Clay Soil Research Articles

Available reports focus mostly on the effects of post-fermentation sludge (digestate) on soil organic carbon level, soil chemistry, and microbiology, and little is known about the impact on soil structural and mechanical properties. Therefore, the influence of different rates of digestate (1-15%) on the structure and strength of several soils, varying in grain size composition, pH, and organic matter content, was studied. The effects were analyzed by scanning electron microscopy, nitrogen adsorption, mercury porosimetry, bulk density, and mechanical stability tests. Organic sludge usually increased total porosity, average pore diameter, total pore volume, and diminished bulk density of all soil aggregates. Digestate addition significantly decreased the specific surface area of most clayed soils of the highest initial surface. The application of digestate increased the strength of initially most fragile sandy soil aggregates. The more intensive positive changes in the pore and surface characteristics and increase in mechanical strength of sandy soils highlighted the potential of the digestate application to enhance the stability and structure of less productive areas.

Objectives: To investigate the effect of lime and quarry dust, both individually and in combination, on the geotechnical properties of Puducherry inland clay using Artificial Neural Network (ANN) modelling. Methods: Clay samples were treated individually with varying proportions of lime and QD (7%, 14%, 21%, and 28% by dry weight) as well as in combination to assess improvements in geotechnical behaviour. Laboratory tests, including Atterberg limits, Free Swell Index (FSI), compaction characteristics, direct shear test, and Unconfined Compressive Strength (UCS), were conducted to evaluate changes in soil properties. To forecast the parameters of stabilized soil, the ANN Simulink model was simulated using a neural network fitting tool after training. Findings: The experimental findings showed that the plasticity index was reduced by 25% and 37% with lime and QD stabilization, respectively. Lime- and QD-stabilized clay reduced the optimum moisture content by 20% and 35%, while maximum dry density increased by 10% and 35%, respectively. Cohesion was reduced by 28% in both cases. Regarding UCS, lime-stabilized clay showed an increase up to 21% addition before declining, whereas QD-stabilized clay showed continuous strength gain. FSI decreased by 35% and 28% in lime- and QD-stabilized clay, respectively. The combination of both lime and QD showed superior performance due to synergistic effects. ANN modelling with statistical indicators (R2: 0.95–0.99, RMSE <30%, MAPE <20%) effectively predicted geotechnical properties with less than 25% error. Novelty: Utilizing QD provides a sustainable alternative to lime while improving the geotechnical performance of clay soil comparable to lime. Using QD as a stabilizer also helps in addressing environmental waste disposal issues. Keywords: Stabilization, Artificial neural network, Lime, Quarry dust, Simulink model

Aims: Acacia mearnsii tree has high economic value, and it can form a symbiosis with rhizobium bacteria. As an erosion control tree that grows in various types of soil, it is necessary to investigate the adaptability of acacia plants while in the nursery. This study aimed to determine the adaptability of acacia seedling growth to various types of soil. Study Design: The research was designed as an experimental study Place and Duration of Study: Padang West Sumatera, Lab of Biotechnology Andalas University, started from April to October 2023. Methodology: The method used in this research is a complete randomized design with seven treatments and five replications. The treatments were humus soil, beach sand, ultisol soil, coal mine, limestone soil, oxisol soil, and sandy loam soil. Variables observed were plant height, number of leaves, number of branches, number of root nodules, crown wet weight, crown dry weight, root wet weight, root dry weight, and plant dry weight. Data collected were analyzed using analysis of variance, and further statistical analysis was carried out using the Duncan Multiple Range Test at 5% significance level. Results: The results of this study indicate that A. mearnsii plants can adapt well to three soil types, including coastal sandy soil, ex-coal mine soil, and sandy clay soil, in addition to humus soil (used as the control treatment). These soil types can be effectively utilized for reclaiming marginal land. The adaptability of A. mearnsii plants is evident from the observed growth and yield parameters, which include an increase in the number of leaves, shoot wet weight, shoot dry weight, root wet weight, root dry weight, shoot-to-root ratio, and overall plant dry weight. Moreover, the parameters that show a positive correlation with plant dry weight include plant height, the number of leaves, and the number of branches. Interestingly, the formation of root nodules in ex-mining soil increased significantly up to 19 times compared to humus soil. Conclusion: In the seven types of soil used as planting media for adaptation study, the A. mearnsii could adapt well to coastal sand, former coal mines and sandy clay soil, thereby providing its promising potential as a soil conservation agent.

Abstract Indaziflam is a long-term residual weed control option for Georgia pecan [ Carya illinoinensis (Wangenh.) K. Koch] growers. As a nonselective cellulose biosynthesis inhibitor, indaziflam has a niche for broad-spectrum weed control with long residual activity in various perennial cropping systems. Indaziflam’s soil persistence and chemical behavior at various temperatures have not been fully evaluated; therefore, the objectives of these experiments were to: (1) quantify indaziflam soil dissipation under field conditions in two common Georgia soils and (2) evaluate indaziflam molecular stability as affected by temperature and time using laboratory techniques. Indaziflam soil dissipation followed first-order kinetics and was adequately described by the exponential decay equation. Indaziflam half-life in Greenville sandy clay loam and Faceville loamy sand was 96 and 78 d, respectively. Indaziflam half-life and soil clay content had a direct relationship, while indaziflam half-life and microbial biomass had an inverse relationship. Aqueous solutions of indaziflam were exposed to temperatures that ranged from 20 to 70 C for up to 672 h, with results indicating that temperature had no influence on indaziflam’s molecular stability.

Fuel traits are important determinants of fire behavior and regime in savannas and, thus, of how fire affects plant communities. However, whether these traits are correlated, predictable and how they are influenced by biotic and abiotic drivers remain to be rigorously evaluated. We hypothesized that, given their overall dependence on grass biomass, fuel traits were mutually correlated (via correlations to grass biomass), change predictably in space and time, and that they influence fire regimes. We sampled 31 plots distributed in five soil classes in a savanna‐dominated landscape in Brazil and measured the following surface fuel traits: fuel height, continuity, bulk density, bed flammability, composition, total load and grass load. We also obtained data on landscape predictors, such as soil clay content, fire history, climate, canopy cover, elevation , and on future (post‐sampling) fire incidence. We used Pearson correlation and principal component analyses to test for associations among fuel traits, and generalized linear model for assessing 1) landscape predictors effects on fuel traits; and 2) fuel trait effects on future fire incidence. We found two leading axes of fuel trait variability. The first axis was positively correlated with fuel height, continuity, total load, bed flammability, grass load and cover. In this axis, flammability increased with time since last fire and clay content and decreased with canopy cover and rainfall seasonality. The second axis was positively correlated with fuel bulk density, continuity, shrub and litter covers, and negatively with fuel bed flammability. In this axis, flammability decreased with canopy cover and clay content. Grass fuel load was the best predictor of future fire incidence. Our results suggest that fuel traits change predictably in space and time and explain variability in fire regimes in savannas. These findings contribute to a better understanding of fire regimes while providing important information for managers and decision makers.

Effect of remolding water content on cyclic stress–strain property of compacted clay soils

Calcium Speciation and Solubility in Tropical Agricultural Soil Clays

This article studies the compaction of clay soils. Clay soils are often used as building foundations. However, such a use is complicated by their specific properties, namely the dependence of structural properties, particularly deformation patterns and strength, on the compaction degree. Compaction is one of the most important properties of clay soil, largely determining its behavior under load. Compaction can be used as a classification indicator, as well as for preliminary assessment and prediction of the soil behavior under various stress-strain conditions. As is known, the compaction of clay soils is influenced by various factors: occurrence depth, sediment and clay composition, environment and compaction conditions. Purpose: The aim of this work is to refine the compaction classification of clay soils with the possibility of using for practical purposes. Methodology: The article analyzes the dependence of average density of dry soils on the natural moisture content in genetic soil types. Research findings: The current classification of clay soils is refined, depending on the dry soil density. The obtained dry soil density dependence ρ d = f ( W e ) determines the boundaries of W e , ρ d for certain genetic soil types.

ABSTRACT Blackgram ( Vigna mungo ) is an important pulse crop grown mainly under rainfed and partly under irrigated conditions in the North Interior Karnataka region of the Deccan Plateau of India. However, rising temperatures and unpredictable rainfall patterns due to climate change pose a significant threat to its consistent performance and productivity. To assess the effect of projected climates (2021–2040) on blackgram productivity in the region, the DSSAT‐CROPGRO model was used, which was calibrated and validated using experimental data recorded at the MULLaRP Scheme, University of Agricultural Sciences, Dharwad, India during the year 2022. The study considered two predominant soil types: black clay and red sandy soils across the study area. Under future climates, blackgram yield in the region is projected to decrease by 19.7% on black clay soils and up to 32.0% on red sandy soils compared to the current climate (2011–2020) period under rainfed situations. Among the 12 districts studied, the highest yield reduction under the projected climate was observed in Gadag (51.5% and 69.2%, respectively, in black clay and red sandy soils), followed by Haveri (43.7% and 56.2%, respectively, in black clay and red sandy soils).

Integration of Mineral Fertilization and Microbial Inoculants to Enhance Wheat (Triticum aestivum L.) Yield and Soil Fertility in Clay Soil.

Abstract Traditional laboratory analyses of soil texture and soil organic matter (SOM) are time consuming and labor‐intensive, so they are impractical to be measured at the same scale as routine nutrient testing. The objective of this study was to determine soil clay, sand, and SOM across a large number of samples by improving mixed‐land‐use predictive models proposed by Drescher et al. in 2024, creating a rice ( Oryza sativa L.)‐specific set of models that integrates soil pH, Mehlich‐3 extractable nutrients, and estimated cation exchange capacity (EstCEC). With a clustering analysis, a soil dataset containing 179 samples from major rice producing states in the United States was split into a training set (80%) for rice model development and a testing set (20%) for validation. Another dataset of 111 samples from Arkansas was used to compare the performance of rice models with mixed‐land‐use models. After validation, a high‐accuracy clay model ( R 2 = 0.84; RMSE = 68.14 g kg −1 ) was obtained using pH, phosphorous (P), potassium (K), calcium (Ca), and magnesium (Mg). The sand model containing pH, Ca, Mg, and EstCEC fit with moderate accuracy ( R 2 = 0.36; RMSE = 89.94 g kg −1 ). The best SOM model relied on pH, P, K, Mg, and EstCEC ( R 2 = 0.80; RMSE = 4.28 g kg −1 ). The Arkansas rice soil dataset showed that rice models enhanced SOM prediction ( R 2 increased from 0.78 to 0.81), and they improved the overall soil textural classification accuracy to 70% versus 58% by mixed‐land‐use models. While our models are suitable for clay and silt‐dominated classes, such as clay, silt loam, clay loam, and silty clay loam, they may not be for several sand‐dominated classes. This study provides a tool by which to efficiently and inexpensively estimate key soil physicochemical properties for agricultural decision‐making but the overall utility of our models for rice soil textural classification is limited at present.

The reutilization of waste plastic represents a significant concern due to its substantial economic and environmental impact. This article aimed to investigate the strength characteristics of clay soil stabilized by plastic bottles. We investigated the potential use of waste plastic bottles as sustainable soil stabilizers to enhance the geotechnical properties of clay soils. The experimental study involved collecting soil samples from the Wallaweyn District and performing laboratory tests, including unconfined compressive strength (UCS), California Bearing Ratio (CBR), Atterberg limits, and standard Proctor compaction tests, to determine the geotechnical properties of the clay soil. We added varying amounts of shredded plastic bottles (0.5%, 2%, 4%, and 6%) to soil samples to examine their effects on the geotechnical properties of clay soils. The addition of plastic bottles as reinforcement significantly increased the UCS and CBR values. The CBR and UCS test results indicate a direct correlation with the percentage of plastic bottles, up to 6%. The study findings demonstrated that the plastic content increased by 0.5%, representing the lowest of the observed percentages - 5% at shallower depths and 11% at greater depths - as reflected in the California Bearing Ratio. In terms of unconfined compressive strength, cohesion increased by 33.9% and 31.3% at QU. Moreover, the analysis identified that plastic content of 6% yielded the highest rate among all calculated percentages for both the California Bearing Ratio and unconfined compressive strength.

This study examined the impact of soil texture and seedling spacing on the germination and growth of Desmodium adscendens, a plant recognised for its medicinal and agroecological uses. Three types of soil were evaluated: sandy, silty and clayey, as well as three spacing between seedlings (0.5 m; 1 m; 1.5 m). The results showed that the sandy and silty soils produced faster and more uniform germination, with germination rates of over 90% by the thirteenth day after sowing. This performance was attributed to their light, well-aerated structure, which facilitated the circulation of oxygen and the lifting of dormancy. In contrast, the clay soil, which is more compact and less permeable, delayed germination and recorded the lowest germination rates. In terms of vegetative growth, plants grown in sandy soil showed the best results in terms of collar diameter, stem length and number of branches, followed by those grown in loamy soil. The clay soil limited the development of the plants, whatever the spacing used. Statistical analysis revealed that spacing had no significant effect on agronomic parameters (P > 0.05), which can be explained by the morphological plasticity of the species and its ability to adapt to different planting densities. These results confirm the potential of Desmodium adscendens to be integrated into sustainable cropping systems in the humid tropics.

Field study on the hydraulic behavior of heavy soil: Effects of biochar application rates.

Saffron (Crocus sativus L.) is prized for its stigma, a valuable spice rich in bioactive compounds crucial for various industries and traditional medicine. Enriched with bioactive compounds crucial for numerous industries and traditional medicinal practices, saffron cultivation expansion hinges on assessing the vegetative process in soils with low organic content. Optimal fertilization, considering plant and soil conditions, is crucial. Leaves indicate vegetative status and serve as an agricultural byproduct. In this study, saffron was grown in clay loam soil (1.88% organic matter) with supplementation of the bacterium Rhodobacter sphaeroides, spores of an arbuscular mycorrhizal fungus Glomus iranicum var. tenuihypharum, and both. Sole bacterium application increased leaf fresh and dry weight by 25.5% and 36.8%, respectively, demonstrating growth promotion. Rhodobacter sphaeroides and AMF combination elevated leaf P, Mg, and Cu concentrations, while AMF alone increased Zn, Mn, and B accumulation. Rhodobacter sphaeroides reduced Fe, Zn, Mn, and B soil concentrations, with no corresponding increase in their accumulation in the plant, as observed with mycorrhiza and the combination of microorganisms, hinting at its applicability for saffron cultivation in environments contaminated with heavy metals. In summary, the findings underscore the importance of microorganism supplementation in saffron cultivation, offering insights into optimizing growth conditions.

Background/Objectives: The expansive clay soils of the Puducherry inland region exhibit high plasticity, excessive swelling, and low shear strength, making them unsuitable for direct use in construction without stabilization. Despite the proven effectiveness of lime and quarry dust as soil stabilizers, limited research exists on Puducherry inland clay, especially regarding long-term curing, durability, and the mechanistic interactions between these stabilizers and the clay. This study investigates the effect of lime and quarry dust as stabilizing agents on the geotechnical characteristics of Puducherry inland clay. Methods: Soil samples were treated separately with varying proportions of lime and quarry dust (7%, 14%, 21%, and 28% by dry weight) to assess improvements in geotechnical behaviour. Laboratory tests, including Atterberg limits, Free Swell Index (FSI), compaction characteristics, direct shear test, and Unconfined Compressive Strength (UCS) were conducted to evaluate changes in soil properties. Findings: The plasticity index of lime-stabilized clay decreased by approximately 25%, while quarry dust-stabilized clay showed a decrease of approximately 37%. The optimum moisture content of lime-stabilized clay and quarry dust-stabilized clay decreased by about 20% and 35%, respectively. The maximum dry density of lime- and quarry dust-stabilized clay increased by about 10% and 35%, respectively. Cohesion values for both lime- and quarry dust-stabilized clay were reduced by about 28%. The UCS of lime-stabilized clay showed a significant increase up to 21% additive content, beyond which the strength dropped drastically, whereas quarry dust-stabilized clay exhibited a continuous strength increase even beyond 21% addition. The FSI of lime- and quarry dust-stabilized clay decreased by about 35% and 28%, respectively. Novelty: Utilizing quarry dust for the stabilization of clay improves soil properties, making it suitable for construction. Compared to lime, quarry dust is abundantly available and is usually disposed of in landfills, contributing to environmental pollution. Stabilizing clay with quarry dust offers two key advantages: it enhances the engineering properties of clay and helps mitigate pollution by effectively utilizing a waste material. Keywords: Clay, Soil Stabilization, Cohesion, Lime, Quarry Dust, Geotechnical Properties

Clay Soil as a Sustainable and Low-Cost Adsorbent for Methylene Blue Dye Removal from Contaminated Water

Evolution of multi-element coupling and geochemical behavior in dryland and paddy soils along a 3000-year chronosequence in the Yangtze River floodplain.

Climate change and evolving land management practices are reshaping soil–plant interactions critical for sustainable viticulture. These interactions are driven by soil texture, hydrogeochemical gradients, and climatic conditions, influencing grapevine traits like nutrient and water content. Integrating innovative methods, this study explores the relationship between soil variability and grapevine characteristics in the Médoc wine region, France. The research combines hyperspectral imaging, electromagnetic induction (EMI), and electrical resistivity tomography (ERT) with traditional soil and leaf sampling. Hyperspectral data, using visible-near infrared (VNIR) wavelengths, reliably estimated leaf traits such as nitrogen and water content, yielding strong predictive relationships (R2 up to 0.8). These findings suggest VNIR-based indices are cost-effective for monitoring grapevine physiology. Geophysical data revealed significant soil textural gradients, delineating sand, transitional (loam, sandy loam), and clay textural soil classes. Apparent electrical conductivity (ECa) and inverted electrical conductivity (EC) correlated with soil texture and grapevine traits, particularly at depths around 50 cm, aligning with primary root zones. However, interannual variability in correlations emphasised the influence of weather conditions and phenological stages, highlighting the need to align data acquisition with vine growth phases. The integration of hyperspectral imaging and geophysical methods provides a novel framework for linking soil and plant parameters. This interdisciplinary approach enhances the spatial resolution and scalability of vineyard monitoring, offering actionable insights for precision viticulture. Future work should expand datasets and refine predictive models to improve the understanding of soil–plant dynamics under changing environmental conditions. These findings underscore the potential of combining hyperspectral and geophysical data to develop climate-resilient vineyard management strategies, advancing precision agriculture, and sustainable viticulture practices.

Soil-structure interactions commonly induce displacements, with settlements in weak soils becoming increasingly significant under growing urbanization, making it important to minimize them to prevent structural defects. This study investigated the influence of tunnel-pile configurations on ground settlement during tunnel construction at Zhongshan Road with an undercrossing, using numerical simulation. Prediction functions describing settlement behavior within the model were developed and proposed. The Mohr-Coulomb (MC) model in MIDAS GTS NX was employed to simulate settlement levels of a semicircular tunnel lining and surrounding soil under various pile setups, in order to identify the most effective configuration for ground improvement. Results showed substantial variations in vertical settlement. The designed 5 × 4m pile setup produced the highest crown settlement, increasing it by 32-47% longitudinally along the tunnel compared to the case without piles, while reducing lining uplift by only 138-165%. In contrast, the 4 × 4m pile arrangement performed best overall, reducing uplift by 184-194% and limiting settlement fluctuations to - 12% to - 47%, maintaining values within 5-10mm along the 80m tunnel length. The 4 × 4m pile setup was therefore more reliable and less variable in both settlement and uplift. Uniform pile arrangements provided smoother settlement troughs than non-uniform setups. Furthermore, prediction formulas based on Gaussian functions, using parameters n and k, reliably estimated settlement for greenfield conditions and projected behavior for tunnel undercrossings. The greenfield prediction function was validated against 12 existing projects, with n values within [Formula: see text] prediction and back-calculated settlements closely matching observed settlements.