Organic, inorganic, and microbial contaminants in soil and wastewater pose critical risks to human health, agricultural productivity, and environmental sustainability. Heavy metals (HMs) such as Cd, Pb, Ni, and Cr are of particular concern due to their non-degradable nature, long-term mobility, and ability to bioaccumulate in food chains. Conventional remediation techniques, including membrane filtration, chemical precipitation, and electrochemical treatments, are often costly, energy-intensive, and less effective for large-scale or mixed-pollutant systems. In this context, biochar has emerged as a multifunctional, carbon-rich material with physicochemical properties that support the immobilization, adsorption, and degradation of a wide range of contaminants. This review provides an integrative, mechanism-driven assessment of biochar-based remediation that goes beyond descriptive summaries. Specifically, it (1) links biochar production methods and physicochemical properties to contaminant-specific removal efficiencies across soil and wastewater systems; (2) critically analyzes direct and indirect HM adsorption mechanisms, emphasizing their interactions with soil biogeochemical processes and long-term stability; (3) synthesizes emerging evidence on biochar-plant defense crosstalk, demonstrating how reduced metal bioavailability modulates reactive oxygen species (ROS), membrane integrity, and antioxidant responses under stress conditions; and (4) evaluates biochar within a circular economy framework by integrating waste valorization, energy recovery, environmental trade-offs, and techno-economic feasibility. By coupling mechanistic insights with system-level analysis, this review identifies the key knowledge gaps related to biochar aging, contaminant remobilization, and field-scale validation, and guides developing resilient soil-plant-water remediation strategies.

Limited and uneven precipitation constrains maize production and water use efficiency (WUE) in the rainfed Loess Plateau. Organic fertilizer substitution reduces inorganic fertilizer inputs, but its effects on yield formation through stage-specific water consumption remain unclear. A field experiment was conducted from 2021 to 2024 within a long-term trial established in 2016 under the fully mulched ridge-furrow system. Treatments comprised 0% (T1), 50.0% (T2), 37.5% (T3), 25.0% (T4), and 12.5% (T5) organic fertilizer N substitution and a no-fertilizer control (T6); T1–T5 received 200 kg N ha-1. T3 achieved a four-year mean grain yield of 7129.2 kg ha-1, 12.88%–29.00% higher than the other substitution treatments, comparable to T1, and with the lowest yield variability. Its WUE reached 24.85 kg ha-1 mm-1, exceeding the other substitution treatments by 17.27%–33.82%. In 2021 and 2022, pre-sowing soil water storage under T3 was 9.19%–10.59% higher than selected fertilized treatments. Mean total water consumption was 290.3 mm and did not differ among fertilized treatments. However, T3 reduced the proportion consumed during early vegetative growth and increased that during R1–R3. T3 also maintained relatively high kernel number and 1000-kernel weight and a relatively high source-sink ratio. Structural equation modeling showed that silking to the milk stage (R1–R3) water consumption affected yield mainly through kernel number, whereas pre-sowing soil water storage acted mainly through 1000-kernel weight. Overall, 37.5% organic fertilizer N substitution maintained a favorable pre-sowing soil water status, optimizing water consumption structure by decreasing vegetative growth stage water consumption and increasing R1–R3 water consumption without increasing total water consumption, coordinating sink capacity with post-silking assimilate supply, thus improving WUE, and increasing grain yield.

Conservation tillage is a primary strategy in dryland farming systems, that can significantly improve water productivity in dryland crops. However, the mechanism of conservation tillage drives optimization of root water uptake and evapotranspiration (ET) components to enhance efficient water utilization is unclear. Therefore, a two-year field experiment was carried out with spring wheat based on a long-term conservation tillage experiment in a semiarid region of Northwestern China to determine root water uptake, quantify evaporation and transpiration, and assess their relationship with yield and water use efficiency (WUE) under different tillage and straw management practices. The treatments were conventional tillage (CT), no tillage with no straw returning (NT), conventional tillage with straw returning (CTS), and no tillage with straw returning (NTS). Stable oxygen isotope (18O) analysis was used to determine root water uptake, evaporation (E) and transpiration (T). The results showed that wheat root absorbed water from greater depths as the growth stages advanced, and water was absorbed from deeper in the soil profile under NTS than other treatments. Transpiration changed greatly as the growth period advanced, with an initial increase, before then decreasing. The maximum transpiration occurred at jointing stage to flowering stage. Compared with CT, NTS, CTS, and NT decreased evaporation (E) and significantly increased transpiration (T) by 21.7%, 13.9%, and 7.2% in two growing seasons, respectively. Therefore, the transpiration to evapotranspiration ratio (T/ET) under NTS, CTS, and NT were 24.7%, 17.0%, and 11.1% higher than CT in two growing seasons, respectively. Our findings demonstrate that conservation tillage not only enhances root water uptake from deeper soil but also optimizes ET components by enhancing T while reducing E, thereby improving WUE in wheat. The integration of no-tillage with straw returning under NTS produced a synergistic effect that further optimized root water uptake and ET components, resulting in the greatest enhancements in both grain yield and WUE. Elucidation of this underlying physical mechanism advances the understanding of efficient water utilization in wheat under conservation tillage, thus providing insights for selecting appropriate conservation tillage in semiarid regions.

Ridge-furrow plastic film mulching effectively mitigates water scarcity on the Loess Plateau, but its long-term sustainability is questionable. Strip intercropping offers a more water-efficient alternative to traditional monocropping. To investigate the dynamics of water-use and crop productivity under different strip intercropping systems, a three-year field experiment (2018-2020) was conducted. Four maize-based intercropping systems (maize-pea, M/P; maize-millet, M/G; maize-potato, M/S; maize-wheat, M/W) were compared with monocropping maize (MM). Crop yield, water consumption, water equivalent ratio (WER), land equivalent ratio (LER), and economic profit were analyzed. The soil water content was varied with season, soil layer, and cropping system. Maize-wheat intercropping (M/W) extracted water from below 140 cm depth. In contrast, monocropping maize under plastic film mulching showed a soil water deficit only in the 20-60 cm layer, and only at the end of the 2018 growing season. Regarding crop yield, the monocropping maize system (MM) achieved a yield of 9732 kg ha(-1), while the maize-based intercropping systems (except M/S) showed yield reductions of 27.8-32.1% relative to MM. In contrast, LER and WER increased by 2.9-20.3% and 2.4-17.6%, respectively. Compared with monocropping maize, maize-potato intercropping (M/S) achieved higher crop yield and net income, whereas maize-pea intercropping (M/P) exhibited lower yield but greater water savings (Delta WU) and a higher input-output ratio (1.91). Despite a moderate input-output ratio, M/S showed superior performance in yield, net revenue, and water equivalent ratio (WER). These findings indicate that appropriate intercropping systems, especially M/S, can reduce soil water consumption while improving economic returns and land use efficiency. Based on a comprehensive assessment of crop productivity, economic benefit, water use efficiency, and land use efficiency, maize-potato intercropping is recommended as the most effective and sustainable system for rainfed farming on the Loess Plateau.

Tillage and nitrogen (N) management are key drivers of soil fertility and microbial processes in semi-arid agroecosystems. However, their combined long-term effects under the commonly adopted plastic film mulching system remain poorly understood. In this study, plastic film mulching was applied uniformly across all treatments to conserve soil moisture and temperature, reflecting standard agronomic practices in the semi-arid Loess Plateau of China. A multi-year field experiment was conducted to assess four tillage practices (conventional, rotary, no-tillage, and subsoil) combined with two N rates (200 and 300 kg N ha-1). Maize yield, soil properties, and N-cycling functional groups (amoA-AOA, amoA-AOB, nirK, nirS, and nosZ) were analyzed. Results showed that tillage and its interaction with N significantly influenced crop yield, soil fertility, and microbial community composition, whereas N rate alone had minimal effects. Subsoil tillage with 200 kg N ha-1 (T4N2) increased maize yield and biomass by 13.7 % and 13.2 %, respectively, compared with rotary tillage. No-tillage and subsoil tillage with moderate N input improved soil water content (15-20 %), total N (10-12 %), available P (18-20 %), SOC (12-15 %), and the C:N ratio (8-10 %) relative to rotary tillage. These practices enriched beneficial nitrifiers (Nitrosospira) and denitrifiers (Sinorhizobium, Thauera, Pseudomonas), which were positively correlated with nutrient availability and yield. Structural equation modeling revealed that tillage improved soil C and N status, which stimulated denitrifier diversity and indirectly enhanced maize productivity. Overall, conservation tillage with moderate N input under film mulching offers a practical strategy to improve yield, increase N use efficiency, and foster beneficial microbial communities in semi-arid drylands.

In the context of food security and climate change mitigation, enhancing the stability of soil aggregate-mediated organic carbon (C) is crucial for long-term soil C sequestration in arid agroecosystems. Nitrogen (N) input, while essential for boosting crop productivity, profoundly influences soil aggregation, microbial activity, and the distribution of soil organic carbon (SOC) among functional pools. However, the mechanisms through which N regulates aggregate-associated SOC stabilization via microbial-mediated processes remain poorly understood. This review synthesizes recent advances on the effects of N input on soil aggregate dynamics, aggregate-associated SOC fractions, and microbial functional regulation in arid agricultural systems. We emphasize how N-driven shifts in microbial community composition, extracellular enzyme activities, functional genes, and glomalin-related processes influence aggregate formation and SOC protection. The novelty of this review lies in developing an integrated conceptual framework linking N input, soil aggregation, microbial functional responses, and aggregate-scale SOC stabilization. Our synthesis provides mechanistic insights to optimize N management strategies, thereby enhancing soil aggregate stability and maximizing long-term C sequestration, thereby promoting sustainable agriculture and climate change mitigation in arid regions.

A field study was performed in the semi-arid Loess Plateau, China, to explore how different tillage methods improve drought tolerance in wheat by examining plant growth, fungal communities, and soil properties. Four tillage methods were applied for wheat cultivation: (1) T (conventional tillage with no straw), (2) NT (no-tillage with no straw cover), (3) TS (conventional tillage with straw incorporated), and (4) NTS (no-till with straw cover) and data were collected in 2020 and 2021. The results showed that NTS treatment remarkably improved soil physicochemical properties during 2020 and 2021, increasing soil water content by 13.7-62.1 % compared to T at 0-50 cm soil depth. The NTS treatment had the lowest soil bulk density and pH and the highest total N, NO3- -N, and available P. Compared to T, NTS treatment significantly increased endophytic fungal Sobs index and genera like Alternaria, Peyronellaea, Sarocladium, and Schizothecium. The NTS and TS treatments significantly increased antioxidant enzymes, including CAT, POD, and soluble protein by 1.26-25.52 % compared to T. NTS treatment significantly increased yield by 23.64 and 24.28 % and water use efficiency by 16.06-19.97 % compared to T in 2020 and 2021, respectively. The endophytic fungal abundance (Sobs and Chao indices), diversity, and composition (Alternaria, Peyronellaea, Sarocladium, and Schizothecium) in wheat roots were positively correlated with the drought tolerance index, with soil water content, total N, and NO3- -N, being considered as key influencing factors. Collectively, NTS treatment showed the highest drought tolerance in wheat crop by improving soil physicochemical properties and utilizing the microbiome potential, ultimately enhanced water use efficiency and crop yields. Our study findings suggest that the NTS treatment is a promising practice for the semi-arid Loess Plateau area and may further guide future research on harnessing the emergent functions of microbial communities to enhance drought tolerance in wheat cultivated in drylands.

Soil quality is a foundational determinant of grain yield, yet the mechanisms through which tillage and straw management practices influence soil quality and crop productivity remain inadequately characterized in semiarid agroecosystems. This study investigated the microbial mechanisms linking grain yield and soil quality index (SQI) across four practices-conventional tillage with straw removal (T), no-till with straw removal (NT), conventional tillage with straw mulching (TS), and no-till with straw mulching (NTS)-using a 23-year field trial in northwest China. Results showed that TS and NTS significantly enhanced SQI by 60.1%-79.4%, and increased grain yield by 20.5%-31.8% compared to T. In contrast, NT had no significant effect on SQI, or yield. Random forest and structural equation model analyses revealed that long-term straw mulching significantly improved soil quality through restructuring soil microbial community by elevated stoichiometric homeostasis, as reflected in the changes in SIMC:P and SIMC:N ratios. These physicochemical trait shifts alleviated microbial resource limitations, triggering a strategic transition from resource acquisition (A) to growth (Y) strategies. Consequently, the bacterial r/K-strategy ratio increases, while fungal communities become dominated by K-selected taxa. This ecological reconfiguration enhances microbial diversity and network complexity, which in turn amplifies extracellular enzyme activity, particularly for P-acquisition, ultimately elevating SQI, and improving grain yield. NTS exhibited the greatest potential for yield enhancement due to its superior capacity to co-activate microbial and soil quality improvements. This study provides a theoretical basis for understanding the microbial mechanisms underlying long-term conservation tillage impacts on crop yield and soil quality in semiarid regions.

IntroductionTillage and straw management practices play an important role in improving wheat production in rainfed regions. This study aimed to investigate the underlying mechanisms from the perspective of how these practices affect sugar metabolism in flag leaves and grains, as well as the yield formation process of wheat on the Loess Plateau of China.MethodsThis research was conducted in 2023 and 2024 based on a long-term tillage experiment initiated in 2001. The experiment included four treatments: conventional tillage (T), conventional tillage with straw incorporation (TS), no-tillage with no straw (NT), and no-tillage with straw mulching (NTS).ResultsCompared with the T treatment, the NTS treatment significantly increased soil water content by 8% and flag leaf water content (FWC) by 13%. Correlation and path analysis indicated that higher FWC was associated with enhanced activities of flag leaf sucrose phosphate synthase and flag leaf sucrose synthase. Concurrently, flag leaf sucrose content increased, and sucrose was efficiently transported to grains. In the grains, enhanced sucrose synthase activity was linked to increased sucrose cleavage and starch biosynthesis. Consequently, compared with the T treatment, the NTS treatment increased grain yield by 44% and water use efficiency (WUE) by 45%.DiscussionThis study demonstrates that NTS treatment can enhance grain yield and WUE by improving soil water status, optimizing flag leaf water status, and regulating sugar metabolism in flag leaves and grains. This highlights sugar metabolism as an important physiological link between conservation practices and improved wheat productivity in rainfed systems.

Vegetation restoration is an effective strategy to improve the ecosystem function of the Loess Plateau. Soil microbiomes play a critical role in maintaining soil multifunctionality (SMF). However, the role of aggregate-scale microbial communities and interactions in regulating SMF during vegetation restoration remains poorly understood. Here, we selected six types of vegetation restoration measures in the Loess Plateau, including natural grassland (NL), Medicago sativa (MS), Hippophae rhamnoides (HR), Caragana korshinskii (CK), Armeniaca vulgaris (AV), and Populus alba (PA), and used abandoned land (AL) as a control to identify key microbial mechanisms driving SMF at the aggregate scale. The results show that vegetation restoration increased bacterial diversity, fungal network complexity, and SMF, especially in AV. In contrast, fungal diversity and bacterial network complexity exhibited asynchronous dynamics across different-sized aggregates. Soil microbial diversity peaked at micro-aggregates (0.053-0.25 mm), while fungal network complexity increased with decreasing aggregate size. The structural equation model confirmed that fungal community composition in large macro-aggregates (>2 mm) and fungal network complexity in <2 mm aggregates were the key drivers of SMF. Our results emphasize the divergent mechanisms by which microbial properties influence SMF across aggregate sizes, highlighting the importance of fungal communities in maintaining soil ecosystem functions.

Appropriate tillage and nitrogen management are crucial for promoting carbon sequestration, improving yields, and sustaining rain-fed agriculture. However, the long-term effects of tillage and nitrogen rates on soil carbon sequestration under plastic film–mulched (PFM) dryland maize and their microbial and physicochemical mechanisms remain unclear. A long-term field experiment (2012–2020) was conducted on Calcaric Cambisol soils of the Chinese Loess Plateau using two factors: tillage methods (T1, conventional (20 cm); T2, rotary (15 cm); T3, no-tillage; and T4, subsoil tillage (35 cm) and nitrogen fertilization rates (200 and 300 kg N ha−1; N2 and N3). Tillage and its interaction with nitrogen significantly affected maize yield, biomass, soil aggregates, organic carbon fractions, cbbL gene expression, and carbon-sequestering microbial communities. Subsoil tillage with 200 kg N ha⁻1 (T4N2) increased the yield and biomass. Compared with rotary tillage, no-tillage and subsoil tillage with 200 kg N ha⁻1 (T3N2, T4N2) enhanced soil organic carbon (SOC), particulate organic carbon (POC), water content, pH, available phosphorus (AP), aggregation, and C:N ratio. T4N2 and T3N2 also showed higher cbbL expression, microbial diversity, and carbon-fixing taxa (Proteobacteria, Sphingomonas, Nitrosospira, Synechococcus, and Acidithiobacillus), promoting carbon sequestration and yield. Structural equation modelling revealed that tillage and nitrogen indirectly enhanced carbon sequestration and yield by altering the microbial composition. No-tillage or subsoil tillage with 200 kg N ha⁻1 under PFM significantly improved carbon sequestration and maize productivity in semi-arid regions.

The research aimed to assess the influence of conservation agriculture-based practice of no tillage and residue retention on the soil fungal diversity and carbon dioxide (CO2) emission at the flowering stage of field pea in a rotation system with spring wheat. The treatments in the experiment were no-tillage with stubble removed (NT), no-tillage with stubble retained (NTS), conventional tillage with stubble removed (T), and conventional tillage with stubble incorporated (TS). Bulk soil and rhizosphere soil fungi DNA were sequenced using fungal ITS (ITS2) region genes. Treatments NT and NTS recorded the greatest fungal ITS region operational taxonomic units (OTUs) however, they did not vary significantly (P < 0.05) among treatments. Fungal OTUs diversity indices in the bulk soil were greater compared to those of the rhizosphere soil. The predominant phyla were Ascomycota, Basidiomycota and rare fungi genus Kurtzmanomyces were found in the rhizosphere. A few fungi class taxa recorded significant (P < 0.05) positive and negative correlations between tillage, soil respiration and total carbon emission. The study highlights the strong implication for the practice of residue retention and no-tillage to improve soil fungi, carbon emission efficiency and promote conservation agriculture-based practices.

Introduction Optimizing nitrogen (N) fertilizer management is essential for sustainable crop production in semi-arid, rain-fed agricultural regions. This study evaluated the effects of different N-fertilizer rates on nutrient uptake, soil nutrient distribution, and N balance in spring wheat (Triticum aestivum L.) under dryland conditions.Methods The analysis was based on a long-term field experiment initiated 2003 in Dingxi, Gansu Province, China, with five N application rates: 0, 52.5, 105.0, 157.5, and 210.0 kg N ha-1 (designated as N1-N5).Results The study results showed that the concentrations and accumulations of N and K in wheat organs increased significantly with increasing N rates. However, both yield and nutrient uptake plateaued at105 kg N ha-1 (N3) and no statistically significant benefits were observed at higher N rates. In contrast, increasing N fertilization significantly reduced grain P concentration, with the N5 treatment showing a 17.80% decrease compared with N1. Soil nutrient responses exhibited clear vertical differentiation. Residual available N in the 0-100 cm soil layer increased significantly with increasing N rates, with a 32.20% increase under N5 compared with N1, whereas available P decreased by 31.49%. Available K showed redistribution characteristics, with the surface layer and enrichment in the subsoil. Nitrogen balance analysis indicated that the apparent N-use efficiency decreased from 95.12% to 39.71% as N rates increased, while the apparent loss rate shifted from negative to positive values, reaching 33.79% under N5. The N3 treatment achieved a near equilibrium N balance (8.69 kg ha-1), whereas the N5 treatment resulted in a substantial N surplus of 102.34 kg ha-1. Overall, an application rate of 105 kg N ha-1 was identified as the optimal N fertilizer rate for dryland spring wheat.Discussion This rate ensured adequate N uptake and grain yield, maintained high N use efficiency (NUE), minimized potential environmental risks, and achieved a balanced N supply-demand relationship.

Phosphorus (P) is one of the major limiting factors for agricultural crop production. Although a high-chemical-P fertilizer input ensures high yields, it also leads to increased soil P accumulation issues and depletion of non-renewable P resources. It is a great challenge to optimize P inputs, improve soil P use efficiency, and maintain high crop yields. This study aims to review the current efforts to utilize the soil accumulated-P (due to excessive P application) efficiency by maximizing biological potential and to provide feasible insights into nature-based solutions for high-P soil utilization in the future. Currently, we are confronted not only with the longstanding challenges of low P fertilizer utilization rates and substantial soil P accumulation but also with the emerging issue of an ongoing decline in soil C/P stoichiometry. Therefore, improving the biological potential of soil indigenous microorganisms using C/P ratio principles could be an effective approach to promote soil P mobilization and utilization by crops. In this context, we highlighted key mechanisms involved in microbially-mediated soil-P mobilization by building up microbial biomass P pool. Our findings demonstrate that the use of carbon (C) sources enhanced the biological potential for high-P utilization in soil. The higher or lower soil C/P causes competition among plants and microorganisms. However, the soil and microbe C/P thresholds could be a predictor of an intensive competition between plants and microorganisms for P. In this view, we suggest that integrating C/P stoichiometry principles into soil P management could be effective for optimizing P fertilizer application as part of sustainable agricultural practices.

Background:Tetrastigma hemsleyanum Diels et Gilg (Sanyeqing [SYQ]), a traditional anti-inflammatory herb, has been used to treat respiratory disorders. Aims:To elucidate the mechanism of SYQ flavonoids in mitigating acute lung injury (ALI). Materials and methods:An integrated approach combined network pharmacology, HPLC, lipopolysaccharide (LPS)-induced ALI mouse models, and NOD-like receptor thermal protein domain associated protein 3 (NLRP3)-activated cellular assays (LPS + nigericin). NLRP3 knockdown (siRNA) and molecular docking were employed for mechanistic validation. Results:Network pharmacology and HPLC identified procyanidin B1 and catechin as core active compounds targeting the NLRP3 inflammasome pathway. Animal experiments demonstrated that SYQ flavonoids can significantly alleviate pathological damage to lung tissue, reduce pulmonary edema, and inhibit the expression of pro-inflammatory factors, thereby exerting a protective effect against ALI. Furthermore, SYQ flavonoids exhibited protective effects against ALI by downregulating the expressions of interleukin (IL)-1β, IL-18, NLRP3, ASC, and caspase-1. Notably, when NLRP3 was knocked down using siRNA technology, it had no significant effect on the levels of IL-1β and IL-18, indicating that their therapeutic effects are mediated through the NLRP3 pathway. Finally, molecular docking confirmed that both catechin and procyanidin B1 exhibit strong binding affinities with NLRP3, providing a molecular basis for their targeted inhibition of the NLRP3 inflammasome. Conclusion:SYQ flavonoids alleviate ALI by specifically inhibiting the NLRP3 inflammasome, providing a mechanistic basis for its traditional use in lung inflammation.

AIMS:Fertilizers can significantly influence leaf senescence and hormonal regulation, which in turn impacts crop yield. Despite significant advancements in understanding fertilizer effects on plant growth, the specific molecular mechanisms through which fertilizers influence hormonal regulation and leaf senescence, and subsequent impact on yield, remain underexplored. This study addresses this critical gap by examining transcriptional, physiological, and molecular mechanisms in the semiarid regions of rainfed spring maize under long-term fertilizers. METHODS:Fertilizer treatments include no amendment (NA), inorganic fertilizer (CF), combined inorganic and organic fertilizer (SC), organic fertilizer (SM), and maize straw (MS) replicated three times. RESULTS:The highest number of differentially expressed genes (DEGs) were observed under CF (3972) followed by SC (1949) in comparison to NA, showing a strong effect of inorganic fertilizer on gene expressions. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that numerous genes involved in the biosynthesis of secondary metabolites, plant hormone signaling, photosynthesis pathways, and metabolic pathways showed varied expressions of up- and downregulation. Genes involved in the ethylene, abscisic acid, jasmonic acid, salicylic acid, and brassinosteroid pathways indicated their interaction and promoted leaf senescence, whereas those related to auxin and gibberellin pathways had minimal impact. In the ethylene pathway known to influence senescence, two ethylene receptor (ETR) genes (Zm00001d013486 and Zm00001d021687) were downregulated, whereas, two ethylene-insensitive proteins 3 (EIN2) genes (Zm00001d053594 and Zm00001d033625) showed upregulation in the CF, SC and SM treatments. Furthermore, 86 highly up-regulated genes involved in the photosynthesis pathway encompassing components such as photosynthesis antenna, photosynthesis complexes II, cytochrome complexes, photosynthesis electron transport, and ATP complex in SC and CF compared to SM and MS. CONCLUSION:In summary, the study finds that DEGs showed stronger responses to inorganic fertilizers, likely due to organic fertilizers decomposing at a slower rate. Nevertheless, transcriptional and physiological analyses indicate that the SC treatment sustainably enhances maize productivity without causing adverse environmental effects, outperforming the other treatments (NA, CF, SM, MS). These results provide new perspectives on genetic regulation and pathway discovery in rainfed maize cultivation in semiarid areas.

With the escalating application of chemical fertilizers, the potential for environmental pollution has increased significantly. Currently, the degradation of soil quality due to the indiscriminate use of chemical fertilizers poses a more pressing challenge than ever before, threatening both human food production and the environment. The utilization of organic amendments not only enables the efficient recycling of organic waste resources but also reduces the reliance on chemical fertilizers. Meanwhile, organic amendments play a crucial role in soil improvement, helping to stabilize and enhance crop yields. Numerous studies have investigated the impacts of organic amendments on various aspects of crop production, including soil biology, biochemistry, heavy metal accumulation, and greenhouse gas (GHG) emissions. However, these studies have predominantly focused on isolated aspects rather than adopting a comprehensive perspective. Therefore, a comprehensive analysis of the positive and adverse effects of organic amendments is important in optimizing fertilizer use to meet crop nutrient demands and advancing carbon-neutral agriculture. This study mainly explores the intrinsic mechanism of the influence of organic amendments on soil physicochemical properties, enzyme activity and microbial diversity, heavy metal contamination and mobility, and GHG emissions in farmland. Finally, recommendations for the future development of organic amendments are proposed for promoting green and sustainable agricultural practices.

ABSTRACT The bacterial phoD gene encoding alkaline phosphatase (ALP) plays a crucial role in the mineralisation of organic phosphorus (Po) to inorganic phosphorus (Pi). The purpose of this study was to explore the association between soil P fractions and the phoD ‐harbouring bacterial community. Based on a long‐term P fertilisation experiment in calcareous soil on the Loess Plateau (started in 2014), this study analysed the results of treatments including four P fertilisation rates: 0, 60, 120 and 180 kg P 2 O 5 ha −1 (denoted as P0, P60, P120 and P180, respectively). The abundance and community structure of the ALP‐encoding gene ( phoD ) were analysed by PCR amplification and high‐throughput sequencing, and the soil P fractions were measured using Hedley sequential fractionation approach. The majority of soil P was present in the form of HCl‐Pi, and P fertilisation significantly increased the contents of Resin‐P, NaHCO 3 ‐Pi, NaHCO 3 ‐Po, NaOH‐Pi, NaOH‐Po and HCl‐Pi in soil. The ALP activity and phoD gene abundance in the P120 and P180 treatments were significantly less than those in the P0 and P60 treatments: P180 decreased by 14.52% and 46.83% compared with P0, respectively. ALP activity was positively correlated with pH, but negatively correlated with the contents of Resin‐P, NaHCO3‐Pi, NaHCO3‐Po and NaOH‐Pi. P fertilisation decreased the relative abundance of the genera Streptomyces , Bradyrhizobium and Rhizobacter . Sinorhizobium had the highest abundance in low‐P (P60) soil and played an important role in improving ALP activity and bacterial community network stability. P fertilisation significantly affected the community assembly processes of phoD ‐harbouring bacteria, with high‐P input promoting stochastic processes in soil. Soil microbial biomass carbon (MBC) and microbial biomass phosphorus (MBP) contents significantly affected the abundance of phoD , while pH and MBP contents significantly affected the composition of the phoD bacterial community. ALP activity was significantly correlated with phoD gene abundance, which played a key role in promoting Po turnover and improving soil P availability. The decrease in soil pH and the increase of MBC and MBP contents caused by long‐term P fertilisation influenced the activity of ALP by regulating phoD gene abundance and community composition, thereby inhibiting the mineralisation of Po.

In order to reduce N2O emissions during composting, the effects of different nitrification inhibitors (NI), dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP), on compost maturity, N2O, and NH3 emissions were studied under continuous incremental addition. This study used pig manure and corn straw as composting materials, based on the total nitrogen (TN) content of the initial mixture, two treatments were set: DCD (2.5% in the early phase and 5.0% in the maturation phase) and DMPP (0.25% in the early phase and 0.75% in the maturation phase) in a composting experiment. The results showed that adding DCD and DMPP did not affect the compost maturity, with the seed germination index (GI) of final compost reaching 80.76%-97.06%. Before the maturity period of compost, ammonia (NH3) emissions accounted for 98.5%-99.4% of total emissions. Compared with the control group (CK), the addition of DCD and DMPP in the early stage reduced NH3 emissions by 8.85% and 12.83%, respectively, by decreasing the ammonification rate. During the mature stage of composting, N2O emissions account for 95.6%-98.9% of the total emissions. The addition of DCD and DMPP delayed N2O emissions by 4 and 6 days, respectively, through nitrification inhibition. The DMPP amendment also reduced cumulative N2O emissions by 54.50% and increased the nitrogen content of the final compost. Correlation analysis showed that N2O was mainly originated from the denitrification of nitrification substrate (NO2--N and NO3--N). This study provides technical support for low-carbon management of agricultural waste.

To investigate the effects of long-term alfalfa planting on the structure and diversity of soil ammonia-oxidizing microbial communities, this study conducted a field experiment in the semi-arid region of the Loess Plateau. Alfalfa fields planted in 2019 (L2019), 2012 (L2012), and 2003 (L2003) were studied, with farmland corn serving as the control (CK). High-throughput sequencing was used to examine the ammonia-oxidizing microbial communities and their interactions in alfalfa with varying planting durations. The results demonstrated that alfalfa planting significantly increased the levels of total nitrogen, and organic carbon compared to CK. The gene abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) increased with longer alfalfa planting durations. The ecological network analysis showed that at low planting years, species in the AOA community were mainly in a collaborative relationship, while species in the AOB community were mainly in a competitive relationship. This relationship changed at high planting years. Structural equation modeling indicated that planting duration was significantly correlated with Soil water content, total nitrogen, and ammonium nitrogen. Additionally, AOB communities were significantly positively correlated with NH4+-N and negatively correlated with nitrate nitrogen. Ecological null model analysis revealed that the assembly of AOA and AOB communities was primarily governed by stochastic processes, with uncertainty being a key factor in the random assembly process. Furthermore, the β-nearest taxon index (βNTI) of AOB was significantly correlated with Soil water content. This suggests that long-term alfalfa planting forms a stable soil environment, enhancing stochastic processes, which is conducive to maintaining the sustainability and stability of the artificial grassland ecosystem function.