Search Results (1,404)

Protected cultivation of pepper in southern China’s red soil region often leads to soil degradation and continuous cropping obstacles. To investigate whether biochar can alleviate these problems by regulating the soil microenvironment, pot and incubation experiments were conducted from 2021 to 2023 with biochar application rates of 0~10% (w/w). The results showed that appropriate biochar application significantly improved pepper yield and soil quality. Under the 6% biochar treatment, pepper yield and dry matter accumulation increased by 89.05% and 36.79%, respectively, compared to the control. Soil bacterial and fungal abundances increased by 346.61% and 107.37%, and their OTU numbers rose by 64.13% and 35.15%, respectively. Biochar application also elevated soil pH, organic matter, available potassium, and total nitrogen contents, improved aggregate stability, and enhanced the activities of urease, catalase, sucrase, and acid phosphatase. Furthermore, biochar altered the rhizosphere microbial community structure and increased bacterial diversity. These findings demonstrate that biochar can promote pepper growth by improving soil physicochemical properties, enzyme activities, and microbial community structure, providing a viable strategy for mitigating continuous cropping obstacles in protected cultivation. Full article

Hydrochar application to soil inevitably releases hydrochar-derived dissolved organic matter (HDOM), yet its specific impact on soil microbial communities, independent of the hydrochar solid matrix, remains poorly understood. This study investigated, for the first time, the dose-dependent effects of HDOM on bacterial communities in three distinct soil types (red, yellow-brown, and black soils). A concentration gradient, including undiluted stock solution and 10-, 100-, and 1000-fold dilutions with ultrapure water, was established to test for hormesis-like responses. High-throughput 16S rRNA gene sequencing revealed that HDOM induced profound, soil-specific shifts in bacterial community structure. The application of HDOM induced the emergence of numerous specific bacterial taxa, with unique ASVs reaching up to 15,372. However, no significant changes were observed in microbial community richness or evenness (alpha diversity). Drastic shifts in beta diversity were evident only in red soil and yellow-brown soil, and exclusively under the undiluted HDOM treatment. At the phylum level, HDOM application did not alter the dominant bacterial types (top 10 phyla); however, their relative abundances were jointly regulated by both HDOM dose and soil type. Significant HDOM-induced changes in key bacterial biomarkers were primarily detected in red soil (e.g., phylum Elusimicrobia, class Fimbriimonadia, and family Alicyclobacillaceae) and yellow-brown soil (e.g., phylum Proteobacteria, class Alphaproteobacteria, and family Rhizobiaceae), while in black soil, such changes were observed only under the undiluted HDOM treatment (e.g., species Streptomyces rochei). Predictive functional profiling suggested limited impact on major metabolic pathways, with soil type remaining the primary determinant. These findings demonstrate that HDOM exerts a direct, dose-dependent, and soil-specific influence on bacterial communities, providing key insights into the environmental behavior of hydrochar and guiding its safe application. Full article

The occurrence and concentration of potentially toxic elements (PTE) in fertilizers are a concern in tropical regions, and soil properties affect their bioavailability for crops. Cadmium is the most easily bioavailable for plants and so the food chain, and it represents a stepping-stone toward safe food production. So, this study aimed to evaluate the ionomics, metabolism, and growth of potato, tobacco, and rice in response to liming and to monoammonium phosphates (MAP) from different geographic origins and PTE contents (MAP 1, MAP 2, MAP 3). For this, independent experiments were conducted with each crop using MAP fertilizers as a phosphorus source applied to a Red-Yellow Latosol, with and without liming. Our findings indicated that physiological changes were primarily influenced by liming rather than PTE. Most acidic soils negatively impacted plant growth and sugar content and induced metabolic adjustments related to proline. The higher level of Cd in MAP 3 reduced manganese and zinc and increased sugar in plant shoots. Rice also had a lower Cd bioaccumulation than potato and tobacco, followed by a higher tolerance to acidic soil. The concentrations of As, Cd, and Cr present in fertilizers did not impair the growth and life cycle of the evaluated plants; however, metabolic adjustments were observed. Full article

The accumulation of highly alkaline red mud poses serious environmental risks due to land occupation and potential soil/groundwater contamination. Recycling red mud as a secondary resource offers an eco-friendly solution, yet its influence on the performance of high-performance mortar (HPM) remains incompletely understood, particularly in aggressive environments. This study aims to systematically evaluate the effects of red mud on the fresh and hardened properties of HPM, including rheological parameters, setting time, mechanical strength, drying shrinkage, and sulfate dry–wet erosion resistance. The novelty lies in (1) quantifying the nonlinear relationships between red mud content and rheological/setting behaviors, (2) revealing the dual effect of red mud with curing age, and (3) using XRD/SEM-EDS to elucidate the micro-mechanisms related to hydration products and elemental changes (Al and Fe). The results show that increasing red mud content reduces slump flow (max 76.03%), plastic viscosity (46.7%), and yield stress (42.3%) while also shortening initial/final setting times (67.91% and 76.18% max reductions). At curing ages below 7 days, flexural and compressive strength increase (up to 64.53% and 33.35%, respectively), following cubic functions; however, at 7 and 28 days, both strength values decrease (max reductions of 13.43% and 12.98%). Red mud increases drying shrinkage and delays sulfate-induced degradation. Microstructural analysis reveals improved compactness of hydration products at early ages but reduced compactness at later ages, accompanied by increased Al/Fe content and enhanced SiO₂/calcium silicate hydrate crystals. These findings provide valuable insights for applying red mud HPM in marine environments. Full article

Intercropping maize with legume cover crops has been shown to increase soil organic carbon (SOC) and alter soil microbial communities, potentially affecting soil aggregate stability. However, whether different legume cover crop varieties vary in their effects on SOC enhancement and aggregate stability improvement, and whether such variation is associated with their capacity to enhance distinct microbial taxa, remains unclear. Here, we conducted a five-year field experiment comprising maize monoculture (MM) and six intercropping systems in which maize was grown with different legume cover crop varieties. We aimed to assess the role of bacterial, non-AMF, and arbuscular mycorrhizal fungal (AMF) community composition in influencing SOC and aggregate stability, measured as mean weight diameter (MWD). On average, the six intercropping systems significantly increased SOC by 28% compared with MM, with no significant differences among legume varieties. However, MWD varied significantly depending on the specific legume used. Specifically, intercropping with red clover or sesbania resulted in MWD values similar to MM, whereas intercropping with soybean, hairy vetch, common vetch, or yellow sweet clover led to significantly higher MWD. Notably, MWD was positively correlated with the proportion of C within macroaggregates (>0.25 mm), and this effect was linked to the enrichment of specific microbial taxa—including the bacterium RB41, the non-AMF Trichoderma, and AMF (unclassified Glomerales, Glomus2, and Glomus3)—in systems with high MWD. These findings indicate that while SOC accrual under intercropping is robust across legume varieties, aggregate stability is contingent upon the identity of the legume and its associated microbiota. Selecting legume varieties with a greater ability to increase the abundance of specific microorganisms that enhance C allocation into macroaggregates can simultaneously improve both SOC accumulation and aggregate stability in maize-based intercropping systems. Full article

The textile industry wastewater contaminated by azo dyes usually contains a certain amount of salinity. Therefore, screening for microorganisms capable of degrading azo dyes in saline environments is of great significance. In this study, the decolorizing activity of azo dye methyl red (MR) by Klebsiella aerogenes WH2 (WH2), newly isolated from soil, was evaluated. WH2 was able to decolorize 92.4% and 86.0% of MR at concentrations of 200 mg/L and 300 mg/L within 24 h, respectively. Given that WH2 exhibited enhanced growth and superior degradation capacity in the presence of 2.5% NaCl compared to salt-free conditions, it can be classified as a slight halophile. Approximately 87.7% of MR was removed by WH2 in the presence of 10.0% NaCl within 24 h. Azoreductase activity assays indicated that WH2 retained higher enzyme activity in the presence of NaCl concentrations not exceeding 7.5%. The degradation products and putative metabolic pathways for MR degradation by WH2 were analyzed using FTIR and LC-MS. Phytotoxicity analysis based on seed germination of Vigna radiata indicated that the degradation products of MR exhibited less toxicity than the parent compound. The high degradation efficiency of MR under high salt concentrations makes WH2 a promising candidate for the treatment of saline textile wastewater. Full article

Phosphogypsum (PG), a major by-product of the phosphate industry, has potential for improving acidic and nutrient-poor red soils, yet its agronomic benefits and heavy metal risks require systematic evaluation. A field experiment was conducted with five treatments, CK (soil only), GT (50% modified phosphogypsum, MPG), TT (40% MPG), ZT (50% phosphorite tailings), and DT (25% MPG + 25% lake sediment), to assess their effects on soil properties, enzyme activities, peanut growth, yield, quality, and heavy metal accumulation. All amendments improved soil structure, moisture retention, nutrient availability, and enzymatic activities. Peanut pod and kernel yields increased under all treatments, with DT achieving the greatest improvements (29.89% and 40.88%, respectively), whereas ZT showed the weakest response (1.91% and 6.26%). DT also achieved the highest soil quality index, and performed best in both yield improvement and root development. Although Cd accumulation increased under DT, heavy metal concentrations in peanut kernels remained below national food safety limits. Overall, DT was identified as the most effective amendment for enhancing red soil fertility and peanut productivity, while long-term monitoring of Cd bioavailability is recommended to ensure sustainable and safe application. Full article

Continuous monocropping and inappropriate fertilization have contributed to nutrient depletion and soil degradation, limiting peanut productivity in subtropical red soil agroecosystems. Although diversified cropping may help alleviate these constraints, the reasons why it improves peanut productivity remain unclear. In this study, we conducted a long-term field experiment in Jiangxi, China, to compare four cropping systems, assess soil nutrients, peanut productivity, and bacterial communities, and further evaluate the role of key taxa through inoculation assays and structural equation modeling. Results showed that diversified cropping improved peanut growth and yield, with the green manure integrated system performing best overall. Diversified cropping also increased soil organic carbon, total nitrogen, and available phosphorus, while reshaping bacterial communities. Several taxa, including Bradyrhizobium, Mycobacterium, Dormibacter, and Ardenticatena, were positively associated with soil nutrients. Inoculation assays further showed that a synthetic consortium assembled from representative strains affiliated with key taxa produced stronger effects on plant growth than a single-strain inoculation. Structural equation modeling identified key taxa as the factor most strongly associated with crop productivity. These findings suggest that higher peanut productivity under diversified cropping was closely associated with concurrent improvements in soil fertility and the enrichment of key taxa. Full article

Accurate estimation of forest soil organic carbon (SOC) is considered critical for understanding terrestrial carbon cycling and supporting climate change mitigation strategies. However, the canopy block, intricate vertical structure of forests, and the constraints of single-source remote sensing data have presented considerable obstacles for estimating forest SOC. This study proposes a forest SOC estimation and uncertainty analysis (ForSOC-UA) framework to enhance forest SOC estimation and quantify its uncertainty in the natural secondary forests of northern China by integrating hyperspectral imagery (ZY-1F), synthetic aperture radar data (Sentinel-1), and environmental covariates (such as topography, vegetation, and soil indices). The performance of traditional machine learning models (RF, SVM, and CNN), geographically weighted regression (GWR), and a geographically weighted random forest (GWRF) model was compared across three different soil depths (0–5 cm, 5–10 cm, and 10–30 cm). The results showed that GWRF consistently outperformed all other models across all soil depth layers, with the highest accuracy achieved using multi-source data (R² = 0.58, RMSE = 27.49 g/kg, rRMSE = 0.31). Analysis of feature importance revealed that soil moisture, terrain characteristics, and Sentinel-1 polarization attributes were the primary predictors, while spectral derivatives in the red and near-infrared bands from ZY-1F also played a significant role for forest SOC estimation. The uncertainty analysis indicated a forest SOC estimation uncertainty of 37.2 g/kg in the 0–5 cm soil layer, with a decreasing trend as depth increased. This pattern is associated with the vertical spatial distribution of the measured forest SOC. This integrated approach effectively captures spatial heterogeneity and nonlinear relationships between feature and forest SOC, while also assessing estimation uncertainty, so providing a robust methodology for predicting forest SOC. The ForSOC-UA framework addresses the uncertainty quantification of SOC estimation at different vertical depths based on machine learning, providing methodological enhancements for the assessment of large-scale forest SOC and the monitoring of carbon sinks within forest ecosystems. Full article

Conventional cement-based foamed lightweight soil (FLS) faces cost and environmental challenges. This study develops a sustainable polyvinyl alcohol (PVA) fiber-reinforced solid waste-based FLS (PVA-SWFLS) by entirely replacing cement with a ternary system of red mud, granulated blast furnace slag, and fly ash. PVA fibers were incorporated to mitigate inherent brittleness and cracking. The effects of fiber content (0–0.9 vol%), length (3–15 mm), water–binder ratio (0.35–0.55), and wet density (550–950 kg/m³) on the fluidity and compressive strength were evaluated, along with analyses of microstructure and pore characteristics using scanning electron microscopy and mercury intrusion porosimetry. Findings reveal that fiber addition reduces flowability (up to 34.9%) but significantly bolsters compressive strength, depending on fiber content and length. For 0.3% and 0.5% contents, optimal fiber lengths of 12 mm and 9 mm were observed, respectively; the 28-day compressive strength reached a maximum of 2.97 MPa at the 0.3% content with 12 mm fibers. Beyond these optimal points, and particularly for higher contents (0.7–0.9%), strength decreased monotonically with increasing fiber length due to fiber agglomeration and reduced compactness. Furthermore, strength correlated positively with wet density and negatively with the water–binder ratio, while fluidity increased with both. The hierarchy of influence was identified as: fiber content > fiber length, and wet density > water–binder ratio, while all four parameters significantly governed fluidity. The stress–strain behavior under different parameter combinations was analyzed, and a parametric constitutive model was established to support practical applications. Full article

The forest understory litter fraction $\left({\mathrm{F}\mathrm{V}\mathrm{C}}_{\mathrm{y}}\right)$ is a critical indicator for evaluating the effectiveness of “understory erosion” control in red soil regions; however, its high-precision, large-scale monitoring remains challenging due to canopy occlusion. This study proposes an ${\mathrm{F}\mathrm{V}\mathrm{C}}_{\mathrm{y}}$ inversion framework that integrates high-spatial-resolution Sentinel-2 imagery with multi-angular prior knowledge from MODIS BRDF products. First, a linear mapping model between multi-band reflectances at 0° and 45° view angles was constructed using 500 m MODIS MCD43A1 products $(R^2>0.8)$. This model was subsequently employed as a physical prior for anisotropic characterization and transferred to 10 m Sentinel-2 imagery to generate a long-term, dual-angle reflectance dataset. Subsequently, the four-scale geometric-optical model was utilized to decouple canopy and understory background signals, followed by quantitative ${\mathrm{F}\mathrm{V}\mathrm{C}}_{\mathrm{y}}$ inversion using a pixel-based dimidiate model. Validation results confirmed the reliability of the framework $(R^2=0.74, RMSE=0.1073)$. Spatiotemporal evolution analysis indicated a significant upward trend in ${\mathrm{F}\mathrm{V}\mathrm{C}}_{\mathrm{y}}$ across Changting County from 2016 to 2025, with over 90% of the area showing improvement. The proportion of high-coverage areas $({\mathrm{F}\mathrm{V}\mathrm{C}}_{\mathrm{y}}>0.75)$ increased from 10% to 38%, exhibiting a “high in the center, low in the periphery” spatial pattern that aligns closely with core ecological restoration zones. Stability and persistence analyses further revealed that 61.18% of the study area reached moderate-to-high stability, and 70% of pixels exhibited a “positive persistence-improvement” trend, highlighting a pronounced inertia-driven enhancement in ecological recovery. This study provides a refined technical pathway for assessing soil and water conservation benefits in red soil regions. Full article

Aims: This study aimed to evaluate how the combined application of slow-release nitrogen fertilizer and urea influences nitrogen losses via runoff and the yield performance of silage maize in red soil sloping cropland, in order to support region-specific strategies for soil and water conservation and efficient nitrogen management in maize-based systems. Methods: A one-year field runoff plot experiment was conducted under natural rainfall conditions. Three fertilization treatments with equal nitrogen input were established: conventional urea application (CK), 25% controlled-release nitrogen fertilizer combined with 75% urea (P1), and 50% controlled-release nitrogen fertilizer combined with 50% urea (P2). Results: (1) Co-application of slow-release fertilizer and urea significantly improved soil and water conservation compared to CK; total runoff was reduced by 9.17% and 8.29% under P1 and P2, respectively; and soil loss was reduced by 16.45% and 12.25%. (2) The co-application of slow-release fertilizer effectively reduced nitrogen losses from sloping farmland. Compared to CK, both P1 and P2 reduced losses of total nitrogen (TN), nitrate nitrogen (NO₃⁻-N), and ammonium nitrogen (NH₄⁺-N) during the maize growth period, with the reductions under P2 being most pronounced. (3) The co-application of slow-release fertilizer and urea enhanced maize nitrogen uptake and increased maize yield. Conclusions: Based on the results of this single-year field experiment, the combined application of controlled-release nitrogen fertilizer and urea showed potential advantages in reducing runoff-related nitrogen losses while improving crop productivity in red-soil sloping cropland. Among the treatments, P2 (50% controlled-release nitrogen substitution) exhibited relatively better overall performance. However, the broader applicability of these findings requires further verification through multi-year field experiments under different climatic conditions. Full article

Perennial groundcover (PGC) systems integrate perennial grasses with annual crops such as corn (Zea mays L.) to provide continuous soil cover and enhance soil health. However, the proximity to groundcover vegetation can alter light quality perceived by developing seedlings, inducing shade avoidance response (SAR), a phytochrome-mediated developmental response that modifies plant architecture and may compromise yield. Identifying the distance at which SAR is initiated and the extent to which management practices modulate this response is critical for optimizing PGC systems. This growth chamber study aimed to (1) identify the distance at which SAR occurs in corn seedlings, (2) determine whether the thiamethoxam seed treatment mitigates SAR expression, and (3) compare hybrid physiological responses to PGC-induced SAR. The experiment was arranged in a randomized complete block design with four replications across three periods and included two corn hybrids (P1185, P1197), two seed treatments (untreated and thiamethoxam at 0.25 mg seed⁻¹), and four perennial ryegrass (Lolium perenne L.) distances [0, 6, 25 cm, and a control (no-grass)]. Reduced red to far-red light ratios associated with closer proximity to ryegrass induced SAR responses. Corn plants at 6 cm from PGC exhibited significant stem and height elongation beginning at 8 days after planting (DAP), followed by reduced growth by 14 DAP, confirming an early SAR response. Plants grown at 0 cm exhibited reduced height and growth compared to other distances at all growth stages. Hybrid responses differed, and Hybrid P1197 showed enhanced stem elongation, a characteristic SAR response. The thiamethoxam seed treatment did not mitigate SAR. These results indicate that SAR causes stem elongation without altering root or shoot biomass. Full article

With the large-scale cultivation of transgenic Bacillus thuringiensis (Bt) crops, the Bt toxin released from Bt crops is continuously introduced into the soil. Its environmental fate represents a key indicator for assessing the ecological safety of transgenic crops. However, the persistence of Bt toxin in soil is influenced by both biotic and abiotic processes, and their respective contributions under natural conditions remain unclear. This study measured water-dissolved Bt toxin concentrations in paddy soil (PS) and red soil (RS) to compare the influence of biotic and abiotic factors on the dynamic retention of exogenous Bt toxin under different sterilization methods: no sterilization, heat sterilization (HT), and irradiation sterilization (IS). The water-dissolved Bt toxin exhibited a dynamic decrease–increase–decrease trend across all three treatments in both soil types during the 30 day experimental period. Bt toxin displayed rapid adsorption during the initial 2 h stage in RS, but subsequently showed a high desorption, whereas PS probably achieved more stable bonding through soil organic matter (SOM). Different sterilization methods significantly influenced the results by altering abiotic factors: Compared to CK, HT affected soil physicochemical properties and enhanced adsorption resilience, whereas IS caused minimal impact on the soil physicochemical properties, thereby providing a more accurate reflection of abiotic processes. And microbial, as biotic facters, also influence the reduction process of Bt toxin by participating in the adsorption–desorption–degradation equilibrium process. Therefore, we infer that over time, the concentration of water-soluble Bt proteins in the soil will tend toward zero. Additionally, the initial Bt toxin concentration influenced dynamic balance by adjusting adsorption site saturability, with more pronounced desorption reversibility at 500 ng/g concentrations. Overall, this study systematically reveals the effects of soil properties, microorganisms, and sterilization methods on Bt toxin persistence. The findings underscore the importance of selecting and justifying sterilization methods in related environmental behavior studies, while providing essential guidance for the scientific assessment of environmental risks posed by transgenic crops. Full article

Canopy fractional vegetation cover (FVCc) is a critical indicator for evaluating the effectiveness of ecological restoration, and its accurate estimation provides valuable data for regional ecological management. In this study, Sentinel-2 and MODIS data were integrated to develop an angular relationship model for MODIS reflectance, which was then used to estimate Sentinel-2 reflectance at a 45° viewing angle. Background reflectance at a 10 m spatial resolution was derived using a four-scale model, and total and shrub-herb fractional vegetation cover were estimated using a pixel dichotomy model. Finally, an empirical model tailored to the characteristics of the study area was developed to retrieve FVCc. Cross-validation results demonstrated that the multi-angle retrieval method proposed in this study achieved higher accuracy than the single-angle approach. The spatial distribution of FVCc in Changting County is characterized by higher values in peripheral areas and lower values in the central region. Temporal transitions among fractional vegetation cover classes were predominantly upward, indicating an overall trend of continuous improvement. These findings provide important technical support and a scientific basis for estimating and monitoring dynamic changes in forest canopy fractional vegetation cover. Full article