Search Results (25,220)

The terminal tributaries of karst rivers are often under-researched, with low investigation coverage and incomplete surveys. These areas face significant human activity disturbances, fragile soil and water environments, and insufficient research on water quality conditions. Residents in their basins are confronted with urgent issues of water scarcity and deteriorating water quality. This study focused on the Zhongdu River Basin, a terminal tributary in the Pearl River system in Southwest China. By measuring the conventional hydrochemical parameters and stable isotope ratios (e.g., δ¹⁸O and δ²H), this study employed methods such as hydrological and geochemical approaches, as well as classical statistical analyses, to reveal the hydrochemical characteristics, regulatory mechanisms, and water health status in the basin. Data show that the water in the Zhongdu River Basin is generally weakly alkaline, with a pH range between 6.46 and 8.28. The highest values for electrical conductivity (EC) and total dissolved solids (TDSs) are found upstream, reaching 497 μS/cm and 324.5 mg/L, respectively. The average dissolved oxygen (DO) value is 71.3 mg/L. The hydrochemical type is primarily HCO₃⁻-Ca²⁺, with Ca²⁺ and HCO₃⁻ as the dominant ions. The surface water in the middle and lower reaches of the basin is strongly influenced by evaporation, with atmospheric precipitation as the main recharge source. Rock weathering is the primary influencing factor in the basin, with most minerals in a dissolved state. Agricultural activities are the primary pollution source in the basin, with domestic pollution having a minimal effect on water quality. Water quality was assessed using the entropy-weighted water quality index (EWQI) based on 11 parameters, indicating overall good water quality, classified as Grade I. The findings indicate that human activities have a minimal impact on the water quality in the region, and the basin is expected to maintain its healthy condition for an extended period. Full article

Net ecosystem productivity (NEP) is a crucial metric for quantifying carbon storage, exchange, and cycling across global atmospheric and terrestrial ecosystems. This study examines the spatiotemporal patterns of NEP in China’s Zoigê alpine grassland and its response to climate variability, phenological changes, and soil conditions from 2000 to 2020. The results show a statistically significant increase in the annual NEP of the Zoigê Plateau, with an average rate of 3.18 g C/m²/year. Spatially, NEP displays strong heterogeneity, with higher values in the southwestern and northeastern marginal areas (>80 g C/m²) and lower values in the central region (<0 g C/m²). In alpine meadows (standardized total effect coefficient [STEC] = 0.52) and alpine steppes (STEC = 0.43), NEP is primarily regulated by soil moisture modulation, influenced by both water and temperature factors. This study accurately assesses NEP by incorporating regional soil characteristics, providing a more precise evaluation of changes in vegetation carbon sink sources in high-altitude areas. Full article

Black soils refer to soils with black, thick upper layers containing 0.6% or more soil organic carbon in the tropical region. This high organic carbon content makes these soils essential for climate change control and food production. In Indonesia, black soils are found under forests, shrublands, and grasslands in tropical monsoon and savannah climates. Land clearing for agricultural uses will change black soil properties; however, knowledge of change (level, direction, and sensitivity) is limited. Meanwhile, soil surveying records land-use types and collects soil samples, resulting in voluminous legacy soil data. This study aimed to compare the mean difference in soil properties between two land-cover/use types. We used 142 black soil datasets containing legacy data on particle size distribution (sand, silt, clay), pH, soil organic carbon (SOC), total nitrogen (TN), available P₂O₅ (AP), and exchangeable cations (Ca, Mg, K, Na). We calculated the Hedges’s g-index for effect size assessment and performed a Welch’s t-test for significant differences. The results show that, compared to the forest, the agricultural dryland and monoculture home gardens have a large effect size and trigger changes in many soil properties. In contrast, mixed home gardens and paddy fields have a small effect size. In decreasing order, the black soil properties sensitive to change are TN > SOC = exchangeable K > exchangeable Mg = available phosphorus = pH = exchangeable Na > sand = silt = clay > exchangeable Ca. The results suggest that a combination of home gardens and paddy fields better supports food security and mitigates climate change in black soils. In addition, the legacy soil data can be used to monitor soil property changes. Full article

Agricultural activities such as fertilization and cultivation constitute a substantial source of non-point source (NPS) nitrogen (N) in aquatic ecosystems. Precise quantification of fluxes across diverse land uses and identification of critical source areas are essential for effectively mitigating nitrogen loads. In this study, the Soil Water Assessment Tool (SWAT) was employed to accurately model the watershed hydrology and total nitrogen (TN) transport in the Zhongtian River Basin, i.e., an agricultural watershed characterized by low mountainous terrain. The simulation results indicated that the average TN load intensity within the watershed was 21.34 kg ha⁻¹ yr⁻¹, and that TN load intensities for paddy fields and tea plantation were 34.96 and 33.04 kg ha⁻¹ yr⁻¹, respectively. Agricultural land, which covered 32.06% of the area, disproportionately contributed 52.88% of the N output in the watershed. Pearson and redundancy analysis (RDA) underscored land use as the primary driver of nitrogen emissions, with a contribution exceeding 50%. Building on a high-precision simulation analysis, a suite of best management practices (BMPs) was established. These findings highlight the superior performance of engineered BMPs over agricultural BMPs, with TN load reduction rates of 12.23 and 27.07% for filter strips and grassed waterways, respectively. Among three agricultural BMPs, the effect of fertilizer reduction was the most pronounced, achieving reductions of 6.44% for TN and 21.26% for nitrate. These results suggest that optimizing fertilizer management and implementing engineered BMPs could significantly reduce nitrogen pollution in agricultural watersheds, providing valuable insights for sustainable agricultural practices and water quality management. Full article

Accurate soil moisture (SM) estimates with high spatial resolution are highly desirable for agricultural, hydrological, and environmental applications. This study developed a two-step reconstruction approach to obtain a high-quality and high-spatial-resolution (0.05°) SM dataset from microwave and model-based SM products, combining Bayesian three-cornered hat (BTCH) merging and machine/deep learning downscaling algorithms. Firstly, a three-cornered hat (TCH) method was used to analyze the uncertainty of seven SM products on four main land cover types in the Pearl River Basin (PRB). On this basis, the SM products with low uncertainty were merged using the BTCH method. Secondly, two machine/deep learning algorithms (random forest, RF, and long short-term memory, LSTM) were applied to downscale the merged SM data from 0.25° to 0.05° based on the relationship between SM and auxiliary variables. The overall performance of RF and LSTM downscaling models with/without antecedent precipitation were compared. The merged and downscaled SM results were validated against in situ observations and the China Meteorological Administration (CMA) Land Data Assimilation System (CLDAS) SM data. The results indicated the following: (1) The BTCH-based SM estimate outperformed the parent products and the AVE-based SM estimate (the arithmetic average), indicating that BTCH is a fusion approach that can effectively reduce data uncertainties and optimize weights. (2) The optimal time scale for the cumulative effect of precipitation on SM was 35 days during 2015–2020 in the PRB. SM estimations using RF and LSTM downscaling algorithms both had substantial improvement by considering the antecedent precipitation variable, both at the 0.25° and 0.05° spatial scales. Feature importance assessment also revealed the most important role of antecedent precipitation (30.01%). Moreover, the LSTM model with antecedent precipitation performed slightly better than the RF model with antecedent precipitation. (3) The downscaled SM results all mitigated the overestimation inherent in the original SM data, though they were inevitably limited by the performance of the original SM data and difficult to surpass. The developed two-step reconstruction approach was effective in generating an accurate SM dataset at a finer spatial scale for wide regional applications. Full article

A reduction in emissions of nitrous oxide (N₂O), one of the three major greenhouse gases, is important for achieving environmental sustainability and carbon neutrality goals. Agricultural fields are the primary source of N₂O emissions, and their management measures influence greenhouse gas emission reductions and the greening of agriculture. Among these practices, cover cropping plays a key role in promoting sustainable agricultural production as a major cropping technique for efficient water use and increasing crop yields in water-scarce regions worldwide. The present paper systematically reviews the influence of various soil environmental factors, such as soil temperature, moisture, pH, carbon, and nitrogen contents, as well as nitrogen cycle-related enzymes, microorganisms and mulching practices, including general mulching and straw mulching, on N₂O emissions from agricultural fields. This review suggests that future research should explore the long-term effects of different mulching materials and their application rates and durations on soil N₂O emissions. Furthermore, a networked mathematical model for causal analysis should be employed in future research to elucidate the relationships among soil environmental factors, nitrogen cycle microorganisms, and soil N₂O production and consumption. These future studies will help to deepen our understanding of nitrogen cycling processes in agroecosystems with the aim of developing environmentally friendly agricultural technologies and promoting green and sustainable agricultural development. Full article

Nitrogen, an essential element for plant growth and food production, presents significant challenges in agriculture due to the environmental consequences of synthetic nitrogen fertilizers. This review explores the potential of nitrogen-fixing cyanobacteria as a sustainable alternative for agricultural nitrogen fertilization. The molecular mechanisms underlying nitrogen fixation in cyanobacteria, including key genes such as nif and related biochemical pathways, are examined in detail. Biotechnological approaches for utilizing nitrogen-fixing cyanobacteria as biofertilizers are discussed, alongside strategies for genetic engineering to improve nitrogen fixation efficiency. The review further evaluates the impact of cyanobacteria on soil health and environmental sustainability, emphasizing their role in mitigating the detrimental effects of synthetic fertilizers. While promising, challenges such as oxygen sensitivity during nitrogen fixation and competition with native microorganisms are critically analyzed. Finally, future directions are proposed, including advancements in synthetic biology, integration with conventional agricultural practices, and scalable implementation strategies. This review underscores the transformative potential of nitrogen-fixing cyanobacteria in promoting sustainable agriculture and enhancing global food security. Full article

The Sanjiangyuan region, known as the “Chinese Water Tower”, serves as a crucial ecological zone that is highly sensitive to climate change. In recent years, rising temperatures and increased precipitation have led to permafrost melt and frequent occurrences of thermokarst landslides, exacerbating soil erosion issues. Although studies have explored the impact of freeze–thaw action (FTA) on soil properties, research on this phenomenon within the unique geomorphological unit of thermokarst landslides, formed from degrading permafrost, remains sparse. This study, set against the backdrop of temperature-induced soil landslides, combines field investigations and controlled laboratory experiments on typical thermokarst landslide bodies within the permafrost region of Sanjiangyuan to systematically investigate the effects of FTA on the properties of soils within thermokarst landslides. Furthermore, this study employs the EPIC model to establish an empirical formula for the soil erodibility (SE) factor before and after freeze–thaw cycles (FTCs). The results indicate that: (1) FTCs significantly alter soil particle composition, reducing the content of clay particles in the surface soil while increasing the content of sand particles and the median particle size, thus compromising soil structure and enhancing erodibility. (2) FTA initially significantly increases soil organic matter content (OMC); however, as the number of FTCs increases, the magnitude of these changes diminishes. The initial moisture content of the soil significantly influences the effects of FTA, with more pronounced changes in particle composition and OMC in soils with higher moisture content. (3) With an increasing number of FTCs, the SE K-value first significantly increases and then tends to stabilize, showing significant differences across the cycles (1 to 15) (p < 0.05). This study reveals that FTCs, by altering the physicochemical properties of the soil, significantly increase SE, providing a scientific basis for soil erosion control and ecological environmental protection in the Sanjiangyuan area. Full article

The growing demand for sustainable agricultural practices requires the search for innovative solutions to improve crop yield and quality. This study investigated the soil-specific effects of the bio-growth regulator Supporter on seed potato yield and quality in different potato varieties, with the aim of unlocking its sustainable potential under different environmental conditions. Field trials were conducted on several soil types using the bio-growth stimulator Supporter at a rate of 300 mL per hectare. Standardized agronomic practices, including continuous fertilization, weed control, and pest control, were applied at all test sites to ensure comparability. The results showed that the use of the bio-growth stimulator Supporter significantly increased tuber yield and quality, especially in soils with moderate fertility levels. In the treatments, with the Supporter biostimulator, there was better tuber size uniformity and a higher fraction and number of seed potato. A higher average seed potato mass and higher multiplication coefficient were observed. The effectiveness of the Supporter varied across study locations and soil types, with sandy and sandy loam soils showing the most pronounced benefits, while clay soils showed more limited responses. The results underscore the potential of the Supporter as a sustainable tool for increasing potato seed production, while also emphasizing the need for soil-specific recommendations. This study highlights the importance of integrating growth regulators into precision agriculture to optimize crop performance and support global food security goals. Therefore, further research is needed on the use of biostimulants, which will allow us to understand the purpose of their action, which is important in agricultural practice. Full article

Geotechnical field testing evaluates soil, rock, and groundwater conditions in their natural states, offering critical information about subsurface properties such as the density, strength, permeability, and groundwater flow. These tests are essential in ensuring the safety, reliability, and performance of civil engineering projects and are increasingly used for 3D geographical visualization and subsurface modeling. While point-based tests like the cone penetration test (CPT) and standard penetration test (SPT) are widely used, area-based methods such as the spectral analysis of surface waves (SASW) and electrical resistivity testing significantly enhance the accuracy of such models by providing broader coverage. Furthermore, these non-destructive techniques are particularly effective in identifying subsurface defects. This study focuses on analyzing the data acquisition areas of various field seismic tests, including SASW, downhole, crosshole, and suspension logging (PS logging). While other tests clearly define data acquisition areas based on their array paths, the SASW test posed challenges due to the complexity of data reconstruction. To address this, 69 datasets from four different sites were analyzed to predict the data acquisition areas for SASW as a function of depth. Moreover, a case study demonstrates the practical application of the SASW method in detecting cavities near a dam spillway. The findings of this research improve the understanding and interpretation of geotechnical seismic test data, enabling more precise geotechnical investigations and advancing the detection of subsurface defects using non-destructive methods. Full article

Soil health is typically evaluated using physical, chemical, and biological parameters. However, identifying cost-effective and interpretable metrics remains a challenge. The effectiveness of ecological outcome verification (EOV) in predicting soil health in grazing lands was assessed at 22 ranches. Sixty-four soil samples were analyzed using the Haney soil health test (HSHT) and phospholipid fatty acid (PLFA). Of 104 variables, 13 were retained following principal component analysis (PCA), including variables associated with plant community, carbon dynamics, and microbial community structure. Soils with enriched microbial and organic matter (SOM) characteristics supported a healthier ecological status, as corroborated by greater EOV scores. Water-extractable organic carbon (WEOC) was positively correlated to plant functional groups, whereas SOM was positively correlated with plant biodiversity and functional groups. Total bacteria were positively correlated with all EOV parameters. Microbial biomass (MB) was positively correlated with both water and energy cycle indexes, whereas arbuscular mycorrhizal fungi (AMF) was positively correlated with the water cycle. From the multiple regression analyses, water infiltration emerged as a key predictor of soil respiration and WEOC. Overall, the ecological outcomes measured by EOV have the potential to serve as a proxy for soil health, providing a practical tool for producers to make informed land management decisions. Full article

Coordinating the spatial distribution of crop roots with soil nutrients, along with selecting appropriate types of fertilizers, is an effective strategy to enhance root nutrient absorption and increase crop yield. In Xinjiang’s current surface drip irrigation practices for rice (Oryza sativa L.), premature leaf senescence and N deficiency are common issues, resulting in decreased yields. This study investigated whether different N forms under subsurface drip irrigation can modulate rice root morphological strategies to delay senescence in later growth stages, enhancing rice N uptake and yield formation. A field experiment compared the effects of different drip irrigation positions (surface drip irrigation at the surface, DI0; subsurface drip irrigation at 10 cm depth, DI10) and N forms (urea N, UN; ammonium N, AN) in four combination treatments (DI0-UN, DI0-AN, DI10-UN, DI10-AN) on rice root morphology, aboveground growth, and yield formation. During the grain-filling stage, the total root length (RL) and root number (RN) in the DI10-AN treatment were higher than in other treatments. Root vitality increased by 23.24–133.72% during the later filling stages, while the root decline rate decreased by 1.16–32.80%. The root configuration parameters β in the DI10-AN treatment were superior to those in other treatments, indicating that roots tend to distribute deeper in the soil. The DI10-AN treatment reduced Malondialdehyde (MDA) levels and increased Superoxide Dismutase (SOD) activity, thereby alleviating water and N stress on the leaves in later growth stages and maintaining higher photosynthetic parameter values. The DI10-AN treatment significantly increased N absorption (14.37–52.88%) and yield (13.32–46.31%). Correlation analysis showed that RL, RN, and root activity (Ra) were significantly positively correlated with transpiration rate (Tr), intercellular CO₂ concentration (Ci), N uptake (NUP), one thousand-kernel weight (TKW), seed setting rate (SR), Efficient panicle (EP), and yield (r > 0.90). This study presents a new rice drip fertigation technique that combines subsurface irrigation with ammonium to enhance root growth and increase crop productivity. Full article

The change in bound water content with temperature is a core issue in studying temperature effects in clayey soils. This study used nuclear magnetic resonance (NMR) techniques to measure pore water in three types of marine clay, ranging from inland to coastal areas. The T₂ cutoff values were proposed to distinguish between bulk water, capillary water, and bound water, and the curves of unfrozen water and bound water content with changing temperatures were obtained during the freezing process. Additionally, the impact of soil properties on bound water content was analyzed. The research findings indicated that the pore water in marine clay is dominated by bound water, and the change in bound water content with temperature in each soil layer can be divided into four stages: the trace phase change stage, the intense phase change stage, the transitional phase change stage, and the stabilizing stage. Further, the effect of soil properties such as organic matter content, soluble salt content, and cation exchange capacity on bound water content was illustrated, and clay content and bound water content were found not to be strictly positively correlated. Full article

The use of nitrification inhibitors (NIs) with nitrogen fertilizers represents an effective strategy to reduce nitrogen loss. In addition, nitrification inhibitors are widely applied to improve agricultural yield. However, it is necessary to continue investigating the crop-specific agricultural practice. In this study, a nitrapyrin-based nitrification inhibitor was used to assess its effects on Brassica oleracea L. var. botrytis growth and on the environment. In a pot experiment, cauliflower plants were grown in fertilized soils based on calcium nitrate (SF) and SF + nitrapyrin. At the end of the experiment, the content of nitrogen compounds in soil and percolation water and the cauliflower yield were determined, and the plant tissues were characterized by Fourier-transform infrared spectroscopy. The application of the NI significantly reduced nitrogen losses, increasing nutrient availability in the soil and the element’s absorption in the plant. Co-application of fertilizers and NIs reduced ${NO}_3^{-}$ leaching from 925 to 294 mg/L. Plant tissue characterization by FTIR spectroscopy highlighted variations in the functional groups in response to the application of NIs. These results suggest that applying nitrogen fertilizer in combination with nitrapyrin can mitigate nitrate pollution and improve element absorption and plant growth. Our research has shown that application methods and cropping systems need to be studied to maximize the effectiveness of nitrapyrin-based NIs. Full article

Efficient monitoring of soil inorganic nitrogen is crucial for precision agriculture fertilization and ecological environmental protection. Traditional detection methods are complex and challenging for real-time in situ measurements. This study proposes an innovative approach based on dielectric response characteristics, enabling non-destructive and rapid detection by analyzing soil polarization behavior in an electromagnetic field. Using a vector network analyzer (E5071-C), we systematically measured the complex dielectric spectra of red soil and yellow clay loam across a wide frequency range from 10 MHz to 4.5 GHz. Coupled with water–nitrogen interaction experiments (volume water content: 0.05–0.25 cm³/cm³; nitrogen concentration: 0–0.2 mol/L), we established a high-frequency–low-frequency collaborative detection model. The study found that at the 3.8 GHz high-frequency band, the interface polarization weakening effect allows for the precise measurement of soil water content (R² = 0.82; RMSE = 0.030 cm³/cm³). In the 100–200 MHz low-frequency band, based on ion migration dynamics, we successfully identified characteristic sensitive frequency bands for NH₄⁺ (136–159 MHz) and NO₃⁻ (97–129 MHz). Notably, at 127 MHz, the water–nitrogen coupling model predicted inorganic nitrogen content with a determination coefficient of 0.721. This method effectively overcomes the water interference issue inherent in traditional single-frequency dielectric methods through a dual-frequency decoupling mechanism. The findings lay a theoretical foundation for developing in situ sensors for farmland. Real-time monitoring can significantly improve nitrogen fertilizer utilization efficiency and reduce environmental pollution, offering substantial application value for advancing precision agriculture and sustainable development. Full article