Search Results (845)

The nitrogen/N dynamic is complex and affected by soil management (i.e., residue accumulation and correction/fertilization). In soil, most of the N is combined with organic matter (organic forms), but the N forms absorbed by plants are ammonium/NH₄⁺ and nitrate/NO₃⁻ (inorganic forms). The N recommendation for agriculture crops does not observe the N available in the soil (organic or inorganic), indicating a low efficiency in nitrogen management in soil. Based on the hypothesis that the stocks of NO₃⁻ and NH₄ can be used as indicative of N status in soil but with high variation according to soil factors (soil uses and management), the objective of the study was to (i) analyze the balance of nitrate and ammonium in tropical soil with different uses and management and (ii) use machine learning to explain the nitrogen dynamic in soil and the balance of nitrate and ammonium. The results showed that soil N stocks and pH promoted the formation of three clusters with the similarity between Cluster 1 (clay texture) and Cluster 2 (loam texture), represented by higher contents of nitrate as a result of high nitrification rate and lower contents of ammonium in soil. Cluster 3 (sand texture) was isolated with different N dynamics in the soil. In agricultural soils, the content of NO₃⁻ tends to be higher than the content of NH₄⁺. There is a high nitrification rate in clay soil explained by higher organic matter and clay content that promotes soil biology. Based on the results of machine learning, for clay and loam soil, the contents of NO₃ can be used as indicative of N status as a final result of nitrification rate and higher variation in soil. However, in sandy soil, NO₃ can not be used as indicative of N status due to N losses by leaching. Full article

In this article, a nonlinear static analysis model of a bridge pile foundation is established using numerical simulation, and the correctness of the model is verified via experiments. Then, the damage characteristics and mechanical behaviors of bridge pile foundations in cold regions under lateral loads are investigated based on the validated analysis model. The results showed that the impact of soil freeze–thaw cycles on the lateral performance of the pile–soil system is more pronounced in seasonally frozen regions compared with permafrost regions. Specifically, as the number of soil freeze–thaw cycles increases, there is a tendency for the lateral load capacity of the pile–soil system to decrease initially and then stabilize. It is worth noting that soil freeze–thaw cycles significantly influence both the stiffness and deformation capacity of the pile–soil system, with these parameters exhibiting a decreasing trend followed by stabilization as the number of freeze–thaw cycles increases. However, it has little effect on the shear force and bending moment of the pile foundation. Full article

Brazilian soils are predominantly rich in aluminum, which becomes mobile at pH < 5, affecting sensitive plants; however, some species have developed aluminum tolerance mechanisms. The purpose of this study was to compare the physiological responses of Crotalaria genus species, family Fabaceae, which have the ability to associate with nitrogen-fixing bacteria under the influence of Al³⁺ in the soil. The soil used was Oxisol; the experimental design was in randomized blocks in a factorial scheme (2 × 3): soil factor (available toxic aluminum content; correction of dolomitic limestone—MgCO₃) and species factor (C. juncea; C. spectabilis; C. ochroleuca); cultivated within 43, 53, and 53 days, respectively, with five replications; 30 experimental samples. Mass and length, pigments, gas exchange, and changes in nitrogen metabolism were evaluated. C. juncea showed a higher concentration of amino acids in the leaves, internal carbon, and stomatal conductance in soil with Al³⁺, as well as higher production of ureides, allantoinic acid, allantoic acid, proteins, and amino acids in the nodules, with 78% of the Al³⁺ accumulation occurring in the roots. C. ochroleuca demonstrated greater shoot length and nodule number production in limed soil; in soil with Al³⁺, it showed a 91% increase in chlorophyll a content and 93% in carotenoids. C. spectabilis showed a 93% increase in ureide production in the leaves in soil with Al³⁺. Full article

The Tarim River Basin is one of the most ecologically fragile regions around the world in the arid areas of Northwest China. The study of natural vegetation ecological water requirement (EWR) is the basis for the promotion of regional ecological conservation and sustainable development of ecosystems when extreme environmental events occur frequently, which is of great significance for the formulation of scientific and rational ecological conservation strategies. In the study, we improved the vegetation EWR calculation method by introducing a dynamic soil moisture limitation coefficient (K_S) and a dynamic vegetation coefficient (K_C) that is coupled with a resistance correction factor (F_r) based on the Penman-Monteith method and analyzed its spatio-temporal variation characteristics. Additionally, this study utilized the latitude of ecosystem resilience (LER) to clarify the thresholds for vegetation EWR throughout the growing season in the study area and to analyze the water surplus and deficit (WSD) at different threshold levels. The results of the study show that: (1) Over the past 21 years, the EWR for vegetation has shown a downward trend, with the change in EWR for arbor-shrub forests being more significant than that for grasslands. The average EWR for arbor-shrub forests and grasslands is 36.76 × 10⁸ m³ and 459.59 × 10⁸ m³, respectively. (2) The minimum ecological water requirement (EWR_min) and optimal ecological water requirement (EWR_opt) for natural vegetation were 360.45 × 10⁸ m³ and 550.10 × 10⁸ m³, respectively. (3) In EWR_min conditions, the alpine plateau area as a whole showed a water surplus, and the plains area as a whole was in a state of water scarcity, but the precipitation in the study area as a whole could meet the basic survival needs of the vegetation. (4) In EWR_opt conditions, the plains and local alpine plateau areas are in a state of water scarcity, the area of water scarcity is gradually increasing, and the regional precipitation is unable to fully realize the objectives of ecological conservation and vegetation restoration. Full article

Arsenic (As) contamination in groundwater represents a major global health threat, potentially impacting billions of individuals. Elevated As concentrations are found in river floodplains across south and southeast Asia, as well as in the inland basins of China, despite varying sedimentological and hydrogeochemical conditions. The specific mechanisms responsible for these high As levels remain poorly understood, complicating efforts to predict and manage the contamination. Applying hydro-chemical, geological, and soil parameters as explanatory variables, this study employs multiple linear regression (MLIR) and random forest regression (RFR) models to estimate groundwater As concentrations in these regions. Additionally, random forest classification (RFC) and multivariate logistic regression (MLOR) models are applied to predict the probability of As levels exceeding 10 μg/L in the Hetao Basin (China) and Bangladesh. Model validation reveals that RFR explains 80% and 70% of spatial variability of As concentration in the Hetao Basin and Bangladesh, respectively, outperforming MLIR, which accounts for only 35% and 32%. Similarly, RFC outperforms MLOR in predicting high As probability, achieving correct classification rates of 98.70% (Hetao Basin) and 98.25% (Bangladesh) on training datasets, and 82.76% (Hetao Basin) and 91.20% (Bangladesh) on validation datasets. The performance of the MLOR model on the validation set yields accuracy rates of 81.60% and 72.18%, respectively. In the Hetao Basin, Ca²⁺, redox potential (Eh), Fe, pH, SO₄²⁻, and Cl⁻ are key predictors of As contamination, while in Bangladesh, soil organic carbon (SOC), pH, and SO₄²⁻ are significant predictors. This study underscores the potential of random forest (RF) models as robust tools for predicting groundwater As contamination. Full article

Bitter vetch (Vicia ervilia Willd.) is a traditional Mediterranean–West Asian legume, mainly used as livestock feed because of its toxic non-proteinogenic amino acid, canavanine. However, historical sources suggest its past human consumption. Currently, bitter vetch is a minor crop confined to marginal soils in semi-arid regions, presenting a potential alternative protein source amid projected climate changes. This study evaluated the nutritional and sensory attributes of bitter vetch seeds processed through various household methods. Germination and cooking significantly reduced the canavanine content by 28% and 60%, respectively. Incorporating bitter vetch flour (BVF) into wheat bread enhanced protein and fiber contents without substantially altering carbohydrate and lipid levels, and the baking process reduced the canavanine content by 40%. Bitter vetch flour enriched the bread with iron and calcium, contributing significantly to their daily nutritional intakes. Sensory evaluations indicated positive reception for bread with 12% BVF, achieving a balance between nutritional enhancement and consumer acceptance. This study identifies bitter vetch seeds as a valuable resource for improving bread formulations with corrected gluten contents and enhanced protein quality, as measured using protein-digestibility-corrected amino acid score (PDCAAS) values. With strategic processing and formulation adjustments, bitter vetch has the potential to re-emerge as a feasible high-protein grain crop, promoting sustainable farming. Full article

To provide the necessary theoretical models of sphere–soil interaction for the structural design, motion control, and simulation of spherical robots, this paper derives analytical expressions for traction force and driving torque when spherical robots slide and sink into sandy terrain, based on terramechanics and multibody dynamics. Furthermore, orthogonal experimental analysis identifies the load, joint angular acceleration, and maximum joint angular velocity of spherical robots as influencing factors, highlighting that the load significantly affects their longitudinal motion performance. Experimental results indicate that rolling friction and additional resistance on sandy terrain cannot be ignored. The corrected theoretical model effectively replicates the temporal variation of driving torque exerted by spherical robots on sandy terrain. Numerical computations and experimental analyses demonstrate that increasing the radius of the sphere shell, the load, and the slip ratio all lead to increased traction force and driving torque. However, traction force and driving torque begin to decrease once the slip ratio reaches approximately 0.5. Therefore, in the design of spherical robot structures and control laws, appropriate parameters such as load and slip ratio should be chosen based on the established sphere–soil interaction theoretical model to achieve high-quality longitudinal motion performance on sandy terrain. Full article

The correct prediction of heating network pipeline failure rates can increase the reliability of the heat supply to consumers in the cold season. However, due to the large number of factors affecting the corrosion of underground steel pipelines, it is difficult to achieve high prediction accuracy. The purpose of this study is to identify connections between the failure rate of heating network pipelines and factors not taken into account in traditional methods, such as residual pipeline wall thickness, soil corrosion activity, previous incidents on the pipeline section, flooding (traces of flooding) of the channel, and intersections with communications. To achieve this goal, the following machine learning algorithms were used: random forest, gradient boosting, support vector machines, and artificial neural networks (multilayer perceptron). The data were collected on incidents related to the breakdown of heating network pipelines in the cities of Kazan and Ulyanovsk. Based on these data, four intelligent models have been developed. The accuracy of the models was compared. The best result was obtained for the gradient boosting regression tree, as follows: MSE = 0.00719, MAE = 0.0682, and MAPE = 0.06069. The feature «Previous incidents on the pipeline section» was excluded from the training set as the least significant. Full article

Geostatistical prediction methods are increasingly used in earth sciences and engineering to improve upon our knowledge of attributes in space and time. During mining activities, it is very important to have an estimate of any contamination of the soil and groundwater in the area for environmental reasons and to guide the reclamation once mining operations are finished. In this paper, we present the geostatistical analysis of the water content in certain pollutants (Cd and Mn) in a group of mines in Northern Greece. The monitoring points that were studied are 62. The aim of this work is to create a contamination prediction map that better represents the values of Cd and Mn, which is challenging based on the small sample size. The correlation between Cd and Mn concentration in the groundwater is investigated during the preliminary analysis of the data. The logarithm of the data values was used, and after removing a linear trend, the variogram parameters were estimated. In order to create the necessary maps of contamination, we employed the method of ordinary Kriging (OK) and inversed the transformations using bias correction to adjust the results for the inverse transform. Cross-validation shows promising results ($\rho =65\%$ for Cd and $\rho =52\%$ for Mn, RMSE = 25.9 ppb for Cd and RMSE = 25.1 ppm for Mn). As part of this work, the Spartan Variogram model was compared with the other models and was found to perform better for the data of Mn. Full article

Using coal gangue as a subgrade filler will produce good benefits, and its application prospects are very broad. It is of great engineering and scientific value to study the improvement method and dynamic characteristics of coal gangue subgrade filler under traffic load. Combining the properties of coal gangue material, fly ash and lime and soil were added to improve the bearing behavior of coal gangue subgrade filler. Then, a compaction test was carried out using the principle of orthogonal experimental design. By analyzing the compaction test results, the optimal proportion of each additive was obtained. A large-scale dynamic triaxial test was carried out with the proportion of each admixture in the maximum dry density group in the compaction test. Based on the dynamic triaxial test results, the effect of confining pressure on the permanent strain was analyzed, the analysis model of permanent deformation and cycle number of traffic loading was proposed, and the correctness of the model was verified. In addition, a modified Hardin–Drnevich model was established, which can describe the dynamic stress–dynamic strain curve of coal gangue subgrade filler under traffic load, and then, the dynamic modulus and damping ratio were analyzed. Full article

This study investigated the suitability of X-ray fluorescence (XRF) analysis for routine multi-elemental composition analysis, checking its analytical capabilities by measuring a wide array of certified reference materials of soil and plant origin. A portable XRF analyzer was used to evaluate 32 soil and 12 plant standard materials, using both the Soil and Geochem mode, with sequential beams, allowing the detection of a wide range of elements. Recovery rates were calculated by comparing XRF measurements with certified values, and their correlations were verified through the Spearman coefficient. The results demonstrated the reliability of XRF measurements for soil samples, with a large number of elements showing a good or very good recovery and strong correlations with certified values. For plant samples, XRF largely overestimated the certified values, but the strong statistically significant correlations for almost all tested elements allowed us to correct this systematic bias, using the reported median value for dividing the value obtained via XRF. The Geochem mode emerged as more reliable for a larger number of elements. It was concluded that XRF may be a suitable alternative to ICP-MS in routine multi-elemental composition analysis. Full article

Geosynthetics have increasingly been applied to geotechnical engineering works due to their numerous advantages, including cost-effectiveness and their significant role in sustainable development. When geosynthetics are used as reinforcement in earth structures, such as embankments, retaining walls and bridge abutments, soil–geosynthetic interface shear behavior is a critical parameter involved in the design. This paper presents a series of monotonic and cyclic/post-cyclic pullout tests carried out to examine the apparatus scale effect on the pullout response of a geogrid embedded in two different soils. To assess the small-scale equipment feasibility, comparisons were made between pullout test parameters derived from small- and large-scale equipment. The test results indicate that, under a low confining stress of 25 kPa, using a smaller-sized apparatus results in lower values of geogrid pullout resistance and maximum mobilized shear stress, but higher values of confined tensile stiffness at low strains. On the other hand, as the confining stress increases (i.e., 50 kPa and 100 kPa), the difference between the results becomes less significant and similar trends are observed regardless of the equipment type. Adopting small-scale equipment enables obtaining soil–reinforcement interaction parameters using test procedures that are less time-consuming than those associated with large-scale pullout tests. However, proper scale effect correction factors may be considered for more consistent estimates of the interface strength parameters under low normal stress values. Full article

High rates of limestone have been increasingly utilized in newly converted areas for grain production in agricultural frontier regions to expedite the short-term correction of soil fertility, leading to compensatory yields. However, there is a lack of information about different doses of lime and gypsum for soils in the Cerrado of Matopiba, especially in the state of Piauí, Brazil. The aim of this study was to evaluate the effects of doses of lime and gypsum in newly converted areas for soybean production in the Cerrado of Southwest Piauí. The study was carried out in the 2019/2020 and 2020/2021 crop years, on yellow Oxisol soil, in a randomized block design and treatments following a 5 × 4 factorial: five lime rates (0, 5, 10, 15, and 20 t ha⁻¹) and four gypsum rates (0, 1, 2 and 4 t ha⁻¹), with four replicates. The standard lime and gypsum rates were 5 t ha⁻¹ and 1 t ha⁻¹, respectively. Soil fertility attributes (0.0–0.2, 0.2–0.4, and 0.4–0.6 m), nutritional status of plants, and soybean yield were measured. The increases in grain yield using a lime rate of 10 t ha⁻¹ were 18% and 12% in the 2019/2020 and 2020/2021 crop years, respectively. High lime rates provide a reduction in the concentrations of P, K, and cationic micronutrients in soil, thereby reducing leaf contents of macro- and micronutrients in soybean plants. Concentrations of Ca, Mg, and S in subsurface layers were raised to proper levels, similar to those recommended for topsoil (0.0–0.2 m). The use of gypsum and lime in newly converted areas for soybean cultivation provides quick improvement in soil chemical conditions and reduction in acidity components. The application of 10 t ha⁻¹ of lime improved the soil chemical environment in the Matopiba region the short time available for chemical reactions to occur, allowing soybean cultivation in newly converted areas of Cerrado into agriculture. Full article

Mechanically connected precast piles are a type of precast piles that utilise snap-type mechanical connectors to restrain the pile ends of two identical or different precast piles at the top and bottom so as to quickly realise the purpose of the connection. However, the gap problem in the connectors of mechanically connected piles can lead to uneven and uniform deformation of the piles under horizontal loading, resulting in additional displacements and rotation angles of the piles at the connection. Solving the problem of calculating the internal force response of discontinuous deformed piles is a prerequisite for promoting and applying mechanically connected precast piles. Firstly, the theoretical derivation of mechanically connected piles with fixed constraints at the pile bottom is carried out. Secondly, the pile response equations of mechanically connected piles are established, and the theoretical solutions of pile displacement and internal force response of mechanically connected piles under horizontal loading are derived. Thirdly, the pile-soil model of the test pile is established using ABAQUS software (ABAQUS 2016) in combination with the design data of the test pile. The numerical simulation displacements and angles of rotation are compared with the test results. Finally, the theoretical and numerical simulation displacements and internal forces of the ordinary pile and the mechanically connected pile are compared. The relative errors of the displacements and angles of rotation of the established pile-soil model are less than 10%, indicating that the established model has good accuracy. The relative errors of the theoretical and numerical simulation displacements and internal forces of the mechanically connected pile are less than 10%, proving the correctness of the theoretical calculation by the m-method. This study can provide effective theoretical support and methodological guidance for the displacement and internal force response of discontinuous piles. Full article