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The existing models for estimating cation exchange capacity (CEC) from easy‐to‐measure hygroscopic water content (θh) were based on a single water activity (aw) value rather than on the processes that govern soil water vapor adsorption for a distinct aw range. Here, we present a new CEC estimation model based on θh data of 119 soils with different clay mineralogy (i.e., illitic [IL], montmorillonitic [ML], and kaolinitic [KA] samples) and organic carbon (OC) contents for the aw range from 0.23 to 0.57 (Δθ0.23–0.57) and validate its performance. Based on the hypothesis that multilayer adsorption exhibits a higher correlation with CEC than monolayer adsorption and capillary condensation, the aw range from 0.23 to 0.57 was chosen with CEC calculated as CEC = k × Δθ0.23–0.57. The performance of the new model is compared to the Arthur (2017) model and the Torrent (2015) model, which considers a single θh value. The average proportionality coefficient (k) varied with the dominant clay mineralogy of the investigated soils. For soils dominated by 2:1 clay minerals (i.e., IL and ML), the new model showed a good estimation accuracy (Nash‐Sutcliffe model efficiency [E] ≥ 0.85; root mean squared error [RMSE] ≤ 4.18 cmol(+) kg−1). The new model performed better for IL and ML samples than for KA samples, and yielded more accurate CEC estimations than the Arthur model and Torrent model for soils with 2:1 clay minerals. For soil with high OC content (>23.2 g kg−1), the new model slightly underestimated CEC (E = 0.66; RMSE = 5.87). [ABSTRACT FROM AUTHOR]

AbstractResults of previous research on chemigated imazamox for control of branched broomrape (Phelipanche ramosa) in processing tomatoes suggested potential soil-type differences in imazamox availability. Over two years, there were differences in crop-injury between two sites less than 30-km apart: imazamox-treated tomatoes in the Davis location had relatively minor early season injury while tomatoes at the Woodland location were severely injured or killed. The following study was conducted to investigate imazamox sorption in four California soils to determine if differences in herbicide adsorption played a role in variable crop-injury observed in the field trials. To determine the sorption capacity of imazamox of each soil, a batch-equilibrium study was conducted. There were significant differences in sorbed imazamox: the clay soil had the highest adsorption (Robert’s Island: 742.5 pg µL−1 sorbed), followed by the sandy loam soil (Ripon: 723.9 pg µL−1 sorbed), while the loam soils from both trial sites (Davis: 704.2 pg µL−1 sorbed; Woodland: 699.9 pg µL−1 sorbed) had the lowest adsorption and were not significantly different from one another. Results from this study illustrate only minor differences in imazamox adsorption among the soils tested which suggests that soil type was likely not a major factor contributing to differences in crop-injury. [ABSTRACT FROM AUTHOR]

Soil shrinkage characteristic curves are used to describe the shrinkage behavior and hydraulic properties of unsaturated soils. To construct soil shrinkage characteristic curves, a high‐data‐density measurement method is needed that relates water content to soil volume changes. We present a fully automated soil shrinkage measurement setup, based on the simplified evaporation method, to characterize the shrinkage behavior of undisturbed natural expansive clay soils. The high data density creates the opportunity to produce soil shrinkage characteristic curves without the need for a mathematical model. The technique allows for resaturation of the samples after drying, enabling differentiation between reversible and irreversible shrinkage. The setup consists of the commercialized HYPROP2 apparatus combined with optical distance sensors to measure the horizontal and vertical dimensions of the samples, yielding data on the sample volume, weight, and soil water suction. The measurement frequency is once per 10 min, and the measurement period is up to 4 weeks, providing a detailed time series of the drying and shrinkage characteristics. The setup can capture the different shrinkage phases and offers the opportunity to relate the soil shrinkage characteristic curve to soil water suction. The measurement data acquisition rate and accuracy enable detailed interpretation of soil water retention curves for nonrigid soils and are shown to be essential for understanding and quantifying the shrinkage potential of several types of deposits. [ABSTRACT FROM AUTHOR]

Waste materials contribute to a wide range of environmental and economic problems. To minimize their effects, a safe strategy for reducing such negative impact is required. Recycling and reusing waste materials have proved to be effective measures in this respect. In this study, an eco-friendly treatment is investigated based on using waste powdered glass (WGP) and EPS beads (EPSb) as mechanical and chemical admixers in soils. For this purpose, Atterberg limit, standard proctor, free swell, and unconfined compression tests are performed on soil samples with different ratios of waste materials at their optimum moisture contents. The obtained test results indicate that adding WGP to cohesive soils increases the unconfined compressive strength (UCS) and reduces free swell (FS). In contrast, using EPSb reduces both FS and UCS of the treated soil samples. An optimum combination of both waste materials is determined for the improvement of the properties of high plasticity clay used in this study. Furthermore, multiple linear regression (MLR) and artificial neural network (ANN) methods are used to predict the FS and UCS of the clayey soils based on the data obtained here and the experimental test results reported in the literature. Once the FS and UCS values of untreated soil and additive percentages are defined as independent variables, both methods are shown to predict the FS and UCS values of the treated soil samples on a satisfactory level with the coefficient of correlation ( R 2 ) values greater than 0.926. Additionally, when only the index properties (liquid limit, plastic limit, and plasticity index) of the soil samples with waste materials are used as dependent variables, the R 2 values obtained by the ANN method are 0.968 and 0.974 for FS and UCS, respectively. The results of the untreated soil samples' FS and UCS tests are known, and the linear regression and ANN techniques yield similar results. Lastly, the ANN method is used to predict the FS and UCS of the treated samples in accordance to the limited predictors (e.g., only the Atterberg limits of the soil sample). [ABSTRACT FROM AUTHOR]

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, most of the released 137Cs remained in the litter and surface soil of the adjacent forest floor. However, 137Cs absorption by large soil invertebrates near this site has not been estimated. The aim of this study was to understand the role of soil macroinvertebrates in 137Cs uptake from forest litter into forest ecosystems. Breeding experiments were conducted using scarab beetle larvae (Protaetia orientalis). Dissection experiments revealed that 85% of the total 137Cs was concentrated in the digestive tract of larvae, while a low proportion was absorbed into the skin and muscle tissues. The 137Cs absorption rate, indicating the transfer of 137Cs from consumed litter to larval tissue, was low (0.39%). 137Cs concentrations decreased to one-fourth from larva to imago, possibly due to excretion from the digestive tract and during eclosion. In the elimination experiment, biological half-lives were 0.26–0.64 and 0.11–0.47 days and 3.35–48.30 and 4.01–17.70 days for the digestive tract and muscle/skin tissues in the fast and slow components, respectively, corresponding to 137Cs discharge from the gastrointestinal tract and physiological clearance. In the sequential extraction experiment, litter digestion by flower chafer larvae significantly reduced the bioavailable fraction of 137Cs including water-soluble, exchangeable, oxidized, and organic forms, from 23.2% in litter to 17.7% in feces. Residual 137Cs was not reduced by digestion, probably because it was fixed in soil clay. Our study on breeding experiments of the Scarabaeidae beetle confirmed the low bioavailability of 137Cs in the litter in Fukushima. However, litter feeders may play an important role in transferring 137Cs to higher trophic levels in the forest ecosystem by extracting the bioavailable fraction of the vast stock of 137Cs on the forest floor. [ABSTRACT FROM AUTHOR]

Because of the importance of the Central Valley of California, USA, to shorebirds along the Pacific Flyway, conservation investments have been made in the area's agricultural fields and managed wetlands. Increasingly, landowner incentive programs are being used to deliver shorebird habitat, presenting opportunities to answer remaining questions about which implementation strategies and field management practices are most effective at attracting birds. To provide management guidance for these investments, we collected and analyzed 5 years of data (2014–2018) on shorebird abundance in flooded rice fields enrolled in a dynamic habitat incentive program. The program incentivized flooding in fallow and post‐harvest rice fields in seasons when habitat is relatively sparse, specifically the early fall and late spring. Across nearly 9,000 field observations over 5 years, we explored the relationship between abundance and density (birds/ha) of shorebirds and vegetation cover, soil clay, landscape‐level flooding, and local flood timing, duration, and depth. We observed more shorebirds in fields that were approximately 50% flooded, had water depths of 5–10 cm, and had minimal rice straw or stubble cover, with strong or very strong evidence for each of these relationships. We found that the timing of habitat provisioning was important, with moderate evidence that earlier fall flooding and strong evidence that the duration of fall flooding was associated with higher shorebird density. We observed lower shorebird densities in locations with ample flooded rice habitat in surrounding areas, potentially because shorebirds spread out across the landscape. We found very strong evidence that flooding consistency, either at a site that was continually flooded over many months or a site that had been flooded in previous years, was associated with higher shorebird density. Soil clay content was associated with decreased observed shorebird density, potentially through its influence on the ability of shorebirds to forage for invertebrate prey. These results suggest best practices for shorebird habitat creation in agricultural landscapes, providing important information for conservation and population recovery. [ABSTRACT FROM AUTHOR]

Geohelminths (soil-transmitted helminths) tend to thrive in moist soil conditions, and the poor hygiene systems of underdeveloped countries have enhanced their transmission at an alarming rate. A cross-sectional study was conducted to determine the effects of soil type, pH, and temperature on geohelminths found in soil samples from Mkpat Enin LGA, Akwa Ibom State. The soil samples were examined using the centrifugal floatation method for geohelminth eggs and larvae. Among the 200 soil samples examined, an overall prevalence of 67.0% was recorded. Geohelminths recovered were Ascaris lumbricoides, which contaminated 38 (28.36%), Trichuris trichiura 27(20.15 %), hookworms 26(19.40 %), Strongyloides stercoralis 24(17.91 %), and Toxocara canis 19(14.18 %) soil samples. Soil samples obtained from farmlands and toilets had a higher contamination rate (82 %) than those from schools and roadsides (68.0% and 36.0%, respectively). Loamy soil recorded 77(66.38%) contaminated soil samples at a mean temperature of 28.7oC ± 0.1, and pH of 6.9 ± 0.03, compared to sandy soil with 32(69.57 %) at a mean temperature of (27.5oC ± 0.3) and pH of 5.7 ± 0.04, then clayey soil with 25(65.79 %) at a mean temperature of 27.0oC ± 0.1 and pH of 5.3 ± 0.04. There was no significant correlation between the prevalence of each geohelminth and soil type, temperature, or pH. The type of soil, soil temperature within the measured range, and soil alkalinity as measured do not appear to be major factors influencing the overall prevalence of geohelminths. The analysis also showed that these factors do not have a strong influence on the prevalence of individual geohelminth species. The eggs of these geohelminths were more abundant than their larvae. Periodic deworming programmes, health education, and improved sanitation will ultimately reduce the transmission of geohelminths. [ABSTRACT FROM AUTHOR]

Conservation management practices often produced positive but limited desirable outcomes in US Southeast sandy soils, likely due to their intrinsically low clay contents that constrain the soil’s capacity to preserve organic carbon (C) and nutrients. In the field, we tested the effectiveness of a novel approach, that is, clay soil amendment, to improve sandy soils. In October 2017, clay-rich soils (25% clay) were spread at 25 metric tons ha−1 and tilled onto a sandy soil (1.9% clay) in the field, which was further mixed by light tillage at 0- to 15-cm depth, followed by planting winter cover crop mixtures (cereal rye, crimson clover, and winter pea). The crop rotation was cotton and corn with cover crop mixtures planted in the winter fallow season. Soils (0–15 cm) were collected in August 2021 and subjected to physiobiochemical analyses. Clay amendment increased soil clay content to 3.4%, which improved nitrogen (N) availability by 51% but inhibited the activities of C (β-Dcellubiosidase [CB]; β-xylosidase [BX]; N-acetyl-β-glucosaminidase [NAG]) and N (leucine aminopeptidase [LAP]) cycling enzymes, resulting in up to 78% reduction in microbial respiration. A follow-up kinetic study on BG and LAP enzymes suggested that clay addition can have different impacts on enzymes with diverse biological origins through distinct mechanisms. Clay addition can potentially improve sandy soils by stabilizing the organic inputs in soils. However, more research is required to understand its long-term impacts making this approach practical. [ABSTRACT FROM AUTHOR]

The soil mantle of the tropical karstic landscapes of Southern Mexico was shaped by specific processes of pedogenesis and long-term human impacts of ancient Maya agriculture. To understand the interaction between natural and human-induced soilforming processes in the calcareous mountains of Chiapas state, we studied soil toposequences around the Classic Maya site of Budsilhá and related them to the archaeological evidence of settlement and land-use distribution. Soil chemical analysis, micromorphological observations, and clay mineral identification were carried out in key soil profiles at the main geoforms. Limestone hills are occupied by shallow Rendolls which are usually perceived as incipient soils. However, high content of silicate clay composed of kaolinite and vermiculite and ferruginous clayey soil material observed at macro- and microscale backed the hypothesis that these soils were formed from the residues of thick Terra Rossa after their erosion. Swampy lowlands are occupied by thick clayey gleyic soils with clay mineral assemblages similar to those in the upland Rendolls. We suppose that the mineral matrix of the lowland soils is largely derived from the pedosediments of eroded upland Terra Rossa, which lost original ferruginous pigmentation and aggregation due to redoximorphic processes. Some wetland soils contain neoformed gypsum that is atypical for humid tropics; sulfidesulfate transformation under fluctuating redox conditions could promote gypsum synthesis. Ancient Maya land use was closely related to soil-geomorphic conditions: settlements with homegardens occupied calcareous hills, whereas the primary agricultural domain was developed on lowland soils after their drainage by artificial canals. [ABSTRACT FROM AUTHOR]

The calcareous materials used in constructing the Phaya Thon Zu temple at the Bagan historical sites in Myanmar are mortars, plasters, and stuccos. Among them, the mortars and plasters are a mixture of original and new materials used for recent conservation treatments. In this study, the making techniques were examined through analysis of calcareous materials by production period. All calcareous materials have a mineral composition similar to soil, except calcite. Stuccos have the most refined aggregates, homogeneous particle size, and the highest lime and organic contents. They were designed to improve ease of carving and weathering resistance, considering the unique characteristics of the stuccos. Because all calcareous materials were mixed with soil, the origin of the clay materials was analyzed. It was concluded that the mortars were produced by mixing clay and sandy soil, and the original mortars showed characteristics similar to soil. It is highly possible that sandy soil from around the Htillominlo temple was used to produce new plasters, and it is estimated that a mixture of clay soil was used for the original plasters and stuccos. A clear provenance interpretation of the original and raw materials used for each construction and the mixing ratio of clay materials need to be discussed through experiments, along with the estimated provenance area of the raw calcareous materials. [ABSTRACT FROM AUTHOR]

In recent years, individuals have begun to pay more attention to non-traditional stabilizers due to the problems connected with traditional stabilizers. Traditional stabilizers have undergone extensive investigation, and the mechanisms by which they act are well understood. This paper presents findings of the effect of sugarcane vinasse wastewater (VI) and sodium alginate (SA) polymer on the compressibility behavior, and microstructural evolution of clay soil using mixing method. The premise of this paper is to eliminate waste material from nature and compare the performance of this material against the use of polymers that have recently been used in improvement. The additives were dissolved in water and then introduced to the dried stratified soil to produce improved soil samples using the mixing technique. Transported unconfined compressive strength (UCS) was examined for 1, 14, and 28 days of treatments with additive ranges of 3–15% for VI and 0.25–1.25% for SA. In clay with high plasticity, the findings show that VI significantly influences increasing the UCS. With the addition of 9% vinasse to the soil at the age of 28 days, the UCS has increased by 78.8%. Additionally, the introduction of 1.25% SA to the soil has increased by 261.9% for the 28-day treatment efficiency significantly. Microstructural and chemical examination revealed that the mineralogical and morphological contents of the stabilized soil were influenced due to the pozzolanic reaction. The results showed that waste by-product liquid was able to significantly increase the strength and compressibility of the clay soil. Using a large volume of waste by-product liquid to stabilize soil, the researchers discovered a straightforward application method. [ABSTRACT FROM AUTHOR]

This study investigates clayey soil from a road project situated in the district of Lodhran, Punjab, Pakistan. The subgrade prepared with the soil distorted due to heaving after a certain period of its construction. First, laboratory tests were conducted to explore the reason for this problem, examining the fundamental engineering properties of soil. The test results show that the soil acts as a soft material when water content reaches 30%, significantly reducing its strength. The soft soil is generally considered unsuitable for civil work due to its poor performance behaviour. So, the performance of clayey soil was examined in the study at its soft state by coupling it with stronger materials, such as polyethylene polymeric reinforcement and sand, developing laboratory-scale foundation models. Based on the model studies, the study proposes a sustainable polyethylene–sand–soft soil model, which shows 155 and 56% higher ultimate bearing capacity (BC) than soft soil and sand-reinforced soft soil foundations. The changes in BC occur due to the reinforcement action of the polyethylene reinforcement, which is associated with its tensile membrane action effects and interlock bonding at the soil-reinforcement interface. Practically, the study can reduce the dependency of industry practitioners on sand materials. Using polyethylene in civil work is viable for environmental sustainability. [ABSTRACT FROM AUTHOR]

Rainfall-triggered landslides pose a significant threat to both infrastructure and human lives, making it crucial to comprehend the factors that contribute to their occurrence. Specifically, understanding the relationship between these factors and the amount of rain that is necessary for triggering such events is essential for effective prediction and mitigation strategies. To address this issue, our study proposes a statistical modelling approach using machine learning, specifically the Random Forest algorithm, to investigate the connection between landslide predisposing factors and the daily rainfall intensity threshold necessary for the initiation of shallow landslides in Portugal. By leveraging a comprehensive dataset comprising historical landslide events, associated critical rainfall, and ten distinct landslide predisposing factors, we developed several models and used cross-validation technique to evaluate their performance. Our findings demonstrate that the Random Forest model effectively captures a relationship among landslide predisposing factors, critical daily rainfall intensity, and landslide occurrences. The models exhibit a satisfactory accuracy in assessing the spatial variation of critical daily rainfall intensity based on the predisposing factors, with a mean absolute percentage error (MAPE) of around 17%. Furthermore, the models provide valuable insights into the relative importance of various predisposing factors in landslide triggering, highlighting the significance of each factor. It was found that it takes higher rainfall intensity to trigger shallow landslides in the north region of Portugal when considering critical rainfall events of 3 and 13 days. Slope aspect, slope angle, and clay content in the soil are among the main predisposing factors used for defining the spatial variation of the daily rainfall intensity threshold. [ABSTRACT FROM AUTHOR]

Calcium carbide residue (CCR) has been identified as an effective replacement for traditional lime for the stabilization of expansive soils. The shrinkage of expansive clay severely threatens the foundation layers’ long-term stability. The efficacy of CCR stabilization in reducing compressibility and enhancing the strength and stiffness of clay has been widely reported; however, the calcium-based additive stabilized soil tends to lose its engineered integrity under field-exposed seasonal moisture variation, specifically, shrinkage induced by prolonged drying. In this study, the shrinkage characteristic of CCR-treated clay (6%, 9%, and 12%) slurry was investigated by digital image analysis and mercury displacement method to quantify volumetric shrinkage strain. The results were compared with those of 4% and 6% lime-treated clay, which revealed the higher efficacy of CCR in reducing shrinkage strain by 47–57%. A characteristic shrinkage curve that depicted the significant variation of shrinkage phases in CCR-treated clay samples is developed. The dominance of the proportional shrinkage phase is observed in both untreated and treated clay samples. The shrinkage caused by evaporation, hydration, and decalcification is postulated in treated clays. This study is expected to contribute to the understanding of shrinkage mechanisms of CCR-treated clay and assist in the future design of stabilized embankment sections or subgrade for unpaved roads. [ABSTRACT FROM AUTHOR]

Civil engineering projects are always at high risk of failure when constructed on weak or soft soils due to their lower shear strength and settlement issues. This study summarises the influence of various Nano additives such as Nano aluminium oxide, Nano magnesium oxide, Nano copper, Nano clay, Nano carbons and Nano calcium carbonateon the strength, mineralogical and morphological properties of problematic soils as reported by the researchers. The strength properties such as unconfined compressive strength, direct and triaxial shear strength, and California bearing strength were enhanced with the incorporation of Nano additives up to the optimum amount of dosage in the soil. The very low amount of dosage of Nano additives provided a dramatic change in the strength due to their higher specific surface area as compared to the traditional additives such as cement and lime. The mineralogical and morphological studies showed denser and stiffer soil matrices and depict the formation of new cementitious compounds. From the detailed review of past literature, it can be concluded that the inclusion of a small amount of Nano additives in soil is capable of some shadowing the negative effect of problematic soil for construction purposes. [ABSTRACT FROM AUTHOR]

Contamination of soil threatens the environment and can have a negative effect on soil strength parameters. Soil stabilization is one way to address this issue. In the present study, metakaolin geopolymer was used to stabilize contaminated clay. Initially, the effects of the concentration on the soil parameters was investigated. A combination of lead nitrate and zinc nitrate at a 1:1 ratio was used to contaminate the soil by introducing 1000, 5000 and 10,000 ppm of contaminants. The samples were subjected to a 7-day curing period after which the Atterberg limits, compaction, unconfined compressive strength (UCS), California bearing ratio (CBR) and pH tests were conducted. The results showed that the addition of 10,000 ppm of contaminant to the base soil decreased the CBR, UCS and pH by 21.07%, 23.37% and 15.51%, respectively. The most critical contaminant concentration was found to be 10,000 ppm. Next, soil samples contaminated with 10,000 ppm of lead and zinc nitrates was stabilized with 5%, 10% and 15% metakaolin geopolymer at curing times of 7, 14 and 28 days. After stabilization, the tests initially conducted on the contaminated samples without stabilizer were performed on samples stabilized with metakaolin geopolymer. The outcomes revealed that the soil strength parameters increased significantly with increases in the metakaolin geopolymer content and curing time. An increase in the curing time was shown to increase the UCS. The findings demonstrated that, after 28 days of curing, the soil pH of the stabilized samples with 5%, 10% and 15% metakaolin geopolymer increased by approximately 43.4%, 49.2% and 50.65%, respectively, in comparison with the soil containing 10,000 ppm of contaminants without stabilizer. [ABSTRACT FROM AUTHOR]

Soil aggregate functions in maintaining soil structure and protecting soil organic carbon (SOC). To illustrate the influence of land use change on soil aggregate total SOC and aggregate-associated SOC, we conducted a meta-analysis using data from published journals. Overall, land use changes significantly improved soil macro-aggregate and total SOC by 7.3% and 19.8%, respectively, compared with the primary land use type. The WSA0.25 tended to increase by 63.8% and 37.9% in forest and grassland, respectively, while it decreased by 21.9% and 11.2% in farmland and garden, compared to primary land use. The change from ecological land to agricultural land significantly decreased WSA0.25 by an average of 24.3%, but agricultural land change to ecological land increased WSA0.25 by 49.2%. Soil clay, SOC, bulk density, and pH were the most important factors in explaining the variance in macro-aggregate content. The SOC content increased by 44.1% and 74.4% in forest and grassland, respectively, while it decreased by 16.2% in farmland. Changing agricultural land to ecological land increased the SOC and macro-aggregate associated SOC by 52.6% and 50.0%, respectively, and a positive correction was observed between macro-aggregate associated SOC and the content of WSA0.25 rather than MSA0.25. Our meta-analysis provided a scientific basis to enhance soil structural stability and increase SOC storage. [ABSTRACT FROM AUTHOR]

Use of helical piles has become increasingly popular since last few decades for numerous advantages and installation convenience. They may consist of isolated helical plate welded to a central shaft or continuous screw type piles. The load transfer mechanism of helical piles is complex compared to the conventional vertical driven piles. Although limited contributions are available on the performance of helical piles including theoretical and experimental studies, still there are major scopes for further research. The authors have conducted a series of laboratory experimentations on axial load-settlement characteristics of model helical piles made of high tension steel in soft clayey soil, followed by 3D finite element analysis using ABAQUS. The numerical results were found to be close to the experimental observations. Using the numerical model, extensive parametric studies were conducted. The load-settlement response was found to be mostly logarithmic. The pile capacity was found to be influenced significantly by the pitch and embedded pile length. The FEM analysis revealed maximum plastic strain and displacement to develop adjacent to the pile-tip and the interface, while negligible at the boundaries. The interface shear stress distributions are also studied. From the entire investigation, a set of important conclusions are drawn. [ABSTRACT FROM AUTHOR]

Establishing a strength model for cement-stabilized clayey soils is crucial to the design and construction of cement-reinforced foundation projects. Numerous studies have used the parameters to establish the strength model, but the selection of the key characterization parameters that determine the strength development remains challenging. Therefore, more studies and indoor tests are required to verify the parameters. This study designs cement-stabilized pure clay particles (i.e., kaolin) with various characterization parameters and conducts a series of unconfined compressive strength tests. Using the results from the strength tests to clarify the influence mechanism for the characterization parameters, the strongly correlated characterization parameters were identified with correlation analysis, and these parameters were used to establish a multilinear regression model for strength. The experimental results showed that Pearson's correlation analysis could effectively identify the relationship between the characterization parameters of the soil particles, water, and cement, and the strength of cement-stabilized clayey soils at different curing times and their correlation intensity. The multilinear regression-based strength model was determined based on a strong Pearson's correlation. The predicted value is similar to the measured value, with a correlation coefficient of 0.985, a mean absolute error (MAE) of 163.80 kPa, and the predicted root mean square error (RMSE) of 225.99 kPa. This study's findings could provide theoretical support for the strength design and performance prediction of cement-stabilized clayey soils. [ABSTRACT FROM AUTHOR]

Dissolved organic carbon (DOC) is the most active carbon pool in soils, which plays critical roles in soil carbon cycling, plant productivity, and global climate change. An accurate assessment of the quantity of DOC in the soil is essential for the detailed elucidation of ecosystem functions and services. Nevertheless, the global driving factors and distribution of soil DOC remain inadequately quantified due to the scarcity of large-scale data. Here, a comprehensive global database of 12807 soil DOC concentrations derived from 975 target papers in the literature was compiled. Detailed geographic locations, climate, and soil properties were also recorded as predictors of soil DOC. Machine learning techniques were employed to assess the relative importance of various predictors in the determination of soil DOC concentrations, which were subsequently extended for their prediction on a global scale. The worldwide soil DOC concentration spanned a wide range (0.04 to 7859 mg kg-1), averaging 222.78 mg kg-1. The 12 selected variables (including soil properties, month, climate, and ecosystem) explained 65 % of the variance in soil DOC concentrations. Elevation, soil clay, and soil organic carbon were three of the most important predictors. Global soil DOC concentration increased from the equator to the poles. The soil DOC stocks in the topsoil layer (0–30 cm) amounted to 12.17 Pg, with significant variations observed across different continents. These results are instrumental for informing strategies on soil management practices, ecosystem services, and the mitigation of climate change. Furthermore, our database can be combined with other carbon pools to explore the total soil carbon turnover and constrain Earth carbon models. The dataset is publicly available at https://doi.org/10.6084/m9.figshare.26379898 (Ren and Cai, 2024). [ABSTRACT FROM AUTHOR]

Wildfires are hazards of increasing significance in recent decades. Our ability to forecast the evolution of fire regimes is inhibited by the lack of records of key fire parameters such as fire severity. Boron isotopes in the soil clay fraction have been shown to vary with fire severity, where increased δ 11B coincides with higher fire severity. To elucidate the relationship between the B isotope composition of soil clays and fire events, we performed adsorption experiments by reacting rainwater with combusted leaves to analyse how B isotopes are fractionated during processes leading to the imparting of boron from plants to clay minerals in soil during and following combustion. We find that < 5% of B is volatilised during combustion of leaves and barks, where 11B is preferentially volatilised. No isotopic fractionation was detected during the leaching of leaves ash with rainwater, possibly due to the large water:clay ratio in our experiments. Adsorption of B from leaching solutions onto clay minerals shows isotopic fractionation, and hysteresis of the adsorbed B fraction. For experiments at pH between 7 and 9, the isotope fractionation between adsorbed and dissolved B (Δ 11B adsorbed-dissolved) ranges from −8.8 to −14.5 ‰ , indicating preferential adsorption of 10B onto clays compared to 11B. For experiments at pH > 10, the Δ 11B adsorbed-dissolved values range from +11.2 to +19.4 ‰ , indicating a preferential adsorption of 11B over 10B. Irregardless of pH, clay fractions in all experiments show increases in δ 11B, as the leaching solutions have high δ 11B relative to the soil clay minerals prior to their interaction. Ash of leaves combusted at 550 °C (highest temperature in our experiments) induce the greatest increase in solution pH and δ 11B in clays. Our experiments suggests that the higher B isotope composition of clays following a high severity fire is likely imparted by solutions that leach isotopically heavy B from the combusted canopy. [ABSTRACT FROM AUTHOR]

Underground soil in coastal areas is often affected by various dynamic effects such as earthquakes, construction, and waves. In order to study the influence of stress path on the dynamic characteristics of silty clay, resonance column tests were conducted on undisturbed samples of silty clay at different depths in the Yancheng area under cyclic stress paths. The results show that stress history has a significant impact on the response of soil dynamic parameters, and there is a significant difference between the maximum dynamic shear modulus Gmax and dynamic shear modulus G of the soil between loading and unloading paths; When the confining pressure is between 0~80 kPa, Gmax rapidly increases and variability decreases; The geological age and burial depth play an important role in the variation of soil dynamic parameters. As the burial depth increases, the difference between Gmax under different stress paths and G when the confining pressure changes continuously expands. When the geological age changes, G shows a significant increase; Propose a fitting relationship between the maximum dynamic shear modulus and confining pressure based on experiments, and provide fitting results for silty clay with different stress histories, providing reference for engineering design and construction in Yancheng and related coastal areas. [ABSTRACT FROM AUTHOR]

Soils play a central role in ecosystem functioning, and thus, mapped soil property information is indispensable to supporting sustainable land management. Digital Soil Mapping (DSM) provides a framework to spatially estimate soil properties. However, broad-scale DSM remains challenging because of non-purposively sampled soil data, large data volumes for processing extensive soil covariates, and high model complexities due to spatially varying soil–landscape relationships. This study presents a three-dimensional DSM framework for Switzerland, targeting the soil properties of clay content (Clay), organic carbon content (SOC), pH value (pH), and potential cation exchange capacity (CECpot). The DSM approach is based on machine learning and a comprehensive exploitation of soil and remote sensing data archives. Quantile Regression Forest was applied to link the soil sample data from a national soil data base with covariates derived from a LiDAR-based elevation model, from climate raster data, and from multispectral raster time series based on satellite imagery. The covariate set comprises spatially multiscale terrain attributes, climate patterns and their temporal variation, temporarily multiscale land use features, and spectral bare soil signatures. Soil data and predictions were evaluated with respect to different landcovers and depth intervals. All reference soil data sets were found to be spatially clustered towards croplands, showing an increasing sample density from lower to upper depth intervals. According to the R2 value derived from independent data, the overall model accuracy amounts to 0.69 for Clay, 0.64 for SOC, 0.76 for pH, and 0.72 for CECpot. Reduced model accuracies were found to be accompanied by soil data sets showing limited sample sizes (e.g., CECpot), uneven statistical distributions (e.g., SOC), and low spatial sample densities (e.g., woodland subsoils). Multiscale terrain covariates were highly influential for all models; climate covariates were particularly important for the Clay model; multiscale land use covariates showed enhanced importance for modeling pH; and bare soil reflectance was a major driver in the SOC and CECpot models. [ABSTRACT FROM AUTHOR]

Coix lacryma-jobi L., an annual or perennial plant belonging to the Poaceae family, has long been cultivated as a food and medicine plant in China. In recent years, coix cultivation for high yields and good quality has become a research hotspot in Southwest China. Soil optimization is essential for improving crop growth. To ensure the robust establishment of coix plants, eight soil substrates, prepared from three typical soils, i.e., red clay soil, peat soil, and sandy soil, were used to cultivate two local coix varieties (Pu coix from Fujian Province, China; Qi coix from Hebei Province, China), and the plant growth and root coixol content of the two coix varieties were investigated. It was found that coix plants could maintain growth when cultivated with peat soil or sandy soil, but red clay soil was unfavorable for coix growth. The mixtures of sandy soils and peat soils resulted in synergistic benefits for coix growth and root coixol levels over the effects of sandy soil or peat soil alone. In conclusion, the mixtures of sandy soils and peat soils with appropriate proportions (sandy soils/peat soils = 2:1) were suggested as an ideal soil substrate for coix cultivation. The results provide valuable guidance for the establishment of coix plants, which could contribute to high yields and good quality in coix cultivation. [ABSTRACT FROM AUTHOR]

This study focuses on the use of alkali-activated materials and geopolymer grouts in deep soilmixing. Three types of grouts, incorporating metakaolin and/or slag and activated with sodium silicate solution, were characterized at different scales to understand the development of their local structure and macroscopic properties. The performance of the soilmix was assessed by using combinations of the grouts and model soils with different clay contents. Feret's approach was used to understand the development of compressive strength at different water-to-solid ratios ranging from 0.65 to 1. The results suggested that incorporating calcium reduced the water sensitivity of the materials, which is crucial in soilmixing. Adding soils to grouts resulted in improved mechanical properties, due to the influence of the granular skeleton. Based on strength results, binary soilmix mixtures containing 75% of metakaolin and 25% of slag, with H2O/Na2O ratios ranging from 28 to 42 demonstrated potential use for soilmixing due to the synergistic reactivity of metakaolin and slag. The optimization of compositions is necessary for achieving the desired properties of soil mixtures with higher H2O/Na2O ratios. [ABSTRACT FROM AUTHOR]

In Highway Embankments (HE) constructed on Expansive Yazoo Clay Soil (EYCS), in situ moisture and matric suction variations are environmentally driven variables that can significantly impact the safety of the constructed slope. The collected moisture content and suction data are localized and have low spatial resolution on embankments with point borehole monitoring systems with sensor instrumentation. On the other hand, Electrical Resistivity Imaging (ERI) allows high spatial resolution monitoring and is a proven method of mapping the subsurface geologic setting. Multiple studies have proven a correlation between resistivity and soil moisture. The comparison between resistivity and matric suction, on the other hand, has been rarely attempted, much less for EYCS through field-based investigation. The objective of the current study is to compare the field-sensor-based matric suction and soil moisture data with resistivity data. This localized comparison informed the capability of the ERI data to extrapolate the moisture content and suction parameters globally or to other areas of the slope where the instrumentation isn't available. Comparing ERI, matric suction, and volumetric soil moisture content is critical to embankments reliable predictive models. This study's findings can improve performance monitoring requirements for susceptible HE. [ABSTRACT FROM AUTHOR]

Soil improvement is a significant aspect of geotechnical engineering that requires periodic assessment and modification. This study aims to see how glass powder (GP) and rubber particles (RP) affect the shear strength and bearing capacity of clay soil collectively and separately. The soil samples were subjected to direct shear testing and California Bearing Ratio (CBR) tests at various glass powder and rubber particle contents. The CBR test was conducted under soaked and unsoaked conditions. Clay-rubber, clay-glass powder, and clay-rubber-glass powder mixtures were prepared for the tests. It was discovered that adding glass powder and rubber particles improved the soil's shear strength parameters and bearing capacity. A comparative analysis was conducted on the clay-rubber mixtures and clay-glass powder mixtures. The results indicated much improvement by the rubber particles than the waste glass powder in the direct shear test. In contrast, the glass powder had a better impact than the rubber particles in the CBR test. Furthermore, a correlation analysis was conducted to ascertain the relationship between the CBR values and the shear strength of the soil samples using a single Linear Regression Analysis (SRLA) model. The correlation yielded satisfactory coefficients (R2), indicating a strong link between the engineering properties. [ABSTRACT FROM AUTHOR]

Populus euphratica, Tamarix ramosissima, and Sophora alopecuroides are, respectively, typical arboreal, shrubby, and herbaceous species in oases of arid regions. It is important to study the difference in metabolic characteristics of the rhizosphere fungal community of these plant species and their relationships with soil factors for the preservation of delicate arid oasis ecosystems with future environmental changes. In this study, we, respectively, collected 18 rhizosphere soil samples of P. euphratica, T. ramosissima, and S. alopecuroides to explore the difference in rhizosphere fungal metabolic characteristics of different plant life forms and their underlying driving factors. The results showed that (1) soil physicochemical properties (including soil water content, pH, etc.) were significantly different among different plant species (p < 0.05). (2) Rhizosphere fungal metabolic characteristics were significantly different between S. alopecuroides and T. ramosissima (ANOSIM, p < 0.05), which was mainly caused by the different utilization of carboxylic carbon. (3) The RDA showed that the main driving factors of the variations in rhizosphere fungal metabolic characteristics were different among different plant species. The main explanatory variables of the variations in the metabolic characteristics of the rhizosphere fungal community were carbon to nitrogen ratio (23%) and available potassium (17.4%) for P. euphratica, while soil organic carbon (23.1%), pH (8.6%), and total nitrogen (8.2%) for T. ramosissima, and soil clay content (36.6%) and soil organic carbon (12.6%) for S. alopecuroides. In conclusion, the variations in rhizosphere fungal metabolic characteristics in arid oases are dominantly affected by soil factors rather than plant life forms. [ABSTRACT FROM AUTHOR]

Rapid urbanization has caused numerous construction solid waste landfills. Few studies have explored the impact of multi-source waste soils with remarkable spatial variability on the reliability of landfills. This study aims to characterize the site-specific spatial variability of stockpiled waste soils and perform a probabilistic stability assessment of a real-world landfill slope. An integrated probabilistic landfill analysis framework is developed, consisting of spatial variability characterization, random field modeling, and probabilistic slope stability analysis. Seventy-four groups of clayey waste soil parameters were obtained from a landfill in Hangzhou, China. The artificial mixing behavior makes the shear strengths of waste soils have high variability (coefficients of variation close to 0.5), a high positive cross-correlation (about 0.9), and bimodal marginal probability distributions. The spatial variabilities of the cohesion and friction angle of clayey waste soils are similar, with vertical and horizontal scales of fluctuation being 3.23 m and 34.32 m, respectively. The conditional random field modeling of clayey waste soils provides a more realistic slope stability assessment of the landfill and its impact on the failure probability highly relies on the strength and location of boreholes. More slope reinforcement measures should be adopted for safety management of the next stage of landfilling. [ABSTRACT FROM AUTHOR]

Clay swell potential can be classified based on the value of activity and it is defined as the ratio of plasticity index to clay content as a percentage. This paper outlines the investigation into how activity correlates with other key properties of clayey soils. Specifically, four approaches were evaluated for predicting activity using: (a) liquid limit (LL), specific surface area (SSA), cation exchange capacity (CEC) and clay content; (b) LL, SSA and CEC; (c) LL; and (d) SSA and CEC. For this purpose, a database of 104 samples was collected from which 35 machine learning algorithms were trained. Gradient Boosting Trees showed the highest prediction accuracy in the four approaches and, to improve its prediction performance, a Bayesian Optimization was applied to tune theirs hyperparameters, resulting in the final models. The performance of the developed models was evaluated, showing prominent results with exceptionally good metrics, except in the approach from SSA and CEC where the trained algorithm was not capable of predicting activity with confidence (R2=0.46). This algorithm can predict activity using only LL with high accuracy (R2=0.94), and when combined with SSA and CEC, the precision is further enhanced (R2=0.96). [ABSTRACT FROM AUTHOR]

Slag nikel is a by-product of nickel ore smelting through the pyrometallurgical process, which contains silica (> 50 %). This suggests that nickel slag, possessing pozzolanic properties, which potentially to be used as a binding material in construction projects dealing with low soil bearing capacity, such as soil improvement for road foundation. Pozzolanic reactions are greatly influenced by the chemical bonds formed between the binding material and the soil, causing mechanical characteristic changes in the soil. This study aims to examine the effect of adding nickel slag to soft soil based on changes in its physical, mechanical and chemical properties. Physical and mechanical property tests were conducted according to ASTM standards, while the changes in chemical structure in the soil were analyzed based on X-Ray Diffraction (XRD) test results. In this study, nickel slag percentages of 3, 6, 9 and 12 % were used based on the weight ratio of clay soil, at optimum water content (wopt). Furthermore, the test specimens were cured for 14, 28 and 56 days to observe the effect of time on the increase of crystal phases in each variation. The results showed that the presence of nickel slag in the soil can affect its physical and mechanical properties. The nickel slag content in the soil of 3, 6, 9 and 12 % reduces the plasticity index by 16.69, 12.02, 8.86 and 6.38 %, respectively. Meanwhile, the density values increased by 10.97, 11.27, 11.68 and 12.01 kN/m³, respectively. The changes in physical and mechanical properties can be explained by the XRD analysis results, showing changes in the spectrum curve and peak intensity of X-Ray Diffraction in the soil with the addition of nickel slag. This explanation clarifies the transformation of the soil's atomic structure from an amorphous state to a crystalline form, which is stabilized by nickel slag. [ABSTRACT FROM AUTHOR]

New soil organic carbon (SOC) formation in cropland from straw/stover or manure input is a vital source of SOC for climate change mitigation. However, location and variations in the efficiency, specifically the ratio of new SOC formation to organic C input (NCE), remain unquantified globally. In this study, the spatial variability of cropland NCE from straw/stover or manure input and explanatory factors were determined by analyzing 897 pairs of long‐term field measurements from 404 globally distributed sites and by mapping grid‐level cropland NCEs. The global NCE for paddy and upland averaged 13.8% (8.7%–25.1%, 5th–95th percentile) and 10.9% (6.8%–17.3%), respectively. The initial SOC and the clay content of soil, rather than temperature, were the most important factors regulating NCE. A parabola with an apex at approximately 17 g kg−1 between the initial SOC and NCE was resolved, and a positive correlation between soil clay content and NCE was observed. High‐resolution mapping of the global NCE derived from manure/straw and insight into NCE dynamics provide a benchmark for diagnosing cropland soil C dynamics under climate change and identifying priority regions and actions for C management. [ABSTRACT FROM AUTHOR]

Soil mineralogy and texture are directly related to soil carbon due to the physical properties of the clay surface. Traditional techniques for quantifying carbon in soil are time-consuming and expensive, making large-scale quantification for mapping unfeasible. The alternative is the use of soil sensors, such as diffuse reflectance spectroscopy (DRS), an economical, fast, and accurate technique for predicting carbon stocks. In this sense, this study aimed to (a) investigate the relationship of C with different soil mineralogical, chemical, and physical attributes for different geological and geomorphological compartments; (b) understand which spectral bands are most important for estimating C content; (c) estimate C content from diffuse reflectance spectroscopy using different mathematical techniques and indicate which one is the best for tropical soil conditions; and (d) map C contents in detail. The study area was the Western Plateau of São Paulo (WPSP), which covers approximately 13 million hectares (~ 48% of the State of São Paulo, Brazil). A total of 265 samples were collected in this area. The attributes clay, silt, sand, crystalline and non-crystalline iron, base saturation, soil density, total pore volume, total C, C stock, kaolinite/(kaolinite + gibbsite) and hematite/(hematite + goethite), hematite and goethite contents, and spectral curves were evaluated. The spectra were recorded at 0.5-nm intervals, with an integration time of 2.43 nm s−1 over the 350 to 2500-nm range (350–800 nm—visible—VIS and 801–2500 nm—near-infrared—NIR). The data were subjected to descriptive statistics, Spearman correlation, stepwise analysis, and cluster grouping for characterization purposes; partial least squares regression (PLSR) and random forest (RF) for estimation purposes; and geostatistics analysis for creation of spatial maps. Our results indicate that the highest C contents are associated with more clayey soils, oxidic mineralogy, higher total pore volume, and lower soil density in highly dissected basalt compartments. The random forest algorithm associated with the Vis–NIR spectral range is more efficient for estimating and mapping C contents. This suggests that integrating diffuse reflectance spectroscopy with machine learning techniques holds promise for shaping public policies related to land use, mitigating CO2 emissions, and facilitating the implementation of carbon credit policies in a rapid and economically efficient manner. [ABSTRACT FROM AUTHOR]

Soil degradation, marked by declining organic matter, threatens global food security. The impact of brewer's spent yeast (BSY) on clay and sand was analysed at varying application rates to assess its effectiveness in improving soil quality. A randomized complete block design with three replicates was employed. One kilogram of soil were mixed with BSY at application rates of 2 t/ha and 5 t/ha. The samples were incubated at 26 °C for 5 months with daily watering. We analysed pH, total nitrogen, organic carbon, total phosphorus, and electrical conductivity (EC); microbial activity (total heterotrophic bacteria, actinobacteria, and fungi) and soil enzyme activity (dehydrogenase, catalase, protease). BSY application improved soil quality, particularly in clay. Clay showed increased in pH, EC, N and C. BSY significantly boosted microbial populations (bacteria, fungi) in clay with a lesser effect in sand. Enzyme activity and a fertility index also improved in BSY-treated clay, while sand displayed increased activity of a different enzyme. Results suggest BSY holds promise as an organic fertilizer, especially for clay soils. Further research is needed to optimize application, understand long-term effects, and evaluate economic feasibility and social acceptance. This study contributes to the search for sustainable, local solutions to improve soil health and agricultural practices. [ABSTRACT FROM AUTHOR]

This work focuses on archaeological analogues as a way of obtaining long‐term data for assessing the lifetime of a spent nuclear fuel canister. An analysis of the environment around the excavated artefacts is presented, followed by geochemical modelling of the likely corrosion products and subsequent comparison with real phases in the corrosion layer estimated by X‐ray diffraction. A total of 16 archaeological sites with fine clay soils and the potential for long‐term flooding were evaluated. Although the soil pore solution contained high levels of silicates, no such phases with iron in the corrosion products were confirmed. Carbonate corrosion products, typical of bentonite environments, were also not observed. Although oxygen access is very limited in the environments of all sites, even low concentrations shifted the equilibrium of corrosion products formed in favour of (hydroxy)oxides. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the straw to decrease the bulk density of sandy clay loam and clay soils and to determine the effect of this on the development of soybean and maize plants. The soils were compacted using Proctor test with different amounts of crushed straw on the soil surface corresponding to 0, 3, 6, 9 and 12 t ha−1. After this, the soils in pots were compacted with same levels of straw on its surface using the maximum bulk density each soil. Then, soybean and maize were sown and after 42 days, biometric characteristics and physiological parameters were evaluated. The results showed that the maximum bulk density and critical soil moisture for the sandy clay loam soil were 1.51 t m−3 and 0.15 kg kg−1, respectively, while those for the clay soil were 1.54 t m−3 and 0.19 kg kg−1. The straw reduced soil compaction for the two soils, resulting in lower soil bulk density with 9 and 8 t ha−1 of straw on the surface of sandy clay loam and clay soils, respectively. When evaluated the plant, the amounts 6 to 9 t ha−1 of straw promoted better initial development of soybean and maize plants. Thus, this study suggests that a minimum of 6 and 8 t ha−1 of straw be used on the surface of sandy clay loam and clay soils, respectively were efficient in promoting physical soil improvements and better plant development. [ABSTRACT FROM AUTHOR]

Biopolymers are polymers of natural origin and are environmentally friendly, carbon neutral and less energy-intense additives that can be used for various geotechnical applications. Biopolymers like xanthan gum, carrageenan, chitosan, agar, gellan gum and gelatin have shown potential for improving subgrade strength, erosion resistance, and as canal liners and in slope stabilization. But minimal research has been carried out on cellulose-based biopolymers, particularly microcrystalline cellulose (MCC), for their application in geotechnical and geo-environmental engineering. In this study, the effect of MCC on select geotechnical properties of kaolin, a weak, highly compressible clay soil, like its liquid and plastic limits, compaction behavior, deformation behavior, unconfined compression strength (UCS) and aging, was investigated. MCC was used in dosages of 0.5, 1.0, 1.5 and 2% of the dry weight of the soil, and the dry mixing method was adopted for sample preparation. The results show that the liquid limit increased marginally by 11% but the plasticity index was nearly 74% higher than that of untreated kaolin. MCC rendered the treated soil stiffer, which is reflected in the deformation modulus, which increased with both dosage and age of the treated sample. The UCS of kaolin increased with dosage and curing period. The maximum UCS was observed for a dosage of 2% MCC at a 90-day curing period. The increase in stiffness and strength of the treated kaolin with aging points out that MCC can be a potential soil stabilizer. [ABSTRACT FROM AUTHOR]

AbstractThe significance of zinc and iron in crop production, particularly in rice-wheat cropping systems, has been increasingly recognized. The present study aimed to determine the effect of different soil samples collected from the rice-wheat cropping system of Haryana with different soil texture on rice grain yield and micronutrient content using a greenhouse trial with four levels of Fe (0, 25, 50 mg kg−1 as soil and 0.5% foliar spray of FeSO4 at 45 DAS) and four levels of Zn (0, 5, 10 mg kg−1 as soil and 0.5% foliar spray of ZnSO4 at 35 DAS). This study discovered that rice grain yield showed a positive correlation with soil Zn and Fe concentrations in soil before sowing and a negative correlation with soil Fe and Zn concentrations in soil after crop harvesting. In most of the soils studied, foliar spray alone Fe @ 0.5% foliar (45 DAS) and Zn @ 0.5% foliar (35 DAS) improved Fe and Zn concentrations in rice significantly more than soil application of 25 mg Fe kg−1 and 5 mg Zn kg−1, respectively. The rice grain yield in clay soil was 14-42% higher than in sandy soil with different doses of Zn and Fe application. The order of preponderance of different Fe and Zn fractions were CA-Fe < OM-Fe < EX-Fe < FeMnOX-Fe < Res-Fe and Res-Zn > FeMnOX-Zn > OM-Zn > CA-Zn > Ex-Zn in the soils, respectively. Conclusively, concomitant consideration of grain yield and grain Zn and Fe concentrations of rice are the sustainable approach toward food targets achievement. [ABSTRACT FROM AUTHOR]

The electro‐osmosis approach efficiently facilitates the rapid dewatering of soil with high water content and contributes to reducing contaminant levels within the clay soil. However, the changes of chemical field caused by ion transport in the clay soil during electro‐osmosis process will also influence the clay soil consolidation effect. Existing theories predominantly tend to disregard this crucial physical process and its resultant effects, thereby restraining a comprehensive analysis of electro‐osmosis consolidation (EOC) behavior under intricate chemical conditions. This study introduces a concise model of EOC and ion transport considering chemical osmosis. The model considers the nonlinear variation of clay soil parameters such as compressibility, permeability, and effective diffusion coefficients, along with the interaction between EOC and ion transport. Meanwhile, the correctness of the model is verified from different aspects such as theoretical derivation and model comparison. Based on the proposed model, the impacts of the variation in electrical field intensity and chemical concentration on the coupled behaviors between EOC and ion transport are systematically investigated, with and without incorporating nonlinear consolidation characteristics. The results show that diffusion and electro‐migration exhibit a more pronounced effect on ion transport during EOC. Simultaneously, with the increase of ion concentration in clay soil pore solution, the effects of chemical osmosis become increasingly apparent, thereby enhancing clay soil settlement. [ABSTRACT FROM AUTHOR]

Although many commercial stabilizers are available for the treatment of poor soils; agricultural, agro-industrial, and environmentally friendly stabilizers are always encouraged. In this study, an attempt has been made to assess the effects of brewery spent grain ash (BSGA) on lime-treated clay for stabilization of an expansive clay to be used as road construction material. Brewery spent grain (BSG) is an agro-industrial solid waste product obtained during the brewing of beer. Through burning in an open cylinder, it is converted to BSGA. The clay was subjected to preliminary tests to classify and identify some required engineering properties of the sample. Initially, samples were thoroughly mixed with lime by weight of clay to determine the optimum amount of lime needed throughout the experiments. Through laboratory execution trials, 10% lime was determined to be the optimal amount. Following, BSGA was added to the treated clay, which was previously treated with 10% lime, at various percentages of 2, 4, 6, 8, and 10% BSGA by weight of clay. At 0% BSGA, the unsoaked and soaked California bearing ratio (CBR) rose from 13.56 and 8.24% to their greatest values of 14.99% and 9.3%, respectively, at 6% BSGA. Unconfined compressive strength (UCS) values rose from 112.63 kN/m2 at 0% BSGA to 130.31 kN/m2 at 6% BSGA, which is the highest value. Therefore, it was discovered that BSGA can be a beneficial addition to lime stabilization in clay soil. [ABSTRACT FROM AUTHOR]

Understanding the factors affecting the total amount and distribution of soil organic carbon (OC) across different functional carbon pools is important to better define the future management of soil OC stocks. The interactions between soil management practices, local physicochemical soil properties and climate are essential for determining the OC content of the soil. Nevertheless, how these factors affect the total amount of OC and its distribution across carbon pools, i.e., more labile particulate (POC) and more stable mineral‐associated (MAOC) organic carbon, is only partly known. In this study, we assessed topsoil (0–20 cm) samples from 93 arable farms in the southern half of Finland to determine the total amount of OC, and its distribution in MAOC and POC, along with relevant soil properties (amount of clay and silt, aluminium and iron oxides and pH), climate (precipitation and temperature) and fertilization (mineral versus organic). The fertilization did not affect the total soil carbon content (12–58 g OC kg−1 soil). The share of OC in the MAOC fraction (on average 86% of total OC) was relatively stable across the large range of OC contents and clay contents (2%–68%). We assessed the highest feasible MAOC of the soils with boundary line analyses and their OC saturation state with Hassink's equation (Hassink, 1997). Only soils with the lowest clay content (<10% clay) were assumed to be carbon‐saturated, suggesting that most of the studied soils have a capacity to accrue more MAOC. Simple linear regression showed that clay, aluminium and iron oxides explained 9%, 21% and 22% of the variation in MAOC, respectively. Multiple regression analyses including the amount of clay, clay+silt, aluminium and iron oxides, pH, type of fertilization, precipitation and temperature as explanatory variables explained 33%–53% of the variation in OC and MAOC. In all soils, aluminium oxides were important explanatory variable for MAOC, whereas Fe oxides were significant only in soils with higher clay content (>30%). In soils with a low clay content (<30%), pH had added value in explaining MAOC. Altogether, it seems that various climatic, edaphic and soil management‐related factors are context‐dependently controlling OC and that soil textural information alone is not necessarily an adequate predictor to assess the MAOC saturation state of the soil. [ABSTRACT FROM AUTHOR]

The present study examined how the use of soil color can help build and evaluate clay content prediction models from laboratory visible and near infrared spectroscopic data. This study was based on a regional database containing 449 soil samples collected over Karnataka state in India, which has been divided into red soils (240 samples) and black soils (209 samples) based on their Munsell soil color. Partial least squares regression models were calibrated and validated from both the regional datasets and subsets stratified as red and black soils. In addition, a random forest model was used to classify the validation soil samples into black and red classes to evaluate models' performance. First, while the clay content predicted by the regression model built from regional data was evaluated as correct at regional scale (R2val of 0.75), this model was evaluated as more accurate over black (R2val of 0.8) than red (R2val of 0.63) soil samples. Second, the regression models built from subsets stratified per soil color provided different performances than the regression model built from the regional data, both at the regional scale and soil color scale. In conclusion, this study demonstrated that (1) predictions are highly dependent on calibration data, (2) the interpretation of prediction performances relies heavily on validation data, and (3) pedological knowledge, such as soil color, can be effectively employed as an encouraging covariate in both the construction and evaluation of regression models. Core Ideas: Prediction of clay from visible and near infrared spectroscopy was analyzed based on soil color.Models were calibrated from regional database and subsets stratified by soil color.Global model yielded over‐ and underestimation of accuracy over red and black soils, respectively.Predictions are highly dependent on the calibration dataset.Model performance evaluation is highly dependent on validation data stratification. [ABSTRACT FROM AUTHOR]

Bacterial leaf streak caused by Xanthomonas vasicola pv. vasculorum (Xvv) is an emerging disease in several corn-producing regions around the world. In Brazil, there is a lack of information on the survival of this bacterium in soil and crop residues. Thus, the objective of this study was to determine the survival of Xvv in soil and also in infected corn crop residues under the humid subtropical climate of southern Brazil. The survival of Xvv in soil was initially investigated in sandy and clayey soils maintained at 20, 25 and 30 °C under controlled conditions. The survival of the bacterium under field conditions was studied in artificially infested clayey soil. The survival of Xvv in corn crop residues was investigated in infected residues maintained on the soil surface or buried in the soil at 20 cm deep. Under controlled conditions, regardless of the type of soil, the bacterium survived longer at 20 °C than at higher temperatures. The bacterium survived for 40 days in clayey soil kept at 20 °C and four days in sandy soil maintained at 30 °C. Under field conditions, the survival of Xvv in the soil was only for 48 h and in infected corn crop residues for up to 15 days in the samples maintained on the soil surface. In samples of infected corn residues buried in the soil, the bacterium was only detected at the time the experiment was set up. In general, the results obtained in this study revealed that Xvv survives for a short period of time in soil and in infected corn crop residues under humid subtropical conditions. Therefore, soil and corn residues may not be highly important sources of primary inoculum for the development of bacterial leaf streak on corn crops under these conditions. [ABSTRACT FROM AUTHOR]

Intensified drought exacerbated by climate change aggravates the development of soil desiccation cracking, triggering several weakening mechanisms in surface soils and eventually causing various geohazards and environmental problems. This study investigates the effect and mechanisms of a bio-mediated approach based on microbially induced calcite precipitation (MICP) for remediation of desiccation cracks in soils with different layer thicknesses. We conducted 5 MICP treatment cycles on clayey soil samples to explore the influence of layer thickness on the water evaporation properties, desiccation cracking behaviors, and calcium carbonate content and distribution of MICP-treated soils. The results show that the MICP treatment can significantly decrease the water evaporation rate, the surface crack ratio, average crack width, and total crack length of all soil samples. The crack reduction ratio reaches over 90% after 5 MICP treatment cycles. The soil layer thickness has an obvious influence on the effectiveness of MICP for the clayey soil treatment. Thicker soil samples exhibit wider desiccation cracks, which, in turn, require more MICP treatment cycles for remediation. The calcium carbonate content and distribution of MICP-treated soils is governed by the original desiccation cracks, the wider cracks in thicker soil samples result in the higher calcium carbonate content of soil nearby the cracks, and the denser cracks in thinner soil samples lead to the more homogenous distribution of calcium carbonate. The remediation of soil desiccation cracks is mainly attributed to the coupling effect of the soil volume change and the accumulation of calcium carbonate crystal during MICP treatment. The findings of this study provide new insights into the mechanisms of the interaction between MICP-treated soil and drought climate and contribute to developing environmentally friendly approaches for soil improvement in regions subjected to droughts. [ABSTRACT FROM AUTHOR]

Background and aims: The accumulation of soil organic carbon (SOC) is a crucial process in mitigating climate change and ensuring soil quality. Subtropical plantations in China have shown high potential for enhancing SOC sequestration due to their high carbon sink capacity. However, the dynamics and compositions of SOC after long term afforestation are still poorly understood. Methods: We examined the dynamics of SOC and its fractions of different soil layers (0–5 cm, 5–10 cm, 10–20 cm, 20–40 cm, 40–80 cm, 80–100 cm) in a mixed broadleaf-conifer plantation (BCP), a Masson pine plantation (MP), and a Slash pine plantation (SP), and an enclosed forest (EF) in subtropical China. Both physical fractions (particulate organic carbon (POC), soil clay organic carbon (SOCclay), soil silt organic carbon (SOCsilt)) and chemical fractions (iron-aluminum-bound organic carbon (Fe/Al-OC), and calcium-bound organic carbon (Ca-OC)) were determined. Additionally, soil physicochemical properties were further analyzed. Results: Our results showed the SOC storage in the EF, BCP, MP, and SP in 2019 increased by 82%, 238%, 126%, and 103% respectively compared to 1984. The proportions of MAOC to SOC were respectively as follows: SP (65.9%) > BCP (64.9%) > EF (61.6%) > MP (53.9%). The mean proportions of SOCclay to MAOC were as follows: BCP (71.1%) > EF (66.9%) > MP (58.5%) > SP (51.0%). The mean proportions of Fe/Al-OC to MAOC were as follows: EF (53.3%) > SP (48.3%) > MP (47.9%) > BCP (39.8%). All these proportion increased with soil depth. RDA and PLS-SEM analysis revealed that soil nitrogen content and electrochemical properties (pH and EC) were the main factors that controlled SOC content and fractions. Conclusions: Subtropical plantations have significant soil carbon sequestration capabilities, but they are currently nearing saturation. Soil nitrogen content may be key factor limiting further enhancement of carbon sequestration. Due to the high proportion of MAOC and relative consistent SOC storage, BCP and SP are recommended as priorities for plantation regeneration in subtropical China. [ABSTRACT FROM AUTHOR]

Aims: Climate warming can potentially cause more plant-derived organic substrates into the surface soil. The newly produced carbon may accelerate or restrict native soil organic carbon (SOC) decomposition by priming effects (PE), so as to increase the uncertainty of the feedback prediction between climate change and soil carbon pool. However, it is controversial about the direction and driving factors of the PE of surface SOC in the warming world. Methods: In this meta-analysis, we investigated 1680 pairwise PE determined by 13C or 14C isotope labeling method in surface soils across cropland, grassland and forest from 39 warming experiments to generalize the direction and influencing factors of the warming effects on PE. Results: The meta-analysis showed that warming decreased PE across different ecosystems. The decrease was much greater in forest (effect size: -6.2) than in cropland (effect size: -2.6) and grassland (effect size: -1.7) and was more severe in simple substrates (effect size: -12.1), i.e., small molecules such as glucose and amino acid than that in complex substrates (effect size: -1.7), including plant tissues, residues and pyrolysis products, etc. The effect size of warming on PE was positively correlated with soil clay and pH, while negatively correlated with SOC content, total nitrogen, soil C/N ratio and warming intensity. Conclusions: These findings emphasize that warming will decrease the primed surface SOC loss, particularly in forest or organic matter-rich soils and larger warming intensity. [ABSTRACT FROM AUTHOR]

This study uses fly-ash-based superplasticized geopolymer by adding a naphthalene-centered superplasticizer to the geopolymerized soil. Alkali-binder ratios and alkali-activator ratios are varied simultaneously with a molarity of 10M. The optimum dosages of binder, geopolymer, and superplasticized geopolymer are found from unconfined compression tests. California Bearing Ratio (CBR), pH, consolidation, water-holding capacity, and microstructure tests were performed on optimum dosages. The clayey soil's undrained shear strength and CBR value increased as the geopolymer was superplasticized. The 28-day undrained shear strength of geopolymerized clay was around 300 kPa, attained within three days of the curing period with superplasticized geopolymer. This is because adding a superplasticizer increases the polymerization reaction rate and improves the geopolymer's performance. The maximum undrained shear strength was attained within seven days of the curing period for both cases. The undrained shear strength after a curing period of 7, 14, and 28 days for geopolymer and superplasticized geopolymer was found to be almost the same value, which shows that after seven days, curing has little role in strength improvement. The hydraulic conductivity and coefficient of consolidation of geopolymerized soil increased with the addition of superplasticizer due to the reduction in fine particles and plasticity of the residual soil. Microstructural studies using scanning electron microscope and x-ray diffraction techniques showed an interaction between soil, geopolymer, and superplasticizer, thus confirming the formation of geopolymer gel and increased polymerization rate with the superplasticizer. [ABSTRACT FROM AUTHOR]

This study investigates the evolution of soil pore structure and shear strength deterioration in compacted clayey soil under controlled wetting and drying (wd) cycles, which are expected to become more frequent due to climate change. Thirty soil samples were compacted at optimal moisture content and 90% maximum dry density. These samples were then subjected to 0, 1, 5, 10, and 15 controlled wd cycles from saturation to the wilting point, and volumetric changes were recorded during each cycle. After the wd treatment, the soil samples were scanned using X-ray computed tomography (CT) at 50 μm resolution and then sheared under unconsolidated–undrained and consolidated–undrained conditions in a triaxial test. Significant shrinkage and swelling of soil samples were observed during wd cycles, with average volumetric strain fluctuating between +12% at saturation and −5% at the wilting point. X-ray CT visualisation and analysis revealed higher porosity, more prominent pores, and increased pore length in soil samples with increasing wd cycles. Both undrained and effective soil shear strength markedly decreased with increasing wd cycles. CT-derived macroporosity and pore length were significant predictors of the soil's undrained and effective shear strength when exposed to wd cycles. The findings emphasise the considerable impact of climate change, specifically wd cycles, on clayey soil, highlighting the need for consideration in the design of earth-based infrastructure. [ABSTRACT FROM AUTHOR]

The degree of salinity, the freezing point, and the amount of unfrozen water are key factors in predicting the temperature, humidity, and mechanical behavior of saline permafrost soils used in construction as foundations for buildings. The results of the experimental studies are presented and a method for calculation of the amount of unfrozen water in saline soils is proposed. The calculated and experimental data show good convergence for both sandy and clay soils of different salinity and water content. [ABSTRACT FROM AUTHOR]

Soil nutrient cycling, the distribution of soil aggregates, and their stability are directly influenced by soil texture. Different sizes of soil aggregates provide microhabitats for microorganisms and therefore influence soil carbon (C) and nitrogen (N) mineralization. The purpose of the present study was to assess the aggregate stability and dynamics of carbon and nitrogen in macroaggregate size fractions (1-8 mm) with different clay content from meadow soils. Surface soil samples (0-15 cm) were collected from 4- to 5-year-old forage crops. Four macroaggregate size classes were isolated by dry sieving and analyzed for their mass proportions: fine macroaggregates (FM) (less than 1 mm), medium-fine macroaggregates (MFM) (1-2 mm), mediumcoarse macroaggregates (MCM) (2-4 mm), and large-coarse macroaggregates (LCM) (4-8 mm). The dry mean weight diameter (MWD), organic carbon (OC), total nitrogen (TN), carbon and nitrogen of microbial biomass (C-MB, N-MB) were determined. CO2 emission and net nitrogen mineralized (NM) were measured after 14 weeks of incubation. The amounts of FM were significantly lower than those of intermediate macroaggregates (MCM and MFM) and decreased markedly with increasing clay content within soil macroaggregates. In general, the amounts of macroaggregate size fractions were lowest in soils with high clay content. MWD exhibited a significant correlation with particle size distribution, OC, and MB-C. OC, TN, MB-C, and MB-N contents within macroaggregates increased with decreasing macroaggregate size and increasing clay content of macroaggregate fractions. The CO2 emission and NM content increased with increasing macroaggregate size, indicating higher organic C and N mineralization activity in larger macroaggregates. Mineralization of OC was lowest in macroaggregate fractions with the highest clay content. We conclude that clay content can increase the protection of microbial biomass in meadow soils. Small macroaggregates tend to contain more recalcitrant organic matter compared to larger macroaggregates. [ABSTRACT FROM AUTHOR]