High Soil Research Articles

Theoretical model and parameter sensitivity analysis of the filter cake formation during slurry shield tunnelling

The filter cake formation during slurry shield tunneling in high permeability soil layers is complex and difficult to monitor. There is no reliable method to evaluate the mechanical characteristics during the filter cake formation. A theoretical model is proposed to describe the filter cake formation and development in this study. The finite difference method is used to simulate the whole filter cake formation process. In addition, the influence of the key bentonite slurry parameters and of the deep infiltration on the filter cake formation is investigated based on the proposed model. The results show that the excess pore water pressure within the filter cake is not uniformly distributed. The slurry support effect is manifested by a pressure drop generated on both sides of the filter cake. The development process of the filter cake can be summarized into three stages: prior infiltration filling of the filter cake, accumulation and thickening of the new filter cake, and compression and consolidation of the prior filter cake. The slurry deep infiltration results reflected by the membrane specific resistance have the most significant effect on the filter cake development. Compared with the slurry concentration, the viscosity has a greater influence on the formation and final thickness of the filter cake.

Vigna marina as a Potential Leguminous Cover Crop for High Salinity Soils

The beach bean (Vigna marina) exhibits robust growth in habitats characterised by sandy substrates, limited nutrient availability, and elevated saline levels. The utilisation of V. marina, a potentially beneficial leguminous cover crop, allows for its cultivation in regions characterised by soil salinity, hence facilitating the alleviation of environmental stress and the promotion of nitrogen fixation within the soil. A study assessed the feasibility of V. marina as a leguminous cover crop, in which this legume was cultivated in both coastal and inland soils. Pueraria javanica and Mucuna bracteata, widely recognised as established leguminous cover crops, were used as the control in this experiment. The observations involved were total plant biomass, nitrogenase activity, and leaf chlorophyll content of the host plants. The experiment consisted of five replicates arranged in a randomised complete block design, respectively. The effects of commercialised rhizobial compost on the development of the leguminous plants planted in both plots were also investigated. The results indicated that V. marina flourished in coastal and inland soils with the highest leaf chlorophyll concentration throughout the eight weeks of growth. It showed that V. marina has the potential to outperform the other two established leguminous cover crops when planted in highly salinised soils. The results also showed evidence that V. marina was an excellent potential leguminous cover crop, especially for any agricultural plots of high salinity soils, compared to the other two well-established leguminous cover crops, P. javanica and M. bracteata.

Clonal integration benefits Calystegia soldanella in heterogeneous habitats

Abstract Land-use change and tourism development have seriously threatened the ecosystems of coastal protection forests and beaches. Light and nutrients are spatially heterogeneously distributed between the two ecosystems. Clonal plants, such as Calystegia soldanella, which play a crucial role in maintaining the ecological stability of coast habitats, are likely to encounter diverse environments. In this study, we investigated clonal integration and the division of labor in C. soldanella under heterogeneous (high nutrient and low light [HNLL]; low nutrient and high light [LNHL]) and homogeneous habitats. We cultivated pairs of connected and severed ramets of C. soldanella in these environments. Our results showed the total biomass (TB) of connected ramets was higher than that of severed ramets in heterogeneous environments, suggesting clonal integration enhances growth in heterogeneous habitats. The root shoot ratio was significantly lower in HNLL than in LNHL conditions for connected ramets, demonstrating a division of labor in growth under heterogeneous conditions. However, parameters of clonal propagation of C. soldanella did not significantly differ between connected and severed ramets in heterogeneous environments, indicating no division of labor in clonal propagation. In homogeneous environments, the growth of C. soldanella did not benefit from clonal integration. Connected ramets in heterogeneous habitats exhibited higher TB than in homogeneous habitats. The TB of one ramet in HNLL was consistently higher than that in LNHL, irrespective of ramet’s states, which suggests that high soil nutrients may enhance the growth. We conclude that C. soldanella has the capability of clonal integration to achieve high biomass in heterogeneous but not in homogeneous conditions, and the establishment of coastal protection forests (high nutrient and low light) may foster the growth of C. soldanella.

Endophytes Alleviate Drought-Derived Oxidative Damage in Achnatherum inebrians Plants Through Increasing Antioxidants and Regulating Host Stress Responses

Endophytes generally increase antioxidant contents of plants subjected to environmental stresses. However, the mechanisms by which endophytes alter the accumulation of antioxidants in plant tissues are not entirely clear. We hypothesized that, in stress situations, endophytes would simultaneously reduce oxidative damage and increase antioxidant contents of plants and that the accumulation of antioxidants would be a consequence of the endophyte ability to regulate the expression of plant antioxidant genes. We investigated the effects of the fungal endophyte Epichloë gansuensis (C.J. Li & Nan) on oxidative damage, antioxidant contents, and expression of representative genes associated with antioxidant pathways in Achnatherum inebrians (Hance) Keng plants subjected to low (15%) and high (60%) soil moisture conditions. Gene expression levels were measured using RNA-seq. As expected, the endophyte reduced the oxidative damage by 17.55% and increased the antioxidant contents by 53.14% (on average) in plants subjected to low soil moisture. In line with the accumulation of antioxidants in plant tissues, the endophyte increased the expression of most plant genes associated with the biosynthesis of antioxidants (e.g., MIOX, crtB, gpx) while it reduced the expression of plant genes related to the metabolization of antioxidants (e.g., GST, PRODH, ALDH). Our findings suggest that endophyte ability of increasing antioxidant contents in plants may reduce the oxidative damage caused by stresses and that the fungal regulation of plant antioxidants would partly explain the accumulation of these compounds in plant tissues.

Geoinformatics-Based Mapping of Environmental Sensitive Areas for Desertification over Satara and Sangli Districts of Maharashtra, India

Desertification processes in arid, semi-arid, and dry sub-humid conditions have been enhanced in recent decades. The geospatial database and associated satellite data can be effectively employed for regional planning to address desertification and land degradation. In this study, the Mediterranean Desertification and Land Use (MEDALUS) model has been used to map environmentally sensitive areas due to desertification in the Satara and Sangli districts of Maharashtra, India. This was achieved by combining Landsat-8 multispectral data, Census data, soil data, and climatic variables like temperature, rainfall, and evapotranspiration. The algorithm of MEDALUS is the geometric mean of four indicators, namely soil quality index (SQI), climate quality index (CQI), vegetation quality index (VQI), and socio-economic quality index (SEQI). The findings indicated that the majority of the study area comes under the potential category of desertification (60.32%) followed by fragile (27.87%) and critical (11.81%). Areas with a high propensity for desertification were found over the low to very low climatic quality and moderate to high soil quality including lower socio-economic quality. The lower socio-economic quality is mainly due to high to very high population density (>100 people/km2), low to moderate illiteracy rate (<16%), and low to moderate work participation rate (<50%) that incentivize unsustainable land use practices. The study provides a valuable tool for understanding and managing natural resources. It offers a detailed analysis of the environmental sensitivity of the study area, taking into account various factors like land use, vegetation cover, slope, and soil erosion potential. The developed comprehensive map of the area helps in identifying the most sensitive regions and developing appropriate conservation strategies. The information obtained from the study can be utilized to develop and implement successful measures to prevent or alleviate desertification, which is crucial for sustaining the health of ecosystems and the welfare of local residents.

Unearthing the legacy of wildfires: post fire pyrogenic carbon and soil carbon persistence across complex Pacific Northwest watersheds

AbstractWildfires have the potential to dramatically alter the carbon (C) storage potential, ecological function, and the fundamental mechanisms that control the C balance of Pacific Northwest (PNW) forested ecosystems. In this study, we explored how wildfire influences processes that control soil C stabilization and the consequent soil C persistence, and the role of previous fire history in determining soil C fire response dynamics. We collected mineral soils at four depth increments from burned (low, moderate, and high soil burn severity classes) and unburned areas and surveyed coarse woody debris (CWD) in sites within the footprint of the 2020 Holiday Farm Fire and in surrounding Willamette National Forest and the H.J. Andrews Experimental Forest. We found few changes in overall soil C pools as a function of fire severity; we instead found that unburned sites contained high levels of pyrogenic C (PyC) that were commensurate with PyC concentrations in the high severity burn sites—pointing to the high background rate of fire in these ecosystems. An analysis of historical fire events lends additional support, where increasing fire count is loosely correlated with increasing PyC concentration. An unexpected finding was that PyC concentration was lower in low soil burn severity sites than in control sites, which we attribute to fundamental ecological differences in regions that repeatedly burn at high severity compared with those that burn at low severity. Our CWD analysis showed that high mean fire return interval (decades between fire events) was strongly correlated with low annual CWD accumulation rate; whereas areas that burn frequently had a high annual CWD accumulation rate. Within the first year postfire, trends in soil density fractions demonstrated no significant response to fire for the mineral-associated organic matter pool but slight increases in the particulate pool with increasing soil burn severity—likely a function of increased charcoal additions. Overall, our results suggest that these PNW forest soils display complex responses to wildfire with feedbacks between CWD pools that provide varying fuel loads and a mosaic fire regime across the landscape. Microclimate and historic fire events are likely important determinants of soil C persistence in these systems.

Production of vegetables with biofertilizers based on native microorganisms: A case study in Tixtla, Guerrero, Mexico

In agriculture, the use of fertilizers has increased due to the high demand for food by humanity, causing negative impacts because of high production costs and soil contamination. We evaluated five biofertilizers based on native microorganisms promoters of plant growth (NMPPG) as an alternative to the fertilizers used by small vegetable producers. The evaluation was carried out with three types of vegetables (lettuce, celery and epazote) in the Juan Berbera Catalán Irrigation Unit made up by producers from the community of Tixtla, Guerrero. The results show that Rhizobium sp. R01 (Tx3), Azotobacter sp. C3 (Tx1) and Bacillus licheniformis M2-7 (Tx5) used as biofertilizers promote germination and considerably increase fresh weight in these crops, and Azospirillum sp. M9 (Tx2) and Trichoderma sp. ABC1 (Tx4) present significant differences with the negative and chemical control. The yield of lettuce, celery and epazote was favored using biofertilizers, which can be considered a good alternative to apply to these crops, likewise, the price of biofertilizers (5 liters per Tx) compared to the fertilizer DAP-18-46-00 (50 kg) used by the same producers is $1,200.00 vs. $2,000.00 MXN per hectare produced respectively. In conclusion, the biofertilizers used herein represent a feasible alternative for farmers without disregarding the need for technical specialists and producers to identify optimal conditions that support the sustained application and management of biofertilizers.

Effect of Soil Acidification on Temperature Sensitivity of Soil Respiration

Soil pH significantly impacts microbial activity and community assembly, which in turn determines the temperature sensitivity (Q10) of soil respiration. Due to the high soil acidification in China, it is necessary to understand how soil acidification impacts Q10. Here, the Q10 of soil respiration was examined in a long-term field experiment (1982–present) with different soil pH caused by fertilization management. In this experiment, we selected treatments with neutral pH: (1) no crops and fertilization (CK); (2) crops without fertilization (NF); low pH with (3) crops with chemical fertilization (NPK); and (4) crops with chemical fertilization combined with wheat straw incorporation (WS). Under natural soil temperature changes, we observed that soil acidification lowered the Q10 value of soil respiration. Considering only temperature changes, the Q10 of soil respiration was strongly associated with microbial community composition, alpha diversity, and soil ammonium nitrogen. Considering the interaction between soil pH and temperature, warming strengthened the negative effect of soil pH on the Q10 of soil respiration, and the pathway through which soil pH mediated Q10 included not only microbial community composition, alpha diversity, and biomass but also the soil’s available phosphorus. This work enhanced our insights into the relationships between Q10, temperature, and soil pH by identifying important microbial properties and key soil environmental factors.

Using Optimized Spectral Indices and Machine Learning Algorithms to Assess Soil Copper Concentration in Mining Areas

Soil copper (Cu) contamination in mining areas poses a serious threat to the surrounding environment and human health. Timely determination of Cu concentrations is crucial for the ecological protection of mining areas. Hyperspectral remote sensing technology, with its non-destructive monitoring advantages, is essential for monitoring soil Cu pollution and achieving sustainable agricultural development. Using the hyperspectral technique for assessing soil Cu concentration, four machine learning models (support vector regression (SVR), random forest (RF), partial least squares regression (PLSR), and artificial neural network (ANN)), combined with three types of input variables (the full-band, sensitive bands, and optimized spectral indices (Opt-TBIs)) were employed. The hyperspectral reflectance of 647 soil samples from an abandoned tailings mine in western Inner Mongolia, China was collected. The sensitive bands were extracted using the successive projections algorithms (SPA), and 12 Opt-TBIs were selected. Results showed that the regions with higher soil Cu concentration extracted by SPA and Opt-TBIs were concentrated in the red edge and near-infrared regions. Compared with the full spectrum and SPA-sensitive bands, models based on Opt-TBIs successfully predicted soil Cu concentrations. The Opt-TBIs-RF model provided higher accuracy in estimating soil Cu among the four models. Using only four Opt-TBIs as input variables, the model maintained a stable performance in estimating Cu concentrations in different mining areas (R2Val = 0.72, RPDVal = 1.90). In conclusion, Opt-TBIs as input variables demonstrate good predictive capabilities for soil Cu concentrations in the study area, providing a basis for the formulation of sustainable strategies for soil reclamation and environmental protection in Inner Mongolia.

Analytical and Experimental Evaluation of Two-Layered Unsaturated Sand Bearing Capacity

Pavement design methods based on principles of unsaturated soil mechanics take into account high soil shear strength due to matric suction resulting in more economical design especially in long roads. In this study, the bearing capacity of two-layer unsaturated sand was investigated using both analytical and experimental methods. At first, using the limit equilibrium method an analytical formula was proposed to determine the bearing capacity of two-layer unsaturated sand in which linear suction profile was considered in soil layers. It should be considered that the constant matric suction distribution assumed by the previous researchers doesn’t show the real profile of matric suction within the soil, sometimes resulting in miscalculated unsaturated bearing capacity. Also, the bearing capacity of two-layer unsaturated poorly graded sand was investigated experimentally in different suctions by a special unsaturated chamber apparatus (UCA) designed for this purpose. The results show more than double increase of unsaturated soil bearing capacity with Sr=25% compared to saturated soil. The formation of failure wedges in all experiments was investigated by image processing. An acceptable agreement was obtained between the theoretical and experimental bearing capacity results.

The Effect of Saltwater Stress on the Performance of Cherry Tomatoes

Rising sea levels and saltwater intrusion in aquifers pose significant challenges for South Florida agriculture, leading to increased groundwater salinity and potential crop losses. Utilizing salttolerant crop species presents a potential solution for saline soils and regions with active saltwater intrusion. However, the effects of soil salinization through groundwater alone remains less studied. This research investigates the impact of short-term, below-ground saltwater stress on the growth, survival, and overall health of commonly grown cherry tomatoes (Solanum lycopersicum). The objectives of the study are to: 1) determine the impact of saline groundwater on tomato plant health and 2) compare the nutrient content of soil and tomato plant tissue exposed to varying concentrations of saline water. Established cherry tomato plants were exposed to varying concentrations of NaCl solution, simulating saltwater intrusion into groundwater. Over 28 days, plant height, leaf chlorophyll levels, and disease occurrences were monitored. It was found that the NaCl treatments did not significantly affect cherry tomato performance under the parameters of height, chlorophyll levels, or leaf nutrition when compared to the control group. This study suggests that cherry tomatoes can tolerate short-term exposure to NaCl in groundwater. Further exploration of more intense salt stress conditions from groundwater could be beneficial for utilizing this crop in areas with saline soils or polluted groundwater. Identification of salt-tolerant cherry tomato varieties can provide alternative crop options for non-arable land affected by high soil salinity.

Soil CO2 flux maps as tools to reduce the risk on soil diffuse degassing areas

Carbon dioxide released permanently from soils in diffuse degassing areas may constitute a permanent hazard for the population. Several villages in the Azores archipelago (Portugal) are placed in areas with anomalous soil CO2 degassing and lethal indoor CO2 concentration (>10 vol%) has been already recorded in some buildings. The 2021-2022 dislodgements of population at Vulcano (Italy) and La Palma (Spain) volcanic islands due to high soil CO2 degassing highlight the importance of defining criteria to produce human CO2 exposure risk maps, which are useful to mitigate the risk and should constitute valuable tools for land-use planners. Risk is assessed in the current study by combining susceptibility, exposure, and vulnerability maps. The defined criteria were applied to two villages in Furnas Volcano (São Miguel Island, Azores), showing that 58% and 98% of the buildings, respectively, at Furnas and Ribeira Quente villages are at high risk of CO2 exposure.

Distinguishing direct N2O emissions from 15N-labeled manure compost, urea, and maize roots in a field study

Nitrous oxide (N2O) emissions from agricultural activities are a significant contributor to global anthropogenic N2O emissions. Sustainable agriculture practices, including using manure compost to replace nitrogen (N) fertilizers, can reduce chemical fertilizer use and minimize negative impacts on soil health and water quality. However, the direct contributions of manure compost to N2O emissions have not been fully studied. We conducted a field study to distinguish the direct contributions of manure compost, urea, and residual maize roots to N2O emissions in an integrated crop-livestock agricultural system in Shandong Province, China. Using the 15N-labeling technique, we found that the majority (93.3%) of cumulative N2O emissions originated from the soil and other unaccounted sources. Notably, manure compost contributed 1.3%, while current-year urea, residual urea with root exudates, and maize root accounted for 3.4%, 1.9%, and 0.03% of cumulative N2O, respectively. Our results also demonstrated that applying manure compost in combination with urea resulted in lower seed yield-scaled N2O emissions (0.046 g N2O-N kg−1 seed) compared to applying urea alone, even when the total N input was identical, suggesting the potential of manure compost in a more sustainable agriculture model. The low emission factor of manure compost (0.005%) compared to urea (0.019%) supports this potential, indicating the slow-release nature of manure may mitigate N2O while maintaining crop yield. Additionally, the overall low emissions may be attributed to the relatively high soil pH (8.17), which influences the denitrification product ratio, favoring the conversion of N2O to N2. Our study provides valuable insights into the factors contributing to N2O emissions in integrated crop-livestock farming systems, and highlights the importance of distinguishing multiple sources of N2O emissions to develop effective strategies for reducing emissions while promoting sustainable agriculture.

Hydroponic Screening at Early Seedling Stage Identified Sources of Salinity Tolerance in Wheat (Triticum aestivum L.) Crop

Wheat is a vital crop globally, essential for agriculture, economics, and food security. However, in arid and semi-arid conditions, wheat production faces significant challenges due to low water availability, uneven rainfall distribution, and high soil salinity. The germination and early seedling stages are particularly vulnerable to these stresses. Therefore, this study assessed 15 wheat genotypes for their tolerance to salinity stress during early growth stages, using a hydroponic system with four salt stress levels (0, 50, 100, and 150 mM NaCl). Significant differences were observed for genotype and salinity main effects and their interaction on all investigated traits, indicating considerable variability in the response to salt stress among the investigated wheat cultivars. High NaCl concentrations led to substantial reductions in measured parameters across genotypes, with some showing resilience while others exhibited heightened sensitivity. Stress tolerance indices, such as mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI) and yield index (YI), were identified as reliable indicators for selecting salt-tolerant wheat cultivars. Consequently, Sidi Okba (G11), Ziad (G12), Tamezghida (G13) and Zidane (G14) emerged as the most promising, displaying acceptable performance under both non-stress and salt-stress conditions. These genotypes could serve as valuable genetic resources for breeding programs aimed at enhancing wheat’s salinity tolerance, particularly in arid and semi-arid regions.

Susceptibility of Zucchini Cultivars to Powdery Mildew (Podosphaera xanthii) under High and Low Nitrogen Regimes

Powdery mildew, primarily caused by Podosphaera xanthii, threatens cucurbit crop yield and longevity. Fungicides and resistant cultivars cannot fully manage or prevent the disease. Previous work has shown that powdery mildew incidence and severity can increase under high soil nitrogen. This study was conducted in Kentucky to determine disease severity and yield using a split plot design with nitrogen fertility (high: 140 kg/ha, low: 84 kg/ha) and zucchini cultivar (Cash Machine, Cue Ball, Desert, Dunja, Eight Ball, Emerald Delight, Golden Glory, Mexicana, and Spineless Perfection) as the main plot and subplot factors, respectively. In year one, powdery mildew severity was significantly higher in high soil nitrogen and varied significantly among cultivars. Yield was significantly lower in high soil nitrogen. Significant differences in fruit count, but not fruit weight, were observed among the cultivars. In year two, nitrogen did not significantly affect disease severity, but fruit weight and count were significantly lower in the high soil nitrogen treatment. ‘Golden Glory’ had significantly higher powdery mildew severity while ‘Mexicana’ and ‘Eight Ball’ had significantly lower severity compared to all other cultivars. Spineless Perfection had the highest fruit weight and was significantly higher than all other cultivars except for Cue Ball and Eight Ball. ‘Golden Glory’ had the highest fruit count and was significantly higher than all others except for ‘Dunja’. Nitrogen did not consistently affect disease severity throughout the study. The effects of powdery mildew on yield should be explored further, as heavily diseased plants did not always have low yield.

Evaluation of reanalysis soil moisture products using cosmic ray neutron sensor observations across the globe

Abstract. Reanalysis soil moisture products are valuable for diverse applications, but their quality assessment is limited due to scale discrepancies when compared to traditional in situ point-scale measurements. The emergence of cosmic ray neutron sensors (CRNSs) with field-scale soil moisture estimates (∼ 250 m radius, up to 0.7 m deep) is more suitable for the product evaluation owing to their larger footprint. In this study, we perform a comprehensive evaluation of eight widely used reanalysis soil moisture products (ERA5-Land, CFSv2, MERRA2, JRA55, GLDAS-Noah, CRA40, GLEAM and SMAP L4 datasets) against 135 CRNS sites from the COSMOS-UK, COSMOS-Europe, COSMOS USA and CosmOz Australia networks. We evaluate the products using six metrics capturing different aspects of soil moisture dynamics. Results show that all reanalysis products generally exhibit good temporal correlation with the measurements, with the median temporal correlation coefficient (R) values spanning 0.69 to 0.79, though large deviations are found at sites with seasonally varying vegetation cover. Poor performance is observed across products for soil moisture anomalies time series, with R values varying from 0.46 to 0.66. The performance of reanalysis products differs greatly across regions, climate, land covers and topographic conditions. In general, all products tend to overestimate data in arid climates and underestimate data in humid regions as well as grassland. Most reanalysis products perform poorly in steep terrain. Relatively low temporal correlation and high bias are detected in some sites from the west of the UK, which might be associated with relatively low bulk density and high soil organic carbon. Overall, ERA5-Land, CRA40, CFSv2, SMAP L4 and GLEAM exhibit superior performance compared to MERRA2, GLDAS-Noah and JRA55. We recommend that ERA5-Land and CFSv2 could be used in humid climates, whereas SMAP L4 and CRA40 perform better in arid regions. SMAP L4 has good performance for cropland, while GLEAM is more effective in shrubland regions. Our findings also provide insights into directions for improvement of soil moisture products for product developers.

Joint Impacts of Meloidogyne incognita and Soil Nutrition on Solanum lycopersicum var. cerasiforme.

Strategies for plant nutrient resource allocation under Meloidogyne spp. infection and different soil nutrient conditions are not well established. In response, the objectives of this research are to determine if increased vegetative growth of Solanum lycopersicon var. cerasiforme (cherry tomato) under high nutrition enhances resistance to M. incognita and whether adaptive strategies for growth, reproduction, and nutrient uptake by cherry tomato infected with M. incognita alter nutrient availability. The study was conducted under greenhouse conditions using high, medium, and low soil nutrient regimes. The research results indicate that the total biomass of cherry tomato was less in the presence of M. incognita infection under all three nutrient conditions, compared with plants grown in the absence of this nematode. However, the increase in the root/shoot ratio indicates that cherry tomato allocated more resources to belowground organs. Under the combined impacts of M. incognita infection and low or medium soil nutrition, the nitrogen content in root system tissues and the phosphorus content in shoot system tissues were increased to meet the nutrient requirements of galled root tissue and plant fruit production. It is suggested that plants increase the allocation of reproductive resources to fruits by improving phosphorus transportation to the aboveground reproductive tissues under low and medium nutrient conditions. Overall, the study highlights a significant impact of soil nutrient levels on the growth and resource allocation associated with M. incognita-infected cherry tomato. In response, soil nutrient management is another practice for reducing the impacts of plant-parasitic nematodes on crop production.

A longitudinal analysis of soil salinity changes using remotely sensed imageries

Soil salinization threatens agricultural productivity, leading to desertification and land degradation. Given the challenges of conducting labor-intensive and expensive field studies and laboratory analyses on a large scale, recent efforts have focused on leveraging remote sensing techniques to study soil salinity. This study assesses the importance of soil salinity indices’ derived from remotely sensed imagery. Indices derived from Landsat 8 (L8) and Sentinel 2 (S2) imagery are used in Random Forest (RF), eXtreme Gradient Boosting (XGBoost), Decision Tree (DT), and Support Vector Machine (SVR) are associated with the electrical (EC) conductivity of 280 soil samples across 24,000 hectares in Northeast Iran. The results indicated that the DT is the best-performing method (RMSE = 12.25, MAE = 2.15, R2 = 0.85 using L8 data and RMSE = 10.9, MAE = 2.12, and R2 = 0.86 using S2 data). Also, the results showed that Multi-resolution Valley Bottom Flatness (MrVBF), moisture index, Topographic Wetness Index (TWI), and Topographic Position Indicator (TPI) are the most important salinity indices. Subsequently, a time series analysis indicated a reduction in salinity and sodium levels in regions with installed drainage networks, underscoring the effectiveness of the drainage system. These findings can assist decision-making about land use and conservation efforts, particularly in regions with high soil salinity.

The coupling of sulfide and Fe-Mn mineral promotes the migration of lead and zinc in the redox cycle of high pH floodplain soils

In this study, we investigated the impact of fluctuating water levels on the distribution of lead (Pb) and zinc (Zn) in soil and sediments at a historical Pb-Zn smelting site along the Xiangjiang River. Despite the high pH levels (7 to 11) in the study area, which generally inhibits heavy metal solubility, we found that regular changes in water levels still affect Pb-Zn movement. Soil analysis revealed distinct redox zones within the unconfined aquifer, as shown by the variable Fe/Mn and Ce/Ce* ratios. Advanced techniques such as Mn K-edge XAFS, Mössbauer spectroscopy, and TOF-SIMS indicated persistent Fe-Mn redox cycling and highlighted the presence of Pb and Zn-rich manganese oxides near sulfur-bearing minerals. These findings suggest that acidic microzones produced by the oxidation of sulfur-bearing minerals become "refuges" for microbial and heavy metal activity. Considering that sulfur-containing minerals are widespread waste types in nonferrous metal smelting sites, these findings are instructive for a better understanding of the transformation mechanisms of heavy metal ions in nonferrous metal smelting-polluted environments and for guiding pollution remediation strategies.

Evaluation of aluminum tolerance diversity in Avena sativa L. from the VIR collection

Background. Oat is an important food and feed cereal crop in Russia. The area under oats is 10 million ha worldwide, and 3 million ha in Russia. Acid soils with excessive content of exchangeable aluminum occupy almost every third hectare in the exUSSR territory. Oats are relatively resistant to unfavorable soil factors. Among cereal crops, oat is second only to rye and triticale in terms of resistance to exchangeable Al forms. Despite the crop’s high environmental plasticity, an important condition for obtaining sustainable oat yields is the development of new cultivars with resistance to adverse environmental factors, including metal toxicity and high soil acidity.The objective of this work was to search for oat cultivars resistant to soil stressors (excess of Н+ and Al3+) for use in breeding for edaphic resistance.Materials and methods. The research material included 687 oat accessions from the VIR global plant genetic resources collection. The accessions underwent laboratory evaluation of their aluminum tolerance at the initial growth and development stages using the method of measuring radicle growth after the exposure to aluminum stress. Reproducibility of the used modification of the method was mathematically proved.Results and discussion. Significant variation in the resistance to the studied stressor was observed among the accessions. The regions acting as sources of valuable aluminum resistance genes were identified for the crop. The accessions selected for their high resistance to exchangeable aluminum can be used in breeding programs to develop high-yielding oat cultivars with edaphic resistance.