Search Results (723)

Soil organic matter (SOM) is a key indicator of cropland quality and carbon cycling. Accurate SOM mapping is essential for sustainable soil management and carbon sink assessment. This study investigated the effects of interannual climatic variability on SOM prediction using remote sensing and machine learning. Youyi Farm in the Sanjiang Plain, Heilongjiang Province, was selected as the study area, covering three representative years: 2019 (flood), 2020 (normal), and 2021 (drought). Based on multi-temporal Sentinel-2 imagery and environmental covariates, Random Forest models were used to evaluate single- and dual-period combinations. Results showed that combining bare-soil and crop-season images consistently improved accuracy, with optimal combinations varying by year (R² = 0.544–0.609). Incorporating temperature, precipitation, and elevation enhanced model performance, particularly temperature, which contributed most to prediction accuracy. Feature selection further improved model stability and generalization. Spatially, SOM showed a pattern of higher values in the northeast and lower in the central region, shaped by topography and cultivation. This study innovatively integrates interannual climatic variability with remote sensing temporal combination and feature selection, constructing a climate-adaptive SOM mapping framework and providing new insights for accurate inversion of cropland SOM under extreme climates, highlights the importance of multi-temporal imagery, environmental factors, and feature selection for robust SOM mapping under different climatic conditions, providing technical support for long-term cropland quality monitoring. Full article

The fusion of Raman and visible–near-infrared (VIS–NIR) spectroscopy provides a promising pathway for rapid and non-destructive soil analysis. However, conventional fusion strategies often fail to properly balance modality discrepancies and complementary information. To address this limitation, this study develops an adaptive Gated Ridge Regression fusion model (Fusion_GatedRidge) for predicting soil organic matter (SOM). A total of 246 soil samples collected from a dryland agricultural region in Shanxi Province were analyzed using laboratory Raman and VIS–NIR spectroscopy. After standard preprocessing, three baseline fusion frameworks—EarlyFusion_Ridge, AE_LatentFusion, and WeightedLate_Fusion—were implemented for comparison with the proposed gated fusion method. Under fivefold cross-validation, Fusion_GatedRidge achieved the best performance, with an R² of 0.83, RMSE of 2.01 g·kg⁻¹, and RPD of 2.39. Compared with single-modality models, R² increased by up to 18.6% and RMSE decreased by up to 23.0%. The gating mechanism dynamically adjusted the contributions of Raman and VIS–NIR features, leading to more stable predictions with residuals largely within −2 to 2 g·kg⁻¹. Overall, the proposed model demonstrates that adaptive modality weighting enhances the exploitation of complementary spectral information and significantly improves SOM prediction accuracy. These findings offer a concise and effective multimodal fusion framework for laboratory-based soil nutrient assessment. 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

A field study was conducted on the plants of two grapevine cultivars, ‘Solaris’ and ‘Regent’, grafted onto an SO 4 rootstock (V. berlandieri × V. riparia) and characterized by strong growth and yield. The effect of twelve treatments on the concentration of macroelements in leaf blades in the véraison phase, as well as selected soil parameters, was assessed in the sixth, seventh and eighth year of their application. The following treatments were tested: control (no fertilization), NPK (mineral fertilization 70 kg N/ha; 40 kg P/ha; 120 kg K/ha), mycorrhizal substrate (AMF—arbuscular mycorrhizal fungi), NPK + AMF, manure before planting, NPK + manure before planting, BioIlsa, NPK + BioIlsa, BF-Ecomix, NPK + BF-Ecomix, Ausma, NPK + Ausma. The aim of the study was to assess the nutritional status of the two cultivars after long-term use of mineral fertilizers, organic fertilizers, biofertilizers and biostimulants under Polish conditions in soil with a low organic matter (SOM) content prone to acidification. AMF, organic fertilizers and biostimulants were not a sufficient alternative to mineral fertilizers, especially with regard to N supply. BF-Ecomix treatment increased the content of Mg in the soil and the soil pH value. Regular use of NPK fertilization increased the concentration of leaf N and K, but did not improve the nutritional status of plants with P, despite doubling its content in the soil compared to control. NPK fertilizers worsened the availability and accumulation of Mg and caused soil acidification, but resulted in a slight increase in total soil N and SOM. No significant differences were noted in the mineral status of both cultivars under the same fertilization treatments but liming improved the leaf Ca status in ‘Solaris’. Fertilization of grapevines, which have started to be cultivated in Poland due to the warming climate, requires further study. Mineral fertilization should not be routine, but rather constantly readjusted, taking into account the soil fertility and mineral status of plants, in order to use the nutrients more effectively and avoid their unfavorable effects on plants and soil. Full article

Long-term fertilization affects soil nutrient levels and aggregate stability, eventually altering crop yield. However, their responses to organic fertilizer application and straw returning are still unclear, particularly as the contributions of soil nutrient levels and aggregate stability on crop yields remain poorly quantified. Therefore, topsoil samples (0–20 cm) were collected from six fertilization treatments in a long-term (13-year) Shajiang black soil field experiment with no fertilization (CK), chemical fertilization (NPK), 50% NPK plus pig manure (50%NPKP), 50% NPK plus cattle manure (50%NPKC), 70% NPK plus pig manure with straw return (70%NPKPS), and 70% NPK plus cattle manure with straw return (70%NPKCS). We examined the characteristics of crop yield, soil nutrient levels, and soil aggregate stability parameters, including under different long-term fertilization treatments. The results show that long-term fertilization significantly influenced the distribution of soil nutrients and soil aggregates in Shajiang black soil. Compared to CK, organic fertilizers and straw returning significantly increased the soil organic matter (SOM), total nitrogen (TN), and total phosphorus (TP) contents but decreased soil pH, respectively, indicating the best strategies for improving soil fertility. Compared to the CK and NPK treatments, long-term organic fertilization and straw returning significantly increased the mean weight diameter (MWD) and geometric mean diameter (GMD) values and significantly decreased the fractal dimension (Dm) and mean weight-specific surface area (MWSSA) values, with the 70%NPKCS treatment showing the most pronounced effect of improving aggregate stability. A redundancy analysis revealed that SOM and TN exert significant effects on aggregate stability. Furthermore, a stepwise regression analysis showed that SOM and TN were positive factors affecting the yields of wheat and maize, while MWD and pH were negative factors affecting wheat yield, demonstrating that high crop yields are derived from soils with limited stability and high fertility. Thus, our findings indicate that the integrated application of cattle manure with straw returning was the most effective strategy to promote soil nutrient accumulation, improve aggregate stability, and enhance crop yield, albeit with the potential risk of soil acidification, which requires management in the Shajiang black soil (Vertisol) region of Northern China. Full article

This study explored how top-dressed biogas slurry at winter wheat’s (Triticum aestivum L.) jointing stage (JS) and grain-filling period (GP) affects soil enzyme–microbe interactions, aiming to address nutrient supply–crop demand mismatches. A field experiment with five treatments (water [CK], chemical fertilizer [CF], and three biogas slurry topdressing regimes [S1–S3]) was conducted. Soil samples (0–20 cm) were collected at JS, flowering stage (FS), GP, and reaping period (RP) to analyze soil properties (total nitrogen [TN], available phosphorus [AP], available potassium [AK], soil organic matter [SOM], ammonium nitrogen [AN], pH), enzyme activities (urease [UE], neutral phosphatase [NP], sucrase [SC], catalase [CAT]), and microbial community abundance (via Illumina NovaSeq sequencing). Results showed biogas slurry altered enzyme activities, microbial structure (e.g., Actinomycetota, Ascomycota), and their interactions by regulating soil properties. JS application boosted Pseudomonadota and UE activity, GP application increased Ascomycota and CAT activity, and S3 had the most complex enzyme–microbe network, enhancing nutrient cycling. The analysis indicated that UE activity was strongly and positively correlated with several bacterial phyla (e.g., Planctomycetota, Verrucomicrobiota) (p < 0.01) and fungal phyla (e.g., Ascomycota) (p < 0.01). Full article

The fragile ancient ‘Shuikoulin’ forests, which provide critical habitats for the critically endangered Blue-crowned Laughingthrush, are increasingly degraded by soil contamination and heavy metal pollution. This study examines the rhizosphere environment of four key ancient tree species in the bird’s core habitat, focusing on soil properties, heavy metal accumulation, and the structure of arbuscular mycorrhizal (AM) fungal communities. The results revealed that Liquidambar formosana showed the highest total nitrogen (TN) and available phosphorus (AP), whereas Quercus chenii had the lowest soil organic matter (SOM). The primary heavy metal contaminant across all tree species was Cd (Igeo > 2), followed by the metalloid As. We detected 41 AM fungal species spanning 7 genera, with Glomus dominating (84.19% relative abundance). OTU richness was highest in Cinnamomum camphora and L. formosana (110 each), followed by Q. chenii (88) and Castanopsis sclerophylla (75). Structural equation modeling indicated that soil nutrients (TN, TP, AP, SOM) suppressed the accumulation of V, Cr, Ni, and Cu, thereby indirectly favoring Glomus and Paraglomus. In contrast, higher pH and total potassium (TK) levels promoted Co and Zn bioavailability and negatively affected Acaulospora and other minor genera. Tree species identity directly modulated these interactions. Our findings demonstrate that ancient tree species shape AM fungal assembly through distinct rhizosphere geochemical niches, providing a mechanistic basis for restoring degraded habitats critical to endangered species conservation. Full article

The low water and fertiliser utilisation efficiency and soil quality degradation caused by high water and fertiliser inputs are the primary challenges facing goji berry cultivation in arid regions. A two-year field experiment was conducted from 2021 to 2022. The experiment included three irrigation rates (I₁, I₂, I₃) of 2160, 2565, and 2970 m³·hm⁻² and three nitrogen application rates (N₁, N₂, N₃) of 165, 225, and 285 kg·hm⁻² to quantify their impacts on soil nutrients, enzyme activity, and goji berry yield in the root zone. Results indicate that the indicators of soil nutrients decrease with increasing soil depth, with depths of 0–20 cm accounting for 24.80–72.48% of total content. With fertility period progression, soil organic matter at depths of 0–80 cm exhibits a “folded-line” trend, while total nitrogen, nitrate nitrogen, and available phosphorus show an “M”-type trend. At depths of 0–40 cm, the proportions of urease, sucrase, and alkaline phosphatase activities all exceeded 70%. At I₁ irrigation rate, enzyme activities gradually increased with rising nitrogen application rates. At I₂ and I₃ irrigation rates, enzyme activities first increased, then decreased with increasing nitrogen application. The highest yields of both fresh and dried fruits were achieved at I₂N₂ treatment, increasing by 14.17% and 14.78%, respectively, compared to conventional management (CK). Analysis of the random forest model indicates that the soil-driven factors influencing yield formation include SA, UA, APA, HPA, SOM, NH₄⁺-N, and TP. Analysis of SQI and yield fitted data indicates that water–nitrogen coupling significantly influences wolfberry yield by regulating soil quality. Partial least squares (PLS-PM) showed that N application and irrigation of soil nutrients did not cause a significant indirect impact on goji berry yield, but a significant positive effect on goji berry yield occurred through enzyme activity. Full article

Intensive land use in the Argentine Pampas has led to soil degradation, yet links between soil organic matter (SOM) composition, enzyme activity, and fungal communities remain unclear. This study compared contrasting ecoregions and land uses: pristine (PI), pasture (PA), crop rotation with cover crops (RO), and monoculture (MO). Infrared spectra showed that PI soils in Anguil had higher absorbance in hydroxyl/amine (3400 cm⁻¹: 0.90 ± 0.08) and carbonyl (1750 cm⁻¹: 0.52 ± 0.12) bands than MO soils (0.47 ± 0.30 and 0.35 ± 0.06; p < 0.05), indicating greater SOM diversity. Pergamino soils showed smaller differences, reflecting site-specific effects. Enzyme activities also responded to land use. In Anguil, xylosidase, β-1,4-N-acetylglucosaminidase, and phosphatase peaked under PI (40, 127, and 443 nmol g⁻¹ h⁻¹). In Pergamino, xylosidase and β-1,4-N-acetylglucosaminidase were higher under PA and PI, indicating enhanced microbial functionality under low disturbance. Fungal composition varied with land use and location: Mortierellomycetes dominated in Pergamino, while Leotiomycetes and Agaricomycetes were more abundant in PI and PA, and Dothideomycetes increased in MO and RO. Despite compositional shifts, fungal diversity changed little. Integrating chemical, biochemical, and molecular indicators revealed how land-use intensification modifies SOM and microbial processes in Pampas soils. Full article

Drought poses a severe challenge to ornamental tree growth under climate change. This study employed a 2 × 4 factorial design—with two soil moisture levels (80–85% vs. 50–55% field capacity) and four nitrogen treatments (NN: no nitrogen; NO: nitrate nitrogen; NH: ammonium nitrogen; MN: mixed nitrate-ammonium nitrogen)—to examine the efficacy of nitrogen addition in enhancing drought resistance in Machilus yunnanensis seedlings. Results revealed that (1) drought stress leads to the acidification of rhizosphere soil, resulting in a decrease of 7.67%, 29.51%, 14.07%, and 44.09% in the content of soil organic matter (SOM), available phosphorus (AP), available potassium (AK), and dissolved organic nitrogen (DON), respectively. This adverse change directly impacts plant growth; it is manifested by a significant reduction of 45% in total chlorophyll (T Chl), a 67.18% decrease in photosynthetic rate (Pn), as well as reductions of 10.61%, 27.59%, 14.81%, and 12.35% in plant height, leaf, stem, and total biomass, respectively. (2) The application of all three forms of nitrogen helps alleviate drought stress, as evidenced by the recovery of photosynthetic levels and the reduction in malondialdehyde (MDA) content, with ammonium-N exhibiting superior efficacy over nitrate-N across most metrics. (3) Strikingly, the mixed nitrogen form outperformed singular applications by demonstrating multifaceted advantages: It maintains soil pH levels and rhizosphere nutrient availability under drought conditions, particularly with a 10.99% and 33.44% increase in dissolved organic nitrogen and available phosphorus content, respectively. More importantly, under drought stress, it increased leaf water content by 20.31%, nitrogen use efficiency by 15.67%, and photosynthetic nitrogen use efficiency by 439.44%, promoted the accumulation of osmolytes, while upregulating antioxidant enzyme activity to counteract osmotic imbalance and alleviate oxidative damage. These findings highlight that nitrogen supplementation, particularly mixed nitrogen application, enhances drought resistance in M. yunnanensis, offering a viable management strategy to sustain urban tree landscapes in water-limited environments. Full article

Soil organic matter (SOM) is a key component of nutrient cycling and soil fertility in terrestrial ecosystems. SOM is of great significance to the stability of terrestrial ecosystems and the improvement of soil productivity; to further exert its role, it is first necessary to clarify its actual distribution and occurrence status in specific regions. Under the combined impacts of intensive agriculture, unreasonable farming practices, and climate change, the SOM content in the Songnen Plain is showing a degradation trend, posing multiple stresses on its soil ecosystem functions. This study aims to systematically track the dynamic changes of SOM in the Songnen Plain, assess its spatiotemporal evolution characteristics, and reveal its driving mechanisms. A total of 113 representative soil profiles were selected in 2023; standardized excavation and sampling procedures were employed in the Songnen Plain. Soil pH, SOM, total nitrogen (TN), total phosphorus (TP), total potassium (TK), particle size (PSD), texture, and Munsell soil colors of samples were determined. Temporal variation characteristics, as well as horizontal and vertical spatial distribution patterns, in SOM content in the Songnen Plain were assayed. Structural equation modeling (SEM), together with freeze–thaw of soil and soil color mechanism analyses, was applied to reveal the spatiotemporal dynamics and driving mechanisms of SOM. The result indicated that the distribution pattern of SOM content in horizontal space shows higher levels in the northeastern region and lower levels in the southwestern region, and decreased with increasing soil depth. SEM analysis indicated that TN and PSD were the main positive factors, whereas bulk density exerted a dominant negative effect. The ranking of contribution rates is TN > TK > TP > PSD > annual average temperature > annual precipitation > bulk density. Mechanistic analysis revealed a significant negative correlation between SOM content and R, G, B values, with soil color intensity serving as a visual indicator of SOM content. Freeze–thaw thickness of soil was positively correlated with SOM content. These findings provide a scientific basis for soil fertility management and ecological conservation in cold regions. Full article

Landslides are a major natural hazard capable of causing severe damage to infrastructure, ecosystems, and human life. They result from complex interactions of geological, hydrological, and environmental factors, with soil properties playing a crucial role by influencing the mechanical behavior and moisture dynamics of slope materials that drive initiation and progression. In South Africa, few studies have examined soil influences on landslide susceptibility, and none have been conducted in the Eastern Cape Province. This study investigated the role of soil physical and chemical properties in landslide susceptibility by comparing profiles from landslide scars and stable sites in the Port St. Johns and Lusikisiki region. Samples from topsoil and subsoil horizons were analyzed for soil organic matter (SOM), cation exchange capacity (CEC), saturated hydraulic conductivity (Ksat), exchangeable sodium adsorption ratio (SARexc), and texture. Statistical analyses included the Shapiro–Wilk test to evaluate data normality. For inter-profile comparisons, Welch’s t-test was applied to normally distributed data, while the Mann–Whitney U test was used for non-normal distributions. Intra-profile differences across more than two groups were assessed using the Kruskal–Wallis test for the non-normally distributed data. Results showed that landslide-prone soils had higher SOM, CEC, and Ksat in topsoil, promoting moisture retention and rapid infiltration, which favor pore pressure build-up and slope failure. Non-landslide soils displayed higher sodium-related indices and finer textures, suggesting more uniform water retention and resilience. Vertical variation in landslide soils indicated hydraulic discontinuities, fostering perched saturation zones. Findings highlight landslide initiation as a product of interactions between hydromechanical gradients and chemical dynamics. Full article

Saline–alkali soils represent a significant reserve of arable land, playing a vital role in ensuring national food security. Given that saline–alkali soil has low soil organic matter (SOM) and soil nutrient contents, and that soil quality degradation poses a threat to regional high-quality agricultural development and ecological balance, this study took coastal saline–alkali land as a case study. It adopted the extreme gradient boosting (XGB) model optimized by the tree-structured Parzen estimator (TPE) algorithm, combined with in situ hyperspectral (ISH) and spaceborne hyperspectral (SBH) data, to predict and map soil organic matter and four soil nutrients: alkali nitrogen (AN), available phosphorus (AP), and available potassium (AK). From the research outputs, one can deduce that superior predictive efficacy is exhibited by the TPE-XGB construct, employing in situ hyperspectral datasets. Among these, available phosphorus (R² = 0.67) exhibits the highest prediction accuracy, followed by organic matter (R² = 0.65), alkali-hydrolyzable nitrogen (R² = 0.56), and available potassium (R² = 0.51). In addition, the spatial continuity mapping results based on spaceborne hyperspectral data show that SOM, AN, AP, and AK in soil nutrients in the study area are concentrated in the northern, eastern, southern, and riverbank and estuarine delta areas, respectively. The variability of soil nutrients from large to small is phosphorus, potassium, nitrogen, and organic matter. The SHAP (SHapley Additive exPlanations) analysis results reveal that the bands with the greatest contribution to the fitting of SOM, AN, AP, and AK are 612 nm, 571 nm, 1493 nm, and 1308 nm, respectively. Extending into realms of hierarchical partitioning (HP) and variation partitioning (VP), it is discerned that climatic factors (CLI) alongside vegetative aspects (VEG) wield dominant influence upon the spatial differentiation manifest in nutrients. Meanwhile, comparatively diminished are the contributions possessed by terrain (TER) and soil property (SOIL). In summary, this study effectively assessed the significant variation patterns of soil nutrient distribution in coastal saline–alkali soils using the TPE-XGB model, providing scientific basis for the sustainable advancement of agricultural development in saline–alkali coastal regions. Full article

Increasing attention is being paid to the use of cover crops as a means of improving soil quality, particularly in relation to soil organic matter (SOM) accumulation and aggregate stability. This study evaluated the effects of soil texture, soil depth, and cover crop type on soil organic carbon (Corg), labile carbon (C_L), and soil structure under field conditions in western Slovakia. A field experiment compared two texturally distinct Phaeozem soils—silty clay loam and sandy loam —and two cover cropping strategies: pea (Pisum sativum L.) monoculture and a four-species mixture of flax (Linum usitatissimum L.), camelina (Camelina sativa L.), white mustard (Sinapis alba L.), and Italian millet (Setaria italica L.). Fine-textured soil accumulated up to 50% more Corg and 1.5 times more C_L than sandy soil, while aggregate stability was up to 90% higher. The surface layer (0–10 cm) contained more SOM, but the deeper layer (10–20 cm) showed greater aggregate stability. Pea cultivation increased total organic carbon, whereas the diverse mixture enhanced labile carbon content and promoted the formation of smaller yet more stable aggregates. Strong correlations between C_L and aggregate stability confirmed the key role of labile organic matter fractions in soil structural stabilisation. Overall, the results demonstrate that the interaction between soil texture and cover crop diversity critically shapes SOM dynamics and soil structure. Combining diverse cover crops with fine-textured soils provides an effective strategy to enhance soil quality, carbon sequestration, and long-term agricultural sustainability. Full article

Soil organic matter (SOM) plays a fundamental role in soil fertility and ecosystem functioning. In calcareous soils, SOM quantification is often challenging due to carbonate interference. This study aimed to compare three common analytical methods for SOM determination: the Anne method, the modified Walkley–Black method, and the Loss on Ignition (LOI) method, with and without decarbonation. Twenty-five soil samples were collected from a calcareous parcel in the Bordj Bou Arreridj region (Algeria), and SOM content was analysed using all methods. The results revealed substantial variability in SOM content across methods, reflecting differences in sensitivity to carbonates and efficiency of organic carbon oxidation. The Anne method, considered the reference technique, yielded the highest mean SOM content (3.61%), followed by LOI without decarbonation (3.41%), the modified Walkley–Black method (2.96%), and LOI with decarbonation (2.55%). Strong correlations were observed between methods, particularly between the Anne method and LOI with decarbonation (R² = 0.91), confirming the latter as a reliable alternative. Decarbonation significantly reduced SOM overestimation, as demonstrated by paired statistical tests and a large effect size (Cohen’s d = 2.95). Linear regression models were established to estimate SOM from LOI results, providing a cost-effective approach for rapid assessment. These findings highlight the importance of method selection according to soil type, the need for standardised protocols, and the value of LOI with decarbonation as a robust, practical, and economical method for SOM determination in calcareous soils. Full article