Abstract:【Objective】The potential impact of biochar on key soil animals, especially earthworms, is an important aspect in evaluating its environmental safety. Although previous studies have confirmed the toxic effects of biochar on earthworms, there is still a lack of systematic understanding of how preparation conditions regulate its toxicity and the specific sources of toxicity. Thus, this restricts the screening and application of low-risk biochar. 【Method】The effects of biomass sources (rice straw and perishable waste) and pyrolysis temperature (350 ℃, 500 ℃, and 650 ℃) on the toxicity of biochar to earthworms were systematically investigated. Also, the toxicity differences between biochar and its extract solution were compared. Moreover, the common Eisenia fetida was used as the test subject, and multiple indicators were employed, such as individual survival rate, enzyme activity, histopathological observation, and transcriptomics, to evaluate the effect of biochar on the earthworm’s survival. 【Result】The main results indicated that: (1) The toxic effects of biochar on earthworms exhibited significant feedstock specificity and dose dependence. At an exposure dose of 2.5 g·kg-1, perishable waste biochar (PWB) significantly reduced the relative survival rate of earthworms, while the same dose of rice straw biochar (RSB) had no significant effect; when the dose increased to 5 g·kg-1, both types of biochar showed obvious lethal effects on earthworms. (2) The response of the oxidative stress system showed that biochar stimulated the antioxidant defense mechanism of earthworms. Moreover, as the pyrolysis temperature increased, the oxidative stress in the earthworms showed a decreasing trend. The integrated biomarker response further indicated that the ecological risk of PWB was higher than that of RSB, and the toxicity risk of biochar pyrolyzed at a lower temperature was stronger. (3) Histopathological analysis indicated that biochar can induce damage to the epidermis and midgut of earthworms, with the damage caused by PWB being more severe. Transcriptomics revealed that several key physiological pathways such as protein digestion and absorption, extracellular matrix (ECM)-receptor interaction, and vitamin digestion and absorption in earthworms, were affected under the exposure to biochar, and PWB induced more differentially expressed genes. (4) Biochar extract solution exhibited toxic tendencies to earthworms in the soil at a dosage of 5 g·kg-1, while the toxicity was lower than that of the solid biochar. This indicated that both the chemical composition toxicity of its extract solution and the physical characteristic risks of its solid particles should be considered for a comprehensive assessment of the ecological safety of biochar. 【Conclusion】Based on the above results, the toxic effects of biochar on earthworms in the soil are influenced by multiple factors such as the feedstock, pyrolysis temperature, dosage, and components of biochar. Thus, this study provides an important reference for research aimed at better assessing the environmental risks of biochar and provides a theoretical basis for the safe application of biochar in soil.

Abstract:【Objective】The combined application of biological nitrification inhibitors (BNIs) with chemical nitrogen (N) fertilizers reduces N loss and enhances nitrogen use efficiency (NUE). However, research on their combined use with organic N fertilizers remains limited, and their yield-enhancing effects and underlying mechanisms remain unclear. 【Method】This study employed organic Chrysanthemum morifolium Ramat cv. ‘Hangbaiju’ in field trials, establishing four treatments: no nitrogen application (-N), fish protein organic water-soluble fertilizer (N), N+50 g·kg-1 methyl 3-(4-hydroxyphenyl) propionate (MHPP), and N+50 g·kg-1 salicylic acid (SA). The research investigated the effects of combining BNIs with organic N fertilizers on chrysanthemum yield, quality, and the underlying synergistic mechanisms. 【Result】 Results indicated that the N+SA treatment yielded the highest harvest at 6 154 kg·hm-2, achieving a 40.2% increase in yield (P < 0.05), a 9.1% rise in total flavonoids (P < 0.05), and a 75.0% improvement in NUE (P < 0.05) compared to the N treatment. Compared with the N treatment, N+MHPP showed a trend of increasing yield and enhancing NUE. N+SA significantly increased total root length by 147.7% and fresh root biomass by 127%, with root-promoting effects significantly superior to N+MHPP. Principal component analysis indicated positive correlations between Chrysanthemum morifolium Ramat cv. ‘Hangbaiju’ yield and NUE with root length, root surface area, and root volume. It is speculated that the application of SA may achieve synergistic effects of “increased yield, enhanced efficiency, and improved quality” by optimizing the root architecture of Chrysanthemum morifolium Ramat cv. ‘Hangbaiju’, enhancing nitrogen uptake, and potentially exhibiting growth-promoting activity.【Conclusion】This study confirms the significant potential of BNIs in boosting yield, efficiency, and quality within organic water-soluble fertilizer systems, providing a new pathway for green and efficient fertilization of organic medicinal crops.

Abstract:【Objective】The intricate interactions between introduced plant growth-promoting rhizobacteria (PGPR) and the indigenous microbial community are pivotal determinants of inoculation efficacy and plant health. While the direct mechanisms of PGPR are well-studied, the role of resident microbes in modulating their activity remains less understood. This study focuses on Sphingomonas sp. HJY, a known growth-promoting bacterium for rice, aims to elucidate how specific indigenous bacteria influence its plant growth-promoting capacity and to uncover the fundamental mechanisms behind this interaction. Clarifying this synergy is crucial for advancing the knowledge of rhizosphere ecology and optimizing microbial inoculation strategies. 【Method】A batch of bacteria was isolated from rice rhizosphere soil, and indigenous bacterial helpers that promoted the growth of HJY were screened by both co-culture assay and supernatant-culture assay. The bacterium with the most pronounced promotion effect was selected as a representative and identified by full?length 16S rRNA gene sequencing. To elucidate the mechanism of facilitation, the selected helper strain was cultured under iron-rich and iron-limited conditions. Its siderophore production was quantified using the Chrome Azurol S (CAS) assay. Subsequently, the impact of its filter-sterilized supernatant from both iron conditions on HJY growth was compared. Finally, a pot experiment with natural soil was conducted to assess the influence of the indigenous bacterial helper on the ability of HJY to promote rice growth. 【Result】The results showed that the indigenous bacterium labeled B35 exhibited the most significant promotion effect on HJY growth. The biomass of HJY was increased by 71.2% and 95.4% by B35 cells and its sterile supernatant, respectively, with the latter being significantly more effective. This strain was identified as Bordetella petrii. Under iron?limited conditions, the siderophore secretion by B35 was significantly higher than under iron?sufficient conditions. Moreover, the iron?limited supernatant enhanced the growth?promoting effect on HJY by 13.89% compared with the iron?sufficient supernatant, indicating that siderophores secreted by B35 were one of the main factors promoting HJY growth. Soil inoculation experiments demonstrated that, at 18 days, the plant height, fresh biomass, chlorophyll content, and root length of rice treated with HJY + B35 sterile supernatant were increased by 5.9%, 11.6%, 12.7%, and 21.2%, respectively, compared with those treated with HJY alone. In contrast, the corresponding indices for rice treated with HJY + B35 cells were increased by 4.4%, 7.6%, 5.1%, and 8.0% compared with HJY alone. These results indicated that both B35 and its sterile supernatant could enhance the growth?promoting effect of HJY on rice, with the supernatant treatment showing a superior effect to the bacterial cell treatment. Inoculation with B35 alone or its supernatant alone had no significant effect on rice growth. 【Conclusion】 In conclusion, this study demonstrates that the indigenous bacterium Bordetella petrii B35 enhances the plant growth-promoting activity of Sphingomonas sp. HJY through a facilitative interaction driven largely by siderophore production. This interaction significantly improves HJY"s efficacy in promoting rice growth in natural soil, with the direct application of the helper"s metabolites yielding the strongest effect. These findings provide novel insights into the complex network of rhizosphere microbial interactions, highlighting how targeted exploitation of specific facilitative relationships—such as cross-feeding via siderophores—can be a crucial strategy for optimizing the performance of PGPR inoculants. This study, therefore, offers a theoretical foundation for designing more effective and stable synthetic microbial consortia for sustainable agriculture.

Abstract:【Objective】This study aimed to investigate the effects of different land use types and soil profiles on ammonia-oxidizing microorganisms and nitrogen (N) cycling processes, with a focus on the community distribution and functional roles of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and complete ammonia oxidizers (Comammox) in agricultural soils under different management regimes.【Method】Soil samples (0-100 cm) were collected from three typical farmland ecosystems in Changshu, Jiangsu Province, including rice-wheat rotation, orchard, and vegetable fields, during both spring and summer. Soil physicochemical properties were determined, and microbial community composition and abundance were analyzed using quantitative PCR and high-throughput sequencing. In addition, microcosm incubation experiments with nitrification inhibitors were conducted to determine nitrification and N2O production rates, enabling clear quantification of microbial contributions to soil nitrogen transformations.【Result】The ammonia oxidation rate and N2O emission rate of the surface soil are the highest, with mean values of 6.1 ± 1.0 mg·kg-1·d-1 (calculated by N, the same as below) and 17.9 ± 6.1 ng·kg-1·d-1, respectively, and both declined significantly with depth. The N2O emission rate in rice–wheat soils (17.5 ± 5.6 ng·kg-1·d-1) was significantly higher than that in vegetable soils (1.5 ± 0.5 ng·kg-1·d-1). Within the rice–wheat system, summer exhibited a significantly higher N2O emission potential than spring. Among ammonia oxidizers, AOB contributed most to nitrification, accounting for 56.6% in surface soils and up to 64.9% in subsurface layers, while the contribution of Comammox increased with depth. Microbial functional gene abundance and diversity showed pronounced vertical heterogeneity and were strongly influenced by land use type. Correlation analysis indicated that microbial gene abundance was significantly positively correlated with nitrification rates, and that ammonium nitrogen and dissolved organic carbon were the key factors regulating both nitrification and N2O emissions. Structural equation modeling further revealed that AOB gene abundance was a major determinant of ammonia oxidation rates and that ammonia oxidation processes were positively linked to N2O emissions.【Conclusion】This study systematically evaluated the effects of land use and soil profile on the functional differentiation of ammonia-oxidizing microorganisms. The findings demonstrated that AOB dominate ammonia oxidation across soil layers, while Comammox play an increasingly important role in deeper soils, and that both groups jointly regulate the potential mechanisms of N2O emissions. These results provide theoretical support for developing microbe-oriented strategies for agricultural nitrogen management.

Abstract:Nitrous oxide (N2O) is a potent greenhouse gas; thus, understanding its emission mechanisms from agricultural soils is a critical research priority. Previous studies have largely focused on macro-scale drivers like climate and management, leaving a gap in the systematic understanding of how micro-scale soil pore heterogeneity regulates N2O dynamics. This review addresses this gap by synthesizing current knowledge. It first examines how dynamic changes in soil pore characteristics (e.g., porosity, pore-size distribution, connectivity) govern the transport of water, gases (O2, N2O), and solutes, thereby creating distinct microenvironments for N2O production and diffusion. A key focus is the scenario of straw incorporation. The analysis details how straw management, encompassing application methods, duration, and straw type—interacts with soil physical structure and moisture regimes (particularly wetting-drying cycles) to reshape pore network heterogeneity. Building on this physical foundation, the review then analyzes the consequential biogeochemical effects. It highlights how pore-scale heterogeneity in the distribution and accessibility of carbon/nitrogen substrates and oxygen critically regulates microbial nitrogen transformation processes (e.g., nitrification and denitrification), ultimately controlling N2O production pathways and the emergence of emission “hotspots.” Furthermore, this synthesis consolidates potential micro-scale mitigation strategies that leverage pore structure manipulation. These include optimizing straw treatment (e.g., biochar production, particle size reduction) and targeting microbial communities to design microenvironments that suppress N2O formation or enhance its reduction to N2. In summary, by developing an integrated framework that links pore structure dynamics with microbial biogeochemistry, this review advances the mechanistic understanding of N2O emissions under straw incorporation. It provides a novel, pore-centric perspective and a theoretical basis for designing innovative farmland management practices aimed at reducing greenhouse gas emissions while supporting sustainable agriculture.

Abstract:【Objective】Soil resilience refers to the ability of soil to restore its original properties and functions after being disturbed by anthropogenic or climate change. It is an important ecological indicator for achieving the sustainable utilization of soil resources. This paper aims to construct a soil resilience evaluation system suitable for large-scale applications and assess the spatial distribution characteristics of soil resilience in China. 【Method】Based on existing research results, this study refines the logic of index construction, determines four dimensions: soil properties, climatic factors, topographic influences, and biological characteristics, and sets a total of nine specific indicators. The Analytic Hierarchy Process (AHP) is used to determine the weights of the indicators, and weighted superposition analysis is conducted to form a national spatial distribution map of soil resilience. 【Result】The results show that soil resilience in China presents a spatial pattern that gradually increases from West to East and from North to South. Nationwide, soils with high and relatively high resilience account for 25% and 39%, respectively, mainly concentrated in South and Southwest China. The areas with relatively low resilience include the Gansu and Xinjiang regions and the Loess Plateau Area. 【Conclusion】The research provides technical support and decision-making basis for establishing the evaluation of specific soil functions at the macroscopic scale in China at the theoretical and methodological level.

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:Magnesium (Mg) is an essential mineral element for plants, playing critical roles in photosynthesis, nutrient transport, stress responses, and nutrient use efficiency. However, the long-term ignorance of Mg fertilizers in China"s agricultural production has led to widespread soil Mg deficiency, which constrains crop yield, quality, and the potential for further improvement in nutrient use efficiency. This study provides a comprehensive assessment of soil exchangeable Mg status and Mg fertilizer use in China, based on integrated data from national surveys and field experiments conducted by the National Mg Network. It also evaluates the effects of Mg fertilizers in improving crop quality and nutrient use efficiency. In addition, it analyzes the national demand and usage of Mg fertilizers, thereby advancing the understanding of the fundamental physiological functions and agronomic roles of Mg in crop production. Survey results indicate that soil exchangeable Mg concentrations are generally higher in the northern regions (average 271.7 mg kg-1) compared to the southern regions (174.6 mg kg-1). The application of Mg fertilizers remains below 9%, with application rates far below than crop requirements. Mechanistic studies demonstrate that Mg directly participates in the light reactions of photosynthesis and carbon fixation, and regulates the circadian rhythms of photosynthesis. It also promotes nitrogen uptake and assimilation through improved carbon allocation and signaling pathways. Moreover, Mg exhibits multiple protective mechanisms under aluminum toxicity, salinity, and high-temperature stress, and activates plant immune responses to enhance disease resistance. Field trials show that appropriate Mg application can increase average crop yield by 14.6%. It also significantly improves the nutritional and sensory quality of agricultural products while improving the efficiency of nitrogen, phosphorus, and potassium fertilizer use. The estimated Mg fertilizer demand in China"s agricultural production is 2.81–4.40 million tons (as MgO), yet the current application of Mg fertilizer is just 150000 tons. The insufficient development and diversification of Mg fertilizer products remain a major bottleneck for the green development of Chinese agriculture. In the future, it is necessary to strengthen the basic and applied research on plant Mg nutrition, expand the production and supply chains of Mg fertilizers, and enhance policy support to promote large-scale adoption. These efforts will contribute to higher yield, better quality, improved nutrient use efficiency, and the sustainable development of Chinese agriculture.

Abstract:【Objective】Viruses play a crucial role in regulating soil microbial community and host dynamics. However, the efficient extraction and enumeration of soil viruses remain challenging due to the complexity of soil environments. This study aimed to enhance the efficiency of soil virus detection by optimizing both the viral extraction protocol and epifluorescence microscopy observation conditions. 【Method】Soil samples were collected from the long-term brown soil fertilization experimental station at Shenyang Agricultural University. Three key factors affecting soil virus extraction efficiency and enumeration results were evaluated: (1) antifade agents (the commercial anti-quenching agent Fluoromount-G? and a laboratory-prepared antifade agent); (2) disruption methods (blender, vortex mixer, ultrasonic cell disruptor, and water bath shaker); and (3) soil-to-liquid ratios (30:100 and 50:100; mass: volume). Viral particles were stained using SYBR Green I and enumerated under an epifluorescence microscope. The optimized protocol was subsequently applied to brown soil, black soil, and meadow soil to validate its general applicability. 【Result】Without an antifade agent (Fluoromount-GTM or laboratory-prepared antifade agent), viral particles were difficult to observe under the 100× objective. The application of Fluoromount-GTM significantly increased virus counts to 3.75 × 108 virus-like particles (VLPs)?g-1, outperforming the laboratory-prepared antifade agent. The disruption method significantly affected virus extraction efficiency (P < 0.05). The blender (650 W, 50 Hz) treatment for 3 minutes achieved the highest extraction efficiency, significantly surpassing the vortex mixer and water bath shaker, whereas no viral particles were observed with the ultrasonic cell disruptor treatment. In addition, increasing the soil-to-liquid ratio also significantly enhanced virus extraction efficiency (P < 0.05), with the 50:100 ratio resulting in a 1227.10% increase in virus counts compared to the 30:100 ratio. The validation results demonstrated that the optimized method consistently yielded stable and reliable viral counts across all three soil types, with significant differences in viral abundance observed among them, confirming its broad applicability. 【Conclusion】In summary, this study established an efficient, stable, and widely applicable epifluorescence microscopy method for soil virus enumeration through the systematic optimization of the disruption method, soil-to-liquid ratio, and antifade agent. The optimized method significantly enhances the extraction efficiency and counting accuracy of soil viruses, thereby providing robust technical support for soil viral ecology research.

Abstract:【Objective】This study aims to investigate the mechanisms and efficiency-enhancing pathways by which pelletized straw incorporation technology rapidly improves organic carbon content and its active fractions in sandy soils of the Horqin Sandy Land, addressing critical challenges of organic carbon pool depletion and poor water-fertilizer retention capacity.【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·ha-1 pelletized straw (PS75), and 150 t·ha-1pelletized 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. 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). Notably, the 150 t·ha-1 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. The observed highly significant positive correlations between particulate organic carbon (POC) and total SOC content (P<0.01), as well as between labile organic carbon (LOC) and total SOC content (P<0.01), provide compelling evidence for the pivotal role of these labile carbon fractions in driving overall soil organic carbon sequestration. 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. This indicates that the improvement mechanism of water-holding capacity in sandy soils can be attributed to the synergistic effects of physical adsorption and chemically mediated water retention derived from pelletized straw decomposition. RDA analysis identified MAOC and capillary porosity as key factors influencing soil carbon and nitrogen retention. MAOC emerged as the dominant driving factor, exhibiting the strongest explanatory power for variations in SOC, TN, and C/N ratio. Partial least squares path modeling demonstrated that the cumulative addition of pelletized straw showed a highly significant positive correlation with soil particulate organic carbon and readily oxidizable organic carbon (P< 0.01), pelletized straw application significantly promoted SOC and TN accumulation through regulating POC (p<0.05), with the carbon sequestration effect further improving soil water retention via reduced bulk density (p<0.05).In summary, the study demonstrated that particulate organic carbon (POC) served as the key mediator for carbon-nitrogen coupled stabilization in sandy soils. The establishment of this regulatory mechanism provided a theoretical foundation for carbon sequestration management in arid sandy soils.【Conclusion】The study demonstrates that pelletized straw incorporation effectively enhances sandy soil organic carbon fractions, promotes carbon-nitrogen synergistic sequestration, and improves soil physical properties, with the optimal effects achieved at 150 t·ha-1 with two consecutive years of application.