Soil Systems

Environmental pollution by poly- and perfluoroalkyl substances (PFAS) can impact human health through drinking water and the ingestion of contaminated agri-food. Plants can take up PFAS from polluted soils or irrigation waters, and soil amended with biochar has been proposed as a practical and sustainable option to effectively reduce the PFAS transfer from soils to plants. We evaluated the potential of biochar, the byproduct of biomass pyrolysis, to reduce or prevent PFAS uptake from contaminated soil and water in a field trial conducted in a PFAS-contaminated area, where tomato and red chicory plants were grown in succession. The PFAS content in irrigation water, soil, and tomato and red chicory plants was determined by liquid chromatography coupled to mass spectrometry before and after each cultivation trial. Compared to those grown in unamended soil, tomato plants grown in the biochar-amended soil showed a significantly lower uptake of perfluorobutane sulfonic acid (PFBS), perfluoroheptanoic acid (PFHpA), and perfluorooctanoic acid (PFOA) in the leaves (−70%, −45%, and −84%, respectively), and significantly less (−61%) perfluorobutanoic acid (PFBA) in the fruits. Compared to unamended soils, leaves of red chicory plants grown in biochar-amended soil accumulated less PFBS (−74%) in the early growth stage and less PFBA (−34%) at plant maturity. The presented results confirmed previous reports on the potential soil amendment with biochar as a sustainable and effective measure for reducing PFAS uptake by horticultural crops cultivated in PFAS-polluted areas and PFAS concentration in their edible parts. Implications of this approach are also discussed. Full article

Soil health and fertility are essential components of sustainable land management. In Bhutan, where agricultural practices range from organic to conventional systems, and natural vegetation areas persist across varied elevations. Understanding how these factors influence soil properties is essential for advancing sustainable agriculture and fostering environmental stewardship. Thus, the objectives of this study were to evaluate some soil chemical properties across land use practices and their relationship to soil texture. Soil organic carbon (SOC) and macro-nutrients in three land use types (organic fields—OrgF; conventional fields—ConF; and natural vegetation—NatV) were studied across high-, mid-, and low-altitude sites in the Wangdue Phodrang, Chhukha, and Dagana districts of Bhutan. The effects of land use practices on soil properties varied with altitude. While available P responded significantly at both high- and mid-altitude locations (p < 0.01), SOC content was influenced only at high altitude (p < 0.001). In contrast, soil pH (p < 0.01) and available K (p < 0.001) showed clear sensitivity to land use at low altitude but were unaffected at higher elevations. Total N content and C:N ratios remained relatively stable across management practices within each altitude category. Silt and clay content had positive relationship with SOC (R² ≥ 0.13), whereas sand content had a significant negative relationship (R² = 0.23, p < 0.001). These findings are pertinent to providing guidelines for sustainable land management, improving agricultural practices, and shaping policies to protect and restore soil health across varied agro-ecological zones. Full article

Soil moisture plays a critical role in the global water cycle, the exchange of matter and energy within ecosystems, and the movement of water in plants. Accurate monitoring of soil moisture is essential for drought early warning systems, irrigation decision-making, and crop growth assessment. The use of drone-based multispectral remote sensing technology for estimating the soil moisture content offers advantages such as wide coverage, high accuracy, and efficiency. However, the soil background can often interfere with the accuracy of these estimations. In specific environments, such as areas with strong winds, removing soil background noise may not necessarily enhance the precision of estimates. This study utilizes unmanned aerial vehicle (UAV) multispectral imagery and employs a vegetation index threshold method to remove soil background noise. It systematically analyzes the response relationship between spectral reflectance, spectral indices, and the soil moisture content in the top 0–10 cm layer of alfalfa; constructs K-Nearest Neighbors (KNN), Random Forest Regression (RFR), ridge regression (RR), and XG-Boost inversion models; and comprehensively evaluates model performance. The results indicate the following: (1) The XG-Boost model validation set had the highest R² value (0.812) when spectral reflectance was used as the input variable, which was significantly better than the other models (R² = 0.465 to 0.770), and the RFR model validation set had the highest R² value when the spectral index was used as the input variable (0.632), which was significantly better than the other models (R² = 0.366 to 0.535). (2) After removing soil background noise, the accuracy of the soil moisture estimates for each model did not show significant changes; specifically, the R² value for the XG-Boost model decreased to 0.803 when using spectral reflectance as the input, and the R² value for the RFR model dropped to 0.628 when using spectral indices. (3) Before and after removing the soil background noise, the spectral reflectance can provide more accurate data support for the inversion of the soil moisture content than the spectral index, and the XG-Boost model is the most effective in the inversion of the soil moisture content when using the spectral reflectance as the input variable. The research findings provide both theoretical and technical support for the retrieval of the surface soil moisture content in alfalfa using drone-based multispectral remote sensing. Additionally, they offer evidence that validates large-scale soil moisture remote sensing monitoring. Full article

Monitoring the concentration of heavy metals in urban soils is of a paramount importance for several reasons. These inorganic pollutants can pose a significant health risk to living organisms, as they are toxic even at low concentrations and can be present in the soil for a long period of time. This study assesses the spatial distribution, concentration levels, and potential anthropogenic and natural sources of eight typical heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb and Zn) occurring in urban surface soils across Debrecen, Hungary. A total of 295 topsoil samples were collected; heavy metal concentrations were determined by energy-dispersive X-ray fluorescence (EDXRF) spectrometry. The results were interpreted using descriptive statistics, correlation analysis, hierarchical clustering, factor analysis, ordinary kriging interpolation, and spatial-discriminant analysis. The dual origin of the metal contaminants was revealed: As, Co, Pb, and Zn showed strong anthropogenic signatures associated with traffic, urban waste, and construction materials, whereas Cr and Ni were associated with natural geogenic sources. Cd reflected both lithogenic and point-source urban pollution. The current evaluation incorporated Hungarian and Dutch regulatory benchmarks to identify exceedances of environmental quality thresholds. It was found that only Cd and Cr exceeded the Hungarian target values, on average. Linear discriminant analysis based on pollution maps highlighted contamination hotspots around traffic corridors and newly industrialized zones. The importance of high-resolution soil monitoring in the rapidly urbanizing city is highlighted. Given its anticipated industrial and transportation developments, accumulations of heavy metals are probably going to be further exacerbated; therefore, the results provide a critical baseline for future environmental assessments and long-term monitoring. Full article

Olive groves (Olea europaea L.) are highly susceptible to soil degradation, particularly water erosion, due to sparse canopy cover and wide inter-row spacing. This study evaluated the effect of different vegetation cover management practices on soil quality and erosion control in a tropical olive grove in southeastern Brazil. The experiment followed a randomized block design with five treatments: exposed soil (BS), olive trees on exposed soil (OB), olive trees with spontaneous vegetation managed with herbicide (OVH), with mowing (OVM), and with mowing + localized weeding (OVMC). Physical, chemical, and biological indicators and losses due to water erosion were analyzed. The OVM and OVMC treatments promoted an increase in soil organic matter (up to 39 g kg⁻¹), microbial biomass carbon (40% higher than BS), enzymatic activity, and glomalin, improving aggregate stability (WMD of 4.9 mm) and reducing soil and water losses by more than 99% compared to exposed soil. The BS and OB treatments, on the other hand, showed higher acidity, lower microbial activity, and greater susceptibility to erosion. The study reinforces that maintaining vegetation cover improves soil quality, mitigates erosion, and promotes the sustainability of olive groves in tropical regions. Full article

The high-elevation ecosystems of the Tibetan Plateau provide crucial ecosystem services including watershed protection and water provision for downstream human and wildlife communities. Thus, understanding the relationship between soil properties and vegetation under different management regimes is important as a warming climate alters these systems. This study assessed vegetation cover, quantified the distribution of soil nutrients, and examined the relationships among soil chemical properties and plant cover in the high-elevation shrublands (3300 to 3700 m) in the Qilian Mountains on the northeastern Tibetan Plateau of China. These vegetation surveys and soil sample collections were conducted on 15 shrubland plots at different soil depths and soil chemical properties were investigated at each elevation. The content of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK) fluctuated along the elevational gradient, while soil pH was close to neutral (pH 7.4). At our sites, SOM and TN contents generally increased with elevation, and AK was positively correlated with Salix plant cover. Using PCA, we determined that PC1 captured 43% of the total variance, and SOM and TN were the top contributing features. As climate in the region warms and precipitation becomes more variable, understanding the current soil–vegetation equilibria and how vegetation may migrate in future years is important to predicting changes in this region, especially at high elevations. From a managerial perspective, our goal was to provide additional information for restoring and managing subalpine and alpine shrubland vegetation in the Qilian Mountains to ensure the future sustainable use of these systems. Full article

Fertilizer integration is key for sustainable tea gardens, but the impacts of different plant- or animal-derived organic fertilizers on soil pH, nutrients, and carbon composition remain unclear. This study evaluated five fertilizer treatments: 50% chemical fertilizer combined with 50% of either compound fertilizer (CF), rapeseed cake (RC), soybean cake (SC), chicken manure (CD), or sheep manure (SD). Results indicate that both plant- and animal-derived organic fertilizers effectively increased soil pH and soil organic matter content. However, animal-derived fertilizers showed a more pronounced capacity to buffer soil acidity, albeit with the potential risk of exceeding the optimal pH range for tea cultivation. In terms of soil fertility, RC performed best, achieving the highest total nitrogen and phosphorus contents. Compared to CF, RC increased nitrogen by 27.98% and phosphorus by 89.04% in the first year, and by 51.21% (N) and 61.35% (P) in the second year. The CD demonstrated superior performance in available potassium, with increases of 52.01% in the first year and 86.09% in the second year compared to CF. Regarding soil organic carbon composition, including total organic carbon (TOC), particulate organic carbon (POC), and mineral-associated organic carbon (MAOC), both types of organic fertilizers enhanced TOC levels compared to CF. Animal-derived fertilizers were more effective in rapidly increasing TOC and POC, whereas plant-derived fertilizers promoted a more stable accumulation of POC, contributing to long-term soil fertility through sustained nutrient release. Dynamics of MAOC revealed initial enhancements under animal-derived fertilizers, but stability declined over time. In contrast, plant-derived treatments showed a steadier increase in MAOC. Ratios of POC/TOC and MAOC/TOC further indicated that RC favored a higher proportion of particulate organic carbon, which is crucial for sustained nutrient availability. In conclusion, this study highlights the importance of tailored fertilization strategies to optimize soil productivity and enhance carbon sequestration in tea gardens. Adapting fertilizer application to specific soil conditions is therefore critical for the effective management of modern sustainable tea garden systems. Full article

Soil color has long been used as an indicator for soil properties such as soil organic carbon and soil moisture. Recent developments in citizen science have seen the increased use of smartphone cameras for soil color measurements. However, there are high errors associated with this technique. Two major sources of errors are smartphone cameras and lighting conditions. These errors limit the applicability of this technique in citizen science. Existing correction methods for reducing these errors are either ineffective or too complicated or difficult to apply. There is also a lack of systematic analysis on how these correction methods can reduce errors. In this study, we tested the effectiveness of using a color plate as a reference to reduce the errors on color measurements due to the use of different smartphones and taking photos under different lighting conditions. Three types of objects were tested, including the squares on the color plate itself, the color chips in a Munsell soil color book, and soil samples. The results show that the raw values of color parameters showed different patterns of biases with different smartphones and lighting conditions. The calibration reduced the errors consistently for all smartphones under all lighting conditions for the color plate squares. For the Munsell book chips or the soil samples, the calibration did not always reduce the bias but it did reduce the variations in all color parameters among smartphones and lighting conditions and, therefore, improved the precision of color measurements. Full article

Soil reflects ecosystem processes and is influenced by gradual biospheric changes, which can affect its biotic components. In fairy rings, soil morphology, physicochemical properties, and biota are interconnected within a shared environmental space. In La Bertolina grasslands, while fungal and bacterial genomics have been investigated, the micromorphological soil effects of these rings have not. This study micromorphologically analyzed thin sections of three fairy rings at four zones: the ring center, the zone of peak growth in 2013 (R13), the predicted growth zone for 2019 (R19), and outside the ring. From each zone, two thin soil sections were prepared, totaling 24 samples. Fungal structures were exhaustively described according to morphological criteria following reference by multiple authors. The soil was a calcareous, loamy Regosol, and showed moderately developed crumb or laminar microstructures. Nine types of fungal structures were identified, consistent with genomic findings in the zone. Although fungal abundance did not vary across zones, mesofauna droppings were more frequent in R13 and R19, which was related to higher nutrient or water availability due to the fungal activity. Regarding the groundmass of the topsoil, neither the composition nor the microstructure of the surface horizons varied according to the moment of appearance of the ring at the sampled points. Full article

Molybdenum (Mo) is an important trace nutrient element in the soil and plays a significant role in maintaining plant growth. However, there are scarce studies on soil Mo content change and its driving factors based on historical soil samples. This paper studied the characteristics of Mo content in three different parent rock types (PRTs) and different eras. The findings indicated that the available Mo (AMo) and total Mo (TMo) in the purple soil were 0.087–0.131 mg/kg and 0.488–0.903 mg/kg, respectively, which were considered deficient. The TMo of J₃p was higher than those of J₂s and K₂j, but the AMo was slightly lower than those of K₂j and J₂s. Compared with the old samples, the AMo of K₂j, J₂s and J₃p has increased by 35.58%, 120% and 30.86%, respectively, and their TMo has increased by 29.37%, 25.21% and 11.97%, respectively. Our studies showed that PRTs directly impacted AMo, and indirectly influenced TMo and AMo through soil pH and organic matter. Organic matter and pH positively affected TMo, while pH negatively affected AMo. Overall, soil molybdenum content in the study area was generally insufficient, and local governments should comprehensively consider the molybdenum content and its main constraints for scientific fertilisation. Full article

Oil sands mining in northeastern Alberta, Canada, has disturbed large areas of the northern boreal forest which must be restored to pre-disturbance levels through reclamation. The oil sands tailings have high pH and elevated levels of Na⁺ which are harmful to plants. A novel non-segregating tailing (NST) was developed to accelerate consolidation of fine tailings, yet its effects on boreal plant species are not well characterized. In oil sands reclamation, a capping layer—either forest mineral soil mix (FMM), salvaged from upland boreal forest sites, or peat mineral mix (PMM), sourced from peatlands—is typically applied over overburden materials and coarse tailings sands prior to revegetation. Plants in oil sands revegetation sites frequently experience nutrient deficiencies, such as nitrogen and phosphorus, and impaired physiological processes due to the high pH and soil salinity. In this study, we examined the effects of nitrogen and phosphorus supplements in the NST-amended reclamation soils on growth and physiological parameters of trembling aspen (Populus tremuloides) and white spruce (Picea glauca) seedlings. We found that the growth and physiological responses of seedlings were superior in the mixture of NST and FMM compared with NST and PMM. Phytotoxicity of NST was associated with elevated boron levels. Trembling aspen exhibited greater sensitivity to NST but showed stronger growth improvements with increased nitrogen and phosphorus supplementation compared to white spruce. High levels of nitrogen and phosphorus supplementation alleviated the adverse effects on both species that were caused by mineral nutrient imbalance. Full article

Efforts have been underway worldwide to reintroduce seawater to many historically diked salt marshes for restoration of tidal flow and associated estuarine habitat. Seawater restoration to a diked Cape Cod marsh was simulated using the computer program PHREEQC based on previously conducted microcosm experiments to better understand the associated timing and sequence of multiple biogeochemical reactions and their implications to aquatic health. Model simulations show that acidic, reducing waters with high concentrations of sorbed ferrous iron (Fe[II]), aluminum (Al), sulfide (S²⁻), ammonia (NH₄⁺ + NH₃), and phosphate (PO₄³⁻) are released through desorption and sediment weathering following salination that can disrupt aquatic habitat. Models were developed for one-dimensional reactive transport of solutes in diked, flooded (DF) marsh sediments and subaerially exposed, diked, drained (DD) sediments by curve matching porewater solute concentrations and adjusting the sedimentary organic matter (SOM) degradation rates based on the timing and magnitude of Fe(II) and S²⁻ concentrations. Simulated salination of the DD sediments, in particular, showed a large release of Al, Fe(II), NH₄⁺, and PO₄³⁻; the redox shift to reductive dissolution provided higher rates of SOM oxidation. The sediment type, iron source, and seasonal timing associated with seawater restoration can affect the chemical speciation and toxicity of constituents to aquatic habitat. The constituents of concern and their associated complex biogeochemical reactions simulated in this study are directly relevant to the increasingly common coastal marsh salination, either through tidal restoration or rising sea level. Full article

This study investigated the impacts of land-use history and an episodic flood event on the soil quality of a riverine floodplain ecosystem, providing long-term and short-term disturbance perspectives. The study took place in the Saint Michael’s College Natural Area, which has over a hundred-year history of land-use change. Based on aerial orthoimagery, three zones (a recently abandoned farm field, a new-growth forest, and an old-growth forest) were selected that reflected different land-use histories. Two plots were selected per zone and pooled soil samples were collected from each before and after a major flooding event. Surface soil quality before flooding was often similar among the new- and old-growth forested areas (1.4 mg-P/g-soil, 6.8% soil organic matter (SOM), 0.79 humification index (HIX), and 13% Peak T) but differed from that found in the recently abandoned farm field, which had higher phosphorus levels (1.6 mg-P/g-soil), lower SOM content (3.9%), more microbial-like SOM (0.65 HIX and 17% Peak T), and drier soils. Flooding caused SOM to better resemble that of a forest rather than an agricultural field, and it lowered phosphorus levels. The results of our study suggest that episodic flooding events could help accelerate the restoration of soil organic matter conditions. Full article

Arbuscular mycorrhizal fungi (AMF) taxa, glomalin protein, and hyphal density are potential indicators of soil functionality of temperate grasslands in marginal environments subject to grazing over the years. This study evaluated how the AMF community composition, glomalin protein, and hyphal density vary in response to grazing intensity (low or high) and seasonality (spring and autumn) in sodic soils of Argentinian temperate grasslands. The AMF community was dominated by Glomeraceae species. Funneliformis geosporus and Glomus brohultii were the most abundant in both seasons and all grasslands. No AMF species were associated with a particular grazing intensity. However, Entrophospora etunicata, Glomus fuegianum, Septoglomus constrictum, and Acaulospora sp. occurred only in spring, and no species were exclusive to autumn. Hyphal density was highest in grasslands with low grazing intensity and can be considered an indicator of soil functionality. Glomalin protein was the highest in spring in all grasslands. The lower grazing intensity in grasslands with poor livestock control showed no changes in AMF diversity. The AMF community showed high adaptation to soil conditions, indicating high resilience. We concluded that longer periods of controlled grazing management are needed to improve soil conditions and, consequently, change the AMF species composition. Full article

Land use conversion to perennial cropland often degrades the soil structure and fertility, particularly under Mediterranean climatic conditions. This study assessed spatial and temporal dynamics of soil properties and tree responses to 3-year repeated mature compost additions in a citrus orchard. Digital soil mapping revealed strong baseline heterogeneity in texture, CEC, and Si pools. Compost application markedly increased total organic C and N levels, aggregate stability, and pH with noticeable changes after the first amendment, whereas a limited C storage potential was found following further additions. NDVI values of tree canopies monitored over a 3-year period showed significant time-dependent changes not correlated with the soil fertility variables, thus suggesting that multiple interrelated factors affect plant responses. The non-crystalline amorphous Si/total amorphous Si (_iSi:Si_amor) ratio is here proposed as a novel indicator of pedogenic alteration in disturbed agroecosystems. These findings highlight the importance of tailoring organic farming strategies to site-specific conditions and reinforce the value to combine C and Si pool analysis for long-term soil fertility assessment. Full article

In the present work, six biochars were produced from the pyrolysis of poultry manure at 400 °C and 600 °C (PM-B-400 and PM-B-600), and their post-modification with, respectively, iron chloride (PM-B-400-Fe and PM-B-600-Fe) and potassium permanganate (PM-B-400-Mn and PM-B-600-Mn). First, these biochars were deeply characterized through the assessment of their particle size distribution, pH, electrical conductivity, pH at point-zero charge, mineral composition, morphological structure, and surface functionality and crystallinity, and then valorized as biofertilizer to grow spring barley at pot-scale for 40 days. Characterization results showed that Fe- and Mn-based nanoparticles were successfully loaded onto the surface of the post-modified biochars, which significantly enhanced their structural and surface chemical properties. Moreover, compared to the control treatment, both raw and post-modified biochars significantly improved the growth parameters of spring barley plants (shoot and root length, biomass weight, and nutrient content). The highest biomass production was obtained for the treatment with PM-B-400-Fe, owing to its enhanced physico-chemical properties and its higher ability in releasing nutrients and immobilizing heavy metals. These results highlight the potential use of Fe-modified poultry manure-derived biochar produced at low temperatures as a sustainable biofertilizer for soil enhancement and crop yield improvement, while addressing manure management issues. Full article

Desert plant communities play a vital role in sustaining the stability of arid ecosystems; however, they demonstrate limited resilience to environmental changes. A critical aspect of understanding community assembly mechanisms is determining whether soil texture heterogeneity affects vegetation diversity in arid deserts, especially under conditions of extreme water scarcity and restricted nutrient availability. This study systematically examined the relationships between plant diversity and soil physicochemical properties across four soil texture types—sand, sandy loam, loamy sand, and silty loam—by selecting four representative desert systems in the Hami region of Xinjiang, China. The objective was to elucidate the mechanisms through which soil texture may impact desert plant species diversity. The findings revealed that silty loam exhibited distinct characteristics in comparison to the other three sandy soil types. Despite its higher nutrient content, silty loam demonstrated the lowest vegetation diversity. The Shannon–Wiener index (H′), Simpson dominance index (C), Margalef richness index (D), and Pielou evenness index (Jsw) for silty loam were all lower compared to those for sand, sandy loam, and loamy sand. However, silty loam exhibited higher values in electrical conductivity (EC), urease activity (SUR), and nutrient content, including soil organic matter (SOM), ammonium nitrogen (NH⁴⁺-N), and available potassium (AK), than the other three soil textures. This study underscores the significant regulatory influence of soil texture on plant diversity in arid environments, offering new insights and practical foundations for the conservation and management of desert ecosystems. Full article

Combining potassium-containing rocks with conventional KCl may improve the agronomic use of K rock and reduce leaching from high-soluble sources. The aim of this study was to evaluate K rocks (phonolite and alkaline) and the mixture with KCl at different K rates on the biomass production of maize and rice (residual effect), K uptake, and K leaching. The experiment was conducted in greenhouse columns with sandy soil. The experimental design included four K sources: PR (phonolite rock), PR + KCl in an 86:14 mass ratio, AR (alkaline rock), and KCl; three K rates (100, 200, and 400 mg kg⁻¹); and a control (no K), with five replicates. PR + KCl resulted in similar maize biomass (120 g column⁻¹) and K uptake (18 mg g⁻¹) compared to KCl, and it was higher than the PR, the AR, and the control, which produced 86, 48, and 32 g column⁻¹, respectively. The residual effect of PR, PR + KCl, and KCl generated similar rice biomass. K leaching reached 15% of K applied with KCl and was reduced by 50% with K rocks. Thus, the mixture of PR + KCl can improve K fertilization compared to KCl, enhancing maize and rice biomass while reducing K leaching. Full article

This study aims to assess the ecological and human health risks associated with four heavy metals (Cd, Cr, Cu, and Zn) in the soil of a dumpsite in Targuist city, Morocco. In total, 16 surface soil samples were collected from the dumpsite and its nearby areas following leaching drain flows. The pollution load index (PLI), geo-accumulation index (Igeo), and potential ecological risk index (RI) were subsequently determined. In addition, hazard quotient (HQ) and health index (HI) were used to assess the non-carcinogenic and carcinogenic risks associated with the soil heavy metal contents. The PLI indicated significant contamination by the studied heavy metals. On the other hand, the Igeo values suggested no Cr contamination, moderate contamination by Cu and Zn, and severe contamination by Cd. The RI indicated a dominant contribution from Cd, with minor contributions from Cu, Zn, and Cr accounting for 92.47, 5.44, 1.11, and 0.96%, respectively, to the potential ecological risk in the study area. The non-carcinogenic health risks associated with exposure of the nearby population to the soil heavy metals at the dumpsite and burned solid waste-derived air pollution were below the threshold value of 1 for both children and adults. Although carcinogenic risks were observed in the study area, they were acceptable for both children and adults according to the United States Environmental Protection Agency (USEPA). However, carcinogenic risks associated with Cr were unacceptable according to the Italian Legislation. Finally, strategies to mitigate the risks posed by the dumpsite were also discussed in this study. Full article