Search Results (90)

Nitrous oxide (N₂O) is recognized as a potent greenhouse gas, and 60% of atmospheric N₂O emissions come from cropland soils. Potassium (K) is an important fertilizer for rice paddy fields. K fertilizer decreased the abundance of functional genes mediating nitrification and denitrification processes, thereby mitigating N₂O emissions. However, few studies have explored the effect of K fertilization rates on N₂O emissions and grain yields, as well as the associated soil properties and aboveground N accumulation in paddy fields under different irrigation regimes. This study aimed to propose an optimum combination of K fertilization rate and irrigation regime to increase grain yield while reducing N₂O emissions. Here, a 2-year field experiment using a split-plot design with three replicates was conducted to assess the effect of three K fertilization rates (K₀: 0 kg ha⁻¹, K₇₅: 75 kg ha⁻¹, K₁₅₀: 150 kg ha⁻¹) on N₂O emissions, grain yield, aboveground N accumulation, and soil properties, including soil redox potential (Eh), NH₄⁺, NO₃⁻, soil gene abundance of AOA, AOB, nirK, nirS, nirK/nirS, and nosZ, under continuous flooding irrigation (I_CF) and alternate wetting and drying irrigation (I_AWD). The soil physicochemical properties, the gene abundance and the aboveground N accumulation were evaluated and used to explain how irrigation and K fertilization affect grain yield and N₂O emissions. We found that I_AWD significantly increased N₂O emissions by 38% compared to I_CF, and K fertilizer significantly reduced N₂O emissions by 15% relative to K₀. The effects of I_AWD and K fertilizer on N₂O emissions can be attributed to the combined impact of soil physicochemical properties and the abundance of functional genes governing N₂O emissions. Both irrigation regimes produced equivalent grain yield and aboveground N accumulation. Shifting from I_CF to I_AWD, the increase in N₂O emissions can be mitigated by K fertilization. Moreover, K₇₅ and K₁₅₀ had similar effects in reducing N₂O emissions and yield-scaled N₂O emissions, while K₇₅ had a lower K fertilizer cost and higher K partial factor productivity. Therefore, applying K fertilizer at 75 kg ha⁻¹ under I_AWD is identified as a potentially suitable rate to secure grain yield while effectively mitigating N₂O emissions. Full article

To investigate the effect of high-arsenic (As) soil on the absorption of As by highland barley, 135 pairs of soil–crop samples were collected in the main producing areas of highland barley in the middle reaches of the Yarlung Zangbo River. Eight soil variables, including pH, redox potential (Eh), soil organic matter (SOM), total arsenic (T-As), total iron (T-Fe), total manganese (T-Mn), chemically extractable As (KH₂PO₄-As), and bioavailable As determined by diffusive gradients in thin films (DGT-As), were measured, along with As concentrations in barley grains (HB-As). Machine learning approaches were employed to construct predictive models for HB-As accumulation, and feature influence mechanisms were interpreted using SHapley Additive exPlanations (SHAP) and Partial Dependence Plot (PDP) analyses. The results showed that: (1) among models constructed using the full feature set, the random forest (RF) model exhibited the best predictive performance for HB-As, with R² values of 0.756 and 0.651 for the training and testing datasets, respectively; (2) SHAP analysis indicated that DGT-As had the greatest contribution to the model (30.5%), followed by T-As and T-Fe/Mn; and (3) significant interaction effects among soil variables jointly influenced HB-As accumulation. This study provides scientific support for agricultural product safety, soil security, and sustainable land use in plateau agroecosystems. Full article

Soil heavy metal (HM) pollution poses a severe threat to ecological security and human health. Selenium (Se) is an essential trace element for the human body and can regulate crop growth and development as well as HM uptake in HM-contaminated soils. The regulatory mechanisms of Se on HMs are mainly reflected in four aspects: Geochemical immobilization promotes the formation of metal selenide precipitates and the adsorption of HMs by soil colloids by regulating the rhizosphere redox potential (Eh) and pH value. Rhizosphere microbial remodeling drives the enrichment of functional microorganisms such as Se redox bacteria, plant growth-promoting rhizobacteria (PGPR), and arbuscular mycorrhizal fungi (AMF) through the dual selective pressure of Se toxicity and root exudates, in order to synergistically realize Se speciation transformation and HM adsorption/chelation. Root barrier reinforcement constructs physical and chemical dual defense barriers by inducing the formation of iron plaques on the root surface, remodeling root morphology and strengthening cell wall components such as lignin and polysaccharides. Intracellular transport regulation down-regulates the genes encoding HM uptake transporters, up-regulates the genes encoding HM efflux proteins, and promotes the synthesis of phytochelatins (PCs) to form HM complexes and lastly realizes vacuolar sequestration. Finally, we summarize current research gaps in the interaction mechanisms of different Se species, precise application strategies, and long-term environmental risk assessment, providing a theoretical basis and technical outlook for the green remediation of HM-contaminated farmlands and Se biofortification of crops. Full article

Polyethylene (PE) mulching has been widely practiced in agriculture for decades, but its short-term impacts on heavy metal dynamics and crop safety under field conditions remain poorly understood. In this study, a one-season field trial was carried out in Cd-contaminated paddy to evaluate how PE mulching influences rhizosphere microbial communities, soil physicochemical properties, and Cd accumulation in rice. Results showed that PE mulching improved rice performance, increasing dry grain weight by 14.47% and thousand-grain weight by 1.10 folds, while reducing grain Cd concentration from 0.2307 to 0.1727 mg/kg, below the national safety threshold of 0.2 mg/kg. These effects were closely linked to elevated soil pH, decreased redox potential, and the enrichment of metal-reducing (Geobacteraceae, Desulfuromonadia) and sulfate-reducing (Desulfosporosinus, Methanospirillum) taxa, which promoted Cd immobilization into less bioavailable forms. A structural equation model (SEM) further confirmed that microbial abundance and Cd speciation were key factors associated with Cd uptake by rice. However, PE mulching also reduced microbial diversity and functional redundancy, disrupted co-occurrence networks, and potentially weakened rhizosphere ecosystem stability and resilience in the short term. This study provides field-based evidence that PE mulching reduces food safety risks and improves yield but destabilizes soil microbial communities, highlighting its short-term double-edged ecological effects and the need for balanced management to sustain productivity and soil health. Full article

The antagonistic geochemical behaviors of cadmium (Cd) and arsenic (As) in co-contaminated soils complicate their simultaneous remediation. This study aimed to develop a synergistic immobilization strategy by converting Spirulina residue into a magnetic biochar-layered double hydroxide composite (FSRBL). The composite was applied to both acidic red and calcareous black soils, and its effects on Cd and As, immobilization efficiency, and ecotoxicity were evaluated. The results showed that FSRBL effectively transforms Cd and As from mobile fractions to stable residual forms. At a 2.5% application rate, FSRBL achieved remarkable immobilization efficiencies of 39.2% for Cd and 57.5% for As, representing effectiveness 3.55 and 5.97 times higher than that of unmodified biochar, respectively. A dose–response relationship between the application amount of FSRBL and the immobilization efficiency of As and Cd was observed and further quantified using a logistic model. The results indicate that while increased FSRBL application enhances immobilization efficiency, the marginal benefit of each additional unit diminishes as the application rate increases, demonstrating a significant diminishing marginal effect. According to the ecotoxicity assessment experiment, the soil leachate from FSRBL-amended soil remarkably decreased the ecological toxicity to rice (Oryza sativa L.). Mechanistic investigations employing SEM/TEM-EDS, XRD, and XPS revealed that the synergistic immobilization could be ascribed to the multi-component cooperation within FSRBL, which resolved the conflicting pH/Eh requirements for the immobilization of Cd and As: (1) the LDH phase efficiently immobilized As oxyanions through anion exchange and isomorphic substitution; (2) the magnetic Fe phase concurrently immobilized Cd²⁺ and As oxyanions via redox transformation and coprecipitation, resulting in the formation of precipitates such as Fe/Ca/Cd–As(V). This work demonstrates a feasible approach to upcycle biomass waste into a value-added material for sustainable remediation of Cd–As co-contaminated soil. Full article

Rice–fishery integrated farming has expanded rapidly in China, yet its implications for arsenic (As) accumulation remain insufficiently understood. This study evaluated As bioavailability and enrichment in a rice–crayfish farming system (RCFS) by establishing controlled field plots with soil As concentrations ranging from 5 to 40 mg/kg under three water-management regimes: alternating wetting and drying (AWD), continuously flooded (CF), and RCFS. Soil–water physicochemical variables and As accumulation in both rice organs and crayfish tissues were systematically analyzed, followed by human health risk assessment. Inorganic As in brown rice increased linearly with soil As, following Y = 0.0117X + 0.0598 (R² = 0.96), and the estimated soil safety thresholds were 26.48 mg/kg for AWD, 11.98 mg/kg for RCFS, and 9.24 mg/kg for CF. AWD consistently exhibited the lowest As risk due to its ability to elevate soil Eh and maintain a more favorable pH, thereby suppressing As mobilization. Compared with CF, RCFS reduced As bioavailability through crayfish-induced bioturbation, which increased Eh, enhanced SOM and CEC, and improved soil aeration. As accumulation in crayfish tissues also rose with soil As, with abdominal muscle As fitting Y = 0.0085X + 0.0553 (R² = 0.8588). Although abdominal muscle met safety limits, the hepatopancreas accumulated substantially higher As and exceeded carcinogenic risk thresholds, even at 5 mg/kg of soil As, indicating a potential health concern for consumers. This work elucidates As dynamics and enrichment mechanisms in RCFS, providing guidance for safer rice–crayfish production in As-impacted areas. Full article

Annually, up to 15 million tons of coffee production waste are produced worldwide. Among them are spent coffee grounds (SCG), which have the potential to be recycled and used as organic fertilizers. However, their direct application to soil is limited due to the presence of ecotoxic compounds (phenols, tannins, and caffeine). Composting is a promising approach; however, the highly variable properties of the raw coffee materials require the selection of optimal production and application modes. In this study, we performed two composting methods for SCG, i.e., vermicomposting and microbial composting, in mixtures with co-composting substrate at five SCG/substrate ratios (0, 25, 50, 75, and 100% SCG). First, the acute toxicity of raw SGC and its mixtures to earthworm Eisenia andrei was evaluated. After 30 days of composting, chemical and microbiological properties, including pH, RedOx potential (Eh), organic carbon (C_org), lignin content, bacteria count, diversity, and potential metabolic activity, were determined in the end products. As composting went on, the pH increased from 5.6–6.2 to 6.0–7.3 and 7.4–7.7 under microbial composting and vermicomposting, respectively. RedOx potential levels achieved 142–166 mV for microbial composting and 73–113 mV for vermicomposting. Organic matter (OM) content reached 86–94%, with an increasing proportion of lignin, demonstrating the decomposition of more readily accessible organic matter. Vermicomposting and microbial composting produced chemically safe and microbiologically highly active composts. An initial SCG content of 25–50% of the compost mixture’s weight yielded the most favorable properties for the resulting compost (high organic matter content and optimal pH levels). Due to the high biological activity of both composting methods, the resultant composts are likely to have a positive effect on plant growth and development and soil health when used as organic nutrient resources. Full article

Floods increasingly threaten semiarid regions, yet their long-term soil ecological impacts remain underdocumented. This study quantifies the hydrologic change and flood-induced soil transformation on the Zhabay River floodplain (Akmola, Kazakhstan) using integrated field, laboratory, and remote sensing data. Gauge records (2012–2024) were analyzed; inundation was mapped from a 0.30 m DEM (Digital Elevation Model) merging SRTM (Shuttle Radar Topography Mission), Landsat 8/Sentinel 2, and UAV (Unmanned Aerial Vehicle) photogrammetry (NDWI (Normalized Difference Water Index) > 0.28) and validated with 54 in situ depths (MAE (Mean Absolute Error) 0.17 m). Soil samples collected before and after floods were analyzed for texture, bulk density, pH, Eh, macronutrients, and heavy metals. Annual maxima increased by 0.08 m yr⁻¹, while extreme floods became more frequent. Thresholds of ≥0.5 m depth and >7 days duration marked compaction onset, whereas >1 m and ≥12 days produced maximum organic carbon loss and Zn/Ni enrichment. The combination of high-resolution DEMs, ROC (Receiver Operating Characteristic) analysis, and soil microbial monitoring provides new operational indicators of soil degradation for Central Asian steppe floodplains. Findings contribute to SDG 13 (Climate Action) and SDG 15 (Life on Land) by linking flood resilience assessment with sustainable land-use planning. Full article

The accumulation of heavy metals in rice (Oryza sativa L.) compromises food safety and endangers public health. Previous studies have postulated that ecological co-cultivation systems can potentially improve soil quality and reduce crop absorption of heavy metals. Herein, three treatment groups, rice mono-culture (CG), low-density rice–frog co-culture (LRF), and high-density rice–frog co-culture (HRF), were employed to evaluate the effects of rice–frog co-culture on the physicochemical properties of soils in reclaimed rice fields and heavy metal accumulation in rice. Notably, the rice–frog co-culture markedly increased levels of soil organic matter (SOM), dissolved organic carbon (DOC), cation exchange capacity (CEC), pH, and redox potential (Eh) (p < 0.05), particularly under high-density conditions, compared to the mono-culture system. These changes significantly reduced the bioavailable fractions of Cd, As, and Hg in the soil and substantially diminished their uptake in the roots, stems, leaves, and grains of rice. Conversely, the co-cultivation systems increased the bioavailable content and plant uptake of Pb, particularly under high-density conditions. These findings highlight the feasibility of the rice–frog co-cropping systems in improving soil conditions and reducing the accumulation of specific toxic metals within rice, thereby enhancing the safety of rice grown in reclaimed fields. However, increased Pb accumulation warrants further investigation. Full article

Examining the changing patterns and underlying mechanisms of soil biomass carbon stocks constitutes a fundamental aspect of soil biology. Despite the potential influence of the sulfur cycle and the life strategies of organisms on community biomass, these factors have rarely been studied in tandem. Biocrusts are model systems for studying soil ecosystems. In this study, metagenomic analysis of biocrusts related to different life strategies from five batches over four consecutive years demonstrated that, in free-living communities, microbial biomass carbon (MBC) synthesis, via assimilatory sulfate reduction (ASR), is primarily coupled with the 3-hydroxypropionate/4-hydroxybutyrate and Calvin–Benson–Bassham cycles. These pathways are affected by the oxidation-reduction potential (Eh), pH, electrical conductivity, and nutrient levels. The decomposition of organic carbon (OC) via dissimilatory sulfate reduction (DSR) was accompanied by the production of dimethyl sulfide (DMS), which was influenced by the C/S ratio and moisture, whereas the synthesis of MBC by symbiotic communities was found to be affected by Eh and pH, and decomposition was affected by the C/S ratio. The MBC stock was influenced by all strategies, with resource strategies having the greatest impacts during the growing season, and the contribution of chemotrophic energy was most significant in free-living communities. In conclusion, the MBC in biocrusts is associated with both ASR and DSR and is facilitated by the A-, S-, and P-strategies under the regulation of the stoichiometric C/S ratio. The exploration of microbial life strategies and sulfur cycling in biocrusts within arid ecosystems in this study offers a new perspective on the patterns of change in soil biomass carbon stocks. Full article

This study represents the first evaluation of the effects of zinc–carbon dot nano-fertilizers (Nano-ZCDs) on the growth of Bok choy (Brassica chinensis L.) and soil health under multi-batch consecutive foliar spraying during three successive cultivation cycles. The results showed that relative to CK, Nano-ZCDs significantly elevated the fresh weight of Bok choy cultivation across three consecutive harvests, by 75.5 ± 1.8%, 75.1 ± 0.2%, and 74.6 ± 0.4%, respectively. Meanwhile, the nutritional value, including amino acids, vitamin C, soluble sugars, proteins, and Zn accumulation, was markedly enhanced by Nano-ZCDs. Additionally, Nano-ZCDs significantly improved soil water content, Eh, soil organic carbon, available potassium, and available phosphorus in the rhizosphere soil. It also enhanced the complexity, stability, and species richness of the bacterial community. Based on the Cornell Soil Health Assessment system, the soil health index of the Nano-ZCDs group was significantly 8.1% higher than that of the CK group. Therefore, multi-batch consecutive applying of Nano-ZCDs promoted Bok choy cultivation growth and improved its quality, without impairing soil health. This study suggests that Nano-ZCDs can be applied in agricultural production processes to promote the sustainable development of agricultural systems. Full article

The regulation of nutrient availability and microbial processes in agroecosystems are strongly mediated by soil physico-chemical factors. Yet, their seasonal dynamics in different crops are not fully understood. This study monitored pH, redox potential (Eh), electrical conductivity (EC), and nitrite (NO₂⁻) in soils grown with clover, maize, and triticale from November to May. Monthly samples were collected in four depth layers (0–20, 20–40, 40–60, 60–80 cm) and analyzed to reveal patterns over time and space. Soil pH remained near neutral, with slight decreases in spring, and it appeared that maize maintained more stable values than clover or triticale. Eh was highest in winter, indicating oxidizing conditions, but decreased in spring, especially at depth under triticale. EC showed moderate variation, with higher surface values under maize. NO₂⁻ was uniformly low in winter but increased in spring, especially in deeper soils with triticale, while clover had lower accumulation. Overall, clover supported greater soil stability, maize increased surface EC, and triticale enhanced nitrite accumulation at depth. These results highlight the need for crop-specific, depth-aware management to maintain soil quality and optimize nitrogen cycling in agricultural systems. Full article

Rice is one of the world’s most consumed foods, and the cereal that most efficiently uptakes and accumulates As, contributing to human health risk. Flooded rice fields alter Eh-pH conditions and, consequently, the proportion of As(III)/As(V), favoring their accumulation in the crop. The use of algae in paddy soils can improve fertility and C-stock and affect chemical conditions and As availability. This study aimed to evaluate the effect of algae application on: As adsorption capacity in paddy soils from Sado, Portugal, changes in pH-Eh conditions in the soil–water environment, and consequent As speciation. Batch-based As adsorption assays were performed with different solid–solution ratios and Chlorella minutissima algae application, and fitted to the Freundlich and Langmuir linear models. In semi-continuous column assays, simulating rice field conditions, the effect of algae on the pH-Eh of soil pore water was evaluated. The soil quality assessment showed pseudo-total contents of As and other elements higher than Portuguese agriculture limits (11 mg As kg⁻¹), but their availability was low, posing no environmental risk. The studied soils had great As adsorption, which increased with algae application (1.07 mg g⁻¹). Algae application favored oxygenation, increasing Eh values, and maintaining As(V) species. This indicated a potential approach to reducing As(III) mobility. Full article

Climate change has intensified extreme weather events and accelerated soil salinization, posing serious threats to crop yield and quality. Salinity stress, now affecting about 20% of irrigated lands, is expected to worsen due to rising temperatures and sea levels. At the same time, the global population is projected to exceed 9 billion by 2050, demanding a 70% increase in food production (UN, 2019; FAO). Agriculture, responsible for 34% of global greenhouse gas emissions, urgently needs sustainable solutions. Microbial inoculants, known as “plant probiotics,” offer a promising eco-friendly alternative by enhancing crop resilience and reducing environmental impact. In this study, we evaluated the plant growth-promoting (PGP) traits and melatonin-producing capacity of Bacillus aerius EH2-5. To assess its efficacy under salt stress, soybean seedlings at the VC stage were inoculated with EH2-5 and subsequently subjected to salinity stress using 150 mM and 100 mM NaCl treatments. Plant growth parameters, the expression levels of salinity-related genes, and the activities of antioxidant enzymes were measured to determine the microbe’s role in promoting plant growth and mitigating salt-induced oxidative stress. Here, our study shows that the melatonin-synthesizing Bacillus aerius EH2-5 (7.48 ng/mL at 24 h after inoculation in Trp spiked LB media) significantly improved host plant (Glycine max L.) growth, biomass, and photosynthesis and reduced oxidative stress during salinity stress conditions than the non-inculcated control. Whole genome sequencing of Bacillus aerius EH2-5 identified key plant growth-promoting and salinity stress-related genes, including znuA, znuB, znuC, and zur (zinc uptake); ptsN, aspA, and nrgB (nitrogen metabolism); and phoH and pstS (phosphate transport). Genes involved in tryptophan biosynthesis and transport, such as trpA, trpB, trpP, and tspO, along with siderophore-related genes yusV, yfhA, and yfiY, were also detected. The presence of multiple stress-responsive genes, including dnaK, dps, treA, cspB, srkA, and copZ, suggests EH2-5′s genomic potential to enhance plant tolerance to salinity and other abiotic stresses. Inoculation with Bacillus aerius EH2-5 significantly enhanced soybean growth and reduced salt-induced damage, as evidenced by increased shoot biomass (29%, 41%), leaf numbers (12% and 13%), and chlorophyll content (40%, 21%) under 100 mM and 150 mM NaCl compared to non-inoculated plants. These results indicate EH2-5′s strong potential as a plant growth-promoting and salinity stress-alleviating rhizobacterium. The EH2-5 symbiosis significantly enhanced a key ABA biosynthesis enzyme-related gene NCED3, dehydration responsive transcription factors DREB2A and NAC29 salinity stresses (100 mM and 150 mM). Moreover, the reduced expression of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) by 16%, 29%, and 24%, respectively, and decreased levels of malondialdehyde (MDA) and hydroxy peroxidase (H₂O₂) by 12% and 23% were observed under 100 mM NaCl compared to non-inoculated plants. This study demonstrated that Bacillus aerius EH2-5, a melatonin-producing strain, not only functions effectively as a biofertilizer but also alleviates plant stress in a manner comparable to the application of exogenous melatonin. These findings highlight the potential of utilizing melatonin-producing microbes as a viable alternative to chemical treatments. Therefore, further research should focus on enhancing the melatonin biosynthetic capacity of EH2-5, improving its colonization efficiency in plants, and developing synergistic microbial consortia (SynComs) with melatonin-producing capabilities. Such efforts will contribute to the development and field application of EH2-5 as a promising plant biostimulant for sustainable agriculture. Full article

Reductive soil disinfestation (RSD) significantly alters soil characteristics, yet its combined effects with bacterial inoculation on subsequent rhizospheric microbial community composition remains poorly understood. To address this knowledge gap, we investigated the effects of RSD and endophytic Brevibacillus laterosporus inoculation on the composition, network, and predicted function of peanut rhizospheric bacteria and fungi. Our results demonstrated that RSD and B. laterosporus inoculation substantially increased rhizospheric bacterial diversity while reducing fungal diversity. Specifically, B. laterosporus-enhanced RSD significantly reshaped the bacterial community, resulting in increased relative abundances of Chloroflexi, Desulfobacterota, and Myxococcota while decreasing those of Firmicutes, Gemmatimonadota, and Acidobacteriota. The fungal community exhibited a more consistent response to RSD and B. laterosporus amendment, with reduced proportions of Ascomycota and Gemmatimonadota but an increase in Chytridiomycota. Network analysis revealed that B. laterosporus inoculation and RSD enhanced the bacterial species complexity and keystone taxa. Furthermore, canonical correspondence analysis indicated strong associations between the soil bacterial community and soil properties, including Eh, EC, NO₃⁻-N, and SOC. Our findings highlight that the shifts in bacterial taxa induced by B. laterosporus inoculation and RSD, particularly the keystone taxa identified in the network, may contribute to the suppression of soil-borne pathogens. Overall, this study provides a novel insight into the shifts in rhizospheric bacterial and fungal communities and their ecological functions after bacteria inoculation and RSD treatment. Full article