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

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

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

The impact of antecedent soil moisture content on soil erosion has been a contradictory issue in erosion research, as well as process-based soil loss estimation models. The objective of this study was to investigate the impact of antecedent soil moisture content on the loss of clay soil through two-year runoff plot experiments under natural rainfall. Volumetric soil moisture sensors were used to monitor soil moisture changes, and readings were used along with rainfall records to quantify the antecedent soil moisture conditions. The results of this study show that the impact of antecedent soil moisture on interrill erosion is conditional, and the impact only exists in erosion events with a low Rainfall–Runoff Erosivity Index. The coefficient of determination between antecedent soil moisture content and soil loss per the Rainfall–Runoff Erosivity Index (Soil Loss/EI30) varies from 0.222 to 0.758, depending on the rainfall duration and Rainfall–Runoff Erosivity. The results of this study also suggest that accumulative rainfall within 48 h (Pp48) prior to an effective erosion event is strongly correlated with Soil Loss/EI30, particularly when the duration of an effective erosion event is either 3~7 h or 10~30 h. Hence, Pp48 can be considered as a replacement for antecedent soil moisture in process-based soil loss simulation models. [ABSTRACT FROM AUTHOR]

Soil moisture is one of the most important components in the land-air coupling system. Acquisition of soil relative moisture in high precision can benefit to the finer monitoring and assessment, as well as prediction and warning for drought and waterlogging. This study aims to assess drought and waterlogging using data fusion of soil water in multiple dimensions. Daily soil relative moisture was derived from China Meteorological Administration Land surface data assimilation system (CLDAS). Hourly soil relative moisture was observed from automatic soil moisture stations during April and November from the year of 2020 to 2023. The dataset also included the land use, soil properties and geographic information. A dynamic fusion model was constructed to correct the bias of relative soil moisture from between automatic soil moisture stations and CLDAS. Random forest and support vector machine models were used to take the latitude, longitude, altitude, soil sand, soil silt and soil clay as the inputs. Given that daily fusion relative soil moisture was constructed, the intensity, area and duration index were proposed to monitor and assess drought and waterlogging disasters at the multiple dimensions. The results showed that the values of determination coefficient between observed and corrected soil relative moisture by random forest model were 0.79, 0.81 and 0.80, respectively, and relative root mean square errors were 13.81%, 11.40% and 9.50%, respectively, at the length of 0-10, 0- 20 and 0-50 cm. Comparatively, the determination coefficient was 0.56-0.57 and relative root mean square error was 17.72%- 23.63% between observed and corrected relative soil moisture by support vector machine model. Thus, random forest model was accepted to effectively correct the bias of relative soil moisture between automatic soil moisture stations and CLDAS. Daily fused relative soil moisture was then generated as well. At the spatial scale, the days percent of water deficit increased from southeast to northwest in the period of April-November. Moreover, the days percent of water deficit in the central-western areas of Inner Mongolia and majority of Northwest China was greater than 70% and even 80%, while 50%-70% was found in northeastern Inner Mongolia, central-northern North China and central-western Southwest China, even less than 40% in major central-eastern areas. The days percent of soil overwetting decreased from southeast to northwest, with the value of greater than 50% only in eastern and southern South China, southern Southeast China and northeastern Northeast China. According to the water deficit index, overwetting, moisture, the area and duration index, drought and waterlogging conditions were dynamic assessed in the quantitative and finer characteristics at the intensity-area-duration dimension, especially in the typical disaster process, such as typical heat and drought event in Yangtze River in the year of 2022, typhoon Dusuri and Khanun in the year of 2023. Typically, the soil water deficit was tended to intensify in Yangtze River in the summer of 2022. The overwetting index was much lower during April-July in Huang-Huai-Hai region, whereas, there was the significant increase in late July by typhoon Dusuri, which was characterized by 12.3%-70.1% area exposed to waterlogging in 3-5 days. In Northeast China, the area exposed to overwetting or waterlogging in a large extent during 2-4th August in Heilongjiang and Jilin by typhoon Dusuri. After that, there was some decrease in 5-9th August, but it enlarged to 27.4%-41.8% in 10-13th August by typhoon Khanun. Of course, further investigation should be explored to consider more inducing factors on soil moisture. [ABSTRACT FROM AUTHOR]

Background and aims: The frequent occurrence of extreme rainfall events results in soils experiencing drying–rewetting (DRW) cycles. Such rewetting can lead to a surge in soil CO2 emissions; however, the main regulatory factors involved in this priming effect are unclear. Methods: In this study, we conducted a meta-analysis using data extracted from 43 published papers, to determine the direct regulatory factors involved in the priming effect of soil CO2. Results: The results indicated that the priming effect of rewetting on soil CO2 emissions was influenced by ecosystem type, soil properties, climatic factors, and the number of DRW cycles. The priming effect was the highest in cropland but the lowest in grassland when taking flux values observed before rewetting as the control group. It was also greater in acidic soils (pH < 6.5) and soils with a high clay fraction (clay ≥ 30%) than in other soils. The effect size (lnRR) of soil CO2 emissions was exponentially related to the mean annual precipitation (MAP), and decreased with increases in MAP. In DRW experiments, the priming effect of the first rewetting on soil CO2 emissions was the largest, an effect that gradually decreased with the number of DRW cycles, before disappearing completely. Most importantly, soil moisture influenced the peak time and the pulse time of the priming effect: the greater the change in soil moisture, the longer the peak time duration; the higher the maximum soil moisture content after rewetting, the longer the pulse time duration; and the lower the initial soil moisture content, the bigger the priming effect. Conclusion: Generally, physical mechanisms, especially soil moisture, directly regulate the CO2 priming effect during DRW cycles. Thus, this study provides a theoretical basis for assessing and predicting the impact of future precipitation changes on soil carbon cycling. Future studies should also carefully monitor any changes in soil microorganisms in response to changes in soil moisture during DRW cycles, because these appear to be significantly involved in CO2 release from soils. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the actual situation of the project on the Weihai–Yanhai Expressway section of Rongwu Expressway, the effects of water content change and the dry–wet cycle on the mechanical behavior of unsaturated clayey sandy soil were analyzed in this study. In this study, ventilated undrained triaxial shear tests were carried out on unsaturated clayey sandy soils with different water contents (6%, 8%, 10%, 12%, 14% and 16%). Concurrently, the soil samples were subjected to three distinct wet and dry cycle pathways (2~22%, 2~12%, and 12~22%) to gain an understanding of how the mechanical features of the soil changed under the different conditions. The test findings demonstrate that when the water content increases, the unsaturated clayey sandy soil's cohesiveness and shear strength diminish. The strength of shear decline exhibits a pattern of first being quick, followed by sluggish. The strength of shear and cohesiveness of clayey sandy soil declined under the influence of the dry and wet cycles, with the first cycle primarily affecting variations in cohesiveness and strength of shear. Furthermore, the strength of shear and cohesiveness of clayey sandy soil diminish more with increasing wet and dry cycle amplitude and upper water content limits. Lastly, the drying shrinkage and hygroscopic expansion of clay particles in clayey sandy soils during wet and dry cycles are not significant, resulting in less structural damage and deterioration of the mechanical properties of the soils. The study's findings have a significant impact on the durability of roadbeds made of unsaturated clayey sandy soil in both wet and dry situations. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive examination of the effects of quicklime (QL) addition on the stabilization of two distinct clayey soils with high (CH) and low plasticity (CL-tuff). The results showed that incorporating QL into the soils substantially improves their stabilization characteristics. Specifically, the addition of QL results in a notable decrease in the final water content of both soils, as shown by a reduction from 23.04 to 19.06% in CH and from 18.07 to 17.1% in CL-tuff at 4% QL addition. Furthermore, this study reveals a transformation in the plasticity properties of soils. Liquid Limit (LL) and Plasticity Index (PI) were reduced, with CH-tuff exhibiting a significant decrease in PI from 48 to 12 and an increase in Plastic Limit (PL) from 21.8 to 55 at 4% QL. CL-tuff also showed reduced plasticity, with PI decreasing to 8.33 at 4% QL. Additionally, the Immediate Bearing Index (IBI) was improved for both soil samples, indicating improved load-bearing capacities. For CH samples, IBI improved from 6.37 to 11.99 at 4% QL addition, while for CL-tuff, it increased dramatically from 4.5 to 23.6 for the same QL percentage. The findings underscore the effectiveness of QL in improving soil properties crucial for chemical stabilization, providing evidence that QL addition can be a key technique in soil stabilization, especially for soils with high plasticity or those requiring increased bearing strength. [ABSTRACT FROM AUTHOR]

This study conducted experimental investigations into the effects of electrode material and potential gradient on the effectiveness of electro-osmotic consolidation (EO) in strengthening soft soils. Seven laboratory tests were conducted on high-water-content marine clayey soils through EO. In these experimental tests, four different types of electrodes made of steel, copper, aluminum, and composite carbon fiber (CCF) were employed in four tests each to evaluate the consolidation effectiveness. Additionally, four tests, one was the comparitive study for different eletrode materials, were carried out to determine the optimal gradient for the EO using CCF electrode. Several critical properties of the tested soils were examined and evaluated in this study, including the effective voltage utilization, potential distribution, water discharge, discharge rate, energy consumption, and soil bearing capacity. The test results indicated that the CCF electrode had superior performance in water discharge, discharge rate, and average soil water content compared to metal electrodes. Furthermore, CCF led to uniform enhancement of soil strength, with treated soil bearing capacities 6.3 to 12 times higher than initial values, and 1.9 to 2.5 times higher than those attained with metal electrodes. Additionally, an effective potential gradient of 1 V/cm was identified for the EO with the CCF electrode, providing a higher discharge rate and a larger soil strength in a uniform distribution. Moreover, the use of CCF electrode significantly reduced corrosion compared to metal electrodes during the consolidation process, further contributing to improved consolidation efficiency. This study offers valuable insights and recommendations for the utilization of CCF in marine clayey soils, effectively addressing the challenges posed by electrode corrosion and high energy consumption in EO applications. [ABSTRACT FROM AUTHOR]

• Calibration of red clay with different water contents based on EDEM software. • The Hertz-Mindlin with JKR Cohesion model was used to model red clay soil's physical properties. • Experimental studies provide insights into the impact of soil moisture content on its properties. • Technical references for future research on soil-tool interactions were provided. Distinct physical properties of red clay soil in hilly and mountainous regions of southwest China, including high adhesiveness and density, challenge the operation of agricultural machinery. A scarcity of accurate discrete element simulation parameters for this soil type restricts computational modeling. The study was focused on red clay soil with a moisture content of 12.50% ± 1% and a measured repose angle of 35.54°. The soil's inherent physical properties were identified through experimental assessments. Soil contact mechanical parameters were obtained from the GEMM database, and optimal contact parameter ranges were determined using Steepest Ascent Experiments, with the simulated soil particle repose angle serving as the response value. A second-order regression model was developed using a quadratic regression rotation orthogonal combination test. By taking the actual repose angle as the optimization criterion, parameters were optimized. The optimal contact mechanical parameters in EDEM simulations were identified as: JKR surface energy at 8.981 J/m2, recovery coefficient at 0.474, dynamic friction coefficient at 0.196, and static friction coefficient at 0.45. The model yielded a repose angle of 36.21°, closely corresponding with the observed value, with a relative error of 1.80%. The parameters calibrated in this study offer a valuable reference for future soil-tool interaction studies and tillage implement optimization in these regions. [ABSTRACT FROM AUTHOR]

Soft clay is identified to have some unfavorable characteristics when used as the foundation for construction work. This is due to the low bearing capacity and high compressibility which often leads to prolonged consolidation settlement. Therefore, soil improvement is necessary, and this can be achieved through the Vacuum Consolidation Method (VCM). This research focused on conducting laboratory-scale model tests to determine the characteristics of clay soil improved by vacuum consolidation in terms of its physical properties, hydrolysis, and compressibility. The results showed that the water content decreased as soil approached the Prefabricated Vertical Drain (PVD). A similar trend was also observed for the compression index value; this is because local density occurs in the soil near the PVD as a result of the movement of fine particles towards the PVD, which fills the empty pore space. Moreover, soil permeability in both vertical and horizontal directions reduced, and the soil became anisotropic after VCM improvement. The results of this research can be a consideration in the use of the VCM method for soft soil improvement, especially the problem of clogging zones that occur due to the suction pressure of the vacuum pump, which can reduce the performance of the VCM. [ABSTRACT FROM AUTHOR]

In heavy soils, changes in humidity incur soil volume changes. In the horizontal plane, these are manifested by cracks formation and in the vertical plane by the movement of the soil surface. Cracks have a significant impact on hydrodynamics of the soil profile. The work is based on the hypothesis that soil volume changes depend on both the content of clay particles in soil and soil volumetric moisture. The aim of the work is to measure and analyze the changes in the width of the cracks and their reaction to the changes in volumetric soil moisture. One of the objectives of the work was to design a simple tool for accurate measurement and calculation of the crack width on the soil surface. For the study of crack width, a soil profile in an area on the East Slovakia Lowland was selected. The profile was examined under conditions of extreme drought, at the turn of July and August 2022. Crack width varied between 1.0 cm and 3.3 cm. The calculation procedure was evaluated as satisfactory for estimating the change in crack width on the soil surface. [ABSTRACT FROM AUTHOR]

Moisture migration in unsaturated soils is a result of the interaction between temperature and soil microstructure. In order to reveal the mechanism of moisture increase of subgrade soils under diurnal cycle conditions, a series of macro and microscopic tests were carried out on the unsaturated silty clay and sand soil, including liquid–vapor mixed migration tests simulating a one-dimensional subgrade, environmental scanning electron microscope (ESEM), and matrix suction test. Then, the soil microstructure in microscopic images was investigated using the particle (pores) and cracks analysis system (PACS). Next, the relationship between the thermal effects of the soil–water characteristic curve (SWCC) and changes in soil microstructure was analyzed. Finally, the change mechanism of liquid–vapor mixed migration based on the change in soil microstructural under thermal effects was analyzed. The results showed under the diurnal cycle, both the silty clay and sand soil columns appeared in the phenomenon of a "diurnal cycle of water vapor migration", which led to moisture accumulation at the top of the soil layer. In silty clay soil column, moisture was primarily driven by water vapor pressure and migrated upwards. Additionally, moisture redistribution led to changes in soil microstructure, which in turn influenced the process of moisture migration. The moisture content in the upper soil layer increased making both inter-aggregate and intra-aggregate pores decrease. The moisture content in the lower soil later decreased, leading to the water-holding capacity of the lower soil layer to increase. So, the moisture migration gradually decreased at night. In the sand soil column, moisture migration was mainly driven by gravity potential and migrated downwards. Moisture redistribution made inter-aggregate pore and matrix suction of the upper soil layer increase, leading to an increase in moisture migration at night. [ABSTRACT FROM AUTHOR]

In order to explore the effects of planting tea trees under Phyllostachys edulis forest on soil organic carbon storage and carbon components, we took pure bamboo forest, bamboo-tea mixed forest and evergreen broad-leaved forest as the study objects, collected the surface soil(0-10 cm)of these three forest types, and measured soil organic carbon(SOC), carbon components, biotic and abiotic factors. The results were as follows:(1)The diversity of understory plants in bamboo-tea mixed forest was significantly lower than that in pure bamboo forest, but there was no significant differences in soil organic carbon density[(22.54 ± 2.09)t·hm-2 ] and carbon composition between bamboo-tea mixed forest and pure bamboo forest(P>0.05). Mineral-associated organic carbon(MOC)was(20.13 ± 1.83)g · kg-1, accounting for 92.66% of total organic carbon. The soil organic carbon density of evergreen broad-leaved forest was 41.15% and 41.00% higher than that of bamboo-tea mixed forest and pure bamboo forest(P>0.05).(2)Soil microbial biomass carbon(MBC)content, 16S rRNA gene abundance, cbbL gene abundance and microbial carbon use efficiency of these forest types were(0.58 - 3.08)g·kg-1,(2.18×1010 - 5.65×1010)copies·g-1,(0.37×108-1.10×108)copies·g-1, 0.03 - 0.28, respectively. But there were significant differences about these microbial indicators between three forest types(P>0.05).(3)SOC of the three forest types was significantly negatively correlated with soil pH, gravel content and aboveground litter biomass, and significantly positively correlated with soil clay content, silt content, total nitrogen, C:N, total phosphorus and ammonium nitrogen(P<0.05).(4)In terms of different carbon fractions, particulate organic carbon(POC)and MOC were significantly negatively correlated with soil pH, gravel content and root biomass, and significantly positively correlated with soil water content, clay content, silt content, total nitrogen, C:N, total phosphorus and ammonium nitrogen(P<0.05). In conclusion, the mixed transformation of bamboo and tea will cause the decrease of understory vegetation diversity in the original pure bamboo forest, but it will not cause the decrease of soil carbon storage; compared with evergreen broad-leaved forest, it is necessary to improve the management measures of bamboo to improve its carbon sink efficiency. [ABSTRACT FROM AUTHOR]

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: Water retention capacity (WRC) is crucial for assessing the hydro-physical behavior of unsaturated soils. Dispersive soil, erodible and found mainly in arid regions, lacks sufficient WRC knowledge, hindering its stability evaluation in unsaturated state. This study aimed to explore the WRC of dispersive soil by measuring its matric suction (ψ) under coupling effects of dry density (ρd) and soluble salt content (η). Materials and method: Compacted specimens with different ρd and η were prepared. For each ρd-η case, six levels of soil mass water content were considered and the ψ was measured via filter paper method. Soil water characteristic curves (SWCCs) were fitted by van Genuchten model. Results and discussion: The WRC of dispersive soil enhances as ρd increases. Increasing η first weakens then strengthens the WRC, showing suction dependence. The air-entry value and residual state suction range within 0.95–17.8 kPa and 15.7–98.4 MPa, respectively. As for the air-entry value, increasing η from 0.3% to 2.0% decreases it from 36.0% to 58.7% when ρd increases, and its average growth rate changes from 174.5% to 265.3% when ρd exceeds 1.53 g/cm3. Increasing ρd reduces the average water loss rate of SWCC transition stage, while the impact of η is nonmonotonic, with an inflection point at 1.0%. Conclusions: The ρd and η influenced the WRC of dispersive soil individually and interactively. The effect of ρd links to the water release sequence from pores of different sizes, whereas that of η, rather complex and non-monotonic, relates to clay electrochemistry and salt phase. [ABSTRACT FROM AUTHOR]

A method for an a priori estimation of the frost heave ratio for clayey soils, considering the degree of their water saturation upon a closed system of freezing, is proposed. The proposed approach involves the introduction of a new parameter in the mechanics of frozen soils, namely, the frost heave index of clayey soils, which characterizes the degree of frost heaving of soil relative to the maximum height of the frost heave of soil that is fully saturated with water. An introduced parameter is used in the final formula to estimate the frost heave ratio of clayey soils. Laboratory experiments were performed to determine the height of frost heaving of clayey soils with a variation in their moisture and porosity to verify the proposed approach. A comparison of the experimental and calculated results showed a suitable convergence sufficient for the practical use of the formula to determine the frost heave ratio in a closed system of freezing. An example of a calculation to justify antiheaving measures using the proposed estimation of the frost heave ratio is given. [ABSTRACT FROM AUTHOR]

The scarcity of water is a major problem in Tunisia. Thus, 50% of water resources are with salinity higher than 1.5 g L−1 and 16% with salinity exceeding 3 g L−1. To use this saline water in crop irrigation, new technologies for water treatment can be applied such us electromagnetic irrigation water device. In this context, a field experiment was carried out at Zitouna Agricultural Development Company in Zaghouan governorate to study the impact of magnetized irrigation water on clay soil and on leaf mineral content of Arbequina olive tree growing under drip irrigation with saline water. Bimonthly soil samples were taken with an auger every 20 cm over 1 m depth. Olive leaf samples were taken from the trees located above the soil sampling points. The results showed that soil parameters variations are the same throughout the depths 0–20, 20–40, 40–60, 60–80, and 80–100 cm. As a consequence, the interpretation of the effect of magnetized irrigation water was restricted to 0–100 cm soil depth. However, a slight decrease of the pH was observed with the use of magnetized water. On other side, we reported that the electromagnetic treatment of irrigation water increases the soil moisture (Hs) and favors the absorption of N, P, K+, and Na+ by olive tree leaf tissues. Also, water use efficiency (WUE) in the plot irrigated with treated water is equal to 1.3 compared to that irrigated with untreated water. Thus, 30% improvement in yield using treated water. [ABSTRACT FROM AUTHOR]

Successful use of stable isotopes (δ2H and δ18O) in ecohydrological studies relies on the accurate extraction of unfractionated water from different types of soil samples. Cryogenic vacuum distillation (CVD) is a common laboratory‐based technique used for soil water extraction; however, the reliability of this technique in reflecting soil water δ2H and δ18O is still of concern.This study examines the reliability of a newly developed automatic cryogenic vacuum distillation (ACVD) system. We further assessed the impacts of extraction parameters (i.e. extraction time, temperature and vacuum) and soil properties on the recovery of soil water δ2H and δ18O for the ACVD and traditional cryogenic vacuum distillation (TCVD) systems. Finally, we investigated the potential influence of CVD (ACVD and TCVD) technique on the prediction of plant water uptake through a sensitivity analysis.Both ACVD and TCVD similarly extracted water from the rewetted soils, but none of the CVD systems successfully recovered the isotopic signatures of doped water from soil materials. Mean δ2H offsets of extracted soil water were −2.6 ± 1.3‰ and −2.4 ± 1.7‰ for ACVD and TCVD, respectively, while mean δ18O offsets were −0.16 ± 0.14‰ and −0.39 ± 0.37‰. The isotopic offsets of CVD systems were positively correlated with soil clay content, and negatively correlated with soil water content. Using corrected soil data (with CVD offsets) could improve the prediction of plant water uptake based on its high correlation with the environmental factors.This study identifies the isotopic offsets of CVD systems (i.e. ACVD and TCVD) and provides possible solutions for better predicting plant water sources. Even though, the wide use of CVD techniques probably induce noticeable uncertainties in the prediction of plants water uptake depths. The dataset of soil water extraction in this study will have implications for the technological development of CVD techniques. [ABSTRACT FROM AUTHOR]

When the seeding monomer of no-tillage maize planter operates in sticky and wet soil, soil bonding and blocking of soil-touching parts will occur to different degrees, leading to functional failure and affecting the quality of seeding operation. Aiming to improve the anti-adhesion property with minimum cost, a seeding monomer is modified to operate in sticky and wet soil with the support of TRIZ (Theory of Inventive Problem Solving). There are two major scheme adjustments, including self-cleaning seedbed collating device and split gauge wheel. The Su-field model of seedbed collating device is constructed, and the design scheme of smaller wavy coulter and dirt scraper is proposed on the basis of the standard-solution tool and water-film theory. And the parameters of the wave are determined on account of force analysis of soil particles and bionic earthworm. Based on the systemic-functional analysis of the seeding depth-limiting device and the force analysis of gauge wheel during operation, a split type of depth-gauge wheel with large lug hole is designed. As a result, the field trial demonstrates that the improved monomer could meet the operation requirements of clay soil with the water content of 15%-25%. Compared with the original model, the residual clay content is decreased (seedbed collating device 57.5%, gauge wheel seeding depth-limiting device 10%). This study can provide reference for the anti-adhesion design of soil-contacting parts of agricultural machinery. [ABSTRACT FROM AUTHOR]

Soil moisture content (SWC) can change the diversity and composition of soil fungal communities by affecting soil texture and soil nutrients. To explore the response of soil fungal communities to moisture in the grassland ecosystem on the south shore of Hulun Lake, we set up a natural moisture gradient that was subdivided into high (HW), medium (MW), and low (LW) water contents. Vegetation was investigated by quadrat method, and aboveground biomass was collected by the mowing method. Soil physicochemical properties were obtained by internal experiments. The composition of the soil fungal community was determined using high-throughput sequencing technology. The results showed significant differences in soil texture, nutrients, and fungal species diversity under the moisture gradients. Although there was significant clustering of fungal communities in different treatments, the fungal community composition was not significantly different. According to the phylogenetic tree, the Ascomycota and Basidiomycota were the most important branches. The fungal species diversity was smaller when SWC was higher, and in this environment (HW), the fungal-dominant species were significantly related to SWC and soil nutrients. At this time, soil clay formed a protective barrier for the survival of the dominant classes Sordariomycetes and Dothideomycetes and increased their relative abundance. In summary, the fungal community responded significantly to SWC on the southern shore of the Hulun Lake ecosystem in Inner Mongolia, China, and the fungal community composition of the HW group was stable and easier to survive. [ABSTRACT FROM AUTHOR]

As one of the physical quantities concerned in agricultural production, soil moisture can effectively guide field irrigation and evaluate the distribution of water resources for crop growth in various regions. However, the spatial variability of soil moisture is dramatic, and its time series data are highly noisy, nonlinear, and nonstationary, and thus hard to predict accurately. In this study, taking Jiangsu Province in China as an example, the data of 70 meteorological and soil moisture automatic observation stations from 2014 to 2022 were used to establish prediction models of 0–10 cm soil relative humidity (RHs10cm) via the extreme gradient boosting (XGBoost) algorithm. Before constructing the model, according to the measured soil physical characteristics, the soil moisture observation data were divided into three categories: sandy soil, loam soil, and clay soil. Based on the impacts of various factors on the soil water budget balance, 14 predictors were chosen for constructing the model, among which atmospheric and soil factors accounted for 10 and 4, respectively. Considering the differences in soil physical characteristics and the lagged effects of environmental impacts, the best influence times of the predictors for different soil types were determined through correlation analysis to improve the rationality of the model construction. To better evaluate the importance of soil factors, two sets of models (Model_soil&atmo and Model_atmo) were designed by taking soil factors as optional predictors put into the XGBoost model. Meanwhile, the contributions of predictors to the prediction results were analyzed with Shapley additive explanation (SHAP). Six prediction effect indicators, as well as a typical drought process that happened in 2022, were analyzed to evaluate the prediction accuracy. The results show that the time with the highest correlations between environmental predictors and RHs10cm varied but was similar between soil types. Among these predictors, the contribution rates of maximum air temperature (Tamax), cumulative precipitation (Psum), and air relative humidity (RHa) in atmospheric factors, which functioned as a critical factor affecting the variation in soil moisture, are relatively high in both models. In addition, adding soil factors could improve the accuracy of soil moisture prediction. To a certain extent, the XGBoost model performed better when compared with artificial neural networks (ANNs), random forests (RFs), and support vector machines (SVMs). The values of the correlation coefficient (R), root mean square error (RMSE), mean absolute error (MAE), mean absolute relative error (MARE), Nash–Sutcliffe efficiency coefficient (NSE), and accuracy (ACC) of Model_soil&atmo were 0.69, 11.11, 4.87, 0.12, 0.50, and 88%, respectively. This study verified that the XGBoost model is applicable to the prediction of soil moisture at the provincial level, as it could reasonably predict the development processes of the typical drought event. [ABSTRACT FROM AUTHOR]

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Gypseous soils are present in many parts of the world, particularly in the Middle East and Africa. While effects of addition of various percentages of gypsum on the engineering properties of soils have been investigated previously by many researchers, effects of presence of naturally occurring gypsum crystals on soil properties have been less studied. Study of these effects is important since many civil engineering developments need to be carried out in or on soils containing naturally occurring gypsum crystals. These crystals consist of fragile particles that break easily, even during handling and laboratory testing, and their presence affects many properties of in situ soils. Moreover, estimation of the percentage of crystallized gypsum in such soils usually requires unconventional chemical or physical tests since visually estimated percentages are often misleading due to the transparent nature of the crystal grains, especially when mixed with fine-grained soils. The current study presents results of tests on a low-plasticity clayey soil containing gypsum crystals. Percentages of crystals present in the soil are determined using a simple procedure involving water content determination of the soil dried at 110 and 40 °C. Effects of crystalized gypsum content on the in situ and laboratory properties of the clayey soil are studied, and results are discussed in the context of pavement design. It is shown that in situ soil unit weight, field CBR, plasticity, grains specific gravity, maximum dry density and optimum moisture content decrease with the increase in the gypsum crystal content of the soil. [ABSTRACT FROM AUTHOR]

This paper presents a case study for the testing of locally available resources selected to form a clay barrier. This is a promising technique for protecting historic masonry from ground moisture intrusion. There are several historical precedents for the use of calcareous, clayey soils to form moisture resilient barriers in architecture. More recently, specialised bentonite mixtures have arrived on the market. Assessment protocols for suitable barrier material will help establish general codes and the potential for this technique to make use of locally available resources, either in their raw state or in mixtures. In this project, a variety of different geo-materials are collected from around Pompeii to test their suitability for use in a barrier installation on a tomb in the archaeological site. The methodology consists of laboratory tests used in the assessment of barrier material for landfill engineering, and rapid tests used in earth construction. A mixture of a calcareous clay and a sand produced barrier material with suitable properties. The methodology can form the basis of assessments elsewhere, to further develop the potential of using locally available geo-resources for conservation and construction projects. [ABSTRACT FROM AUTHOR]

In other words, although soil mineralogy may well play a key role in the varying strength of clays with the water content, I c i SB u(FC) sb mobilised at the FC liquid-limit water content does not respond in any significant way to soil mineralogy; the same conclusion has been previously reported by O'Kelly I et al i . ([16]) employed a Geonor G-200 model 60°-60 g FC device to determine the apparent variations of I c i SB u(FC) sb with the water content about the I w i SB L-FC(BSI) sb (established using the 30°-80 g FC device) for the various fine-grained soils investigated. Keywords: Liquid limit; fall-cone; cone factor; undrained strength; fine-grained soil EN Liquid limit fall-cone cone factor undrained strength fine-grained soil 170 174 5 04/04/23 20230301 NES 230301 It is the authors' opinion that confusion could arise from the analyses and explanations of the experimental fall-cone (FC) results presented in the paper by Nagaraj I et al i . Figure 1(a): An x:y scatter plot showing the changes in undrained shear strength at the British Standard fall-cone liquid-limit water content against the British Standard fall-cone liquid-limit water content for six different fine-grained soils investigated by Nagaraj et al. (2018). [Extracted from the article]

In geotechnical projects involving soft soils, cement-mixed soils are an excellent way to improve the mechanical behaviour and engineering performance of soils. The water-to-cement ratio, cement content, and porosity are the most critical parameters impacting the strength of cement-mixed soils, but their effects are less well understood. The proportional influence of cement amount, porosity, and moisture content on cement-mixed soil strength is investigated in this research. The results showed that as the water-to-cement ratio increases, the influence of cementation and porosity on unconfined compressive strength decreases. The blended volume ratio is proposed as a new and adequate index for evaluating cement-mixed soil strength based on the experimental results. The blended volume ratio is the product of the void/cement volume ratio and the water/cement volume ratio. While the current index has not fully addressed the important effects of the water-to-cement ratio and porosity, the blended volume ratio allows describing the concurrent influences of porosity, cement amount, and water amount on the strength development. The experimental results showed that the cement-mixed soil strength is a function of the blended volume ratio. An empirical equation based on the blended volume ratio was then proposed for predicting the strength of cement-mixed soils. The validation of the proposed equation is verified by strength analysis for several different test data sets. A good agreement between measured and predicted results indicated that the proposed model is applicable to predict well the strength of cement-mixed soils. [ABSTRACT FROM AUTHOR]

A soil water unit weight of 9.8 kN/m3 has been universally considered to quantify soil volumetric phase properties such as void ratio and degree of saturation, but has been found to greatly vary depending on soil type and the volume scale with which it is defined. Recent experimental and theoretical evidence has indicated that the unit weight of soil water can be significantly greater than 9.8 kN/m3 for clayey soils when gravimetric water content is less than 30%. A soil water unit weight as high as 18.8 kN/m3 is evident for some expansive soils at low water content. The significance of abnormally high water unit weight in quantifying soil phase volumes, saturation, and void ratio was experimentally assessed for various clayey soils and theoretically interpreted as a function of water content and soil type. For clayey soils with low liquid limit, average soil water unit weight can be as high as 12.5 kN/m3 for gravimetric water content less than 10%. This leads to an overestimation of liquid-phase saturation and void ratio by as much as 8% if a soil water unit weight of 9.8 kN/m3 is used. For clayey soil with a high liquid limit, the average soil water unit weight can be as high as 18.8 kN/m3 for water content less than 18%, leading to overestimation of liquid-phase saturation by as much as 36% and void ratio by as much as 20% if 9.8 kN/m3 is used. Charts were developed to estimate average soil water unit weight as a function of soil specific surface area and water content, and as a function of liquid limit and water content. The commonly used value of 9.8 kN/m3 for water unit weight can lead to significant errors in estimating phase volumes, void ratio, and saturation for clayey soils. [ABSTRACT FROM AUTHOR]

The paper deals with three issues relevant to the application of TDR methods for monitoring water content in compacted clay soils: (i) the dependence on dry density, (ii) the ability to monitor changes in water content in clay soil approaching saturation, and (iii) difficulties in performing efficient and reliable calibrations. A calibration scheme which inherently controls dry density of the specimen has been developed and applied. The methodology creates continuous calibration curves over a range of volumetric water content from a single test specimen. The new approach has been applied in monitoring the advance of a wetting front through a compacted swelling clay in a laboratory environment. [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]

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As an important means of curbing soil degradation, afforestation has a profound impact on regional soil properties and quality. However, it is still unclear regarding how to conduct a systematic assessment of soil properties and soil quality and the impact of vegetation characteristics and plant functional traits in leguminous plantations with different afforestation years in drylands. Therefore, we investigated the vegetation characteristics and determined the functional traits of leaves and roots and the soil physicochemical properties of Caragana korshinskii plantations with 13, 35, and 55 years. The results showed that tree height; crown diameter (CD); root dry matter content; root water content; soil clay, silt, and sand contents; bulk density (BD); soil water content; soil organic carbon (SOC); total nitrogen (TN); available nitrogen; total phosphorus (TP); available phosphorus (AP); and soil quality index (SQI) changed significantly with an increase in afforestation years. Although the specific leaf area did not show a significant variation, it had a significant negative effect on soil properties and SQI, except for soil sand and BD. Soil sand and BD decreased with the afforestation succession, but the succession pattern of soil clay, silt, SOC, TN, TP, and AP was 13 years < 35 years < 55 years, and SQI increased from 0.20 (13 years) to 0.77 (55 years). This indicated that long-term legume afforestation led to the transformation of soil texture from silty loam to silt and significantly improved the soil properties and quality in the study area. [ABSTRACT FROM AUTHOR]

The economic and environmental sustainability of extensive livestock production systems requires the optimisation of soil management, pasture production and animal grazing. Soil compaction is generally viewed as an indicator of soil degradation processes and a determinant factor in crop productivity. In the Montado silvopastoral ecosystem, characteristic of the Iberian Peninsula, animal trampling is mentioned as a variable to consider in soil compaction. This study aims: (i) to assess the spatial variation in the compaction profile of the 0–0.30 m deep soil layer over several years; (ii) to evaluate the effect of animal trampling on soil compaction; and (iii) to demonstrate the utility of combining various technological tools for sensing and mapping indicators of soil characteristics (Cone Index, CI; and apparent electrical conductivity, ECa), of pastures' vegetative vigour (Normalised Difference Vegetation Index, NDVI) and of cows' grazing zones (Global Positioning Systems, GPS collars). The significant correlation between CI, soil moisture content (SMC) and ECa and between ECa and soil clay content shows the potential of using these expedient tools provided by the development of Precision Agriculture. The compaction resulting from animal trampling was significant outside the tree canopy (OTC) in the four evaluated dates and in the three soil layers considered (0–0.10 m; 0.10–0.20 m; 0.20–0.30 m). However, under the tree canopy (UTC), the effect of animal trampling was significant only in the 0–0.10 m soil layer and in three of the four dates, with a tendency for a greater CI at greater depths (0.10–0.30 m), in zones with a lower animal presence. These results suggest that this could be a dynamic process, with recovery cycles in the face of grazing management, seasonal fluctuations in soil moisture or spatial variation in specific soil characteristics (namely clay contents). The NDVI shows potential for monitoring the effect of livestock trampling during the peak spring production phase, with greater vigour in areas with less animal trampling. These results provide good perspectives for future studies that allow the calibration and validation of these tools to support the decision-making process of the agricultural manager. [ABSTRACT FROM AUTHOR]

A series of unconsolidated-undrained triaxial tests and unconfined compressive strength (UCS) tests for cemented soils with different curing times were carried out in this research. In total, three cemented soil mixtures with different cement contents were adopted in the tests, and the confining pressure was controlled in the range of 100–1600 kPa. The influence of curing time, cemented soil mixture ratio and confining pressure on the compressive and shear capacity of cemented soil was analyzed based on the test results. The test results indicate that the cement content and curing time both had a great influence on the strength of cemented soil, the UCS of the cemented soil increased linearly with the curing time under the semi-logarithmic coordinate, the cemented soil exhibited strain softening characteristics in the axial shear tests, and the maximum deviatoric stress of the cemented soil increased with the increase in confining pressure. A linear correlation was found between the cohesion and the UCS of cemented soil, and the cohesion was about 0.40 times the compressive strength. [ABSTRACT FROM AUTHOR]

Soil water content (SWC) sensors are widely used for scientific studies or for the management of agricultural practices. The most common sensing techniques provide an estimate of volumetric soil water content based on sensing of dielectric permittivity. These techniques include frequency domain reflectometry (FDR), time domain reflectometry (TDR), capacitance and even remote-sensing techniques such as ground-penetrating radar (GPR) and microwave-based techniques. Here, we will focus on frequency domain reflectometry (FDR) sensors and more specifically on the questioning of their factory calibration, which does not take into account soil-specific features and therefore possibly leads to inconsistent SWC estimates. We conducted the present study in the southwest of France on two plots that are part of the ICOS ERIC network (Integrated Carbon Observation System, European Research and Infrastructure Consortium), FR-Lam and FR-Aur. We propose a simple protocol for soil-specific calibration, particularly suitable for clayey soil, to improve the accuracy of SWC determination when using commercial FDR sensors. We compared the sensing accuracy after soil-specific calibration versus factory calibration. Our results stress the necessity of performing a thorough soil-specific calibration for very clayey soils. Hence, locally, we found that factory calibration results in a strong overestimation of the actual soil water content. Indeed, we report relative errors as large as + 115 % with a factory-calibrated sensor based on the real part of dielectric permittivity and up to + 245 % with a factory-calibrated sensor based on the modulus of dielectric permittivity. [ABSTRACT FROM AUTHOR]

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

THE PRESENT WORK aims to modify Fredlund and Xeng (FX) model to simulate the soil water characteristic curve (SWCC) to be applicable in soil physics and agriculture. Laboratory measurements of the SWCC of clay soil, representing the soil type close to river Nile in Egypt, were carried out using a pressure plate extractor. The measured points of the curve include saturation, field capacity (FC), and permanent wilting point (PWP). The estimation of the regression equations and unknown parameters was performed using non-linear estimation in the STATISTICA program through user-specified regression. The flexibility and capability of the proposed equation (PE) for a wide range of soil suction (ψ) values and soil types were also determined. The SWCC of the experimental soil and statistical tools indicated that PE showed a very good fit to the measured data. The three compared models accurately simulated the entire range of SWCCs for different soil textures. The statistical analysis and fitting curves revealed that the PE precisely simulated the SWCCs for the entire range of ψ values for different soil types and performed better than MVG and FX. Furthermore, only PE was able to simulate SWCCs using different forms of soil moisture, distinct from MVG and FX. The study hence recommends the use of the PE in simulating SWCCs. [ABSTRACT FROM AUTHOR]

This paper considers the use of radar and optical data from the Sentinel 1 and Sentinel 2 satellites for 2019–2020 to assess the humus content and the percentage of clay and moisture in the topsoil using the example of chernozems and gray forest soils of the Novosibirsk oblast. Particular attention is paid to the selection of satellite images, because in order to quantify the humus content and clay in the soil, it is necessary to fulfill the conditions for the soil to be dry and bare. The humus content is estimated for five test sites based on a regression model (Karavanova and Orlov, 1996), which includes surface reflection coefficients at the wavelength of the B6 spectral channel of the Sentinel 2 satellite. The model parameters are adjusted for the conditions of the study area separately for chernozems and gray forest soils. The percentage of physical clay in the soil is estimated using Sentinel 2 optical data, ground measurements, and regression models with an exponential dependence of clay content on soil reflectances at the SWIR wavelengths of the Sentinel 2 spectral channels (Bousbih et al., 2019; Shabou et al., 2015). The change in the percentage of humus and clay content in the test sites of soils over the year is shown according to Sentinel 2 data. The topsoil moisture content is estimated based on radar, optical, and the combined use of radar and optical data. [ABSTRACT FROM AUTHOR]

Determining the best management practices (BMPs) for farmland under different soil textures can provide technical support for improving maize yield, water- and nitrogen-use efficiencies (WUE and NUE), and reducing environmental N losses. In this study, a two-year (2013–2014) maize cultivation experiment was conducted on two pieces of farmland with different textural soils (loamy clay and sandy loam) in the Phaeozems zone of Northeast China. Three N fertilizer treatments were designed for each farmland: N168, N240, and N312, with N rates of 168, 240, and 312 kg ha−1, respectively. The WHCNS (soil Water Heat Carbon Nitrogen Simulator) model was calibrated and validated using the observed soil water content, soil nitrate concentration, and crop biological indicators. Then, the effects of soil texture combined with different N rates on maize yield, water consumption, and N fates were simulated. The integrated index considering the agronomic, economic, and environmental impacts was used to determine the BMPs for two textural soils. Results indicated that simulated soil water content and nitrate concentration at different soil depths, leaf area index, dry matter, and grain yield all agreed well with the measured values. Both soil texture and N rates significantly affected maize yield, N fates, WUE, and NUE. The annual average grain yield, WUE, and NUE under three N rates in sandy loam soil were 8257 kg ha−1, 1.9 kg m−3, and 41.2 kg kg−1, respectively, which were lower than those of loam clay, 11440 kg ha−1, 2.7 kg m−3, and 46.7 kg kg−1. The order of annual average yield and WUE under two textural soils was N240 > N312 > N168. The average evapotranspiration of sandy loam (447.3 mm) was higher than that of loamy clay (404.9 mm). The annual average N-leaching amount of different N treatments for sandy loam ranged from 5.1 to 13.2 kg ha−1, which was higher than that of loamy clay soil, with a range of 1.8–5.0 kg ha−1. The gaseous N loss in sandy loam soil accounted for 14.7% of the fertilizer N application rate, while it was 11.1%in loamy clay soil. The order of the NUEs of two textural soils was: N168 > N240 > N312. The recommended N fertilizer rates for sandy loam and loamy clay soils determined by the integrated index were 180 and 200 kg ha−1, respectively. [ABSTRACT FROM AUTHOR]

Many studies have shown that climatic and edaphic factors influence the variations in nitrogen isotopes (δ15N) in terrestrial ecosystems. However, the relative importance of co-varying climatic and edaphic controls on plant δ15N remains somewhat unclear. To address this issue, regional-scale plant (L. chinensis) and soil samples were collected along a longitudinal transect across the temperate grasslands in northern China. The influences of climatic and edaphic factors on the plant δ15N were disentangled using the variable importance in projection (VIP) approach. We found that the climatic and edaphic variables explained 52.4% and 31.2%, respectively, of the variation in plant δ15N. The mean annual precipitation (MAP), soil N, and mean annual temperature (MAT) were the most important variables, but the soil water content (SWC), aridity index (AI), and soil clay content were also important variables. The soil pH and soil C: N ratios were identified as unimportant variables. Furthermore, a high-performance model for simulating plant δ15N values was constructed based on the important variables (VIP > 0.8). Further investigations should focus on the effects of the interaction between the climatic and edaphic variables on the N cycles in the temperate grasslands to provide more reliable predictions of plant δ15N. [ABSTRACT FROM AUTHOR]

This study developed a comprehensive database of soil physical properties to expand the potential applications of soil moisture observations across the Kansas Mesonet environmental monitoring network. The database comprises 14 site‐ and depth‐specific soil hydraulic properties for 40 stations monitoring soil water content. The measured soil hydraulic properties include sand, clay, and silt contents; bulk density; particle density; total porosity; effective saturation; saturated hydraulic conductivity; and water retention at six matric potentials. The soil database spans eight soil textural classes, with silty clay loam, silt loam, and silty clay soils dominating the fine‐textured soils, and sandy loam and sandy clay loam soils comprising the only coarse‐textured soils. All the measured soil hydraulic properties showed low coefficient of variation (CV ≤10%) within soil textural classes, except for the saturated hydraulic conductivity, which varied from a median of 0.520 ± 308 cm d–1 in the clay soils to 47.1 ± 119 cm d–1 in the sandy loam soils. The uncertainty of the Kansas Mesonet soil water content observations was reduced by at least 29% using laboratory sensor calibration equations instead of the factory default sensor equation. Our soil physical property database offers new prospects to use historical and near real‐time in situ soil water content observations across the Kansas Mesonet for diverse agricultural and hydrological applications, including drought monitoring, wildfire preparedness, and estimating potential drainage and groundwater recharge rates. Core Ideas: This study developed a comprehensive soil physical property database for the Kansas Mesonet.The database comprises 14 site‐ and depth‐specific soil hydraulic properties for 40 stations.The soil database is dominated by fine‐textured soils with 92% of the soils having >20% clay content.Laboratory sensor calibration equations reduced the uncertainty of the water content measurements by at least 29%. [ABSTRACT FROM AUTHOR]

Based on the soil temperature and humidity data of soybean farmland under conservation tillage in Northeast China in the published article, the impact of conservation tillage measures on the soil hydrothermal status of soybean farmland in Northeast China was quantitatively assessed by using conventional tillage (CT) as a control, no-tillage (NT), reduced tillage (RT), straw mulching (SM), and no-till straw mulching (NTSM) as treatments. The results showed: compared with CT, conservation tillage increased the soil volume water content of 0-170cm soil layer in soybean farmland in Northeast China by 9.2%, and reduced the temperature of the shallow soil layer (0-30cm) by 8.2%. Four conservation tillage could increase soil moisture under different climatic conditions; straw mulching could increase soil moisture content throughout the growth period of soybeans, and the effect on soil hydrothermal was greatest during the nutrition period of soybean, and soil temperature increased with the increase of straw mulching; the magnitude of soil temperature reduction by conservation tillage decreases with the decrease of soil clay particles, the magnitude of soil moisture increased by conservation tillage decreases with the increase of soil depth. Among them, NTSM at different soil depths was the most obvious effect of water storage and moisture retention, and the soil moisture in the soil layer of 0-20cm was increased by 32.9%. In summary, conservation tillage could increase soil moisture but reduce soil temperatures. Temperature, precipitation, growth period, straw mulching amount, soil type and soil depth all had an impact on soil hydro-thermality in soybean farmland under conservation tillage. [ABSTRACT FROM AUTHOR]

A new method is proposed to recover the electric properties and water content of ground soil by applying the Target Decomposition (TD) theory for Polarimetric Synthetic Aperture Radar (PolSAR) images. The proposed method depends on the e-s characteristic curves of the soil which are unique for each soil type at a specific frequency. This method is examined for the clayey type soil which is found in most naturally vegetated land areas. Also, a novel method is developed for the realistic simulation of PolSAR images of natural lands, including forest regions, grasslands, and bare lands being prepared for gardens or crop cultivation. This method is based on the reverse of the PolSAR TD theory. The numerical results presented in this paper are concerned with the characterization of the most common type of clayey soil. Also, some of the numerical results presented in the present paper aim to achieve realistic PolSAR datasets using the inverse TD theory. Finally, some numerical results are presented for quantitative assessment of the method proposed to recover the properties and water content of the clayey soil using the datasets which are obtained through realistic simulations of forested areas, gardens, grasslands, and bare lands being prepared for cultivated plants. It is found, through the numerical investigations and quantitative assessment, that the dielectric constant, electric conductivity and water content of the investigated clayey types of soil are accurately estimated. [ABSTRACT FROM AUTHOR]

Grouser height and soil moisture content have a significant effect on the tractive performance of tracked vehicles. Paddy soil has the mechanical properties of both clay soil and sandy soil and can have a wide range of water content values, and it has a considerable influence on the tractive performance of tracked agricultural machinery. To study the influence of grouser height on the tractive performance of a single-track shoe under different soil moisture contents, a three-dimensional shearing model of the single-track shoe and the contact soil was established based on the ground vehicle mechanics theory, and an experimental platform with a soil bin, sensors, and a control system was established. Six preset levels of moisture contents (7%, 12%, 17%, 22%, 27%, and 32%) of paddy soil were prepared for the research experiment. The mechanical properties of the soil with different moisture contents were obtained through the use of a direct shear test, penetration test, and compaction test. The obtained physical parameters of the soil have special characteristics that are different from typical soil. Combined with the three-dimensional model and the obtained soil parameters, the parameters of the tractive performance, such as thrust, running resistance, and traction with different moisture contents were analyzed and calculated. The test results revealed that the thrust at different grouser heights shows a regular waveform growth trend with an increase in soil moisture content. The minimum value and the maximum value of thrust were obtained at moisture contents of 7% and 12%, respectively. The curve of different grouser heights of the running resistance shows similar changes with different moisture contents. The two peak points and inflection points of the fluctuation curve are for moisture contents of 17% and 27%. The change curve of the traction is highly similar to the curve of thrust. The maximum value of the traction was found at a moisture content of 12%, and the minimum value at 22% or 27%. Under different moisture conditions, tracked vehicles with higher grousers have better tractive performances. [ABSTRACT FROM AUTHOR]

The shear characteristics of the interfaces between soil and concrete structures are essential for the safety of the structures. In this study, a large-scale direct shear test apparatus was developed to measure the mechanical parameters of soil–concrete interfaces under conditions with different soil types, soil moisture contents, and interfacial filling materials. The results showed that the shear stress of the soil–concrete interface increased initially and then became stable with the increase in the shear displacement. The shear displacement of the sandy soil when the shear stress became stable was smaller than that of the clayey soil. The silty sand–concrete interface had a smaller friction angle than the interface with the medium-coarse sand. Moreover, with the increase in the soil moisture content, the friction angle of the clayey soil–concrete interface decreased rapidly, whereas the cohesion first increased and then decreased, and the peak cohesion was near the plastic limit of the soil. Under the same moisture content, the friction angle and cohesion of the clay–concrete interface was reduced by filling the interface with a thin layer of sandy soil, while filling the silty sand–concrete interface with a thin layer of silt reduced the friction angle and increased the interfacial cohesion. Nonetheless, the filling had little impact on the overall shear strength of the interface. [ABSTRACT FROM AUTHOR]

The determination of the coefficient of linear extensibility (COLE) of soils is crucial for enhancing structural stability in civil engineering applications. Traditional methods for measuring COLE have some practical limitations. In routine soil analyses, clay and soil organic carbon (OC) are often measured, while soil hygroscopic water content (wh) is easy to determine on several soil samples simultaneously. The aims of the study were to (1) utilise two data partitioning approaches to develop regression models that estimate the soil COLE from hygroscopic water content, clay and OC contents, and (2) compare the model performance of the developed regression models. We used two data partitioning approaches. First, the calibration models were developed on 53 soil samples from Slovakia and validated with 24 soil samples from the United States (country‐wise). Second, the calibration models were built from 67% of the entire dataset and validated with 33% (mixed data). Regression models based on hygroscopic water content accurately estimated COLE regardless of sorption direction or data partitioning approach (RMSE: 0.014–0.023 cm cm−1). The inclusion of OC in multiple linear regression models of clay only marginally improved COLE estimation compared to clay alone. For all models, the mixed data partitioning method showed better model validation performance than the country‐wise approach. The COLE classes derived from the estimated COLE values compared favourably (72%–94% accurate) to the measured data. Thus, there is a great potential to estimate the COLE from readily available (clay and OC) or easily measurable (hygroscopic water content) soil properties. Highlights: Hygroscopic water content (wh) is intimately linked to soil properties that determine COLE.Regression models based on wh or clay, and organic carbon content accurately estimated COLE.Data partitioning approach for modelling significantly impacted model performanceSamples with very high COLE were better estimated by wh‐based models than by other variables [ABSTRACT FROM AUTHOR]