Search Results (442)

Agriculture in the Pacific is driven primarily by small-scale private farmers, many of whom do not have access to soil testing services or advice, nor the means to interpret analytical results into soil management and agronomic recommendations. Soil degradation through the process of acidification poses a significant risk to food and income security as it directly threatens crop productivity. The nutritional quality of food crops may also be affected through sub-optimal nutrient uptake by plants and nutrient imbalances. The dataset reported here provides a useful platform for the development of a decision-support tool (DST) that will assist Fiji farmers in understanding and managing soil pH and soil acidity. The DST will enable making informed decisions about liming to help correct soil pH. To support this development, historical soil pH data available from the Pacific Soils Portal were combined with updated analyses of agricultural soils from 17 locations in Viti Levu Island (Fiji) collected during a field campaign undertaken in August 2025. The soils were sampled at two depth intervals (0–15 and 15–30 cm) and analyzed for pH using a variety of methods. These methods included direct field measurements using a portable pH-meter as well as traditional laboratory determinations. Of the soils sampled, it was found that most soils exhibited pH levels below 7, which were observed for both depth intervals. Across all samples taken in 2025, it was found that 54.3% of them had soil pH < 5, 38.6% had soil pH between 5 and 6, and 7.1% had pH > 6 (based on soil pH_1:5 soil-to-water method). Depending upon specific land uses, climate and cropping intensity, it was recommended that routine liming be built into soil fertility management programs to help farmers overcome soil acidity-related constraints to production. Liming frequency, timing of application and application rate will need to be determined for specific soil and cropping situations; however, it was suggested that soil pH was not changed by more than 1 unit each time lime was applied. Such an approach should reduce the risk of soil organic matter loss through accelerated mineralization, which would be challenging to restore in that environment if soils remained under continuous cropping. The analytical information contained in this article expanded and updated the datasets available in the Pacific Soils Portal. Furthermore, this work provided an opportunity to build analytical expertise in aspects of soil chemistry at local organizations to support academic and extension activities as well as the ongoing development of the Pacific Soils Portal. Full article

Copper flotation tailings are produced in large quantities during ore beneficiation and smelting, yet remain underutilized and can act as persistent sources of potentially toxic elements. Here, we combined XRD-based mineralogical characterization, ICP-OES quantification, Tessier sequential extraction, and pH-dependent batch leaching to elucidate metal occurrence, mobility, and associated ecological risk in tailings from Tongling, Anhui Province. This study systematically analyzed the mineral composition, potentially toxic elements content, chemical fractions, leaching behavior, and ecological risks of copper flotation tailings from the Shuimuchong tailings reservoir in Tongling, Anhui Province. XRD and XRF analyses revealed that calcite, quartz, and garnet were dominant mineral phases in the tailings. Elevated levels of Cu, Cd, Pb, Zn, and As were detected, some of which surpassed both local background concentrations and national soil quality standards. Most potentially toxic elements primarily existed in the residual fraction, indicating low mobility. Leaching experiments revealed that Zn, Cu, and As showed enhanced release under acidic conditions, making them priority risk elements during tailings acidification. Pollution index and ecological risk assessments indicated that the tailings were heavily contaminated, with Cu and Cd as the main risk contributors. The Risk Assessment Code (RAC) evaluation showed that Cd had the highest bioavailability and ecological risk. By clarifying the behavior of pollutants, this study contributes to the effective regulation of environmental hazards and the sustainable use of tailing materials. Full article

The synergistic effects of soil acidification and heavy metal pollution present major challenges for global agroecosystems. To systematically trace the evolution of research and identify key topics in this field, this study employed CiteSpace to visualize and analyze 691 records from the China National Knowledge Infrastructure (CNKI) and 6747 highly relevant articles or reviews from the Web of Science (WOS) Core Collection database from 2005 to 2025. The results indicate a steady to rapid rise in global publications, with China contributing the largest share, at 2468 publications. This has produced a research cluster centered around the Chinese Academy of Sciences (CAS); however, the centrality of its international cooperation remains limited. Studies in the CNKI database are driven by agricultural needs, focusing on national food security, rice yield stability, improvement of arable land, and heavy metal passivation and remediation, with a concentration on basic agricultural science. By contrast, research in the WOS database emphasizes fundamental mechanisms and interdisciplinary integration, addressing aluminum toxicity, microbial communities, the nitrogen cycle, and global climate change, intersecting fields such as environmental science, soil science, ecology, and microbiology. The evolution of research hotspots shows a clear trajectory: from acidity regulation and chemical speciation analysis of heavy metals (2005–2013), to heavy metal passivation, remediation, and phytoremediation (2014–2018), and then to biochar materials, microbiome analysis, and the synergistic role of carbon sequestration (2019–2025). This study argues that future research should move beyond single remediation measures and adopt integrated strategic management to jointly improve bioremediation efficiency, promote soil carbon sequestration and soil health, and enhance microbial adaptation to global climate change. Full article

Cadmium is an element that is unnecessary for the functioning of plant and animal organisms, and its widespread presence in the environment poses a serious threat to human and animal health. Therefore, effective methods are being sought to remediate soils contaminated with this element, including through the enrichment of degraded soils with organic matter. To this end, the effectiveness of selected organic sorbents, including starch, fermented bark, compost and humic acids, in mitigating the transfer of cadmium and other heavy metals from soil to plants was assessed. Model studies compared the effects of 15 and 30 mg of cadmium (Cd) per kg of soil with an uncontaminated control sample. The sorbents were applied on a carbon basis at a rate of 3 g C per kg of soil. The test plant was Zea mays. Cadmium was found to significantly impair plant growth, causing reductions of 21%, 85%, and 77% in leaf greenness, aboveground biomass and root biomass, respectively. Excess cadmium increased the translocation of lead, chromium, copper, nickel, zinc, iron, and manganese from the roots to the aboveground parts of the plant, while simultaneously limiting their uptake. All of the organic sorbents tested reduced the negative impact of cadmium on leaf greenness, except starch. Compost and HumiAgra significantly improved the condition of Zea mays plants weakened by cadmium exposure. Cadmium contamination increased soil acidification. pH was positively correlated with maize yield and the SPAD leaf greenness index and negatively correlated with the cadmium translocation index and cadmium content in the aboveground parts of maize. Compost and humic acids are among the most effective and practically feasible approaches for reducing cadmium bioavailability in soil and its accumulation in Zea mays, and are therefore recommended for the remediation of cadmium-contaminated soils. Full article

The persistence of cadmium (Cd) immobilization in acidic paddy soils is exacerbated by acidification and fluctuating redox conditions that promote Cd re-mobilization. While biochar is a promising amendment, its long-term efficacy in Cd immobilization relative to conventional lime and the underlying mechanisms remain incompletely resolved. This study tested the hypothesis that biochar’s superior effect lies in its durable enhancement of soil pH buffering capacity (pHBC), not merely in increasing initial pH. Using six acidic paddy soils amended with three biochars (corn straw, peanut straw, and seeded sunflower plate) and pH-matched lime [Ca(OH)₂] controls, we quantified pHBC changes, resistance to simulated acidification, and Cd dynamics during a flooding-drying cycle. Results showed that biochar amendments increased pHBC by 24.7–110%, significantly more than lime. Under acid stress, biochar-treated soils maintained higher pH and released 40–85% less soluble and extractable Cd than lime controls at equivalent pH range. Correlation and regression analyses established that the biochar-induced change in pHBC (ΔpHBC) was the strongest predictor of reduced Cd availability, exerting twice the influence of native soil pHBC. During the redox cycle, enhanced pHBC directly attenuated soil re-acidification upon drainage, minimizing Cd re-mobilization. Thus, the durable enhancement of soil pHBC is the central mechanism for biochar’s sustained Cd immobilization, advocating a strategic shift from transient pH adjustment to building inherent soil buffering resilience for long-term remediation security. Full article

Electrokinetic remediation (EKR) was evaluated in naturally contaminated vineyard soils to assess copper redistribution, treatment redistribution efficiency, and changes in copper fractions across contrasting soil pH conditions. Ten vineyard soils (five acidic, five alkaline) were subjected to a 30-day ex situ EKR experiment under a constant electric field. Total copper content was measured in the anode, cathode, and inter-electrode zones, while copper fractions were quantified only in electrode zones exhibiting the most pronounced post-remediation decrease in total copper. The findings demonstrate that the EKR process generated distinct, soil-type-dependent gradients in copper mobility. In acidic soils, copper exhibited pronounced central-zone accumulation with notable depletion toward the anode, whereas in alkaline soils, the lowest concentrations consistently occurred near the cathode and increased toward the anode. Notably, one slightly alkaline soil displayed the highest redistribution efficiency (43.0%), underscoring the strong influence of soil chemistry on EKR performance. Redistribution efficiencies averaged 29.5% in acidic soils and 12.8% in alkaline soils, although localized acidification enabled notably higher redistribution in highly contaminated samples. These trends reflected on copper fractions: acidic soils showed enhanced release from Fe/Mn oxides and carbonates, while alkaline soils experienced stronger short-term mobilization driven by cation competition and dissolution of less stable oxide phases. Fractionation results indicated that the Fe/Mn oxide-bound fraction was the most susceptible to electromigration, while both acidic and alkaline soils ultimately shifted copper toward less extractable operational fractions. Full article

Promoting the agricultural recycling of biogas slurry (BS) is crucial for sustainable development, yet its long-term ecological impacts remain unclear. Through a multi-year field trial in a sugarcane system, this study examined the effects of BS application (0, 3, and 6 years) on the soil properties, bacterial communities, and functional genes for C, N, P, and S cycling. The results revealed distinct two-phase patterns of changes in soil properties, microbial communities, and functional genes. Short-term (3-year) application induced a “disturbance” phase, characterized by significant acidification (pH decreased by 17.91%), a surge in nitrate-N (increased by 757.27%), and a transient decline in bacterial richness. Long-term (6-year) application drove a “functional restructuring” phase, reversing acidification and significantly increasing soil organic matter (29.05%) and total nitrogen (TN) (20.81%). Bacterial richness recovered, and community composition distinctively restructured. Functional gene analysis revealed shifts in gene abundance that transitioned from high abundance in the short term to a new balance favoring processes like N fixation. Co-occurrence network analysis indicated that this functional shift was associated with core microbial modules (e.g., Firmicutes) and changes in soil pH and SOM. This study suggests that, although short-term application causes significant adjustments, sustained and appropriate BS application can ultimately enhance soil fertility and promote a functionally reorganized state by reshaping microbial interaction networks. It presents a microbial ecological basis for the safe and sustainable use of BS in circular agriculture. Full article

Clubroot caused by Plasmodiophora brassicae is a devastating soil-borne disease of oilseed rape, and physiological race differentiation of the pathogen greatly hinders disease control. The differential regulatory mechanisms of different P. brassicae races on the rhizosphere microecology remain unclear. This study aimed to reveal the race-specific effects of P. brassicae on the rhizosphere microenvironment, microbial community and nitrogen cycling of oilseed rape. A pot inoculation experiment was conducted with two typical races from Sichuan Province (race 4 CZ and race 2 KD), combined with soil physicochemical determination, high-throughput sequencing and functional prediction. The results showed that CZ exhibited a higher infection rate but a lower disease index than KD. Both races significantly decreased soil pH and reshaped soil nutrient profiles. Notably, CZ treatment caused a more pronounced pH decrease and was characterized by NH₄⁺-N accumulation, whereas KD treatment was dominated by NO₃⁻-N enrichment. Bacterial alpha diversity was increased by both races, following the order KD > CZ > CK. In contrast, fungal alpha diversity was decreased by both races, showing the pattern CK > KD > CZ. Distinct rhizosphere microbial community structures were formed under different race infections, and both races reduced the abundance of nitrogen-fixing bacteria and related functional genes. These findings indicate that distinct P. brassicae races shape race-specific rhizosphere microenvironments by differentially regulating soil acidification, nutrient availability and nitrogen-cycling functional microorganisms, thereby driving divergent pathogenic outcomes. This study is the first to reveal differential regulation of the rhizosphere microecology by distinct physiological races of P. brassicae, offering new insights for region-specific management of clubroot disease. Full article

Drought will likely become more frequent and intense in Europe due to climate change, which may worsen Mn²⁺ and P deficiencies found in high pH soils. In this context, research investigating the effectiveness of ammonium-based nitrogen fertilizers treated with nitrification inhibitors (NIs) in alleviating Mn²⁺ and P deficiencies in such soils has been done. However, studies considering the impact of drought periods and soil texture on this topic are lacking. Therefore, we carried out a study addressing this research gap. Maize plants were grown in a greenhouse experiment, and the experimental setup comprised three factors consisting of soil texture (sand and silt loam), soil moisture (sufficient and drought), and DMPP application (with and without DMPP). The measured variables were bulk and rhizosphere soil pH, Mn²⁺ availability, maize biomass yield, and shoot concentration of selected macro- and micronutrients. DMPP increased shoot biomass production by 60% in silt loam under drought but not in sand soil texture. In addition, DMPP increased Mn²⁺ and P shoot concentrations by 38% and 21%, respectively, in the silt loam soil texture under drought. In contrast, DMPP did not alleviate the negative impact of drought on plant biomass production, Mn²⁺ and P shoot concentration in the sand soil texture. In conclusion, DMPP application is effective in alleviating Mn²⁺ and P deprivation in high pH soil subjected to drought. However, this effect was soil texture-dependent and observed in the silt loam rather than in the sand soil texture. Full article

This scoping study assesses practical aspects of electrokinetic (EK) biocementation of clay soil underneath a railway embankment ahead of upscaled testing to include a reduced-scale field pilot as an intermediate step towards subsequent pilot embankment treatment. It considers suitable field setups and performs Life Cycle Analysis (LCA) of biocementation by biostimulation of carbonic anhydrase (CA)-producing bacteria compared to hydrated lime slurry, if both treatments were implemented electrokinetically. LCA analysis was conducted using SimaPro software (version 9.6.0.1) with Ecoinvent database and bench-scale laboratory testing data. Electroosmotic flow modelling was performed to instruct on suitable setups and for estimates of power consumption towards the field application of 30 m of railway embankment and foundation soil. LCA indicated a considerable reduction in global warming if CA biocementation is used (0.00823 kg CO₂ eq for biocement vs. 0.022136 kg CO₂ eq for lime), and resource usage (7.06 × 10⁻⁵ kg Cu eq compared to 8.47 × 10⁻⁵ kg Cu eq for lime). Biocementation was more water-consuming compared to lime, as it involved multiple chemical solutions. Terrestrial acidification, aquatic eutrophication, and ecotoxicity were slightly higher for biocement, possibly due to system boundaries and processes assumed for material production. Further sustainability improvements would be possible if waste materials (e.g., captured industrial CO₂) could be used. Field trials will be essential for validation, system optimisation, and advanced model calibration. Full article

Nanoplastics (NPs) are increasingly detected in agricultural soils, yet their influence on arsenic (As) transfer and plant toxicity remains unclear. Lettuce (Lactuca sativa L.) was cultivated in farmland soil with a naturally high As background (98.8 mg·kg⁻¹) to assess how polyethylene nanoplastics (PE NPs) affect rhizosphere conditions, As accumulation, and plant performance. PE NPs partially buffered soil acidification but reduced rhizosphere water content, while total soil As remained largely unchanged. Leaf As increased by 35–39%, with reduced biomass (up to 30%) and lower chlorophyll status (SPAD ~7% lower). Metabolomic analyses indicated dose-dependent alterations in central carbon metabolism and phenylalanine-related antioxidant metabolites, including suppressed tricarboxylic acid cycle intermediates at higher PE levels. Overall, PE NPs enhanced transfer of background As to edible leaves and intensified phytotoxicity, underscoring the need to consider nanoplastics in risk assessment of As-affected soils. Full article

This study investigated the effects of different application rates of spent mushroom substrate (SMS) from Morchella sextelata on soil properties and microbial communities in a moso bamboo (Phyllostachys edulis) plantation. Three SMS rates (2.4, 4.7, and 9.4 kg·m⁻²) were applied, and soil samples were collected at 6 and 12 months from two depths (0–20 cm and 20–40 cm). One year after application, topsoil total phosphorus (TP) increased 12–20 fold, while available phosphorus (AP) and potassium (AK) were significantly elevated. Soil pH initially decreased but partially recovered, whereas electrical conductivity (EC) continued to rise, indicating salt accumulation. Urease (UA) and sucrase (SA) activities increased 10–17 fold and 3–5 fold, respectively, while catalase (CAT) and acid phosphatase (ACP) were temporarily suppressed. SMS application significantly altered microbial community composition, with Acidobacteriota and Basidiomycota becoming more abundant. Correlation analysis identified pH, organic matter, AP, and UA as key factors linked to microbial changes. The medium application rate (4.7 kg·m⁻²) provided the best balance between soil improvement and environmental risk. These findings demonstrate that M. sextelata SMS can effectively enhance soil fertility while modulating microbial communities, but salt accumulation and short-term acidification warrant attention. Full article

Magnesium is an essential macronutrient for both plants and humans. However, its availability in agricultural systems and dietary intake has been declining, raising concerns about crop productivity and nutritional security. In plants, magnesium plays a critical role in photosynthesis, enzyme activation, carbohydrate transport, and overall metabolic regulation, while in humans it is required for numerous biochemical processes related to energy metabolism, cardiovascular function, and disease prevention. Long-term studies have reported a 20–30% decrease in magnesium concentrations in fruits and vegetables worldwide, potentially contributing to widespread magnesium deficiency. Soil factors such as acidification, nutrient imbalance, and intensive agricultural practices further limit magnesium availability along the soil–plant–human continuum. This review summarizes the biological importance of magnesium in plants and humans, evaluates the occurrence and causes of magnesium deficiency, and discusses current strategies for improving magnesium nutrition through agronomic and genetic biofortification. It considers even fertilizer management, nano-fertilizers, and alternative magnesium sources such as serpentinite. The review highlights biofortification as a cost-effective and sustainable strategy to enhance crop magnesium concentration and mitigate global magnesium deficiency while emphasizing the need for further research on bioavailability, environmental safety, and long-term agricultural sustainability. Full article

Fungal transformation is increasingly recognized as an important process influencing metal solubilization and immobilization in soil environments. In this study, a fungal strain (PTW4) isolated from mining-contaminated soil was molecularly identified as Aspergillus aculeatus. The strain was evaluated for its ability to solubilize and transform several heavy metal oxides, including ZnO, Pb₃O₄, Cu₂O, and MoO₃. PTW4 produced consistent halo formation across all tested oxides, accompanied by progressive acidification of the culture medium, suggesting organic acid-mediated solubilization. Characterization of extracellular precipitates by SEM-EDS and XRD indicated mineral phases consistent with oxalate-associated biominerals, including zinc oxalate dihydrate (ZnC₂O₄·2H₂O), lead oxalate (PbC₂O₄), and copper oxalate hydrate (CuC₂O₄·xH₂O). These minerals represent low-solubility phases that may reduce metal mobility in the surrounding environment. In contrast, molybdenum did not precipitate under the experimental conditions, suggesting metal-specific constraints in fungal biomineralization processes. Although organic acid production was not directly quantified, identification of oxalate mineral phases supports an oxalate-associated mineralization mechanism. Overall, the results provide evidence for heavy metal solubilization and selective extracellular precipitation consistent with oxalate biomineral formation by A. aculeatus PTW4, highlighting its potential relevance to fungal-mediated bioremediation and selective bioleaching processes. Full article

Growing concern over soil degradation and the demand for sustainable solutions have driven research into remediation technologies. This study aimed to evaluate the morphological, physiological, and phytochemical responses of Larrea cuneifolia, Bulnesia retama, Plectrocarpa tetracantha, and Neltuma flexuosa seedlings exposed to mining waste contaminated soil during early developmental stages. Plants were cultivated for 90 days in soils amended with increasing concentrations of mining waste. Higher waste proportions resulted in a dose-dependent increase in metal(loid)s concentrations and soil acidification. All species survived in soils containing up to 1572.6 mg kg⁻¹ As, 25.6 mg kg⁻¹ Cu, 33.0 mg kg⁻¹ Cd, and 742.6 mg kg⁻¹ Zn. Metal(loid)s accumulation occurred predominantly in roots, reaching 1895.1 mg kg⁻¹ Zn in P. tetracantha and 2223.2 mg kg⁻¹ As in B. retama. The presence of metal(loid)s in leaf and stem tissues was confirmed by SEM-EDX analysis. Elevated MDA levels, combined with low POX and APX activities, indicated a limited antioxidant response. Additionally, the abundance of yeast and bacterial colonies increased across all soil treatments associated with the studied native species. These results demonstrate remarkable tolerance of native species to multi-metal contamination and underscore their potential for cost-effective, nature-based strategies to restore mining-impacted soils in arid regions. Full article