Susceptibility Of Soils Research Articles

Modeling the response of a field probe for nondestructive measurements of the magnetic susceptibility of soils

AbstractNondestructive volume magnetic susceptibility measurements (MS) from the surface do not provide information about the depth distribution of a magnetic material or about the amount of magnetic material. We have developed a model that can be used to predict the volume magnetic susceptibility from the surface for a given (known or hypothesized) stratification of the magnetic layers in the soil profile. The measurements were performed with the MS2D Bartington sensor. The antenna signal from the MS2D probe decreases rapidly with depth. We show that the relative decrease in MS depends not only on the concentration of the magnetic tracer, but also on the distribution of the magnetic tracer in the soil profile. The decrease in sensitivity was fitted with a double exponential function. The function was implemented in a newly developed MagHut model. The MagHut model is a tool that can be used for forward modeling of the volume magnetic susceptibility when the tracer distribution in the soil profile is known. The model was successfully calibrated and validated with the measured data and with data from the literature. The Nash–Sutcliffe coefficients for goodness of fit were above 0.99 in all cases. MagHut can help interpret MS mapping results or it can be used to optimize amount and placement of the magnetic tracer for soil erosion experiments. However, the MagHut tool is only limited to the top 10 cm of the soil profile and cannot replace, but only complement, the standard procedure of occasional soil profile sampling and laboratory mass MS measurements.

Assessment of soil loss susceptibility in geodetic landmarks for the past and future climate change scenarios

Geodetic landmarks (GLs) are essential for obtaining precise height, horizontal coordinates, and the Earth's gravity field. This study aims to assess the soil susceptibility of GLs for past, present, and future scenarios, considering the projected anthropogenic effect from Coupled Model Intercomparison Project, Version 6 (CMIP6). Therefore, the soil loss estimations were made for all the GLs in the southern region of Santa Catarina state in Brazil using the Revised Soil Loss Equation (RUSLE). Our results showed average soil loss decreasing from 1985 to 2020. There was an increase in GLs in the null class (soil loss = 0 t/ha/year), mainly caused by urban growth. A decrease occurred in the low (0 t/ha/year < soil loss ≤10 t/ha/year), very severe (soil loss >200 t/ha/year), severe (50 t/ha/year < soil loss ≤200 t/ha/year), and moderate classes (10 t/ha/year < soil loss ≤50 t/ha/year). In addition, most future scenarios projected an increase in soil loss susceptibility, which also increased the GLs' susceptibility to soil loss from 2020 to 2100, albeit with lower values than the historical series. The soil loss remained stable in ssp126, slightly increased in ssp245 and ssp370, and increased in ssp585. The future scenarios only take into account changes in rainfall. Thus, the land cover change forecast would also be necessary for better analysis for future studies. Therefore, climate simulations can be used to understand the effects of climate change on soil erosion to support decision-making regarding GLs maintenance and the construction of new ones.

A resolved CFD–DEM investigation into the onset of suffusion: effect of confining pressure and stress anisotropy

AbstractThe susceptibility of a granular soil to suffusion is strongly dependent on its grain size distribution (GSD) and the mechanical and hydraulic conditions it is subjected to. This study investigates the onset of suffusion considering the effect of confining pressure and stress anisotropy using a fully resolved computational fluid dynamics and discrete element method (CFD–DEM). Three benchmarks, including the sedimentations of single and two adjacent spheres and the classic one‐dimensional (1D) consolidation are performed to demonstrate the capability of this method for high‐fidelity particle‐fluid simulations. A modified hydraulic criterion for the onset of suffusion considering stress anisotropy is presented. The microstructural changes of soil specimens before and during global suffusion are inspected, with emphasis on the evolutions of particle kinetic energy and displacements, force chain networks, and stress anisotropy. We found that the critical hydraulic gradient is negatively correlated with the confining pressure and the degree of stress anisotropy. Fine particles in the soil matrix are locally detached at small hydraulic gradients before the apparent global suffusion, as manifested by the variation of particle kinetic energy and coordination numbers. The roles of different contact types on force transmission and stress anisotropy in eroded specimens are also examined.

Material-specific interpretation of the state parameter from drained cone penetration test

The Cone Penetration Test (CPT) is a widely used site investigation tool due to its accuracy and wealth of data at a relatively low cost. Virtually all CPT interpretations explicitly or implicitly depend on how the in-situ state parameter is correlated to the tip resistance. Accurate interpretation of the state parameter from CPT is the basis for evaluating strength and liquefaction susceptibility of granular soils. The handful of interpretation methods used in the industry range between empirical and semi-empirical. As is the case for all empirical methods, extrapolating these methods outside of the original database, especially to significantly different soils such as silt-rich tailings, brings about significant risk. This paper presents a new method of interpreting the state parameter from a fully validated model of the cone penetration in sand. The method has no empirical elements and produces soil-specific correlations between the tip resistance and the state parameter. It can be easily implemented in a spreadsheet and does not require complicated analyses. The method differentiates among soils through calibration of a critical state based constitutive model, Norsand, through triaxial compression tests. The potential errors induced by not measuring soil properties are quantified.

Map-based soil crusting susceptibility assessment using pedotransfer Rules, CORINE and NDVI: A preliminary study in Greece

Map-based assessment of land degradation processes supports national monitoring and protection of the soil resources, in line with the Land Degradation Neutrality (LDN) and the Sustainable Development Goals (SDGs) initiatives. Soil crusting susceptibility, a complex expression of land degradation, with fundamental impact on soil functions, has not yet been estimated in Greek territory. To address this knowledge gap, current research uses well-known pedotransfer rules (PRLeB), partially adjusted to suit the local soil database format. The PRLeB, already applied at European scale, examine the soil crusting problem as a function of fundamental soil characteristics. From the first analysis a paradox emerged. Moderately and highly crusting prone soils were encountered in forested areas. This paradox indicated the need for a second formalization of the soil crusting problem (ePRLeB). The CORINE Land Cover (CLC) 2018 and a seasonal vegetation cover index (Normalized Difference Vegetation Index -NDVI) were used to divide the study area into categories and to capture the temporal variability of the problem, accordingly. Three land use categories emerged. The water bodies and the artificial areas were characterized as Non-evaluated areas (NE). Areas with considerable vegetation coverage (NDVI greater than 0.5) were characterized as Non-prone to crusting (NC), and the rest of the areas were characterized as Potentially prone to crusting (PC). The PRLeB approach was applied only to the PC areas. In both formalizations, the physicochemical and textural aspects of soil crusting adopted the same PRLeB. With the first formalization, 15% and 39% of the soils in Greece were characterized as very low and low susceptible to soil crusting respectively. With the second formalization 58 – 63% of the soils were characterized by no and 5 – 7% by very low crusting susceptibility. Current work explored two fundamentally different facets of the soil crusting problem. The first formalization, which can be expressed as the soil susceptibility to crusting, considers crusting as an inherent soil process. The second formalization, expressed as soil crusting susceptibility encounters crusting as a complex phenomenon involving natural but not anthropogenic factors. The study indicated that vegetation and seasonality are important factors in the map-based assessment of the observable soil crusting phenomenon. Also, it was highlighted that the unambiguous problem specification is a critical aspect for complex problem assessment and communication, particularly within an interdisciplinary context.

Comparison of Areal and Profile Distribution of Magnetic Susceptibility in Steppe Soils of the Russian Plain

A comparative analysis of areal and profile measurements of magnetic susceptibility was carried out on the plots pf 100 m2 in order to improve methods of surface soil sounding for mapping purposes and for identification of anomalies associated with anthropogenic pollution or disturbance of the surface soil layer. Two sites with Haplic Chernozems and one site with Haplic Kastanozem (Endosalic, Cambic) were studied. Additionally, a catena on the Yergeni Upland with different landscape positions (eluvial, transeluvial, transeluvial–accumulative) was studied. A comparison of the areal and profile magnetic susceptibility measured to a depth of 30 cm showed a direct correlation (R2 = 0.7). The areal survey was found to correctly determine the volumetric magnetic susceptibility ({{varkappa }_{{text{s}}}}) to a depth of 30 cm. The {{varkappa }_{{text{s}}}} variation at sites with different types of soils reflects soil–climatic zonality and spatial lithological heterogeneity expressed in different textures and mineralogical compositions of the upper (0–30 cm) soil layer within the test area of 10 × 10 m. The areal magnetic susceptibility of soils can be an important additional indicator capable of reflecting the features of soil-forming, lithological, and geochemical processes occurring in the upper soil layer. The {{varkappa }_{{text{s}}}} variation at sites in different landscape positions is due to the development of sheet erosion and changes in the direction of iron oxidogenesis depending on the position of the soil profile in the relief. The set of areal and profile magnetic susceptibility measurements can be used to study soil inhomogeneities caused by anthropogenic, paleocryogenic, geomorphological, and lithogenic factors. In particular, this approach can be applied to the study of polluted soils and monitoring of agricultural lands.

Comparison of Areal and Profile Distribution of Magnetic Susceptibility in Steppe Soils of the Russian Plain

A comparative analysis of areal and profile measurements of magnetic susceptibility was carried out in order to improve methods of surface sensing of the earth, as well as to take into account small-scale mapping of soils and the identification of anomalies associated with anthropogenic pollution or violation of the surface layer of soils. Two sites with Haplic Chernozems and one Haplic Kastanozems (Endosalic, Cambic) were studied. Additionally, a catena was studied on the territory of the Ergeninsky upland with the inclusion of sites in various positions of the landscape (eluvial, transeluvial, transeluvial-accumulative). The comparison of the areal and profile magnetic susceptibility measured to a depth of 30 cm showed a direct correlation (R2 = 0.7). It was found that the areal type of survey correctly captures the volumetric magnetic susceptibility (\({{\varkappa }_{{\text{s}}}}\)) to a depth of 30 cm. The variation of \({{\varkappa }_{{\text{s}}}}\) at sites with different types of soils reflects soil-climatic zonality and spatial lithological heterogeneity, expressed in different granulometric and mineralogical composition of the 0–30 cm layer on an area of 10 × 10 m. The areal magnetic susceptibility of soils can be an important additional indicator capable of reflecting the features of soil-forming, lithological and landscape geochemical processes occurring in the upper soil layer. Variation of \({{\varkappa }_{{\text{s}}}}\) at sites in different positions of the landscape occurs under the influence of planar flushing and a change in the direction of iron oxidogenesis processes depending on the position of the soil profile in the relief. The complex of measurements of areal and profile magnetic susceptibility can be used to study soil inhomogeneities caused by anthropogenic, paleocryogenic, geomorphological and lithogenic factors. Such an approach can be widely applied to the study of polluted soils and monitoring of agricultural land.

Mapping of the Susceptibility of Colombian Musaceae Lands to a Deadly Disease: Fusarium oxysporum f. sp. cubense Tropical Race 4

Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4) (Syn. Fusarium odoratissimum) is a devastating soil-borne pathogen that infects the roots of banana plants and causes Fusarium wilt disease. Colombia is one of the world’s leading banana producers; therefore, new uncontrolled outbreaks could have serious consequences. Despite this, little is known about the susceptibility of Musaceae lands in Colombia to Foc TR4. This work presents a pioneering study on the susceptibility of Colombian soils to Foc TR4. For this, a study was carried out to characterize climatic, edaphic, and density factors of Musaceae productive systems at the Colombian level, articulated with expert criteria to map and define areas with different levels of susceptibility to Foc R4T. These criteria are typically selected based on the existing scientific literature, consultation with domain experts, and consideration of established methods for assessing soil health and disease susceptibility in Musaceae plantations. By joining the analyzed susceptibility factors, differentiated areas were generated that imply a greater or lesser predisposition to the disease. Subsequently, a validation of the classification was made with Random Forest. The results indicate that at the level of climate, soil, and farm density as a fit factor, practically 50% of the cultivated territory of Musaceae are areas high and very highly susceptible to the pathogen (572,000 km2). The results showed that from the total Musaceae area, Antioquia, Bolívar, Chocó, and Santander turned out to be the departments with the highest proportion of very high susceptibility class of the production farms. The analysis of Random Forest classification performance shows that the model has a relatively low out-of-bag (OOB) error rate (0.023). The study on the susceptibility is highly novel and original, as it represents the first systematic investigation of Foc TR4 susceptibility in Colombian soils. This paper provides important insights into the susceptibility of Musaceae lands in Colombia to Foc TR4. The study highlights the need for ongoing monitoring, containment, and control measures to prevent the spread of this deadly pathogen and protect Colombia’s important banana industry.

Gyttja as a Soil Conditioner: Changes in Some Properties of Agricultural Soils Formed on Different Parent Materials

Organic matter is essential in improving the physical, chemical and biological properties of soils. Thus, the organic matter is widely considered a crucial indicator of environmental quality and biodiversity. In this study, the effect of gyttja addition as a soil conditioner on some physical and chemical properties of soils formed on volcanic and serpentine parent materials was investigated. The layout of the incubation study was randomized plots with 3 replications and the study lasted for 8 months to determine the value of gyttja in improving soil quality in two different parent materials. The results showed that pH, EC, total CaCO3, soil organic matter (SOM), wet aggregate stability (WSA), structural stability index (SSI), Ca-ex, Mg-ex, Fe-ex and P-av values of volcanic soils were significantly increased with increasing gyttja addition rates, while dispersion ratio (DR), Cu-ex and Cd-ex values were decreased. Likewise, pH, total CaCO3, SOM, WSA, SSI, Ca-ex and P-av values of serpentine soils were increased with increasing gyttja rates, while DR, Mg-ex, Fe-ex, Cd-ex, Ni-ex, Mn-ex, Cu-ex and Zn-ex values were decreased. The changes in the values of soil properties were statistically significant. The results demonstrated that gyttja addition overall decreased the erosion susceptibility and heavy metal contents of serpentine and volcanic soils. Moreover, the gyttja addition ameliorated some of the chemical soil properties. Therefore, gyttja could be suggested as a soil conditioner in the remediation of problematic soils.

An expression for wind erosion rate from dry and dense soil surface

AbstractWind erosion is a physical process predominated by airborne grains rather than the wind itself. The soil deformation is either elastic–plastic or fully plastic during its collisions with solid grains, corresponding to dense and loose soils, respectively. Only the fully plastic deformation was previously taken into account in the physically‐based wind erosion models. The impact erosion of dry and dense soil surface can be well quantified by the contact mechanics and strength theories. In this study, with the help of Owen's uniform saltation model, a simple expression for wind erosion rate is derived based upon the eroded volume per impact when soil deforms in the elastic–plastic manner. The new expression, a simple analytical function of several conventional variables and parameters of wind and soil, describes the effects of saltation flux and soil susceptibility. Its validity is verified by some field and laboratory experiments.

Magnetic susceptibility of soils as an ambiguous climate proxy for paleoclimate reconstructions

In soils of the temperate zone, there is an increase in the magnetic susceptibility χ of an upper layer compared to χC of parent rocks. The difference between χ and χC characterizes the magnetic “enhancement” Δχ, which is usually considered as associated with mean annual precipitation (MAP), allowing the reconstruction of MAP of the past from Δχ values of paleosols. which is widely enough used. However, in regions with a wide MAP range, non-monotonic dependence of Δχ on MAP is observed, making this reconstruction ambiguous. To construct climatic functions for reconstructing the past climate, we subdivided the south of European Russia into three regions, where climatic functions such as MAP(Δχ) of modern soils are monotonic and close to linear. These regions are relatively dry, humid, and semi-humid cold. We considered an extended set of climatic features including potential evapotranspiration (PET), actual evapotranspiration (AET), water deficit (WD = PET–AET), moisture index (MI = MAP/PET), an index of De Martonne (IDM = MAP/(MAT+10), where MAT is the mean annual temperature). The links of Δχ with MAP were positive in dry and negative in humid and semi-humid cold where they are weaker, but there were closer links with temperature-dependent WD and PET. Reliable (with R2 > 0.7) climatic functions were constructed for dry and semi-humid cold, but such reliable functions were absent in humid part. Since the differences in soil - forming material, it is necessary to identify some parameter to characterize lithological factors. For this reason, we include in consideration median grain sizes (lgSz) in soil profiles and total iron (Fet) to obtain some explanations for the results. Although the use of Δχ, lgSz and Fet together made the climatic functions more reliable (R2 ∼ 0.8), but Δχ played the main role, while lgSz and Fet were not always significant. Based on the obtained data, it appears possible to provide a more detailed subdivision of paleoecological periods in the Late Holocene for the steppe and forest-steppe zones of the Eastern Europe. Taking into account the diversity of soil conditions in different regions, equations using soil profile MS enhancement to reconstruct rainfall should be used locally and regionally, taking into account the identified limitations and eliminating the possible ambiguity of reconstructions.

Discussion on the frost susceptibility of sandy soil under hydraulic pressure

A non-frost susceptibility soil is generally not considered to generate significant frost heave. However, recent researches indicate that significant frost heave occurs in coarse fill in engineering, which implies that the frost susceptibility classification based on fine content and particle size may be not reliable. To investigate the frost susceptibility of sandy soil under hydraulic pressure, nine groups of 1-D freezing tests based on the orthogonal array are conducted considering the combination of hydraulic pressure, cooling temperature, fine content and dry density. The results indicate that considerable frost heave occurs in freezing sandy soil. A multivariate regression model is developed to predict the frost heave ratio and to assess the frost susceptibility of sandy soil. From the regression equation, the hydraulic pressure has the largest influence on frost heave ratio of sandy soil, followed by fine content, and the effect of cooling temperature and dry density on sandy soil frost heave can be ignored. In addition, it is found that the reliability of the current standards is poor when assessing the frost susceptibility of sandy soil. The invalidation for frost susceptibility classification is owing to the increased saturation and the increased driving force for water migration. It is proposed that the PWP at the base of freezing front can be used as an indicator for assessing the frost susceptibility of soil.

A Geospatial Modelling Approach to Understand the Spatio-Temporal Impacts of Grazing on Soil Susceptibility to Erosion

Grazing management to reduce soil erosion is paramount for preserving and enhancing grassland health under pastoral livestock production systems. However, as the focus of these production systems is to increase productivity, the inclusion of the soil and its complexity in grazing management has been usually neglected. Detailed consideration of the soil spatio-temporal susceptibility to erosion may be best approached with simulation modelling. To understand and explore the spatio-temporal impact of grazing strategies on soil surface erosion, this work used a geospatial model approach in a high-country pastoral livestock production system in New Zealand as a case study. We modelled 45 scenarios characterized by different stock densities and occupation periods applied for each season of the year and for different livestock types: sheep, beef, and deer, producing a total of 540 scenarios. In addition, we included scenarios to represent ungrazed pastures for each season and the current grazing management of the case study station as the baseline for comparisons (resulting in a total of 545 scenarios). Spatio-temporal variation of natural soil superficial erosion from ungrazed pastures appears to be more relevant than the impact of manipulating grazing intensity and indicates that paddocks in our study area have different capacities to support grazing which also changes during seasons. Increases in occupation period seem more detrimental to soil erosion compared to increases in stock density, and cattle are the most detrimental stock type compared to sheep and deer. Our results suggest that grassland health can be enhanced in LUMGS by applying context-adjusted grazing management strategies according to the station spatio-temporal heterogeneity and susceptibility to erosion.

A new and simple method for predicting the collapse susceptibility of intact loess

The collapse susceptibility of intact soil should be determined before designing infrastructures in loess regions. It is significantly affected by many factors, including soil type (i.e. sandy, silty or clayey loess), moisture, porosity, stress and structure. So far, many relevant empirical equations and theoretical models were reported in the literature. Each empirical equation has a narrow application range and the theoretical models cannot be easily calibrated. In this study, a new and simple method was developed to predict the loading- and wetting-induced collapse of intact loess within the elasto-plastic framework. The compression curves of intact loess under saturated and unsaturated conditions were normalised using the void index and applied to analyse the loading- and wetting-induced collapse. This method can readily be used by engineers to predict the collapse potential in a wide range of loess types and conditions, with the input of only three state variables (i.e. initial void ratio, vertical stress and initial water content) and the void ratio at the liquid limit state. To verify this new method, it was applied to simulate about 200 laboratory wetting tests and one in-situ ponding test. The measured and predicted results are reasonably matched, demonstrating a good capability of the method.

Magnetic susceptibility of the slope soils for predicting of agronomic characteristics

The article is related to the study of the localization of agronomic heterogeneities of the soil distributed on slopes. To study this important agricultural areas, we usedthe mathematical modeling of erosion processes and the survey of the magnetic susceptibility of the arable horizon of the soils. The experiment design includes the typical chernozemof the slope.The soil sampling was performed according to DSTU 4287:2004, determination of organic carbon content according to DSTU 4289:2004, and determination of statistical indicators using Statistica®. The visualization of the study results was carried out in the QGis software. Magnetic susceptibility (MS) was measured using a KLY-2 magnetometer. Modeling of soil erosion processes involved USLE universal soil loss equation. A 1:10,000 topographic map was adopted as the topographic basis. The research territory is the fields of the National Biotechnological University (V.V. Dokuchaev KhNAU) on the southern outskirts of the city of Kharkiv. The 70 soil samples were collected from the arable layer (horizon A). Due to the course of water erosion processes, a long-term soil washout and a widespread complex spatial complex of washed-out soils took place on the site, which is a typical case for eroded sloping lands of the Forest Steppe. In non-eroded watersheds (in the north-western direction), typical heavy loamy medium-humus chernozems are developed. Sampling was carried out using an irregular grid, the sampling density was about 5 samples per hectare.We detected that mathematical modeling of erosion processes can be used to predict the location of inhomogeneities in the agronomic properties of the ground cover of sloping lands. However, given the shortcomings of the main models of potential soil losses associated with the alternation of zones of erosion and deposition require to clarify and verify the obtained results. Hence, we propose to apply the statistical characteristics of the spatial distribution of values of the magnetic susceptibility of the soil. The most important parameters are the average values and coefficient of variation of MS.

Susceptibility of the Surrounding Soil and Rock by the Electrical Resistivity Method

The research area is located in Banga, Soppeng Regency, South Sulawesi Province. The purpose and intent of this research is to determine the resistivity value of the material layer, identify the characteristics of the slip plane and its relationship to the plasticity properties and the characteristics of the clay minerals contained in the soil. The method used to collect field data includes surface geological data and subsurface geology, which are the electrical resistivity data and surface soil data, then interpreted by combining topographiccross-sectional data and subsurface geoelectrical data along the measurement path. The first slip plane is curved as well as the second slip plane is the residual soil resulting from weathering of limestone which is still above the less dense and thick parent rock (in situ). The geochemistry of the soil samples showed that the mineral content in each layer had the largest percentage of illite 54.4% - 69.9%, and montmorillonite 6.1% - 13.6%, these two clay minerals have large shrinkage properties. Plasticity Index 29.8% - 35.8%, causing vulnerability to the soil, so that the mass movement on the sliding plane is moderate and active in slow motion. The mass movement in the slip plane can be categorized into creep type.

Can Organic Matter from Waste-Derived Amendments Limit Phosphorus Losses from Soil to the Aquatic Environment?

When introducing innovative waste-derived amendments, their potential impact on soil retention capacity towards phosphorus (P) should be accounted for to limit its losses and thus water eutrophication. The study was aimed at evaluating P sorption properties of organic waste-derived amendments conifer woodchip biochar (BIO) and brown coal waste (BCW), and assessing their impact on P sorption properties in soil five years after their application in terms of limiting P losses from soils to the water sources. In batch tests samples of amendments and sandy acid soil (Haplic Luvisol) were exposed for 24 h to balancing solutions with a different P content, respectively 0–80 mg P L−1 for amendments and 0–20 mg P L−1 for soil. Three treatments were studied: (1) conifer woodchip biochar (BIO, (2) brown coal waste (BCW) and (0) soil without amendment (control). Organic amendments were applied to soil at a rate equivalent of 10.2 t C ha−1 once at the start of the trial and they amounted to 24.2 t ha−1 for BCW and 12.8 t ha−1 for BIO. Based on the results of the bath tests and the Langmuir and Freundlich equations, sorption parameters of P were determined for BIO, BCW and the soil after their application. The maximum sorption capacities (Smax) of BIO and BCW were 832.3 and 250.4 mg kg−1, respectively, and were controlled mainly by the organic surfaces of their structures. Within the range of concentrations used in the balancing solutions (5–20 mg P L−1), sorption of P was generally higher in unfertilized soil compared to soil amended with BCW and BIO. The application of BIO significantly (p &lt; 0.05) decreased the Smax (17%), while BCW decreased the bonding energy of P (k) by 15% compared to the untreated soil. The content of dissolved P increased significantly in the case of both BCW and BIO applications, which may indicate an increase in soil susceptibility to P losses. However, the effectiveness of these amendments in limiting P losses with the use of other doses and in different soil and climatic conditions cannot be excluded. Further research is recommended to better understand the effect of biochar feedstock and temperature of its production on P retention/losses in various types of soils.

Mapping of the wind erodible fraction of soil by bidirectional gated recurrent unit (BiGRU) and bidirectional recurrent neural network (BiRNN) deep learning models

The destructive consequences of wind erosion have been reported in many studies, but accurate assessment of wind erosion is still a challenge, especially on large scales. Our research introduces two deep learning (DL) algorithms consisting of bidirectional gated recurrent unit (BiGRU), and bidirectional recurrent neural network (BiRNN) for spatial mapping of wind-erodible fraction of the soil (EF). EF was measured in 508 soil samples using the Chepil method. 15 key factors controlling EF including: soil, topography, and meteorology parameters were mapped. The performance of the most efficient DL model was interpreted by Game theory. The uncertainty of the DL models was quantified by deep quantile regression (DQR). Results showed that both DL models were performed very well with the BiRNN performing slightly better than BiGRU. The aggregate mean weight diameter (MWD) was a key variable for the mapping of soil susceptibility to wind erosion. Based on the BiRNN model, most of the study region was moderately and highly susceptible to wind erosion regarding the EF value (between 32 and 98). This indicates the urgent need for soil conservation measures in the region. The DQR results showed that the observed values of EF fell within the EF values predicted by the model. Overall, the suggested methodology has proven to be helpful in mapping wind erosion susceptibility on a large scale.

Mitigating embankment frost heave with nano-ZnO in the Arctic

Non-frost susceptible soils (e.g., gravel) are typically used as embankment fill to minimize the frost heave problem on the highways in the Arctic. However, accesses to the non-frost susceptible soils are limited in the remote regions, and the transportation costs for it are very high, thereby resulting that frost susceptible soils have to be used to fill the embankments. In this study, nano-ZnO was added to two types of frost susceptible soils, namely silty clay and clay, to reduce the frost susceptibility of soils and to mitigate the frost heave. Firstly, the unconfined compressive strengths of the soil samples whose the mass ratios of the nano-ZnO to the silty clays were 1.5 wt%, 3.0 wt%, 4.5 wt% and 6.0 wt% were tested. A series of isotropic freezing tests were then conducted to study the temperatures and frost heave deformations of the soil samples with the nano-ZnO of 0.0 wt%, 1.5 wt%, 3.0 wt% and 4.5 wt%, thereby verifying the effectiveness of the nano-ZnO in reducing the frost susceptibility of the soils. The optimal mass percentage of the nano-ZnO was determined by the mechanical and freezing tests. Finally, a clay embankment model with the nano-ZnO of the optimal mass percentage (defined as the nano-ZnO embankment model) during freezing-thawing cycles under various artificial rainfall conditions in the Arctic environment was tested. A clay embankment model without nano-ZnO was the control case, and defined as the control embankment model. Experimental results revealed that 1) with the increased nano-ZnO, the unconfined compressive strengths of the soil samples initially increased and subsequently decreased, and the maximum value corresponded to the mass percentage of 4.5 wt%; 2) the usage of the nano-ZnO can considerably reduce the freezing point and the frost heave deformations of the soil samples; 3) the optimal mass percentage of the nano-ZnO was 4.5 wt%. Compared with the soil sample without the nano-ZnO, the frost heave deformation of the soil sample with the nano-ZnO of 4.5 wt% was reduced by 71.98% and 78.44% using the rapidly cooling and step by step cooling method, respectively; 4) the usage of 4.5 wt% nano-ZnO was reduced the frost heave deformation of the clay embankment model by a maximum value of 74.06% under artificial rainfall, whereas the frost heave deformation of the embankment model reduced by a maximum value of 31.94% without artificial rainfall. Moreover, the mechanisms of the increase in the compressive strength and the decrease in the frost heave were analyzed. This study can provide considerable insights for mitigating the frost heave problems in highways in the Arctic when frost susceptible soil is used as embankment fill.

Long-term manure fertilization increases rill erosion resistance by improving soil aggregation and polyvalent cations

Application of organic fertilizers is a potential practice to prevent soil erosion by changing the physicochemical properties of the soil, such as macroaggregates, soil organic carbon (SOC) content, and exchangeable cations. However, the practical performance of organic fertilizer in soil erosion after a long-term application has scarcely been reported. To reveal the response of soil erosion resistance (i.e., the soil susceptibility to resist external erosion force) to 43 years of organic fertilization, five treatments were investigated: (1) CK (no fertilizer), (2) NPK (mineral fertilizer), (3) M (pig manure), (4) MN1 (pig manure + 138 kg N ha−1), and (5) MN2 (pig manure + 276 kg N ha−1). The results showed that NPK, M, MN1, and MN2 significantly increased soil critical shear stress (τc) by 54 %, 87 %, 101 %, and 67 %, respectively, compared to CK. However, rill erodibility (kd) was increased significantly only in the MN2 treatment. The optimal partial least squares regression model showed that the increase in soil exchangeable Ca2+ was the dominant contributor to the τc increase, while soil mean weight diameter (MWD) had the greatest negative effect on kd. Compared with CK, the soil exchangeable Ca2+ in M and MN1 increased significantly by 123 % and 135 %, respectively. The MWD in M and MN1 increased by 86 % and 83 %, respectively, compared with that in CK. The application of pig manure was beneficial for decreasing exchangeable Na+ and increasing SOC content, which could improve MWD. Manure with a high N content did not increase MWD due to SOC decomposition. Our results indicate that the long-term application of manure, alone or combined with moderate N, improves rill erosion resistance.