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Considerable quantities of pyrophosphate and orthophosphate are introduced to soils as fertilizers and fire retardants. While the fate of orthophosphates added to soils has been extensively studied, less attention has been paid to the behaviour of pyrophosphates in soils. In this work sorption edge and surface charge measurements of orthophosphate and pyrophosphate by boehmite and kaolinite, were conducted at 10, 25 and 50 °C between pH 3.5–11.5. Pyrophosphate and orthophosphate sorption edges differ significantly, showing greater quantities of phosphorous as pyrophosphate sorbed by the minerals in lower pH. Boehmite consistently had higher pyrophosphate uptake across the three temperatures compared to kaolinite. For kaolinite, temperature changes had a more pronounced influence on pyrophosphate sorption. Temperature increases also shifted boehmite point zero charge to lower pH. Analysis of pyrophosphate isotherm data suggests outer-sphere electrostatic attraction is the principal interaction between absorbent and absorbate material at pH 8. The difference observed in sorption results indicate that the type and structure of various phosphates will affect sorption to different mineral types and stresses the importance of studying pyrophosphate sorption processes under a range of environmental conditions. [Display omitted] • The minerals removed more phosphorus when applied as pyrophosphate compared to orthophosphate. • Orthophosphate and pyrophosphate both showed higher affinity to boehmite than to kaolinite. • Temperature effects were more pronounced in pyrophosphate sorption to kaolinite compared to boehmite. • The results show the importance of studying the sorption of different phosphate species by soil clays and minerals. [ABSTRACT FROM AUTHOR]

[Display omitted] • CMC-S-nZVI synthesized by two methods can effectively dechlorinate soil-sorbed TCE. • CMC, a common nZVI stabilizer, can facilitate release of TCE from soils. • Soil particles promoted iron corrosion through taking Fe2+ from CMC-S-nZVI surface. • Soil particles blocked the CMC-S-nZVI surface during extended reactions. Carboxymethyl cellulose stabilized and sulfidated nano zero-valent iron (CMC-S-nZVI) can efficiently degrade trichloroethene (TCE) in water. However, little is known about the interaction between CMC-S-nZVI and TCE in soils. Here we studied the effects of two soils, a sandy (LY) and a sandy-loamy soil (DXAL), on TCE dechlorination by two types of CMC-S-nZVI particles. Continuous dechlorination of soil-sorbed TCE was observed for up to 96 h. LY and DXAL soil sorption suppressed 24-h dechlorination by 5–16 % and 25–51 %, respectively, although CMC significantly enhanced TCE release from the soils. Soil clay minerals, including Fe/Mn oxides and organic matter, promoted iron corrosion during the initial stage (< 8 h and < 2 h for the two particle types) through uptake of Fe2+ from the CMC-S-nZVI surface, but inhibited corrosion and TCE dechlorination at the later stage by blocking surface reaction sites, thereby hindering electron transfer. The dual effects of soil were more evident in DXAL, due to its higher content of clays and organic matter. Our findings show that CMC-S-nZVI can effectively dechlorinate soil-sorbed TCE, but reductant demand and the blocking effect from the soil should be considered to optimize engineering designs at TCE-contaminated sites. [ABSTRACT FROM AUTHOR]

• Spatialized data were used for a more accurate analysis of hopyard production traits. • A weak negative relation was found between clay content of the soil and hop yields in a Mediterranean environment. • Shoot production before training was positively and strongly related to cone yield of cultivar Cascade. • Cultivar Cascade proved to be well adapted to the Mediterranean environment. • Organic hop production is feasible under the Mediterranean climatic conditions. The cultivated hops are recently moving towards new growing areas in Southern Europe, boosted by the increasing number of craft breweries and by the higher vulnerability to climate change observed, for this crop, in the traditional growing regions. Despite this clear market and geographic trend, there is a lack of knowledge about pedoclimatic needs and agronomic performances of hops grown in the Mediterranean environment. Particularly, the agronomic potential of a new hopyard during its establishment period is poorly studied even in traditional growing zones. Moreover, a restricted number of plants were usually sampled to gather the few data available, thus leading to a probable overestimation of yield performance. A commercial organic hopyard in central Italy was established and a 2-year (2018–2019) field experiment was set-up to accurately investigate the cone and shoot yield potential of cultivar 'Cascade' and to understand how such yields are related to each other and to soil texture. Hop plants were two-years old when the experiment started; plant population was 4,000 plants ha−1. Forty points within the hopyard were sampled for soil analysis and yield traits. Data were analyzed accounting for spatial dependence of the sampling points. Results show a negative relation between clay content in the soil and hop yields, even though it was significant only in the exceptional rainy season of 2018. Shoot and cone yield were positively and strongly related, suggesting the green shoot yield in spring as a good predictor of hop production. Both shoot and cone yield significantly increased from the second to the third year (+11% and +16%, respectively); however, the unseasonably high rainfall of 2018 probably lowered the yield of the first experimental year. Cone yield attained over this 2-year study (1.24 t ha−1 and 1.44 t ha−1 for 2018 and 2019, respectively) was within the published ranges for mature plants. Similarly to cone production, shoot dry matter yield was lower in 2018 (197 kg ha−1) than in 2019 (218 kg ha−1). This study provides the first reliable information on both cone and shoot yield potential of a young organic hopyard under Mediterranean climatic conditions. [ABSTRACT FROM AUTHOR]

Understanding the differential fertilizer N fates among soil textures is important to optimize crop nitrogen (N) management for reducing N losses while enhancing crop yields and N use efficiency. In this study, two-year field experiments were conducted on three contrasting soil textures (clay, sandy and loamy soils) with an identical climate in Northeast China, to quantify fertilizer N fates in the maize cropping system and evaluate their responses to N rates (168, 240, and 312 kg N ha−1) under different soil textures using 15N tracer technique, further to model fertilizer N fates with soil properties using multiple linear regression. In two seasons, both grain yields and plant N accumulation were the highest on loamy soil, followed by clay soil, while the lowest on sandy soil. Compared with loamy and clay soils, the plant N accumulation derived from fertilizer (Ndff%) was significantly higher (47 %) on sandy soil in the 1st season, meanwhile its poor soil structure increased environmental N losses (ENL) while decreasing crop N recovery (CNR) and soil N residual (SNR); together with higher in-season ENL, this further significantly lower Ndff% (6%) on sandy soil in the 2nd season. Relative to loamy soil, the SNR on clay soil was significantly higher in both seasons due to the denser and heavier soil texture, but its CNR was lower in the 1st season while both CNR and ENL were higher in the 2nd season. Throughout two growing seasons, the total CNR of loamy, clay and sandy soil was 44 %, 34 % and 28 %, the total ENL was 41 %, 46 % and 64 %, and the final SNR was 15 %, 20 % and 8 %, respectively. With increasing N rates, total CNR decreased while final SNR increased on all three soils, and ENL increased in the 1st season but decreased in the 2nd season. Moreover, the N responses of CNR and SNR were higher on sandy soil, indicating that its fertilizer N fates were more susceptible to N rates. Therefore, crop N management strategies are required to be adjusted according to differential fertilizer N fates among soil textures. By establishing the model between fertilizer N fates with soil properties and N rates, we provided a promising approach to understand and predict fertilizer N use and loss for precisely optimizing N managements on different soil textures. [Display omitted] • Crop 15N recovery was higher on loamy soil (43.8 %) relative to clay soil (34.4 %) and sandy soil (28.1 %). • Soil 15N residual was higher on clay soil (19.6 %) relative to loamy soil (14.9 %) and sandy soil (7.6 %). • Total 15N loss was higher on sandy soil (64.3 %) relative to clay soil (46.0 %) and loamy soil (41.2 %). • The higher Ndff in 1st year but the lower Ndff in 2nd year were obtained on sandy soil than other soils. • Modelling the relationships between fertilizer 15N fates and the soil structure and N rates. [ABSTRACT FROM AUTHOR]

There is a clear nonlinear characteristic of the seepage velocity of clay; however, its existing prediction models are mostly empirical, and the prediction accuracy needs to be improved. In this paper, the soil–water retention curve is considered an indirect indicator reflecting the scale distribution of the soil seepage channel to calculate the initial hydraulic gradient of the microscopic seepage channel, based on which a nonlinear seepage velocity prediction model for clay soils was established in combination with the Tao-Kong model. To verify this model, the saturated seepage velocity of three dry densities of Hunan clay under different hydraulic gradients was measured with a GDS permeameter. Using the new model, the saturated seepage velocity under different hydraulic gradients was predicted and compared with experimental results and prediction results from existing models. The comparison showed that the new model has the highest accuracy. Both the prediction and experimental results showed that seepage in Hunan clay exhibits a nonlinear behavior and has an initial hydraulic gradient. When the seepage pressure is small, the permeability coefficient is small; as the seepage pressure increases, there is a steep increase in stair, and the larger the dry density is, the larger the initial hydraulic gradient. [ABSTRACT FROM AUTHOR]

• Contribution of organic carbon (OC) to total specific surface area (SA) is unclear. • EGME SA correlated with water sorption SA, except for OC-rich soils. • OC contribution to SA depended on clay mineralogy and OC content. • OC contribution ranged from 7.5 to 13.9 m2/g per %C depending on clay mineralogy. • For samples rich in montmorillonite, OC negatively contributed to total SA. Soil specific surface area (SA) reflects the quantity and quality of the soil mineral and organic fractions. For soil samples that have similar clay mineral types, clay content and or organic carbon (OC) contents are good predictors of SA. However, the magnitude of the OC contribution to SA for different soil types is unclear, particularly since SA varies depending on which method or probe molecule is used to measure it. Consequently, we set out to (i) quantify the contribution of soil OC to total SA for soils with varying clay mineralogy, and (ii) assess the effect of probe molecule (EGME or H 2 O) and water sorption direction on the contribution of OC to the total SA. We utilized 330 soil samples (clay = 1 to 89 %; silt = 2 to 78 %; OC = 0.03 to 34.9 %) that were grouped according to clay mineralogy and OC content. The total SA was measured using EGME adsorption (SA E) and water adsorption and desorption (SA H2O). The contribution of OC to SA was examined using regression and partial correlation analyses that combined clay, silt, and OC as explanatory variables. Results showed that SA E values were strongly correlated to SA H2O , except for OC-rich soils where SA E was significantly lower than SA H2O. Apart from montmorillonite-rich samples, OC contribution to SA E was smaller than for SA H2O. Organic carbon had a positive contribution to desorption SA H2O for all sample groups, except for montmorillonite-rich samples; OC contribution was 7.5, 10.7, and 13.9 m2/g per %C for illite-rich, kaolinite-rich and OC-rich samples, respectively. There was no significant effect of water sorption direction on the OC contribution to SA H2O. Partial correlation analyses that accounted for clay and silt contents confirmed a negative contribution of OC to SA E or SA H2O for soil samples dominated by montmorillonite clay minerals. We can conclude that for the soil types investigated here (except montmorillonitic soils), OC has a positive contribution to total SA, and the magnitude of the contribution depends on the clay type. [ABSTRACT FROM AUTHOR]

• Soil acidification rates and dissolved organic C fluxes were quantified on permafrost. • Fluxes of dissolved organic C were higher in clayey soils with shallow active layer. • Nitrate-N fluxes were higher at lower slope position even in arctic soils. • Cation uptake by lichen and moss as well as higher plants leads to soil acidification. • Climate warming has potential to increase active layer thickness and soil acidification. Climate warming is predicted to change the fluxes of dissolved organic matter and nitrate by increasing active layer thickness, plant productivity, and organic matter decomposition. These changes are hypothesized to increase mineral weathering and soil acidification rates. We investigated whether acidification rates and solute leaching fluxes are variable between permafrost-affected soils with different active layer thicknesses. We compared the fluxes of dissolved organic carbon (DOC) and total dissolved N and the ion fluxes associated with solute leaching and plant uptake to calculate proton budgets in the soils that differed in slope positions (upper slope and lower slope) and soil texture (clayey and sandy soils) in NW Canada. We found the wide variation in DOC and nitrate-N fluxes, depending on slope positions and soil texture. The nitrate-N fluxes were higher at the lower slope position of the sandy soil, compared to the upper slope position. Compared to sandy soils, the DOC fluxes from the organic horizons were higher in the clayey soils on shallower permafrost table. Organic acids were major proton sources in the organic horizons at all sites, but acidity was also contributed by nitrate (sandy and clayey soils at lower slope position) and carbonic acid (clayey soil at upper slope position). The weathering by carbonic acid lead to accumulation of short-range-order minerals in the clayey soils, while incipient podzolization of the sandy soils included the weathering of illite to vermiculite and the dissolution of short-range-order minerals. The shallower active layer thickness at the lower slope position resulted in lower plant productivity and acidification rates. In the permafrost-affected soils, the active layer thickness, the DOC and nitrate-N fluxes, and their contribution to acidification are dependent on the local variation in slope position and soil texture, as well as climate change. [ABSTRACT FROM AUTHOR]

• Na- and Ca-montmorillonite contents of the clay mixtures were estimated using visible-near-infrared (Vis-NIR) spectra. • Partial least square regression (PLSR) models well estimated Na- or Ca-montmorillonite contents of the clay mixtures. • PLSR models estimated Na- or Ca-montmorillonite content of bentonite samples. • PLSR models performed better than single regression (SLR) and multivariate (MLR) regression models. The aim of this study was to evaluate whether Na- and Ca-montmorillonite and the swell-indicating properties (i.e., free swell index, water uptake capacity, and cation exchange capacity (CEC)) of clay mineral mixtures can be estimated using visible-near-infrared (Vis-NIR) spectral features. The data regarding four types of reference clay minerals (KGa-1b, kaolinite; IYd, illite; SWy-3, Na-montmorillonite; STx-1b, Ca-montmorillonite) and binary and ternary mixtures of the reference clay minerals (SWy-3/KGa-1b/IYd, and STx-1b/KGa-1b/IYd) with specific mass percentage ratios were used as a calibration dataset. The absorption spectral features could be correlated well with changes in the clay mineral content of the mixtures. The leave-one-out cross-validation results showed that the partial least square regression (PLSR) calibration models produced the best prediction in the following order: Na or Ca-montmorillonite, kaolinite, and illite amounts in the mixtures. The calibration models produced better predictions in the ascending order of CEC, free swell index, and water uptake capacity, regardless of the multivariate statistical methods and type of exchangeable cations in montmorillonite. Validation using an independent dataset indicated that the PLSR model predicted the Na- and Ca-montmorillonite content in clay mineral mixtures and bentonite samples. The results of this study provide the possibility of using Vis-NIR absorption spectral features as a screening tool for predicting the montmorillonite content with different interlayer cations in relatively pure clay soils (e.g., bentonite), if the calibration model is developed using the specific montmorillonite contained in the clay soil of interest. [ABSTRACT FROM AUTHOR]

Conservation systems, such as no-tillage, follow as principles the absence of soil tillage, formation and maintenance of vegetation cover, and crop rotation. Nevertheless, when one principle is not adequately adopted there may be alterations in soil aggregation and porosity. Thus, this study aimed to evaluate physical attributes and organic carbon of the soil in an area with tillage and fallow in the off-season and in areas without soil tillage, with fallow and with crop in the off-season. The soil of the three areas was characterized as an Oxisol with clayey texture. For more than 10 years, corn has been the main crop grown in the season period in the three areas: conventional soil tillage system with fallow in the off-season (CTS), no-tillage system with fallow in the off-season (NTS-f), and no-tillage system with grass-grass succession (NTS-g). Each area was sampled at 20 random points and soil samples were collected from the layers, 0–0.1 m, 0.1–0.2 m and 0.2–0.3 m. The data were subjected to multivariate factor analysis, where two factors were identified, called "soil aggregation" and "soil porosity". Through the "soil aggregation" process, it was found that clay is essential for the formation of aggregates with diameter of up to 2.0 mm, while soil organic carbon influences the formation of macroaggregates. The "soil aggregation" was higher in the area under NTS-g, and lower in the areas under NTS-f and CTS. The practice of fallow in the off-season in a no-tillage system proved to be harmful to soil structuring, especially in relation to soil aggregation. In the area under CTS there was greater "soil porosity" in the 0–0.1 m layer, but this effect is temporary, due to the large amount of microaggregates generated in this system, which over time obstructs soil pores and causes lower porosity than that determined under the no-tillage system. • Cultivation in the off-season is crucial for the structuring of the soil in a no-tillage system. • Off-season fallow in no-tillage system s is as harmful to soil aggregation as in the conventional tillage system. • In clayey soil, the clay is essential for the formation of aggregates with diameter less than 2.0 mm. • The soil porosity is higher in the conventional tillage system due to soil tillage operations. [ABSTRACT FROM AUTHOR]

The expansion of irrigation infrastructure in Tasmania, Australia, has led to intensified irrigated crop production, including for vegetables. This has resulted in increased irrigation of texture contrast soils, and other soils with high clay content in the subsoil. Widely used for rain-fed grain production in other parts of Australia, these soils have been subject to a range of soil amelioration approaches in an effort to improve their soil physical characteristics and capacity to produce crops. Subsoil manuring – the process of placing organic soil ameliorants at a target depth using a specially modified deep ripper – has proven to be successful in increasing yields of rain-fed grain crops. Locally available organic materials (chicken manure and poppy seed meal) were placed in the upper zone of a clay subsoil at three sites used for irrigated vegetable production. The crops grown were green peas for processing and carrots for seed production. Normal grower management practices were the reference against which treatments were compared. Subsequent measurements showed no consistent or significant benefit from subsoil manuring one year after treatment under the soil and crop management conditions used in this research. • Subsoil manuring has shown productivity benefits in rain-fed grain production. • Irrigated vegetables were grown on treated texture contrast and high clay soils. • No significant differences were found as a result of subsoil manuring treatments. [ABSTRACT FROM AUTHOR]

• Length dependent rill erosion processes seemed to be different on gentle slopes. • Equilibrium sediment transport was reached on the rills >7 m length under Q L. • Rolling of coarse particles affected by flow rates and rill length was evidenced. • Continuous head-cuts formation along long rills was an important affecting process. • Steady C and Dr of the 1-m-rill deviated from the Foster-Meyer conceptual model. Understanding the dynamic mechanisms of rill erosion is vital for accurately modeling of soil erosion. In this research, rill erosion was experimentally studied using different rill lengths. A flume, 11 m long and 0.2 m wide adjusted to 3% slope, was used for constructing rectangular rills of 0.05 m width and six different lengths (1 to 12 m). The experiments were carried out on a clayey calcareous soil from a semiarid region under two flow rates of Q L = 0.025 and Q H = 0.045 L s−1. Temporal sediment concentrations (C) were measured at the rill outlet for 40 min and the sediment size distribution (PSD) was recorded twice during each test. The common decreasing trend of C was affected by both flow rate and rill length. The formation of head-cuts along the bed of long rills was an important erosion process affecting C and PSD. The compiled data were used to determine the exponential models' parameters of both C and soil detachment rate based on the steady, unsteady, and event-average values. While, the equilibrium sediment transport occurred by increasing rill length beyond 7 m under Q L , the tested rills under Q H were not sufficiently long for the flow to reach its maximum transport capacity at the gentle slope used and for the calcareous soil tested. Based on the sediment PSD, the selective transport of coarse particles was evidenced. Selectivity transport was affected by rill length reached its maximum at the rill length of 7 m. The findings provides better understanding of rill erosion processes for calcareous soils on gentle slopes in semiarid regions. Further research is needed for better understanding of the rill erosion processes on short gentle slopes to provide experimentally supports for the existing theoretical concepts of rill erosion models. [ABSTRACT FROM AUTHOR]

• Surface activity on chronically subsided relief was analysed in a coal mining region. • Overall subsidence of 4–9 m from 1966 to 2013 pre-determined near-surface displacements. • Tree-ring records from Larix decidua Mill. showed the strongest activity in the 1970s. • One-year compression wood was discussed as a specific dendrogeomorphic signal. • Extreme rainfall contributes to surface activity in an area with more clayey soils. Tree-ring records from sites affected by underground mining provide valuable data on the long-term development of subsidence troughs. However, due to complexity of local conditions, it is unclear whether the surface displacements are actually the result of mining operations or shallow landslides caused by extreme rainfall. This paper compares surface movements at two nearby sites in the Upper Silesian Coal Basin (Central Europe) that have been affected by underground coal mining. Dendrogeomorphic data on subsidence-related movements were obtained from 360 increment cores (90 trees) of European larch (Larix decidua Mill.). Subsidence between 1966 and 2013 was calculated from the corresponding digital elevation models and the actual morphometric parameters of the sites were related to tree-ring records. The effect of precipitation on surface displacements was evaluated using logistic regression models incorporating rainfall data from a nearby meteorological station and dendrogeomorphic event years. The subsidence at the edges of subsidence troughs (study sites) between 1966 and 2013 reached 4–9 m, which is relatively low compared to nearby (5 km radius) directly undermined sites with subsidence up to 22 m. Most events were dated to the 1930s, 1970s, 1990s, and late 2000s with a peak of activity in 1973 and other noteworthy events in 1986, 1995, and 2009. Event years at the site with a flatter topography, and more waterlogged and clay soils are well explained by higher triennial precipitation and higher Simple daily intensity index, suggesting a possible influence of near-surface displacements on the chronology of recorded events, whereas the elevated site with step-block topography showed no relationship between precipitation extremes and event years. We concluded that not only the time of mining operation, but also the site-specific conditions are crucial for characterization of surface displacements in the forested post-mining landscape. [ABSTRACT FROM AUTHOR]

This review article includes a description of additive manufacturing from its advantages and opportunities for the construction sector, highlighting the definition of a design methodology for cementitious material mixes suitable for 3D printing and the properties required of them. Included among the materials analyzed are conventional ones based on Ordinary Portland Cement (OPC) and non-conventional ones, with alkali-activated materials (geopolymers) to the fore. In United States, Europe and Asia this technology has interesting construction projects, however, in Latin America, 3D printing is still in the experimental phase, so it can be considered as a technology that is in the process of being adopted. The results obtained in the development and research phase in different countries such as Mexico, Brazil, Chile, Colombia, Guatemala, Peru, among others, are promising and it is projected as an industrial reality in the near future. This paper presents the main challenges and opportunities in implementing additive manufacturing. [Display omitted] • 3D technology could be considered to solve the current housing deficit in countries. • Locally available materials, native clays and soils, can be used in 3D printing. • Supplementary cementitious materials (SCM) and geopolymers can also be used. • 3D printing must be recognized as a construction method by the construction codes. [ABSTRACT FROM AUTHOR]

This paper addresses the modelling of cesium sorption in non-equilibrium and nonlinear conditions with a two-site model. Compared to the classical K d approach, the proposed model better reproduced the breakthrough curves observed during continuous-flow stirred tank reactor experiments conducted on two contrasted soils. Fitted parameters suggested contrasted conditions of cesium sorption between 1) equilibrium sites, with low affinity and high sorption capacity comparable to CEC and 2) non-equilibrium sites, with a fast sorption rate (half-time of 0.2–0.3 h), a slow desorption rate (half-time of 3–9 days) and a very low sorption capacity (0.02–0.04% of CEC). Comparison of EK sites densities with sorption capacities derived from the literature suggests that the EK equilibrium and kinetic sites might correspond to ion exchange and surface complexation of soil clay minerals respectively. This work stresses the limits of the K d model to predict 137Cs sorption in reactive transport conditions and supports an alternative non-equilibrium nonlinear approach. • Cs sorption was studied on two soils with stirred flow-through reactor experiments. • Observed Cs sorption was influenced by flowrate and concentration. • The proposed two-site model described non-equilibrium and non-linearity effects. • Equilibrium sites had low affinity and high sorption capacity comparable to CEC. • Non-equilibrium sites had a fast sorption rate and a very low sorption capacity. [ABSTRACT FROM AUTHOR]

Desiccation cracks initiate and propagate during the drying process and healing occurs during the wetting process. However, most of the previous studies only paid attention to the drying-induced crack propagation and the wetting-induced healing behaviour was always neglected. In this paper, a series of wetting tests were conducted on cracked soils under different wetting rates. The crack pattern evolution during wetting was recorded and quantitatively analysed. The results show that the narrow and short secondary and tertiary cracks heal earlier than the long and wide primary cracks during wetting. With the elapsed wetting time, the surface crack ratio and average crack width decrease slowly at first, then rapidly decrease and eventually stabilise. However, at the early stage of wetting, the total crack length almost remains constant. The healing of desiccation cracks in clayey soils is mainly attributed by two factors: wetting-induced swelling and disintegration. Furthermore, the healing degree of desiccation cracks become higher with increasing wetting rate. The healing of desiccation cracks with a lower wetting rate is mainly due to the wetting-induced swelling of soils. However, that with a higher wetting rate is dominated by both swelling and disintegration. • The evolution of soil cracks subjected to various wetting rates was investigated. • The healing degree of desiccation cracks became higher with increasing wetting rate. • Wetting-induced crack healing at a low wetting rate is mainly due to soil swelling. • Both swelling and disintegration dominate the crack healing at a higher wetting rate. [ABSTRACT FROM AUTHOR]

Soil selenium is of great significance to human health. Soil-forming parent rocks are the most critical factor that influences soil Se levels. Chengmai County, Hainan Island, has a tropical climate and diverse types of parent rocks, in which soil Se content is high. This study investigated the vertical distribution of soil Se from various parent rock substrates under tropical climatic conditions, and the factors that influence these soil Se contents, with 69 vertical soil profiles covering Chengmai County. The vertical distribution of soil Se and correlations with CIA (chemical alteration index), Al 2 O 3 , TFe 2 O 3 (total iron oxide expressed as Fe 2 O 3), total iodine, SOC (soil organic carbon), and pH were analysed. As per the results, the mean ± standard error of Se content in the A, B, and C horizons was 0.88 ± 0.13 mg/kg, 0.77 ± 0.08 mg/kg and 0.45 ± 0.05 mg/kg, respectively. The parent rock strictly controlled the horizon distribution of Se in the A-horizon. Soil Se showed A-B-horizons-enrichment in the vertical profile, especially in soil profiles overlying granite and basalt. It is hypothesised that the Se enriched in soils developed from the Tuolie Formation due to the release of Se from the weathering process of Se-rich rocks. Meanwhile, Se in soils developed from granite and basalt is more closely associated with exogenous input. Another crucial factor for the high level of Se in Chengmai County is the tropical climate, which has led the rocks to generally undergo intense chemical weathering. This results in soils rich in clay minerals and Fe/Al oxyhydroxides, which easily absorb and retain Se. Furthermore, the Se content of the B-horizon was generally higher than that of the A-horizon due to leaching. These results provide further knowledge and understanding of the geochemical behaviour of soil Se and guide the evaluation of Se-rich land resources under tropical climatic conditions. [Display omitted] • Soil Se levels were high in the A, B, and C horizons in Chengmai County, Hainan Island. • Soil Se showed A-B-horizons-enrichment in the vertical profile. • The tropical climate is a crucial factor for the high soil Se content. • The distribution of Se content below the B horizon was most closely related to OM. [ABSTRACT FROM AUTHOR]

Accidental releases of highly saline produced water (PW) to land can impact soil quality. The release of associated salts can clog soil pores, disperse soil clays, and inhibit plants and other soil biota. This study explores a novel remediation technique using ferrocyanide to enhance the evaporative flux of soil porewater to transport dissolved salts to the soil surface, where crystallization then occurs. The addition of ferrocyanide modifies crystal growth that enhances salt transport, allowing salt efflorescence on the soil surface and physical removal. Release sites were simulated through beaker sand column experiments using two PWs collected from the Permian Basin. PW composition altered efflorescence, with up to ten times as much ferrocyanide required in PWs than comparable concentrations of pure NaCl solutions. The addition of EDTA reduced dissolved cation competition for the ferrocyanide ion, improving PW salt recovery at the soil surface. The speciation model, PHREEQC, was used to predict the onset of salt precipitation as a function of evaporative water loss and model the effect of aqueous ferrocyanide and EDTA speciation on efflorescence. The results highlight the utility of predictive modeling for optimizing additive dosages for a given release of PW. [Display omitted] • Evaporative flux remediation of soil is enhanced with crystallization modifiers. • Prussian yellow reduces salt crystallization in sands polluted with produced waters. • Single salt solutions oversimplify the behavior of real produced waters. • For some produced waters, remediation is enhanced with EDTA complexing agent. • PHREEQC is an effective tool for predicting crystallization during evaporation. [ABSTRACT FROM AUTHOR]

• Cover crop root-derived SOC influences aggregate stability in clayey red soil. • High root number and low lignin/cellulose result in high SOC and polysaccharides-C. • Fibrous root vetiver changes SOC and soil surface charge properties largely. • Lower repulsive soil net force leads to higher aggregate stability. Soil aggregate stability is influenced by soil organic carbon (SOC). However, the influence of SOC from different fall/winter cover crop roots (annual and perennial crops) on aggregate stability through soil internal forces (SIFs) (electrostatic repulsive force (P erf), van der Waals attractive force (P vdw), and surface hydration repulsive force (P h)) remains unclear. The objectives of this study were compare three fall/winter cover crops (lucerne, rapeseed, six-year-vetiver (Vet_6Y)) and two control (fallow and fallow with SOC removal (fallow-SOC-R)) to determine SOC effects red soil aggregation through SIFs. Plant root morphological and chemical traits, SOC properties, soil surface charge properties, soil internal forces and aggregate breakdown were all determined. The perennial crop (Vet_6Y) showed the highest root number density (0.21 counts cm−2), second highest root mass density (1.80 mg cm−3), and the lowest root lignin/cellulose ratio (0.69), and thus contributed to higher SOC content and SOC functional groups (mainly polysaccharide-C) than annual crops (rapeseed and lucerne). Such SOC traits in perennial vetiver resulted in a higher specific surface area (SSA), lower surface charge density and surface charge number (Q s) compared to annual crops (rapeseed and lucerne) and controls, and the relationship between the root, SOC and soil surface properties (i.e., SSA) was further confirmed by significant correlation (r ranging from 0.76 to 0.97). Ultimately, these soil surface charge properties after cover crops increased P vdw , decreased P erf , and thus decreased repulsive net force (P net) (the sum of P vdw , P erf , and P h) and the average repulsive net force displayed in order of fallow-SOC-R (2.77 MPa) > fallow (2.11 MPa) > lucerne (2.02 MPa) > rapeseed (1.78 MPa) > Vet_6Y (1.45 MPa) at a distance of 1 nm. This resulted in the mass percentage of released small particles (<20, <10, and <2 µm) w (< d) % from aggregate being reduced after cover crops compared to controls. Generally, clayey red soil aggregate stability can be improved by decreasing the repulsive soil P net through cover crop root contribution to SOC and SOC-functional groups. [ABSTRACT FROM AUTHOR]

• Soil erosion modulus of the large-scale gullies increased from north to south. • Hydraulic erosion dominated gully development during one-year monitoring period. • Contribution of gravity erosion to the gully was ascribed to hypsometric integral. • Clay in colluvial deposits contributed to regional difference of gully erosion. Gully erosion is the most serious threat to sustainable development of global ecosystem and economy, with declining soil productivity and fertility threatening agricultural production. However, due to limitations in quantifying gully erosion rate, origin of erosion could be hardly distinguished. This study aimed to figure out this problem by developing a soil erosion estimation method based on unmanned aerial vehicles (UAV) monitoring techniques. Specifically, 18 gullies with different terrain characteristics were selected across typical erosion regions in southeast China, and UAV low-altitude photography, weather station monitoring, and field sampling investigation were conducted from 2020 to 2021to monitor their total erosion volume (VE), collapse volume (VC), proportion of collapse volume to total erosion volume (VC%), morphological parameters (e.g., total length of scour channels, L; erosion area, A; residual volume, V; and hypsometric integral) and soil-environmental factors (rainfall, temperature, and soil properties). It showed that 92.65 % of VE was resulted from colluvial deposits, attributing to the variation of L. Additionally, VC quantifying the amount of gravity erosion was determined by soil clay content in the upper catchment (Clay1). And percentage of VC to VE, characterized by VC%, possessed a significant linear correlation with HI (R2 = 0.571, p < 0.001). Moreover, regional differences of VE and VC was mainly attributed to soil clay content in colluvial deposits (Clay3) and HI. Collectively, clay content in the gully system inhibited gully erosion, while all the morphologic factors facilitated the development of gully erosion. Meanwhile, rainfall and temperature had significant impacts on VE and the regional difference of VC, probably due to the limited monitoring period. [ABSTRACT FROM AUTHOR]

The applications of helical piles have grown significantly and they have become more popular for construction, especially as a potential offshore foundation system in recent years, owing to their distinct benefits over alternative systems. Helical piles may be installed in groups to support heavy loads; therefore, a reliable design requires an accurate assessment of their behavior. The present study used finite element modeling to extensively analyze the uplift and lateral behavior of group piles installed in soft clay soil. The problem was modeled using Plaxis 3D software, and the model was validated using laboratory scale model test data. The validated model is then utilized to investigate the group effect for three distinct configurations, namely rectangular, triangular, and square patterns, with helical piles placed at varied center-to-center spacing's. The term "group efficiency" is used to describe the group effect of each group on the ultimate capacity. The findings showed that the group efficiency is significantly influenced by the number of piles, center-to-center pile spacing, and the failure criteria assumed to interpret test data. The load-transfer mechanism was also investigated and reported for varying group configurations. Finally, for the assumed failure criteria, the provision of an optimum spacing ratio is suggested for both tensile and laterally loaded group helical piles. • Assumed failure criteria substantially affect group behavior and predicted performance. • The group effect becomes insignificant under uplift and lateral loading when the pile spacing exceeds 3D. • As the group size increases, the uplift and lateral group capacities also increase. • The displacement contours are significantly affected by the helical pile spacing ratio (S g /D) and configuration types. [ABSTRACT FROM AUTHOR]

• The influence laws of multiple factors on soil/metal adhesion are present. • The influencing mechanism of soil/metal interface adhesion is analyzed. • The effect of compression pressure on adhesion stress is of vital importance. • A modified clogging risk diagram based on adhesion stress and I c is proposed. In order to effectively diminish clogging of EPB shield machines, it is an urgent need to systematically understand the soil/metal interface adhesion behaviours. Here, a series of piston pull-out tests are proposed to systematically understand the soil/metal interface adhesion behaviour by the optimal selection of clayey soils such as kaolinite, montmorillonite, bentonite and completely decomposed granite. For all of these clayey soils, the adhesion stress first increases and then decreases with an increase of water content, while it increases linearly with the increase of compression pressure. Besides, plating chrome as a hydrophobic layer could effectively decrease the adhesion stress of the clay. The influence of metal surface structure and compression time is limited. Based on the test results, we proposed a modified clogging potential assessment diagram with water content, adhesion stress, and compression pressure as reference indexes. Adhesion stress can be used as a reference index to evaluate the risk of shield clogging. The diagram is validated by four clayey soils. This work systematically reveals the soil/metal interface adhesion behaviours and evidently provides a reference index for reducing clogging of EPB shield machines. [ABSTRACT FROM AUTHOR]

Soil desiccation is a common physical phenomenon, which causes many geotechnical problems to unsaturated clayey soils. In this paper, a proposed model was incorporated into the original Discontinuous Deformation Analysis (DDA) to simulate the full desiccation process of a clayey soil from volume shrinkage to desiccation cracking and then to desiccation curling by focusing on soil suction. In this model, evaporation-induced soil volume shrinkage and suction-induced tensile failure were separately considered, in particular, soil suction was reasonably treated as an equivalent attractive force rather than a strength parameter. Then, a constrained desiccation test was simulated using the extended DDA model, and obtained numerical results were compared with the experimental results. The comparison results show that this model can capture the main features of the full desiccation process of the clayey soil. Moreover, the influences of soil suction and sample thickness on the desiccation cracking and curling were investigated, which agrees with the laboratory observations. This work aims to propose a novel yet simple model to reproduce the key characteristics of the soil's full desiccation process, and the results demonstrate that the extended DDA model can be served as a promising approach to analyzing the full desiccation process of clayey soils. [ABSTRACT FROM AUTHOR]

Urea is the most consumed nitrogen (N) fertilizer but is susceptible to high N losses that can result in lower crop yields compared to other N sources. The aim of this study was to evaluate the effects of the continuous usage of urea and calcium ammonium nitrate (CAN) at different N rates on cotton yield, fiber quality, nitrogen agronomic efficiency (NAE), and soil N stock. Two field trials were conducted across four seasons in two regions of Brazil with contrasting soil textures, with clayey and sandy loam soil. The experiment design consisted of two N sources (urea and CAN), four N rates (48, 96, 144, and 192 kg of N per hectare [kg ha−1]), a control plot (no N), and an additional treatment (different N split). Cotton was sown in the rainy summer season using the cultivars TMG 47 B2RF and DP 1536 B2RF, where rows were spaced 0.90 and 0.76 m apart, with densities of 100,000 and 90,000 plants ha−1, in the clayey and sandy loam soils, respectively. Climate conditions were favorable (>800 mm rainfall and 26ºC) during growing, and cotton yield ranged from 2514 to 5437 kg ha−1. Nitrogen application increased cotton yield for both N sources in clayey soil, but not in sandy loam, probably due to N mineralization and a low C/N ratio. In the clayey soil, the N addition at 192 kg ha−1 increased cotton yield by up to 50 % (3500 to 5300 kg ha−1 in the 2019 season) and increased the accumulated yield (4 years) from 12,000 to 16,000 kg ha−1 compared with control. Over the four seasons, CAN application resulted in a higher yield per unit of N compared with urea, resulting in means for NAE of 10.3 and 8.3 kg kg−1, respectively. The N addition improved the micronaire index from the base range, 4.3–4.8 micrograms per inch (control), to premium values of 3.8–4.3 and had no effect on other cotton quality properties or soil N stock. The management of N plays a major role in cotton production and quality, which depend on site-specific conditions. In the long term, yield responsiveness to N was intensified, which suggests that further differences may occur between urea and CAN. • Cotton yield increased by up to 50 % when applying 192 kg ha−1 of N in clayey soil. • The N addition had no effect on cotton yield in sandy loam soil due to soil N status. • Calcium ammonium nitrate resulted in a higher cotton yield per N applied than urea. • Split N application twice or three times resulted in comparable cotton yield and quality. • The N addition improved the micronaire index but had no effect on other quality traits. [ABSTRACT FROM AUTHOR]

• Cover crop root-derived SOC influences aggregate stability in clayey red soil. • High root number and low lignin/cellulose result in high SOC and polysaccharides-C. • Fibrous root vetiver changes SOC and soil surface charge properties largely. • Lower repulsive soil net force leads to higher aggregate stability. Soil aggregate stability is influenced by soil organic carbon (SOC). However, the influence of SOC from different fall/winter cover crop roots (annual and perennial crops) on aggregate stability through soil internal forces (SIFs) (electrostatic repulsive force (P erf), van der Waals attractive force (P vdw), and surface hydration repulsive force (P h)) remains unclear. The objectives of this study were compare three fall/winter cover crops (lucerne, rapeseed, six-year-vetiver (Vet_6Y)) and two control (fallow and fallow with SOC removal (fallow-SOC-R)) to determine SOC effects red soil aggregation through SIFs. Plant root morphological and chemical traits, SOC properties, soil surface charge properties, soil internal forces and aggregate breakdown were all determined. The perennial crop (Vet_6Y) showed the highest root number density (0.21 counts cm−2), second highest root mass density (1.80 mg cm−3), and the lowest root lignin/cellulose ratio (0.69), and thus contributed to higher SOC content and SOC functional groups (mainly polysaccharide-C) than annual crops (rapeseed and lucerne). Such SOC traits in perennial vetiver resulted in a higher specific surface area (SSA), lower surface charge density and surface charge number (Q s) compared to annual crops (rapeseed and lucerne) and controls, and the relationship between the root, SOC and soil surface properties (i.e., SSA) was further confirmed by significant correlation (r ranging from 0.76 to 0.97). Ultimately, these soil surface charge properties after cover crops increased P vdw , decreased P erf , and thus decreased repulsive net force (P net) (the sum of P vdw , P erf , and P h) and the average repulsive net force displayed in order of fallow-SOC-R (2.77 MPa) > fallow (2.11 MPa) > lucerne (2.02 MPa) > rapeseed (1.78 MPa) > Vet_6Y (1.45 MPa) at a distance of 1 nm. This resulted in the mass percentage of released small particles (<20, <10, and <2 µm) w (< d) % from aggregate being reduced after cover crops compared to controls. Generally, clayey red soil aggregate stability can be improved by decreasing the repulsive soil P net through cover crop root contribution to SOC and SOC-functional groups. [ABSTRACT FROM AUTHOR]

• Soil erosion modulus of the large-scale gullies increased from north to south. • Hydraulic erosion dominated gully development during one-year monitoring period. • Contribution of gravity erosion to the gully was ascribed to hypsometric integral. • Clay in colluvial deposits contributed to regional difference of gully erosion. Gully erosion is the most serious threat to sustainable development of global ecosystem and economy, with declining soil productivity and fertility threatening agricultural production. However, due to limitations in quantifying gully erosion rate, origin of erosion could be hardly distinguished. This study aimed to figure out this problem by developing a soil erosion estimation method based on unmanned aerial vehicles (UAV) monitoring techniques. Specifically, 18 gullies with different terrain characteristics were selected across typical erosion regions in southeast China, and UAV low-altitude photography, weather station monitoring, and field sampling investigation were conducted from 2020 to 2021to monitor their total erosion volume (VE), collapse volume (VC), proportion of collapse volume to total erosion volume (VC%), morphological parameters (e.g., total length of scour channels, L; erosion area, A; residual volume, V; and hypsometric integral) and soil-environmental factors (rainfall, temperature, and soil properties). It showed that 92.65 % of VE was resulted from colluvial deposits, attributing to the variation of L. Additionally, VC quantifying the amount of gravity erosion was determined by soil clay content in the upper catchment (Clay1). And percentage of VC to VE, characterized by VC%, possessed a significant linear correlation with HI (R2 = 0.571, p < 0.001). Moreover, regional differences of VE and VC was mainly attributed to soil clay content in colluvial deposits (Clay3) and HI. Collectively, clay content in the gully system inhibited gully erosion, while all the morphologic factors facilitated the development of gully erosion. Meanwhile, rainfall and temperature had significant impacts on VE and the regional difference of VC, probably due to the limited monitoring period. [ABSTRACT FROM AUTHOR]

Service life of wooden foundation piles could be at risk during modern urban construction work, as local groundwater conditions might change and cause increased degradation of nearby buried wood material. Maintaining a high groundwater level has been linked to good preservation conditions, but detailed studies on the effect of lowering the water level have not yet been performed. In this unique designed laboratory study, we explore how reduced water levels affect degradation rates of wood rods embedded in clay soil. In clay columns, effects of reduced water levels (30 cm, 60 cm) and fluctuating water levels (0–60 cm) were investigated at three levels (−5 cm, −30 cm, −55 cm). Two controls were included, one with no water reduction and one with sand soil. Redox potential was measured regularly at the three levels, and soil moisture was measured at start and end of experiment (12 months). Results showed that lowering water levels generally increased wood degradation. Decay took place almost exclusively by soft rot fungi and was highest at −5 cm below soil surface. At −55 cm depth and −400 mV redox potential, scarcely any decay was observed. Desiccation was highest in sand and in clay with −60 cm water reduction, and any decay process here had stopped. Surprisingly, fluctuating water level generated equally low decay rates as a high stable water level. Covered soil surfaces yielded less degradation and the effect was even comparable to that of a maintained high groundwater level. Protecting soils against desiccation could thus keep wood degradation at a minimum at open-air excavations. More experiments are needed to determine long-term effects and threshold values for decay in relation to redox potential. • Degree of degradation decreases with depth of burial and higher water level. • Fluctuating water levels (high – low) is just as protective as fully saturated soil. • A relative correlation between redox potential and decay rates by soft rot is observed. • No redox potential threshold values for onset of fungal decay could be concluded. • Soft rot decay at +80 mV was just as intense as at higher redox potential, suggesting that a threshold was reached. [ABSTRACT FROM AUTHOR]

• Mechanical and microstructural behavior of a clayey soil stabilized by an alkali-activated binder composed of two residues. • Experimental design to analyze the mechanical behavior of soil-alkali activated binder, and soil-Portland cement mixtures. • Porosity/binder content index as a reliable parameter when evaluating soil stabilization. This paper evaluated the mechanical and microstructural behavior of a clayey soil stabilized by an alkali-activated binder composed of two residues (sugarcane bagasse ash and hydrated eggshell lime) and sodium hydroxide. The sugarcane bagasse ash, an agro-industrial waste, contains high aluminosilicates content (64.74 % silica and 13.25 % alumina), needed for alkali-activation processes; calcium additions from the lime (72.90 % calcium oxide) allow curing at room temperatures. An experimental design analyzed the mechanical behavior of soil-alkali activated binder, and soil-Portland cement mixtures. Unconfined compressive strength (UCS), tensile strength (STS), stiffness (G 0), durability (accumulated loss of mass, ALM), and matric suction tests, and XRD and SEM-EDS investigations were performed. Statistical analysis showed a higher influence of the dry unit weight over the binders' mechanical results. In addition, binders presented similar mechanical results for mixtures cured in room temperature (23 °C) (e.g., UCS around 5 MPa for high density-high binder content samples with 30 % moisture content, and STS around 0.6 MPa for high density-high binder content samples with 28 % moisture content). For both binders, the lowest ALM was 1.63 % for high density-high binder content samples. The porosity/binder content index was a reliable parameter when evaluating soil stabilization. XRD and SEM analysis of alkali-activated samples showed, respectively, an amorphous hump attributed to disordered structures (C S H and (C,N)-A S H) and soil particles embedded in a cementitious matrix. Higher temperature (40 °C) and curing period (28 days) resulted in a denser structure. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) decomposition and stabilisation are largely affected by microbial carbon use efficiency (CUE), which is defined as the proportion of substrate carbon (C) uptake that microbes use for growth. Microbial CUE varies due to substrate quality and availability differences, but this may also depend on soil properties, such as pH, soil organic C (SOC) and clay content. We conducted a meta-analysis using data from 26 publications and analysed 272 CUE observations to investigate whether the substrate type has a distinct effect on microbial CUE and how CUE varies with the amount of substrate application and soil factors (pH, SOC, and clay content). We observed large variations in the CUE among different substrates, but we could not discern clear associations with substrate complexity, nitrogen, and energy content. Most of the studies used glucose as the substrate. The CUE of glucose significantly increased with decreasing amount of substrate applied and increasing clay content. We further observed a significant increase in glucose CUE with increased soil pH and decreased SOC content, although these relationships were relatively weak. Overall, our findings suggest the possibility of rapid adsorption of glucose or microbial products derived from glucose, which would then reduce substrate availability to microbes and increase CUE. The combined effects of greater adsorption and higher CUE with increased clay content would therefore result in more C stabilisation. We emphasise the need for including rapid adsorption of substrates and their microbial products when investigating substrate-specific microbial CUE. [Display omitted] • Microbial carbon use efficiency (CUE) varied among different substrates. • Rapid substrate adsorption may limit substrate availability to microorganisms. • CUE varies with substrate-specific adsorption of microbial products. • Increasing clay content increased CUE of glucose. [ABSTRACT FROM AUTHOR]

Adhesion between metal surfaces and soil can have significant effects on soil-tool interaction. The cone pull-out test (CPT) and piston pull-out test (PPT) for adhesion assessment were used in this study on smectite, illite and kaolinite clays at different water contents. In the CPT, the tangential adhesion stress (TAS) and cone adhesion (CA) were measured. In the PPT, the normal adhesion stress (NAS) and piston adhesion (PA) were measured. The results showed that the NAS and TAS depended on the type of clay. The ratios of NAS to TAS for smectite and kaolinite had the largest and smallest values, respectively. For all three types, NAS and TAS decreased as the water content (W) decreased. An increase in the thickness of the water film at the soil-metal contact surface reduced the stress required to separate the metal from the soil. The relationship between CA-W and PA-W for the three clay types differed. For smectite, a change in water content had no effect on CA or PA. For illite, an increase in water content decreased the CA and PA. For kaolinite, a bell-shaped curve formed such that, as water content increased, where WLL, CA and PA decreased. For all three clay soil types, NAS and PA were higher than TAS and CA at a specific water content. This demonstrated the effect of the metal-to-soil contact geometry on the adhesion parameters. The NAS and TAS values were classified in terms of clogging potential. Clogging potential is the adhesion of soil to the cutting tools or conveying system. The selection of the use of the CPT or PPT for adhesion assessment depended on the phenomenon being studied. • The metal-to-soil contact geometry does affect on adhesion parameters. • The normal adhesion stress (NAS) was higher than the tangent adhesion stress (NAS). • The piston adhesion (PA) was higher than the cone adhesion (CA). • The NAS and TAS decreased as the water content decreased. • There is linear relationship between NAS and TAS. [ABSTRACT FROM AUTHOR]

Cement and other traditional materials are frequently used to improve the properties of soil in the Yellow River Basin, the ecological environment has become severely polluted. To promote the environmental protection strategy of sustainable development, environmentally friendly biopolymers were used to treat typical silt samples collected from the Yellow River Basin. The water retention characteristics and vegetation growth of the treated silt were evaluated, and the microscopic mechanism of the water retention characteristics was investigated. The results show that the water retention capacity of the treated silt increased upon increasing the ratio of xanthan gum, gellan gum, and guar gum, with gellan gum performing better than the other two gums. The biopolymers had no discernible effect on the vegetation germination, but effectively promoted vegetation growth with a significantly lower wilting rate than that of the untreated soil. The soil treated with xanthan gum had the highest germination rate and vegetation growth height, while soil treated with gellan gum had the lowest wilting rate. The superior performance of gellan gum and xanthan gum can be attributed to their hydrophilicity and adhesion. These gums directly interact with the surface of charged clay particles in the soil pore space to closely connect the particles, reduce water loss, and increase the water retention capacity. The better soil water retention capacity is associated with improved germination and vegetation growth. • Water retention characteristics of biomolymer-treated soil in wide suction range. • Different biopolymers' effects on vegetation growth in treated soil. • The water retention capacity of treated silt increases as the ratio increases. • The water retention capacity of gellan gum was better than xanthan gum and guar gum. • The rate of wilting in treated soil was significantly lower than in untreated soil. [ABSTRACT FROM AUTHOR]

Organic wastes, fertilizers, organominerals, and minerals contain nutrients essential to crops and contribute to increase productivity. However their use can also lead to the accumulation of copper and zinc, which changes the distribution of their fractions and enhances the risk of toxicity to plants and the environment, thereby working against the sustainable development goals. However, the effect of manure applications on clayey soils and the effects of increasing Cu and Zn contents over the years on crop productivity remain unknown. This study aimed to evaluate the distribution and the potential for contamination of heavy metals in clayey soil with a history of the application of different types and amounts of fertilizers under Cynodon spp. grazing and no-tillage system for soybeans. In Experiment 1, Cynodon spp. were cultivated for hay production and submitted to applications of the following treatments: 0, 200, and 400 kg ha−1 of total-N in the form of pig slurry and urea. In experiment 2, the soybean was grown and subjected to the following treatments: control, pig slurry, commercial granulated solid organic fertilizer, organomineral fertilizer blended with granules, and mineral fertilizer blended with granules. The dose of each nutrient source was determined based on the soil analysis and the recommendations of the liming and fertilization manual. The experiments were conducted for four agricultural crops where soil samples were collected in the layer of 0.00–0.10 m layer and submitted to chemical fractionation of Cu and Zn. The use of pig manure increased the availability of Cu and Zn in the soil, causing an increase in the distribution of copper organic (40.73% and 57.64% for PS200 and PS400 treatments, respectively, in Experiment 1; 67.33% for PS treatment, in Experiment 2) and residual fractions (10.01% and 7.60% for PS200 and PS400 treatments, respectively, in Experiment 1; 9.80% for PS treatment, in Experiment 2), while zinc was predominant in clay-mineral (61.04% and 92.01% for PS200 and PS400 treatments, respectively, in experiment 1; 278.90% for PS treatment, in Experiment 2) and residual fractions (2.36% for PS200 treatment in experiment 1; 9.90% for PS treatment, in Experiment 2). Additionally, the use of swine manure increased the Cu and Zn contents in the exchangeable fraction, which may potentiate the toxicity to plants and increase the potential for contamination of subsoil water. However, the increased bioavailability of Cu and Zn did not caused a loss of crop productivity but instead increased dry mass production and crop yield. • Use of PS in the highest dose increases Cu and Zn available contents in the soil. • Use of PS accumulates Cu in the organic and residual fractions. • Use of PS accumulates Zn in the mineral and residual fractions. • There was no harm to Tifton 85 DM the accumulative production over the years. • There was no harm to soybean DM accumulative production and productivity over the years. [ABSTRACT FROM AUTHOR]

The performance of pile foundations subjected to cyclic lateral loading is central to offshore geotechnical engineering. Although non-linearity and path-dependence of soil mechanical behavior at small strains are widely recognized, the influences of these local behavior on global response of pile foundations are less explored. This work presents numerical analyses of cyclically-loaded piles in undrained clays that explicitly account for soil small-strain characteristics. By using intergranular strain (IGS) elasticity method, a soil model proposed by the authors for undrained clays during cyclic loading is extended to include non-linear small-strain behavior. Via comparing against element tests, the constitutive relation is shown capable of representing the observed variation of soil stiffness and damping with strain magnitudes, as well as the dependence of such non-linearity on stress paths. Based on the above soil model, finite element simulations are performed to interpret the response of laterally loaded piles from geotechnical centrifuge tests. The impacts of soil small-strain behavior on pile force–displacement relations, hysteric loops, and the ability of a pile–soil system to dissipate energy are investigated. This work highlights that the sensitivity of these foundation responses to small-strain non-linearity of soils can vary considerably, depending on pile geometry features and head constraint conditions. • Influence of soil small-strain behavior on cyclically-loaded piles is investigated. • Soil model considers path-dependent stiffness variation at small strains. • Small-strain behavior impacts foundation hysteric loop and energy dissipation. • Effects of soil small-strain behavior depend on pile geometry and head condition. [ABSTRACT FROM AUTHOR]

In Niigata, Japan, many landslides have occurred in Tertiary rocks. Although most of these landslides were slow-moving, some underwent catastrophic failure, and different types of landslides sometimes occurred nearby under almost identical geological and hydrological conditions, but their mechanisms remain unclear. This study introduces a landslide triggered by Typhoon Hagibis in 2019 in an area in Niigata prone to landslide disasters. The landslide was small in scale, but the displaced materials were fluidized and deposited on a flat field at the toe of the slope after a long runout. To unravel this landslide's initiation and movement mechanisms, we conducted ring shear tests on the samples (clayey soils) taken from the landslide source area to examine their shear behaviors under both undrained and naturally drained conditions. Our results of undrained shear tests showed that shearing of the saturated landslide material can develop high pore-water pressure, lowering the shear resistance and elevating the mobility of the landslide. The results of shear tests under naturally drained conditions at different shear displacement rates (V) revealed that landslide materials behave rate-weakening at low and rate-strengthening at high rates, respectively. Further, it was found that during continuous shearing, a sudden change in V results in a sharp but temporal change in the mobilized shear strength. Different accelerations through which the shear rate was increased to a given V also result in different mobilized peak shear strengths. Our results indicate that the different landsliding phenomena occurring in the same area might be regulated by the diverse shear behaviors of the landslide materials involved in the sliding: contractive behavior may result in catastrophic failure, while the shear rate- and state-dependent shear behavior of the landslide material regulates the slow landsliding phenomena. Our results provide new insights for better understanding and predicting different landsliding phenomena within the same geological settings. • Kamoda landslide is a small fluidized one that occurred on clayey materials. • The landslide materials showed great reduction in shear resistance under undrained condition. • The residual shear strength of the landslide material exhibits diverse tendencies with shear rate. • These diverse shear behaviors provide insights toward understanding different landsliding phenomena in the same area. [ABSTRACT FROM AUTHOR]

This paper presents the results of a centrifuge study in which swell of an expansive clay profile was induced in the centrifuge. A factor which has previously hindered such research is the time required to induce significant swell in-flight, within a reasonable time frame. In this study the use of an artificially fissured fabric together with geotextile layers allowed for a significant magnitude of swell to be achieved within a matter of hours. Measurements of matric suction and water content throughout testing highlight the potential difficulties associated with such measurements in a fissured profile. The suction in clay along the interfaces of fissures can be significantly reduced almost instantaneously with the ingress of water. In contrast, elements closer to the centre of intact masses may take significantly longer to respond, illustrating the role of the dual processes (and hence dual scaling laws) of moisture ingress along fissures, followed by diffusion associated with swelling of the clay. A comparison of the magnitude of swell induced in this centrifuge model with that of conventional oedometer swell tests indicated gross overpredictions from the oedometer testing. In this comparison, the severe limitation of oedometer tests reducing a sample to a point of zero suction is emphasised. Finally, it is illustrated how an understanding of the rate of swell throughout an expansive profile can provide insights into the validity of the predictions from oedometer swell tests. • A centrifuge study of an artificially fissured expansive clay profile is presented. • A significant magnitude of swell was achieved in-flight in a short timeframe. • Suction, water content and penetration resistance were measured in-flight. • Swell in the model was compared with results of conventional oedometer tests. • Limitations of conventional oedometer testing are presented. [ABSTRACT FROM AUTHOR]

The role of clay minerals on the strength development of cement stabilized clays at different cement contents, water contents and curing times was studied in this research. Kaolin and sodium bentonite were used to represent non-swelling and high swelling soils respectively. The soils studied were mixtures of kaolin and bentonite at replacement ratios of 0, 25, 50, 75, and 100% of the dry weight of bentonite to have various swelling potentials. The water content of the soil samples was adjusted to the optimum water content (OWC) and to the liquidity index (LI) of 0.25–1.50, so as to simulate different initial soil phases. The macro- and micro-observation indicated that the clay mineral, water content and cement content were the predominant influence factors controlling the strength development of cement stabilized clays, at a particular curing time. For a particular clay mineral, the total soil water to cement content, s-w/c was found to be the prime parameter reflecting the effect from both water content and cement content on the strength development in cement stabilized clay. The generalized strength model can be represented in the form: q u = A/B(s-w/c) where q u is unconfined compression strength, and A and B are constant. The values of parameters A and B were found to be primarily controlled by the clay mineral, which was found to be described by plasticity index. The generalized strength model was validated using separated test data. This model will facilitate the engineering decision of selecting the water content and cement content to attain the target strengths of clayey soils at required curing time with minimum number of trials. • Study microstructure of unstabilized and cement stabilized clayey soils via SEM. • Study roles of clay mineral, cement content, and water content on strength development. • Develop the generalized strength model of cement stabilized clays with 25% < PI <257%. • Verify the generalized strength model with test data at very high R2 > 0.97. [ABSTRACT FROM AUTHOR]

Heavy metal contaminated soils pose a serious threat to the environment, and preparing ceramsite using contaminated soils was proposed as an effective method to address this threat in this study. Specifically, two typical soils (i.e., contaminated clay and sandy soil) were mixed with different ratios and calcined at temperature 1000–1200 °C to prepare ceramsite. Special attentions were paid to evaluating the immobilization of heavy metals in ceramsite and identifying the corresponding immobilization mechanisms. Using the leachability of heavy metals from ceramsite as evaluation criteria, the optimum mixing ratio of clay/sandy soil and sintering temperature were determined as 0.6:0.4 and 1200 °C. Moreover, based on the spectroscopic characterizations and thermodynamic calculation, high sintering temperature well facilitated the liquid phases formation, promoting the reactions between heavy metals and aluminosilicates and the valence state conversion of heavy metals. Accordingly, heavy metals were well immobilized in ceramsite by forming thermodynamically stable minerals, being encapsulated in solid matrix, and transforming to valence states with low mobility. The leaching conditions including pH and temperature had minimal effect on the immobilization of heavy metals in ceramsite. In summary, ceramsite prepared by contaminated soils was environmentally friendly and had good potential in engineering application as building materials. [Display omitted] • Co-utilization of polluted clay and sandy soil for ceramsite production is presented. • The optimum ratio of clay/sandy soil and sintering temperature are 0.6:0.4 and 1200 °C. • The immobilization effectiveness of heavy metals in ceramsite is evaluated. • The immobilization mechanism of heavy metals in ceramsite is determined. [ABSTRACT FROM AUTHOR]

Soil conservation ecosystem services (SCESs) are related to food production, safety of residents, water quality, and public health. However, the traditional assessment framework only focuses on a single dimension of SCESs, and the efficiency and development trends are often overlooked. A multidimensional assessment framework was established to assess SCESs in terms of the total output, efficiency, development trend temporally and spatially. Additionally, the traditional perspective of influencing mechanism analysis was expanded to include spatial heterogeneity. The influencing strength and distance were quantitatively revealed at pixel resolution. The results indicate that (1) the SCESs in Minnesota were generally improved from 1998 to 2018. (2) 70% and 78% of the counties experienced low-output and low-efficiency problems, respectively. (3) The Twin Cities constituted the degradation cores of SCESs in Minnesota. (4) The cropland and forestland proportions and rainfall were the top three influencing factors, causing SCES changes of 0.9959%, 0.4937%, and 0.1536%, respectively, for every 1% change in these factors. (5) According to the influence scopes, the soil organic carbon (SOC) content, normalized difference vegetation index (NDVI), and soil silt content were classified as long-distance factors, the soil sand content, slope and soil clay content were categorized as moderate-distance factors, and the remaining variables were identified as short-distance factors. (6) The influencing factors imposed both positive and negative influences on the SCESs, and attenuation or alteration of the adverse influences on SCESs through specific human interventions is a very promising approach. • A multidimensional assessment framework was proposed. • The SCESs in Minnesota has been severe with an upward development. • Degradations were classified into five types at county level and concentrated at "Twin Cities". • The proportions of cropland, forestland, and rainfall were the strongest influencing strength factors. • The influencing factors are classified as long-distance, moderate-distance, and short-distance factors. [ABSTRACT FROM AUTHOR]

Overcoming the consequences of future scarcity of P is crucial to ensure agriculture sustainability. This requires decision-making processes depending on data on the P status of agricultural fields, commonly conducted with soil P tests (SPTs), and efficient use of the resource on a societal scale following a circular economy approach. All this will decrease the P losses and the subsequent environmental impact. However, SPTs are not universal and, even for a given SPT, the definition of threshold values for fertilizer response is not accurate. This work aimed to define models to predict Olsen P threshold values, allowing the identification of P-responsive sites at the European scale as a basis for more accurate and sustainable P fertilization schemes based on a circular economy approach. To this end, a data set was compiled based on a literature review that describes the Olsen P threshold values for different crops under field conditions. Subsequently, an analysis of potential P fertilizer requirements was performed on agricultural soils of the European Union (EU) using the data set of the LUCAS project and how this need can be covered with a circular economy approach. Environmental factors were more relevant than crops to explain the variation in threshold values. A regression model involving soil pH and clay content and annual average rainfall as independent variables explained 61% of the variance in Olsen P threshold values. When soil pH and clay content were the only explanatory variables, the explained variance was 49%. This reveals the need to take into account factors related to P buffer and sorption capacity to estimate accurate threshold values. We detected that only 27.8% of EU cropland soils and 42.7% of grassland soils were P-responsive. We can conclude that a more precise allocation of the resource is possible in P-responsive sites and also that most of the European demand for P could be covered by recycling P from manure, wastewater, and municipal solid waste. • Identification of P-responsive sites is possible using a simple model for the estimation of Olsen P threshold values. • This will allow for a better allocation of P resources and more accurate estimates of P fertilizer rates. • Only 27.8% of croplands EU soils were P-responsive. • Most of the European P demand could be covered with a circular economy approach. • Results will contribute to agricultural sustainability and environmental performance in the use of P resource. [ABSTRACT FROM AUTHOR]

Understanding the heterogeneous distribution of soil organic matter (SOM) on soil particles is essential for predicting the stability of organic carbon (C) in soil, but direct visualization of the microscopic distribution of organic C in soil is still challenging due to the complexity of soil particles. In this study, a paddy soil was fractionated and spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) coupled with electron energy loss spectroscopy (EELS) was employed to analyze the microscopic distribution of organic C species on clay-sized soil particles (<2000 nm) from the different size fractions (800–2000 nm, 100–800 nm and 0–100 nm) at the nano and sub-nano scale. The EELS results demonstrated that the relative abundance of both phenolic and aliphatic C was quite independent of the particle size fractions, while aromatic and carboxyl carbon demonstrated the largest variations between fractions. With the decrease in soil particle size from 800 to 2000 nm to 0–100 nm, the median abundance of carboxyl (oxidized) C increased from 23% to 35%, and aromatic (reduced) C decreased accordingly from 40% to 16%. The statistical analysis demonstrated that the local organic C concentration was the major factor accounting for the variations in oxidized and reduced C species in soil particles, in which selective sorption of the organic C abundant of acidic functional groups by reactive minerals was responsible for the enrichment of oxidized C in small clay size soil particles. Overall, the results of this study contribute to an improved understanding of the chemical diversity of SOM in organo-mineral interfaces and provide insights in the microscopic C stabilization mechanisms in natural soils. [Display omitted] • Distribution of SOM at different sized soil clay particles was unveiled by Cs-STEM. • Heterogeneity of organic C species was visualized at the nano and sub-nano scales. • Aromatic and carboxyl C showed significant variations among soil clay fractions. • Local organic C concentration determined chemical heterogeneity of organic C species. [ABSTRACT FROM AUTHOR]

Phosphorus (P) availability in highly weathered soils is significantly influenced by the contents of iron (Fe)/aluminum (Al) oxides, clay minerals, and organic matter. With the increasing interest in biofertilizers (e.g. chitosan), it is important to understand how they affect P adsorption profiles on colloids of weathered soils rich in Fe/Al oxides. Thus, the effect of chitosan on the adsorption of P to colloids of hematite, gibbsite, Oxisol, and Ultisol was studied through electrokinetic measurements, spectroscopic analysis, and adsorption edge/isotherm profiles. The presence of chitosan significantly improved the surface positive charge and the decreasing trend of surface positive charge was slower for chitosan-treated colloids compared to the control with increasing pH. At pH 5.0, all the colloids were positively charged, with the oxides containing more positve charges than the soil colloids. At this pH value, the surface coverage capacity of P was 99.1, 61.6, 50.5, and 37.5 mmol kg⁻1 for Oxisol, Ultisol, hematite, and gibbsite, respectively. This suggests that clay minerals in soil colloids were vital in enhancing P adsorption. In the presence of chitosan, the surface coverage capacity of P was increased by 111%, 173%, 647%, and 488% for Oxisol, Ultisol, gibbsite, and hematite, respectively. Drawing inferences from spectroscopic analysis, citric acid desorption profile, and zeta potential analysis, we suggest that chitosan (CH) enhanced P adsorption by promoting the formation of (i) citric acid "undisplaceable" inner-sphere P complexes such as [Colloid-OP- O -CH] and [Colloid-OP- N -CH] , (ii) citric acid "displaceable" outer-sphere P complexes such as {[Colloid- O -CH]-OP} and {[Colloid- N -CH]-OP} , and (iii) water "leachable or soluble" P complexes such as {[Colloid-CH] + PO 4 ³⁻} and {[Colloid-OP]⁻CH + }. Thus, applying chitosan as a biofertilizer (source of N) along with P in highly weathered soils could improve P availability while reducing P leaching. [Display omitted] • Soil colloids adsorbed more phosphate than gibbsite/hematite due to clay minerals. • Chitosan enhanced positive charge of soil colloids more than for gibbsite/hematite. • Chitosan enhanced P adsorption through electrostatic and chemical complexation. • Effect of chitosan on P adsorption was largely dependent on chemical complexation. [ABSTRACT FROM AUTHOR]

Overcoming the consequences of future scarcity of P is crucial to ensure agriculture sustainability. This requires decision-making processes depending on data on the P status of agricultural fields, commonly conducted with soil P tests (SPTs), and efficient use of the resource on a societal scale following a circular economy approach. All this will decrease the P losses and the subsequent environmental impact. However, SPTs are not universal and, even for a given SPT, the definition of threshold values for fertilizer response is not accurate. This work aimed to define models to predict Olsen P threshold values, allowing the identification of P-responsive sites at the European scale as a basis for more accurate and sustainable P fertilization schemes based on a circular economy approach. To this end, a data set was compiled based on a literature review that describes the Olsen P threshold values for different crops under field conditions. Subsequently, an analysis of potential P fertilizer requirements was performed on agricultural soils of the European Union (EU) using the data set of the LUCAS project and how this need can be covered with a circular economy approach. Environmental factors were more relevant than crops to explain the variation in threshold values. A regression model involving soil pH and clay content and annual average rainfall as independent variables explained 61% of the variance in Olsen P threshold values. When soil pH and clay content were the only explanatory variables, the explained variance was 49%. This reveals the need to take into account factors related to P buffer and sorption capacity to estimate accurate threshold values. We detected that only 27.8% of EU cropland soils and 42.7% of grassland soils were P-responsive. We can conclude that a more precise allocation of the resource is possible in P-responsive sites and also that most of the European demand for P could be covered by recycling P from manure, wastewater, and municipal solid waste. • Identification of P-responsive sites is possible using a simple model for the estimation of Olsen P threshold values. • This will allow for a better allocation of P resources and more accurate estimates of P fertilizer rates. • Only 27.8% of croplands EU soils were P-responsive. • Most of the European P demand could be covered with a circular economy approach. • Results will contribute to agricultural sustainability and environmental performance in the use of P resource. [ABSTRACT FROM AUTHOR]

The interaction of similar soil forming factors with different parent materials determines soil chemical weathering, influencing soil processes and properties. In the coastal temperate rainforests of southeast Alaska, Spodosols is the dominant soil order in well-drained parent materials regardless of the lithology. Yet, the role of lithology on chemical weathering, base cation depletion, and mineral transformation during pedogenesis remains elusive. Here, we established a lithosequence comprised of soils derived from tonalite, phyllite, slate, and metavolcanic rocks to test the hypothesis that despite the soils in southeast Alaska presenting similar taxonomy and morphology, the influence of lithology in chemical weathering intensity and mineralogy can be detected. We evaluated physicochemical properties, clay mineralogy, Fe-Al oxides, chemical weathering, and elemental mass balance on eleven Spodosols sampled along the lithosequence. We also propose a new weathering index, the Weathering Index for Spodosols (WISP), suitable to evaluate the weathering degree of soils with Al mobility and base-rich parent materials. This index fills a gap in traditional weathering indices that uses Al as an immobile element and/or does not evaluate the leaching of main base cations. We found the pedons across the lithosequence expressed similar physicochemical properties, with predominantly thick profiles, presenting andic properties, relatively thick spodic horizons, and thin E horizons. Podzolization imposed similar mineral transformation trends, mainly dissolution of chlorite, mica alteration to interstratified mica-vermiculite, and formation of smectite in E horizons. Kaolinite was detected in the soils from all lithologies, but only in trace amounts in phyllite soils. Fe oxides depth distribution was similar but with a higher concentration in the slate (44.5 ± 4.2 g/kg), followed by metavolcanic (31.6 ± 4.0 g/kg), phyllite (27.9 ± 3.8 g/kg), and tonalite soils (19.9 ± 5.7 g/kg) and predominantly as organometallic complexes (extracted by Na-pyrophosphate). The stronger weathering of chlorite and mica in the E horizons was reflected in larger losses of Mg and K, while Ca and Na were more depleted in the spodic horizons, suggesting plagioclase weathering. Slate soils were the most depleted in base cations, followed by phyllite, tonalite, and metavolcanic soils. The more depleted status of slate soils was supported by the higher WISP values (WISP = 62), followed by phyllite (WISP = 55), tonalite (WISP = 53), and metavolcanic soils (WISP = 45). Our results demonstrated that lithology controlled elemental depletion intensities, Fe oxide concentrations, and partially the clay fraction mineralogy in addition to podzolization acting as a dominant pedogenic process across all sites. These findings advance our understanding of the role of lithology on soil mineralogy/geochemistry that impacts critical soil functions, such as the soil carbon cycle, elemental fluxes, organo-mineral interactions, and solid-solution reactions. [ABSTRACT FROM AUTHOR]

Accurately describing rill development is important for building physical process models of soil erosion. The objectives of this study were to investigate the evolution processes of rill erosion morphology, their impacts on runoff and sediment yield, and the relationship between flow hydraulic characteristics and rill erosion dynamic mechanisms on slopes of two soil types, namely, clay loam soil (CLS) and loess soil (LS), under two successive rainfall events at a rainfall intensity of 120 mm h−1. We used digital close range photogrammetry technology to obtain overhead images of two experimental soil bins (5 m long, 1 m wide and 0.5 m deep with a slope gradient of 20°) at 5-minute time intervals to monitor the dynamic processes of rill erosion. The results showed that rill erosion processes exhibited important impacts on sediment and runoff and its hydrodynamic characteristics. Compared with LS, runoff formed and rills developed earlier in the CLS slope. Soil with high clay content was more prone to form rills, but less susceptible to severe soil erosion than LS. Once rills began to develop in LS, soil loss increased and the morphology of rills changed rapidly, as did runoff rate. The flow velocity for the two soils decreased gradually with time and increased along the flow direction. The trend of Froude number (Fr) decreased with time, whereas the Darcy-Weisbach resistance coefficient (f) exhibited an opposite trend. The Reynolds number (Re) of LS increased first and then decreased, while Re of CLS decreased gradually with time. Sediment yield and runoff were positively correlated with f , but significantly negatively correlated with Fr. Moreover, Re was significantly negatively correlated with sediment yield, but not with runoff. These results are of great importance for soil loss prediction. [ABSTRACT FROM AUTHOR]

Phosphorus (P) retention capacity of soils directly affects the management of phosphate fertilization, and has economic and environmental importance. Brazil has expressive agricultural production and high edaphoclimatic variability; still, the detailed spatial distribution of P retention capacity is not known. Thus, machine learning models were created to estimate the P retention capacity of soils at superficial horizons using the variables: clay content, sand content, soil organic matter, pH, base saturation. The four best models were combined to create an ensemble (a combination of models), which was applied in a dataset (5524 samples) that comprises a sample data from the entire Brazilian territory. The ensemble was used to build a map of P retention capacity. Most of the country presented soils with medium P retention (40–60%), and large areas with very high retention capacity were found in the south of Brazil, a subtropical region mostly associated with clayey soils. High P retention was observed for Histosols, probably related to humic-Al(Fe) complexes. Nitisol, Ferralsol, Gleysol and Cambisol classes presented high P retention, especially for clayey soils with qualifiers related to bases/weathering (Dystric) and organic matter (Umbric and Humic). The correlation between Fe oxide minerals and P retention varied with soil color and drainage conditions mainly associated to redoximorphic reactions; the same was not observed for Al oxide minerals. This pioneer study revealed the distribution of P retention capacity across different soil classes in Brazil, which can help to define land use suitability and soil P management strategies that ensure profitable agricultural exploration. [Display omitted] • In 34% of the country, soils had P retention capacity framed as Low and 22% as High. • The Histosol class presenting soils with elevated P retention capacity (>60%). • For mineral soils, the highlighted classes were Nitisol, Ferralsol, Gleysol and Cambisol. • Soil color and drainage conditions had little effect on soil P retention capacity. [ABSTRACT FROM AUTHOR]

Natural and man-made slope failure has been a phenomenon that has caused many deaths, destruction, and environmental damage. The use of bioengineering technique (grasses) has been widely approached for slope remediation work. However, slope failure still occurs even though it has been protected by a few grasses. Many previous findings have reported on root pull out and root tensile strength for different plant species. However, the type of soil was not taken into account. Therefore, this research was carried out to investigate the function of root mechanical properties in different types of soil. The dry and wet sieve analysis tests were performed to know the classification of the soil. In addition to that, the soil mineralogy test was also conducted to support the soil classification. Root tensile strength tests were carried out on well-grown and poorly-grown Bermuda grass toward sandy and clay soil in dry and wet conditions. The dry condition is considered the condition of Bermuda grass in hot weather, while the wet condition is the condition after the raining season. Bermuda grass was chosen since this type of grass is widely applied for slope stabilization. The site locations were chosen in Temerloh, Maran which consist of clay soil. The other locations chosen were Karak, Gambang, Kuantan, Dengkil, Batang Kali, Ulu Yam, Kuala Pilah, Gombak and Sabak Bernam consist of sandy soil. The results show that the single root of Bermuda grass has higher tensile strength in sandy soil with range values from 0.47 to 185 Mpa compared to clay soil with range values from 0.12 to 159.10 Mpa. In conclusion, the results indicate that soil is one of the factors that influence the growth of bioengineering techniques for slope reinforcement. • A bioengineering method is being used as an alternative for slope stabilization. • The soil stability will increase with time as the root grows. • The pull out force was much affected by tensile strength. • In term of tensile strength, the value decreases with increasing root diameter. • Roots have a great impact on tensile and pull out strength. [ABSTRACT FROM AUTHOR]

• The effect of different polystyrene (PS) fractions added to laboratory standard soil particle sizes was evaluated using MIR spectra. • MIR absorbances from binary soil-PS mixtures were different. • MIR absorbances depend on the combination of the soil physical fraction and PS particle size. • No linearities were observed depending on the fraction analysed. As the volume of plastics produced, used, and discarded around the world continues to increase, the environmental pollution presented by these polymers and their by-products continues to be impacted. Different methods and techniques have been proposed to evaluate plastics in environmental samples, including soils. However, in most cases, the effect of variables such as plastic particle size, soil physical fractions, and interactions between them, was not evaluated or not well understood. The aim of this study was to evaluate the effect of different polystyrene (PS) fractions added to laboratory standard soil particle sizes (clay, sand, and silt) on the attenuated total reflectance (ATR) mid-infrared (MIR) spectra of the samples. Additive-free PS was sieved in four particle sizes, namely fraction 1 (∼500–251 µm), fraction 2 (∼250–181 µm), fraction 3 (∼180–107 µm) and fraction 4 (∼106–46 µm). The PS fractions were used to spike four physical soil fractions such as clay, loam, sand and sandy and analysed using ATR-MIR spectroscopy (4000–400 cm−1). The results of this study indicated that the MIR absorbances at specific frequencies of the binary soil-PS mixtures are different and depend on the combination of the soil physical fraction and PS particle size. Overall, no linearities were observed depending on the fraction analysed. This is of importance as the data indicates a different behaviour on the MIR spectral properties of the sample. Although further validation is needed, these results might have a direct effect on the development of robust protocols to monitor MPs in complex matrices such as soil using MIR spectroscopy. [ABSTRACT FROM AUTHOR]

• Thermal conductivity of lateritic clay increases with increasing soil temperature. • Water migration in lateritic clay increases with increasing heat source temperature. • Driving force of water migration is generated from both temperature and humidity gradient. • A three-dimensional heat and moisture transfer model is established and verified. The heat released by buried pipes of the soil thermal storage (STS) system will inevitably aggravate the coupling effect of heat and moisture migration in the surrounding soil, which may affect soil thermal properties and thermal storage characteristics. However, there is no conclusive evidence. A series of model tests were conducted to investigate the potential effect of the heat and moisture coupling migration on the heat transfer characteristics of buried pipes. A three-dimensional model considering the temperature dependence of soil thermal conductivity was established and verified. The effects of heat storage temperature and initial soil moisture on the heat transfer characteristics of buried pipes were further evaluated using the proposed model. Test results show that the thermal conductivity of lateritic clay increases with increasing soil temperature due to the latent heat transfer of vapor. For lateritic clay with an initial saturation of 13.42 %, the thermal conductivity increases to 7.3 times that of 5 °C at 90 °C. The driving force of moisture migration is generated from both temperature and humidity gradient. Soil moisture near to the buried pipe varies significantly during the first 3 ∼ 12 h due to the hysteresis of moisture migration caused by the temperature gradient driving. The soil moisture variations on the one-dimensional conditions are more significant than those under three-dimensional conditions due to the effects of gravity and paths on the moisture migration. Model validation results show that ignoring the moisture migration and temperature dependence of soil thermal conductivity will lead to the lower prediction value of the numerical model. Simulation results show that the influence of the initial soil moisture on the heat and moisture coupling migration should be taken into account when accurately evaluating the performance of STS system. [ABSTRACT FROM AUTHOR]

• Soil clay and moisture mediate the decoupling of C, N and P cycling along an elevational gradient. • Total organic C pools were highest where the clay content was highest. • Soil organic N pools were controlled by clay and soil moisture effects on microbial stabilisation. • Soil P pools were not related to clay and soil moisture. • Soil organic P was decoupled from soil organic C and N pools along the hillslope. Grasslands extend across a variety of topographies including non-flat hilly areas with varied soil texture and moisture that can mediate soil biogeochemical cycling of carbon (C), nitrogen (N) and phosphorus (P). In this study we examined soil organic C, total N and P pools (both inorganic and organic), as well as gross N mineralisation (GNM, as a measure of microbial activity and N dynamics) and microbial C, N and P in winter and spring along a grassland hillslope. Our results showed that variation in soil clay and associated soil moisture were the most important mediators affecting C and N dynamics along the grassland elevational gradient. Total organic C pools were highest where the clay content was highest, likely because of the sorption capacity of clay stabilising organic matter against microbial decomposition. Likewise, the variation in soil organic N pools along the hillslope was mostly controlled by clay and soil moisture effects on microbial stabilisation of organic N. Furthermore, microbial C, N and GNM increased with increased soil moisture, suggesting that microbial activity was limited by soil moisture. In contrast, soil P pools were not related to clay and soil moisture, while soil organic P was decoupled from soil organic C and N pools along the hillslope. Possibly, differences in microbial stabilisation and mineralisation pathways (oxidation for C and N, hydrolysis for P), microbial homeostatic regulation of C, N and P, and P fixation resulted in a decoupling of P from C and N cycling in this grassland. We conclude that variation in clay and associated soil moisture along grassland hillslopes can have important but non-unidirectional effects on soil C, N and P cycling. [ABSTRACT FROM AUTHOR]

[Display omitted] • FTIR spectroscopy of clay is sensitive to temperature during bushfires. • Boron leached from combusted bark decreases d11B of clays. • No direct influence of combustion temperature on d11B of clays. • Clays have higher d11B after experiencing a high severity fire. • Both FTIR spectroscopy and B isotope could be viable fire proxies. Bushfire occurrences will likely be exacerbated by climate change, thus requiring a model to forecast and manage their impacts. However, a robust bushfire model requires new proxies that can infer fire severity responses to past climate variability. A key test to the viability of new fire proxies is whether they record fire severity in the affected soil. We address this by testing Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy and boron (B) isotopes in soil clay fractions from Yengo National Park, southeastern Australia, as proxies for bushfire severity. The isotopic results were also compared to that of clays that reacted with experimentally combusted bark. ATR-FTIR spectroscopy constrains the soil temperature to between 225 and 500 °C during high severity fires, based on the lack of dehydroxylation peak characteristics and the increased aromatic to aliphatic organic peak ratios in clays, compared to that of low severity sites. The isotope composition of the non-exchangeable B fraction in clays is lighter after reacting with leaching solutions of bark combusted at higher temperatures. Combustion temperature does not affect the B isotope fractionation during B adsorption onto clays. Changes to the B isotope composition of clays could instead be justified by the varying B concentration and B isotope compositions of the leaching solutions. In Yengo soil clay fractions, sites that experienced a high severity fire show higher δ 11B values by about 1.5 ‰, compared to low severity sites- at odds with observations from our experiment using combusted bark. The combustion of leaves from tree crowns in high severity fires could account for the increase in δ 11B of clays post-fire. In summary, FTIR spectroscopy of clays could be useful for constraining soil temperature during bushfires, while the B isotope composition of clays appears as a promising proxy for fire severity. [ABSTRACT FROM AUTHOR]

• Biochar from sewage sludge, sugarcane, and green coconut increased the water retention in the sandy soil. • Sugarcane and green coconut biochars improved the water holding capacity of all tested soils. • Biochar reduced the bulk density of the sandy soil but not the clayey soil. • Biochar proved distinct benefits for the hydraulic properties of soils with different textures. Most of the Brazilian soils have severe water limitations to crop growth and, therefore, can benefit from organic amendments. For instance, biochar is known to improve soil water dynamics and use efficiency by increasing the water holding capacity and availability. This study assessed the effect of sewage sludge (SSB), green coconut residues (GCB), and sugarcane bagasse (SCB) biochars on the water retention capacity and availability of three tropical soils (Typic Quartzipsamment-TQ, Ultisol, and Luvisol). Control treatments (no biochar) were included as references. Soil bulk density, water holding capacity (WHC), water retention curves, and plant available water (AW) were determined. We also measured soil pH, organic matter content, and electrical conductivity (ECs). Biochar (SCB and GCB) increased the WHC by 62% in the Typic-Quartzipsamment, 38% in the Ultisol, and 18% in the Luvisol. The SCB increased the AW in the TQ and Ultisol by 40% and 10%, respectively. Conversely, SCB and GCB reduced the AW in the Luvisol by 22.5% and 17.5%, respectively. Biochar improved the WHC of the coarse-textured soils. In the clayey soil, biochar improved soil porosity and water transmission. We conclude that biochar can be an excellent amendment to soils across a range of textures. [ABSTRACT FROM AUTHOR]