil, the accumulation patterns of plant- and microbial-derived carbon within MAOC, as well as their relative contributions to SOC, remain unclear. Therefore, this study aims to explore the accumulation characteristics of plant- and microbial-derived carbon and their contribution to MAOC in the 0-20 cm soil depth of Shajiang black soil under long-term fertilization. 【Method】Based on a 34-year field experiment, four treatments were established (no fertilizer and wheat straw return as CK, mineral fertilizer as NPK, mineral fertilizer with half amount of wheat straw return as NPKLS, and mineral fertilizer with full amount of wheat straw return as NPKHS). Biomarkers and chemometric methods were used to investigate the effects of long-term fertilization on plant and microbial-derived carbon in MAOC. 【Results】The results reveal that compared to CK treatment, NPKHS and NPKLS treatments significantly increased the content of MAOC by 29.6% to 54.3% (P < 0.05), with MAOC exhibiting a significant linear positive correlation with SOC (R2 = 0.95, P < 0.05) and carbon input (R2 = 0.98, P < 0.01). In terms of plant-derived components, the NPKHS treatment induced an increase of 14.8% and 13.3% in the contents of Vanillyl (V) and Syringyl (S) phenols, respectively, while the S/V and C/V ratios decreased by 1.27% to 9.46%. However, the differences in the acid-to-aldehyde ratios (Ad/Al)V and (Ad/Al)S were not significant (P > 0.05). For microbial-derived components, NPKHS treatment significantly elevated the amino sugar content, with an increase of up to 91.4% compared to the control (P < 0.05). Specifically, the contents of fungal residual carbon (FNC) and bacterial residual carbon (BNC) increased by 92.7% and 48.5%, respectively, with fungal necromass dominating (FNC/BNC=4.39). Biomarker analysis indicated that the microbial-derived carbon contribution rate was as high as 72.6% to 73.4%, whereas chemometric methods suggested that the plant-derived carbon contribution ranged from 74.0% to 82.6%. Compared to previous studies on grassland/forest ecosystems (53% to 65%), this proportion appears somewhat unreasonable, suggesting that the chemometric method may have overestimated the contribution from plant sources. 【Conclusion】Our findings indicate that long-term fertilization enhances the accumulation and stability of MAOC in Shajiang black soil primarily by increasing microbial-derived carbon content. This study provides an important reference for the efficient utilization of straw resources and for improving the quality of cultivated land in the Shajiang black soil region.

Abstract:【Objective】Vegetable production is frequently associated with high nitrogen fertilizer application and intensive crop rotation, resulting in soil acidification, structural degradation, and proliferation of harmful microorganisms. These factors significantly impede the sustainable development of vegetable farming. 【Method】Therefore, this study investigated the short-term effects of organic fertilizer, potassium humate, calcium carbonate, and their combinations on soil properties, organic carbon components, and microbial community structure in acidic vegetable fields with an untreated control (CK). 【Result】(1) Results showed that the sole application of full-dose organic fertilizer significantly increased total nitrogen, available phosphorus, and available potassium in non-rhizosphere soil, while significantly increasing easily oxidizable organic carbon (EOC) in non-rhizosphere (by 22.70%) and rhizosphere (by 9.76%) soils. The sole application of full-dose calcium carbonate significantly raised soil pH but reduced available phosphorus in non-rhizosphere soil and alkali-hydrolyzable nitrogen, available potassium, and organic carbon (SOC) in rhizosphere soil. Most notably, the combined application of all three amendments significantly increased soil pH and Chinese cabbage yield, compared to CK, while also increasing SOC, EOC, dissolved organic carbon (DOC), and the abundance of soil bacteria, fungi, Gram-positive bacteria, Gram-negative bacteria, and actinomycetes. (2) Correlation analysis between soil physicochemical properties and microbial community structure revealed that alkali-hydrolyzable nitrogen and EOC were significantly positively correlated with all measured microbial groups in the non-rhizosphere, where DOC correlated positively with bacteria. Also, in the rhizosphere, DOC correlated positively with bacteria and Gram-negative bacteria. Redundancy analysis showed that in non-rhizosphere soil, alkali-hydrolyzable nitrogen had the greatest influence on microbial communities. In rhizosphere soil, available potassium and DOC were the main factors affecting microbial communities. (3) Correlation analysis between soil properties and Chinese cabbage yield indicated that yield correlated positively with non-rhizosphere pH and rhizosphere exchangeable Ca2? and Mg2?, but negatively with rhizosphere alkali-hydrolyzable nitrogen. Structural equation modeling revealed that exchangeable Ca2+, available phosphorus, and alkali-hydrolyzable nitrogen had significant positive effects on cabbage yield, with Gram-negative bacteria indirectly influencing yield through available phosphorus. 【Conclusion】Based on these results, it can be concluded that the combined application of calcium carbonate and organic amendments effectively mitigated soil acidity, enhanced soil organic carbon sequestration, increased microbial biomass, and stabilized soil productivity. This study provides an important reference for research aimed at managing soil acidification and improving crop yields in acidic soils.

Abstract:【Objective】Organic Se is an important component of total Se in soil, and selenomethionine exists as one of the most common species among the organic Se. Given that the interfacial interaction between iron oxides in soil and organic Se species remains elusive, this study provides an avenue for understanding the migration and transformation of Se coupling with Fe-cycling in soil. 【Method】 In this study, the interfacial interaction between selenomethionine and iron oxides, ferrihydrite, goethite, and hematite was investigated through the analysis of surface species, coordination structure of iron atom (Fe) and adsorption configuration over the X-ray photoelectron spectrum (XPS), X-ray absorption fine structure spectrum (XAFS), and attenuated diffuse reflection infrared spectrum (DRIFTS-IR). 【Result】The results revealed that the binding energy (B.E.) of N1s was decreased to 399.7 eV and it was maintained for the main Se species adsorbed on ferrihydrite. The coordination structure of first- and second-sphere for Fe atom of ferrihydrite before and after interacting with selenomethionine did not change, while there was an adsorbed carboxyl-species with bidentate coordination mode. This result suggested that selenomethionine could be adsorbed on ferrihydrite through the bidentate coordination mode with a vertical adsorption configuration over carboxyl on the surface of ferrihudrite. After interacting with selenomethionine, the B.E. of Fe for bulk FeO6 at the goethite sub-surface was reduced by 0.4 eV. Also, the distance of first-sphere and coordination number of outer spheres for Fe atom in goethite showed an obvious change, compared to that of the fresh goethite. It indicated that goethite had undergone an obvious dissolution accompanied by obvious reduction effect after interacting with selenomethionine. Moreover, the Se atom mainly existed as the oxidized species on goethite. There was a monodentate coordination mode for the adsorbed selenomethionine on goethite with a horizontal adsorption configuration. For hematite, the B.E. of Fe both at sub-surface and surface were reduced to 0.4 eV, while the coordination structure of Fe atom for the Fe-sphere did not change but shortened in the first-sphere. This phenomenon revealed a characteristic weak dissolution interaction and a strong reducibility for hematite interacted with selenomethionine. Owing to the reduction by selenomethionine, there was a strong surface-enhanced infrared absorption effect for the adsorbed selenomethionine. Besides, the amino N and Se atoms might directly participate in the chemical adsorption of selenomethionine on hematite. Among the three iron oxides, there was a similar oxidization pattern for Se during the interaction process and this observation can be summarized as: 1) the complete oxidization of selenomethionine into selenite and 2) the incomplete oxidization species of selenomethionine. 【Conclusion】The interaction characteristic and mechanism of selenomethionine with ferrihydrite, goethite, and hematite was carefully revealed through surface analysis. The results revealed a differential response for the surface structure of mineral and change of selenomethionine when it interacted with iron oxides with different surface structure and properties. These findings provide an important reference for understanding the migration and transformation of organic Se in soil under different Fe-cycling processes. It also provides guidance for the unitization of Se resource and remediation of Se pollution in Se-rich area.

Abstract:【Objective】Iron (Fe) is an essential micronutrient for plant growth. Accurate monitoring of different forms of iron (Total Fe, Available Fe, Free Fe) is essential for soil health management and agricultural production optimization. Total iron and free iron are also necessary indicators to identify certain soil types. Compared with traditional soil determination methods, spectral technology is rapid, cost-effective, and environmentally friendly, and is gradually becoming an alternative for soil Fe determination in recent years. However, there are few reports on the systematic inversion of different forms of iron by spectral technology.【Method】Based on the color parameter (CP), visible near infrared (VNIR), mid infrared (MIR) , and fusion spectrum (SF) were used to obtain data of 501 typical farmland tillage layer (0~20cm) soil samples in Guizhou Province. The spectrum was smoothed by Savitzky-Golay (SG) denoising, and then the baseline was corrected by the standard normalization (SNV) method. Partial least squares regression (PLSR) and support vector machine (SVM) were used for modeling, respectively. The system compared the predictive performance of single spectra and fused spectra for the three types of iron fractions. Moreover, the relationship between accuracy and cost of different prediction strategies was quantified using two indicators: Cost-Efficiency Ratio (CER) and Efficiency Index (EI).【Result】The results show that: (1) in the single spectral model, VNIR spectrum performed best in the prediction of total iron (determination coefficient R2 = 0.85, relative analysis deviation RPD = 2.59, root mean square error RMSE = 5.48 g·kg-1), while MIR spectrum had the highest accuracy in the prediction of free iron (R2 = 0.80, RPD = 2.23, RMSE = 4.15 g·kg-1). Also, the decision level fusion (SF3) spectrum further improved the prediction accuracy of the three forms of iron, among which the effective iron increased the most, but it was still difficult to achieve effective prediction (RPD = 1.37). Thus, using spectral technology to predict soil available iron is not recommended. (2) The cost accuracy analysis showed that the spectral technology can significantly reduce the cost (by 40%~85%) of soil iron characterization. VNIR and MIR technologies had high accuracy and were cost-effective in the prediction of total iron and free iron, and were suitable for scenarios requiring comprehensive consideration of accuracy and cost. However, the accuracy improvement of fused spectrum (SF) was limited, and the cost increased more, which is suitable for scenarios requiring higher accuracy. 【Conclusion】This study shows that spectral technology can significantly reduce the cost of soil iron content measurement on the basis of ensuring a certain prediction accuracy, and can replace the traditional methods to achieve efficient monitoring of total iron and free iron, so as to provide effective technical support for the implementation of precision agriculture.

Abstract:【Objective】Direct application of soil amendments represents a crucial approach for ameliorating acidic soils. Grasping the fundamental properties of commercially available acidic soil amendments is vital for developing strategies to improve acidic soils in China. 【Method】In this study, detailed information regarding product registration and patent applications for acidic soil amendments in China was gathered and systematically organized. Subsequently, the basic properties; including particle size distribution, pH, contents of CaO and MgO, crystalline minerals, and functional groups, of 24 randomly selected commercial soil amendments were determined. The crystalline minerals and functional groups of soil amendments were identified by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analyses. 【Result】The results indicate that a substantial number of acidic soil amendments exist in China, accounting for 78% of all types of soil amendments. Driven by market demand, raw material availability, and agricultural development characteristics, the manufacturers of acidic soil amendments are predominantly located in Guangdong and Shandong provinces. The authorization rate of patents for acidic soil amendments in China is less than 10%. Among the authorized patents, the primary raw materials are organic matter and by-products from industry and agriculture, followed by natural minerals and chemical products. Specifically, the main raw materials listed in product registrations were carbonate minerals and oyster shells and most of the amendments were available in powder and granular forms, with a product registration ratio of approximately 2:1. However, the adoption of the powder products face challenges in promotion due to dust generation during application. The pH value, CaO content, and MgO content are the core indicators that most effectively reflect the ability of acidic soil amendments to mitigate soil acidity and replenish soil base nutrients. Even though some of the soil amendments did not fully disclose these three parameters on their packaging, the experimental evidence indicated that they were highly alkaline and exhibited high pH values and CaO contents, and most products also contained small amounts of MgO. These measured indicators aligned with their labeled values or ranges and the XRD and FTIR analyses further demonstrated that the predominant component in the commercially available amendments was CaCO?. In addition, other alkaline constituents such as Ca(OH)?, CaO, CaMg(CO?)?, and MgO were also present in some of the soil amendments, depending on their raw materials and production technologies. Moreover, most of the amendments also contained silicate minerals or SiO?. 【Conclusion】The results of this study revealed that the primary function of the commercially available amendments for acidic soils in China is the amelioration of soil acidity. However, due to the single functionality of these products, there are significant challenges in market promotion. To meet the diversified needs of agricultural production, it is necessary to further develop multi-functional acidic soil amendment products that can both regulate soil acidity and enhance soil fertility, thereby improving product practicability and market competitiveness. In addition, acidified soil amelioration is a systematic project. Besides strengthening the development of new products, it is also necessary to simultaneously advance various aspects of work such as soil acidification monitoring and early warning, and integration of acidified soil improvement technologies and models, in order to effectively promote the improvement and sustainable utilization of China""s acidic cultivated land.

Abstract:【Objective】Cunninghamia lanceolata is a significant timber species in subtropical China with a long cultivation history. However, persistent monoculture management has triggered multiple ecological issues, including soil nutrient depletion, biodiversity loss, and declining forest productivity. To enhance ecological functions and economic returns while achieving sustainable development of Cunninghamia lanceolata plantations, precious tree species were introduced through interplanting and their effects on soil chemical properties and microbial communities were investigated.【Method】Soil samples were collected from pure Cunninghamia lanceolata plantations (PC) and four mixed forests: Taxus wallichiana-C. lanceolata (MTC), Ormosia hosiei-C. lanceolata (MOC), Phoebe chekiangensis-C. lanceolata (MPC), and Houpoea officinalis-C. lanceolata (MHC) in Qingyuan Forest Farm, Zhejiang Province. Soil chemical properties were analyzed via standard protocols. Microbial community composition was characterized using 16S rRNA and internal transcribed spacer (ITS) high-throughput sequencing, while co-occurrence network analysis and partial least squares path modeling (PLS-PM) were employed to decipher microbial interactions and functional linkages.【Result】(1) Interplanting significantly improved soil chemical properties. The MPC treatment increased soil pH by 11.2% (P<0.05), while the MTC treatment elevated soil organic carbon (SOC) content to 31.8 g·kg-1, a 26.2% increase compared to PC (P<0.05). The MOC treatment significantly boosted available phosphorus (AP) content by 3.96 times relative to PC (P<0.01). (2) The bacterial co-occurrence networks in mixed forests exhibited increased nodes, edges, and path lengths. Significant differences (P<0.05) were observed in degree centrality, closeness centrality, and eigenvector centrality among the treatments. Notably, the MTC treatment resulted in the highest degree centrality and eigenvector centrality within the soil bacterial co-occurrence network, indicating the formation of a more efficient and stable bacterial community structure. (3) Functional gene analysis revealed distinct metabolic pathways: PC treatment was dominated by nitrogen respiration and nitrogen fixation functions, whereas MTC and MPC treatments activated xylanoly and nitrate reduction functions, respectively. (4) PLS-PM demonstrated that soil chemical properties indirectly influenced the expression of carbon and nitrogen cycling genes by regulating key microbial taxa, such as those within the Actinobacteria phylum.【Conclusion】Interplanting valuable tree species significantly enhances the stability of Cunninghamia lanceolata forest ecosystems by optimizing soil physicochemical properties and strengthening the complexity and functional redundancy of microbial networks. The improvements in soil chemistry (pH, SOC, AP), the formation of more complex and stable bacterial co-occurrence networks (particularly under MTC), and the shift towards specific functional genes (carbon decomposition, nitrate reduction) collectively underpin this increased ecosystem resilience. Based on the superior performance in fostering stable microbial structures and activating beneficial functional genes, the Taxus wallichiana-C. lanceolata mixed model (MTC) is prioritized for future promotion in southern China. Supplementing this with interplanting Phoebe chekiangensis is recommended to synergistically optimize overall soil quality.

Abstract:【Objective】 The invasive plant Sphagneticola trilobata has been expanding to higher latitudes and colder regions since it invaded China due to its rapid adaptability to the environment. As a part of the rhizosphere environment, the rhizosphere microbial community plays an important role in plant invasion and resistance to abiotic stress. However, the effect of rhizosphere microorganisms on the cold tolerance of invasive plants remains to be elucidated. It is therefore hypothesized that rhizosphere microorganisms of S. trilobata acclimated to cold stress play an important role in the improved cold resistance of S. trilobata populations to spread to high latitudes (colder regions).【Method】In this study, two populations of S. trilobata from the southernmost (Sanya ) and northernmost (Wenzhou ) regions of China were used as the research objects, and the cold-acclimatized rhizosphere soil microorganisms of these two populations of S. trilobata were used as microbial agents. Afterwards, the feedback effects of rhizosphere soil microorganisms on the cold tolerance of host plants after low temperature acclimation was explored through soil feedback experiments.【Result】 Under low temperature stress, the inoculation of rhizosphere microbial community significantly increased the biomass, root growth, chlorophyll and leaf nitrogen content of S. trilobata. The maximum photochemical efficiency and photosynthetic performance index of S. trilobata were significantly enhanced by inoculation of rhizosphere soil microbial agents domesticated by the northern (Wenzhou) population, and the relative content of anthocyanins was significantly reduced, indicating that it was less affected by low temperature stress. 【Conclusion】 The results showed that S. trilobata could improve its tolerance to low temperature stress by recruiting rhizosphere microorganisms, and the effect of northern populations was better. This indicates that domestication and recruitment of cold-tolerant rhizosphere microorganisms could promote the expansion of S. trilobata to higher latitudes. Moreover, this study provides an explanation for the possible reasons for differential cold tolerance in different populations of S. trilobata from the perspective of rhizosphere microorganisms, and emphasizes the necessity and urgency of strengthening the supervision of the current invasion boundary regions of S. trilobata.

Abstract:【Objective】Biopores constitute a critical component of the soil pore network, exhibiting significantly greater efficiency in facilitating the transport of water, solutes, and gases compared to nonbiopores. However, quantitative analysis of biopores at a single scale exhibits significant limitations in resolving morphological characteristics, elucidating developmental dynamics, and evaluating functional attributes. 【Method】To comprehensively characterize soil biopores distribution patterns, this study integrated a 5-year rotational field experiment on lime concretion black soil with high-resolution X-ray computed tomography (CT) scanning. The investigation was conducted at three distinct scales: (1) large column scale (10 cm diameter × 20 cm height soil columns), (2) small column scale (5 cm diameter × 5 cm height soil cores), and (3) aggregate-scale (3-5 mm aggregates). We systematically examined the effects of different cropping systems - conventional wheat-maize rotation (WM) versus cover crop rotations (wheat-Cassia occidentalis: WY, and wheat-Cassia tora Linn.: WJ) - on biopore characteristics within the 0-20 cm soil layer. Furthermore, we critically evaluated the applicability of each scale for biopore network analysis. 【Results】This study developed an improved biopores segmentation protocol comprising three key steps: (1) initial classification of pores into connected and isolated networks, (2) application of 3D distance transform watershed algorithms to separate biopores and nonbiopores, and (3) implementation of a Random Forest classifier leveraging morphological feature parameters (blobness, sphericity, compactness, and plateness) for scale-specific biopores segmentation across all three observational scales. Compared to the WM treatment, the WY treatment significantly increased bioporosity by 237%, 243%, and 119% at the large column, small column, and aggregate scales (P<0.05), respectively. Similarly, the WJ treatment resulted in an increase of bioporosity by 111%, 217%, and 114% at the large column, small column, and aggregate scales (P<0.05), respectively. At the large column scale, biopores exhibited significantly larger diameters than those at small column and aggregate scales, with mean diameters ranging from 1,444-3,374 μm and maximum diameters reaching from 4,792-8,854 μm (P<0.05). This scale effectively captured the biopores network architecture and directly revealed vertical continuity patterns throughout the 0-20 cm plow layer. However, large column scale analysis showed limited detection capability for fine biopores (<60 μm in diameter), reflecting inherent resolution constraints of the methodology. The small column effectively identified medium-to-fine biopores (>30 μm) and primarily correlates with soil physical properties governing hydraulic conductivity and gas transport. Microscale aggregate analysis can resolve ultra-fine biopores (>6 μm in diameter), with quantitative characterization revealing these biopores occupy 21.6-34.4% of total aggregate porosity. Aggregate scale analysis provides critical insights into root-soil architecture interactions and reveals fundamental mechanisms of soil organic carbon physical protection within microhabitats. 【Conclusion】This study demonstrated that cover cropping significantly enhanced soil biopore networks across multiple scales. We propose that future research adopt integrated multiscale approaches to fully unravel the spatial distribution and temporal evolution of these biopore systems.

Abstract:【Objective】The 15N isotope ratio of NH4+-N plays a crucial role in nitrogen transformation research and is widely applied to soil, water, and other samples with sufficient inorganic nitrogen content. While the diffusion method is the most effective technique for isolating and transforming soil NH4+-N, its application remains limited for low-concentration and natural abundance NH4+-N. 【Method】In this study, it is aimed to evaluate the feasibility of using the diffusion method alone for transforming and measuring low-concentration (≤1 mg·L-1) labeled and natural abundance NH4+-15N. To establish a diffusion system for rapid and accurate determination, this study improved the acid trap material and production method, incubation time, reaction volume, and incubation temperature. 【Result】The results demonstrated that: (1) The envelope diffusion packet acid trap exhibited higher nitrogen recovery?(95.0%) and better precision (standard deviation <0.010 atom%) compared to suspended acid traps. Envelope packets fabricated from domestic high-purity polytetrafluoroethylene (PTFE) could replace imported Merck Millipore PTFE, reducing costs by >90%.?The improved diffusion packet not only reduced the cost, simplified the operation and also increased N recovery to 99.8%. (2) The diffusion method accurately and sensitively measured the labeled NH4+-15N concentrations as low as 0.2 mg·L-1 with an error <0.006 atom%, and the difference between the corrected and the expected value was <0.020 atom%. In addition, diffusion method further exhibited robust performance in natural abundance NH4+-15N (≥1 mg·L-1), with an error ≤0.30‰ and a deviation from the expected less than 0.38‰. (3) Expanding the sample volume to 100 mL for low-concentration labeled samples and employing envelope packet acid traps for 8-day diffusion at 25 ℃ not only significantly enhanced recovery, measurement accuracy and precision, but also enabled accurate quantification of low-concentration NH4+-N (≥0.2 mg·L-1) with minimal isotopic deviation (Δ15N<0.020 atom%) after correction with standards. For even lower concentrations of labeled or natural abundance NH4+-N, it is advisable to combine diffusion method with additional methods. While heating can effectively shorten the incubation time and improve recovery, it also amplified interference from exogenous nitrogen impurities.?And heating may lead to increase the interference of dissolved organic nitrogen (DON) in natural soil or water samples, necessitating cautious application during practical measurements. 【Conclusion】Overall, diffusion remains a powerful method for transforming and measuring NH4+-15N in soil. This study enhances the concentration threshold and accuracy of labeled sample diffusion methods while significantly reducing experimental duration. The improved diffusion protocol can be used for measuring NH4+-15N at different concentrations and abundances, providing a theoretical foundation for accurate soil inorganic nitrogen analysis.

Abstract:【Objective】Soil health is essential to achieving sustainable agricultural development. 【Method】 This study selected the soil of a typical rice-wheat rotation area in southern Jiangsu Province as the research object. By measuring physical, chemical, and biological indicators, principal component analysis was used to identify soil health indicators and determine their weights. Combined with the membership function, the soil health index was calculated and subsequently classified. The microbial community indicators were obtained via high-throughput sequencing, and the random forest model was used to screen the indicators and construct a soil health assessment system based on microbial community indicators. 【Result】The results showed that biochar application significantly increased the content of soil available phosphorus (AP), but the content of available potassium (AK) was slightly lower compared to direct straw returning. The impact of different treatments on the alpha diversity index of the fungal community was more significant compared to that of the bacterial community. Also, the minimum dataset for soil health evaluation in the typical rice-wheat rotation area in southern Jiangsu Province, selected based on principal component analysis, consisted of soil organic carbon, AP, AK, and the activities of SUC and urease. The application of nitrogen fertilizer, single straw returning, and straw carbonization returning significantly increased the soil health index, while double straw returning reduced the soil health index in the short term. Moreover, the microbial community indicators selected by the random forest model were the relative abundance of Spirochaetota, Actinobacteriota, Mortierellomycota, bacterial Chao1 index, fungal Shannon index, and the relative abundance of functional genes such as rbcL, nosZ, ureC, and soxA. 【Conclusion】 The results of this study provide a scientific foundation for the formulation of agricultural management measures in the southern Jiangsu region and offer valuable insights into the construction of a soil health system based on microbial community indicators.