Abstract:Wheat, serving as a staple food for one-third of the global population, has long been overlooked in terms of its grain cadmium (Cd) accumulation capacity and the resulting dietary exposure risks. By integrating analyses of global literature and our recent research findings, this study preliminarily clarified that wheat grown in contaminated alkaline soils exhibited high Cd accumulation capacity with elevated risks of exceeding food safety thresholds. In rice-wheat rotation farmland systems, the Cd enrichment factor of wheat grains at the same sampling points was significantly higher than that of rice. Remarkably, wheat grains exceeded China’s food safety standard in alkaline soils even when the Cd contents remained below the national risk screening threshold. Elevated soil pH levels induced a pronounced increase in wheat's contribution to adult daily dietary cadmium intake, while concurrently reducing rice’s contribution, demonstrating that alkaline soil conditions amplify Cd exposure risks specifically through wheat-derived dietary pathways. The article further discussed the Cd speciation in alkaline soils and their influencing factors, analyzed the mechanisms related to Cd migration and its chemical binding forms at the root-soil interface, and explored the interaction effects between Cd and trace elements during uptake and translocation by wheat. In order to develop wheat-safe production technologies adapted to the characteristics of alkaline Cd-contaminated soils, future research should strengthen investigations into the molecular mechanisms of Cd interface processes in the wheat rhizosphere and Cd-trace elements interactions on uptake and translocation by roots.

Abstract:Hainan is the only province in China entirely situated within the tropical region, characterized by abundant light, heat, and water resources, making it the most typical tropical agricultural production base in China. However, restrictive factors such as "poor, acidic, and leaky" soils, coupled with high nitrogen (N) fertilizer inputs in crop cultivation, led to significant risks for N loss in farmlands and severe environmental pollution. The agricultural non-point source pollution situation in Hainan is severe, N and phosphorus discharged from agriculture enter nearshore waters via short transport pathways, leading to serious degradation of coral reefs and seagrass beds. However, the generally weak foundation of research on N cycling in Hainan's tropical farmland soils hindered the development of scientific and targeted N regulation measures. In response to the characteristics of tropical agricultural resources, we propose that future research should focus on four key areas: the characteristics of N transformation, the fate and loss pathways of N, the mechanisms of efficient N utilization in crops, and the principles and regulation measures for reducing N fertilizer application while enhancing efficiency. More attention should be paid to the effects of organic matter-mediated soil fertility and acidity improvement on soil N transformation in Latosols, the mechanisms underlying high ammonia emissions in acidic soils and nitrate accumulation in deep soil profiles, as well as the impact of organic material inputs on nitrous oxide emissions. We emphasize the need to clarify the relationship between the transformation and migration characteristics of N in farmland soils and crop N use efficiency, and to elucidate the mechanisms by which soil carbon (C) pool expansion affects N transformation, migration, retention, and loss prevention. Thus, to propose a principle for reducing N fertilizer application while enhancing efficiency, centered on "increasing C to retain N, coupling C and N, controlling losses, and coordinating N supply". This approach will form an innovative theory and solution. The finding would provide scientific and technological support for the development of efficient and green tropical agriculture and offer a scientific basis for understanding regional differences in N cycling across global climate-soil zones.

Abstract:Soil pipe erosion is a special erosion process caused by the formation and expansion of underground soil pipes. It makes important contributions to the development process of gully erosion and the gravitational erosion processes, such as landslides and collapse. It mainly affects the runoff-erosion-sediment transport process of the slope and watershed by changing the near-surface soil hydrological conditions. However, due to its concealment and complexity of genesis, related quantification research faces great challenges. Based on the bibliometric analysis method, this paper systematically reviews the development history of soil pipe erosion research and identifies the hot spots and development directions in the field of soil pipe erosion research. Aiming at the current research focus, this paper overviews the dynamic process of soil pipe formation, summarizes the multiple factors affecting soil pipe erosion, and analyzes the dynamic mechanism and harm of soil pipe erosion. In the future, it is necessary to innovate the monitoring methods of soil pipe erosion, clarify the dynamic mechanism of soil pipe erosion, quantify the contributions of key influencing factors, and develop a water erosion prediction model containing the processes of soil pipe erosion. This will provide a scientific basis for soil pipe erosion risk assessment and optimization of governance measures.

Abstract:【Objective】Soil spatial traceability has significant application value in forensic soil science and judicial identification.【Method】This study, based on 265 surface soil samples from Anhui Province, compares two soil provenance strategies: (1)a similarity-matching and spatial clustering approach, which filters similar samples using spectral and physicochemical property similarities and applies the DBSCAN algorithm to determine the potential source area of unknown samples; and(2)an inverse inference approach based on pedogenic environmental factors, which employs a random forest model to predict environmental variables such as soil parent material, land use, topography, climate, and vegetation, and infers provenance by integrating spatial distribution maps. By simulating provenance analysis, the accuracy and applicability of the two strategies were evaluated. 【Result】The results indicate that the similarity-matching strategy achieves higher localization accuracy under conditions of strong spatial proximity and well-established databases, while the inverse pedogenic environment inference strategy demonstrates superior spatial constraint capabilities in regions with limited databases or strong spatial heterogeneity. 【Conclusion】Each strategy has its own advantages, and their integrated application holds promise for further improving the accuracy and resolution of soil spatial provenance analysis.

Abstract:【Objective】The speciation of metal elements in soil determines their environmental functions and effects. Developing predictive models for element speciation based on soil properties is an important approach to enrich the informational value of such data and reduce the number of required analytical indicators. This is of great significance for data mining under conditions of limited information. Most metal elements, as important trace elements in soils, are widely present and affect crop growth and soil ecosystem health. Their forms and valence state have significant effects on their migration and transformation mechanisms on the surface and underground. Therefore, studying the metal forms in soil helps to understand their geochemical cycles and facilitate the evaluation of their impact on soil electronic networks, providing scientific basis for developing natural soil remediation methods and supporting the green, efficient, and sustainable use of soil. 【Method】This study selected manganese (Mn), a representative trace metal and redox-active element in soils, as the target. A total of 29 surface agricultural soil samples from different locations in the urban area of Hangzhou were collected and analyzed. The samples were characterized for their physicochemical properties, including total organic carbon (TOC), pH, total Mn content, and cation exchange capacity (CEC). The classical Tessier sequential extraction method was used to determine five Mn fractions in the soil: exchangeable, carbonate-bound, Fe-Mn oxide-bound, organic matter and sulfide-bound, and residual, and their correlation with soil physicochemical properties was evaluated. A neural network-based weight analysis method was then applied to predict Mn using soil physicochemical properties as input variables. 【Result】The results show that the soil pH was mainly alkaline, with abundant CEC and organic matter content. However, CEC exhibited high variability and was probably unevenly distributed and may be easily affected by external factors. Further analysis revealed that the average total Mn content in Hangzhou soils was 1.46 g·kg^-1, higher than the background value for Zhejiang Province. Among the Mn fractions, Fe-Mn oxide-bound and residual forms were dominant, followed by organic/sulfide-bound, while exchangeable and carbonate-bound forms were the least abundant. Spatial distribution showed a layered pattern for exchangeable and carbonate-bound Mn, decreasing from north to south. Significant positive correlations were observed among most Mn fractions, except for the residual form. Among the physicochemical factors, pH showed the strongest correlation with Mn speciation, particularly a highly significant negative correlation with the exchangeable and carbonate-bound species. CEC was positively correlated with carbonate-bound and organic-bound Mn, while soil organic matter showed no significant correlation with any Mn fraction. Also, the neural network modeling demonstrated that using three parameters: total Mn, pH, and CEC, yielded the best prediction performance, with the coefficient of determination (R²) improving from 0.41 to 0.85, and prediction error reducing from 65% to 16%. 【Conclusion】The findings of this study provide theoretical support for predicting metal speciation in soils based on the observed distribution patterns of Mn and its relationships with soil physicochemical properties. The neural network-based modeling approach proposed herein offers a feasible strategy for deep mining of conventional soil survey data and enables rapid estimation of specific metal species. This contributes to a better understanding of the behavior of Mn in the soil redox network.

Abstract:【Objective】The key to achieving sustainable utilization of newly reclaimed cultivated land in coastal areas is to control the upward accumulation of soil salinization. In this context, mulching and subsoil interlayer placement are widely adopted measures to mitigate salt accumulation in the surface soil. However, the combined effect of straw mulching with a biochar interlayer on soil water and salt transport in the southeastern coastal regions remains unexplored.【Method】This study considered a newly reclaimed cultivated land in the coastal areas of Fujian Province as the research object, and explored the impacts of biochar salt-barrier layer(with burial depths of 25 cm and 45 cm)combined with straw mulching on the distribution of water and salt during the water infiltration and evaporation processes of saline soils.【Result】The results demonstrated that the incorporation of a biochar interlayer significantly decelerated the wetting front advancement during the leaching process. Among all treatments, T3-25 (straw mulching combined with a biochar interlayer at 25 cm depth) exhibited the most pronounced effect, reducing the migration distance by 4.07% compared to the control (CK) after 73 hours of infiltration. As the leaching time prolonged, the salt content of the leachate in all treatments gradually decreased. On the first day of leaching, the T3-45 treatment (surface straw mulching + 45 cm biochar interlayer)had the highest leachate salt content, reaching 16.24 g·L^-1. In terms of total desalination amount, CK outperformed all interlayer treatments due to the absence of interlayer obstruction; it also had the highest pH value (8.07) after leaching. In the 0～45 cm soil layer, a significant reduction in soil salt content was observed across all treatments. The control (CK) treatment exhibited the highest desalination rate at 68.68%, while the T3-45 treatment demonstrated a superior desalination effect compared to T3-25. Regarding specific ions, the T3-25 treatment showed the most pronounced decrease in Na⁺ content, with an average reduction of 74.76%. Also, under the evaporation condition with a groundwater table depth of 65 cm, the soil water content in the 0～45 cm layer was significantly higher in both T3-0 (straw mulching only) and T3-45 treatments than in CK. Following 45 days of evaporation, a notable increase in both total salt and Na⁺ content was detected in the 0～45 cm soil layer for all treatments. Additionally, the T3-45 treatment displayed the lowest increments in the salt accumulation rate and Na⁺ content, at 3.49% and 14.06% respectively, relative to pre-evaporation levels. In contrast, the CK treatment exhibited the most severe salt accumulation, with corresponding increases of 54.21% and 150.19%. By the end of the evaporation stage, the soil pH in all treatments had increased significantly compared to both pre-evaporation values and the CK, with the relative increase over CK ranging from 0.71% to 3.57%.【Conclusion】Based on the experimental results, the combined application of straw mulching with a biochar interlayer at 45 cm depth proved most effective. It not only reduces water evaporation but also achieves the best performance in promoting desalination and inhibiting the salinization of coastal saline soil. This study found that the effects of the T3-25 treatment and the T3-45 treatment are similar. In practical applications where upfront cost-effectiveness is a consideration, the improvement measure of straw mulching with a biochar interlayer buried at a 25 cm depth can be considered for newly reclaimed coastal farmlands in the southeast region.

Abstract:【Objective】To establish scientifically grounded, synergistic regulatory approaches for the comprehensive mitigation of the persistent challenge of saline-alkali soil degradation in cotton-growing systems, this study conducted a controlled field experiment during the 2024 cotton season on moderately saline-alkali soils in Manas County, Xinjiang. The objective was to elucidate how the integrated application of poly-γ-glutamic acid (γ-PGA) and regulated irrigation influences soil biochemical processes, cotton physiological performance, yield formation, and fibre quality under field conditions.【Method】A two-factor randomized block design was established, involving three γ-PGA rates (F1: 7.5 kg·hm^-2; F2: 15 kg·hm^-2; F3: 22.5 kg·hm^-2) and two irrigation quotas (W1: 4 000 m³·hm^-2; W2: 4 500 m³·hm^-2). Comprehensive measurements included soil physicochemical indices (Electrical conductivity (EC)-based salinity and pH variations across growth stages), key enzymatic activities (polyphenol oxidase, catalase, urease, sucrase), root morphological traits (length, diameter, biomass ratios), organ-specific dry matter accumulation, and yield and fibre parameters (boll number, lint percentage, composite quality index).【Result】Compared with F1 and F2, the F3 treatment effectively suppressed peak soil salinity and pH, concurrently elevating enzymatic activity, particularly urease, which increased by 30.13%-35.22 %. Nevertheless, the response plateaued beyond the F3 level, suggesting diminishing returns under higher γ-PGA concentrations. Enhanced enzymatic activity and improved rhizosphere conditions promoted root proliferation and biomass accumulation, resulting in a moderate but statistically significant yield increase (3.02%-27.96 %). Likewise, a higher irrigation quota (W2) alleviated surface salt accumulation and improved enzyme activities by 9.16%-48.33%, although excessive irrigation risked secondary salinization through capillary rise and nutrient leaching. Also, multivariate analyses (Principal component analysis and Pearson correlation) revealed a strong positive correlation (P < 0.05) between enzyme activity and yield traits. At the same time, soil salinity and alkalinity showed negative correlations with fibre quality indices, emphasizing the trade-off between osmotic stress alleviation and fibre maturation under saline conditions.【Conclusion】The combined application of 22.5 kg·hm^-2 γ-PGA with 4 500 m³·hm^-2 irrigation proved the most efficient configuration within the tested range, primarily by ameliorating the rhizosphere microenvironment (lower EC/pH and enhanced enzymatic turnover) and optimizing photosynthate allocation to reproductive organs. However, the overall improvement remains conditional on soil salinity thresholds, long-term stability, and economic feasibility. Thus, while the integrated γ-PGA-irrigation strategy significantly enhances cotton yield and fibre quality in saline-alkali soils, its scalability and sustainability under variable climatic and hydrological regimes warrant further investigation.

Abstract:【Objective】Managing soil acidification in farmland soils is of great significance to ensure national food security and sustainable agricultural development. Microorganisms have important application value in soil improvement. However, the research on alkali-producing microorganisms and the mechanism of improving acid soil is still lacking. This study aimed to systematically explore the mechanisms of acidified soil remediation by alkali-producing microorganisms, with a focus on overcoming the limitations of functional microbial resource scarcity and field application technology gaps. 【Method】Systematic screening was employed to isolate alkali-producing microorganisms from acidic soils in South China. Indoor simulation experiments evaluated its pH elevation capacity through repeated inoculation. Genomic analysis revealed its urease gene cluster (ureABCEFGD), and field trials assessed the effects of single-dose application on soil pH and crop yield. 【Result】We screened 109 alkali-producing bacterial strains (65% belonging to Bacillus spp.) and 24 fungal strains (33% Trichoderma spp.). The alkali-producing ability and stability of alkali-producing bacteria were generally stronger than those of fungi, with Lysinibacillus fusiformis LW-3 identified as a key strain. Within 15 weeks of continuous culture, repeated inoculation of L. fusiformis elevated soil pH by 1.5 units, reduced exchangeable aluminum by 23.46%, and decreased hydrolytic acid by 31.80%. Genomic analysis revealed that L. fusiformis LW-3 carried a complete urease gene cluster (ureABCEFGD). Lysinibacillus fusiformis LW-3 could ameliorate acid soil by enhancing soil urease and protease activities, metabolizing ammonia, consuming hydrogen ions through bicarbonate, and reducing the content of active and potential acids in soil. Field application confirmed that soil pH stably increased by 0.2 units and enhanced Chinese cabbage yield by 11.6%. 【Conclusion】This study elucidated a multi-pathway synergy mechanism for acidified soil remediation, including alkali production, enzymatic activity regulation, and acid speciation transformation. These findings indicate that the strain L. fusiformis LW-3 has good application prospects in acid soil amendment, providing technical support for alkaline-producing microbiome-driven soil acidification management.

Abstract:【Objective】 Land-use change is a primary driver of soil structure alteration and nutrient cycling in ecosystems. In subtropical hilly areas of China, which are ecologically fragile and experience significant land-use pressure, understanding the interplay between soil physical structure and biogeochemical cycles is crucial for sustainable land management. The stability of soil aggregates and the ecological stoichiometry of nutrients serve as critical indicators for evaluating ecological restoration and soil quality. Thus, this study aims to elucidate the mechanism by which typical land use practices in subtropical hilly areas influence nutrient variations through alterations in the distribution characteristics of soil aggregates. 【Method】 We examined soils from three representative land use types(forestland, tea garden, and cultivated land)in Yingshan County, Hubei Province. Key stability indices, including the mean weight diameter (MWD), geometric mean diameter (GMD), soil erodibility (K), and fractal dimension (D), were calculated. Utilizing both stoichiometric methods and multivariate statistical models, we analyzed the relationship between aggregate stability levels and the distribution patterns of soil organic carbon, total nitrogen, and total phosphorus. 【Result】 The results revealed that: (1) The content of >5 mm aggregates in forestland soils was 4.11 and 1.89 times higher than that in tea garden and cultivated land, respectively. Both the mean weight diameter (MWD) and geometric mean diameter (GMD) followed the order: forestland > cultivated land > tea garden. The tea garden soil exhibited the highest erodibility (K) value and fractal dimension (D) value. (2) The soil organic carbon content in forest land was significantly higher than in other plots, reaching 10.22 g·kg^-1. Total nitrogen content followed the order of forest land > tea garden > cultivated land, while total phosphorus content exhibited the opposite trend. Both C: P and N: P ratios were highest in forestland soils, followed by cultivated land and tea garden. (3) Aggregate characteristics were significantly correlated with nutrient indicators (P< 0.05), with the macroaggregates (> 5 mm) playing a major role in shaping C: P and N: P ratios. Also, the partial least squares path modeling (PLS-PM) showed good fit(goodness-of-fit > 0.61)and the path coefficients indicated that the influence pathways of aggregate particle size on nutrient stoichiometric ratios varied under different land use types, with the direct effect being most pronounced in forested areas. 【Conclusion】 This study illustrates that changes in land use significantly affect the relationship between soil structure and nutrient cycling. Forestland, which experiences minimal disturbance, encourages the creation of stable macroaggregates. This process enhances long-term nutrient sequestration and maintains a balanced stoichiometric environment. On the other hand, intensive management practices in tea gardens and cultivated lands can disrupt aggregate stability. This disturbance leads to structural degradation and a notable stoichiometric imbalance. Therefore, it is crucial to preserve forestland and implement sustainable soil practices in managed lands. This approach will significantly improve soil quality and promote ecological sustainability in subtropical hilly areas.

Abstract:[Objective]To curb the trend of soil degradation and improve ecological environment quality, large-scale and long-term vegetation restoration projects have been carried out in the Loess Plateau region. However, the long-term variations in soil volumetric water under typical vegetation restoration types, especially the variability and differences in soil moisture, have not been given in-depth attention. [Method]Therefore, this study selected typical artificial forests (Pinus tabuliformis, Platycladus orientalis, Robinia pseudoacacia) and natural forests (Quercus mongolica secondary forest) in the Loess Plateau remnant gully area as the subject focus. Based on a long-term sequence (2006—2025) of 0～200 cm soil volumetric water dynamics, combined with multi-phase soil physicochemical properties and vegetation growth attribute data, this study used one-way analysis of variance, principal component analysis, and Mantel test to explore the effects of soil physicochemical properties and vegetation growth parameters on the soil hydrological dynamics in long-term vegetation restoration. [Result]The results show that: (1) Significant soil moisture differences exist between vegetation restoration types: compared to artificial forests, the natural forest has a higher overall soil volumetric water content, with an average of 16.8%and a peak of 30.4%, and greater moisture stability, with an average coefficient of variation of 12.89%; (2) Significant differences exist in soil physicochemical properties and vegetation attributes among different vegetation restoration types. The natural forest has higher nitrogen (236.428 mg·kg^-1), phosphorus (488.575 mg·kg^-1), and organic carbon content (14.903 g·kg^-1) than the three artificial forests. The biomass and height of the tree and shrub layers are lower in the natural forest than in the artificial forests; (3)Principal component analysis and Mantel test analysis show that soil moisture differences are mainly influenced by both tree and understory vegetation attributes, while soil moisture variability is predominantly influenced by understory vegetation attributes. [Conclusion]This study can provide a theoretical basis for the conservation of natural forests in the region, the optimization of understory vegetation in plantations, the enhancement of water conservation capacity through the cultivation of understory vegetation, and the management of soil and water conservation.

Abstract:【Objective】The aggregation and dispersion of soil colloids influence macroscopic phenomena such as soil structure, soil erosion, soil nutrients, and pollutant transport. This study aims to explore the process of purple soil colloid aggregation and its ion-specific effects under different fertilization treatments. Specifically, the study aims to elucidate the interactions and microscopic mechanisms from the perspective of the effect of fertilization on mineral composition, surface properties, and aggregation kinetics of purple soil colloids. 【Method】In this study, four fertilization treatments, no fertilizer (CK), urea alone (N), organic fertilizer replacing 10% urea nitrogen (LM), and organic fertilizer replacing 30% urea nitrogen (HM) were set up on a purple soil in Southwest China. After 60 d of incubation, the effect of fertilization on the colloid aggregation kinetics of purple soils and their causes were investigated by determining the colloid quantity, clay mineral composition and surface properties, and soil colloid aggregation process. 【Result】The colloids used in this study contained mainly hydromica, chlorite, montmorillonite, vermiculite, and kaolinite, and the short-term fertilization treatments had no significant effect on the colloid content and mineral composition. Compared to CK, the N treatment induced the highest surface charge density to the purple soil colloids, with the greatest electrostatic repulsion between particles whereas LM and HM treatments decreased the surface charge density, and the degree of decrease was directly proportional to the amount of organic fertilizer added. The aggregation kinetics of soil colloids differed under different fertilizations and the critical coagulation concentration (CCC) decreased in the order of N > CK > LM > HM. Under the same fertilization treatment, the CCC values of purple soil colloids showed an ion-specific effect, decreasing in the order of Na⁺, K⁺, Mg²⁺, and Ca²⁺. Also, correlation analysis showed that there was a strong positive correlation between the CCC values of purple soil colloids and the surface charge density and a strong negative correlation with the specific surface area and organic matter content. 【Conclusion】Different fertilization treatments affect the interaction force between soil particles mainly by influencing the surface chemical properties of purple soil colloids, thus, affecting the aggregation and dispersive behaviors of the colloids.

Abstract:【Objective】 Soil components serve as the material basis determining soil properties and heavy metal behaviors. However, the effects and mechanisms of different soil components on cadmium (Cd) adsorption performance, speciation, and bioavailability in purple soil remains elusive. 【Methods】This study employed selective removal and exogenous addition methods, combined with adsorption-desorption experiments, sequential chemical extraction, and pot bioassays, to investigate the effects of core components of OM (humic acid, HA and fulvic acid, FA), iron oxides, and manganese oxides on Cd adsorption performance, speciation, and bioavailability in purple soil.【Results】 The results showed that there were significant differences in the effects of the various components of purple soil on soil properties: the removal of organic matter (ROM) and iron oxides (RFe) significantly increased soil pH and specific surface area (SSA), while the removal of manganese oxides (RMn) had the opposite effect; the removal of each component significantly reduced soil cation exchange capacity (CEC), charge quantity (SCN), and density (σ₀), with the effects of RFe and RMn being the greatest; the addition of exogenous components had a significantly weaker effect on soil properties than component removal, and only the addition of organic matter-containing components (AHA and AFA) could increase soil pH and CEC, but significantly reduce SSA; the addition of manganese oxides (AMn) significantly increased SSA. The changes in soil components and properties regulated the environmental behaviors of Cd: ROM and RFe significantly enhanced the adsorption capacity and strength of soil Cd, while RMn had no significant effect; in the component addition treatments, only AHA and AMn could enhance the Cd adsorption capacity by soils. The availability of Cd (Avail-Cd) in purple soil was constrained by its occurrence form and had no significant correlation with adsorption capacity; among the various forms of Cd in the soil, only exchangeable Cd(EX-Cd) positively contributed to Avail-Cd, while carbonate-bound (CA-Cd), organic-bound (OM-Cd), and iron-manganese-bound (FeMn-Cd) all showed negative contributions. ROM and RFe, as well as AHA, promoted the transformation of EX-Cd to above less labile forms, thereby reducing soil Avail-Cd contents by 39.30% to 96.80%; while RMn, RFe-Mn, and AFA treatments acted the opposite, significantly increasing Avail-Cd contents by 2.38 times to 2.91 times.【Conclusion】 The pot experiment confirmed that the accumulation of Cd in pakchoi (Brassica chinensis L.) is mainly regulated by the availability of soil Cd. Changes in soil components altered the biological availability of Cd mainly by adjusting soil pH, CEC, OM, SSA and thereby the distribution of Cd forms in soils. This study clarifies the regulatory effects and mechanisms of soil key components on Cd bioactivity, providing a theoretical bases for soil pollution remediation and management.

Abstract:【Objective】Phytic acid-modified biochar exhibits excellent adsorption capacity for cadmium (Cd) in aqueous solution; However, its effectiveness and mechanisms in remediating Cd-contaminated soils remain unclear. This study systematically analyzes the dynamic impacts of phytic acid-modified biochar on soil properties, and Cd release in soil, and reveals the key mechanisms underlying biochar regulation of Cd movement in soil. 【Method】 Soil incubation experiments were conducted to systematically evaluate the remediation and amelioration effects of bamboo biochar (BBC), phytic acid-modified bamboo biochar (PABC), and sodium phytate-modified bamboo biochar (SPBC) on Cd-contaminated soils over various incubation periods (0, 10, 20, 60, 120, and 180 days). 【Result】The addition of biochar significantly altered the pH of both soil and soil solution and increased the electrical conductivity (EC). SPBC exhibited the highest EC and total carbon concentration in the soil solution, while PABC showed a distinct advantage in supplying total phosphorus, particularly in the short term. During the early and mid-phases (0-120 days), biochar treatment significantly reduced the Cd concentration in soil solution(24.60%-99.35%), with a significant dose-response effect, and SPBC exhibited the most effective remediation. In addition to their inherent adsorption mechanisms, biochar also inhibited Cd release indirectly by affecting the chemical (pH, total phosphorus, and total carbon), physical (aggregate structure), and biological properties (urease and acid phosphatase) of the soil and soil solution, with soil pH and micro-aggregate content identified as key factors influencing Cd release. In the later phase (120-180 days), enhanced soil aggregate stability further facilitated the remediation process, as biochar increased the activity of urease and acid phosphatase. 【Conclusion】 Phytic acid-modified biochar demonstrates strong potential for both Cd remediation and soil improvement in heavily contaminated soils, offering significant application value.

Abstract:【Objective】This study examines the evolution and core issues of domestic and international research on homestead land reclamation.【Method】Using “homestead reclamation” and “homestead soil reconstruction” as search terms, relevant literature was retrieved and screened, and visual bibliometric analysis was performed with CiteSpace.【Result】Domestic studies emphasized land-use optimization, urban-rural integration, ecological protection, market mechanisms, and policy interactions with a practical “problem-countermeasure” orientation. However, international literature favored case studies, technological innovation, and mechanistic analyses of reclamation impacts. Nevertheless, both recognized soil quality as critical to reclamation success.【Conclusion】Future research should foster interdisciplinary collaboration, carry out long-term empirical studies, and support incentive-compatible policy frameworks so that rural land reclamation yields sustainable, mutually beneficial outcomes across ecological, social, and economic dimensions.

Abstract:【Objective】Northeast China is an important grain production base, and it is also one of the largest fertilizer consumption markets. Over the years, the application of many chemical fertilizers has led to increasingly prominent negative impacts on the agricultural ecological environment. Using the application rate of chemical fertilizer in Northeast China in the past three decades, it was estimated environmental cost (EC) from different potential pollution, and their comprehensive environmental cost(CEC)and environmental cost load (ECL). This research will provide a scientific basis for realizing agricultural sustainable development in Northeast China and ensuring China 's food security. 【Method】Combining energy analysis and disability-adjusted life year assessment, the spatial and temporal distribution characteristics of EC from different potential pollution sources, and their CEC and ECL were analyzed in Northeast China from 1990 to 2022. The EC in different provinces and cities and their potential causes were evaluated, and countermeasures and suggestions for reducing EC were put forward. 【Result】(1) From 1990 to 2022, the CEC of fertilizer application in Northeast China gradually increased, from 42.12 million yuan to 3 200.55 million yuan, an increase of 76 times, with an average annual growth rate of 14.49%. The growth rates of the 1990s, 2000s, and 2010s were 22.69%, 16.67%, and 7.78%, respectively, which gradually slowed down. (2) In 2022, the total EC of air, water, and soil pollution caused by chemical fertilizer application was 542.37 million yuan, 749.36 million yuan, and 1908.8 million yuan, respectively. Ammonia and nitrate, respectively, contributed the most to air, water, and soil pollution. Their ECs respectively were 467.92 million yuan, 691.76 million yuan, and 1 485.17 million yuan, reaching 82.64% of the total EC. (3) The largest change in CEC was mainly concentrated in the line from Jiamusi to Chifeng, while the smaller change was concentrated in the line from Yanbian to Dalian. The largest changes in ECL were mainly concentrated in most areas of Liaoning Province, Tongliao, Shuangyashan and the surrounding areas of Jixi, while the smaller changes were mainly in Siping, Yichun, Daxing'anling, and Xilinguole. 【Conclusion】 In the past three decades, the CEC of chemical fertilizer application in Northeast China has increased year by year, but the growth rate has gradually slowed down, indicating that the impact of chemical fertilizer application on the environment has been significantly alleviated. In addition, the EC and ECL showed obvious spatial distribution characteristics, which indicates that the impact intensity of the southern and southern coastal areas was stronger than the northern inland areas. In future research, it is recommended that the focus should be directed towards typical black, brown, and other types of soil in Northeast China, as well as typical cultivated areas such as the corn belt and miscellaneous grain area in Northeast China, to further explore the spatial differences of CEC. Although chemical fertilizer input can increase grain yield, it also brings high EC, which requires scientific fertilization measures according to local conditions. It is necessary to continue to promote scientific fertilization and reasonable intercropping/rotation to improve the utilization efficiency of chemical fertilizers. Finally, the effect of reducing fertilizer application and being environmentally friendly will be realized to ensure the sustainable development of agricultural production in Northeast China.

Abstract:【Objective】Elevated near-surface ozone (O₃) concentrations are an increasing threat to rice production, but the mechanisms and dose effects on below-ground ecosystems, including soil nutrient cycling and microbial communities, remain poorly understood. 【Method】This study targeted three major rice cultivars (HuaiDao 5, NanJing 5055, and WuYunJing 27) in the Yangtze River Delta. Using open-top chambers, we conducted an 84-day fumigation experiment with four ozone concentration gradients, including [NF(ambient air), NF20(ambient air + 20 nmol·mol^-1 O₃), NF40 (ambient air + 40 nmol·mol^-1 O₃), and NF60 (ambient air + 60 nmol·mol^-1 O₃)], to systematically analyze the dose-response effects of elevated O₃ concentration on soil nutrients and microbial communities in paddy fields. 【Results】The results showed that increasing O₃ concentration significantly altered soil NO₃^--N and available phosphorus (AP) contents, as well as the abundances of methanotrophs (pmoA gene) and archaea during the rice filling stage, whereas no significant effects were observed for soil DOC, total carbon (TC), available potassium (AK), bacterial or methanogen (mcrA gene) abundances. The interaction between O₃ fumigation and rice cultivar significantly affected soil NH₄⁺-N, NO₃^--N, and AP contents. Specifically, O₃ fumigation significantly reduced NO₃^--N contents in HuaiDao 5 and WuYunJing 27, although the inhibitory effect weakened with increasing O₃ concentration. In contrast, NH₄⁺-N content in NanJing 5055 significantly increased under the highest O₃ treatment (NF60). Similarly, NH₄⁺-N in HuaiDao 5 decreased under O₃ stress but the effect weakened at higher concentrations, whereas NH₄⁺-N in WuYunJing 27 increased under NF60. AP content in HuaiDao 5 exhibited a negative correlation with O₃ concentration, whereas no significant effects were observed in the other two cultivars. O₃ fumigation significantly increased the abundance of pmoA gene in NanJing 5055 and WuYunJing 27, with the promoting effect intensifying under higher O₃ concentrations. Soil bacterial community analysis revealed cultivar-specific responses, the relative abundance of Bacteroidota in WuYunJing 27 and Chloroflexi in NanJing 5055 was positively correlated with O₃ concentration, while the relative abundance of Bacteroidota in NanJing 5055 and Desulfobacterota in HuaiDao 5 showed significant negative correlations. Moreover, the abundance of carbon and nitrogen metabolic pathways in NanJing 5055 and WuYunJing 27 exhibited nonlinear dose-response relationships with increasing O₃ concentrations. 【Conclusion】Our findings demonstrate that soil nutrient dynamics and microbial community responses to O₃ stress are highly cultivar-specific, with evidence suggesting the existence of threshold concentrations for O₃ sensitivity. However, accurately quantifying the mechanisms underlying O₃-induced alterations in below-ground elemental cycling and identifying key ecological thresholds will require long-term in situ observations. These findings offer critical insights for assessing the ecological risks of ozone pollution in rice paddies and guiding the selection of ozone-tolerant cultivars.

Abstract:【Objective】Dissolved organic matter (DOM) is the most active functional component in the soil carbon pool, and the application of organic fertilizer is an effective measure for carbon sequestration and soil fertility improvement in greenhouse soils. However, the response of DOM content and quality in greenhouse soils to organic fertilizer is still unclear, which hinders the elucidation of the regulation mechanisms of the active carbon pool in greenhouse soils and the development of precise application technologies for organic fertilizers.【Method】This study was conducted in situ and five treatments were included: no fertilization as control (CK), chemical fertilizer only (F), and three organic fertilizers with different carbon components replacing 30% of chemical N fertilizer (composted straw replacing 30% of chemical N, FMs; chicken manure replacing 30% of chemical N fertilizer, FMc; and spent mushroom replacing 30% of chemical N fertilizer, FMm). The content of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) were studied in the surface and subsurface layers of greenhouse soils under vegetable cultivation. Combined with three-dimensional fluorescence spectroscopy technology and parallel factor analysis method, the fluorescence spectral characteristic parameters and chemical composition of DOM in soil were analyzed.【Result】Compared with CK, the F treatment had no significant effect on the DOC content in both the surface and subsurface soil; it only significantly increased the DON content in the subsurface soil, with an increase of 1.22-folds. The results showed that compared with F, the FMc organic fertilizer with the highest content of labile carbon components significantly increased the DOC and DON content by 44.2% and 78.1%, respectively, in the surface soil. However, only the DON content in the surface soil significantly increased under the FMs and FMm treatments. Compared with CK, the application of chemical and organic fertilizers significantly reduced the DOC/DON ratio in the surface and subsurface soils, and the humification index (HIX) of DOM in the surface soil significantly increased by 1.06 to 2.07-folds, reaching the highest in the FMc treatment. Also, the fluorescence spectral characteristics of DOM in the subsurface soil did not significantly respond to fertilization. In addition, the content of DOC and DON were significantly negatively correlated with fulvic acid-like components with low molecular weight, while significantly positively correlated with humic acid and aromatic components with high molecular weight.【Conclusion】In summary, the application of chicken manure rich in labile carbon components can more effectively increase the content of DOC and DON and the humification degree of DOM in the surface soil, and increase the proportion of refractory components of DOM in the subsurface soil. Thus, it is more beneficial to apply chicken manure to achieve the "double improvement" of the content and quality of labile carbon pools in the entire tillage layer of greenhouse soils under vegetable cultivation.

Abstract:【Objective】To combat the depletion of organic carbon and poor water-fertilizer retention in the Horqin Sandy Land, this study examines the mechanisms by which pelletized straw incorporation enhances soil organic carbon and its active fractions.【Method】Through a controlled incubation experiment, the study established treatments with different application rates of pelletized straw: a control with no straw addition (CK), 75 t·hm^-2 pelletized straw (PS75), and 150 t·hm^-2pelletized straw (PS150). Additionally, the experiment included duration treatments consisting of single-year application and two consecutive years of application.【Result】 Compared to the CK treatment, pelletized straw application significantly increased soil organic carbon (SOC) and total nitrogen (TN) contents by 217.52%～749.15% and 197.78%～679.25%, respectively. With increasing application rates and duration of pelletized straw incorporation, the carbon and nitrogen retention capacity of sandy soil was significantly enhanced. Application of pelletized straw consistently elevated the C/N ratio of the sandy soil, with the most significant increase observed in the PS150-1a treatment (P<0.05). Also, the addition of pelletized straw significantly enhanced particulate organic carbon (POC), mineral-associated organic carbon (MAOC), and labile organic carbon (LOC) contents (P<0.05). The contents of POC, MAOC, and LOC increased significantly with higher application rates of pelletized straw and longer amendment duration. Moreover, POC, LOC, and MAOC all showed highly significant positive correlations with total SOC content (P<0.01). Notably, the 150 t·hm^-2 pelletized straw treatment with two consecutive years of application significantly increased the proportion of POC to total SOC by 31.81% (P<0.05), suggesting a preferential accumulation of this active carbon fraction. Nevertheless, pelletized straw application significantly reduced bulk density while improving water-holding capacity and porosity in sandy soil. The study found a statistically significant positive correlation (P<0.01) between the water-holding capacity of sandy soil and the duration of pelletized straw application. Moreover, the improved water retention in sandy soils resulted from synergistic physical adsorption and chemically mediated retention from pelletized straw decomposition. According to redundancy analysis, soil physicochemical properties explained 98.90% of the variability in SOC, TN, and C/N. Besides, MAOC was the primary driver, highlighting mineral association as a fundamental mechanism for soil carbon and nitrogen stabilization. Partial least squares path modeling demonstrated that the cumulative addition of pelletized straw directly promoted SOC sequestration by significantly increasing the contents of both LOC and MAOC (P<0.01). The model further confirmed the dominant role of MAOC in SOC stabilization, highlighting the importance of mineral protection mechanisms for carbon retention in sandy soils. The accumulation of SOC significantly increased TN content (P<0.01), indicating a coupled carbon and nitrogen sequestration effect in the sandy soil. Furthermore, increasing the application rate of pelletized straw significantly reduced soil bulk density and enhanced water holding capacity (P<0.01). In summary, the study demonstrated that SOC fractions served as the key mediator for carbon-nitrogen coupled stabilization in sandy soils. The establishment of this regulatory mechanism provides a theoretical foundation for carbon sequestration management in arid sandy soils.【Conclusion】The study demonstrates that pelletized straw incorporation effectively enhances sandy SOC fractions, promotes carbon-nitrogen synergistic sequestration, and improves soil physical properties, with the optimal effects achieved at 150 t·hm^-2 with two consecutive years of application.

Abstract:【Objective】Soil organic carbon (SOC) sequestration in agricultural ecosystems is critical for mitigating climate change and maintaining soil fertility, with mineral-associated organic carbon (MAOC) playing a central role in long-term C stabilization. Paddy soils with higher SOC density exhibit distinct biogeochemical cycles due to periodic flooding and anaerobic conditions, making their SOC dynamics particularly complex. While biochar amendment has emerged as a promising strategy to enhance SOC storage, the specific mechanisms by which biochar interacts with soil mineral fractions and modulates native SOC stability remain poorly understood. Previous studies have primarily focused on total SOC changes, overlooking the differential responses of mineral-bound C pools to biochar input. This knowledge gap hinders accurate assessments of biochar's long-term C sequestration potential in paddy systems. The present study aimed to address this gap by investigating how biochar amendment affects SOC distribution across density-based mineral fractions and alters native SOC dynamics through advanced spectroscopic and isotopic tracing techniques.【Method】In this study, a field experiment was established in a typical paddy soil in southern China, with two treatments: biochar application at 15 t·ha^-1 (C15) and no biochar (C0). After two years of rice cultivation, soil samples were collected from the 0-15 cm depth and subjected to sequential density fractionation using sodium polytungstate solutions with gradient densities (1.65, 1.85, 2.05, 2.25, 2.45, 2.65 g·cm^-3). Each fraction was characterized for SOC content, stable isotope composition (δ¹³C), and chemical functional group via Fourier-transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) was used to visualize particle morphology and elemental composition, while X-ray diffraction (XRD)identified dominant mineral phases in each fraction. Isotopic mixing models were applied to quantify biochar-derived C versus native SOC contributions across density gradients.【Result】The results showed that (1) Based on SOC content and soil minerals categories, density fractionation successfully separated soil into three functionally distinct pools: particulate organic carbon(POC, <1.85 g·cm^-3), clay mineral-associated C (1.85～2.45 g·cm^-3), and primary mineral-bound C (>2.45 g·cm^-3). XRD analysis confirmed that the 1.85～2.45 g·cm^-3 fraction was enriched in 2: 1 phyllosilicate (e.g., montmorillonite, illite) and Fe/Al oxides, whereas the >2.45 g·cm^-3 fraction contained quartz and feldspars. Fourier-transform infrared spectroscopy (FTIR) demonstrated that the intensities of O-H stretch (2 923 cm^-1) for aliphatic structures and C=C stretch (1 610 cm^-1) for aromatic compounds gradually decrease in both biochar application (C15) and non-application of biochar (C0) treatments with increasing density, while SOC stability progressively increased.(2)SOC content of density-specific changes varied under biochar amendment: Contribution of SOC in the <1.65 g·cm^-3 fraction increased by 150.1%, driven by biochar particles, while the 1.65～1.85 g·cm^-3 fraction showed a 60.9% increase, due to biochar-derived C adsorption onto clay minerals. Conversely, the 1.85～2.05 g·cm^-3 clay fraction exhibited a 37.4% reduction in SOC contribution. δ¹³C analysis confirmed biochar-C presence across all fractions, with the highest incorporation (64.5%) in the <1.65 g·cm^-3 fraction. Native SOC depletion was observed in five density intervals, with the most severe loss (-41.2%) in the <1.65 g·cm^-3 fraction, indicating strong positive priming. Notably, priming extended to the 1.85～2.25 g·cm^-3 clay fraction (-14.6%), suggesting biochar-induced microbial activity stimulated decomposition of relatively stable mineral-protected C.【Conclusion】This study demonstrates that biochar amendment effectively enhances total SOC content in paddy soil within two years, but its C sequestration efficiency is offset by priming-induced native SOC losses across labile and mineral-protected pools. The findings highlight the need to account for biochar-microbe-mineral interactions when evaluating long-term C sequestration. By linking density fractionation with spectroscopic and isotopic tools, this research advances understanding of mineral-mediated C stabilization in biochar-amended soils, providing a basis for optimizing biochar application strategies (e.g., feedstock selection, application rate) to maximize C sink capacity in rice-based systems. Future work should focus on long-term monitoring of priming effects and microbial community shifts to refine sustainable soil C management practices.

Abstract:【Objective】Grasslands play an important role in regulating the global carbon cycle through the decomposition of soil organic carbon (SOC) pools. However, the effects of global warming on SOC decomposition dynamics, and the underlying microbial and enzymatic regulatory mechanisms remain unclear. This study aims to investigate how warming alters the decomposition dynamics of active, slow, and passive SOC pools, with a focus on microbial community composition and extracellular enzyme stoichiometry. 【Method】This study was conducted using surface soil collected from semi-arid grasslands on the Loess Plateau in a long-term incubation experiment. Soil samples were incubated at two controlled temperatures (15 ℃ and 25 ℃) under constant temperature and humidity for 553 days (～1.5 year). During the incubation, soil respiration rates, microbial biomass carbon (MBC), extracellular enzyme activities, and microbial community compositions were systematically monitored. 【Result】The results showed that incubation at 25 ℃ significantly increased soil respiration rates, cumulative carbon emissions, and the decomposition rates of the three SOC pools (active, slow, and passive) compared to 15 ℃. However, the magnitude of this enhancement diminished over time. Among the SOC pools, the active pool exhibited the most rapid decline in respiration rate, followed by the slow pool, with the passive pool showing the slowest decline. Additionally, microbial biomass carbon and bacterial diversity decreased more rapidly at 25 ℃, accompanied by significant shifts in microbial community composition. The relative abundance of copiotrophic microorganisms, such as Proteobacteria and Ascomycota, decreased during the incubation, whereas oligotrophic microorganisms, including Actinobacteria and Ascomycota, increased. Notably, copiotrophic microorganisms were more dominant at 15 ℃, while oligotrophic microorganisms were more prevalent at 25 ℃. Microbial oxidative metabolism, nitrogen demand, and phosphorus demand increased progressively throughout the incubation, with overall higher levels observed at 25 ℃ compared to 15 ℃. Furthermore, the response of the three carbon pool decompositions to temperature increase was regulated by extracellular enzymes and microbial community composition. Stepwise linear regression showed that under 15 ℃ incubation, MBC and oxidases were positive regulatory factors for the decomposition of the active and slow carbon pools, respectively. Under 25 ℃ incubation, β-1, 4-N-acetylglucosaminidase, and alkaline phosphatase were positive regulatory factors for the decomposition of the passive carbon pool. The partial least squares path model analysis indicated that incubation temperature and time significantly regulated microbial community composition. The microbial community composition positively regulated extracellular enzyme activity and exerted negative and positive regulation on the decomposition of the slow and passive carbon pools, respectively. Also, extracellular enzymes, as key regulatory factors for the decomposition of the active and passive carbon pools, exerted negative and positive regulation on the decomposition of these pools, respectively.【Conclusion】This study reveals that shifts in microbial community composition, particularly the shift in species with different ecological strategies, play a key role in regulating extracellular enzyme activities and stoichiometry, thereby mediating temperature-induced changes in SOC decomposition dynamics. These findings provide critical insights into the microbial and enzymatic mechanisms that drive SOC turnover under warming conditions, offering valuable evidence to enhance our understanding of global carbon cycling and its feedback to climate change.

Abstract:【Objective】The priming effect(PE)is a key process in regulating soil organic carbon dynamics, but its mechanism is complex and substrate dependent, which limits the accuracy of model predictions. Therefore, it is necessary to clarify its regulatory mechanism. 【Method】This study is based on 2 122 sets of global observational data, combined with meta-analysis, process-based model analysis, sensitivity testing, and random forest methods, to systematically analyze the mechanism, dynamic process, and main controlling factors of PE under different carbon substrate conditions. 【Result】The results show that: 1) Both simple and complex carbon inputs induce significant positive PE, but the intensity varies significantly among ecosystems, with farmland PE intensity (about 65%) significantly higher than forest ecosystems (about 33%). Multivariate analysis reveales that this difference is mainly due to the coupled variation of climate, soil physicochemical properties, and microbial community structure characteristics along environmental gradients. 2) The priming pathway exhibits significant substrate specificity. Simple carbon input mainly induces strong positive PE through microbial triggering effects, while complex carbon input mainly inhibits the decomposition of native soil organic matter and generates negative real PE through the substrate priority utilization mechanism. 3) The results based on the process model further indicate that the dynamic process of PE is controlled by substrate quality. Simple carbon inputs exhibit two patterns: “continuous positive” and “transient”, while complex carbon input is dominated by a “high apparent-negative real” pattern. Also, parameter sensitivity analysis shows that this model is mainly constrained by microbial maintenance metabolism, reflecting the differences in energy allocation strategies of microorganisms under different substrate conditions. 4) Besides, the main controlling factors of PE have hierarchical differentiation characteristics, and the apparent PE is mainly driven by microbial biomass carbon and soil carbon-to-nitrogen ratio. Moreover, the main controlling factors of real PE depend on substrate type. In simple carbon scenarios, soil organic carbon content and pH are dominant, while in complex carbon scenarios, the governing factors shift to soil carbon-to-nitrogen ratio and exogenous carbon addition. 【Conclusion】By elucidating the controlling mechanisms of PE under different carbon substrate input conditions, this study provides evidence for the accurate prediction of soil organic carbon and the assessment of soil carbon balance in the context of global climate change.

Abstract:【Objective】Carbon cycling in paddy soils is crucial for carbon sequestration and soil fertility enhancement. The rice root zone, being the most active site of this cycle, exhibits carbon turnover processes that are closely linked to soil redox conditions and iron phase transformations. However, the iron-mediated organic carbon mineralization process under redox gradients remains unclear, and the carbon-iron coupling mechanism requires systematic elucidation.【Method】In this study, it is established a simplified rhizosphere microcosm system by using soil columns equipped with artificial roots. Four redox potential gradients of the soil column were constructed by adjusting water conditions (60%, 80%, and 100% of soil water saturation capacity, plus 3 cm flooding), and ¹³C-labeled glucose was used as a model root exudate, for investigating the effects of iron phase transformation on total organic carbon mineralization and priming effect in the root zone under different redox states.【Result】The results showed that: (1) Both soil Eh reduction and exogenous glucose input significantly increased the cumulative emissions of CH₄ and CO₂. Under water-saturated conditions, the incremental emission of CH₄ was significantly higher than that of CO₂ in the glucose-amended treatments, and vice versa in the unsaturated water content. (2) In both glucose-amended and non-amended treatments, soil dissolved organic carbon (DOC) content generally decreased compared to pre-incubation levels, but the aromaticity of DOC increased under saturated conditions. Eh reduction and glucose input stimulated ferrous iron (Fe²⁺) reduction and iron-associated organic carbon (Fe-OC) release, with Fe-OC content variations showing significant correlations with iron speciation and CO₂ emission rates. (3) The activities of carbon cycle hydrolase and oxidase were significantly affected by the redox gradient and glucose input. Cellobiohydrolase (CBH) activity decreased with decreasing Eh and showed a negative correlation with CH₄+CO₂ emission rates. Moreover, phenol oxidase activity was higher in the saturated water treatments than in the unsaturated water treatments and was positively correlated with the rate of gas emission. Glucose addition significantly increased the activities of phenol oxidase and catalase oxidase. 【Conclusion】Both the “iron gate” and “enzyme latch” mechanisms synergistically regulated CH₄ and CO₂ emissions. The findings provide critical parameters and a scientific basis for predicting rhizodeposited carbon sequestration potential in subtropical iron-rich paddy soil, and optimizing water management strategies to enhance carbon storage and mitigate greenhouse gas emissions in rice cultivation systems.

Abstract:【Objective】Soil organic nitrogen directly reflects the nitrogen supply capacity of soil. Therefore, it is important to clarify the mechanism of the effect of organic fertilizer on soil organic nitrogen components. 【Method】This study was based on the long-term positioning experiment started in 2008, and four fertilization treatments were set up (no fertilization CK, single application of organic fertilizer M, single application of chemical fertilizer NPK, and combined application of organic and inorganic fertilizer MNPK) to explore the effects of long-term different fertilization on the content of soil organic nitrogen components in apple orchards on the Weibei dryland. Besides, the key mechanism of increasing organic fertilizer to improve soil organic nitrogen content was studied through soil organic nitrogen component determination and metabolomics analysis of nitrogen metabolites. 【Result】The results showed that compared with NPK treatment, the contents of soil water, available phosphorus, available potassium, soluble organic nitrogen, and microbial biomass nitrogen in MNPK were increased by 4%, 33.8%, 41.7%, 8.2%, and 21.7%, respectively. Also, the content of acid hydrolyzed total nitrogen and acid ammonium nitrogen increased by 10.1% and 8.9%, respectively. The amino acid nitrogen content of M treatment was significantly higher than those of other treatments during the whole growth period, followed by MNPK, and CK was the lowest. Soil organic nitrogen components were significantly positively correlated with soil total nitrogen, microbial biomass nitrogen, and available nutrients (available phosphorus and available potassium). Except for non-acid hydrolyzable nitrogen, each organic nitrogen component was significantly positively correlated with acid-hydrolyzed total nitrogen. Metabolome results showed that the nitrogenous organic compounds in MNPK treatment were significantly higher than those in other treatments, and the proportion of amino acid nitrogen in the application of organic fertilizer treatment was higher than those in other treatments. Compared with NPK and CK treatments, amino acids accounted for an important proportion of nitrogenous organic compounds upregulated by MNPK treatment, and 8 amino acids were included in 45 nitrogenous organic compounds. The relative abundance was significantly positively correlated with available phosphorus, available potassium and soluble organic nitrogen. 【Conclusion】 The results showed that the improvement of soil physicochemical properties with increased application of organic fertilizer was conducive to organic nitrogen decomposition and turnover of amino acid nitrogen.

Abstract:【Objective】Nitrous oxide (N₂O) is a potent greenhouse gas with a global warming potential 296 times that of carbon dioxide (CO₂). Microbial-driven nitrification and denitrification are major processes contributing to N₂O production. While numerous studies have explored the combined effects of biochar and organic fertilizer, most have been short-term, and the legacy effects of aged biochar on soil N₂O emissions remain poorly understood. The interactive effects of its combined application with organic fertilizers necessitate further investigation. 【Method】Soil samples were obtained from a seven-year field experiment comprising four distinct treatments: (1) control (urea application, F); (2) one-time basal application of biochar (FB); (3) annual application of organic fertilizer (OF); and (4) combined annual application of organic fertilizer and one-time basal biochar (OFB). In the organic fertilizer treatments, 25% of the urea nitrogen was substituted with organic fertilizer nitrogen. A laboratory incubation experiment was conducted to measure cumulative N₂O emissions, quantify the abundances of key functional genes (including nirS, nirK, and nosZ), and partition the relative contributions of fungal and bacterial pathways to N₂O emissions. 【Result】The result showed that compared to the control, cumulative N₂O emissions were significantly reduced by 49.4% in the biochar treatment (FB), 38.4% in the organic fertilizer treatment (OF), and 59.3% in the combined treatment (OFB). Biochar significantly decreased the fungal contribution to N₂O emissions (FDC) by 11.4% and increased the bacterial contribution (BDC) by 5.8%. Organic fertilizer reduced the contribution of ammonia-oxidizing bacteria (AOB) by 15.3% but increased the bacterial contribution by 12.1%. The combined application of biochar and organic fertilizer decreased the fungal contribution by 9.7% and increased the bacterial contribution by 15.7%. Structural equation modeling (SEM) indicated that biochar directly reduced FDC and enhanced BDC, organic fertilizers significantly enhance BDC and reduce (nirS+nirK)/nosZ, thereby decreasing N₂O emissions. 【Conclusion】These results demonstrate the sustained potential of biochar and organic fertilizer amendments in reducing greenhouse gas emissions from agricultural soils and provide mechanistic insights into how these amendments regulate microbial processes governing N₂O production. This research outcome provides scientific support for in-depth analysis of the legacy effects of biochar and organic fertilizer application on soil and their microbiological mechanisms offering scientific guidance for optimizing fertilization practices to achieve the goal of reducing N₂O emissions from farmland soils.

Abstract:【Objective】The substitution of organic fertilizer for chemical fertilizer is becoming a popular practice for improved crop productivity. However, there is limited understanding of the nutrient stoichiometric relationships among crops, soil, and microorganisms under different proportions of organic fertilizer substitution for chemical fertilizers in a rice-wheat rotation system. 【Method】This study utilized a five-year field experiment at the Yixing experimental site of the Changshu Agro-Ecological Experimental Station, Chinese Academy of Sciences, to investigate the effects of organic fertilizer substitution on crop-soil-microorganism stoichiometric ratios and phosphorus availability under equivalent nitrogen, phosphorus, and potassium inputs. Five treatments were established: no phosphorus fertilizer (CK), conventional chemical phosphorus fertilizer (CF), 30% substitution of chemical phosphorus fertilizer with organic fertilizer (TM), 50% substitution (FM), and 100% substitution (HM). 【Result】Results from ten consecutive cropping seasons over five years revealed no significant differences in the grain and straw yields of rice and wheat or the total carbon, nitrogen, and phosphorus stoichiometric ratios among treatments. The stoichiometric ratios of available nutrients in the soil, including dissolved organic carbon: available nitrogen, dissolved organic carbon∶ available phosphorus, and available nitrogen∶ available phosphorus, ranged from 7.08-7.39, 23.1-26.8, and 3.59-4.06, respectively, under the TM, FM, and HM treatments. Compared with CF, these treatments did not significantly alter the total nutrient stoichiometric ratios in the soil but significantly increased the soil organic phosphorus fractions by 49.7%-58.2%, dominated by moderately labile organic phosphorus (NaOH-P_o). Additionally, soil microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus(MBP)in soil increased by 14.3%-61.1%, 4.37%-36.2%, and 46.4%-50.8%, respectively. The microbial stoichiometric ratios under all treatments were as follows: MBC∶MBN(11.6-14.5), MBC∶MBP(68.3-106), and MBN∶MBP(5.32-7.32). The TM and FM treatments significantly reduced the stoichiometric ratio of enzyme activity (EEA_(C∶N)) but did not affect the overall soil-microorganism stoichiometric balance. 【Conclusion】These findings demonstrate that substituting 30% of chemical fertilizers with organic fertilizers can maintain crop yields while effectively enhancing soil available phosphorus content. This study underscores the critical importance of scientifically regulating the substitution ratio of organic fertilizers to optimize soil nutrient management, improve soil fertility, and promote sustainable agricultural development.

Abstract:【Objective】Bridge construction strongly affects the structure and function of soil microbial communities in coastal wetlands. However, its specific impacts on mangrove soil fungal communities have not been given much attention. This study aimed to investigate the impacts of bridge construction on mangrove soil fungal communities, focusing on two common construction methods (Steel casing pipe, SC; Sheet pile cofferdam, SP) compared to undisturbed areas (UD), providing insights for ecological conservation and sustainable management.【Method】Soil fungal communities across SC, SP, and UD habitats were investigated using high-throughput sequencing, functional guild annotation, and co-occurrence network analysis. Key soil properties were measured to identify environmental drivers.【Result】The results showed that the main fungal biomarkers in the soils of the UD and SC habitats were Ascomycota, whereas the SP habitat was dominated by Basidiomycota. Also, the species richness of the soil fungi in the SP habitat was significantly (P< 0.01) higher than that in the SC and UD habitats. In addition, the species richness of saprotrophic fungi was significantly (P <0.05) higher in SP than in SC and UD, and the relative abundance of saprotrophic fungi was significantly (P < 0.05) higher in SC than in UD. The soil C/N ratio, TN, and pH were the main environmental drivers affecting fungal guilds. Fungal co-occurrence network analysis showed that the network complexity (avgK = 1.94) was higher in the UD habitat than in the SC and SP habitats.【Conclusion】This study reveals that bridge construction methods differentially alter mangrove soil fungal communities through soil physicochemical alterations. These findings highlight the need for method-specific environmental assessments and offer a scientific basis for balancing coastal wetland conservation with construction activities.

Abstract:【Objective】This study aimed to investigate the regulatory differences of various organic fertilizers on the rhizosphere microorganisms, nematode communities, and nutrient absorption of jackfruit, so as to select suitable organic fertilizers to construct a healthy soil microecology, and provide a theoretical basis for targeted regulation of soil quality.【Method】Malaysian No.1 grafted seedlings were used as experimental materials, and the latosol formed by granite was used as test soil in this study. The experiment was designed to have six treatments: CK(no fertilizer), DF(soybean flour), YF(sheep manure), JF(chicken manure), NF(cow manure), and CF(chemical fertilizer only), for comparing the effects of different fertilizers on the biomass accumulation, nutrient absorption, and soil microenvironment of jackfruit. 【Result】The application of organic fertilizer generally promoted the biomass accumulation and nutrient absorption of jackfruit, and increased the soil pH and organic matter. NF significantly improved the proportion of soil organic matter, available nitrogen, and potassium nutrients, but significantly reduced the proportion of soil available phosphorus compared to other treatments. The application of JF also significantly increased the contents of soil available nitrogen, phosphorus, and potassium; however, YF treatment induced the weakest effect among all organic fertilizer treatments. Also, the YF treatment had the highest number of soil nematodes and nematode abundance in each trophic group, followed by the NF treatment. The Shannon-Weiner diversity index and evenness index of soil nematodes in the organic fertilizer treatment were significantly higher than those in the CK and CF treatments. In addition, the soil microbial communities under different fertilization treatments all exhibited relatively active metabolism towards carbohydrates, amino acids and carboxylic acids, while their metabolic capabilities towards polymers, phenolic acids, and amides were weaker. The diversity and evenness index of soil microbial community structure in the DF treatment were significantly higher than those in other organic fertilizer treatments. Mantel analysis showed a significant correlation between plant biomass, nematode community, nematode trophic groups, microbial carbon source utilization, and soil pH. Also, the Mantel analysis of nematode community, bacterial-feeding nematode, and omnivorous/predacious nematode with soil organic matter showed significant correlation. 【Conclusion】The application of organic fertilizer can promote the growth and nutrient absorption of jackfruit, increase soil organic matter, and improve soil microecology. Moreover, organic fertilizers from sheep and cow manure is beneficial for increasing the total number of soil nematodes and the number of nematodes in each trophic group, while soybean flour can enhance the activity of rhizosphere microorganisms and promote carbon source utilization. For practical applications, specific organic fertilizers or their combinations can be selected based on the basic soil conditions for targeted regulation of soil health, providing a theoretical basis for high crop yield and efficient resource utilization.

Abstract:【Objective】Soil microorganisms serve as crucial mediators, bridging organic and inorganic environmental factors. They play a significant role in regulating multiple soil functions. Forest management represents the primary anthropogenic disturbance to forest soils, yet the mechanisms through which soil microorganisms influence soil multifunctionality (SMF) under continuous intensive management remain unclear. 【Method】This study investigated Carya cathayensis var. dabeishansis secondary forests in the Dabie Mountains to explore the mechanisms by which soil microbial diversity affects SMF under sustained intensive forest management. The authors analyzed 45 plots under varying management durations (0, 3, 8, 15, 20 years) and management metods (CK: no management; EM: extensive management; IM: intensive management)in Jinzhai County, Anhui Province. The soil microbial diversity (amplicon sequence variant, ASV) number, Simpson index, Shannon-Wiener index, and Chao1 richness index for bacterial and fungal communities) and 15 indicators related to four soil functions: nutrient supply (alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), available potassium(AK), microbial biomass nitrogen(MBN), microbial biomass phosphorus (MBP)); nutrient storage(total nitrogen (TN), total phosphorus (TP), total potassium (TK)); nutrient cycling (acid phosphatase (ACP), urease (UE), sucrase (SC), β-1, 4-glucosidase (BG), protease (Pro)); and carbon storage (soil organic carbon, SOC), microbial biomass carbon (MBC)) were measured. SMF was calculated using both the single-function approach and the averaging method. Two-way ANOVA was employed to compare management effects, while Pearson correlation, Mantel tests, and random forest models identified key functional indicators. Structural equation modeling (SEM) was constructed to analyze regulatory pathways. 【Result】The results indicated that short-term management (3 years) significantly enhanced soil microbial diversity and SMF(bacterial Shannon index peaked under IM at year 3; SMF increased by 0.94 compared to CK). However, both declined significantly with prolonged management, with bacterial ASV number and Shannon index decreasing by 19.63% and 3.46% after 20 years of intensive management, respectively. Management duration exerted a significantly greater impact on microbial diversity and SMF than management regime (P< 0.001), and IM amplified this temporal effect (e.g., carbon storage, nutrient cycling, and supply functions under IM-15 were significantly lower than CK). Random forest analysis identified SOC, TP, MBC, AN, TK, MBN, SC, and BG as key indicators of SMF (P< 0.05). SEM revealed that microbial diversity influenced SMF by indirectly regulating soil nutrients and enzyme activities (explaining 57.4% of the variation): bacterial diversity positively drives nutrient and carbon storage. In contrast, fungal diversity governed nutrient cycling and carbon storage. Nutrient supply and storage functions were the core contributors to SMF, where TP and TK indirectly affected SMF by regulating AN, MBN content, and SC/BG enzyme activities. Moreover, long-term management induced soil acidification, SOC loss, and phosphorus limitation (TP significantly decreased after 15 years), impairing microbial community function. This subsequently reduced enzyme activities (e.g., SC, BG) and nutrient turnover efficiency, ultimately leading to SMF degradation.【Conclusion】 This study revealed that the loss of soil microbial diversity is a key factor in SMF degradation under long-term intensive forest management. Thus, optimizing management strategies (supplementing carbon/phosphorus fertilizers, reducing nitrogen fertilizer application, decreasing understory vegetation clearance frequency)to maintain soil ecological functions is highly recommended. These findings provide a theoretical basis for the sustainable management of economic forests in mountainous regions.

Abstract:【Objective】Soil bacterial communities are key drivers of ecosystem functions in facility-based agriculture. However, the regulatory effects of magnetized water (MTW) irrigation on the structure and function of soil bacterial communities under facility cultivation remain unclear. 【Method】In this study, soils from eggplant, cucumber, and pepper cultivation plots were used as research objects. The experimental design comprised irrigation treatments using MTW and non-magnetized water (NMTW). Employing high-throughput sequencing technology combined with functional prediction analysis (FAPROTAX), the study systematically evaluated the impact of MTW irrigation on bacterial community composition, diversity, and key environmental driving factors.【Result】The results demonstrated that MTW irrigation significantly increased the abundances of Proteobacteria and Actinobacteria bacteria in soils of all vegetable cultivation plots by 7.43%-61.94% and 1.95%-11.79%, respectively, while decreasing the abundance of Chloroflexi and Gemmatimonadetes by 3.98%-27.42% and 7.89%-9.62%, respectively. At the genus level, MTW irrigation increased the relative abundance of Streptomyces and Chryseolinea in plot soils across all vegetable cultivation systems. Moreover, alpha diversity analysis showed that MTW irrigation significantly increased the Chao1, ACE, and Shannon indices of bacterial communities in pepper cultivation plots by 21.27%, 26.74%, and 12.22%, respectively, while no significant changes in bacterial community diversity were observed in eggplant and cucumber cultivation plots. Also, the redundancy analysis (RDA) revealed that MTW irrigation altered the environmental factors influencing soil bacterial communities, with soil pH, available phosphorus, and total phosphorus being the key factors regulating the abundance of dominant bacterial phyla. Functional prediction (FAPROTAX) showed that MTW irrigation significantly promoted the enrichment of functional bacteria related to cellulolysis and nitrogen fixation, while reducing the abundance of functional bacteria associated with human pathogens.【Conclusion】This study elucidates the multidimensional impacts of MTW irrigation on soil bacterial communities in facility agriculture systems, specifically addressing compositional, functional, and ecological network characteristics. The findings establish a theoretical foundation for regulating soil bacterial structure and metabolic functions, optimizing microbial ecological networks, and promoting sustainable soil management in protected cultivation.

Abstract:【Objective】Reactive oxygen species (ROS) at the soil-water interface play a crucial role in carbon/nitrogen cycling and pollutant transformation. However, it is still unclear how biochar influences the formation of ROS at the soil-water interface. Thus, this study aims to explore the formation behaviors and factors influencing ROS generation at the soil-water interface containing biochar. 【Method】Under simulated solar illumination conditions, the probe capture method was used to quantitatively analyze the generation kinetics and mechanisms of three typical ROS (hydroxyl radical ·OH, hydrogen peroxide H₂O₂, and superoxide radical (O₂^·-) at the 10 g·kg^-1 biochar-amended soil-water interface. The effects of biochar pyrolysis temperature, dissolved biochar carbon (DBC), clay minerals (kaolinite), and dissolved organic matter (fulvic acid) on ROS formation were also examined at such interfaces. 【Result】The results showed that under light, substantial ·OH and H₂O₂ were generated at the biochar-containing soil-water interface, with concentration ranges of 0.43-0.83 μmol·L^-1 and 21.12-30.93 μmol·L^-1, respectively, which were 1.39-2.65 times and 1.31-1.91 times higher than those at the biochar-free interface (control group). In contrast, O₂^·- concentration was low (< 0.2 μmol·L^-1), significantly lower than that in the control. DBC played an important role in the formation of ROS, and after removing DBC, the generation of H₂O₂ in the water-soil interface containing biochar was significantly inhibited, but the generation of ·OH was not affected. Also, kaolinite significantly inhibited the capacity of biochar to mediate ROS generation at the soil-water interface under light (except for high-temperature biochar) and reduced the conversion efficiency of H₂O₂ to ·OH. Fulvic acid significantly enhanced H₂O₂ generation at the light-irradiated, biochar-containing soil-water interface but decreased ·OH concentration.【Conclusion】Light plays a critical role in mediating ROS formation at the biochar-amended interface: it not only promotes H₂O₂ generation and transformation, but also facilitates ·OH production and O₂^·- conversion. However, biochar-mediated ROS generation at the interface is not entirely dependent on light. The generation of ROS at the light-irradiated, biochar-amended soil-water interface is collectively determined by biochar surface persistent free radicals, oxygen-containing functional groups, as well as dissolved organic carbon and Fe²⁺ contents at the interface. These findings provide an important reference for understanding the formation and distribution of ROS in biochar-amended soils.