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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]

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]

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]

Granite residual soil is a widely encountered clayey soil with unique microscopic soil structures. Its soil structures mainly stem from the presence of interparticle cementation by iron oxide. An attempt is made herein to experimentally quantify the impact of interparticle iron oxide cementation on soil's mechanical properties, particularly in the high suction range. The amount of interparticle cementation is artificially generated by mixing soil samples with varying mass fractions of iron hydroxide colloid. The mechanical behavior of these soil samples in the full suction range is measured via the drying cake test. Preliminary experimental results demonstrate that interparticle iron oxide cementation can significantly decrease soil shrinkage (by up to 52%), and substantially increase soil elastic modulus (by up to 1.83 times) and negative suction stress change (by up to 0.82 times). [ABSTRACT FROM AUTHOR]

In this investigation, the structural strength of a clayey soil compacted at three different dry densities (1.7, 1.6 and 1.5 Mg/m3) and three different compaction water contents (20%, 16% and 12%) was studied by using a micropenetrometer. The penetration curves at various water contents during the drying and wetting cycle were analyzed. The maximum unit penetration strength and the penetration stiffness were used to represent the structural strength. Experimental results show that the structural strength increases with decreasing water content. At a given water content, the larger dry density, the larger structural strength and the smaller hysteresis loop induced by the drying-wetting cycle. At a higher dry density, the structural strength increases and the drying-wetting cycle induced hysteresis loop becomes smaller. Specimens compacted on the wet side of optimum water content exhibit a dispersed structure and those compacted on dry side of optimum water content have an aggregated structure. For soils with a dispersed structure, the structural strength increases with decreasing water content and the growth rate is gradually accelerated. However, for soils with an aggregated structure, when dried to water content lower than 8%, the structural strength increases by a small degree or even decreases. Moreover, the hysteresis loop of the soil specimens with dispersed structure is much smaller than those with an aggregated structure. [ABSTRACT FROM AUTHOR]

As a common natural phenomenon in clayey soil, drought-induced desiccation cracks impose danger to soil structures by degrading soil mechanical strength and hydraulic properties. In this study, through a series of field tests, we evaluated the effect of microbially induced calcite precipitation (MICP) technology on the suppression of desiccation cracks in field clayey soil and examined the impacts of MICP treatment methods (two-phase and one-phase methods) and cementation solution (CS) concentrations (0.5 and 1.0 M) on soil desiccation cracking behaviors and soil microstructure variation. The results revealed that MICP is capable of suppressing desiccation cracks in field soil. The surface crack ratio, average crack width, total crack length, and average crack depth decreased with the increase of treatment cycles and CS concentration. The two-phase MICP method performed better on soil crack suppression than the one-phase MICP method. Further CaCO3 distribution and soil microstructure characterizations indicated that the CaCO3 crystals generated by the MICP process contributed dominantly to the soil crack suppression by filling crack space, bonding soil particles, and reducing soil water evaporation. This study demonstrates that MICP is expected to serve as an eco-friendly and sustainable technology for soil desiccation crack suppression at the field scale. [ABSTRACT FROM AUTHOR]

Background: Soil aggregation and organic carbon (OC) content are important indicators of soil quality that can be improved with plant residue amendments. The extent of the effects of plant residue amendments on soil aggregation and OC content across different plant residue and soil types is not fully understood. Aim: In this meta‐analysis, we evaluated the effects of plant residue amendments on soil aggregation and OC content for different plant residues (fresh, charred) and soil types varying in clay content, initial OC content, and pH. Methods: Our meta‐analysis included 50 published studies (total of 299 paired observations). We estimated the response ratios of mean weight diameter (MWD) and separate aggregate size classes, total soil OC (TSC), and aggregate‐associated OC. We also considered the effect of experimental factors (study duration, residue type, residue amount, initial soil OC, clay content, and pH). Results: The benefit of plant residue amendment on soil aggregation was larger in soils with initially low OC content and neutral pH. Initial soil OC content and pH were more important than soil clay content for OC storage in soil aggregates. Both fresh and charred plant residue amendments were effective in forming aggregates, whereas charred residues were more effective in increasing TSC. We found only a weak positive relationship between the response ratio of TSC and MWD indicating that other factors besides soil aggregation contributed to the increase in soil C storage. Conclusions: While plant residue amendments can enhance soil aggregation and TSC, these effects are likely governed by the type of plant residue and soil properties such as the initial soil pH and OC content. [ABSTRACT FROM AUTHOR]

Selenium (Se) is a trace element that plays a crucial role in human health. It has antioxidant, anti-cancer and anti-viral properties and is essential for a healthy body. The level of Se in the human body is largely dependent on daily dietary intake, which is in turn influenced by the amount of Se that enters the food chain from the soil. The global distribution of Se in soil is uneven, with a large difference in concentrations ranging mainly between 0. 01- 2. 0mg / kg. The average abundance of Se in the Earth’s crust is 0. 07mg / kg, but in some Se-enriched areas, it can reach up to 1200mg / kg. The chemical behavior of Se in soils is complex and diverse, involving processes such as adsorption - desorption, precipitation - dissolution, oxidation - reduction, methylation - demethylation and complexation reactions, each of which affects the bioavailable Se and is influenced and conditioned by factors such as soil pH, soil organic matter, metal oxides, clay and microorganisms. Roots are the primary site for most plants to absorb Se, which is then transported, metabolized, and accumulated. Plants can directly absorb Se from the soil, including Se that exists in the form of free ions, carbonate-bound Se, and Se adsorbed on the surfaces of clay and humus in soil solutions. However, selenite and selenate can be reduced to solid, insoluble Se(0) and metalSe precipitates that are not bioavailable in locally anaerobic areas (such as soil aggregates) or used by bacteria as terminal electron acceptors. Previous researchers have conducted a lot of work on chemical extraction methods, but there are still problems, such as insufficient extraction specificity and Se form transformation during the extraction process. Hence, an accurate approach for predicting the amount of soil Se that can be absorbed by plants is essential. However there are no clear paths for the choices of assessment methods and influencing factors of soil Se bioavailability. These problems have restricted the utilization of Se -enriched land resources. Thus, providing a scientific basis for the development and utilization of Se-enriched land resources is the goal here by summarizing the main assessment methods and dominant factors on soil Se bioavailability. Determining the activity of Se in soils comprehensively requires considering the complicated and varied effects of natural conditions on its bioavailability, which can be studied through characterization methods and identification of influencing factors. Therefore, it is of practical importance and a challenge to accurately determine the form of Se in soils and assess its bioavailability. Current methods for characterizing the bioavailability of soil Se include the traditional chemical extraction methods ( single extraction and sequential extraction) and the emerging Diffusive Gradients in Thin films (DGT) technique. Chemical extraction is a process that involves separating a specific component or substance from a mixture using a solvent or a chemical reagent. The extraction method depends on the physical and chemical properties of the substance being extracted and the nature of the mixture. The general steps involved in a chemical extraction method are: choosing the appropriate solvent or chemical reagent that can selectively dissolve the desired substance while leaving the unwanted components behind, mixing the mixture and the solvent / reagent together to allow the selective extraction of the desired substance, separating the extracted substance from the mixture using various techniques such as filtration, centrifugation, or evaporation, and purifying and isolating the extracted substance by further chemical or physical methods if necessary. The DGT technique is an effective environmental chemistry method used for identifying elements and compounds in various aqueous environments, including natural waters, sediments, and soils. This technique is particularly useful for detecting bioavailable trace elements, and it can be applied for in - situ detection. The DGT technique involves using a specially-designed passive sampler that comprises a binding gel, a diffusive gel, and a membrane filter. The element or compound of interest passes through the membrane filter and diffusive gel before being assimilated by the binding gel in a rate-controlled manner. Subsequently, the binding gel is analyzed post-deployment, enabling the determination of the time-weighted-average bulk solution concentration of the element or compound via a simple equation. The advantages and limitations of chemical extraction methods, DGT technique and bioavailability assessment models of Se at a regional scale are compared. Traditional chemical extraction procedures such as single extraction or sequential extraction can be used to characterize the bioavailability of Se in the soil, to a certain extent. Still, the extraction process has many limits and incomplete extraction problems. The DGT method can be used to simulate the root uptake process of plants and can better characterize the bioavailability of Se compared to sequential extraction. One of the major advantages of the DGT technique is its ability to provide accurate and reliable results, even at low concentrations. Additionally, this technique is non-destructive and can be used in-situ, making it suitable for real-time monitoring of environmental conditions. However, there are also some limitations associated with the DGT technique. For instance, the binding gel used in this method may not be specific to the target element or compound, leading to the possibility of cross-reactivity with other substances. Additionally, the technique may be influenced by factors such as temperature, pH, and ionic strength, which could affect the accuracy of the results. Using large-scale crop-root soil samples, a soil-crop Se assessment model was developed with parameters of physicochemical indicators ( e. g. soil pH, soil organic matter, soil Se, etc. ), which can better predict Se bioavailability on a regional scale. Some major and minor influencing factors affecting the uptake of Se in soil by plants are discussed. In short, topography and soil type, Se species, pH and organic matter are the main factors affecting bioavailable Se, with plant species and soil aging as secondary factors. In brief, the main limitations of the characterization methods for the bioavailability of different forms of Se are: a single extraction method can be affected by soil properties, soil / solution ratio, extraction time, the pH value of the extraction agent, and other factors. Sequential extraction methods have problems with incomplete extraction, dilution of the extract, and Se loss during centrifugation and filtration. These traditional methods cannot be used to reflect the dynamic processes of the solid - phase soil - solution - root system. DGT technology is a method that disturbs the equilibrium between soil solution and solid phase, simulating the dynamic process of Se uptake by roots, and has advantages in assessing bioavailability. However, it is still questionable whether it can be used to fully predict the replenishment dynamics of Se in field soil. The main factors affecting the bioavailability of soil Se are: (1) Topographical factors such as altitude, slope, and terrain wetness index, which have some influence on soil Se content; there are large differences in organic matter, iron / aluminum hydroxides, and pH among different soil types, which can be controlled to affect Se migration and bioavailability; (2) Soluble and exchangeable Se are more easily absorbed by plants, and selenate with better mobility is easier to absorb, transport, and metabolize in plants than selenite; (3) Increasing soil pH can generally improve Se bioavailability, but this is not the case in organic-enriched soils. Currently, there is no universally applicable method for evaluating soil Se bioavailability, as it is influenced by many factors such as topography, soil type, and soil physicochemical properties. This makes it difficult to compare and verify different results. Improving in-situ DGT analysis technology and modifying the analysis of Se forms are important technical means for accurately evaluating soil Se bioavailability and are also important directions for future development. [ABSTRACT FROM AUTHOR]

Improving and preserving soil quality in areas managed under no-tillage, especially in clayey soils, is extremely important for achieving high productivity along with environmental preservation. In this study, we evaluated the effect of three states of soil compaction and initial water saturation on pre-consolidation pressure (σp) and compaction index (CI) of two Oxisols, in order to estimate maximum loads to be applied by pneumatic machinery and agricultural implements without causing irreversible damage to soil structure. Oxisol-LVd (0.55 kg kg−1 clay) and Oxisol-LVdf (0.62 kg kg−1 clay) soils from the plateau region of Rio Grande do Sul were studied. An isoline map was generated for soil penetration resistance in the 0.07–0.12 m soil layer, with the highest state of compaction. Soil bulk density was used to characterize three state of compaction, used as treatments. Statistical analysis consisted of comparing soil σp and CI means for state of compaction, initial water saturation, and soil layers. Increase in clay content and bulk density and reduction in soil moisture is associated with increase in soil σp and decrease in CI. Average values of critical σp of the three states of compaction at field capacity are 245 kPa for Lvd, and 347 kPa for LVdf. In an annual timeframe for already consolidated no-tillage Oxisols, further soil wheeling and natural reconsolidation does not affect soil pre-consolidation and compaction susceptibility. [ABSTRACT FROM AUTHOR]

Clay–sand mixtures are deposited worldwide, such as naturally sedimentary soils and dredged clays in human activities. These mixtures usually have a fine fraction above the transitional fine content, and the compressibility is dominated by clay matrix and affected by sand fraction. In this paper, an explicit equivalent compression curve is proposed for clay–sand mixtures. This is done by directly incorporating the equivalent void ratio into the intrinsic compression model of the clay matrix. The roles of initial and evolving soil structure developed during the compression process are described by a structural variable, which can be directly computed from the experimental data. Experimental data compiled from various literature are used for evaluating the accuracy of the suggested model. They indicate that the proposed relationship of stress versus equivalent void ratio is simple yet effective to evaluate the compressibility of clay–sand mixtures with a wide spectrum of sand fraction. The model is also practically useful for estimating the compressibility of other gap-graded soils, such as clay–gravel mixtures. The proposed stress versus equivalent void-ratio equation is an elementary function and can be readily implemented into general elastoplastic models. [ABSTRACT FROM AUTHOR]

This study evaluates the strength behaviors and morphological characteristics of Lianyungang marine clay under the effect of porewater salinity. Soil at higher salinity was found to have increased internal friction angle and undrained shear strength. The difference in undrained shear strength enlarges as the confining pressure increases. Different stress paths were exhibited with soil at different salinities. Soil morphology analysis including scanning electron microscopy (SEM) and Image-Pro Plus (IPP) were employed to investigate the underlying mechanism of the enhanced strength behaviors of soft marine clay with increased salinity. Aggregated soil fabric was observed at higher salinity and contributed to enhanced strength. The results demonstrate that the aggregated soil structure is the primary mechanism responding to the enhanced strength behavior of marine clay under relatively high salinity (6%). Quantitative relationships were developed between the strength parameters and morphological characteristics of soil, i.e., area of particles, roundness of particles, area of pores, pore orientation, and fractal dimension of pore distribution, in the forms of empirical equations, and are expected to serve as the references for prediction in undrained behaviors of soft marine clays with known soil index. [ABSTRACT FROM AUTHOR]

The dry–wet cycle greatly impacts the anchoring effect of prestressed anchor cables in expansive soil. Moreover, the stress relaxation of the soil and prestress loss of anchor cables are correlated. This is due to the special expansion and contraction characteristics of this soil. To explore the influence of the dry–wet cycle, this study experimentally analyses the stress change mechanism of the anchor supporting structure in expansive soil; meanwhile, the coupled expansive soil-anchor stress model for the dry–wet cycle case is derived. Expansive soil possesses unique viscoelastic-plastic mechanical characteristics. These were simulated using a calculation framework based on the Bingham model. This was used to describe the coupling effect between expansive soil and anchor cable with equal strain. Dry–wet cycle tests were set up under three different conditions: moisture contents, the amplitude, and number of the wet–dry cycles, which verified the accuracy of the model. The experimental results show that the number and amplitude of dry–wet cycles determine the number and amplitude of cycles of anchor stress change, respectively, and the initial water content determines the reference value of stress change. The primary inference is that the number of dry–wet cycles has the greatest influence on stress attenuation of anchor, as shown in the experiment, where the stress attenuation of stress anchor was 88.12% of initial stress after three dry–wet cycles. [ABSTRACT FROM AUTHOR]

Here, we investigated the effects of biogas digestate application on flow pathways and soil properties in a sandy soil aiming at unraveling phosphorus accumulation and depletion processes in fertilized soils. Dye tracer experiments were conducted to visualize and distinguish between various flow pathways, while X-ray tomography was utilized to characterize the soil structure. The dye tracer experiments revealed differences between the control and the digestate-treated group of soil profiles in the top-soils although no statistical verification was possible amid a single plot per treatment. The stained soil profiles in both treatments indicate extensive areas of homogeneous and heterogeneous matrix flow. However, the digestate-treated group showed a decrease in homogeneous matrix flow and a notable presence of preferential flow with low interaction. The application of biogas digestate impacted various soil properties, including organic carbon content, water drop penetration time, and pH levels. Accordingly, the topsoil experienced an increase in soil organic carbon, water repellency, and a decrease in pH levels. The fraction of macropores also increased in the topsoil of the digestate-treated group, accompanied by an increase in tortuosity. Double lactate-extractable phosphorus (DL-P) distribution varied across the different flow pathways, with higher concentrations detected in matrix flow and a depletion observed in preferential flow regions in both treatments. These findings confirm the close relationship between the type of flow pathway and phosphorus distribution in soils. Additionally, a significant correlation was observed between pH levels and DL-P in the digestate-treated group, indicating potential implications for phosphorus availability. Overall, the results of this study suggest that the long-term application of biogas digestate is likely to improve soil properties as related to soil organic matter content, particularly in the topsoil of sandy soils. The study highlights the significance of the prevailing flow and transport pattern on nutrient distribution, with potential implications for nutrient management in agricultural systems. While the study design presented prevents the unequivocal assignment of differences to treatment effects, our data likely illustrate the impacts of biogas digestate amendment on the investigated sandy soil. Further research should focus on assessing the long-term effects of digestate application in loamy and clayey soils. • The impact of digestate on topsoil organic matter and water repellency is notable. • The application of biogas digestate tends to reduce the extent of homogenous matrix flow. • Macroporosity, air-filled porosity, and tortuosity alter with digestate application. • The spatial distribution of soil phosphorus exhibits high variability and is influenced by the flow field. [ABSTRACT FROM AUTHOR]

This paper aims to determine the appropriate scaling coefficient rigorously in the dynamic analysis of structures via small shaking table tests to represent the full real case while considering the soil-structure interaction problem. In addition, we investigate the seismic effects of the superstructure with flexible and fixed bases. To achieve this purpose, seven stories of concrete moment-resisting frames supported on silty clay soil were scaled. According to the shaking table specifications, a small-scaled soil-structure model was executed with a scaled factor of 1 : 50. Consequently, the scale steel skeleton model was built to represent the real superstructure. In addition, the laminar soil container for the soil block was constructed to reduce undesirable boundary effects. Three earthquakes have been applied at the superstructure base as a fixed base and at the bottom of the soil block in the soil structure system as a flexible base. The numerical simulations are implemented for scaled and real models. According to obtained results from experimental and numerical investigations, the numerical model achieved good results with experimental observation. In addition, the small scaling factor of 1 : 50 can represent the seismic response of full construction conditions with acceptable precision. It is observed that the flexible base has overestimated in lateral displacement of the real superstructure compared with a fixed base, in which the maximum amplification percentage at the roof floor level reaches up to 98% under seismic load. Otherwise, the shear force distribution along the height and base shear of the superstructure with a flexible base decreases compared with a fixed base. The maximum reduction percentage is 38% under seismic load. Consequently, the safety and cost of the superstructure are affected. [ABSTRACT FROM AUTHOR]

In this study, the suction induced by stress release was investigated by measuring the suction of instantaneously unloaded MX80 bentonite specimens after wetting in an oedometer either under different vertical stresses or under a constant-volume condition. Swell-consolidation tests were also performed, and the results were compared with those of specimens wetted under different vertical stresses or a constant-volume condition. The microstructure of the unloaded specimens was investigated using mercury intrusion porosimetry (MIP). The water content and void ratio as well as the degree of saturation of specimens were also determined. Results showed that in the case of limited water exchange between macropores and micropores during stress release, the change in suction was equal to that of stress (−ds/dσv=1). By contrast, with water exchange between macropores and micropores, soil swelling occurred, and the variation of suction was higher than that of stress (−ds/dσv>1). A method was proposed allowing such water exchange between macropores and micropores to be determined (−ds/dσv−modified=1 , where σv−modified is the modified stress considering water exchange), evidencing the macropore drying due to stress release. Comparison of results from MX80 bentonite and other clayey soils showed that when the nonclay (grains such as quartz, calcite, and so on) fraction (NCF) was lower than 35% by mass, NCF had an insignificant effect on −ds/dσv−modified (equal to 1). By contrast, in the case of higher NCF (>35%), −ds/dσv−modified became lower than 1, and the higher the NCF, the lower the −ds/dσv−modified value. These findings provide useful information for better understanding the mechanism involved at the microstructure level in the stress/suction coupling during stress release in clayey soils. [ABSTRACT FROM AUTHOR]

The structure of soil aggregates plays an important role for the turnover of particulate organic matter (POM) and vice versa. Analytical approaches usually do not disentangle the continuous re‐organization of soil aggregates, caught between disintegration and assemblage. This led to a lack of understanding of the mechanistic relationship between aggregation and organic matter dynamics in soils. In this study, we took advantage of a process‐based mechanistic model that describes the interaction between the dynamic (re‐)arrangement of soil aggregates, based on dynamic image analysis data of wet‐sieved aggregates, to analyze the turnover of POM, and simultaneous soil surface interactions in a spatially and temporally explicit way. Our novel modeling approach enabled us to unravel the temporal development of aggregate sizes, organic carbon (OC) turnover of POM, and surface coverage as affected by soil texture, POM input, and POM decomposition rate comparing a low and high clay soil (18% and 33% clay content). Our results reveal the importance of the dynamic re‐arrangement of soil structure on POM‐related turnover of OC in soils. Firstly, aggregation was largely determined by the POM input fostering aggregates through additional gluing joints outweighing soil texture at lower decomposition rate, whereas at higher decomposition rate, soil texture had a higher influence leading to larger aggregates in the high clay soil. Secondly, the POM storage increased with clay content, showing that surface interactions may delay the turnover of OC into CO2. Thirdly, we observed a structural priming effect in which the increased input of POM induced increased structural re‐arrangement stimulating the mineralization of old POM. This work highlights that the dynamic re‐arrangement of soil aggregates has important implications for OC turnover and is driven by underlying surface interactions where temporary gluing spots stabilize larger aggregates. [ABSTRACT FROM AUTHOR]

The soil–water characteristic curve (SWCC) and pore-size distribution (PSD) are fundamental characteristics of soils that determine many physical and mechanical properties. Recent studies demonstrate that both SWCC and PSD sometimes exhibit a bimodal feature. In this paper, soils with bimodal SWCCs are mainly divided into three categories: gap-graded soils, compacted clayey soils, and natural dual-porosity structural soils, from the perspective of microporosity structure. Based on the Fredlund and Xing unimodal SWCC equation, a bimodal SWCC equation is presented. The bimodal PSD equation d v / d log r for mercury intrusion porosimetry (MIP) is derived theoretically, according to the relationship between the mercury intrusion process in MIP and the water desorption process along the drying SWCC. These two associated equations have the same set of parameters, so the corresponding relationship between the bimodal SWCC and bimodal PSD can be directly shown. Three main presenting forms of PSD in MIP tests are summarized. Regression analysis results show that the proposed PSD equation can well fit bimodal PSD experimental data of various soils in the literature, and the SWCCs are predicted at the same time. [ABSTRACT FROM AUTHOR]

Soil health or soil degradation criteria are until now not well documented for a greater number of soil profiles under conventional and conservation tillage management in the literature. In order to evaluate the compaction status of more than 700 arable sites analyzed within the last 40 years, the Compaction Verification Tool (CVT) was applied according to Zink et al. (2011). Besides the ratio of air capacity (AC, at a matric potential of −6 kPa) and saturated hydraulic conductivity (Ks), the ratio of AC and air conductivity (Ka, at a matric potential of −6 kPa) was considered for evaluating the compaction status with respect to potentially harmful soil alterations. The compaction status was classified into the CVT classes I–IV, where a harmful subsoil compaction was assumed, if both values of AC and Ks or AC and Ka simultaneously exceeded (are smaller than) their defined critical value indicating limited conditions for plant growth (CVT class IV). We analyzed the compaction status of soil profiles with respect to clay content, soil type, structural stage (aggregate forms) and time span of sampling (1980–1999, 2000–2020) under conventional and conservation tillage for top- and subsoil horizons. While also some of the annually plowed topsoils under conventional tillage showed critical values of AC, Ks and Ka, the occurrence of harmful soil compaction is most dominant in the subsoil horizons (> 30 cm depth) because of a higher proportion of class IV which increased with the clay content (from < 12 % to > 12 % clay), irrespective of the applied ratio used for verification (AC/Ks or AC/Ka). Especially the highly productive Luvisols showed a high percentage of harmful compaction in the subsoil (30–41 % in CVT class IV). Soil profiles under conservation tillage management are less affected by harmful compaction. The more aggregated subsoils showed smaller proportions of class IV, which was further influenced by the clay content. • The soil threat by harmful soil compaction (CVT IV) can be explained on the ratio of AC:Ks and AC:Ka. • Luvisols show severe subsoil compaction, documented by a higher number of Class IV subsoil sites. • Soils with clay contents > 12 % are often more intensely deformed than sandier sites. • The ratios between AC and Ks and AC and Ka show similar results. • Soils under conservation tillage are less degraded than under conventional tillage. [ABSTRACT FROM AUTHOR]

Nonylphenol (4-NP) has significant adverse effects on the male reproductive system. 4-NP is commonly used in agriculture as a plasticizer and pesticide emulsifier. In the current study, two soil samples with different textures were collected to evaluate the impact of soil components on the environmental existence of 4-NP among soil aggregates. It was found that the presence of soil POM resulted in 4-NP exhibiting a significantly polarized distribution in soil aggregates, instead of the expected increase in content with decreasing particle size. High levels of organic matter and metal oxides result in a high carrying capacity of small aggregates for 4-NP in both soil textures, while POM results in a higher carrying capacity of large aggregates for 4-NP in clay soil. Another important finding is that the existence of 4-NP in soil was regulated by the percentage of aggregates. The results of contribution shown that although small aggregates in sand presented stronger 4-NP carrying capacity, whereas 4-NP was mainly distributed in large aggregates in sand. For clay soil, 4-NP was predominantly located in small aggregates with the 4-NP contributions of small aggregates amounting to 63.17%, despite the highest carrying capacity of 4-NP was observed in large aggregates. These results provide a theoretical basis to investigate the transport and transformation of 4-NP in the soil environment. [Display omitted] • Organic matter and metal oxides dominated the existence of 4-NP among soil aggregates. • The small aggregate may accumulate 4-NP more readily in the soil environment. • POM leads to polarized distribution of 4-NP in soil aggregates. • Soil texture directly affects the distribution of 4-NP among soil aggregates. [ABSTRACT FROM AUTHOR]

Soil structure is a dynamic property which controls a wide range of soil functions and is closely linked with soil carbon content. The carbon contents of agricultural soils are subject to several ongoing trends, including declining carbon stocks and attempts to increase the soil carbon reserves. In this study, we aimed to quantify how organic soil amendments, which have been shown to reduce long-term nutrient loads from agricultural fields, can impact soil structure. The structural impacts of a large one-time addition (8 tons carbon per hectare, three different soil amendments) of pulp and paper mill side stream sludges to a boreal clay soil were explored quantitatively in aggregate (X-ray microtomography, sample size 1–2 mm), core (water retention measurements, sample size 195 cm3) and column (macropores ≥80 µm, sample size ∼ 20 dm3) scales. Our results showed no micrometer-scale structural changes within soil aggregates despite the large number (25 aggregate per treatment) of imaged samples. However, the organic soil amendments had a statistically significant impact on the macroporosity. The macroporosity was on average 20–27 % higher compared to the control samples and visible even five years after the application of the amendments. Such change in soil structure improves soil aeration and fast infiltration of water during wet periods and extreme rain events and may thereby also reduce erosion risk by decreasing surface runoff. The increased microporosity was visible only in the column scale. No statistically significant differences were observed in the fraction of large pores in core scale water retention measurements. Probing the soil structural changes in macropore regime by X-ray tomography or developing sub-micron scale analysis methods are recommended approaches to improve our understanding of clay soil's structural changes induced by organic soil amendments. • The effect of a large single dose of organic matter on soil structure was studied. • Soil structure was investigated from aggregate to column scale. • 100 aggregates imaged with X-ray tomography. • Differences in intra-aggregate porosity were not found. • Only macropores (≥80 µm) were affected by the organic soil amendments. [ABSTRACT FROM AUTHOR]

• Ca2+ promoted macropores develop toward spheres under Na+ presence. • Under Na+ presence, Mg2+ promoted macropores to develop in one/several directions. • Ca2+ increased macropore size by soil flocculation, but Mg2+ by soil cracking. • Ca2+ affected soil macropore area, but Mg2+ changed macropore number. Cations in soil solutions affect soil structural stability and thus soil quality and health. Ca2+ and Mg2+ could alleviate soil clay dispersion by replacing Na+, which was the main driver. However, Mg2+ could also cause soil disaggregation and weaken aggregate integrity. Currently, most studies on Ca2+ and Mg2+ mainly examine soil hydraulic characteristics and clay particle dispersion, rather than macropore geometry. We analyzed the impact of Ca2+ and Mg2+ on soil macropore morphology by measuring macropore length, aspect ratio, and area indices. An indoor soil column experiment was set up, and irrigation water was prepared with the same electrical conductivity (4 dS m−1) and different cation compositions (Na+-Ca2+ (NC), Na+-Ca2+-Mg2+ (NCM), Na+-Mg2+ (NM) and Na+-only (N) were added), and deionized water as the control (CK). The results indicated that N had the highest soil suspension turbidity among all treatments, with NM being higher than NC. The highest percentage of soil macropore aspect ratio < 2.0 was found in N, and the highest percentage of soil macropore aspect ratio for NCM was found in > 2.0. The macropore anisotropy of NM was closer to 1.0, and anisotropy of NC was closer to 0. The soil macropore morphology of NC developed towards a spherical shape, while the macropores of NM might extend along one or several similar directions. For Na+-Ca2+ dominated soil, Ca2+ mainly affected the macropore area. However, for Na+-Mg2+ dominated soil, Mg2+ primarily influenced the number of macropores. Ca2+ inhibited the negative effects of Na+, but Mg2+ promoted unidirectional extension of macropores, posing a risk of soil cracking. This study provided a better understanding to explore the differences in the effects of different cations on soil pore structure and helped to provide guidance for field water management. [ABSTRACT FROM AUTHOR]

• Clay content and subfreezing temperature coupling affect soil FT deformation. • The clay aggregate evolution during FT accounts for the complex deformation. • Full-range evolution of soil structure is characterized via NMR and X-CT. • Quantitatively analyze contribution of micro/meso structure change to deformation. Climate change brought about significant freeze–thaw (FT) deformation of clayey soils distributed in cold regions, which resulted from soil structure evolution including pore size distribution change and crack development. However, the formation of clay aggregate that dominates the soil deformation behavior during FT remains unclear. This study investigated the effects of clay contents (5 %, 10 %, 15 %, and 20 %) and subfreezing temperatures (−5 °C, −10 °C, and −15 °C) on the soil FT deformation properties by isotropic isothermal FT tests. Meanwhile, the soil structure evolution was characterized via Nuclear Magnetic Resonance and X-ray Computed Tomography. The results indicated that the frost heave ratio (η) and thaw settlement coefficient (δ) non-linearly varied with clay content and subfreezing temperature. Specifically, the minimum η and δ were observed in the specimen with 10 % clay content, and the maximum η and δ were identified at −10 °C. This phenomenon can be attributed to the clay aggregate forming bimodal or unimodal pore size distribution (PSD) with different initial clay contents. The freezing characteristics of inter- and intra-aggregate pore water were determined by the solid-water interaction. Moreover, the FT action altered the structure of clayey soil by the change in PSD and the generation of cracks. The contribution of pore size change and crack development to the total volume change before and after FT was quantitatively analyzed. It demonstrated that pore size change was more important for the total volume change in specimens with lower clay content and higher subfreezing temperature, whereas crack development mainly contributed to the total volume change in the rest of the specimens. This study provides a deep insight into the deformation characteristics of clayey soils under different climate conditions in cold regions. [ABSTRACT FROM AUTHOR]

• SOC bioavailability significantly differed among soil particle-size fractions. • SOC bioavailability of fine sand increased by 200 %, whereas clay reduced by 60 % • The porosity of fine sand was 60% of clay. • Abundances of soil elements of clay were 6–30 times higher than fine sand. • Microbial activity, mediated by soil morphology, affected SOC bioavailability. Despite the fact that physical and chemical processes have been widely proposed to explicate the stabilization mechanisms of soil organic carbon (SOC), thebioavailability of SOC linked to soil physical structure, microbial community structure, and functional genes remains poorly understood. This study aims to investigate the SOC division based on bioavailability differences formed by physical isolation, and to clarify the relationships of SOC bioavailability with soil elements, pore characteristics, and microbial activity. Results revealed that soil element abundances such as SOC, TN, and DOC ranked in the same order as the soil porosity as clay > silt ≥ coarse sand > fine sand in both top and sub soil. In contrast to silt and clay, which had reduced SOC bioavailability, fine sand and coarse sand had dramatically enhanced SOC bioavailability compared to the bulk soil. The bacterial and fungal community structure was significantly influenced by particle size, porosity, and soil elements. Copiotrophic bacteria and functional genes were more prevalent in fine sand than clay, which also contained more oligotrophic bacteria. The SOC bioavailability was positively correlated with abundances of functional genes, C degradation genes, and copiotrophic bacteria, but negatively correlated with abundances of soil elements, porosity, oligotrophic bacteria, and microbial biomass (p < 0.05). This indicated that the soil physical structure divided SOC into pools with varying levels of bioavailability, with sand fractions having more bioavailable organic carbon than finer fractions. Copiotrophic Proteobacteria and oligotrophic Acidobacteria, Firmicutes, and Gemmatimonadetes made up the majority of the bacteria linked to SOC mineralization. Additionally, the fungi Mortierellomycota and Mucoromycota, which are mostly involved in SOC mineralization, may have the potential for oligotrophic metabolism. Our results indicated that particle-size fractionation could influence the SOC bioavailability by restricting SOC accessibility and microbial activity, thus having a significant impact on sustaining soil organic carbon reserves in temperate agricultural ecosystems, and provided a new research direction for organic carbon stability. [ABSTRACT FROM AUTHOR]

[ Purpose] The present paper aimed to study the physical properties, soil enzyme activities and their correlation characteristics of wild Bletilla striata soil in different producing areas in Guizhou, so as to provide a theoretical basis for realizing high yield and quality of B. striata artificial cultivation. [ Method] 8 soil sample plots for the wild B. striata were collected in Guizhou province to detect and analyze the soil physical and enzyme activity index characteristics and the correlation between them. [ Result]The soil density was between 2. 06 -2. 55 g/ cm³ with weak variation. The soil texture was mainly clay loam and sandy loam. In most soils, the proportion of the > 0. 25 mm size soil water-stable aggregates reached 70% . The distribution of the soil water-stable aggregates size fraction were different, 2 - 5 mm size fraction was the dominant size fraction in 4 soil plots, < 0. 25 mm size fraction was the dominant size fraction in 3 soil plots. The dominant size fraction of soil micro-aggregate was 0. 25 -0. 05 mm size fraction. The activities of urease, acid phosphatase and sucrase in soil were significantly different with strong variation. The activities of catalase in soil were not significantly different with weak variation. Soil enzyme activity was strongly influenced by the soil density, soil aggregates and microaggregates. There was a significant positive correlation between urease and acid phosphatase, which could promote each other. [Conclusion] Guizhou wild B. striata has strong adaptability to soil environment. It mainly grows in sandy soil or clay with soil clay content less than 25 %, and some wild B. striata can also grow in clay with soil clay content more than 30% ; Soil specific gravity, soil aggregates and micro aggregates are important factors affecting soil enzyme activity of B. striata. The suitable soil specific gravity is 2. 06 - 2. 55 g/ cm³, the dominant particle size is 2 - 5 mm or < 0. 25 mm, and loam is the best soil texture; Urease and acid phosphatase can promote each other. [ABSTRACT FROM AUTHOR]

Phosphorus (P) losses from clay soils can be mitigated by introducing measures for improving soil structure. These include structure liming, where a mixture of CaO or Ca(OH)2 and CaCO3 is added to the soil. In a field experiment with separately tile-drained plots on a clay loam in Sweden, we examined the effects of structure liming on leaching of total-P, phosphate P (PO4-P) and total nitrogen (N) during three years after initial application. The treatments included two application rates (8 and 16 t ha−1) of a common product in comparison with a control (no lime). Effects of structure liming emerged during the second and third year after application, with 45 and 38% lower total-P leaching than in the unlimed control. A significant effect of the application rate was found in the third year. Nitrogen leaching and crop yield were not affected. As expected, soil pH raised following structure lime addition. Measurements of aggregate stability did not confirm the reduction in P leaching, indicating that it is important to measure P concentrations in drainage water directly when assessing the effect of structure liming. [ABSTRACT FROM AUTHOR]

Liming before cultivation of sugar beets is favourable even on alkaline soils but knowledge of response in other crops is lacking. Therefore, effects of ground limestone (GL) and structure lime (SL1 slaked lime or SL2 mix of ground limestone and slaked lime) were evaluated in southern Sweden on soil structure, growth and nutrient concentration in barley under four fertilisation strategies 1.5–2 years after application. All lime products increased aggregate stability, but with variations between locations. A lower proportion of large aggregates was found in both limed treatments, and a higher proportion of small aggregates in SL. In barley, grain yield was unaffected while shoot numbers and biomass in first node stage increased for GL and biomass increased further for SL. Structure lime increased potassium concentration in plants in first node stage, due to more potassium in the product. Both lime types increased molybdenum concentration. Ground limestone reduced zinc concentration compared with no liming. Finer seedbed tilth and increased aggregate stability may explain increased biomass for GL. Higher potassium content in SL might be a further explanation. No interactions between liming and fertilisation were found. In conclusion, on the soil types studied, no change of fertilisation strategy is needed due to liming. [ABSTRACT FROM AUTHOR]

The sandy clayey purple soil is widely distributed in the middle and upper reaches of the Yangtze River, serving as one of the main soil resources in the mountainous areas of southwest China. Intense physical weathering, loose structure, and low erosion resistance are the main characteristics of sandy clayey purple soil. Therefore, environmental disturbance, such as the water fluctuation near reservoirs, heavy rainfall, and groundwater, often induces soil erosion, landslide, settlement, and soil-water disasters of purple soil. A serious threat has been posed on the village buildings and roads, even the agricultural production. The properties of water immersion disintegration with the sandy clayey purple soil can also be an important reason for water and soil disasters in the southwest mountainous areas. It is necessary to clarify the disintegration characteristics and reinforcement for the water-soil disasters prevention and control. In this study, a disintegration test was performed on the purple soil samples with different initial dry densities, water content, and grain gradation using a self-developed instrument. Meanwhile, the disintegration and evolution of sandy clayey purple soil were also analyzed from the perspective of unsaturated effective stress. Bacillus megaterium was selected to reinforce the soil samples with the Microbial Induced Calcite Precipitation (MICP), as the more suitable as Sporosarcina pasteurii in the sandy clayey purple soil areas. A Scanning Electron Microscope (SEM) was then utilized to characterize the morphologies of the soil sample, thereby determining the MICP improvement on the disintegration characteristics of sandy clayey purple soil. The results show that: 1) Four stages were divided in the whole process of immersion and disintegration of sandy clayey purple soil, including the air-water conversion, equilibrium, disintegration development, and disintegration residual stage. 2) The initial dry density, water content, and grain gradation obviously affected the disintegration characteristics of sandy clayey purple soil. Specifically, the disintegration rate and the average disintegration velocity decreased, with the increase of initial dry density and water content. In addition, the average disintegration velocity of soil increased by the content of fine particles. 3) The evolution of water and air was ranging from the pore water closed, double connected, and pore air closed morphology, with the increasing of the initial saturation. Water was rapidly absorbed into the pores under the matric suction, where the pore pressure was changed significantly. Subsequently, the effective stress of unsaturated soil rapidly reduced to the negative, leading to an interparticle compressive stress (the negative tensile stress). Once the tensile stress reached the value of effective cohesion, the unsaturated strength of purple soil was lost completely. Finally, the soil sample was then destroyed under disintegration. The more severe disintegration was also obtained with the decrease in the initial saturation of a soil sample. The decay process of the unsaturated effective stress depended greatly on the initial saturation after the purple soil was immersed in water. Specifically, the average disintegration velocity attenuated exponentially with the increase of the initial saturation. 4) The disintegration rate and the average disintegration velocity of the MICP treated soil samples decreased by 73 to 97 percentage points and 84%-99%, respectively, compared with the untreated soil. Calcium carbonate crystals formed by solidification and deposition greatly reduced the micro-cracks and large pores in the soil structure. As such, a denser pore structure was achieved to enhance the strength of intergranular cementation for the higher resistance to the disintegration of the soil. Consequently, the MICP technology can serve as an effective measure to prevent the water and soil disasters of the sandy clayey purple soil in southwest mountainous areas. [ABSTRACT FROM AUTHOR]

Simple measures of appropriate levels of soil organic matter are needed for soil evaluation, management and monitoring, based on readily measurable soil properties. We test an index of soil organic matter based on the soil organic carbon (SOC) to clay ratio, defined by thresholds of SOC/clay ratio for specified levels of soil structural quality. The thresholds were originally delineated for a small number of Swiss soils. We assess the index using data from the initial sampling (1978–83) of the National Soil Inventory of England and Wales, covering 3,809 sites under arable land, grassland and woodland. Land use, soil type, annual precipitation and soil pH together explained 21% of the variance in SOC/clay ratio in the dataset, with land use the most important variable. Thresholds of SOC/clay ratio of 1/8, 1/10 and 1/13 indicated the boundaries between "very good", "good", "moderate" and "degraded" levels of structural condition. On this scale, 38.2, 6.6 and 5.6% of arable, grassland and woodland sites, respectively, were degraded. The index gives a method to assess and monitor soil organic matter at national, regional or sub‐regional scales based on two routinely measured soil properties. Given the wide range of soils and land uses across England and Wales in the dataset used to test the index, we suggest it should apply to other European soils in similar climate zones. Highlights: We assess the use of SOC/clay ratios as guidelines for soil management in England and Wales.We use data from 3,809 sites to assess thresholds based on work for Polish, French and Swiss soils.SOC/clay threshold values can indicate degraded and good soil structural condition.The thresholds show the effect of land use and provide an index for use in England and Wales. [ABSTRACT FROM AUTHOR]

The effect of soil organic matter (SOM) on aggregation of variably-charged red soils (Ultisol) through clay zeta potential is not fully understood. Therefore, the objectives of this study were to investigate the SOM effect on the clay zeta potential and soil aggregation after fertilization. Soils under 17 years of fertilization (manure, NPK + straw, NPK, and control (CK) were adjusted by KCl solution to reach varying soil pH and concentration in order to determine clay zeta potential, cations, and aggregate size distribution. The SOM content and C-functional groups by 13C-NMR analysis were also determined. Results showed that the negative zeta potential displayed a bell-shaped pattern with increasing concentration of KCl, but displayed different amplitude of variation among treatments. Manure had the highest zeta potential value and its degree of variation in relative to the value at KCl concentration of 0.1 mol L−1 (19%), NPK + straw and NPK treatments were similar, and CK was the least. Greater negative zeta potential for manure treatment was attributed to higher SOM content, aromatic-C functional groups, and their greater concentrations of Ca2+ and Mg2+ than did the CK. As a result, higher SOM and clay zeta potential yielded in less release of amount of soil particles (< 10 μm) (r = − 0.46*) and enhanced water stable macroaggregates for manure instead of NPK + straw. Long-term manure fertilization would be suggested as a conservation practice for red soil due to its increase in soil aggregate stability and negative zeta potential in subtropical climate. [ABSTRACT FROM AUTHOR]

Unstable soil aggregates can easily be dispersed when mechanical energy is applied, denominated as readily dispersible clay (RDC) which is usually measured by turbidimetry. Faster methods that require minimum preparation at reduced costs are needed, such as the spectroscopy technique. Nevertheless, the technique has not yet been tested on soils. Electromagnetic radiation has strong interaction with soil physical elements (sand, silt, and clay) and with selective elements of the clay fraction, such as mineralogy. Thus, this study assessed the potential of 400–16,680 nm range (visible – Vis; near-infrared – NIR; short-wave infrared – SWIR; and medium infrared – MIR) spectroscopy to estimate RDC in some tropical soils. We also evaluated the wavelengths and regions that contribute to this prediction. We collected 68 samples from the underlying horizon of three different soils from three important states in Brazil The soil analyses were performed (physical and chemical) in the laboratory. RDC quantification was compared with the Vis-NIR-SWIR and MIR wavelengths models. The random forest (RF) algorithm was used to generate the prediction in the soil database. For RDC, the Vis-NIR-SWIR and MIR configuration presented a better relationship (coefficient of correlation (r) = 0.659 and root of the mean square error (RMSE) = 0.469%), although the results were similar when the regions were evaluated separately (Vis-NIR-SWIR – 350 to 2500 nm and MIR 2500 to 16,680 nm). RDC determination is more related to bands from 1980 to 2040, 6840 to 7360, and 7750 to 9820 nm. Spectroscopy showed its importance in RDC quantification, as it is fast and does not require soil preparations. The results show that spectral wavelengths are appropriate to assist on the estimative of RDC in the studied soils and may provide a basis for future research. [ABSTRACT FROM AUTHOR]

Electrification is done in newer tractors hesitantly. There will be an increase in the need for electrified mounted implements and application units. Semi-liquid manure and degestate from biogas crops are increasingly injected directly into the soil. This technique reduces nutrient losses and ammonia emissions. In the case of loamy soils and clay, a high draft force is needed for slurry deposition into the soil. With the development and testing of an application unit with reduced working width of 3 m, the draft force reduction was found to be lower by nearly one third. The field trials have been performed in two steps: first, a prototype with spiked roller and star packer as a traction element on the roller unit in 3-m working width and second, a final slurry grubber with 6-m working width and cutting coulter on the traction roller. We tested both devices with and without powering the electrified traction roller. These field tests took place on six fields near Freising in Germany. Results showed that firstly, draft force reduction up to 35% was achieved with a powered traction roller on the mounted implement having 20% slippage on the traction roller. These values were obtained by pulling a tractor with the electrified implement by another tractor in a horizontal ground level. Second, we observed a different variation range of the values among the three test fields. This results from differences in the soil structure on the test fields having pebbles and stones near the soil surface or bigger stones down the working depth of 22.5 cm. The presented results show new kinds of working scenarios and operation modes for agriculture. Electrification can be an advantage in taking care of nutrient losses and ammonia emissions as it leads to a draft force reduction on heavy soils. [ABSTRACT FROM AUTHOR]

Soft marine deposits are widely distributed in the coastal region of China. The marine soft clays have high water content and high sensitivity, which shows high compressibility and low strength. The installation of precast piles for wind turbines over soft marine clay will generate high excess pore water pressure (EPWP) with very low dissipation rate, resulting in low bearing capacity and large postconstruction settlement, which will affect long-term stability. This study investigated the generation and dissipation of the EPWP correlated with the change in soil structure during the installation of pile foundations in a project of 100 MW wind-power generation in Lianyungang, Jiangsu, China. The results show that the marine soft clay soils feature strong natural structures based on the intrinsic compression concept. The EPWP decreases with increasing distance from the pile, whose influence reaches a distance of 6 m (about 10 times the pile side length). The structural strength of natural sedimentary clay has a remarkable impact on the generated EPWP. The dissipation rate of the EPWP is very slow in mucky clay with more than half the residual value after 30 days, which is mainly attributed to the sharp decline of consolidation coefficient induced by the disturbance of natural clay soils from pile driving. Moreover, hydraulic fracturing can well explain the dissipation characteristics of the EPWP in clay. This phenomenon is actually an ongoing process especially in marine soft clay soils with a strong cementation effect. [ABSTRACT FROM AUTHOR]

When the shield machine passes through the clay layer, the clay debris cut by the cutter head usually adheres to the surface of the cutter head and is easy to form mud cakes after extrusion, which affects the safety and efficiency of construction. For the structure made of different materials, due to the different surface properties, the adhesion characteristics of clay are also different. So, selecting proper materials for the soil contacting parts in the shield machine can effectively reduce the adhesion between the structure and soil, decrease the clay adhering to the surface of the shield cutter, and reduce the possibility of further productions of mud cake. Therefore, studying the adhesion properties of clay to different materials and understanding the adhesion rule of clay to soil contacting structures are of guiding significance when selecting the materials of soil contacting parts. In this paper, the adhesion properties of cohesive soil to commonly used construction materials were studied by a self-made adhesion test device, including steel, iron, copper, aluminum, and engineering plastics (polyamide). According to the findings, the separation process of adhesion between soil and the structure by an external force can be divided into four stages, which are the adhesive elastic development stage, adhesive plastic development stage, failure stage, and detachment stage. The adhesion forces and the amount of soil adhered to the structures made of the selected materials are found to vary from each other. The adhesion forces ranked from high to low are, respectively, found on the iron, plastic, aluminum, steel, and copper surfaces. The material with the most amount of adherent soil is aluminum, followed by iron, steel, copper, and plastic. [ABSTRACT FROM AUTHOR]

The impact of chemical additives on the engineering properties of expansive soils has been studied in the past few years; however, the swelling properties as well as mineralogical and microstructural characteristics of expansive clay soils stabilized with NaCl solutions have not been clearly studied. This research work aims at investigating the expansion behavior of the studied clay soil before and after the treatment with a NaCl solution. It also aims to interpret the change in the soil geotechnical properties by monitoring the mineralogical and microstructural alterations. The treatment was performed with different NaCl doses (2.5–12.5%) for different curing times using various water amounts. The mineralogical and microstructural composition of NaCl-stabilized soil samples were analyzed by means of x-ray diffraction analysis, thermal analysis, and scanning electron microscopy. The test results indicated that the NaCl solution reduced the soil swelling in the short term significantly. The amount of water used in NaCl treatment considerably affected its performance. The mineralogical alteration of disappearance of the montmorillonite mineral from the composition of the NaCl-stabilized soil sample interpreted the reduction in the soil swelling in the short term. The 90 days, 12.5% NaCl-stabilized soil sample had densely packed cement block-like microstructure. This resulted from the binding of the soil clay aggregates by the newly formed cementitious products. [ABSTRACT FROM AUTHOR]

The main objective was to evaluate to what extent subsoil compaction on an arable clay soil (Stagnosol (Drainic)) may be alleviated after 5 years under the climate conditions in South-East Norway. Therefore, field plots which had been ploughed and under minimum tillage were compacted through wheel impact (10x) with a 6.6 Mg wheel load. Samples were taken from the 'compacted' and 'non-compacted reference' treatments at depths of 40 and 60 cm both before and directly after compaction and again 5 years later. The soil physical parameters revealed that pre-compression stress, bulk density, air capacity, air conductivity and saturated hydraulic conductivity at depths of 40 and 60 cm were impaired by compaction, especially under ploughed. After 5 years, bulk density and pre-compression stress remained almost unchanged, while air capacity, air conductivity and saturated hydraulic conductivity had increased at both the 40 and 60 cm depth on both plots as compared to the compacted state and to R for the most part, indicating the recovery of the soil structure in the subsoil. The compaction status evaluated by the 'compaction verification tool' indicates the relative reduction of 'harmful soil compaction' (after wheel impact) with a change towards 'slightly harmful compaction' for the most part with an as yet limited saturated hydraulic conductivity at both depths after 5 years. [ABSTRACT FROM AUTHOR]

Soil microaggregates contain particles of different sizes, which may affect their potential to store organic carbon (OC). A variety of methods can be used to isolate microaggregates from the larger soil structures, among which wet sieving approaches are widely employed. We developed a novel dry crushing method that isolates microaggregates along failure planes due to mechanical stresses rather than hydraulic pressures and compared the mechanical stability, OC contents and microbial community composition between dry‐crushed and wet‐sieved samples with contrasting clay contents. Dry‐crushed samples exhibited a higher stability and bacterial diversity compared to wet‐sieved samples. As a result, the dry‐crushed microaggregates had different size distributions when analysed dry and after wetting. In the dry state, dry‐crushed microaggregates were larger and contained more sand‐sized primary particles within the aggregate structures. The wetting of dry‐crushed aggregates caused a disintegration of larger microaggregates and sand‐sized primary particles into smaller microaggregates that contained finer particles. In the soils with lower clay contents, the diameter of dry‐crushed microaggregates was 40 μm larger due to more sand‐sized primary particles remaining within the aggregates. Depending on how much volume in microaggregates is occupied by large primary particles, the OC concentration increased in the soil with higher clay content. Wet‐sieved size fractions also showed a similar pattern of OC distribution, whereas more primary particles were observed outside of aggregates. Wet sieving approaches disperse the soil into OC‐rich aggregates and might be preferable if OC dynamics are investigated. Differences in bacterial community composition in dependence on clay content were more pronounced in dry‐crushed microaggregates. If intact aggregate architectures are of interest for the isolation of soil structural units, the presented dry crushing method might provide an advantageous alternative that also better preserves bacterial diversity. [ABSTRACT FROM AUTHOR]

Many techniques, most notably soil stabilization, have been developed to enhance soil characteristics due to the growing trend of constructing structures on clayey soils. Therefore, it is imperative that researchers address clay-related issues utilizing geotechnical engineering achievements. This study evaluated the effect of volcanic ash (tuff) as a natural pozzolan on the improvement of cement performance in the clay stabilization. Various compositions of cement (0%–6% by dry mass) and tuff (0%–20% by dry mass) were added to clay and cured for 7 and 28 days. Then a set of tests, including modified Proctor, Atterberg limits, electrical conductivity (EC), pH, unconstrained compressive strength (UCS), California bearing ratio (CBR), wet-dry durability, and scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, were performed on the untreated and treated samples. The secant modulus (E50) was measured to evaluate the stiffness of the specimens. The data showed that the incorporation of tuff into the studied cement-stabilized clay considerably enhanced the mixture mechanical properties and substantially reduced the plasticity index of the samples. After a 28-day period, the samples containing 6% cement and 15% tuff, as the optimum mixture, had increases of the UCS and CBR values of approximately twice those containing 6% cement. Moreover, the inclusion of tuff into the cement–soil blends increased the durability of the samples. According to the SEM and XRD analysis, the addition of tuff to the samples containing cement caused the formation of more cementitious compounds and fully changed the soil structure. The findings indicate that the use of tuff can lead to improved cement performance in the stabilization process. [ABSTRACT FROM AUTHOR]

The soil is considered the largest carbon reservoir in nature after the oceans, its content has been studied mostly in forest ecosystems, leaving aside other important ecosystems such as high Andean natural pastures, whose plant cover is made up of species diversity, which occupy large areas. The objective of the research was to determine the influence of the altitudinal variability on the Soil Organic Carbon (SOC) storage capacity of the Stipa, Festuca and Calamagrostis species, as well as its relationship with the characteristics of the soils. 73 soil samples were extracted at 0.2 m depth, between altitudes of 4000 to 4410 m.a.s.l.; To determine the COS, the wet oxidation methodology was used. The results show that there is no significant difference in the accumulation of SOC of the species studied, its general mean is 364.33 ± 48.80 t ha-1 . The correlation coefficients between the amount of SOC and altitude, sand, silt, clay, temperature and organic matter were 0.84; 0.72; -0.30; -0.56; -0.82 and 0.91, respectively. As the altitude increases the COS content increases; the variation of sand and clay in the structure of the soil, influence this process, while low temperatures favor the accumulation of carbon according to the availability of organic matter. [ABSTRACT FROM AUTHOR]

Short‐term (5 years) impact of tillage and residue management practices on physical properties and organic carbon (OC) of a silty clay soil was evaluated in a rice–wheat rotation in the Indo‐Gangetic Plains of Bihar. The experiment had three conservation agriculture (CA) practices: one full (direct‐seeded rice (DSR)–no‐tilled wheat (NTW)–no‐tilled mung bean (NTMB); fCA) and two partial (puddled transplanted rice (PTR)–NTW–conventionally tilled mung bean (CTMB); pCA1 and unpuddled transplanted rice (UPTPR)–conventionally tilled potato+maize (CTP + M)–NTMB; pCA2), which were evaluated against full conventional practice (puddled transplanted rice (PTR)–conventionally tilled wheat (CTW); TA). Subsurface compaction reduced and soil aggregation improved under both full and partial CA. Macro‐ and water‐stable aggregates increased to a large extent (26 and 11%, respectively) in full CA and to a lesser extent in partial CA, mostly due to increase in coarse macroaggregate (2–8 mm) contents in the 0–10 and 10–20‐cm depth soil layers. Steady‐state infiltration rate nearly doubled under full CA, with larger pore volume recorded in 10–20 and 20–30‐cm depth soil layers. The CA increased OC associated with all size fractions of aggregates in the surface soil layer (0–10 cm), but a higher amount of C was associated with macroaggregates, indicating relative stabilization of OC in the soil under CA. Change in bulk soil OC was larger in the 0–10‐cm depth soil layer in favour of CA, which also had an 11% increase in OC stock in the 0–30‐cm depth soil layer. Improvement in soil physical condition did not effectively translate into increased rice or wheat yields, but the system productivity increased largely. Highlights: Conservation agriculture (CA) resulted in 11–12% higher macro‐aggregation compared to conventional practice (CT).Macro‐ and total pores reduced in the 0–10 cm depth soil layer but increased in the 10–20 cm depth soil layer under CA.CA resulted in 27–35% higher aggregate‐associated OC content and 11% increase in OC stock at 0–30 cm.Full/partial CA improved soil physical condition and the productivity of rice–wheat systems in the Indo‐Gangetic Plains. [ABSTRACT FROM AUTHOR]

Pocket gophers (Geomyidae) require soils amenable to burrowing and vegetation communities that provide adequate foods. We examined the interplay of soil texture and vegetation structure in determining site occupancy of the southeastern pocket gopher (Geomys pinetis), a species of conservation concern throughout its range. Using a case-control sampling design, we compared vegetation structure and soil texture between occupied and unoccupied sites in southeastern Alabama. All occupied sites had soil clay content ≤8.05% at 0–20 cm depth. In logistic regression modeling, clay content had overwhelming support as the most important single habitat variable distinguishing occupied from unoccupied sites. Based on soil results, we focused our examination of vegetation structure on the subset of our sites with <10% clay at 0–20 cm depth. Relative odds of occupancy were highest at intermediate levels of canopy cover; however, canopy cover at occupied sites ranged widely. Compared to unoccupied sites, occupied sites contained less midstory cover and greater ground cover of graminoids and shrubs. Our results demonstrate that although vegetation structure is important in determining site suitability, soil texture may be an overriding constraint limiting potential habitat for this species. Conservation actions for southeastern pocket gophers such as habitat restoration and population translocations should ensure that target sites have suitable low-clay soils. [ABSTRACT FROM AUTHOR]

Additional void ratio and yield stress that can be easily determined by one-dimensional consolidation test are two representative parameters for the assessment of clayey soil structure. In this paper, a "structural parameter" that defined as the normalization of the integral of additional void ratio times effective vertical stress until yield stress was proposed to evaluate the disturbance induced by soil structure changes. By conducting oedometer tests on Hangzhou clay at various disturbed states, the compression index, yield stress, and structural parameter were obtained. The evolution of normalized additional void ratio during one-dimensional loading is presented to establish the soil structural indexing strategies for assessment of clay structure disturbances. Based on the laboratory investigations, a linear relationship between the normalized structural parameter and normalized yield additional void ratio was obtained. For a certain soil, specimens with the same initial void ratio but different disturbed state have a nearly constant void ratio when yielding. It is also found that soils with a higher plasticity index exhibit stronger structure and lower compressibility. In addition, quick direct shear tests were carried out to examine the undrained shear strength of soils at different disturbed states. The soil disturbance degree quantified from the undrained shear strength is found slightly higher than that from the structural parameter. This study can provide a reference for assessing the clayey soil structure. [ABSTRACT FROM AUTHOR]

Vertisols occurring in the Sępopol Plain in north-eastern Poland are characterized by high natural fertility. They belong to the group of soils with high clay content, which show the ability of periodic shrinking and swelling of clay minerals. As a result of variable moisture conditions, deep cracks and sliding surfaces are formed on the surface of the soil aggregates. The purpose of this research was to determine the chemical, physical, air-water and redox properties of vertisols developed from glaciolimnic sediments of the Weichselian glaciation, and having textures of clay (C), loam (L) and heavy clay (HC). The studied soils had high field water capacity (pF 2.0) and high content of water unavailable to plants (pF 4.2), as well as low volume of air pores. A significant positive correlation was found between the amount of clay and the volume of water unavailable to plants (pF 4.2), and a negative correlation between the amount of clay and content of water available to plants (AWC), including water readily available to plants (RAWC). The distribution of soil pores was unfavourable, and the ratio of macropores to mesopores to micropores in humic horizons was 1:2.7-5.1:1.5-5.4. The studied vertisols had low values of redox potential (Eh) and oxygen diffusion rate (ODR). The values of the Eh were above 300 mV, a threshold value for oxidised and reduced soil, only in surface horizons. [ABSTRACT FROM AUTHOR]

Aims: Shrub encroachment into grasslands alters organic carbon pools and patterns of decomposition. Here, we quantify the influence of plant life-form patches occuring on contrasting geomorphic substrates on (1) soil-litter mixing (SLM) and litter decomposition and 2) the development of soil aggregates and soil-microbial films on litter. Methods: A factorial experiment in a shrub-invaded arid grassland tested the hypotheses that SLM would promote decomposition, and that development of soil films and aggregates would be inversely related to grass cover and positively related to soil surface clay content. Litterbags containing shrub (Prosopis velutina) leaf litter were deployed on a sandy Holocene-age soil and on a clayey Pleistocene-age soil under and away from shrubs on areas with low and high grass cover. Results: SLM accelerated decomposition, with highest rates on sandy soils in inter-shrub areas with low grass cover. Decomposition on clayey soils was slower, despite more rapid development of soil films. Soil-microbial film formation in bare ground placements exceeded that in shrub or grass placements and was greater on sandy Holocene-age soils compared to clayey Pleistocene-age soils. Conclusions: Vegetation structure and geomorphology should be considered when modeling decomposition dynamics in systems with low plant cover and high rates of aeolian and fluvial soil movement. [ABSTRACT FROM AUTHOR]

When saturated, clayey soils are subjected to compressive stress and there is a time lag between the applied stress and the extrusion of pore water; there is thus a lag in the settlement. Soils under structures such as silos, tanks and so on may be subjected to cyclic loading. The theories that can be used for the calculation of consolidated settlement under cyclic loadings, such as triangular cyclic loading, contain errors due to the assumptions used in the derivations of mathematical equations. Thus, using these theories can create significant errors. The characteristics of the cyclic load, the surcharge and the specimen can affect the consolidation settlement as well as the time to achieve a steady state. Thus, in this research, one-dimensional consolidation of clay subjected to triangular cyclic loading was experimentally investigated under several conditions. The results showed that the ultimate consolidation settlement of a clay layer and the time to reach this state decreased with an increase in surcharge and an increase in cyclic time. Furthermore, the experimental results showed significant differences from the results obtained using theoretical methods. [ABSTRACT FROM AUTHOR]

Oedometer intrinsic compressibility of common inorganic soils can be explained with a few fundamental parameters obtained from simple laboratory tests. Specifically, on the basis of the liquid limit and clay percentage of a soil (fine or semi-fine), the coordinates of its intrinsic compression line can be calculated. Hence, by plotting both the oedometer compression curve of an undisturbed soil sample and the relative (measured or calculated) intrinsic compression line, the natural soil structure derived from its geological history can be estimated. Since the natural soils generally differ in mineralogical composition, the data normalisation appears to be of fundamental importance to evaluate the soil element structure in sedimentary soil profiles. The aim of this paper is to build a unique 'straight intrinsic compression line' SICL correlating the compression behaviour of soils with different mineralogical compositions based on the Burland's concept of evaluating soils structure. Specifically, it is possible to obtain the 'sedimentation compression curve' SCC of the intact soil elements down a sedimentary soil profile, which can be compared directly with the SICL and SCC of others soil profiles. [ABSTRACT FROM AUTHOR]

Lemon essential oil (EO) has several biological activities especially against breast carcinoma cells. Cysteine (CYS) and soil structures play an important role in the production of lemon EO. The application of CYS in various soils is one way of scientific technique which leads to a modification of the EO production. Thus, the aim of this investigation was to evaluate the lemon EO extracted from leaves and peels under CYS rates and soil structures. Lemon trees were exposed to different rates (0.0, 0.2 and 0.4 g/L) of CYS in sand and clay soils. The EO isolated from leaves and peels by steam distillation, then analyzed by GC/MS. Obtained results indicated that different changes were recorded in the composition of leaf and peel oils in response to CYS levels and both soils. Limonene, neral, geranial and neryl acetate were the major components of leaf EO while limonene and γ-terpinene were the main constituent in peel EO. CYS at 0.4 g/L resulted in the maximum values of EO (%) and major constituents in both soils. Various chemical groups (monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons and oxygenated sesquiterpenes) were changed with CYS application x soil textures. Production of EO with CYS is required because the application of CYS produced significant variation in the EO composition of lemon especially under various soils. [ABSTRACT FROM AUTHOR]

Industrial use of sugarcane straw for bioenergy production represents a promising opportunity for the Brazilian sugarcane sector. Nonetheless, intensified straw removal may aggravate the effects of mechanized harvesting and increase the risks of soil compaction, declining sugarcane yield. An experiment was designed, and four field studies were conducted to evaluate the cumulative effects of straw removal on soil physical attributes (bulk density, BD; soil resistance to penetration, SRP; macroporosity, MaP; microporosity, MiP, and mean weight diameter of soil aggregates, MWD) and their relationship with crop yield under clayey and sandy soils in the São Paulo state, Brazil. In each field study, four straw removal rates (no removal, NR; low removal, LR, removal of 5 Mg ha−1; high removal, HR, removal of 10 Mg ha−1; and total removal, TR, removal of 15 Mg ha−1) were arranged in a randomized block design with four replicates. The 4-year intensive management of straw removal (HR and TR) resulted in an increased soil compaction (BD and SRP values) and reduced the MWD in both sandy and clayey soils. Our findings also showed that these effects are more significant in sandy soils, where soil carbon content was substantially reduced in HR and TR treatments. Sites with higher BD and SRP induced by straw removal were strongly associated with lower sugarcane yields, especially in sandy soils. Conversely, our findings indicate that LR was not detrimental to soil physical quality and sugarcane yield. Nevertheless, considering the multifunctionality of straw in sustaining multiple ecosystem services in different soil types, straw management should be defined taking into consideration site-specific conditions. We advocate that recommendations for straw removal should also be combined with other conservationist soil management practices in order to minimize soil compaction and its negative implications on sugarcane yield and other ecosystem services. [ABSTRACT FROM AUTHOR]

Question: How do biotic forest conditions, in terms of plant functional traits and tree basal area, and soil variables influence old‐growth forest dynamics? Location: A subtropical old‐growth forest in Southern Brazil. Methods: Forest inventories were conducted in 1999 and 2017, in 24 permanent plots of 500 m2. All trees with a circumference at breast height of ≥ 30 cm were measured, identified to the species level, and tagged. We fitted linear models to evaluate the effect of the biotic variables of initial forest communities (tree basal area, trait community‐weighted mean [CWM] and both species and functional diversity metrics) and of soil variables on forest dynamics. These models included biomass dynamics (annual rate of biomass increment and mortality) and demographic rates (recruitment and mortality rates). Furthermore, linear models were used to evaluate the effect of tree survival, recruitment and mortality and biomass increment on the net biomass change. Results: We observed a positive effect of species diversity and a negative effect of CWM leaf phosphorus content on the biomass increment. Biomass loss was positively related to basal area and negatively related to the CWM of leaf nitrogen content. Overall, net biomass change was negatively influenced by biomass loss due to mortality. Recruitment rates were negatively affected by soil potassium content and were positively affected by soil pH and functional evenness of the community. Mortality rates were positively predicted by soil clay content and negatively predicted by species diversity. Conclusions: Community functional traits, basal area and soil variables predicted growth, mortality and recruitment dynamics of this subtropical old‐growth forest. This work provides important information about the biomass and demographic dynamics of subtropical forests, showing that initial community characteristics influence the gain and loss of biomass and individuals over a period of almost two decades. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing of clayey soils has been gaining traction in construction and architecture due to its eco-friendliness and design advantages. However, no comprehensive method has yet been developed for transforming these soils into a mixture that facilitates both flowability and post-deposition stability. For the development of such a method, the rheological properties and performance of 12 mixtures of sand and clay were assessed using a rotational rheometer, a custom rigidity test, and pumping tests. Subsequently, linear correlations between various results were examined to identify meaningful statistical relationships. This was followed by an in situ cylinder printing test. An analytical model was used to predict the plastic collapse of the bottom layer. To better elucidate the failure mechanism, a digital image correlation of the in situ printing test was employed. Finally, the mechanical properties of the mixtures were assessed at 14 and 28 days. The results of this study indicate that values from flow-table tests and custom rigidity tests can be used to guide the design of soil-based mixtures for 3D printing. Rheological findings show that increased kaolinite content enhances the thixotropic effect of the mixture, while coarser particle distribution increases the static yield value. A cylinder printing test until breakdown suggests that a rotational rheometer test can predict element failure due to the bottom layer plastic collapse, based on the printing parameters. Disparities between the performance of fresh and hardened mixtures were revealed by the results of the mechanical tests. [Display omitted] • Flow-table and rigidity test evaluate mixture performance in green state. • Clay particle grading and composition affect the rheological properties and printing performance. • Analytical model predicts stability and failure of 3D printed soil elements. • Disparity between green and hardened states of clay mixes in 3D printing is identified. [ABSTRACT FROM AUTHOR]

Irrigating the soil with irrigation water, which has a high sodium concentration, usually increases the sodium content of the soil. The salt and the Sodium Absorption Rate (SAR) values of irrigation water cause significant changes in the physical structure of the soil. In the clayey soil, limiter variable amount of Na is specified as 1 - 1.5 meq 100-1 g soil, which corresponds to 4-8 Exchangeable Sodium Percentage (ESP) value. In this study, the effects of some parameters such as ESP, EC and pH of irrigation water with constant EC values and 0, 15, 30, 40 SAR values were investigated. During the experiment, 3 replicates were used from each subject and soil samples were taken at the end of the experiment from each layer. ESP values were found with divided into total Na to total Ca, Mg, K and Na values. EC and pH values were obtained by extracting soil samples from the laboratory and measuring them with EC and pH measuring devices. As the SAR values increased, the ESP values increased and statistically significant differences were observed between the soil layers. The highest ESP value averaged 4.124 on the third layer of SAR40, while the lowest ESP value was 1.312 on the second layer of SAR0. As the SAR values increased, EC and pH values increased, statistically significant differences between the layers were observed. [ABSTRACT FROM AUTHOR]