Soil Systems doi: 10.3390/soilsystems10080093

Authors: Sebastiano Ettore Spoto

Soil-gas observations can retain a source-related response while remaining ambiguous with respect to source amplitude, source depth, transport state, water state, and measurement support. This study develops a reduced one-dimensional source–transport–observation analysis for gas-continuous unsaturated soils. Integral-normalized source kernels, a finite-volume solver, a raw scaled-coordinate Jacobian, common-threshold nuisance projection, and an auxiliary noise-scaled check are combined in a reproducible workflow. At a display tolerance of 0.05, the primary structural convention normalizes parameter columns over the complete 11-row observation universe before extracting observation subsets. Under this convention, a carbon dioxide (CO2) surface-flux observation retains one projected amplitude direction; within-set normalization reduces that restricted result to zero. The CO2 profile, ideal-state-constraint set, and full diagnostic set retain ranks of 1/2, 2/3, and 3/4, respectively, under both conventions. The noise-scaled calculation places one projected source response at or above the illustrative one-standard-deviation threshold within a numerical tolerance of 1 × 10−10. A published-data worked example shows why water and carbonate context are required before a gas-phase CO2 deficit is interpreted as a source decrease. The result is a pre-field screening method, not a site-calibrated inversion.

Soil Systems doi: 10.3390/soilsystems10080092

Authors: Dariya Privizentseva Ekaterina Kravchenko Kamil Kazeev Tatiana Minkina Margarita Getman Zengwei Yuan Valeria Bryleva Oğuz Can Turgay

The growing need for biomass waste recycling has led to increased interest in hydrothermal carbonization, which produces hydrochar as a by-product. This carbonaceous material can be applied in agriculture; however, its role in soil health is still not fully understood. Data on the effects of hydrochar on enzymatic activity, one of the key indicators of biological soil health, remain limited and contradictory. This study demonstrates the effects of hydrochars derived from alder wood chips, produced at three temperatures (180, 200, and 220 °C) and residence times (30, 60, and 90 min), on soil enzyme activity and the early seedling response of winter wheat (Triticum aestivum). Dehydrogenase and urease activities increased by 29–45% and 70–169% (p < 0.05), respectively, in hydrochar-amended soil compared with control soil. Hydrochars had no effect on catalase activity and, conversely, negatively affected invertase activity, reducing it by 19–47% relative to the control. Phosphatase activity showed an ambiguous response. It was found that hydrochars H180_90, H200_90, and H220_90 increased the geometric mean of enzyme activities by 17%, 22%, and 18%, respectively, which apparently indicates the advantages of these production conditions in terms of achieving the most positive effects on enzymatic activity. These findings highlight the importance of hydrothermal carbonization conditions in determining the enzyme-specific effects of hydrochar on soil biochemical functioning.

Soil Systems doi: 10.3390/soilsystems10080091

Authors: Michaella Petkova Gergana Dimitrova Evan Gatev Mariana Hristova Nikolai Dinev Galina Radeva

Heavy metal/loid (HM) pollution of soils, primarily as a consequence of mining and ore-processing activities, poses significant risks to ecosystems and human health. Soil microbial communities play essential roles in maintaining key ecosystem functions, including nutrient cycling, carbon sequestration, and soil stability. The purpose of this study was to characterize the taxonomic composition and diversity of bacterial communities and evaluate their functional adaptation to heavy metal stress in soils affected by long-term gold–copper mining activities in Bulgaria. Ten soil samples representing a Cu pollution gradient (53–860 mg kg−1) were categorized into five pollution classes. High-throughput sequencing of 16S rRNA gene amplicons revealed the dominance of the phyla Pseudomonadota (mean relative abundance 32%), Acidobacteriota (22%), and Actinomycetota (16%). At the class level, Alphaproteobacteria (18%), Terriglobia (16%), and Gammaproteobacteria (14%) were the most abundant taxa, indicating their adaptation to long-term heavy metal contamination. The genus Z2-YC6860 exhibited significant tolerance to Cu, whereas Bradyrhizobium_503372 was negatively associated with As and Zn concentrations. Functional predictions suggested enrichment of key pathways related to heavy metal resistance, including efflux systems and detoxification. The study design spans a broad Cu pollution gradient across river-associated and industrially impacted sites, providing an ecologically relevant framework for evaluating microbial responses to long-term metal stress.

Soil Systems doi: 10.3390/soilsystems10080090

Authors: Pamela F. Mejía-Leyva Carlos Raúl Morales-Nieto Jesús A. Prieto-Amparan Mansonia Pulido-Moncada Martín Martínez-Salvador Griselda Vázquez-Quintero Guadalupe N. Aguilar-Palma Alfredo Pinedo-Alvarez

This study addresses the need for reliable field-based tools to assess soil structural quality in semi-arid rangelands, where existing visual methods such as the Visual Evaluation of Soil Structure (VESS) and its modified version for grasslands (GrassVESS) may be limited by site conditions. The objective was to develop and evaluate a modified visual soil structure assessment method (RangelandVESS) adapted to livestock grazed rangelands in northern Mexico. Soil sampling was conducted in grazed and exclusion zones and soil structure was assessed using VESS, GrassVESS, and RangelandVESS. Thereafter, the scores of each method were compared with soil health indicators and above-ground biomass. Results showed distinctions in soil structural conditions between exclusion and overgrazed areas. RangelandVESS seems to demonstrate greater sensitivity to degradation, particularly in sandy soils, where it identified poorer structural quality compared to the other methods. Significant correlations were obtained between RangelandVESS scores and bulk density, infiltration, and biomass supporting its robustness. In contrast, no significant differences among methods scores were observed in clayey–loamy soils. However, RangelandVESS may provide a more reliable assessment of degradation. Overall, the findings suggest that RangelandVESS is a suitable tool for assessing soil structure in semi-arid rangelands and offers improved capacity to detect grazing induced degradation.

Soil Systems doi: 10.3390/soilsystems10080089

Authors: Zsolt Zoltán Fehér Tamás Magyar Florence Alexandra Tóth Péter Tamás Nagy

Heavy metal contamination in urban topsoil is one of the most serious environmental threats to children’s health, particularly through ingestion, dermal contact, and inhalation exposure routes. The objectives of this study were: (1) to assess the probabilistic exceedance-based priority of eight heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) with respect to regulatory threshold exceedance in Debrecen, Hungary; (2) to map the spatial distribution of exceedance probabilities using sequential indicator simulation (SISIM) with 100 equiprobable realizations per element (1000 for Cr) on a 50 m grid; and (3) to develop a toxicologically weighted composite exceedance index based on the Hungarian regulatory action thresholds and classify the results into priority categories. For Cd, the exceedance probability exceeded p > 0.50 in approximately 98% of the study area, and for Cr, in approximately 82% of the study area (regenerated at N = 1000; the Cr threshold lies near the sample median, so the p > 0.50 area is ensemble-size sensitive and was under-converged at N = 100). Approximately 86% of the study area fell into the Very Low Priority class, approximately 14% into the Low Priority class, and less than 0.1% of the area exceeded the Moderate Priority threshold. Monte Carlo perturbation of the child exposure relevance factors confirmed strong spatial rank stability of H(x) (median Spearman ρ= 0.989), indicating that the priority pattern is robust even though areas close to the Very Low Priority/Low Priority boundary may change class. This paper contributes single-threshold exceedance-probability maps at regulatory limits and a toxicity-weighted exceedance-priority index H(x)—a methodological and interpretive advance over our previous concentration mapping, using the same measurements with no new sampling. By constructing the composite index is toxicity-weighted: arsenic and cadmium carry ≈88% of the child weight, so H(x) chiefly resolves As- and Cd-driven priority, with the remaining metals refining local class boundaries. Receptor prioritization is a screening output to guide confirmatory sampling, not a definitive risk classification.

Soil Systems doi: 10.3390/soilsystems10080088

Authors: Isadora Varela Felipe Ogliari Bandeira Carolina Riviera Duarte Maluche Baretta Paulo Roger Lopes Alves Ícaro Luiz Golin Rodrigo Pizzani Dilmar Baretta

Fenthion is a veterinary pharmaceutical (VP) used in the control of ecto- and endoparasites in livestock. This active substance may reach the soil through the animals’ urine and feces, but the ecotoxicological data of this compound on non-target soil fauna is limited. This study aimed to evaluate the chronic ecotoxicity of a fenthion-based veterinary formulation on six species of soil invertebrates. Ecotoxicological tests were performed in a natural tropical soil (Entisol) with earthworms Eisenia andrei, enchytraeids Enchytraeus crypticus and Enchytraeus bigeminus and collembolans Folsomia candida, Sinella curviseta and Proisotoma minuta, following ISO protocols. The species sensitivity distribution (SSD) approach was employed to establish protective concentrations (PCs) for fenthion in soil. Collembolans were the most sensitive organisms; the EC50 for F. candida, S. curviseta and P. minuta were 0.72, 0.93 and 0.48 mg kg−1, respectively. Earthworms E. andrei presented intermediate sensitivity (EC50 = 28.40 mg kg−1). Enchytraeids were the least sensitive animals (EC50 for E. crypticus and E. bigeminus of 233.66 and 221.47 mg kg−1, respectively). SSD-derived PCs for 95%, 90%, 80% and 50% of soil species were estimated in 0.017, 0.054, 0.225 and 3.432 mg kg−1, respectively. The predicted environmental concentration (PEC) of fenthion in soil via veterinary use (0.032 mg kg−1) is almost twice the PC95 value (0.017 mg kg−1), indicating potential ecological risk of fenthion to soil species. This study brings new information regarding the ecotoxicological profile and ecological risk of a relevant VP to the edaphic community.

Soil Systems doi: 10.3390/soilsystems10080087

Authors: Yonggang Li Yingjie Gao Dongxiu Duan Xiuwen Shen Xiaoyu Tang Mengnan Yi Bingqian Su Zhao Fang Wenlong Xu Wenwen Huang Hao Yu

Biological soil crusts (BSCs) are important components of dryland ecosystems, yet nutrient patterns in adjacent uncovered soils remain unclear. We surveyed 70 sites across the Gurbantunggut Desert and collected 209 composite samples from the adjacent 0–5 cm surface-soil layer, categorized into three groups: uncrusted bare sand (n = 32), soil adjacent to algal–lichen crusts (n = 48), and soil adjacent to moss crusts (n = 129), with bare sand serving as the uncrusted reference category. The results showed that: (1) total nitrogen differed among the three BSC-associated soil categories (p = 0.041), whereas soil organic carbon, total phosphorus, and total potassium did not (all p > 0.05); (2) NO3−-N, NH4+-N, extractable inorganic N, NaHCO3-extractable phosphorus, and NH4OAc-extractable potassium differed significantly among categories (all p < 0.001) and were generally highest in soil adjacent to moss crusts; and (3) random forest models explained approximately 38–65% of nutrient variation and identified EC, total nitrogen, and the site-level BSC metric as the leading predictors. The final piecewise structural equation model explained 35.3–76% of nutrient variation. These findings indicate marked regional heterogeneity in extractable nutrient fractions associated with different BSC types.

Soil Systems doi: 10.3390/soilsystems10080086

Authors: Chukwudi E. Nwoko David M. Singer Allyson C. Tessin Jamie Brozell Bryce Stoltz Paul Corty

Lead (Pb)-based paints and other metal-bearing phases sourced from home exteriors can be added to adjacent soils, which break down over time, altering potential bioaccessibility. However, data on how particle size and morphology influence metal bioaccessibility remains limited, which was investigated in this study by using a simulated gastric acid (GA) extraction and characterization at the sub-grain scale. Soil samples were collected along horizontal transects at ~1 m intervals from three homes within the Akron metropolis, OH (USA). Each home had Pb-based paint on its exterior before recent renovations (2, 11, and 25 years ago, respectively). Soils were fractionated into sand, silt, and clay–fine silt using sieving, sedimentation, and laser scattering techniques, and analyzed by ICP-OES, XRD, and SEM-EDS. Lead content peaked within 0–2 m from the homes and declined with distance (maxima: 14,583 mg/kg, 8503 mg/kg, 2393 mg/kg at Sites 1–3, respectively), and primarily in the clay-fine silt fraction. Physical speciation of Pb at each site was invariant across the transect, but the percent Pb in the clay–fine silt Pb increased from Site 1 to Site 2, then declined at Site 3, suggesting the loss of fine particles at Site 3. Across sites 1 to 3, the paint chip abundance and size decreased, and secondary Pb-bearing phases appeared as discrete grains and secondary coatings. A similar trend is exhibited by Cu, Cd, and Zn, over time and space. These results highlight the ongoing breakdown of paint and re-sequestration of metals, which may elevate exposure risk from fine particles after housing renovations.

Soil Systems doi: 10.3390/soilsystems10080085

Authors: Jennifer L. Stackhouse Amalia Kokkinaki Danielle Cucchiara Gregory Möller

Elemental mercury has been used in the production of bleach since at least 1892 and continues to be utilized in some manufacturing processes today. This case study examines a former bleach manufacturing facility in the western United States, where elemental mercury was utilized as an electrical conductor in the chlor-alkali process to produce chlorine and sodium hydroxide, essential constituents in bleach formulation. The operational practices implemented at the facility led to the discharge of elemental mercury into both soil and groundwater. Subsequent investigations identified the presence of mercury in indoor air at levels surpassing the screening thresholds established by the California Environmental Protection Agency (CalEPA) Department of Toxic Substances Control (DTSC) and the United States Environmental Protection Agency (USEPA) for commercial exposure scenarios. Additionally, these concentrations exceeded the California Office of Environmental Health Hazard Assessment (OEHHA) acute 1 h reference exposure level (REL). The origins of mercury in indoor air have been identified as vapor intrusion associated with subsurface sources, along with a potential secondary indoor air source associated with mercury deposition and adsorption in building materials through the years. In the context of interim vapor intrusion mitigation, air purifiers and fans were deployed to enhance air exchange rates, while a comprehensive assessment led to the identification and sealing of 52 preferential pathways. Even with these interim vapor intrusion mitigation systems in place, elevated concentrations of elemental mercury are still present in the building and may represent the presence of a secondary indoor air source from accumulation of elemental mercury in building materials.

Soil Systems doi: 10.3390/soilsystems10070084

Authors: Aimé J. Messiga Neem Lal Pandey Busayo Kodaolu Shibli Md Abedin Sylvia Nyamaizi Thidarat Rupngam

This study aimed to disentangle the relative influence of inherent soil properties and annual starter P fertilization on active carbon (C) pools and C-, nitrogen (N)-, and phosphorus (P)-cycling enzyme activities in silage corn production systems with high-legacy P. Six fields with Mehlich-3 P ranging from 53.5 to 332 mg kg−1 were investigated in 2020 and 2021 in the Fraser Valley, Canada. The experiments at each site consisted of five starter P rates (0, 5, 10, 15, and 20 kg P ha−1 as triple super phosphate) arranged in a randomized complete block design with four replicates. Soil samples were collected at the V3 and V6 stages of silage corn and analyzed for active C, soil enzyme activities, and chemical properties. N-acetyl-β-glucosaminidase varied significantly across the six sites, suggesting substantial differences in the rate of C and N cycling. For instance, in 2020, N-acetyl-β-glucosaminidase was similar at Sites 1 and 2 at V6 and was approximately three times (514.51 pmol MUF g−1 soil h−1) higher than at Site 3 (170.29 pmol MUF g−1 soil h−1). Similarly, in 2021, a 2.8-fold higher MBC observed at Site 4 at V6, compared with the averages of Sites 5 and 6, further confirms an active C pool. Meanwhile, sites with the lowest MBC concentrations were linked to acidic soils (pH 5.3), and a negative correlation between inherent site–year characteristics and enzyme activities confirm enzymes repression. Acid phosphatase at Site 4 was 3-fold higher than at Site 5 and Site 6, while alkaline phosphatase was detected only at Site 4. We conclude that long-term soil conditions are the main factors influencing biological functionality, thereby overshadowing transient fertilization. This indicates that Fraser Valley farmers can prioritize long-term soil health management and safely reduce starter P applications in these high-legacy systems.

Soil Systems doi: 10.3390/soilsystems10070083

Authors: Egondu C. Umeobi Thomas F. Ducey Nicholas T. Basta James A. Ippolito

Understanding Cd and Pb in vitro bioaccessibility (IVBA) is important for evaluating human health risks in mine-impacted soils. In this field study, we assessed Cd and Pb bioaccessibility in a heavy metal contaminated mine impacted soil that received Low and High Compost applications (180 and 360 Mg ha−1, respectively), and Native Prairie soils within close proximity to the impacted soil, using three in vitro methods (Unites States Environmental Protection Agency (US EPA) pH 1.5, US EPA pH 2.5, and Ohio State University pH 1.8). Total Cd concentrations under High Compost (10.3 mg kg−1) exceeded the US EPA regional screening level (RSL)–residential soil Cd concentration for ingestion non-cancer risk in children (7.8 mg kg−1), while Low Compost and Native Prairie soils were below the RSL. Total Pb (<75 mg kg−1) in all sites was below the US EPA RSL for Pb for non-cancer risk in children (200 mg kg−1). Within each extraction method, Cd IVBA remained consistently high (>70% of total) across all three sites for at least US EPA pH 1.5 and OSU pH 1.8. In contrast, Pb IVBA varied across methods, with the pH 2.5 extraction consistently yielding lower Pb IVBA as compared to the other IVBA methods. These findings suggest that Cd poses a challenge for risk mitigation at this site, while Pb shows more promising stabilization outcomes. Findings highlight the importance of tailoring amendment strategies and selecting appropriate in vitro assays when assessing remediation effectiveness and risk within multi-metal contaminated mine-impacted sites, while emphasizing the need for long-term field validation of metal stability under real-world conditions.

Soil Systems doi: 10.3390/soilsystems10070082

Authors: Carmen Orts Ángel Marqués-Mateu Cristina Lull Josep V. Llinares Desamparados Soriano Rafael Boluda

Green undersown crops (GUCs) are increasingly promoted as a sustainable management strategy to improve soil quality and ecosystem services in Mediterranean orchards, particularly in the calcareous, low-organic-matter soils typical of Eastern Spain. In this context, soil quality is understood as the soil’s overall functional capacity, integrating physical structure, chemical balance, and biological activity, whereas soil fertility refers specifically to the soil’s ability to supply nutrients to plants; soil quality therefore encompasses a broader set of ecosystem functions beyond nutrient provision. However, their effects on the calcareous, low-organic-matter soils typical of Eastern Spain remain insufficiently quantified. This study evaluates the effects of seeded undersown (grasses, legumes, and flower mixtures), spontaneous vegetation, and herbicide-managed bare soil on topsoil (0–15 cm) physicochemical and biological indicators in 54 plots across three irrigated persimmon orchard sites (Granja, Cargol, and Alginet) over 18 months of treatment in the València region (Eastern Spain). Seasonal sampling was conducted at the START (early winter) and END (late spring) of the experiment period. Soil measurements at both sampling times included soil organic matter (SOM), nitrogen (N), C/N ratio, pH, electrical conductivity (EC), soil respiration rate (RR), collembolan abundance, mite abundance, and the QBS-ar index of soil arthropods. Legumes increased SOM by +1.12%, grasses by +0.22%, whereas flower mixtures (−0.44%) and spontaneous vegetation (−1.36%) showed SOM reductions associated with rapid biomass turnover. RR increased under all GUCs (+0.06 to +0.16 g CO2 m−2 h−1), and QBS-ar improved markedly under grasses (+26.6) and spontaneous vegetation (+36.7). EC decreased across all treatments (−16 to −84 µS cm−1). These results were analysed using principal component analysis (PCA). Four PCA components explained 74% of the total variance, revealing functional gradients driven by SOM, N, EC, RR and mesofauna. After 18 months, microbial biomass carbon (MBC) increased by +45–60% under legumes, water-soluble organic carbon (WSOC) by +30–50% under legumes and flower mixtures, and the enzyme activities (EA) by +20–40% under all GUCs. Herbicide-managed soils showed reduced biological activity and detectable residues of glyphosate and oxyfluorfen. PCA and linear discriminant analysis (LDA) were used to identify functional gradients and treatment separation. GUCs significantly increased SOM, MBC, EA, and mesofauna abundance compared with herbicide treatments, which showed reduced biological activity and detectable residues of glyphosate and oxyfluorfen. Legumes and flower mixtures produced the strongest improvements in biological functioning due to higher MBC, WSOC, EA and RR. PCA and LDA confirmed clear separation between GUCs and herbicide-managed soils based on multivariate differences in SOM, N, EC, RR, MBC, WSOC and mesofauna indicators. Overall, GUCs modulated soil chemistry and biodiversity and enhanced soil functioning and biological quality, supporting their adoption as a sustainable management strategy in Mediterranean orchards. Legume-based covers are recommended for rapid biological activation, whereas grass-based covers favour longer-term SOM stabilisation. These findings highlight their role as key tools for improving soil resilience in Mediterranean persimmon orchards.

Soil Systems doi: 10.3390/soilsystems10070081

Authors: Anna Temraleeva Nadezhda Arefieva Yury Bukin Svetlana Didovich Maxim Kulikovskiy

Background: The urgent need for sustainable agricultural drives the search for effective microbial biostimulants. Cyanobacteria of the order Nostocales are promising candidates due to their nitrogen-fixing capabilities and bioactive secondary metabolites. However, the genomic potential of many soil strains from microorganism collection remains largely unexplored. Methods: We performed a targeted genomic screening of five cyanobacterial strains from the All-Russian Collection of Microorganisms (VKM): Nostoc commune VKM Al-35, Nostoc punctiforme VKM Al-37, Nostoc minutum VKM Al-168, Anabaena pirinica VKM Al-153, and Hassallia pseudoramosissima VKM Al-158. The workflow involved WGS, de novo assembly, and comparative metabolic profiling using KEGG, SEED, PLaBAse, antiSMASH, and RhizoSMASH to identify predicted plant growth-promoting (PGP) traits, biosynthetic gene clusters (BGCs), and rhizosphere competence mechanisms. Biosafety was evaluated via Comprehensive Antibiotic Resistance Database (CARD) and in silico toxomics screening. Results: High-quality genome assemblies were obtained for all strains (completeness > 99%). Functional annotation uncovered complete genetic machinery for nitrogen fixation, predicted phosphate mobilization, and phytohormone biosynthesis pathways. Comparative analysis revealed two distinct genomic strategies: a versatile support profile in Nostoc strains (expanded genomes and diverse accessory pathways) and a specialized stimulation profile in Anabaena and Hassallia strains (focused phytohormone pathways). Comprehensive CARD and antiSMASH screenings demonstrated an excellent biosafety profile, confirming the complete absence of regulated cyanotoxin clusters or acquired antibiotic resistance genes of clinical concern. Conclusions: This genome-based bioprospecting serves as a cost-effective pre-selection filter, providing a strong scientific rationale for downstream experimental validation of these strains. The presence of predicted gibberellin biosynthesis pathways and T6SS/T4SS secretion systems in H. pseudoramosissima VKM Al-158 represents a notable genomic feature among soil cyanobacteria. The identified genomic prerequisites suggest that these strains possess strong predictive potential for future development as safe biological resources for sustainable agriculture.

Soil Systems doi: 10.3390/soilsystems10070080

Authors: Ali Bahadur Xian Xue Syed Shameer Salman Zare Wasim Sajjad

Soil salinity is a major constraint to agricultural productivity, causing osmotic stress, ion toxicity, nutrient imbalance, and progressive deterioration of soil biological functions. Beyond its direct effects on plant performance, salinity also generates persistent soil legacies that influence subsequent plant growth through plant-soil feedback (PSF) processes. PSF provides an ecological framework for understanding how plants modify the physicochemical and biological properties of soil and how these altered soil conditions subsequently affect plant growth, health, and resilience. Salinity research has predominantly emphasized soil microorganisms as promoters of plant growth, while their broader role in regulating soil legacy effects remains comparatively underexplored. This review examines whether soil microorganisms may contribute to a transition from salt-amplified negative PSF toward more favorable feedback outcomes by reshaping rhizosphere chemistry, nutrient cycling, pathogen pressure, ion homeostasis, stress signaling, and soil structural stability. However, conditioned-soil bioassays and multi-season saline field trials remain scarce, these proposed pathways are treated as potential mechanisms or testable hypotheses rather than as established evidence of PSF regulation. We first summarize the mechanisms underlying PSF in non-saline systems and then describe how salinity alters plant-, soil-, and microbe-mediated feedback pathways. We further evaluate the potential of halotolerant plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi, actinobacteria, disease-suppressive microbial communities, and synthetic microbial consortia as regulators of PSF, while distinguishing direct salt-tolerance effects from evidence of genuine feedback modulation. Specifically, improved salt tolerance in the inoculated plant is interpreted as direct stress mitigation, whereas demonstrated PSF regulation additionally requires measurable soil conditioning and an effect on a subsequent crop. The novelty of this review lies in organizing studies of salinity-microbiome interactions within an evidence-based PSF framework that differentiates immediate plant responses from rhizosphere modification, conditioned-soil effects, and subsequent-crop performance. The review concludes that microbial strategies for saline agriculture are most likely to succeed when developed as integrated PSF interventions that combine crop traits, indigenous microbiomes, optimized inoculant design, organic matter management, diversified rotations, and multi-season field validation.

Soil Systems doi: 10.3390/soilsystems10070079

Authors: Samuel Ayodele Mesele Ádám Csorba Bas Kempen Mary Steverink-Mosugu Abosede B. Babatunde Mohamed Ouessar Andrei Rozanov Poulouma Louis Yameogo Mamoudou Traore Michael Okoti Erika Michéli Elzo Jeroen Huising

Reliable and harmonised soil information remains critically limited across Africa, constraining soil monitoring, climate-resilient agriculture, and evidence-based land management. Existing soil resources are often fragmented, spatially uneven, outdated, or derived from legacy observations, limiting their usefulness for contemporary continental-scale assessment. The Soils4Africa project implemented a coordinated field campaign across 33 African countries between 2022 and 2025 to establish a harmonised soil monitoring framework for agricultural lands. Using a hierarchical probabilistic sampling design, 24,951 soil samples were collected from 14,311 locations, supported by standardised field protocols, digital data capture, QR-based sample traceability, and centralised quality control. This paper presents the conceptual, operational, and data-management framework underpinning the survey and reports baseline field observations on farming systems, land management, vegetation structure, and soil physical constraints. The framework achieved more than 70% of planned sampling coverage despite major logistical, environmental, and security-related constraints. Baseline observations show that African agricultural landscapes remain dominated by smallholder systems, low external input use, limited soil and water conservation, and widespread dependence on rainfed production. Field indicators also reveal sparse woody vegetation cover and common physical constraints, including compaction, coarse fragments, shallow effective rooting depth, and subsoil barriers. Unlike earlier continental resources based largely on legacy profiles or site-based surveillance, Soils4Africa provides a contemporary, harmonised, spatially structured field-survey framework designed to support future laboratory-based soil assessment, digital soil mapping, land suitability analysis, and long-term soil monitoring. The study therefore provides a scalable model for coordinated soil monitoring across diverse African agroecosystems and establishes an operational baseline for subsequent analytical studies.

Soil Systems doi: 10.3390/soilsystems10070078

Authors: Assiya Myltykbayeva Akmaral Nurmakhanova Murat Toktar Sultan Bazarbayev Serzhan Mombekov Aigul Akhmetova Saule Atabayeva Moldyr Dyusebaeva Bagila Abdullayeva Zhazira Zhunusbayeva Dzhumadil Childibaev Umit Oshakbay Shadiiyam Turailova Aitolkyn Muratbayeva Ünal Murat

Sandy desert ecosystems of Central Asia are highly vulnerable to climate change, land degradation, and increasing anthropogenic pressure, yet the soil conditions supporting native desert vegetation remain insufficiently characterized. This study investigates soil development and physicochemical properties under the canopy of Calligonum aphyllum across different geomorphological conditions in the southern Balkhash region of Kazakhstan. Field investigations were conducted within the Ili River delta, where nine soil profiles were described across three geomorphological settings. Soil samples were analyzed using standard soil analytical methods to assess particle-size composition, soil organic matter, nutrient availability, carbonate content, salinity, and sodicity indicators. The studied soils were predominantly sandy, with sand fractions ranging from 88 to 96% and very low clay content, resulting in weak horizon differentiation, high permeability, and limited water-retention capacity. Soil organic matter and total nitrogen contents were consistently low across all sites. Available phosphorus decreased with depth, particularly in carbonate-enriched horizons, whereas exchangeable potassium remained comparatively high. Total salinity was low, with chloride–sulfate and calcium–sodium dominance, and no evidence of sodicity was observed based on SAR values. Clear differences among geomorphological settings were identified, including relatively homogeneous sandy substrates, dust-enriched semi-stabilized sands, and actively reworked aeolian ridges. The results indicate that C. aphyllum can persist under nutrient-poor, coarse-textured sandy conditions and is associated with surface root concentration, local substrate stabilization, and early soil-profile differentiation. These findings highlight the ecological importance of C. aphyllum in sandy desert habitats and provide site-specific soil information relevant to vegetation-based restoration and sustainable land management in arid regions of Central Asia.

Soil Systems doi: 10.3390/soilsystems10070077

Authors: Pinchas Fine Ami Gips Yaniv Freiberg Uri Mingelgrin

Ammonia injection into soils is used both to supply N to field crops and to reduce soil-borne pests and weeds. Ammonia efficacy depends on its persistence in the soil environment following application. Hence, the extent of ammonia binding in six thermic, xeric Mediterranean soils, varying widely in texture, was evaluated at three moisture contents. Fitting the experimental retention data for each of the six oven-dry soils to the Langmuir isotherm yielded apparent maximum retention capacities (SMAX) ranging from 440 to 1730 mg NH3-N kg−1, and Langmuir binding coefficients (k) ranging from 0.08 to 4.31 L mg−1. The SMAX correlated strongly and linearly with clay content (r2 = 0.946, p < 0.01). The SMAX of the six soils increased with moisture content, likely due to ammonia dissolution in the liquid phase and the adsorption of its cationic derivative. The expected reduction in ammonia binding to the solid phase upon wetting, due to competition with water, was reflected in a sharp, unanimous decrease in the Langmuir model coefficients. A reduction in ammonia retention (but not in SMAX) due to moistening occurred only in the very-fine clayey montmorillonitic soil. While anhydrous ammonia may act as an effective slow-release N source in heavier-textured soils, its tendency to remain in the gas phase in sandy soils is advantageous for pest control.

Soil Systems doi: 10.3390/soilsystems10070076

Authors: Soroor Pashang Fernando Barrio-Parra

Human health risk assessment of vapor intrusion caused by organic pollutants is commonly based on steady-state predictions of partition and vapor migration in the subsoil. This study develops a pseudo-dynamic, process-based Partition–Diffusion Risk Model (PDRM) using a one-dimensional numerical model for organic mixtures to assess the time evolution of cancer and non-cancer risks, indoor air concentrations, and non-aqueous phase liquid (NAPL) formation. The model has been applied to a low-carbon sandy soil without microbial degradation, which might be a worst-case scenario. Six simulation scenarios combined two source concentrations (1000 and 3000 mg/kg) and three source depths (1, 3, and 5 m) over 30 years. Results show that source depth governs exposure dynamics: shallow contamination poses unacceptable risks rapidly but declines quickly, whereas at greater depths, unacceptable levels appear later and persist throughout the exposure period. NAPL formation may act as a secondary source, sustaining vapor release and extending indoor exposure under high-loading conditions. Multicomponent partitioning induces nonlinear, compound-specific behavior, with the first 3–5 years representing a critical period for rapid risk changes. Conventional models show that neglecting NAPL formation and time variability may lead to an underestimation of cancer risk by up to an order of magnitude. These findings highlight the importance of incorporating depth and time-dependent characterization to reduce uncertainty in vapor intrusion risk assessments.

Soil Systems doi: 10.3390/soilsystems10070075

Authors: Xiong Li Zhigang Wang Wei Wang Zhiling Nie

Ground-penetrating radar (GPR) was utilized for subsurface soil investigation in the Yellow River Delta, aiming to provide a scientific basis for the remediation performance of saline soils. The study particularly focuses on the red clay layer, a typical and characteristic soil horizon in this region. GPR antennas with central frequencies of 400 MHz and 900 MHz were adopted to investigate shallow soils within 1 m of the ground surface across three experimental plots (pits, undisturbed soils, and tilled soils) and 18 scattered measurement sites, followed by systematic analysis and interpretation of the acquired GPR profiles. During data acquisition, reasonable survey lines were deployed across the patchy bare areas of cultivated lands covering the experimental plots and measurement points to collect raw GPR data. Meanwhile, subsurface soil data were collected via test pits and borehole sampling along the survey lines. Raw GPR data were further preprocessed and postprocessed to characterize soil horizons and interpret subsurface stratigraphic structures. Finally, the correlations between the relative dielectric permittivity, reflection coefficient, and reflected wave amplitude of each soil layer were systematically analyzed. The results demonstrate that the 400 MHz antenna enables effective identification of soil layers within 1 m depth, while the 900 MHz antenna provides high-resolution detection for soil layers above 0.5 m. The red clay layer presents a distinct strong-amplitude reflection on GPR profiles, and the average relative dielectric permittivity of soils across the study area reaches 30.57. GPR profiles reveal that soil horizons with an absolute reflection coefficient greater than 0.01 yield detectable continuous reflection signals and allow uninterrupted stratigraphic interpretation. An empirical formula was established to calculate soil relative dielectric permittivity from soil moisture content, with a correlation coefficient of 0.9173. However, this formula ignores the influences of soil salinity and other trace soil elements. This study realizes rapid and accurate characterization of the depth and thickness of shallow soil layers, providing technical support for soil remediation of saline–alkali land in the Yellow River Delta. The findings also provide a valuable reference for evaluating the remediation effects, optimizing arable land utilization, preventing and mitigating soil salinization risks, and promoting the sustainable economic development of the study area.

Soil Systems doi: 10.3390/soilsystems10070074

Authors: Caroline Figueiredo Oliveira Selleri Camile Figueiredo Oliveira Luís Reynaldo Ferracciú Alleoni Vinícius de Melo Benites Elcio Ferreira Santos

Phosphorus (P) is one of the most important nutrients to plants, but its bioavailability in agricultural soils is often limited by its low mobility and strong fixation in soil colloids, thus reducing crop productivity and phosphorus use efficiency (PUE). Organomineral fertilizers (OMFs) have been proposed as an alternative to increase the agronomic efficiency of P and promote sustainable soil–plant interactions. In this systematic review, we synthesized scientific evidence on the effects of OMFs on PUE, plant physiological responses, and soil attributes in maize and bean crops. The review followed PRISMA 2020 guidelines and included studies published between 2015 and 2025, retrieved from Scopus, Web of Science, ScienceDirect, SciELO, and Google Scholar. Selected studies compared organomineral phosphate fertilizers with conventional mineral sources and reported outcomes related to PUE, plant performance, or soil attributes. OMFs were generally associated with improved crop growth and increased soil P availability. However, despite frequent comparisons between OMFs and mineral fertilizers, few researchers quantitatively calculated PUE using robust metrics. Plant physiological responses were also poorly explored and, when assessed, were mainly restricted to chlorophyll indices. In addition, the soil microbiome was evaluated in only a few studies, highlighting a major gap in integrated soil–plant–microorganism research.

Soil Systems doi: 10.3390/soilsystems10070073

Authors: Amina Braimi Hinde Benjlil Ilyass Filali Alaoui Tayeb Obidari Amine Idhmida Mouna Belmouden Sarhane Larbi ElMehdi Elhadda Hajar Issouktane Mohamed Ait Hamza Abdelhamid El Mousadik Fouad Msanda Sergio Saia El Hassan Mayad

Environmental gradients associated with continentality shape terrestrial ecosystems by modifying biodiversity patterns, community structure, and ecosystem functioning. In arid ecosystems, where water and thermal constraints are pronounced, soil organisms represent sensitive indicators of environmental change. Soil nematodes, due to their functional diversity encompassing bacterivores, fungivores, herbivores, omnivores, and predators, constitute effective bioindicators of soil health. We hypothesized that increasing continentality (thermal amplitude) would progressively reduce nematode diversity and functional complexity while altering CUE and metabolic footprints through community compositional shifts. A total of 130 soil samples were collected across three bioclimatic zones (island, coastal, and semi-continental) within the Arganeraie Biosphere Reserve, Morocco, and analyzed for nematode abundance, diversity, trophic structure, ecological indices, and functional traits. Nematode abundance and richness were significantly higher in the island zone compared to the coastal and semi-continental zones, while Shannon diversity did not differ significantly. The island zone exhibited a balanced trophic structure with higher proportions of bacteribores, fungivores, herbivores, and omnivores–predators, than the coastal and semi-continental zones. CUE values were consistently low (<0.5) across all zones, with the widest distribution in the island zone. Thermal amplitude was negatively associated with nematode biomass (R = −0.36), production (R = −0.27), and all trophic footprints, with herbivores showing the steepest decline (R = −0.51). Notably, total energy flux remained relatively stable despite reductions in diversity and trophic complexity, suggesting functional redundancy within dominant bacterivore guilds. These findings support the hypothesis that increasing continentality is associated with reduced nematode diversity and functional complexity, alongside altered carbon processing efficiency. This study underscores the value of integrating trophic, metabolic, and energetic approaches for assessing soil health vulnerability in Mediterranean agroecosystems under climate change.

Soil Systems doi: 10.3390/soilsystems10070072

Authors: Kristina Osina Korytina Maria Anna Gunina

Replacing peat in green roof substrates with sustainable alternatives while maintaining plant performance and ecosystem services remains a critical challenge. We studied biochar-substrate interactions across four commercial green roof formulations (based on the type of organic component) in a greenhouse experiment: pure vermicompost, vermicompost + fen peat, fen peat, and mixed fen/high-moor peat. Substrates were amended with straw biochar, pine bark biochar, or left unamended (5% v/v, n = 4 replicates) and planted with a grass seed mixture mimicking early green roof establishment. Plant growth, nutrient contents (nitrate and phosphate contents), and microbial indicators (microbial biomass carbon (MBC), qCO2, and enzyme activities) were measured 30 days after the experiment began. Straw biochar in vermicompost boosted nitrate (90.8 mg kg−1) and root N (3.1%) compared to the control, while pine bark biochar in mixed peat released phosphate (+375%) and maximized MBC (874 µg g−1). Biochar intensified substrate effects, suppressing CO2 in peat through liming effects (pH from 4.6 to 6.5–7.1) but priming respiration in vermicompost via labile C supply. PCA explained 63% of the variance, with nitrate, plant N, and microbial parameters driving substrate separation. These short-term greenhouse results demonstrate critical biochar-substrate specificity for green roof substrate development, emphasizing formulation-specific matching over universal biochar application.

Soil Systems doi: 10.3390/soilsystems10070071

Authors: Polina Kuryntseva Darya Tarasova Vyacheslav Babichuk Natalya Danilova Svetlana Selivanovskaya

Soil organic matter (SOM) stabilization is closely linked to microbial community structure and function, yet reliable biological indicators remain insufficiently defined. This study aimed to identify microbial and biochemical markers of SOM accumulation under different land use systems (cropland, mown with phytomass removal, mown without phytomass removal, and fallow) in gray forest soils. Soil profiles were investigated in four land use types (cropland, mown with phytomass removal, mown without phytomass removal, and fallow) in the Laishevsky District (Russia). Physicochemical properties, SOM fractions, basal respiration, substrate-induced respiration, Biolog EcoPlates, quantitative PCR, and metagenomic data were used to assess microbial diversity and activity. Microbial communities differed substantially among land use systems and soil horizons, with bacterial communities in fallow soils dominated by oligotrophic taxa, such as RB41, Candidatus Udaeobacter, and KD4-96, whereas arable and managed grassland soils showed increased relative abundance of copiotrophic genera, particularly Pseudomonas and Polaromonas. Fungal communities were primarily represented by Mortierella, Penicillium, Trechispora, and Metarhizium, while both bacterial and fungal diversity decreased with soil depth, and metabolic profiling indicated preferential utilization of carbohydrates and carboxylic acids across all land use types. The highest organic matter and total organic carbon (TOC) were in soils under mowing without phytomass removal and fallow land, while arable soils showed the lowest values. Microbial diversity decreased with soil depth across all variants. Hay meadow soils exhibited elevated metabolic activity and higher metabolic quotient (qCO2), indicating intensified carbon turnover or microbial stress, whereas arable soils were characterized by reduced substrate utilization and simplified community structure. Oligotrophic bacterial taxa were associated with more stable SOM conditions, while copiotrophic dominance reflected rapid carbon turnover. The results demonstrate that microbial community composition, functional activity, and specific taxa (e.g., oligotrophic bacteria, saprotrophic fungi, arbuscular mycorrhizal fungi) can serve as sensitive indicators of SOM stabilization processes. These findings support the development of microbiome-based diagnostic tools for assessing soil carbon dynamics and guiding sustainable land management strategies.

Soil Systems doi: 10.3390/soilsystems10070070

Authors: Hatim Sanad Rachid Moussadek Latifa Mouhir Majda Oueld Lhaj Ahmed Ghanimi Khadija Manhou Houria Dakak Abdelmjid Zouahri

Soil quality is central to agricultural sustainability and food security, yet coastal agroecosystems are increasingly threatened by degradation from intensive practices and seawater intrusion. This study aimed to integrate soil quality index (SQI), statistical modeling, machine learning (ML), and decision analysis to assess and manage soil health in the Skhirat coastal plain of Morocco. A total of 30 topsoil samples were collected and analyzed for chemical and nutrient properties. Spatial interpolation revealed strong coast–inland gradients where EC ranged from 0.47 to 6.3 dS/m with the highest salinity in the south-western fringe, while CEC (8.4–39.7 cmol/kg) and OM (0.54–2.81%) peaked inland. Principal component analysis (PCA) explained 65.9% of total variance, with salinity drivers loading negatively against fertility indicators. Redundancy analysis (RDA) biplots highlighted antagonism between salinity and fertility axes. The PCA-minimum data set (MDS)-SQI integrated key indicators and ranged from 0.084 to 0.897 (mean 0.614), classifying 33% of sites as low quality. The ML model linear regression achieved the best performance (R2 = 0.907). Multi-criteria decision analysis (MCDA) using TOPSIS and PROMETHEE II prioritized coastal sites with indices up to 0.882, and robust underweight sensitivity (Spearman ρ = 0.992). This integrated framework demonstrates that soil chemical monitoring, AI prediction, and MCDA can jointly deliver robust, site-specific management strategies for vulnerable coastal agroecosystems.

Soil Systems doi: 10.3390/soilsystems10070069

Authors: Francis Akitwine Rebecca A. Wokibula Johnson G. Mtama Amber D. Anderson Shillah Kwikiiriza C. Lee Burras

Plinthite is a major pedogenic feature in the Kamuli catena, posing significant challenges for agricultural land use. This study investigates the morphological expression and mineralogical insights into plinthite within the soil-landscape of Kamuli District. Soil characterization involved detailed field morphological descriptions along the Kamuli catena followed by laboratory characterization of major soil properties. Plinthite mineralogy was determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Morphology of plinthic soils varied along the catena with summit pedons exhibiting shallow plinthic horizons and backslope pedons showing comparatively deeper occurrences. The lowlands underlain by alluvium of the Holocene lacked plinthite. Mineralogical analysis of ten plinthite samples identified two distinct assemblages. Group 1 (quartz, kaolinite, hematite, goethite, manganite) represents a highly weathered endmember associated with stable summits. Group 2 (muscovite, kaolinite, hematite, goethite, manganite), with elevated K, Mg, Na, and Ca in SEM-EDS, indicating they are recent compared to Group 1. This elemental composition directly reflects the signature of the parent material preserved within Group 2 samples. Plinthite in the Kamuli catena is a relict feature, whose formation is tied to past drainage regimes. Its multi-stage history is recorded in the two mineralogical groups separated by hundreds of thousands of years of landscape evolution. Group 1 represents plinthite from the deeply weathered African Surface. Group 2 is later formed on the substrate exposed by stripping along the Victoria Nile.

Soil Systems doi: 10.3390/soilsystems10070068

Authors: Christian Mera-Parra Pablo Ochoa-Cueva Jose Damian Ruiz Sinoga Paola Duque Sarango

For hydrological parameterization in high-Andean catchments, it is necessary to understand whether near-surface hydro-structural soil properties can provide a surrogate signal of particle-size composition when direct texture information is sparse. This study evaluated the extent to which sand, silt, and clay fractions can be approximated from organic matter (OM), bulk density (ρb), and saturated hydraulic conductivity (Ksat) in the Zamora Huayco (ZH) and Irquis catchments, southern Ecuador. A harmonized dataset (n=44) was analyzed through exploratory statistics, compositional assessment, correlation analysis, PCA, fraction-wise regression, ILR-based modeling, AIC/BIC term reduction, sensitivity analysis excluding OM, nested LOOCV, and bootstrap-based uncertainty intervals. Among LULC classes, samples classified as paramo occupied a distinct high-Andean hydro-edaphic domain, characterized by a differentiated relationship between soil physical properties and hydrological behavior. PCA showed that the dominant covariance structure involved OM, ρb, Ksat, and the redistribution between sand and silt. The BIC-reduced ILR model provided the most balanced formulation, with positive nested LOOCV performance for sand, silt, and clay (RLOOCV2=0.147, 0.704, and 0.124, respectively) and exact 100% compositional closure after inverse transformation. Silt was the most stable predicted fraction, whereas sand and clay retained larger residual uncertainty, stronger tail departures, and partial compression of the observed variability. The proposed equations provide local hydro-pedotransfer support, although their predictive signal remains dependent on further refinement, uncertainty assessment, and external validation before regional application.

Soil Systems doi: 10.3390/soilsystems10070067

Authors: Besarion Meskhi Dmitry Rudoy Sergey Gorbov Andrey Polyakov Mary Odabashyan Arkady Mirzoyan Svetlana Studennikova Denis Kozyrev

The classification position of substrates forming on the beds of aquaculture ponds remains a poorly resolved issue at the intersection of pedology, limnology, and aquaculture science. We examine how major international and national soil classification systems—the USDA Soil Taxonomy, the World Reference Base for Soil Resources (WRB), the German Bodenkundliche Kartieranleitung, the Australian Soil Classification (ASC), the Russian Soil Classification, and the classification systems of Brazil and China—approach the systematics of subaqueous soils and their aquaculture analogues. A systematic literature search was conducted across the Web of Science, Scopus, and Google Scholar databases covering the period from 1953 to 2025. Our analysis reveals that Soil Taxonomy provides the most developed taxonomic framework through specialized suborders (Wassents and Wassists), while the WRB offers the greatest flexibility via its qualifier system (subaquatic, limnic, and gleyic). The German classification uniquely assigns subaqueous soils to the highest taxonomic level (division) with a substantive typology that is directly applicable to pond substrates. The Australian classification contributes a three-part sulfidic material typology of practical significance for pond management. The Russian and Brazilian systems currently lack formal taxa for subaqueous soils, although recent proposals (e.g., Aquazems) may address this gap. The Chinese paddy soil model offers a conceptual bridge between subaqueous pedology and aquaculture. No existing system adequately addresses the specific anthropogenic impacts of aquaculture management on pond soil formation. Permanently inundated little-disturbed ponds fall within the subaqueous soil concept, whereas intensively managed, frequently drained or dredged ponds are better treated as anthropogenic soils with a subaqueous phase. We recommend the WRB (4th edition, 2022) as the most suitable framework for current classification of aquaculture pond soils while acknowledging that a multi-system approach may ultimately prove most effective. These findings carry particular relevance for countries of the former Soviet Union (CIS), where extensive pond aquaculture is practiced but pond substrates remain outside formal pedological classification.

Soil Systems doi: 10.3390/soilsystems10060066

Authors: Carlos Alcides Villalba Algarin Marcos Fabian Sanabria Franco Alodia Concepción González José Lavres

Soil biological activity integrates microbial processes involved in organic matter decomposition and nutrient cycling, yet its long-term response under agricultural systems in Paraguay remains poorly documented. This study evaluated soil biological activity in a 32-year field experiment in the Eastern Region of Paraguay, comparing cropping systems differing in tillage intensity and crop rotation diversification. Soil samples from the 0–20 cm layer were analyzed for microbial biomass carbon (MBC), β-glucosidase (BG), urease (URE), acid phosphatase (AP), arylsulfatase (ARS), soil organic carbon (SOC), total nitrogen (TN), available phosphorus (P), sulfur (S), and pH. Our results revealed that BG, URE, and AP increased under no-tillage, particularly in the most diversified no-tillage rotation, with 71%, 90%, and 51% higher activities, respectively, than conventional tillage. MBC and ARS were not significantly affected by cropping systems. Principal component analysis, Spearman correlations, and Mantel analysis indicated that enzymatic responses were associated with SOC, TN, P, S, and pH, linking soil biological activity with chemical attributes related to nutrient cycling. These findings show that diversified no-tillage strengthens soil biological functioning under representative Paraguayan grain-production conditions, providing long-term local evidence to guide soil-health management, crop diversification strategies, and more sustainable agricultural systems in the region.

Soil Systems doi: 10.3390/soilsystems10060065

Authors: Ayijiamali Kudureti Ümüt Halik Changyan Tian Guanghui Lv

Soil salinization threatens agricultural sustainability and food security, especially in arid and semi-arid regions, yet how salinity gradients reshape multi-trophic networks and their associations with functional genes remain unclear. We investigated soil bacteria, fungi, protists, nematodes, and the carbon-fixation gene cbbL along a natural salinity gradient (electrical conductivity: 1.2–12.4 mS cm−1) in Karamay, Xinjiang. Salinity acted as a key environmental filter, significantly differentiating biotic communities into low- and high-salinity groups. Compared with bacteria and fungi, protists and nematodes exhibit higher sensitivity to salinity shifts from non-saline to slightly saline soils, with their Shannon diversity decreasing by 74.2% and 50.4%, respectively (p < 0.05). High salinity significantly reduced the connectivity, modularity, and robustness of soil multi-trophic co-occurrence networks, resulting in 36.8% fewer edges, 24.2% lower modularity, and diminished network robustness compared to low-salinity conditions. Crucially, salinity was associated with functional decoupling, defined as a shift in the dominant drivers of microbial carbon sequestration potential. At low salinity, biotic factors explained 94.2% of cbbL variation, whereas at high salinity abiotic factors governed 86.1%, as shown by GBM (Gradient Boosting Machine) analyses. Our findings indicate that protists and nematodes can act as early warning indicators for soil salinization, and biotic network complexity represents a core metric for assessing saline soil ecosystem stability. This study reveals salinization-induced biota–function decoupling patterns and provides insights for saline soil health assessment and biotic restoration.

Soil Systems doi: 10.3390/soilsystems10060064

Authors: Craig Rasmussen Catherine Mortensen Kevin Ellett

Integrated crop–livestock systems (ICLS) that couple crop production, cover crops, and grazing present a promising strategy for soil organic carbon (SOC) sequestration. Long-term assessments of SOC change under ICLS management are limited. This study quantified SOC stocks from management systems typical of the warm, humid southern Midwest, USA, including conventional continuous cereal crop production, permanent pasture, hardwood forest, and decadal-scale ICLS management. The ICLS consisted of no-till production of corn silage with a winter ryegrass cover crop grazed by cattle. We hypothesized greater SOC stocks in the ICLS relative to conventional management, with the greatest increase in surface horizons. Soil cores were collected to a depth of 120 cm, subset into 0–30 cm, 30–60 cm, and 60–120 cm sections, and analyzed for SOC, particulate, and mineral-associated organic matter. Results demonstrated that after 15 years, ICLS SOC stocks were significantly greater than conventionally managed fields and comparable to those of permanent pasture and hardwood forest. The SOC differences were predominantly in the upper 30 cm. Using a space-for-time approach, we calculated an average annual SOC accrual rate of 1.3 Mg C ha−1 yr−1, similar to estimated sequestration rates from biogeochemical model simulations. The majority of additional SOC was allocated to particulate organic matter. Significantly greater mineral-associated organic carbon was also observed. Stable carbon isotope data indicated the ryegrass cover crop was likely the primary source of additional SOC in the ICLS. These findings demonstrate the potential of ICLS to increase SOC and enhance soil health over decadal timescales.

Soil Systems doi: 10.3390/soilsystems10060063

Authors: Elói Panachuki Dorly Scariot Pavei Roniedison da Silva Menezes Wander Cardoso Valim Júlio César Salton Sonia Armbrust Rodrigues Wilk Sampaio de Almeida

The long-term effects of agricultural management systems (AMS) on soil physical properties and water infiltration in tropical Ferralsols remain incompletely understood. We assessed steady-state infiltration rates and soil physical properties in a Ferralsol after 20 years under five AMS in a Cerrado–Atlantic Forest transition area in Brazil: no-tillage (NT), conventional tillage (CT), integrated crop–livestock in crop (CL-C) and livestock (CL-L) phases, and permanent pasture (PP). Soil samples were collected at four depths, and infiltration was measured using the InfiAsper simulator at 60 mm h−1. Integrated systems showed the best topsoil (0–0.05 m) physical condition, with higher macroporosity, aggregate stability, and organic carbon than NT and CT. Surface bulk density under PP was similar to integrated systems; higher bulk density values were observed under NT and CT at 0.10–0.20 m. Steady-state infiltration rates ranged from 26.40 mm h−1 (PP) to 54.32 mm h−1 (NT), with integrated systems averaging 59% higher than PP. Total SOC stocks (0–0.40 m) were significantly greater under CL-L (92.7 Mg C ha−1) and CL-C (88.1 Mg C ha−1) than PP (73.5 Mg C ha−1; p = 0.004), driven by higher subsoil SOC concentrations under integrated systems; the lower subsoil bulk density under PP partially attenuated its calculated stock. These results demonstrate that integrated crop–livestock systems simultaneously improve soil physical condition, water infiltration, and carbon accumulation per unit land area, supporting sustainable intensification in the Brazilian Cerrado and Atlantic Forest biomes.

Soil Systems doi: 10.3390/soilsystems10060062

Authors: Mythra Revanna Prabhash Kumar Mishra Rituraj Shukla Jagadeesh Uppar Lohit Kumar Baishya

Drought stress is a major abiotic constraint limiting mung bean (Vigna radiata L.) productivity in arid and semi-arid agroecosystems. This study investigated the individual and synergistic effects of Bradyrhizobium sp. and arbuscular mycorrhizal fungi (AMF) on plant growth, nutrient acquisition, mycorrhizal colonization, and yield of mung bean under contrasting soil moisture regimes. A greenhouse pot experiment was conducted using a factorial completely randomized design with six microbial treatments (uninoculated control, Acaulospora scrobiculata, Claroideoglomus etunicatum, Bradyrhizobium sp., and their respective co-inoculations) and three field capacity levels (50, 75, and 100%). Drought stress was imposed gravimetrically 20 days after sowing. Water limitation significantly reduced growth, biomass accumulation, nutrient uptake, mycorrhizal colonization, and yield in uninoculated plants. In contrast, microbial inoculation markedly mitigated drought-induced adverse effects, with co-inoculation showing the strongest response. Plants receiving combined AMF and Bradyrhizobium inoculation exhibited significantly higher plant height, shoot and root biomass, total dry matter, nitrogen and phosphorus uptake, and yield attributes across all moisture regimes, particularly under severe drought (50% field capacity). Mycorrhizal dependency increased with increasing drought severity, highlighting a greater functional reliance on AM symbiosis under water-limited conditions. Enhanced drought tolerance was closely associated with increased root colonization and improved nutrient acquisition driven by synergistic AMF–Bradyrhizobium interactions. These findings demonstrate that tripartite symbiosis represents a sustainable bio-inoculant strategy to enhance drought resilience and productivity of mung bean under climate change-induced water stress.

Soil Systems doi: 10.3390/soilsystems10050061

Authors: Xi Chen Xi Chen Batande Sinovuyo Ndzelu Yueling Zhang Shuihong Yao

Wheat straw is a plant-derived substrate rich in cellulose, hemicellulose, and lignin and represents a major carbon input to agricultural soils. Mineral-associated organic carbon (MAOC) is the most stable soil carbon pool, yet how mineral structure regulates the stability of straw-derived MAOC through microbial processing remains unclear. Here, straw-derived MAOC was formed in artificial soils containing five clay minerals (halloysite, kaolinite, illite, vermiculite, and montmorillonite) during a two-year incubation, followed by a 45-day incubation with a standardized microbial community to quantify CO2 emission and net carbon balance. Mineral type regulated MAOC mineralization (38.54–54.48 mg C g−1 MAOC). Vermiculite produced the highest CO2 emission but maintained a positive net carbon balance, whereas illite showed net carbon loss (−0.53 g kg−1). Kaolinite, halloysite, and montmorillonite exhibited lower mineralization and retained net carbon. The 2:1 clay minerals enhanced interlayer interactions and favored accumulation of C=O and aromatic compounds, reflecting stronger microbial transformation and residue retention. In contrast, 1:1 minerals stabilized carbon via edge hydroxyl bonding, which restricted substrate accessibility and slowed decomposition. Cumulative mineralization decreased with initial MAOC carbon but increased with dissolved organic carbon and bacterial abundance. Net carbon retention increased with N-acetylglucosaminidase activity and fungal abundance, indicating joint microbial control via nutrient acquisition and fungal processing. Two contrasting stabilization regimes were observed: high turnover driven by vermiculite and halloysite, and strong protection dominated by montmorillonite and kaolinite. These differences indicate that MAOC stability is jointly constrained by mineral-regulated accessibility and microbial transformation processes.

Soil Systems doi: 10.3390/soilsystems10050060

Authors: Tamás Zsolt Vári Pál Sümegi Elemér Pál-Molnár

This study presents a high-resolution, multi-proxy palaeoenvironmental reconstruction of the Tövises fen at Pocsaj, Hungary, utilising lithostratigraphical, geochemical, malacological, and palynological analyses supported by radiocarbon dating. The sedimentary sequence documents the transition from a Late Glacial fluvial system (c. 19,000–16,000 cal BP) to a cut-off meander and subsequent oxbow lake, eventually evolving into a peat-forming fen. Malacological and palynological data reveal the co-occurrence of cold-tolerant Late Pleistocene elements and the early appearance of thermomesophilous taxa at the onset of the Holocene. This suggests that the favourable microclimate of the adjacent loess-covered high bank and the humid alluvial plain functioned as a cryptic refugium for temperate broad-leaved trees and associated fauna during the Late Glacial. Anthropogenic impact is traceable from the Mesolithic, characterised by Corylus management, intensifying through Neolithic agriculture to a peak during the Roman Imperial Period. Geochemical markers in the upper peat sequence reflect increased biomass and medieval habitation, while recent malacofaunal shifts indicate progressive desiccation. Despite modern drainage attempts, the Tövises fen remains a biodiversity hotspot of high conservation value, preserving relict wetland communities.

Soil Systems doi: 10.3390/soilsystems10050059

Authors: Shengchang Huai Qingyue Zhang Yuwen Jin Shenzhong Tian Yueming Chen Xilin Guan Tao Sun Shenqiang Lv Zichao Zhao Weijia Yu Ran Li Gilles Colinet Changai Lu Xinhao Gao

Rapid and cost-effective estimation of soil total nitrogen (TN) is essential for soil fertility assessment and nutrient management. However, the performance of laboratory visible–near-infrared (Vis–NIR) models is shaped not only by preprocessing and modeling strategy but also by sample preparation and the soil’s compositional background. In this study, TN prediction was evaluated using 376 topsoil samples from two contrasting datasets: Mollisols from the black-soil region of Northeast China and Ultisols from Qiyang County, Hunan Province, southern China. Spectra acquired over 350–2500 nm for three particle-size fractions were preprocessed using Savitzky–Golay smoothing combined with standard normal variate (SNV), first-derivative, or second-derivative transformations, and modeled using partial least squares regression (PLSR), support vector regression (SVR), and extreme gradient boosting (XGBoost). Model development used a 5 × 5 nested cross-validation followed by evaluation on a sample-grouped held-out test set. Among all combinations, XGBoost with first-derivative preprocessing on the 0.25 mm fraction produced the best performance, with test R2 values of 0.91 for Mollisol and 0.78 for Ultisol. Shapley additive explanations (SHAP) and principal component analysis (PCA) consistently identified informative spectral regions at 430–480 and 1330–1450 nm for Mollisol and at 585–635, 820–900, and 2180–2240 nm for Ultisol. Prediction errors were larger in the sampled Ultisol dataset and increased with DCB-extractable Fe and mineral backgrounds. A second-stage log-domain residual correction incorporating ancillary soil properties further reduced the Ultisol RMSE from 0.30 to 0.27 g kg−1. These findings support the 0.25 mm, first-derivative, XGBoost workflow as a robust laboratory Vis–NIR approach for TN prediction and indicate that composition-aware residual correction can improve prediction in oxide- and mineral-rich soils.

Soil Systems doi: 10.3390/soilsystems10050058

Authors: Zerihun Asrat Mekbib Fekadu Zerihun Woldu Sebsebe Demissew Betelhem Mekonnen Lars Opgenoorth Georg Miehe Wolfgang Zech

Soil organic matter (SOM) dynamics in tropical montane ecosystems remain poorly understood, particularly regarding the relative importance of particulate versus mineral-associated fractions under varying disturbance regimes. This study investigated SOM fraction distribution across the Ericaceous and Afroalpine belts of Bale Mountains National Park, Ethiopia, an Andosol-dominated landscape subject to recurrent fire. Using a stratified sampling design (n = 30 plots) across four vegetation classes (Ericaceous belt, fragmented Ericaceous belt, herbaceous and heathland, and giant Lobelia areas), three fire history categories (<10, 10–25, and >25 years since fire), and three topographic positions (northern slopes, southern slopes, and central plateau), we quantified coarse particulate organic matter (cPOM: 149–2000 μm), fine particulate organic matter (fPOM: 53–149 μm), and mineral-associated organic matter (MAOM: <53 μm). Particulate fractions dominated the SOM pool, with cPOM and fPOM together accounting for >99% of measured organic carbon. Multivariate ordination revealed a primary gradient (PC1, 61.7%) contrasting particulate-dominated soils in less disturbed areas with relatively MAOM-enriched soils in fire-impacted and fragmented zones. A global comparison reveals a profound stability gap: the Bale Mountains utilize <2% of the mineral stabilization potential of comparable Andosols, demonstrating that extreme fire frequency (<25 yr return interval) overrides even the most reactive mineralogy. We critically evaluate whether standard size-based fractionation adequately captures mineral-associated carbon in volcanic soils and discuss methodological limitations. These results provide baseline data for conservation planning in this biodiversity hotspot and underscore the need for fire management strategies that balance ecological integrity with carbon storage objectives.

Soil Systems doi: 10.3390/soilsystems10050057

Authors: Cuilan Wei Shun Li Bingshuai Cao Songjuan Gao Hao Liang

Co-utilization of milk vetch as green manure (GM) and rice straw is an effective practice for reducing nitrogen (N) input while maintaining crop productivity in rice-based agroecosystems in southern China. The effects of soil carbon (C) and N pools and their fractions under green manuring and rice straw return, combined with reduced N fertilization remain to be clarified. A four-year field experiment was carried out to explore the effects of synergistic utilization of GM and rice straw (GMS) on rice yield, soil C and N fractions, and their contributions to rice productivity. The study demonstrated that compared with winter fallow (WF), GMS increased rice yield by 20.3% under 40% reduction in N fertilization (N60). GM application increased soil total N content by 16.5% and 18.0% significantly relative to WF under N0 and N60, respectively. GMS treatment demonstrated improvements in the soil organic C pool and enhanced soil N activity. Compared with WF, soil organic C, mineral-associated organic C and particulate organic C under GMS increased by 11.1% and 24.9%, 31.3% and 13.8%, 13.1% and 47.3% at N0 and N60 levels, respectively. Under N60, GMS increased heavy-fraction organic C content by 42.6% while reducing light-fraction organic C content by 28.0% compared to WF, thereby enhancing soil C pool stability. Regarding soil N fractions, GMS increased particulate organic N content by 60.8% and 79.3%, and mineral-associated organic N content by 89.7% and 43.4% at N0 and N60 levels, respectively. Under N60, GMS reduced heavy-fraction organic N content while increasing light-fraction organic N content, thereby enhancing soil N availability. Based on the results of Mantel tests and random forest prediction, our analysis found that N and particulate organic C served as the key factors affecting rice yield. In conclusion, GMS combined with 60% of the conventional N rate enhanced rice yield by mediating soil C sequestration and N availability, proving to be an effective strategy for improving soil fertility and ensuring food security in the rice-growing region of southern Jiangsu, China.

Soil Systems doi: 10.3390/soilsystems10050056

Authors: Angélica Vázquez-Ortega Matthew Franks Katarina Kieffer

Conventional tillage, a soil preparation practice used to produce a fine seedbed, can disturb the soil profile by promoting soil compaction and soil organic matter (SOM) degradation. In contrast, conservation tillage, such as no-till, has the potential to sustain or increase SOM. This study aimed to (1) quantify soil organic carbon (SOC) content under conservation tillage and conventional tillage practices, (2) describe the degree of aromaticity of bioavailable SOC using fluorescence spectroscopy, and (3) correlate SOC quantity with nitrogen and phosphorus retention in soils. Fluorescence spectroscopy is a sensitive and non-destructive tool that allows for the assessment of bioavailable SOC quality related to the molecular structure, degree of aromaticity (cyclic molecules with carbon double bonds), and recalcitrance (difficulty of decomposition) of organic compounds. This study employed fluorescence excitation–emission matrices combined with parallel factor analysis (EEM-PARAFAC) to identify humic-like, fulvic-like, and protein-like substances. Data on agricultural management practices were collected from spring 2014 until fall 2017. We obtained soil samples (fall 2017) from farms in the Western Lake Erie Basin, Ohio, and performed geochemical characterization in the bulk soil and aqueous extraction. Our results showed that no-till and minimal tillage fields consistently had greater SOC and fluorescence intensity in the humic-like acids region when compared to conventional tilled fields (no-till: 34,000 mg TOC kg−1; tilled six times: 16,000 mg TOC kg−1). No-till enhanced SOC stabilization. In addition, conservation tillage practices retained the largest total nitrogen (no-till: 2800 mg TN kg−1; tilled six times: 1350 mg TN kg−1) and total phosphorus (no-till: 470 mg TP kg−1; tilled six times: 250 mg TP kg−1) concentrations at all studied depths (0–30 cm) when compared to conventional tilled fields. Conservation tillage promotes the accumulation of highly aromatic organic compounds favoring high cation exchange capacity, and NO3− and PO43− retention and plant bioavailability.

Soil Systems doi: 10.3390/soilsystems10050055

Authors: Paula Alejandra Gómez-Palomo Daniela Monserrat Sánchez-Pérez Erika Flores-Loyola José Juan Torres-Martínez Javier Ulises Hernández-Beltrán Jorge Alejandro Aguirre-Joya Nathiely Ramírez-Guzmán David Francisco Lafuente-Rincón

Soil–Forage–Livestock systems (SFL-systems) integration is fundamental for sustainable land management in arid lands, where conventional crop production is often unfeasible. Aridisols dominate dryland agroecosystems and their edaphic constraints, together with climatic limitations, constitute a major bottleneck for fertility and productivity in key arid regions worldwide. This narrative review provides a taxonomic and edaphic framework to guide sustainable SFL-systems and integrates current approaches and technological applications for forage production in arid environments, focusing on an edaphic-digital scheme that combines organic and inorganic soil amendments with AI-based decision support to improve Aridisols productivity and resilience. Searches of the literature (ScienceDirect, EBSCOhost, Clarivate Web of Science; English, 2021–2025) screened 309 records and selected 169 references; seminal older works were consulted for context. Representative quantitative outcomes from the reviewed literature include SOC increases of ~15–30% after multi-year organic inputs; forage biomass gains of ~10–25% following amendments that correct sodicity; and water-productivity improvements up to ~30% with hydrogels or biochar. AI tools can improve soil diagnostics and amendment selection (diagnostic accuracy improvements of ~15–30% in recent studies) and generate predictive models of amendment–response that facilitate optimization of application rates and water use. The novel contribution of this review is the explicit linkage of SFL-systems and amendment-based soil restoration with AI-driven diagnostics and decision support, providing actionable metrics and research priorities to translate digital diagnostics into measurable forage gains in arid and semi-arid regions. Overall, the evidence suggests that targeted soil restoration, reinforced by AI-based support systems, is a feasible strategy to increase forage availability and ecosystem service provision in drylands.

Soil Systems doi: 10.3390/soilsystems10050054

Authors: Veneramaria Urso William Trenti Mauro De Feudis Gloria Falsone Livia Vittori Antisari Gianluca Bianchini

Vegetation strongly influences soil formation, yet its effect on Rare Earth Element (REE) distribution and fractionation across treeline ecotones remains insufficiently constrained. The present study investigated how contrasting plant communities, Vaccinium myrtillus heathlands and Picea abies forests, affect pedogenetic pathways and REE behavior in sandstone-derived soils of the Northern Apennines (Italy). Six soil profiles were characterized for bulk geochemistry, selective Fe–Al extractions, particle-size distribution, and REE concentrations. Principal component analysis and hierarchical clustering identified pedogenetic drivers and horizon groupings. Under Vaccinium myrtillus, thick acidic organic horizons promoted organo-metal complexation and incipient podzolization, whereas Picea abies soils showed thinner organic layers and enhanced mineral weathering, leading to Bw development with higher silt–clay contents and elevated Al/N ratios. These pathways were captured by Fe–Al indicators and the Spodic Index. REE distributions showed vegetation-related differences in surface horizons and Eu–Ce anomalies, but they did not reproduce Fe–Al pedogenetic clusters, reflecting strong parent-material control. The coexistence of podzolic and cambic pathways at the treeline highlights pronounced spatial heterogeneity and vegetation effects. Plant composition may redirect pedogenesis, influencing nutrient cycling and metal mobility. Additionally, these findings emphasize the need to integrate multivariate statistics with established pedogenetic indicators when evaluating geochemical properties in mountain soils.

Soil Systems doi: 10.3390/soilsystems10050053

Authors: Laura Sanchez-Martin Jhoeel Uvidia Gabriel Gascó Ana María Mendez Mark R. Theobald Patricia Almendros

This study is the first to investigate volcanic ash (VA) as a soil amendment to mitigate nitrous oxide (N2O) emissions, a potent greenhouse gas mainly produced through nitrification and denitrification processes in agricultural soils. The experiment assessed the effects of VA mixed with soil and combined with mineral (NH4NO3, N) or organic (poultry manure, O) fertilizer on N2O emissions, soil mineral nitrogen (NO3− and NH4+), trace metals (Zn, Cu, Mn), and crop yield in a 4-month pot experiment including treatments with and without VA. Results showed that VA reduced N2O emissions by 55% in mineral fertilizer treatments and 71% in organic fertilizer treatments compared to soils without VA. This reduction was associated with significant changes in nitrogen availability. In mineral fertilizer treatments with VA, soil NO3− concentrations remained high, potentially limiting denitrifier activity, while in organic treatments VA appeared to inhibit nitrogen mineralization. Additionally, VA increased soil concentrations of Zn, Cu, and Mn, which were negatively correlated with N2O emissions, suggesting an influence on microbial processes. Importantly, crop yields were not affected by VA application. Although promising, these preliminary findings highlight the need for further research to optimize application rates and evaluate long-term effects across soil types and management systems.

Soil Systems doi: 10.3390/soilsystems10050052

Authors: Tongyao Wu Jihong Qin Shuangchao Wang Hui Sun Xinyue Hu Kaiyan Li

Reactive oxygen species (ROS) are a class of molecules or free radicals with strong oxidizing properties. They have attracted increasing attention in soil research in recent years because of their perceived importance in many soil biochemical processes. Previous reviews of ROS in soil mainly focused on their impacts on carbon emissions and organic pollutant remediation, with few descriptions of the mechanisms responsible for ROS generation, and a comprehensive understanding of their environmental effects is still lacking. Therefore, the present review provides details on the sources and underlying generation mechanisms of ROS in soil. These mechanisms include inputs via atmospheric deposition, metal–mineral reactions, root exudation, microbial metabolism, enzymatic reactions and various organic matter transformations. In contrast to previous reviews, we also discuss mutual conversion between different types of ROS in soil. The impacts of ROS on the soil environment are further explored, such as element cycling, pollutant degradation, and the growth and reproduction of plants and microorganisms, in order to provide a systematic understanding of the various processes involving ROS in soil, thereby guiding better soil management decisions. Finally, we highlight future research trends, suggesting that the advancement of in situ detection methods is crucial for establishing the precise contribution of abiotic ROS processes to global soil carbon and nutrient models.

Soil Systems doi: 10.3390/soilsystems10050051

Authors: Fatma Karaouli Mongi Ben Zaied Nadia Khelif Zaineb Ali Fethi Abdelli Houda Besser Latifa Dhaouedi Mohamed Ouessar

Soil erosion is a significant environmental concern in arid regions, particularly in dam-regulated watersheds, where intermittent flows from sprinkler irrigation can exacerbate land degradation. This study assesses soil erosion susceptibility in the Sidi Aich watershed using a combined approach of the Revised Universal Soil Loss Equation (RUSLE) and the Analytic Hierarchy Process (AHP), enabling the integration of both regional characteristics and expert-driven weighting. The RUSLE model accounts for natural and human-induced factors, whereas AHP provides a hierarchical weighting system that highlights rainfall erosivity and the local impacts of dam-regulated discharges. Results show that 26.12% of the area falls into the very high susceptibility category, 25.45% into high, 23.91% into moderate, and 24.51% into low susceptibility. Model validation demonstrates satisfactory predictive performance, with Area Under the Curve (AUC) values of 0.85 for AHP and 0.78 for RUSLE. Overall, the findings emphasize the critical role of dam-controlled releases in increasing soil vulnerability, a factor that may not be fully captured when using RUSLE alone. By combining RUSLE and AHP, this research provides a more realistic and regionally tailored assessment of erosion risk, offering valuable guidance for watershed management and erosion mitigation strategies in arid environments.

Soil Systems doi: 10.3390/soilsystems10050050

Authors: Talita Dantas Pedrosa Rafael Oliveira Batista Solange Aparecida Goularte Dombroski José Francismar de Medeiros Stefeson Bezerra de Melo Rafael Rodolfo de Melo

Aquaculture effluent appears as an alternative for reuse, given its significant generation. However, its use must be reasonable to avoid damage to the environmental quality of the soil. In this context, the objective was to evaluate the chemical changes in Ultisol cultivated with small prickly pear cactus and irrigated with different dilutions of aquaculture effluent in the supply water. The experiment was conducted at the Water Reuse Experimental Unit, located in the Brazilian semi-arid region, Mossoró, RN, Brazil. Planting was carried out in a randomized block design with five treatments and five replications. A small prickly pear cactus was irrigated weekly for 365 days, with the gross water depth determined based on the crop’s evapotranspiration. During the experimental period, the physical-chemical characterization of the effluent dilutions was conducted every 60 days, with initial and final descriptions of the soil in the 0.0–0.20 m and 0.20–0.40 m layers. Additionally, cation exchange capacity and the exchangeable sodium percentage were determined. Multivariate statistical analysis was applied to understand chemical changes in the soil. The dilutions containing a higher proportion of aquaculture effluent in the supply water, primarily consisting of 100% effluent, exhibited the chemical changes in the soil. Using a dilution containing 25% aquaculture effluent in 75% supply water may be the most viable alternative for water supply in prickly pear cactus irrigation, with non-relevant changes in soil chemical characteristics.

Soil Systems doi: 10.3390/soilsystems10040049

Authors: Hamisi J. Tindwa Bal Ram Singh

Soil contamination in Sub-Saharan Africa (SSA) is increasingly driven by rapid industrialization, intensive agriculture, mining activities, and urban expansion, posing significant risks to food safety, ecosystem services, and human livelihoods. Despite the growing scale of the problem, low-cost, locally adaptable remediation technologies are widely available and technically feasible within the region. Organic waste and waste-derived products—such as compost, manure, biochar, vermicompost, digestate, and agro-industrial residues—have emerged as sustainable and cost-effective amendments for the remediation of contaminated soils. These materials can immobilize heavy metals, enhance the microbial degradation of organic pollutants, and improve soil health, making them especially suitable for resource-constrained settings. This review synthesizes the current knowledge on the use of organic waste-based remediation approaches in SSA, highlighting technologies already applied at the laboratory, pilot, and field scales, as well as their effectiveness across different contaminant types. However, despite their demonstrated potential, their widespread adoption remains limited. The primary challenge is not the absence of affordable solutions, but rather the systemic constraints characteristic of many SSA countries, including limited technical capacity, weak policy and regulatory frameworks, low stakeholder awareness, and insufficient financial and institutional support for large-scale implementation. To enable broader uptake, there is a need to strengthen waste segregation and treatment systems, standardize composting and pyrolysis processes, and develop robust regulatory guidelines and certification schemes. Investments in monitoring infrastructure, practitioner training, and knowledge transfer mechanisms will also be critical to translating scientific advances into scalable, field-ready solutions for sustainable soil remediation in SSA.

Soil Systems doi: 10.3390/soilsystems10040048

Authors: Marina Quiroga Julia L. Bazzani Roberto S. Martínez Anahí Domínguez José C. Bedano

Earthworms are ecosystem engineers that are sensitive to land-use intensification and edaphic conditions, yet their ecology remains poorly understood in transformed semi-arid landscapes. We hypothesized that, in recently colonized agroecosystems, land-use intensity and physicochemical soil conditions jointly filter the earthworm assembly. In the recently irrigated Lower Valley of the Negro River, Patagonia, Argentina, we sampled earthworms and soils across five land uses—riparian reference sites, fruit orchards, pastures, cereal crops, and horticulture plots—in landscapes dominated by Natrargid Ustolls and Fluventic Haplocambids. We found five species, all of which were exotic Lumbricidae, including the first Argentine record for Murchieona minuscula, indicating a recent colonization following human-mediated niche construction that created an ecological island. The earthworm abundance and biomass were highest in permanent and semi-permanent uses and were driven primarily by soil moisture, pH, and particulate organic matter. Crucially, our results reveal that land-use intensity filters communities by restricting the initial colonization rather than through local extinctions. These findings confirm that soil properties mediate the impact of land use on earthworm assemblages. The inclusion of pastures and fruit orchards in the rotations favors the earthworm populations that, despite low diversity, enhance soil functioning and contribute to agricultural sustainability in semi-arid irrigated agroecosystems.

Soil Systems doi: 10.3390/soilsystems10040047

Authors: Ebrahim Jahanshiri Eranga M. Wimalasiri Yinan Yu Ranjith B. Mapa

High-resolution soil depth maps are valuable for environmental modelling, yet reliable data remains scarce in the tropics. This study evaluates the feasibility of mapping depth to bedrock (DTB) in Sri Lanka using a legacy dataset (n = 88) and global environmental covariates (n = 247). A robust machine learning workflow was employed—including feature selection, hyperparameter tuning, and a stacked ensemble of four algorithms (Random Forest, XGBoost, Cubist, SVM)—to test the limits of global data for local mapping. Despite rigorous optimization, the final ensemble model achieved a performance of R2 = 0.197 (RMSE = 35.4 cm) under spatial cross-validation. While still modest, this result significantly outperforms existing global products and quantifies the “prediction gap” inherent in using ~1 km resolution global covariates to model micro-scale soil variability. An initial exploration involved log-transforming the target variable; however, following rigorous testing, the untransformed depth was modelled directly to avoid bias in back-transformation. A robustness experiment was further conducted, reducing predictors from 24 to 12, which degraded performance, confirming that the model captures complex, physically meaningful climatic interactions rather than fitting noise. The study concludes that while global covariates can capture regional meso-scale trends (explaining ~20% of variance), they are insufficient for resolving local micro-relief (<50 m). The resulting map and uncertainty products provide a critical “baseline” for national planning, but effectively demonstrate that future improvements will require investment in higher-resolution local covariates (e.g., LiDAR) rather than more complex algorithms.

Soil Systems doi: 10.3390/soilsystems10040046

Authors: Ana Carolina De Mattos E. Avila Jackson Adriano Albuquerque Johannes Biala Yash Dang Gunnar Kirchhof

Compost is widely used to improve soil fertility and structure, yet its effects on soil physical properties in Vertosols remain insufficiently documented. This study evaluated the effects of repeat compost application on soil carbon and nitrogen contents and selected soil physical properties in Vertosols from three farms in Queensland, Australia (Roma, Dalby, and Goovigen). Compost had been applied at rates between 5 and 22 Mg ha−1 yr−1 for periods ranging from 3 to 11 years, depending on the site. Intact and disturbed soil samples from the top 0–8 cm were analyzed for bulk density, water retention, hydraulic properties, aggregate stability, and water repellence. Aggregate stability was assessed using laser diffraction before and after ultrasonic dispersion. Compost application significantly increased total carbon and nitrogen contents at all sites (p ≤ 0.01), although effects on soil physical properties varied by site. In Dalby, compost improved water retention and aggregate stability; in Goovigen, it resulted in lower Disaggregation Ratios. Compost did not induce soil water repellence at any site. The results indicate that compost amendments improve soil carbon and nitrogen concentrations and can modify soil physical properties in Vertosols, although responses depend on site conditions and management history.

Soil Systems doi: 10.3390/soilsystems10040045

Authors: Kendall Mackin Sarah L. Strauss Yang Lin Diego Arruda Huggins de Sá Leitão Marcio R. Nunes Gabriel Maltais-Landry

Soil enzyme activities are sensitive biochemical indicators that could benefit soil health assessments, especially in coarse-textured soils. Current protocols are inconsistent for fluorimetric assays and an optimized assay would facilitate comparisons of activities across climates and soils. A factorial experiment was conducted to evaluate how assay conditions affect the activity of three enzymes (acid phosphatase, β-glucosidase, and N-acetyl-β-glucosaminidase) across seven Florida mineral soils (>89% sand) by crossing two temperatures, four pH values, and two reaction termination reagents. Results between microplate fluorimetry and benchtop colorimetry and between air-dried and frozen (−80 °C) soils were also compared. For these soils, a pH of 4.5 with sodium hydroxide termination and a temperature of 25 °C were deemed “optimal” for maximizing activities and maintaining consistent trends. Activities measured with benchtop colorimetry and microplate fluorimetry were related for each enzyme (R2 range: 0.58–0.83) and activities from air-dried soils were 50–90% of those from frozen soils (R2 range: 0.75–0.91). Enzyme activities were positively correlated with other indicators (total C, nutrients), supporting their use in soil health assessments. As the rankings of soil samples by highest enzyme activities were similar regardless of protocol variations, this suggests that inherent soil properties were the dominant drivers of enzymatic activity.

Soil Systems doi: 10.3390/soilsystems10030044

Authors: Miguel Ángel Sánchez-Sánchez Alfonso Albacete

Climate change brings about changes in precipitation and temperatures, significantly increasing aridity in many areas. The southeast of the Iberian Peninsula is affected by climate change and increased aridity, which, together with anthropogenic factors, has increased the area affected by erosion. It is interesting to learn about aspects of aridity, desertification, and erosion in the southeast of the Iberian Peninsula. A literature review was conducted on issues related to climate change, aridity, desertification, and erosion, focusing on the southeast of the peninsula. In addition, field visits were made to verify some of the situations described in the literature. The results highlight the relationships among climate change, aridity, desertification, and erosion, and illustrate their impacts on the landscape and territory of the southeastern Iberian Peninsula. Furthermore, the results indicated a clear anthropogenic influence on the aridity–desertification–erosion loop. There has been a notable and rapid increase in erosion and aridification. Aridity is closely linked to erosion, and its harmful effects on soils in the southeastern Iberian Peninsula have intensified significantly.

Soil Systems doi: 10.3390/soilsystems10030043

Authors: Roberta Pastorelli Alessandra Lagomarsino Chiara Ferronato Arturo Fabiani Sara Del Duca Stefano Mocali Livia Vittori Antisari Gilmo Vianello

In permanently submerged coastal wetlands, interactions between biogeochemical processes and microbial communities strongly influence greenhouse gas (GHG) fluxes. To improve our understanding of how redox-driven processes shape GHG dynamics in these ecosystems, we investigated the relationships among iron (Fe) pools, microbial dynamics, and the potential GHG production in subaqueous soils from an interdunal wetland in San Vitale Park (Italy), permanently submerged and affected by seasonal oscillations of the saline water table. Two subaqueous soil columns (WAS-2 and WAS-4), collected from similar settings, were analyzed. Surface layers of WAS-4 showed higher salinity and carbonate content, whereas WAS-2 was characterized by overall higher Fe concentrations. Distinct vertical distributions of organic matter and sulfur (S) were shown along depth. Laboratory incubations revealed that nitrous oxide (N2O) production was up to ten times higher in WAS-2 than in WAS-4, with peaks in the top 13–14 cm, consistent with more active nitrification-denitrification in surface layers. Methane (CH4) and carbon dioxide (CO2) fluxes decreased with depth, reflecting reduced availability of labile carbon. Methanomicrobiales dominated CH4-producing layers, indicating hydrogenotrophic methanogenesis, while amoA-carrying Nitrosomonadales and Thaumarchaeota, occurred in shallow, organic-rich layers where ammonia supported nitrification and denitrification. Denitrifiers mainly belonged to α- and β-Proteobacteria, consistent with their direct contribution to N2O peaks. Spearman’s correlations showed N2O positively correlated to sulfur and labile carbon (C), supporting denitrification under moderately reducing conditions. CH4 and CO2 positively correlated with organic C (Corg), total nitrogen (TN), and reactive Fe forms, reflecting redox-mediated microbial respiration and methanogenesis. Trace elements (B, Cr, Cu, Ni) acted as micronutrients or inhibitors depending on concentration. Canonical correspondence analysis indicated depth-structured links among gas fluxes, soil chemistry (Corg, TN, S/C, CaCO3, P), and microbial distributions: surface layers, rich in labile C and nutrients, supported active bacteria and archaea involved in decomposition, nitrification, and denitrification, whereas deeper layers hosted oligotrophic archaea adapted to inorganic substrates. Overall, Fe pools appeared to be associated with soil processes relevant to GHG dynamics, although the extent of their regulatory role remains uncertain due to potential alterations of redox-sensitive Fe fractions during sample handling. These results contribute to broader efforts to predict GHG emissions in submerged wetland soils by linking redox stratification, inorganic chemistry, and microbial functional groups.

Soil Systems doi: 10.3390/soilsystems10030042

Authors: Ana Méndez Patricia Almendros Jorge Paz-Ferreiro Gabriel Gascó

Micronutrient addition to soil is crucial for improving crop yield. Within the framework of the circular economy, it is necessary to seek more efficient fertilizers. This would reduce fertilizer consumption while serving as a strategy to mitigate the negative effects of climate change. This study proposes the combined use of a traditional source of a Zn fertilizer (ZnSO4) together with wood biochar to improve lettuce (Lactuca sativa L.) crop yield. An experiment was designed in which a dose of 8 mg Zn kg−1 as ZnSO4·7H2O was added to Cambisol soil, mixed with or without biochar (5%), for lettuce growth. Among other soil properties, Zn bioavailability, microbial biomass, and available water were monitored in the soil, while photosynthetic pigments, Zn content, and biomass production were determined in plants. All treatments increased plant biomass production. Biochar treatments (biochar and biochar/ZnSO4) increased fresh biomass by 324%, while ZnSO4 addition resulted in a 158% increase in lettuce yield. This can be due to several factors, such as biochar being a C source, the improvement of soil water content after biochar addition, and the increase in Zn leaf content in all treatments with respect to the control soil. All of these likely had a positive effect on photosynthesis. This is corroborated by the increase in total chlorophyll, chlorophyll, and carotenoids in the treatments with ZnSO4, biochar/ZnSO4, and biochar. The application of biochar alone increased this property by more than 168%, with a positive impact on soil quality. Our research demonstrates that it is possible, in some cases, to prepare fertilizers combining ZnSO4 and biochar, leading to increased plant Zn uptake and improved crop yield.

Soil Systems doi: 10.3390/soilsystems10030041

Authors: Rômulo José Alencar Sobrinho José Odair da Silva Lívia da Silva Santos Fabrício do Carmo Farias Alessandra Noelly Reis Lima Nelson Ken Narusawa Nakakoji Daniel De Bortoli Teixeira Rose Luiza Moraes Tavares Gener Tadeu Pereira Daniel Pereira Pinheiro João Fernandes da Silva-Júnior

Predictive Digital Soil Mapping (PDSM) in Eastern Amazonia faces challenges due to its environmental complexity, difficult access, and scarce legacy data. While legacy soil maps contain valuable tacit knowledge, updating them requires methods that can handle uncertainty. This study evaluates the integration of old soil maps with machine learning to update soil information in Tracuateua, Pará, with a specific focus on the performance of ensemble learning and the explicit incorporation of uncertainty metrics in soil mapping units under hydromorphic influence, which, in addition to being difficult to access, are influenced by complex pedogenetic processes. We combined 270 sampling points, equivalent to the total pixels that captured the variability of soil mapping units, with environmental covariates and historical data. Several algorithms were tested, including an ensemble approach, to predict mapping units and quantify uncertainty through entropy and confusion indices. The ensemble model demonstrated improved stability and reduced classification uncertainty compared to single models, particularly in challenging hydromorphic environments. Although accuracy gains were modest, the models captured soil–environment relationships, with climate as: Annual Mean Temperature 22,000 years ago (Tmean_22k), relief: Channel Network Base Level (CNBL and altitude) and organism variables: Land Surface Temperature (LST) emerging as the main predictors. Spatialized uncertainty estimates, expressed through entropy and the confusion index, provide a practical decision-support tool for guiding field surveys and identifying areas of low mapping reliability. By explicitly transferring the pedologist’s mental model—encoded as tacit knowledge in legacy soil maps—into ensemble learning, this study presents a robust and transferable framework for updating soil maps in data-scarce tropical regions, balancing predictive performance, spatial consistency, and uncertainty-aware interpretation.

Soil Systems doi: 10.3390/soilsystems10030040

Authors: Payton B. Davis Dara M. Park Brook T. Russell Debabrata Sahoo

Integrating cover crops (CCs) into crop rotations has gained interest in the Southeastern United States due to the benefits that CCs offer, which improve soil health for agricultural production. However, more information is needed on how CCs may affect the development of soil water repellency (SWR), which can negatively impact soil hydrology. The development of SWR threatens crop yields, food security, and farmer livelihoods. To address this knowledge gap, a field experiment measured the water repellency (WR) of four common CC species and a fallow treatment. CC samples were oven-dried, ground, and analyzed for WR using the water drop penetration time (WDPT) test. The mean WDPTs of the CC residues collected at termination and four weeks post-termination ranged from 49 to 4174 and 8 to 2627 s, respectively. Large WDPTs (>5 s) indicate that CC residues can potentially influence the development of SWR. All CC residues exhibited WR. The results suggest that farmers may need to consider alternative CC species depending on when they plant their cash crops in relation to CC termination. Considering the effects of CCs on SWR will enable farmers to make informed management decisions to mitigate SWR development and maintain soil health in a changing climate.

Soil Systems doi: 10.3390/soilsystems10030039

Authors: Qi Liu Guodong Fang Naichi Zhang Chenhao Pei Song Wu Min Yang Jie Shen Kai Yu Xuezheng Shi Weixia Sun Jie Liu Cun Liu Yujun Wang

Comprehensive soil surveys necessitate the integration of multidimensional pedological information, ranging from the morphological delineation of horizons and the taxonomic identification of soil groups to the quantitative assessment of soil organic matter (SOM). These attributes collectively constitute the basis for interpreting pedogenesis and guiding sustainable soil management. However, conventional methods are limited by the subjectivity of expert judgment for horizon and soil group identification, and the time-consuming nature of laboratory analyses for SOM quantification. We developed a novel multimodal deep learning framework based on an improved Mask R-CNN architecture that integrates soil profile images with auxiliary soil property data to concurrently delineate soil horizons, classify soil groups, and quantify SOM. The model was trained on high-resolution soil profile images from 451 soil survey sampling sites spanning ten soil groups across Anhui Province, China. Data augmentation and transfer learning with pre-training on large general image datasets were employed to address the dataset size limitations and improve model generalization. In addition to accurately delineating master horizons, we evaluated three schemes for classifying transitional horizons, which are often ambiguously determined by expert assessments: (i) assigning the transitional horizon to one adjacent master horizon; (ii) assigning it to both neighboring master horizons as an overlapping section; and (iii) treating the transitional horizon as an independent layer. Scheme (iii) achieved the best overall performance, e.g., horizon delineation with accuracy = 0.925, recall = 0.933, F1-score = 0.929, and segmentation mean average precision (seg-mAP) = 0.918, soil group classification accuracy = 0.717 and prediction of SOM with R2 = 0.565. These results demonstrate that treating transitional horizons as independent layers yields superior segmentation. Consequently, this integrated framework provides a robust, automated solution for high-throughput soil resource assessment.

Soil Systems doi: 10.3390/soilsystems10030038

Authors: Fatma Mekki Nissaf Karbout Habib Lamourou Houda Oueriemmi Ali Bennour Mohamed Moussa Mohamed Ouessar

Climate change and soil degradation threaten agricultural sustainability in arid oases, where water and nutrient limitations constrain crop production. In Tunisia, date palm residues are abundant but frequently burned despite their potential as soil amendme. This study assessed the effects of date palm waste biochar (B; 10 t ha−1), mineral fertilizers (NPK), and their combination as enriched biochar (BNPK) on soil fertility, including total organic carbon (TOC) and total nitrogen (TN), as well as barley (Hordeum vulgare L.) yield over two consecutive cropping seasons (2023–2024) using a randomized complete block design with three replications. During 2024, B increased TOC to 0.5% (control: 0.18%), while NPK enhanced TN to 0.037% in 2023; however, in 2024, nitrogen levels returned to values comparable to the control condition (0.017%). BNPK combined these beneficial improvements, maintained them in 2024, and resulted in a C/N ratio of 16.7 (control: 9.6), reflecting the most favorable balance between soil carbon accumulation and nitrogen retention. Grain yield increased by 21% (B), 80% (NPK), and 79% (BNPK) relative to the control (3.12 t ha−1), while BNPK reduced soluble sugars in grains (fructose 100%), glucose 86% (control: 0.09, 0.014) and increased grain nitrogen content to 1.80% (control: 0.74). Principal component analysis revealed a clear separation among treatments, with BNPK strongly associated with improved soil fertility, grain yield, and grain quality. These results demonstrate that integrating biochar with nutrient management enhances soil fertility and supports sustainable agriculture in arid oasis agroecosystems.

Soil Systems doi: 10.3390/soilsystems10030037

Authors: Mohammad Wasif Amin Naveedullah Sediqui Shafiqullah Aryan Safiullah Habibi Khalid Joya Atsushi Sanada Shinji Suzuki Irie Kenji Machito Mihara

Drought reduces soil moisture and impairs root function, posing a significant threat to rice production in arid regions. The influence of soil amendments on early rice root development under semi-dry cultivation remains insufficiently characterized, especially when assessed using non-destructive rhizotron techniques. This study employed a scanner-based rhizotron system to evaluate early root responses of rice seedlings to six amendments under semi-dry irrigation: vermicompost and peat moss, spirulina powder, gypsum, rice husk biochar, zeolite, and an unamended control. The vermicompost plus peat moss (VC+PM) treatment demonstrated the highest water-holding capacity (26%), root projected area (9.60 cm2 plant−1), and root surface area (84.79 cm2 plant−1). VC+PM also promoted extensive lateral branching (233 secondary and 1709 tertiary roots) and the greatest total lateral root length (363.09 cm plant−1), resulting in superior biomass (shoot: 140.00 mg plant−1; root: 56.70 mg plant−1) and the lowest root-to-shoot ratio (0.90). These improvements are attributed to the enhanced moisture retention of peat moss and the nutrient and phytohormone contributions of vermicompost. In contrast, rice husk biochar exhibited the lowest water-holding capacity (14%), while other amendments produced moderate or limited effects. The results establish a direct relationship between improved soil water retention and early-stage drought-avoidant root development. The combination of VC and PM emerges as a promising approach to enhance root plasticity and seedling establishment in water-saving rice systems. As this study was conducted under controlled rhizotron conditions and limited to the seedling stage (20 days after sowing), future research should prioritize multi-season field trials to assess yield translation and economic feasibility assessments to support farmer adoption.

Soil Systems doi: 10.3390/soilsystems10030036

Authors: Julián Ramos Nestor Bonomo Claudio García Andrés Quincke

Agricultural systems are under growing pressure, as soil degradation threatens food security and sustainable land use. Early detection through soil monitoring and precision agriculture is vital to prevent irreversible damage and enable timely conservation. This study evaluates a combined procedure based on electrical resistivity tomography and frequency-domain electromagnetic induction measurements, together with discrete soil sampling, to electrically characterize the soil, identify layers, and map the A horizon depth in a non-disturbing way. This work includes the design and implementation of a mounting electrode system, which reduces the installation time of electrical resistivity tomography surveys by 60% while maintaining data quality. The data were acquired in the oldest long-term agronomic experiment in South America, comprising seven rotation systems with three replicates each, totaling 21 rainfed plots, and representing contrasting management scenarios. Soil A horizon thickness maps of the entire experiment were obtained through two procedures. A comparison between mapping inputs, including all plots and only bare-soil plots, revealed minimal differences in unvegetated areas but notable discrepancies under plant cover, where vegetation increased fluctuations and noise. The present study provides a methodology for accurately assessing the spatial variability of the A horizon thickness by means of proximal sensing techniques. This contributes to the challenge of gathering fundamental soil information in a fast and cost-effective manner, critical for precision agricultura.

Soil Systems doi: 10.3390/soilsystems10030035

Authors: Sara Mavsar Helena Grčman Rok Mihelič

Soil texture-dependent responses and time-scales of soil quality change, especially soil carbon, remain poorly understood. We addressed this gap using a dual time-scale design of long-term field experiments: 11 years of minimum (MT) versus ploughing tillage (CT), both followed by 5-year transitions to no-till (NT) in contrasting textures (loamy vs. silty clay) in NE Slovenia. In loamy soils, reduced tillage in the 0–10 cm layer increased soil organic carbon by 40–48%, dissolved organic carbon by 36–64%, permanganate oxidizable carbon by 67–84%, particulate organic carbon by 76–95%, and mineral-associated organic carbon (MAOC < 50 μm) by 28–34%. In silty clay soils, high clay content masked tillage effects, though labile pools showed stratification. MAOC < 20 μm remained stable across treatments and textures (2.0–2.5%), except under CT in loamy soil (1.73%), indicating enhanced decomposition. In loamy soils CT increased by 0.5–1 and 1–2 mm and decreased >20 mm and in silty clay soils increased <0.5, 1–2 and 2–4 mm aggregate formations. The MWD, GMD, Dm indices correlated strongly with C fractions, confirming physical protection mechanisms. Our dual time-scale approach reveals labile C pools and aggregate recovery respond within 5 years of NT, while texture modulates response magnitude and detectability.

Soil Systems doi: 10.3390/soilsystems10020034

Authors: Suah Yekeh Ashaki A. Rouff

Soils in seven urban parks in Newark, New Jersey (NJ), United States, were evaluated for arsenic (As) and lead (Pb) by field and laboratory methods. Surface (S1, 0–3 cm) and near-surface (S2, 4–7 cm) soils in high-contact areas of the parks were analyzed by portable X-ray fluorescence (XRF) spectroscopy. Median concentrations of As and Pb in S1 profiles were higher than median concentrations in NJ Urban soils. In S1 and S2 profiles, 39–50% of As and 56–58% of Pb concentrations exceeded the NJ Department of Environmental Protection limits for residential soils, with most hotspots located in two of the seven parks. The contamination factor (CFAs = 1.5–4.3; CFPb = 1.7–9.8), enrichment factor (EFAs = 1.7–4.6; EFPb = 2.0–10.4), and geoaccumulation index (Igeo As = −0.1–1.5; Igeo Pb = 0.1–2.7), calculated relative to NJ Rural soil concentrations, confirmed the contamination of park soils with As and Pb, with higher contamination and enrichment indices for Pb. Tessier sequential extraction indicated the metals were mostly in the reducible fraction, with median values of 80% As and 65% Pb bound to iron and manganese oxides. The fractionation suggests limited environmental mobility of the metals under current soil conditions. However, human exposure to As and Pb remains a concern as the soils are located in high-contact recreational areas.

Soil Systems doi: 10.3390/soilsystems10020033

Authors: Evanna McGuinness Abraham J. Gibson Joanne Oakes Mark Farrell Naomi S. Wells

Subsoil (30–100 cm) soil organic carbon (SOC) is a poorly constrained but potentially significant component of terrestrial carbon budgets. While controls on subsoil SOC are likely to differ from those affecting topsoil, few studies have quantified them. This study quantified subsoil (30–100 cm) SOC stocks and identified the controls on its spatial distribution across perennial grazing systems in northeast New South Wales, Australia. SOC was measured to 1 m depth across 54 long-term perennial pasture grazing paddocks on nine farms. A Random Forest regression model was then used to determine the relationship between subsoil SOC and drivers represented by the scorpan model of soil formation. Subsoil SOC contributed ~50% of total SOC stocks in the top metre of soil, with a median of 65.8 t ha−1 stored in subsoil. Our study found that drivers of SOC input and turnover (subsoil total nitrogen, 10–30 cm SOC content, and climate), as well as pedogenic processes influencing SOC stabilisation (weathering index), were the most important factors in the determination of subsoil SOC content. This contrasts with previous findings where abiotic factors linked to parent material and soil properties were the major controls on subsoil SOC distribution and highlights links between both input and stabilisation in perennial grazing systems.

Soil Systems doi: 10.3390/soilsystems10020032

Authors: Fujun Liu Hangyu Zhang Jianhui Zeng Zhonglu Guo

Soil erosion and deposition processes act as key drivers of soil resources distribution across landscapes, affecting soil quality and functionality. However, the impacts of long-term soil erosion on soil quality and degradation in the black soil region remain unclear. Here, we assessed soil quality and degradation as a consequence of historical erosion and soil redistribution in an agricultural catchment in Northeast China. Soil quality indices (SQI) were calculated using both linear and non-linear scoring function methods, along with soil indicator selection approaches, including Total Data Set (TDS) and Minimum Data Set (MDS). Soil degradation indices (SDI), resistance indices (SRI), and the change of SQI (CSQI) were computed and compared. The mean SDI for bulk density (BD) and sand was greater than 0. When BD and sand were excluded, the mean SDI and SRI for the 0–10 cm and 10–20 cm soil layers were −29.8% and −21.9%, and 0.57 and 0.65, respectively. Surface soil (0–10 cm) organic matter (SOM), available potassium (AK), structure stability index (SSI), and total nitrogen (TN) in eroding sites, as well as AK, SSI, SOM, TN, and available phosphorus (AP) in depositional sites, are particularly sensitive to long-term erosion. Field capacity, sand, AK, and SSI were selected to develop the SQI, with the non-linear method utilizing MDS outperforming other SQIs. Most SQIs in eroding sites were lower than those in depositional sites and increased with higher soil redistribution rates. The assessment of soil degradation using SDI, SRI, and CSQI revealed that long-term erosion markedly diminished soil quality, although deposition somewhat alleviated this impact. The lower SQI in the 10–20 cm compared to the 0–10 cm soil layer was primarily attributed to decreased FC, while long-term erosion degraded soil quality by negatively affecting AK and sand content. These findings enhance our comprehension of soil degradation caused by erosion in the Mollisol region of Northeast China.

Soil Systems doi: 10.3390/soilsystems10020031

Authors: Dmitry S. Volkov Olga B. Rogova Svetlana T. Ovseyenko Mikhail A. Proskurnin

The distribution of water-soluble organic matter (or dissolved organic matter DOM) in narrow (nano-and micrometer) fractions of chernozem was studied by sequential filtration on track-etched membranes. Multimodal (IR and fluorescence) two-dimensional correlation (2D-COS) spectroscopy was used. Protocols for attenuated total reflectance (ATR) FTIR of DOM were proposed. ATR-FTIR 2D-COS provides a larger volume of information on characteristic bands compared to traditional FTIR, especially in C–H ranges (3000–2800 and 1450–1300 cm−1). The fluorescence excitation–emission matrix 2D-COS showed that the indexes and ratios of humic- to protein-like compounds are reproducible, and exhibit significant variation among size fractions, with maximum amounts of saturated humic-like compounds in the largest (2–10 μm) and finest fractions (0.01–0.03 μm), while medium fractions (0.05–1 μm) are dominated by fulvic acids and fresh organic matter. Heterospectral fluorescence–IR 2D-COS enhanced the accuracy of identification and assessment of DOM group composition and showed that C–H IR band intensities correlate with tyrosine-like EEM bands and biogenic fluorescence indexes, while carboxylic components have humate-like bands and humification fluorescence indexes. Element profiles in DOM fractions correlate with fluorescence indexes; humification indexes with P, S, Cr, Mg, Ca, Cu, and Zn; biogenic with Mg, P, Cr, Cd, K, S, and Ca.

Soil Systems doi: 10.3390/soilsystems10020030

Authors: Hongbiao Cui Zhanlong Liu Binglu Bao Lijun Zhou Shiwen Zhang Jun Zhou

Soil cadmium (Cd) pollution poses a significant threat to rice production and food safety. Although lime amendment is known to reduce Cd bioavailability in soils, the optimal growth stage for its application remains unclear. This study employed pot experiments with the rice cultivar Wuyouhuazhan as the test material to investigate the effects of lime (Ca(OH)2) application during four critical rice growth stages, namely seedling (LS), tillering (LT), booting (LB), and filling (LF), on Cd availability, soil properties, and Cd accumulation in rice. Results showed that lime application at all stages significantly reduced soil-available Cd by 53–63%, primarily by promoting the transformation of exchangeable Cd into more stable residual forms. Lime also increased biomass across rice tissues by 1–153%, with the most pronounced effects observed when applied at the seedling stage. Following lime application at different stages, Cd concentrations in all rice tissues showed a decreasing trend. Compared to CK (without lime application), Cd concentrations decreased by 2–26% in roots, 33–80% in stems, and 8–62% in grains. Among the treatments, LS was the most effective in reducing Cd levels, while LT, LB, and LF exhibited progressively weaker reductions. Structural equation modeling indicated that soil pH and stem Cd concentrations were key factors influencing grain Cd accumulation. These findings demonstrate that lime application at the early seedling stage is most effective in mitigating Cd uptake by rice, providing a practical strategy for safe rice production in Cd-contaminated soils.

Soil Systems doi: 10.3390/soilsystems10020029

Authors: Gabriele Buttafuoco Carmela Riefolo Massimo Conforti Annamaria Castrignanò

This study aimed to evaluate the effectiveness of spectral absorption-feature indices, derived from soil hyperspectral diffuse reflectance spectroscopy, as covariates within a multivariate geostatistical framework to enhance the digital mapping of soil organic carbon (SOC). The approach also incorporated exhaustively measured auxiliary variables derived from topographic and textural attributes. The research was conducted in a 1.39-km2 forested catchment, where 135 topsoil samples (0–0.20 m depth) were collected from soils classified as Typic Xerumbrepts and Ultic Haploxeralfs. All samples were analyzed for SOC concentration, soil texture, and diffuse reflectance spectra across the VIS–NIR–SWIR region (350–2500 nm). The continuum-removal technique was applied to compute radiometric indices associated with absorption features in the visible region and at 1400, 1900, and 2200 nm. Results demonstrated that these indices effectively captured the SOC spatial variability when combined with silt fraction and topographic attributes, which, among the other covariates, actually exhibited the strongest spatial relationships with SOC. Compared to univariate ordinary kriging, the multivariate geostatistical approach yielded improved prediction accuracy in cross-validation, mostly due to the use of hyperspectral indices as auxiliary variables. Moreover, the geostatistical analysis revealed that the multivariate frame of spatial association was characterized by two distinct spatial scales. The findings of this work then support the use of hyperspectral indices as valuable covariates for digital modelling of SOC distribution even in landscapes characterized by heterogeneous topography and pedology.

Soil Systems doi: 10.3390/soilsystems10020028

Authors: Masoud M. Ardestani Kateřina Čápová Filip Křivohlavý Adnan Mustafa Zdeněk Nesvadba Jan Frouz

While the effect of domestication on various aspects of plant ecophysiology has been studied, less is known about its effect on plant–soil interaction. Here, we studied three botanical species of barley in comparison with four old cultivars and four contemporary cultivars with bare soils and two perennial grasses. Aboveground and belowground biomass decreased from botanical species to old cultivars and contemporary cultivars. Aboveground biomass of all barley cultivars was about one third lower in mineral fertilizer compared to the organic one, and this difference was similar in all barley cultivars. Biomass of perennial grasses was up to one third of barley biomass, but grass biomass did not differ significantly between fertilization treatments. Belowground biomass of botanical barley is significantly higher than that of modern cultivars; this discrepancy is even more pronounced under mineral fertilizer where belowground biomass of botanical barley significantly increased, and that of modern cultivars significantly decreased in comparison with organic fertilizer treatment, which means that modern barley cultivar in combination with mineral fertilizers provides less belowground litter to soil. This in the long term can potentially, together with other factors, contribute to the depletion of cultivated soil for organic matter. Microbial respiration in soil did not differ between treatments supplied by organic fertilizer, while in mineral fertilizer treatments old cultivars had lower respiration than other treatments. Microbial biomass did not differ between treatments supplied by mineral fertilizer, but in treatments supported by organic fertilizer, perennial grasses supported more microbial biomass than all barley treatments. The same pattern was observed in C content in soil. Carbon distribution in individual soil fractions did not differ between perennial grasses and barley treatments. In general, when hotspots of organic matter were provided, plants transferred this organic matter to soil, and this activity was more pronounced in perennial grasses than in barley treatments.

Soil Systems doi: 10.3390/soilsystems10020027

Authors: Shimbahri Mesfin Mitiku Haile Girmay Gebresamuel Amanuel Zenebe Abera Gebre Okubay Giday Adhanom Lars Olav Eik Bal Ram Singh

Improving crop productivity largely depends on understanding soil fertility constraints and the effects of nutrient management on yield performance. Accurate determination of existing soil nutrient status and targeted application of limiting nutrients are essential for enhancing wheat (Triticum spp.) productivity. However, the specific effects of omitting one of the macronutrients such as nitrogen (N), phosphorus (P), or potassium (K) on wheat yield have not been investigated in the target area. This study employed the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model to estimate the N, P, and K fertilizer requirements needed to achieve a predefined wheat yield target. The objectives were to: (i) evaluate yield responses to complete versus nutrient omission (N, P, or K) fertilization treatments, and (ii) analyze corresponding nutrient uptake and use efficiency dynamics. The experimental treatments included: (1) full NPK fertilization, (2) NP only (K omitted), (3) NK only (P omitted), (4) PK only (N omitted), and (5) an unfertilized control. Topsoil samples were analyzed and used as inputs for the QUEFTS model. Yield and agronomic data, as well as nutrient uptake and use efficiency, were measured. Model performance was validated using standard statistical metrics. Results showed that full NPK application significantly (p < 0.05) improved yield, yield components, and nutrient uptake compared to omission treatments and the control. The strong agreement between QUEFTS-predicted and observed yields highlights the model’s potential as a reliable, cost-effective decision-support tool for optimizing site-specific fertilizer recommendations. These findings demonstrate that balanced NPK fertilization markedly boosts wheat yield and nutrient uptake, while the QUEFTS model provides a powerful, reliable tool for tailoring fertilizer management to local soil conditions.

Soil Systems doi: 10.3390/soilsystems10020026

Authors: Zainulabdeen Kh. Al-Musawi Agampodi Gihan S. D. De Silva Jabir Ali Abdinoor László Bede Dávid Stencinger Bálint Horváth Sándor Zsebő Áron Licskai Gergő Hegedüs Viktória Vona Gyula Pinke Bahar Makbule Temeltürk Emőke Ruzsics István Mihály Kulmány

Agriculture must balance productivity with greenhouse gas emissions, biodiversity, and resource concerns. This study examined how tillage (conventional, CT; minimum, MT), nitrogen fertilisation (0–221 kg N ha−1), and herbicide rates (0–100%) interactively affected soil CO2 emissions, vegetation vigour, and weed diversity in maize production during 2022. A factorial experiment was conducted on a 1 ha with 40 plots monitored soil temperature, moisture, penetration resistance, normalised difference vegetation index (NDVI), weed diversity (Simpson’s Index), and CO2 emissions (closed-chamber method). Minimum tillage increased soil water retention (9.3 ± 6.5% vs. 5.4 ± 4.3%), soil temperature (28.0 ± 1.5), and compaction (0.6 ± 0.3 vs. 0.1 ± 0.0 MPa), while enhancing weed diversity (0.53–0.80 vs. 0.38–0.67). MT produced higher CO2 emissions than CT, especially at 147 kg N ha−1 (49.9 ± 15.7 vs. 29.1 ± 11.6 μmol m−2 s−1), peaking under MT-147 kg N ha−1-H75 (79.4 ± 1.2 μmol m−2 s−1). NDVI responses varied between tillage systems; under CT, vegetation vigour peaked at 75% herbicide application, while under MT vegetation was more responsive to nitrogen and more sensitive to herbicide, highlighting nitrogen × herbicide interaction trade-offs. Overall, MT enhanced water conservation and weed diversity but increased short-term CO2 emissions. This study reports first-year, site-specific results from an ongoing multi-year field experiment; therefore, the findings were interpreted as short-term, season-specific responses. This highlights the need for site-specific, climate-smart management that integrates emissions, soil health, biodiversity, and productivity.

Soil Systems doi: 10.3390/soilsystems10020025

Authors: Olga B. Rogova Dmitry S. Volkov Mikhail A. Proskurnin

FTIR spectroscopy, attenuated total reflection (ATR), and diffuse reflectance (DRIFT) modalities, along with ICP–AES spectroscopy and correlation analysis, including two-dimensional correlation spectroscopy (2DCOS), were used for the detailed analysis of Kastanozem (chestnut) soils. Microaggregates (20–200 μm) and macroaggregates (200–1000 μm) of characteristic horizons of uncultivated (fallow) and cultivated (arable land) chestnut soils of the same origin were physically fractionated by wet sieving. The combination of these molecular and atomic spectroscopy techniques in combination with correlation analysis was able to find direct correlations between matrix-forming anions and soil organic matter (SOM) of Kastanozems. Humic substances were separated from the corresponding soil samples to reveal SOM contributions more explicitly. Microaggregates of the size fractions of 20–40 μm and 40–60 μm bore the most comprehensive information for both techniques used. Most significant differences between land-use Kastanozem samples were observed in topsoil horizons (arable P versus light-colored humic AJ horizon), and for the next pair of horizons along the profile xerometamorphic BMK horizon to structural metamorphic BM horizon. These differences included carbonate matrix and SOM amounts and composition. Topsoil arable land showed significantly smaller amounts of total organic carbon and a decrease in the share of long-chain hydrocarbons compared to fallow, which has a more distinctive character compared to similar land-use samples of Chernozem. An increase in carbonate contents with soil depth was found for both land-use samples, while the amounts and composition of the silicate matrix remained largely unchanged within the depth profile. The heterospectral 2DCOS comparison of FTIR (between horizons and land-use samples), ICP–AES (between land-use samples), and FTIR–AES (for the same sample) showed the possibility of a more reliable attribution of FTIR absorption bands and revealed the differences in the macro- and micro-aggregate elemental and SOM composition of Kastanozems.

Soil Systems doi: 10.3390/soilsystems10020024

Authors: Viacheslav Vasenev Robin van Velthuijsen Marcel R. Hoosbeek Yury Dvornikov Maria V. Korneykova

The development of urban green infrastructures (UGI) is considered among the main nature-based solutions for climate mitigation in cities; however, the role of soils in the carbon (C) balance of UGI ecosystems remains largely overlooked. Urban green spaces are typically dominated by constructed Technosols, created by adding organic materials on top of former natural or agricultural subsoils. The combined effects of land-use history and current UGI management result in a high spatial variation of soil organic carbon (SOC) stocks and soil CO2 emissions. Our study aimed to explore this variation for the case of Wageningen University campus. Developed on a former agricultural land, the campus area includes green spaces dominated by trees, shrubs, lawns, and herbs, with well-documented management practices for each vegetation type. Across the campus area (~32 ha), a random stratified topsoil sampling (n = 90) was conducted to map the spatial variation of topsoil (0–10 cm) SOC stocks. At the key sites (n = 8), representing different vegetation types and time of development (old, intermediate, and recent), SOC profile distribution was analyzed including SOC fractionation in surface and subsequent horizons, as well as the dynamics in soil CO2 emissions, temperature, and moisture. Topsoil SOC contents on campus ranged from 1.1 to 5.5% (95% confidence interval). On average, SOC stocks under trees and shrubs were 10–15% higher than those under lawns and herbs. The highest CO2 emissions were observed from soil under lawns and coincided with a high proportion of labile SOC fraction. Temporal dynamics in soil CO2 emissions were mainly driven by soil temperature, with the strongest relation (R2 = 0.71–0.88) observed for lawns. Extrapolating this relationship to the calendar year and across the campus area using high-resolution remote sensing data on surface temperatures resulted in a map of the CO2 emissions/SOC stocks ratio, used as a spatial proxy for C turnover. Areas dominated by recent and intermediate lawns emerged as hotspots of rapid C turnover, highlighting important differences in the role of various UGI types in the C balance of urban green spaces.

Soil Systems doi: 10.3390/soilsystems10020023

Authors: Yiyi Sulaeman Nana Sutrisna Joko Pramono Lilia Fauziah Ahmad Suriadi Heppy Suci Wulanningtyas Eni Maftu’ah Endang Gati Lestari Anny Mulyani

Sorghum is a strategic crop for food, feed, and bioenergy. However, information on its cultivation area and agronomic profile in Indonesia remains limited. Therefore, this study aimed to identify, characterize, and evaluate sorghum cultivation in different agroecosystems and pedoagroclimatic settings in Indonesia. We surveyed published articles, newspapers, and other digital resources, collating a dataset that contained pedoagroclimatic characteristics. We then conducted a field survey to gather data on sorghum farming practices. The results show that sorghum is planted in 11 agroclimatic zones, mainly in D3, B1, and E4, and in seven soil types, mainly in Inceptisols, Mollisols, Vertisols, and Andisols. The cultivated varieties cover Bioguma 1, Bioguma 2, Bioguma 3, Numbu, Kawali, UPCA-S1, Suri 3 Agritan, Soper 9, and local varieties. Under smallholder farmers’ management, the average sorghum yield ranges from 3.6 to 7.5 Mg ha−1. The 15–68% of the yield gap can be closed by implementing site-specific technologies, including high-yielding varieties and soil management. These findings provide a baseline for supporting efforts to increase sorghum production and develop robust sorghum cultivation technologies.

Soil Systems doi: 10.3390/soilsystems10020022

Authors: Bernard Gagnon Noura Ziadi

The application of forest byproducts to cropland provides significant benefits, mitigating soil degradation, supplying essential nutrients, and increasing yields. Their impact is well known in the first years, but few studies have examined the effects several years after an application. A field study was initiated in Québec, QC, Canada, to assess the effects of wood ash (10 and 20 Mg dry wt. ha−1), pine biochar (10 Mg dry wt. ha−1), paper mill sludge (PS) (12 Mg dry wt. ha−1), and a combination of wood ash and PS, relative to an untreated control and a mineral treatment, on crop yield and soil properties three to seven years after application in a temperate circumneutral loamy soil. The site was cropped to a maize (Zea mays L.)–soybean [Glycine max (L.) Merr.]–spring wheat (Triticum aestivum L.) rotation. Each crop received supplemental N and P from mineral fertilizers, when needed, according to local agronomic recommendations. Applying wood ash increased wheat yield by 0.25–0.44 Mg ha−1 three years after the addition, but no effect was detected in other cases and for the other amendments. Wood ash also resulted in the largest increases (p < 0.05) in soil pH and Mehlich-3 P, K, Ca, Mg, Zn, and Cd, alone or in combination with PS. Pine biochar promoted soil C sequestration after seven years, but did not affect other soil properties owing to its high stability and low nutrient content. This study revealed that wood ash was more advantageous than pine biochar for improving soil quality and crop productivity.

Soil Systems doi: 10.3390/soilsystems10020021

Authors: Md Abdul Halim Md Rezaul Karim Nigel V. Gale Sean C. Thomas

Tea (Camellia sinensis) cultivation is a major global industry that faces sustainability challenges due to soil degradation and greenhouse gas (GHG) emissions from intensive management. Biochar—charcoal designed and used as a soil amendment—has emerged as a potential tool to improve soil health, enhance carbon sequestration, and mitigate GHG fluxes in agroecosystems. However, field-scale evidence of its effects on GHG dynamics in woody crops like tea remains limited, particularly regarding methane (CH4). Here, we present, to our knowledge, the first field assessment of biochar impacts on CO2, CH4, and H2O vapour fluxes in a subtropical tea agroforestry system with and without shade trees in northeastern Bangladesh. Using a closed dynamic chamber and real-time gas analysis, we found that biochar application (at 7.5 t·ha−1) significantly enhanced average soil methane (CH4) uptake by 84%, while soil respiration (CO2 efflux) rose modestly (+18%) and water-vapour fluxes showed a marginal increase. Canopy conditions modulated these effects: biochar strongly enhanced CH4 uptake under both shaded and open canopies, whereas biochar effects on water-vapour flux were detectable only when biochar was combined with a shade-tree canopy. Structural equation modelling suggests that CH4 flux was primarily governed by biochar-induced changes in soil pH, moisture, nutrient status, and temperature, while CO2 and H2O fluxes were shaped by organic matter availability, temperature, and phosphorus dynamics. These findings demonstrate that biochar can promote CH4 uptake and alter soil carbon–water interactions during the dry season in tea plantation systems and support operational biochar use in combination with shade-tree agroforestry.

Soil Systems doi: 10.3390/soilsystems10010020

Authors: Matthias Filipiak Katrin Kuka

Chemical soil properties contribute to the resilience of soil ecosystems. Healthy soils with optimal nutrient levels, balanced pH and good organic matter content are better able to withstand environmental stresses, such as drought, disease or pests. When comparing the chemical soil properties of temperate grassland and arable land, several differences can be observed due to differences in soil cover and management. Grasslands typically sequester more carbon, limit nitrogen leaching, and have lower nitrous oxide emissions and losses of phosphorus due to less soil disturbance and a more closed nutrient cycle. In contrast, arable land has higher nutrient losses through harvest, leaching, gaseous emissions and erosion due to regular tillage, frequent bare phases, and sequesters less carbon, typically due to higher mineralisation rates and lower nutrient returns. Monitoring and managing chemical soil properties, appropriate nutrient management, addition of organic matter such as organic fertilisers, inclusion of grassland phases and catch crops in crop rotations, incorporation of crop residues into the topsoil after harvest and further sustainable agricultural practices are essential to promote soil health. By optimising chemical soil properties, farmers and land managers can improve productivity, conserve natural resources and support the long-term sustainability of the soil ecosystem.

Soil Systems doi: 10.3390/soilsystems10010019

Authors: Marco Aurélio Barbosa Alves Daniela Roberta Borella Frederico Terra de Almeida Adilson Pacheco de Souza Daniel Fonseca de Carvalho

The conversion of native forests into agricultural areas without conservation practices can expose tons of soil organic carbon (SOC) to the atmosphere. This study aimed to evaluate the effect of land use and cover (LULC) on C in regions of the Caiabi (SBC) and Renato (SBR) River sub-basins, located in the Brazilian Cerrado–Amazon transition. Data on physical attributes and SOC were obtained by region (upper, middle, and lower), LULC (cropland, pasture, and native forest), and depth (0–10, 10–20, and 20–40 cm), with five replicates for each variable. The highest SOC values were found in areas with higher clay contents or in areas of native forest or crop residues. In the SBC, there was a negative correlation of SOC with sand and particle density (PD) and a positive correlation with silt. In the SBR, there was a positive correlation between SOC and microporosity and total porosity, and a negative correlation with sand, soil bulk density, and PD. The highest SOC values were found in the SBC upper region, in native forest (107 Mg ha−1), cropland (69 Mg ha−1), and pasture (49 Mg ha−1). In the SBR upper region, the values were highest in pasture and cropland (93 and 58 Mg ha−1), and in the lower region, the values were highest in native forest (48 Mg ha−1). SOC varied in relation to the SBC and SBR regions, the LULC, depth, and physical attributes, especially soil texture.

Soil Systems doi: 10.3390/soilsystems10010018

Authors: Jan Adriaan Reijneveld Nico Rodenburg Marius Heinen Johan Bouma

A recent report on the future of agriculture by the European Commission emphasizes the need for sustainable development on a farm level to be characterized by measuring ecosystem services with indicators and corresponding thresholds. This case study raises the question whether or not operational methods are currently available to allow such measurements under practical field conditions. To broaden the scope of this case study to the international policy arena, the measurement of ecosystem services was linked to selected UN Sustainable Development Goals (SDGs). The case study showed that operational methods are currently available to measure and judge ecosystem services related to the following: the production of healthy food, water quality, greenhouse gas emissions, biodiversity, and soil health. This conclusion was, however, only possible when applying innovative sensing and laboratory techniques to measure pesticide and heavy metal contents and soil microbiology. Soil health is not only important as an ecosystem service, as such, but also plays a major role in realizing the other ecosystem services. Once all ecosystem services are satisfied on a particular farm, a farmer is free to follow his own unique management practices free from top-down governmental rules and regulations that focus now on required management measures. Each farmer can pursue the goals in a way that best aligns with his own vision, context, and creativity.

Soil Systems doi: 10.3390/soilsystems10010017

Authors: Yacine Benhalima Erika S. Santos Diego Arán

This study examined long-term changes in soil carbon stock dynamics 11 and 19 years after fire under different severities at 0–5 and 0–25 cm depths with a digital soil mapping approach. Linear (MLR) and non-linear models (RF, SVR, XGBoost) combined with feature selection methods (r < 0.8, FFS, Boruta) were used to predict bulk density (BD), total C, and C stock. Distributional biases were evaluated with Kolmogorov–Smirnov statistics and corrected by Quantile Mapping (QM). RF-FFS performed best for BD and total C at 0–5, while RF-SVR outperformed for C stock and all properties at 0–25. Total C was 49% higher at 0–5, whereas C stock was 7.57 times greater at 0–25. Both models underestimated variability, especially for C stock. At 0–25, bulk density decreased after fire, particularly under conditions of medium severity, while total C increased following the same tendency. The results showed that fire’s legacy is still present in the ecosystem after one and two decades. This is particularly evident at greater depths, where long-term C stock is lower.

Soil Systems doi: 10.3390/soilsystems10010016

Authors: Lei Song Peifeng Xu Xiaorong Zhang Zongqiang Gong

The surface chemistry of biochar plays a pivotal role in the adsorption and stabilization of soil organic carbon (SOC); however, sorption-mediated mechanisms remain insufficiently understood for biochars derived from invasive plants. In this study, Solanum rostratum biomass, an aggressive invasive weed in northern China, was pyrolyzed at 400–600 °C in 2023 to produce biochars with varying surface functionalities and structural features. FTIR, Raman, XPS, and SEM analyses revealed that increasing pyrolysis temperature led to decreased oxygen-containing functional groups and enhanced aromatic condensation, reflecting a transition from hydrogen bonding to π–π and hydrophobic sorption mechanisms. Soil incubation experiments using sandy loam soil showed that biochar produced at 500 °C significantly increased the stable carbon pool (SCP) to 52.4%, compared to 30.6% in unamended soils. It also reduced cumulative CO2 release from 1.74 mg g−1 to 1.21 mg g−1 soil, indicating improved carbon retention. Bacterial 16S rRNA gene sequencing revealed that biochar amendments significantly altered community composition and increased deterministic assembly, particularly under 500 °C biochar, suggesting a sorption-driven niche filtering effect. These findings demonstrate that S. rostratum-derived biochar, especially at intermediate pyrolysis temperatures, enhances both carbon sequestration and microbial habitat structure. This has direct implications for improving degraded soils in arid farming regions, offering a dual strategy for invasive biomass management and climate-resilient agriculture.

Soil Systems doi: 10.3390/soilsystems10010015

Authors: Zhizhong Li Madjid Hadioui Kevin J. Wilkinson

In soils, it is key to not simply determine the behavior of the major elements but also understand the fate of trace and ultra-trace elements that can often have disproportionate effects on these complex systems. Soils, including agricultural soils, constitute a reservoir of nanoparticles and natural colloids of multiple origins. Nonetheless, only limited information is available on the concentrations and fate of nanoparticles in soils, due largely to the difficulty of distinguishing anthropogenically generated particles from the complex soil matrices in which they are found. Bulk measurements are often unable to quantify the key contributions of trace pollutants (i.e., needle in a haystack); however, single particle techniques have recently become available for studying complex agricultural systems, including soils. For example, the characterization of engineered nanoparticles or incidentally generated particulate pollutants within a natural soil or sediment is now possible using techniques such as single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Nonetheless, in order to exploit the single particle techniques, it is first necessary to representatively sample the soils. The approach presented here has been designed to help better understand the impact of incidental and engineered nanoparticles on agricultural soils. In this study, we examine two approaches for extracting colloidal particles (CP) from soils in order to facilitate their characterization by single particle inductively coupled plasma mass spectrometry using a sector field- (SP-ICP-SF-MS) and time-of-flight- (SP-ICP-ToF-MS) based instruments. A novel sampling methodology consisting of an ultrasound-assisted continuous-flow extraction (USCFE) was developed and compared to a commonly used batch extraction procedure. Metal containing colloidal particles (M–CP) were quantified and characterized following their extraction in ultrapure water and tetrasodium pyrophosphate (TSPP). At least five successive extraction cycles of 18 h each were required to optimally extract Si–CP (ca. 6 × 1015 kg−1) using the batch extraction approach, whereas similarly high numbers of CP could be extracted by USCFE in about 3 h. The combined use of continuous flow, ultrasound and TSPP improved the sampling of colloidal particles and nanoparticles from an agricultural soil. Due to its higher sensitivity, SP-ICP-SF-MS was used to measure the smallest detectable M–CP in the soil extracts. SP-ICP-ToF-MS was used to determine the multi-elemental composition of the extracted colloidal particles.

Soil Systems doi: 10.3390/soilsystems10010014

Authors: Evgeny Lodygin

The issue of formulating scientifically sound standards for mercury (Hg) content in Arctic soils is becoming increasingly pertinent in view of the rising human impact and climate change, which serve to augment the mobility of Hg compounds and their involvement in biogeochemical processes. In the absence of uniform criteria for regulating Hg concentrations, it is particularly important to determine its geochemical baseline values and the factors that determine the spatial and vertical distribution of the element in the soil profile. The study conducted a comprehensive investigation of Hg content and patterns of its distribution in various types of tundra soils in the European North-East of Russia. The mass fraction of total Hg was determined by atomic absorption spectrometry, and the spatial features of accumulation were analysed using geoinformation technologies. The distribution of Hg in the soils of the tundra zone was found to be distinctly mosaic in nature, determined by the combined influence of organic matter, granulometric composition, and hydrothermal conditions. It has been established that the complex influence of the physicochemical properties of soils determines the spatial heterogeneity of Hg distribution in the soils of the tundra zone. The most effective Hg accumulators are peat and gley horizons enriched with organic matter and physical clay fraction, while in Podzols, vertical migration of Hg is observed in the presence of a leaching water regime. In order to standardise geochemical baseline Hg values, a 95% upper confidence limit (UCL95%) is proposed. This approach enables the consideration of natural background fluctuations and the exclusion of extreme values. The results obtained provide a scientific basis for the establishment of standards for Hg content in background soils of the Arctic.

Soil Systems doi: 10.3390/soilsystems10010013

Authors: Mohamed El Hassan Bouchari Abdelilah Meddich Abderrahim Boutasknit Redouane Ouhaddou Boujemaa Fassih Lahoucine Ech-Chatir Mohamed Anli Abdelmajid Haddioui

In the context of climate change, alterations to the physico-chemical properties of soils, particularly in Mediterranean regions, are a growing source of preoccupation. This study analyzes the ecological plasticity and biochemical adaptability of Thymus saturejoides to changes in soil physico-chemical properties in four contrasting environments in Morocco’s western High Atlas (TM: Tidili msfioua, SF: Sti fadma, TA: Taouss, TN: Tisi ntast). It highlights the influence of edaphic characteristics on the physiology and metabolic composition of the species, revealing marked soil heterogeneity between sites. The results for the physico-chemical characteristics of the soil revealed marked heterogeneity between sites. Tisi ntast and Taouss soils had the highest values in terms of electrical conductivity (TN: 0.25 dS/m, TA: 0.18 dS/m), available phosphorus (TN: 18.58 ppm and TA: 26.06 ppm) and total nitrogen (TN: 0.27% and TA: 0.14%), associated with a silty texture, suggesting higher fertility. Conversely, the soil at the TM site was characterized by low total nitrogen content (0.09%), a high C/N ratio (24.4) and a sandy-silty texture, indicating more constraining conditions for plant growth. From a physiological standpoint, plants from the TA site had the lowest chlorophyll levels (17.10 mg g−1FW), while those from the TN site showed the highest levels (31.08 mg g−1FW), accompanied by increased protein content and reduced polyphenol oxidase and peroxidase. In contrast, TM plants showed significant accumulation of total soluble sugars (30 mg g−1FW), proline (22.53 µmol g−1FW), hydrogen peroxide (1.33 nmol g−1FW) and malondialdehyde (62.97 nmol g−1FW), reflecting strong activation of oxidative stress responses. On the other hand, plants from the TA site displayed significantly lower levels of these stress markers compared to other sites, suggesting greater physiological resilience. These results highlight the pivotal role of interactions between edaphic and environmental conditions in modulating plant physiological and biochemical responses, shedding light on the ecological adaptation mechanisms of plant species to the contrasting ecosystems of the Western High Atlas.

Soil Systems doi: 10.3390/soilsystems10010012

Authors: María del Pilar Fernandez-Murillo Erasmo Cifuentes Antonia Beggs Marlene Manzano Ignacio Gutiérrez-Cortés Constanza Vargas Camilo del Río Fernando D. Alfaro

Marine fog is a key non-rainfall water source that sustains microbial activity and transports dissolved nutrients inland, influencing early soil development in hyperarid ecosystems. However, the mechanisms through which sustained fog inputs drive soil surface modification and biocrust formation remain poorly understood. This study evaluated the effects of long-term fog augmentation on soil surface development, biocrust dynamics, and associated microbial communities in the Atacama Desert. We implemented a four-year fog addition field experiment with three sampling times (T0, T24, T48) to assess changes in soil physicochemical properties, biocrust composition, and the integrated multi-diversity of archaea, bacteria, fungi and protist. Sustained fog input transformed bare soils into biological soil crusts, particularly lichen- and moss-dominated stages. This transition was accompanied by increases in soil nitrogen, variations in organic matter accumulation, a shift from alkaline to near-neutral pH, and improvements in soil stability and water retention. Multi-diversity increased over time and was positively associated with ecosystem variables linked to water availability, structural stabilization, and decomposition. These functions, integrated into an ecosystem multifunctionality index, also increased under prolonged fog input, revealing a positive relationship between multifunctionality and multi-diversity. Overall, the results demonstrate that sustained fog input strongly enhances early soil surface development and biocrust establishment, highlighting the ecological importance of marine fog in shaping biodiversity and ecosystem functioning in hyperarid landscapes.

Soil Systems doi: 10.3390/soilsystems10010011

Authors: Azamat Suleymanov Mikhail Komissarov Ruslan Suleymanov Ilyusya Gabbasova

Soil structure is one of the key soil water-physical properties that determine the water–air regime and ultimately affect soil fertility. This study aimed to test different machine learning (ML) methods in combination with environmental variables (soil and climate) and remote sensing data derived from Landsat 8 for prediction of key structure parameters of topsoil (0–25 cm) in semi-arid areas (Trans-Ural steppe zone, Republic of Bashkortostan, Russia). The all studied soil types (Chernozems (n = 24), Solonchaks (n = 9)) and Solonetzes (n = 12)) characterized by “excellent” aggregate state (the average structural coefficient (Ks) was 6.52, 11.23 and 5.70) and “good” resistance of aggregates to destruction by water (soil aggregate stability coefficient (Ksas)—0.67, 0.65 and 0.70, respectively). The soils had a high proportion of agronomically valuable aggregates (0.25–10 mm, mesoaggregates (MEA)), and a low proportion of blocky/lumpy (>10 mm, macroaggregates (MAA)) and fine/dusty (<0.25 mm, microaggregates (MIA)) ones. In particular, the average share of MIA, MEA, and MAA in Chernozem was 7.63, 83.20, and 11.73%, and in Solonchak, 4.24, 87.91, and 9.74%, respectively. After wet sifting, the water-resistant macroaggregates (WSMAA) were not identified (they were destroyed by water) in all studied soils; the proportion of water-stable mesoaggregates (WSMEA) in Chernozems was 65.92 and microaggregates (WSMIA)—39.67; Solonchaks—74.95 and 22.54; Solonetz soil—66.77 and 33.22%; respectively. Under the ML framework, the best model was achieved for Ksas predictions (R2 = 0.50 and RMSE 0.17), where spectral indices (NDWI, EVI, SAVI, and NDVI) were the main predictors. Other ML techniques explained 22-30% variance of the remaining properties. The findings of this study can be valuable in further endeavors for soil water-physical mapping and accelerate the adoption of measures for land management/reclamation planning for landscapes with similar (arid and semi-arid) natural climatic conditions.

Soil Systems doi: 10.3390/soilsystems10010010

Authors: Patrícia da Silva Gomes Assunção Andrade de Barcelos João Batista Pereira Cabral Fernanda Luisa Ramalho Hudson Moraes Rocha Valter Antonio Becegato Alexandre Tadeu Paulino

This study aimed to quantify and assess the spatial distribution of 238U, 232Th, and 40K in the soils of the Espora Hydroelectric Power Plant (Espora HPP) and Queixada Small Hydroelectric Power Plant (Queixada SHPP) watershed (model hydraulic development areas) and their relationship with the geological, chemical, physical, and biological aspects of the soil. The study areas are located in the Corrente River drainage basin, in the southwestern portion of the state of Goiás, Brazil. Radionuclides were quantified using a PGIS-2 portable gamma spectrometer, with measurements taken at 21 sampling points. Soil samples were collected from the surface layer (0–20 cm) for particle-size and chemical analyses. The results indicated that the average radionuclide contents in the soils were 64.49 Bq/kg for 40K, 45.44 Bq/kg for 238U, and 4.53 Bq/kg for 232Th. When comparing these values with the global average established by UNSCEAR, it was observed that 232Th and 40K concentrations were below the global reference, whereas 238U concentration exceeded the world average of 33 Bq/kg. Particle-size characterization revealed significant variability in soil texture, with sand content ranging from 51.46 to 90.91%, clay content from 7.45 to 30.64%, and silt content from 1.64 to 17.90%. Organic matter content had an average of 10.09 g/kg, while soil pH ranged from 4.67 to 6.54. The results of this study have demonstrated the relevance of integrating radiometric and geochemical data for assessing environmental safety in hydroelectric development areas. The approach adopted can support monitoring programs and decision-making processes related to soil management and land-use planning in regions influenced by hydraulic infrastructures.

Soil Systems doi: 10.3390/soilsystems10010009

Authors: Marwa Zouari Mohamed Hachicha Ewald Schnug

In arid regions, irrigation is essential for sustaining crop production, but irrigation water often contains high levels of salts that may reduce yields. This study aimed to evaluate crop responses to irrigation water with salinity levels exceeding 4 g/L (≈6.25 dS/m). A large-scale field survey was conducted across several Tunisian governorates, covering a wide range of crops and production systems. Irrigation water salinity and corresponding crop yields were recorded and analyzed to determine tolerance patterns under real farming conditions. Results indicate that, even under high salinity conditions, several cropssuch as carrot (Daucus carota), barley (Hordeum vulgare), and tomato (Solanum lycpersicum), can maintain high yields, highlighting their potential for saline irrigation in arid regions. These findings provide valuable insights for irrigation management, crop selection, and the development of sustainable agricultural practices in arid environments.

Soil Systems doi: 10.3390/soilsystems10010008

Authors: Mohamed Rajhi Tamas Deak Endre Dobos

Accurate prediction of soil texture is essential for effective soil management, precision agriculture, and hydrological modeling. This study proposes a novel, data-driven approach for estimating soil texture without the need for laboratory-based analysis. High-frequency in situ soil moisture measurements from EnviroSCAN (Sentek Technologies, Stepney, Australia) sensors and satellite-derived vegetation indices (NDVI) from Sentinel-2 were collected across 25 sites in Hungary. Temporal soil moisture dynamics were encoded using a Long Short-Term Memory (LSTM) neural network, designed to capture soil-specific hydrological response behavior from time-series data. The resulting latent embeddings were subsequently used within an ordinal regression framework to predict ordered soil texture classes, explicitly enforcing physical consistency between classes. Model performance was evaluated using leave-one-soil-out cross-validation, achieving an overall classification accuracy of 0.54 and a mean absolute error (MAE) of 0.50, indicating predominantly adjacent-class errors. The proposed approach demonstrates that soil texture can be inferred from dynamic environmental responses alone, offering a transferable alternative to fraction-based regression models and supporting scalable sensor calibration and digital soil mapping in data-scarce regions.

Soil Systems doi: 10.3390/soilsystems10010007

Authors: Ledemar Carlos Vahl Roberto Carlos Doring Wolter Antônio Costa de Oliveira Filipe Selau Carlos Robson Bosa dos Reis Rogério Oliveira de Sousa

In flooded soils, the concentrations of exchangeable Mn2+ and, especially, Fe2+ can be high and must be considered when determining the cation exchange capacity (CEC) of the soil under flooded conditions. However, these reduced forms of Mn and Fe are oxidized and precipitated during the extraction process used in traditional CEC methods. This procedure underestimates the exchangeable portion of these cations and, consequently, the CEC value of the flooded soil. We introduce a pH-gradient-based model to predict ECEC and exchangeable Fe2+ in flooded soils, circumventing oxidation artifacts inherent in conventional methods. The objective of this study is to propose an alternative to estimate the exchangeable Fe2+ and the effective CEC (ECEC) of flooded soils. To achieve this goal, 21 surface samples (0–20 cm) of soil from rice fields were collected and distributed in the cultivation regions of southern Brazil. The soils were flooded for 50 days. The soil solution was collected on the first day and after 50 days of flooding and pH, Na, K, Ca, Mg, Fe and Mn were determined. In these samples, exchangeable cations (K, Na, Ca, Mg, Mn, Al and H + Al) were determined to calculate ECEC and CEC at pH 7 of unflooded soil and after 50 days of flooding. There was a wide range of variation in the exchangeable cation contents among the soil samples. The K contents ranged from 0.12 to 0.54 cmolc kg−1, the Na contents from 0.00 to 1.18 cmolc kg−1, the Ca contents from 0.48 to 37.31 cmolc kg−1, the Mg contents from 0.10 to 15.53 cmolc kg−1, the Mn contents from 0.01 to 0.36 cmolc kg−1, the Al contents from 0.10 to 1.74 cmolc kg−1 and the H + Al contents from 2.01 to 8.42 cmolc kg−1. The results were used to develop models to predict ECEC and exchangeable Fe content after 50 days of flooding. Estimating the ECEC after flooding using the pH gradient before and after flooding yielded values closer to CEC pH 7.0, correcting for the possible underestimation of the ECEC during flooding. The amount of exchangeable Fe estimated was higher than the exchangeable Fe determined, correcting the possible underestimation of these quantities determined during flooding. It is concluded that the estimations of ECEC after flooding through the equation ECECafter=ECEC+pHsol.after− pHsol.before × (CECpH7− ECEC)(7− pHsol.before), where pHsol.before is pre-flooding soil pH, pHsol.after is after flooding pH, ECECafter is effective CEC after flooding and the exchangeable Fe2+ after flooding through the equation Feexc.after.estimated=ECECafter− Ca+Mg+K+Na+Mn where Feexc.after.estimated is estimated exchangeable Fe2+ after flooding corrected the problem of underestimating the values of these variables by analytical methods, demonstrating its viability for use in flood-prone soils.

Soil Systems doi: 10.3390/soilsystems10010006

Authors: Yu Fan Pengrui Ai Fengxiu Li Tong Heng Yan Xu Zhifeng Wang Zhenghu Ma Yingjie Ma

Freshwater scarcity in arid regions is driving increased use of saline irrigation, yet salinity severely degrades soil structure and suppresses enzymatic function. To address this critical challenge for sustainable soil management, this study systematically evaluated magnetized saline water (MSW) across three salinity levels (1, 3, and 6 g L−1) and four magnetic field strengths (0, 0.2, 0.4, and 0.6 T), confirming the magnetic field intensity (C) × salinity (S) interaction. The comprehensive analysis integrated data on aggregate stability, key ion concentrations (Ca2+, Mg2+, Cl−), and major enzyme activities. Structural Equation Modeling (SEM) was utilized to quantify the underlying mechanisms, demonstrating that structural improvement is primarily driven by strong indirect pathways, mediated by optimized ion dynamics and increased enzyme-mediated organic matter turnover. The moderate-salinity (3 g L−1), moderate-magnetic-field (0.4 T) regime emerged as the optimal balanced strategy for overall soil health. These findings offer a scalable approach, guiding future field-scale research toward long-term agricultural sustainability.

Soil Systems doi: 10.3390/soilsystems10010005

Authors: Pinchas Fine Arie Bosak Anna Beriozkin Dorit Shargil Uri Mingelgrin Yephet Ben-Yephet Daniel Kurtzman Ido Nitzan Shahar Baram Ami Gips Tali Kolokovski Amos Ovadia Efraim Zipilevish Uri Zig Oren Buchshtab

Application of CFA-treated biosolids (NVS) offers multiple benefits to agricultural soils, including fertilizer replacement, soil rehabilitation, and disinfection. It also poses a heavy metal(loid)s threat to the agro-environment. NVS (and CFA to some extent) was tested in lysimeter and field trials, using soils differing in physicochemical properties and a large selection of crops. Consistently, As, Pb, and Cd concentrations in leachate were at or below detection limit, and these and other heavy metal(loid)s (and P) were within the permitted range in plant tissue. Foliage Mo (occasionally also Se, P) concentrations often increased significantly, especially in crops (legumes, potatoes) grown on marginal soils, which also displayed significantly higher yields. CFA and NVS reduced lettuce and legumes foliage Mn (and occasionally Zn) concentrations, which remained, however, adequate. NVS (214 and 642 mT ha−1), digested sewage sludge (ADS) and its compost (24 and 72 mT ha−1), temporarily increased the DTPA-extractability of some elements (NVS: B, Cr; ADS: Cu, Ni, Zn; Compost: Zn) 10–30-fold. The extractabilities of Fe and P increased by up to six times. These increases vanished soon after additive application, supporting the hypothesis of ‘self-attenuation’ by applied biosolids. Our data indicate that long-term application of NVS (and CFA) to calcareous soils poses no heavy metal(loid)s-related threat to the agro-environment.

Soil Systems doi: 10.3390/soilsystems10010004

Authors: Sergey N. Gorbov Nadezhda V. Salnik Suleiman S. Tagiverdiev Marina V. Slukovskaya Margarita V. Kochkina Svetlana A. Tishchenko Elena V. Gershelis Vyacheslav V. Kremenetskiy Alexander V. Olchev

This study is one of the first comprehensive assessments of soil carbon dynamics on the Black Sea coast of Russia, focusing on the role of soils in the terrestrial carbon cycle and the greenhouse gas balance of sub-Mediterranean ecosystems. Our integrated approach combined soil classification with the analysis of the distribution of organic and inorganic carbon, as well as the measurement of microbial biomass and respiration. Soil respiration components, including substrate-induced respiration (SIR) and basal respiration (BR), as well as greenhouse gas (carbon dioxide (CO2) and methane (CH4)) dynamics, were evaluated using a combination of laboratory and field measurements. Our results revealed significant differences between natural Rendzic Leptosols and terraced Skeletic Rendzic Leptosols (Technic and Transportic types). The latter contained higher organic carbon stocks (up to 25 kg m−2) associated with buried humus horizons, whereas the former were dominated by inorganic carbon accumulation. Microbial biomass carbon (MBC) ranged from 113 to 1119 µg C g−1 of soil and decreased with depth. Basal respiration averaged 0.39 ± 0.30 µg C–CO2 g−1 h−1. CO2 emissions were strongly correlated with soil temperature (r = 0.65, p < 0.05) and negatively correlated with soil moisture, reflecting the predominant influence of abiotic factors. Seasonal chamber observations confirmed that these soils consistently function as CH4 sinks, with negative CH4 fluxes recorded across all seasons. Thus, Rendzic Leptosols on the Black Sea coast serve as significant CO2 sources and stable CH4 sinks simultaneously, and anthropogenic terracing enhances their potential for organic carbon sequestration. These findings refine our understanding of the carbon balance in sub-Mediterranean forest soils and highlight their dual role in greenhouse gas dynamics under changing climate conditions.

Soil Systems doi: 10.3390/soilsystems10010003

Authors: Hartina Tidarat Monkham Worachart Wisawapipat Patma Vityakon Tanabhat-Sakorn Sukitprapanon

Managing phosphorus (P) in acidic paddy soils is crucial for sustaining rice yields. However, the effects of combined humic acid (HA) and flue gas desulfurization gypsum (FG), a by-product of coal-fired power plants, on P forms remain poorly understood. This study examined P forms using a sequential extraction procedure and XANES spectroscopy following the application of HA, FG, and HA + FG. HA increased organic labile P, while FG and HA + FG promoted HCl-extractable Pi and humic Po, respectively. XANES data revealed that P associated with aluminum (Al) (hydr)oxides was dominant in acidic paddy soils. Brushite (CaHPO4·2(H2O)) accounted for 25% and 19% of total P in the FG- and HA + FG-treated soil, respectively. Iron (Fe)-bound P was absent in control and FG-treated soils but was present as strengite (FePO4·2H2O) in HA- and HA + FG-treated soils (23% and 30% of the total P, respectively). Inositol hexakisphosphate (IHP), a non-labile Po, was in HA- and HA + FG-treated soil (12% and 31% of the total P, respectively). Archerite (KH2PO4) was 40% and 20% of the total P in HA- and HA + FG-treated soil, respectively. HA alone is an effective soil amendment that enhances P cycling and availability by increasing organic P mineralization, boosting rice yield in acidic paddy soil.

Soil Systems doi: 10.3390/soilsystems10010002

Authors: Aaron Ohene Boanor Rose Nimoh Serwaa Jin Hee Park Jwakyung Sung

Long-term exposure of plastics to the environment causes them to disintegrate, resulting in the formation of micro/nanoplastics as well as the release of additives and chemicals into the soil. The micro/nanoplastics are able to readily migrate into the soil, destabilize the soil microbiota, and finally enter crop plants. Endocytosis, apoplastic transport, root adsorption, transpiration pull, stomatal entry, and crack-entry mode are well-known pathways by which microplastics enter into plants. Roots of vegetable crops were able to transfer 0.2 µm–1.0 µm of microplastics through root adsorption and by transpiration pull to the xylem and then further transported them to the plant tissues through apoplastic pathways. Beads of 1000 nm size were also engulfed by BY-2 protoplast cells through endocytosis. Micro and nanoplastics that enter crops affected the physiological and biochemical activities of the plants. Aquaporins were needed to aid the symplastic pathway which made the symplastic pathway difficult for MPs/NPs transport. Microplastics block seed capsules and roots of seedlings, thereby negatively affecting the uptake and efficient use of nutrients supplied. Photosynthesis of plants was affected due to the reduction in chlorophyll contents. Exposing soils to MPs/NPs drastically affected the pH, EC, and bulk density of the soil. This review focused on bridging the knowledge gap with understanding how microplastics prevent nutrient uptake and nutrient use efficiency in plants. This understanding is essential for assessing the broader ecological impacts of plastic contamination and for developing effective mitigation strategies. Further research is needed on microorganisms capable of degrading plastics, as well as on developing analytical methods for detecting plastics in soil and plant tissues. Also, further research on how to replace plastic mulching and still provide the same benefits as plastic mulch is needed.

Soil Systems doi: 10.3390/soilsystems10010001

Authors: Zuhair Masri Francis Turkelboom Chi-Hua Huang Thomas E. Schumacher Venkataramani Govindan

Steep olive orchards in northwest Syria are experiencing severe land degradation as a result of unsustainable uphill–downhill tillage, which accelerates erosion and reduces productivity. To address this problem, three tillage systems, no-till natural vegetation strips (NVSs), contour tillage, and uphill–downhill tillage, were evaluated at two research sites, Yakhour and Tel-Hadya, NW Syria. The adoption of no-till NVSs significantly increased soil organic matter (SOM) at both sites, outperforming uphill–downhill tillage. While contour tillage resulted in lower SOM levels than NVSs, it still performed better than the conventional uphill–downhill practice. Contour soil flux (CSF) was lower in Yakhour, where mule-drawn tillage on steep slopes (31–35%) was practiced, compared to higher CSF values in Tel-Hadya, where tractor tillage was applied on gentler slopes (11–13%), which highlights the influence of slope steepness on soil fluxes. Over four years, net soil flux (NSF) indicated greater soil loss under tractor tillage, confirming that mule-drawn tillage is less disruptive. Olive trees with no-till NVSs benefited from protected root systems, improved soil structure through SOM accumulation, reduced erosion risk, and improved surface runoff buffering, which resulted in increased water infiltration and soil water retention. This study was carried out using a participatory technology development (PTD) framework, which guided the entire research process, from diagnosing problems to co-designing, field testing, and refining soil conservation practices. In Yakhour, farmers actively identified the challenges of degradation. They collaboratively chose no-till natural vegetation strips (NVSs) and contour tillage as key interventions, valuing NVSs for their ability to conserve moisture, suppress weeds and pests, and increase olive productivity. The farmer–scientist co-learning network positioned PTD not only as an outreach tool but also as a core research method, enabling locally relevant and scalable strategies to restore soil functions and combat land degradation in northwest Syria’s hilly olive orchards.

Soil Systems doi: 10.3390/soilsystems9040138

Authors: Yulian Farkhodov Natalia Danchenko Igor Danilin Irina Grigoreva Natalia Matveeva Aliia Ziganshina Nikita Ermolaev Sergey Yudin Ivan Nadutkin Sergey Kambulov Vladimir Kholodov

Soil conservation technologies are widely studied for their effects on soil organic carbon (SOC) preservation, yet their impact on the composition of soil organic matter (SOM) remains underinvestigated. This study evaluated the effects of two non-inversion tillage systems, MP and NT, on agro-physical and chemical properties and SOM composition (including water-extractable matter) in Haplic Chernozem Pachic. After 12 years, non-inversion tillage showed no significant differences in SOC, WEOC, and soil structure condition compared to MP. Only NT treatment distinctly enhanced the coefficient of soil structuring (Kstr) and mean diameter of water-stable aggregates (MWDWSA), by 1.5 and 2 times, respectively. Differences in SOM composition were clearly pronounced between treatments in the 0–10 cm layer. Non-inversion tillage favored microbial-derived stable SOM, whereas NT enriched SOM with fresh plant material. Our findings revealed that non-inversion tillage shifts the composition of SOM toward recalcitrant components even more than MP due to limited fresh OM input and enhanced mineralization of unprotected SOM during tillage. This poses carbon loss risks. Periodic moldboard plowing may be a way to improve carbon retention in non-inversion tillage, as it allows plant residues to be incorporated into the soil profile and replenish organic matter.

Soil Systems doi: 10.3390/soilsystems9040137

Authors: Pavlos Tziourrou Evangelia E. Golia

The increasing presence of microplastics (MPs) in terrestrial ecosystems, particularly when combined with organic pollutants and heavy metals, presents a considerable environmental challenge. This review examines the intricate interactions between MPs, co-contaminants (both organic and inorganic), and plants involved in phytoremediation processes. A literature search was performed across the databases Scopus, ScienceDirect, and Google Scholar, covering the timeframe from 2015 to 2025. The studies selected specifically addressed the synergistic and antagonistic effects of microplastics in conjunction with heavy metals or organic pollutants (such as PAHs and pesticides) within plant–soil systems. The findings reveal that MPs influence pollutant mobility, bioavailability, and toxicity through adsorption and desorption mechanisms, leading to varied implications for plant growth, microbial communities, and contaminant uptake. Depending on the physicochemical characteristics of MPs and co-pollutants, the effects can range from increased phytotoxicity to diminished contaminant accumulation in plants. Additionally, physiological and molecular disruptions, including oxidative stress, hormonal imbalances, and impaired enzymatic activity, were frequently noted in co-contamination scenarios. Recent developments, such as the creation of genetically modified hyperaccumulator plants and the use of nanotechnology and microbial consortia, demonstrate potential to enhance phytoremediation efficiency in complex polluted soils. This review underscores the pressing need for integrated, multidisciplinary strategies to overcome the limitations of existing phytoremediation methods in co-contaminated environments. Future research should focus on standardized methodologies, a mechanistic understanding, and the safe implementation of emerging biotechnologies for sustainable soil remediation.

Soil Systems doi: 10.3390/soilsystems9040136

Authors: Afia Sultana Qingyue Wang Miho Suzuki Christian Ebere Enyoh Md. Sohel Rana Yugo Isobe Weiqian Wang

Heavy metal contamination in agricultural soils poses serious threats to food safety, ecosystem integrity, and public health. This study investigates the concentrations, ecological risks, and human health impacts of nine heavy metals Cr, Mn, Co, Ni, Cu, Zn, Pb, As, and V in homestead agricultural soils collected from two depths, surface (0–20 cm) and subsurface (21–50 cm), across industrial and non-industrial regions of Bangladesh, using inductively coupled plasma mass spectrometry (ICP-MS). Results revealed that surface soils from industrial areas exhibited the highest metal concentrations in order of Mn > Zn > Cr > Pb > V > Ni > Cu > As > Co. However, maximum As levels were detected in non-industrial areas, suggesting combined influences of local geology, intensive pesticide application, and prolonged irrigation with As-contaminated groundwater. Elevated concentrations in surface soils indicate recent contamination with limited downward migration. Multivariate statistical analyses indicated that industrial and urban activities are the major sources of contamination, whereas Mn remains primarily geogenic, controlled by natural soil forming processes. Contamination factor (CF) and pollution load index (PLI) analyses identified Pb and As as the principal pollutants, with hotspots in Nairadi, Majhipara (Savar), Gazipur sadar, and Chorkhai (Mymensingh). Ecological risk (ER) assessment highlighted As and Pb as the dominant environmental stressors, though overall risk remained low. Human health risk analysis showed that ingestion is the primary exposure pathway, with children being more susceptible than adults. Although the hazard index (HI) values were within the acceptable safety limits, the estimated carcinogenic risks for As and Cr exceeded the USEPA thresholds, indicating potential long term health concerns. Therefore, the cumulative carcinogenic risk (CCR) results demonstrate that As is the primary driver of lifetime carcinogenic risk in homestead soils, followed by Cr, while contributions from other metals are minimal. These findings emphasize the urgent need for continuous monitoring, improved industrial waste management, and targeted mitigation strategies to ensure safe food production, a cleaner environment, and better public health.

Soil Systems doi: 10.3390/soilsystems9040135

Authors: María Teresa Salazar-Ramírez Rubén Palacio-Rodríguez Jesús Josafath Quezada-Rivera Tania Elizabeth Velásquez-Chávez Gisela Muro-Pérez Hortencia Ivone Ortega-Reyes Jorge Arnaldo Orozco-Vidal Antonio Gerardo Yescas-Coronado Gerardo Antonio Verástegui-Hernández Jorge Sáenz-Mata

Soil salinity imposes a critical constraint on plant productivity, highlighting the need for sustainable biological strategies to enhance stress tolerance. This study assessed the effects of volatile organic compounds (VOCs) emitted by ten plant-growth-promoting rhizobacteria (PGPR) isolated from the rhizosphere of Euphorbia antisyphilitica on the growth of Arabidopsis thaliana seedlings exposed to 0, 50, and 100 mM NaCl. A divided Petri dish system was used to quantify biomass, root architecture, proline accumulation, sodium content, and chlorophyll concentration. Three strains—Siccibacter colletis CASEcto12, Enterobacter quasihormaechei NFbEcto18, and Bacillus wiedmannii NFbEndo12—significantly enhanced seedling development under saline and non-saline conditions (p ≤ 0.05). At 50 mM NaCl, S. colletis CASEcto12 increased primary root length from 40.25 to 64.81 mm and fresh weight from 45.05 to 133.33 mg, while E. quasihormaechei NFbEcto18 elevated lateral root number from 10 to 24, compared to the uninoculated control. Under 100 mM NaCl, E. quasihormaechei NFbEcto18 increased proline accumulation (0.564–1.378 mmol g−1 FW) and reduced Na+ content (0.146–0.084 mmol g−1 FW), indicating improved osmotic and ionic regulation. VOC profiling using SPME-GC-MS revealed aldehydes, ketones, and alcohols as predominant classes. Overall, these findings demonstrate the potential of candelilla-associated PGPR VOCs as promising biostimulants for enhancing plant performance in salt-affected soils.

Soil Systems doi: 10.3390/soilsystems9040134

Authors: Giambattista Maria Altieri Josefina Garrido Salustiano Mato Benedicto Soto Vito Santarcangelo Giuseppe Bari Eustachio Tarasco

Soil biodiversity is crucial for maintaining biological soil resilience, understood as a temporal property and as the ability of soils to uphold or recover their ecological functions under stress thanks to the diversity and complementarity of their biological communities. To evaluate this property, we developed the Biological Soil Resilience Index (BSR), conceived as an evolution of the QBS-ar approach by integrating additional key bioindicators—entomopathogenic nematodes, entomopathogenic fungi, and earthworms—together with microarthropod eco-morphological adaptation scores. This multi-taxon framework provides a more comprehensive assessment of soil biological conditions than single-group indices and is specifically designed to be applied repeatedly over time to detect resilience trajectories. The Biodiversity Soil Resilience (BSR) Index was applied across nine sites subject to low, medium, and high anthropogenic disturbance, spanning urban, industrial, and airport environments. Results revealed not a resilience gradient but a clear disturbance gradient: low-impact sites achieved the highest BSR values (52–59), reflecting diverse and functionally complementary assemblages; medium-impact sites maintained moderate BSR value (27–42), but displayed imbalances among faunal groups; and high-impact sites showed the lowest values, including a critically low score at C_HI (17.86), where entomopathogens were absent and earthworm populations reduced. Entomopathogenic organisms proved particularly sensitive, disappearing entirely under severe disturbance. The BSR was sensitive to environmental gradients and effective in distinguishing ecologically meaningful differences among soil communities. Because it can be repeatedly applied over time, BSR provides the basis for monitoring long-term resilience dynamics, detecting early warning signals, and support timely mitigation or restoration measures. Overall, the study highlights the pivotal role of biodiversity in sustaining soil resilience and supports the BSR Index as a simple yet integrative tool for soil health assessment and for future resilience monitoring in disturbed landscapes.

Soil Systems doi: 10.3390/soilsystems9040133

Authors: Stylianos Gerontidis Konstantinos X. Soulis Alexandros Stavropoulos Evangelos Nikitakis Dionissios P. Kalivas Orestis Kairis Dimitrios Kopanelis Xenofon K. Soulis Stergia Palli-Gravani

Soil maps are essential for managing Earth’s resources, but the accuracy of widely used global and pan-European digital soil maps in heterogeneous landscapes remains a critical concern. This study provides a comprehensive evaluation of two prominent datasets, ISRIC-SoilGrids and the European Soil Data Centre (ESDAC), by comparing their soil texture predictions against the detailed Greek National Soil Map, which is based on over 10,000 field samples. The results from statistical and spatial analyses reveal significant discrepancies and weak correlations, with a very low overall accuracy for soil texture class prediction (19–21%) and high Root Mean Square Error (RMSE) values ranging from 13% to 19%. The global models failed to capture local variability, showing very low explanatory power (R2 < 0.2) and systematically underrepresenting soils with extreme textures. Furthermore, these prediction errors are not entirely random but are significantly clustered in hot spots linked to distinct parent materials and geomorphological features. Our findings demonstrate that while invaluable for large-scale assessments, the direct application of global soil databases for regional policy or precision agriculture in a geologically complex country like Greece is subject to considerable uncertainty, highlighting the critical need for local calibration and the integration of national datasets to improve the reliability of soil information.

Soil Systems doi: 10.3390/soilsystems9040132

Authors: Fatima Zohra Batoul Touati Abdelbasset Boumadda Fouzi Benbrahim Abderraouf Benslama Jose Navarro-Pedreño

In arid regions, the soil degradation from salinization, low organic matter content, and compaction severely limits agricultural productivity. Leguminous perennials such as alfalfa (Medicago sativa L.) have the potential to restore soil quality, but their long-term effects remain underexplored in North African drylands. This study aimed to evaluate the impacts of long-term (7–8 years) alfalfa cultivation on soil fertility and salinity in the Ziban region of Algeria. Ninety topsoil samples (0–30 cm) from cultivated and adjacent uncultivated plots were collected and analyzed, determining organic matter (OM), soil organic carbon (SOC), soil nitrogen stock (SNS), electrical conductivity (EC), sodium adsorption ratio (SAR), pH, major cations (Ca2+, Mg2+, Na+), sulfate (SO42−), bulk density (BD), and texture. Compared with uncultivated soils, alfalfa cultivation increased OM by 82.26%, SOC by 78.38%, and SNS by 102.99%, while reducing EC by 40.36%, SAR by 28.94% and BD by 6.16% (p < 0.05), indicating significant improvements in fertility, structure and reductions in sodicity. PCA revealed distinct gradients separating fertility–salinity parameters from compaction–sodicity in cultivated and uncultivated soils. These results confirm that alfalfa systems enhance nutrient cycling, reduce salt stress, and improve structural stability in arid agroecosystems through reduced bulk density and increased organic matter in arid agroecosystems. Integrating alfalfa into land management strategies could promote sustainable restoration of degraded soils in drylands. Further research should optimize irrigation and organic inputs to maximize these benefits under climate-stress conditions.