Search Results (2,646)

The coupled mechanisms governing carbon–nitrogen turnover across soil particle-size fractions remain unclear. This study investigated soil organic carbon (SOC) and total nitrogen (TN) dynamics across five particle-size fractions in Cambisols under conventional and organic orchard management. Results showed that particle size dominated δ¹³C variation (Partial η² = 0.36) while management practice regulated δ¹⁵N variation (Partial η² = 0.38), revealing a fundamental decoupling of C and N cycling within the particle-size matrix. The progressive linear increase in δ¹³C with declining particle size signaled a transition of SOC from net accumulation to net decomposition, accompanied by directional carbon translocation from coarse sand to clay fractions. A universal critical soil pH threshold ~5.3 was identified, where inter-particle-size carbon flow reached its maximum while microbial decomposition was minimized. Organic management reduced the intensity of plant-derived carbon translocation between particle-size fractions, yet substantially enhanced microbial anabolism, leading to drastically elevated stocks of microbial necromass carbon (MNC) in both particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) pools. Notably, the relative proportional distribution of POC and MAOC remained unchanged across the two management practices, which was intrinsically constrained by the inherent textural properties of the studied Cambisols. Counterintuitively, progressive soil acidification concurrently increased SOC lability and overall carbon stabilization, a paradox that directly demonstrated decoupling between chemical oxidizability and physical protection during particle-size carbon translocation. These findings confirmed incomplete carbon–nitrogen coupling within soil particle-size fractions, and demonstrated that SOC stabilization was co-regulated by organo-mineral interactions and microbial processing, whereas nitrogen dynamics were primarily modulated by exogenous management-derived inputs. This work provided novel insights for optimizing agricultural management strategies to synergistically enhance soil fertility and long-term carbon sequestration. Full article

Clayey sand is a typical transitional coastal alluvial soil controlled by both coarse-grain friction and fine-grain cementation. Current studies focus mostly on remolded samples, lacking systematic understanding of water-induced structural degradation and quantitative physico-mechanical correlations for natural undisturbed clayey sand. In this work, 74 intact undisturbed specimens (0.5–23.0 m depth) were tested via basic physical tests, one-dimensional consolidation and consolidated-undrained triaxial shear tests. Pearson correlation analysis was performed to establish prediction relationships between routine physical indices and mechanical parameters. Results show the soil is classified as SC clayey sand with 39.70% fines and an average natural water content of 23.17%. Natural water content dominates soil engineering performance, presenting strong linear correlations with dry density and void ratio (|r| = 0.90). Higher water content and void ratio increase compressibility and reduce shear strength. The compression coefficient and compression modulus exhibited a consistent nonlinear relationship, reflecting the inherent linkage between these two compression parameters. Burial depth has little influence on soil properties, and plasticity index only serves for soil classification. Mechanistically, increasing moisture may thicken adsorbed water films, weaken interparticle contact and matric suction, and the fine particle-filled skeleton may further enhance the water sensitivity of the soil. The established prediction models support fast evaluation of soil mechanical behaviors, offering theoretical and practical support for geotechnical design of similar coastal clayey sand strata. Full article

The surface soil in the Shendong mining area is dominated by aeolian sand and sandy sediment, while precipitation is limited, and evaporation is intense. Under these conditions, shallow reconstructed soil has difficulty retaining plant-available water, which constrains vegetation restoration. This study evaluated how low-range increases in fine-particle clay content affect both water retention and upward water conduction in sandy reconstructed soil. Sandy material from the Shangwan mining area and exogenous river clay were mixed into four treatments, and soil water characteristic curves (SWCCs) were determined by centrifuge over 10–1000 kPa matric suction. The data were fitted with the Van Genuchten model and combined with capillary-rise tests. The results showed that increasing fine-particle content shifted the SWCC upward and raised both saturated and residual volumetric water contents. SN10 reached 17.18% and 5.55% volumetric water content at 10 and 1000 kPa, respectively, and its effective water capacity in the 33–1500 kPa range was 17.9% higher than that of ST. At the same time, fine-particle enrichment in the bottom layer reduced wetting-front rise during capillary testing, indicating a trade-off between water storage and upward replenishment. Within the tested fine-particle range, moderate clay addition improved the hydraulic performance of sandy reconstructed soil, but soil design should balance precipitation retention, infiltration, and capillary supply. Because each treatment and soil-column configuration was represented by only one independently prepared experimental unit, experimental variability and reproducibility could not be evaluated. This study should therefore be regarded as a preliminary and exploratory laboratory assessment conducted under a specific set of material-preparation procedures, specimen geometries, and boundary conditions. The results describe specimen-level hydraulic contrasts rather than reproducible treatment effects and should not be directly generalized to field-scale soil reconstruction. They support a preliminary hypothesis for future replicated testing: fine-particle enrichment may increase water retention while slowing upward capillary replenishment. Full article

Understanding the penetrability of synthetic aperture radar (SAR) signals into near-surface materials is a prerequisite for using SAR observations to infer subsurface physical properties. However, direct measurements of penetration depth under controlled material conditions remain limited, especially for comparisons across radar bands, soil water content, sand, and hard ground surfaces. This study provides direct laboratory measurements of L-band and S-band SAR signal penetration using a ground-based SAR system in a microwave anechoic chamber. Unlike penetration depth inversion studies, dihedral corner reflectors were buried at known depths. We identified the depth at which each reflector response became indistinguishable from the background. The reported values represent effective signal penetration intervals under the laboratory geometry. The chamber effectively reduced thermal noise and electromagnetic interference. At an incidence angle of 40°, the L-band signal penetrated 45–50 cm and 30–35 cm in clay samples prepared at 4% and 18% volumetric soil water content (SWC), respectively. The L-band penetration depth was 85–90 cm in dry sand with 3% SWC, about 9 cm in asphalt, 5 cm in gravel, and 2 cm gravel plus 7 cm asphalt in a composite hard-surface layer. The S-band penetration depth was 20–25 cm in loose clay, 15–20 cm in compacted clay, and 15–20 cm in sandy loam under the tested conditions. These results show that SAR penetration depends strongly on wavelength, water content, material type, and compaction/surface condition. We also demonstrate that thin hard ground surfaces can allow measurable L-band penetration. Our findings provide experimental benchmarks for interpreting SAR signals in subsurface parameter retrieval and sand-layer characterization. Full article

Soil formation in post-mining areas is strongly influenced not only by parent material but also by the vegetation introduced during reclamation. Tree species affect pedogenic processes through litter input, root activity and associated microbial communities. This study investigates soil development in reclaimed post-mining landscapes, focusing on the combined influence of tree species and substrate properties. Two forest sites in Poland were analysed: Szczakowa (former open-pit sand mine) and Bełchatów (lignite mine spoil heap), 30–40 years after reclamation and afforestation with four dominant species: silver birch, European larch, Scots pine and red oak. Differences in soil development were observed among tree species. Stands with deciduous trees (birch and oak) were generally associated with clearer horizon differentiation, higher soil organic carbon and nitrogen content, and more pronounced iron redistribution compared with coniferous stands. The mean thickness of the combined organic-rich surface horizons was 12.4 cm at Szczakowa and 10.8 cm at Bełchatów. Coniferous species were more often linked with soil acidification and early stages of podzolisation-like processes, particularly in sandy substrates, whereas soils under deciduous species showed features related to brunification and organic matter incorporation. The study also included a comparison of soil classification systems, indicating that the World Reference Base for Soil Resources (WRB) offers a flexible framework for describing young and anthropogenically transformed soils compared with traditional national classifications. From a sustainability perspective, the results highlight that strategic species selection during reclamation, specifically promoting birch on sandy substrates and oak on heterogeneous technogenic substrates, enhances soil organic carbon accumulation, nutrient retention and iron cycling, thus contributing to the long-term restoration of ecosystem services on degraded post-mining landscapes. Full article

Accurate prediction of wetted width and wetted depth is essential for optimizing water use efficiency in drip irrigation systems. Existing empirical models are often restricted to specific soil textures and cannot adequately capture the complex nonlinear interactions among soil hydro-physical and chemical properties, irrigation variables, and different soil textures. This study evaluated four machine learning algorithms—Linear Support Vector Machine (Linear SVM), Medium Gaussian Support Vector Machine (Medium Gaussian SVM), Matern 5/2 Gaussian Process Regression (GPR), and Boosted Tree Regression—for predicting wetted width and wetted depth in sand and sandy loam soils. Model inputs included emitter discharge, irrigation duration, and selected soil hydro-physical and chemical properties. Models were developed using a 70% training dataset and validated with the remaining 30%. The Matern 5/2 GPR achieved the highest training accuracy for wetted width (R² = 0.99; RMSE = 0.74) and wetted depth (R² = 0.98; RMSE = 0.90), but validation errors increased to RMSE values of 2.27 and 3.84, respectively. Medium Gaussian SVM yielded the lowest validation RMSE (2.11) for wetted width, whereas Boosted Tree Regression achieved the best wetted depth prediction (RMSE = 2.11; MAE = 1.69). These findings demonstrate the importance of model-specific selection for reliable irrigation management. Full article

Pile foundations used for structures, such as tall buildings and bridges, especially in coastal and heavily flooded areas, experience uncertain lateral loads. The wave action of water applies a lateral load on the pile, which cannot be predicted accurately. However, the impact of the vertical load significantly increases the pile’s lateral capacity. This suggests more specific research is required into this particular area, especially considering the complex interactions involved. This study focused on the lateral strength of a single pile with a vertical load in layered soils. Using an experimental setup, the horizontal deformation of the pile with an increasing applied compression effect in different soil beds was determined. Analyses were extended using FEM for various combinations of clay and sand layers under varying vertical loads. Initially, the vertical behavior of each pile was determined to varying percentages. The results indicate that the lateral capacity of the pile increases significantly up to 60% of the applied vertical load in both sand and clay. But for clay–sand layer combinations, for an applied vertical load, 100% lateral capacity showed 1.34 times improvement. FEM findings are similar to the experimental results; as the vertical load reaches up to 60% on various soil layers, the lateral capacity improves. Full article

Biological soil crusts (BSCs) are important components of dryland ecosystems, yet nutrient patterns in adjacent uncovered soils remain unclear. We surveyed 70 sites across the Gurbantunggut Desert and collected 209 composite samples from the adjacent 0–5 cm surface-soil layer, categorized into three groups: uncrusted bare sand (n = 32), soil adjacent to algal–lichen crusts (n = 48), and soil adjacent to moss crusts (n = 129), with bare sand serving as the uncrusted reference category. The results showed that: (1) total nitrogen differed among the three BSC-associated soil categories (p = 0.041), whereas soil organic carbon, total phosphorus, and total potassium did not (all p > 0.05); (2) NO₃⁻-N, NH₄⁺-N, extractable inorganic N, NaHCO₃-extractable phosphorus, and NH₄OAc-extractable potassium differed significantly among categories (all p < 0.001) and were generally highest in soil adjacent to moss crusts; and (3) random forest models explained approximately 38–65% of nutrient variation and identified EC, total nitrogen, and the site-level BSC metric as the leading predictors. The final piecewise structural equation model explained 35.3–76% of nutrient variation. These findings indicate marked regional heterogeneity in extractable nutrient fractions associated with different BSC types. Full article

Bridge scour analysis, especially scour depth calculation practices implemented mostly by hydraulics and geotechnical engineers, was traditionally built upon flume tests with cohesionless materials, e.g., sands. As a result, the analysis of bridge scour in cohesive materials, i.e., cohesive soils and scour-susceptible rocks, was less understood and thus has been gaining increasing attention. This paper presents a state-of-the-practice survey on the analysis of bridge scour in cohesive materials represented by cohesive soils and scour-susceptible rocks. This includes a literature review covering the concepts and understanding of scour susceptibility, material sampling, erodibility tests, bridge scour calculation methods for cohesive soils and rocks, and a summary of the information gathered in communications with engineers from state Departments of Transportation (DOTs) in the U.S. Through this review, it was found that scour analysis in cohesive soils and scour-susceptible rocks continues to require further research and engineering development despite substantial recent progress. Undisturbed sampling and appropriate erodibility characterization remain critical for reliable scour prediction. Existing research and engineering practice continue to focus primarily on pier scour, while comparatively limited information is available for contraction and abutment scour in cohesive soils and rock formations. The survey of state DOT practices further indicates considerable variability in the implementation of scour evaluation procedures for cohesive and rock materials, including the use of SRICOS-EFA, the Erodibility Index Method, NCHRP 717, agency-developed procedures, and geotechnical consultation workflows. Full article

Helical piles are increasingly used in foundation engineering due to their rapid installation, economic advantages, and superior structural performance. Their applicability to various soil conditions has led to widespread use in both onshore and offshore structures. Therefore, their behavior under vertical and lateral static loads, as well as repeated cyclic loading, must be thoroughly evaluated. Helical piles are installed by applying torque through the helical plates attached to their shafts, causing disturbance in the surrounding sand. The influence of this disturbance on pile load-bearing capacity should not be overlooked. In this study, large-scale laboratory tests were conducted on helical piles with different helix diameters and configurations in dry dense sand. The effects of installation-induced sand disturbance and bidirectional cyclic lateral loading on the lateral and uplift capacities were investigated. The results showed that installation-induced sand disturbance reduced the lateral capacity, whereas increasing the helix diameter significantly enhanced the uplift capacity. After cyclic loading, the lateral and uplift capacities of the straight pile decreased by approximately 35% and 55%, respectively, while the lateral capacity of the helical piles was maintained. These findings highlight the importance of considering installation-induced sand disturbance and cyclic loading in the design of helical piles in dry dense sand. Full article

The study on the valorization of natural resources through cowpea cultivation represents a challenge to mitigate the negative effects of climate change on the environment and on the food security of the population in drought-affected areas globally, and specifically in the sandy soil area of Romania. Thus, the existence in Romania of an area of approximately 439,000 ha with sands and sandy soils, soils with low natural fertility (below 1.2% humus) and with deficient hydrophysical properties, implies finding solutions for their efficient valorization through ecological modeling of the species/varieties structure, depending on the adaptability of the plant in a given area. In this sense, given the economic importance of cowpea, given by the plant’s properties (drought resistance, source of increasing the organic matter content in sands, source of atmospheric nitrogen fixation, good precursor plant, source of protein for humans and animals), the cultivation of this species in a sustainable agricultural system is outlined, as an alternative solution to the cultivation of other leguminous plants. Considered a crop suitable for a climate change scenario, the conservation of genetic biodiversity and the establishment of technological inputs are essential objectives for promoting cowpea in a sustainable agricultural system, given the increasing drought in the world and the increasing need for protein. Full article

Microbially Induced Carbonate Precipitation (MICP) and Enzyme-Induced Carbonate Precipitation (EICP) have emerged as promising sustainable alternatives to conventional ground improvement techniques. This paper presents a focused review of Cone Penetration Test (CPT)-based assessment of bio-cemented soils, synthesizing findings from studies spanning laboratory column tests, centrifuge models, and field trials. The review examines how CPT measurements, including tip resistance (q_c), sleeve friction (f_s), and pore pressure response (u), reflect the cementation mechanisms, treatment heterogeneity, soil-type effects, and scale dependency characteristic of MICP and EICP treatments. Key findings indicate that MICP and EICP produce distinct CPT responses: MICP-treated sands generally show stronger cementation-related stiffness signatures and more persistent improvement, whereas EICP-treated soils more commonly exhibit sharper near-surface q_c gains that may be more susceptible to reduction with time. However, long-term field CPT evidence for EICP durability remains limited. CPT interpretation is more uncertain in fine-grained and heterogeneous soils, where low permeability, preferential flow, localized cementation, and penetration-induced disturbance can produce irregular profiles that are difficult to interpret from q_c alone. Fundamental limitations of conventional q_c-based CPT interpretation in bio-cemented ground are identified, including its inability to decouple cementation effects from density, stress state, and environmental variability. Multi-sensor CPT platforms integrating shear-wave velocity probes, acoustic emission monitoring, and geochemical sensors are identified as the most promising pathway toward reliable characterization. Three priority developments are outlined: standardized CPT interpretation protocols with calibrated conversion functions for major soil types, validated multi-sensor platforms deployable under field conditions, and machine-learning tools for spatial treatment quality assessment. This review provides a structured CPT-based synthesis of bio-cemented ground and establishes an interpretive basis for future standardized assessment protocols in geotechnical practice. Full article

Critical shear stress and erosion rate are two key parameters in predicting sediment transport under hydrodynamic loads. Seepage and clay content can significantly influence these two critical parameters. Using an in-house erosion–seepage system (ESS), this study explores the erosion process in mixed soils and its relationship to seepage under steady currents. Unlike previous studies that focused on sandy seabeds or clay without seepage, this study considers a mixture of clay and sand and establishes relationships between erosion rate, critical shear stress, clay content, and seepage in sand–clay mixtures. It compares the applicability of two non-linear models to sand–clay mixtures with seepage. The developing variation patterns of their parameters are examined, and the mechanisms that influence these patterns are analyzed. Full article

In dryland ecosystems, the restoration of Salix psammophila shrubs plays a vital role in wind erosion control and sand stabilization. However, the temporal dynamics of soil particle-size distribution and erodibility during S. psammophila restoration remain poorly understood. To address this gap, we established a chronosequence of S. psammophila plantations in the Hobq Desert—a temperate desert in northern China—that had been restored for 6, 12, 15, 25, and 35 years, with adjacent shifting sand dunes serving as the control (CK). At each of the six sites, ten replicate plots were established, and soil samples were collected from the 0–20 cm layer, yielding a total of 60 samples. Multifractal parameters and the soil erodibility K factor were calculated to quantify the effects of stand age on particle-size distribution and erodibility. Principal component analysis (PCA) and a Random Forest model were then applied to factors associated for the observed changes. Compared with CK, soil nutrient and fine particle contents increased significantly with increasing shrub age, whereas pH and sand content declined continuously. Specifically, under S. psammophila plantations, organic carbon (OC), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), and alkali-hydrolysable nitrogen (AHN) contents increased continuously with stand age, while the soil texture became progressively finer. During long-term S. psammophila restoration, the ranges of the multifractal parameters D₀, D₁, D₂ and D₁/D₀ were 0.82–0.91, 0.59–0.71, 0.50–0.58, and 0.70–0.78, respectively. S. psammophila restoration exhibited pronounced multifractal characteristics, which reduced the heterogeneity of the soil particle-size distribution and made the distribution more uniform, thereby resulting in a more stable soil structure and a more balanced ratio of fine to coarse particles. The soil erodibility K factor indicated that soil erosion resistance gradually increased with stand age, with a 23.71% reduction at 35 years compared with CK. Random Forest analysis identified organic carbon (OC), total nutrients (TN, TP), pH, soil particle-size fractions (clay, silt, sand), D₁, D₂, and vegetation characteristics (aboveground biomass, AGB; plant density, PD) as important predictor variables for soil erodibility (p = 0.01, R² = 0.961). These findings provide new insights into the mechanisms by which long-term S. psammophila restoration improves soil structural stability and erosion resistance, offering a scientific basis for optimizing vegetation restoration and sustainable desert ecosystem management in arid regions. Full article

Accurate prediction of soil organic carbon (SOC) at fine resolution is crucial for precision soil management; however, existing national products for Hungary remain too coarse for farm-scale applications. Focusing on Hungarian croplands, we developed a 30 m resolution SOC map using multi-temporal bare-soil composites, DEM derivatives, SHAP interpretability and bootstrap uncertainty. Among five evaluated algorithms, the GBDT model achieved the best performance (test R² = 0.518, RMSE = 4.498 g·kg⁻¹, MAE = 3.499 g·kg⁻¹, RPIQ = 2.229, LCCC = 0.621). SHAP analysis revealed pronounced nonlinear effects of spectral and topographic variables within this modeling framework, with spectral predictors playing a dominant role in SOC prediction. Furthermore, the bootstrap uncertainty framework yielded a Prediction Interval Coverage Probability of 94.59% at the 95% confidence level, indicating reliable interval estimation for the test set. Spatial patterns of uncertainty varied considerably, with higher values in the western hills and southern sands, and moderate levels in the northern low-mountain areas. Benchmark comparisons showed that our 30 m map captures fine-scale heterogeneity often smoothed over by coarser products, while the uncertainty layer supports risk-aware interpretation. Overall, this study provides a regionally calibrated framework for mapping in similar heterogeneous agricultural landscapes, providing practical insights for local management. Full article