Search Results (449)

Soil salinization severely restricts crop growth and presents a major challenge to global agriculture. In this study, a plant-growth-promoting rhizobacterium (PGPR) was isolated and identified as Proteus sp. through 16S rDNA analysis and was subsequently named Proteus sp. JHY1. Under salt stress, exogenous dopamine (DA) significantly enhanced the production of indole-3-acetic acid and ammonia by strain JHY1. Pot experiments revealed that both DA and JHY1 treatments effectively alleviated the adverse effects of 225 mM NaCl on rice, promoting biomass, plant height, and root length. More importantly, the combined application of DA-JHY1 showed a significant synergistic effect in mitigating salt stress. The treatment increased the chlorophyll content, net photosynthetic rate, osmotic regulators (proline, soluble sugars, and protein), and reduced lipid peroxidation. The treatment also increased soil nutrients (ammoniacal nitrogen and available phosphorus), enhanced soil enzyme activities (sucrase and alkaline phosphatase), stabilized the ion balance (K⁺/Na⁺), and modulated the soil rhizosphere microbial community by increasing beneficial bacteria, such as Actinobacteria and Firmicutes. This study provides the first evidence that the synergistic effect of DA and PGPR contributes to enhanced salt tolerance in rice, offering a novel strategy for alleviating the adverse effects of salt stress on plant growth. Full article

Glycyrrhiza uralensis (G. uralensis), a leguminous plant, is an important medicinal and economic plant in saline–alkaline soils of arid regions in China. Its main bioactive components include liquiritin, glycyrrhizic acid, and flavonoids, which play significant roles in maintaining human health and preventing and adjuvantly treating related diseases. However, the cultivation of G. uralensis is easily restricted by adverse soil conditions in these regions, characterized by high salinity, high alkalinity, and nutrient deficiency. This study investigated the impacts of four multistrain microbial inoculants (Pa, Pb, Pc, Pd) on the growth performance and bioactive compound accumulation of G. uralensis in moderately saline–sodic soil. The aim was to screen the most beneficial inoculant from these strains, which were isolated from the rhizosphere of plants in moderately saline–alkaline soils of the Hexi Corridor and possess native advantages with excellent adaptability to arid environments. The results showed that inoculant Pc, comprising Pseudomonas silesiensis, Arthrobacter sp. GCG3, and Rhizobium sp. DG1, exhibited superior performance: it induced a 0.86-unit reduction in lateral root number relative to the control, while promoting significant increases in single-plant dry weight (101.70%), single-plant liquiritin (177.93%), single-plant glycyrrhizic acid (106.10%), and single-plant total flavonoids (107.64%). Application of the composite microbial inoculant Pc induced no significant changes in the pH and soluble salt content of G. uralensis rhizospheric soils. However, it promoted root utilization of soil organic matter and nitrate, while significantly increasing the contents of available potassium and available phosphorus in the rhizosphere. High-throughput sequencing revealed that Pc reorganized the rhizospheric microbial communities of G. uralensis, inducing pronounced shifts in the relative abundances of rhizospheric bacteria and fungi, leading to significant enrichment of target bacterial genera (Arthrobacter, Pseudomonas, Rhizobium), concomitant suppression of pathogenic fungi, and proliferation of beneficial fungi (Mortierella, Cladosporium). Correlation analyses showed that these microbial shifts were linked to improved plant nutrition and secondary metabolite biosynthesis. This study highlights Pc as a sustainable strategy to enhance G. uralensis yield and medicinal quality in saline–alkali ecosystems by mediating microbe–plant–nutrient interactions. Full article

Soft soils, characterized by high compressibility, low shear strength, and high water sensitivity, pose serious challenges to geotechnical engineering in infrastructure projects. Traditional stabilization methods such as lime and cement face limitations, including environmental concerns and poor durability under chemical or cyclic loading. Ionic soil stabilizers (ISSs), which operate through electrochemical mechanisms, offer a promising alternative. However, their long-term performance—particularly under environmental stressors such as acid/alkali exposure and cyclic wetting–drying—remains insufficiently explored. This study evaluates the strength and durability of ISS-modified soil through a comprehensive experimental program, including direct shear tests, permeability tests, and cyclic wetting–drying experiments under neutral, acidic (pH = 4), and alkaline (pH = 10) environments. The results demonstrate that ISS treatment increases soil cohesion by up to 75.24% and internal friction angle by 9.50%, particularly under lower moisture conditions (24%). Permeability decreased by 88.4% following stabilization, resulting in only a 10–15% strength loss after water infiltration, compared to 40–50% in untreated soils. Under three cycles of wetting–drying, ISS-treated soils retained high shear strength, especially under acidic conditions, where degradation was minimal. In contrast, alkaline conditions caused a cohesion reduction of approximately 26.53%. These findings confirm the efficacy of ISSs in significantly improving both the mechanical performance and environmental durability of soft soils, offering a sustainable and effective solution for soil stabilization in chemically aggressive environments. Full article

Cadmium (Cd) contamination in rice (Oryza sativa L.) poses serious health risks for human, necessitating effective mitigation strategies. This study investigated the effects of Cd stress on iron (Fe), manganese (Mn), zinc (Zn), and Cd accumulation and translocation in rice varieties with high (MY46) or low (ZS97B) Cd accumulation capacities grown in acidic and alkaline soils. Results demonstrated that Cd stress significantly inhibited plant growth, reducing plant height, shoot biomass, and grain yield in both soil types. Cd accumulation increased in roots, shoots, and grains, while Fe, Mn, and Zn concentrations decreased markedly. Molecular analysis revealed upregulation of metal transporter genes (OsIRT1, OsNRAMP1, OsNRAMP5) and the vacuolar sequestration gene (OsHMA3) in roots under Cd exposure. The translocation factor (TF) values of Mn and Zn from root to shoot were reduced in acidic soils, whereas Mn and Zn TFs exhibited an increasing trend in alkaline soils despite Cd exposure. Furthermore, correlation analyses indicated Mn and Zn play crucial roles in suppressing Cd accumulation in both acidic and alkaline soils. These findings provide critical insights for developing soil-specific strategies to reduce Cd accumulation in rice through micronutrient management. Full article

The study examined seasonal variability in soil enzymatic activity and microbial abundance across five grassland vegetation units: Molinietum caeruleae, Alopecuretum pratensis, Arrhenatheretum elatioris, Lolio–Cynosuretum, and com. Poa pratensis–Festuca rubra. Soils under Molinietum caeruleae showed higher fungal abundance and greater plant diversity, while Lolio–Cynosuretum was notable for elevated Azotobacter spp. populations. Actinobacteria preferred soils with more organic matter, whereas Azotobacter spp. favored higher pH. A negative correlation was observed between the Shannon diversity index (H′) and heterotrophic bacterial abundance in Arrhenatheretum elatioris and with fungal abundance in com. Poa pratensis–Festuca rubra. Acid and alkaline phosphatase and catalase activities were also negatively correlated with H′. Redundancy analysis showed these enzymes were related to total nitrogen content, and enzyme activity decreased with rising soil pH. In autumn 2022, high fungal abundance coincided with a reduction in other microorganisms. Seasonal trends were evident: catalase and urease activities peaked in autumn 2023, while other enzymes were more active in spring 2022. The results emphasize the significance of seasonal shifts in shaping microbial and enzymatic soil processes, which are vital for nutrient cycling, carbon sequestration, and climate regulation. Further research is essential to guide sustainable grassland soil management. Full article

The addition of alkaline amendments is considered an important strategy to alleviate soil acidification, with profound impacts on soil nitrogen (N) transformations such as nitrification as well as greenhouse gas (GHG) nitrous oxide (N₂O) emissions. Nitrification inhibitors (NIs) have been widely recognized to effectively mitigate N₂O emissions by depressing the nitrification process. However, the effectiveness of NIs on N₂O emissions reduction under different alkaline amendments remains largely unknown, hindering our knowledge of the optimal soil acidification mitigation strategies. In this study, the effects of NIs in combination with different alkaline amendments on N₂O emissions were assessed on typical acid soils collected from four sites during a 28-day aerobic incubation experiment. Treatments included four alkaline amendments (quicklime, chicken manure, cow dung, biochar) and no amendment control, designated as CaO, CM, CD, BC, and CK, combined with a typical NI (3,4 dimethylpyrazole phosphate, DMPP) applied at 2 mg soil kg⁻¹ or non-NI applied, respectively. Both individual amendments and their combination with DMPP significantly elevated the soil pH by 4.9–64.2% compared with the CK treatment, with the effectiveness ranking as CaO > CM ≈ CD > BC. Cumulative N₂O emissions were stimulated by the individual application of CaO, CM, and CD but were reduced by BC application compared with the CK treatment. Changes in N₂O emissions were positively correlated with the responses of the net N mineralization and nitrification rates to individual amendments, which were regulated by changes in the soil pH. The suppressive effects of NI combined with individual amendments on N₂O emissions were significant in the CaO treatment with a reduction ranging from 3.3% to 60.2%, which was attributed to decreased abundances of ammonia-oxidizing bacteria (AOB). Therefore, we concluded that the combined application of CaO and DMPP could be considered as a suitable mitigation strategy for addressing soil acidification through optimized N management. Additionally, BC can serve as a supplementary practice to simultaneously improve soil fertility. These insights are crucial for developing integrated fertilization management strategies to mitigate soil acidification with low N loss risks. Full article

Agricultural production in the saline–alkaline soils of the Yellow River Delta faces persistent challenges in waste recycling and soil improvement. We developed a three-stage circular agriculture model integrating “crop straw–edible mushrooms–vegetables,” enabling simultaneous waste utilization and soil remediation within one year (two mushroom and two vegetable cycles annually). Crop straw was first used to cultivate Pleurotus eryngii, achieving 80% biological efficiency and reducing substrate costs by ~36.3%. The spent mushroom substrate (SMS) was then reused for Ganoderma lucidum and vegetable cultivation, maximizing the resource efficiency. SMS application significantly improved soil properties: organic matter increased 11-fold (from 14.8 to 162.78 g/kg) and pH decreased from 8.34 to ~6.75. The available phosphorus and potassium contents increased several-fold compared to untreated soil. Metagenomic analysis showed the enrichment of beneficial decomposer bacteria (Hyphomicrobiales, Burkholderiales, and Streptomyces) and functional genes involved in glyoxylate metabolism, nitrogen cycling, and lignocellulose degradation. These changes shifted the microbial community from a stress-tolerant to a nutrient-cycling profile. The vegetable yield and quality improved markedly: cabbage and cauliflower yields increased by 34–38%, and the tomato lycopene content rose by 179%. Economically, the system generated 1,695,000–1,962,881.4 CNY per hectare annually and reduced fertilizer costs by ~450,000 CNY per hectare. This mushroom–vegetable rotation addresses ecological bottlenecks in saline–alkaline lands through lignin-driven carbon release, organic acid-mediated pH reduction, and actinomycete-dominated decomposition, offering a sustainable agricultural strategy for coastal regions. Full article

Background/Objectives: Understanding metabolome adjustment under saline–alkaline conditions is crucial for enhancing crop tolerance capacity and ensuring food security. Although soil salinization impairs wheat seedlings’ growth, metabolome plasticity under saline–alkaline stress remains poorly understood. Here, we delved into dynamic physiological and metabolome shifts in wheat seedlings grown on SAS (saline–alkaline soil) on the 7th and 15th days post-germination (DPG). Methods: A self-developed and cultivated high-generation salt–alkali wheat variety (011) was grown on SAS and control soil, followed by comparative physiological, biochemical, and metabolomics analyses of seedlings. Results: The seedlings’ saline–alkaline stress responses were developmentally regulated with reduced growth, increasing accumulation of proline and soluble sugars, and differential antioxidant response. LC-MS-based global metabolomics analysis revealed significant metabolite profile differences, with 367 and 485 differential metabolites identified on the 7th and 15th DPG, respectively, between control and treatment. Upregulation of saccharides, flavonoids, organic acids (citrate cycle-related), phenolic acids, amino acids and derivatives, phytohormones, and sphingolipid metabolism was essential for seedlings’ growth on SAS. The key induced metabolites in seedlings grown on SAS include saccharic acid, trehalose, sucrose, glucose, L-citramalic acid, phellodendroside, scutellarin, anthranilate-1-O-sophoroside, lavandulifolioside, N-methyl-L-glutamate, etc. Up-regulated phytohormones include abscisic acid (3.8-fold, 7th DPG and 3.18-fold, 15th DPG), jasmonic acid (1.93-fold, 15th DPG), and jasmonoyl isoleucine (2.03-fold, 15th DPG). Conclusions: Our findings highlight the importance of ABA and jasmonic acid in regulating salt–alkali tolerance in wheat seedlings. Moreover, this study depicts key pathways involved in salt–alkali tolerance in wheat seedlings and unveils key DMs, offering resources for boosting wheat production on SAS. Full article

Acid rain alters soil chemistry significantly and is a key driver of heavy metal pollution. This study investigates the environmental impact of acid rain-induced heavy metal migration in the Siding Lead–Zinc mining area in south China. Tailings, surrounding soils, and riverbed sediments were examined through simulated acid rain soil column leaching experiments. Leachate parameters—including pH, redox potential (Eh), total dissolved solids (TDSs) and heavy metal concentrations—were used to develop machine learning models (Random Forest and Support Vector Machine) to quantify the influence of environmental factors on metal migration. The results showed that leachates were generally alkaline and reductive after leaching, with Cd, Pb, and Zn as the dominant migrating metals. Leachates from tailings and nearby soils exceeded safe drinking water standards, with significantly higher cumulative metal release than other samples. The RF model outperformed the SVM model in predicting heavy metal concentrations. Feature importance analysis revealed that, beyond sample characteristics, pH and Eh were critical factors driving metal migration. Zn and Cd showed strong sensitivity to these parameters, with pH and Eh contributing over 80% to their migration. The findings highlight that acid rain can enhance the solubility and migration of heavy metals, posing a serious threat to the quality of surrounding water and underscoring the requirement for effective mitigation strategies to protect the ecological environment in mining areas. Full article

Under the global climate change context, the probability of extreme flood events has substantially increased. Nevertheless, our understanding of the post-flood dynamics in wetland ecosystems, particularly regarding soil biogeochemistry and microbiota, remains limited. Therefore, soil properties, enzyme (soil acid phosphatase, soil alkaline phosphatase, soil urease and soil protease) activities, and bacterial communities were examined in four dominant vegetation communities of Shengjin Lake’s riparian zone prior to and following an extreme flooding event. Our findings reveal a notable reduction in soil fertility, including nitrate nitrogen (NO₃⁻-N), ammonium nitrogen (NH₄⁺-N), available potassium (AK), and total phosphorus (TP), following the flood across different vegetation types. Marked enhancement of four key soil enzymatic activities was observed after flooding. Although the flooding event did not alter the dominant phyla-level bacterial taxa in the various vegetation communities, it significantly reduced the structural divergence among soil bacterial assemblages. Following the flooding event, total nitrogen (TN) emerged as a direct regulatory factor mediating the influence of vegetation communities on bacterial community composition, replacing the previous role of soil urease activity. These results highlight the profound impact of extreme flooding on plant–microbe interactions and provide critical insights into the ecological consequences of such events in wetland ecosystems. Full article

Excessive tillage and chemical fertilization are the primary attributes of conventional farming and the main causes of soil degradation. This research focused on the comparative study of two tillage systems: conventional (CT) and no-tillage (NT), as well as on the effect of chemical fertilizers and different Bacillus megaterium var. phosphaticum inoculum rates (75, 100 and 125%) on soil properties. This short-term experiment was conducted under field conditions in Northeastern Romania from 2023 to 2024. Soil dehydrogenase, catalase, acid, and alkaline phosphatase activities, pH, organic carbon content (SOC), total nitrogen (TN), total phosphorus, and available phosphorus (TP and AP) were determined. Bacillus treatments generally inhibited soil enzyme activity by 0.35 to 57%, depending on the enzyme type. Under NT, activity increased by up to 59% for dehydrogenase, 43% for acid phosphatase, and 70% for alkaline phosphatase compared to the CT system. An opposite trend was found for catalase, along with a negative correlation with the other enzymes. There were positive differences in TP concentration at 125% Ecofertil + N in both CT (0.0577 ppm) and NT (0.0578 ppm) in 2023 compared to the control (0.0346–0.0374 ppm). In the same year, after the first inoculation, AP increased significantly with bacterial treatments in CT, from 32.34% (T0) to 47.94% (T4), and at crop harvest in NT in 2024, from 34.18% (T0) to 91.06% (T3). The results suggest that enzymatic activities and soil chemical properties were more influenced by soil management than the interaction between inoculated bacteria and chemical fertilizers. Full article

Although tea (Camellia sinensis)/soybean (Glycine max) intercropping is widely applied in tea gardens, the underlying mechanisms driving tea quality promotion remain largely unclear. This study explores the effects of intercropping on tea quality, soil nutrient availability, and soybean growth and analyzes their mutual relationship. Field experiments revealed that intercropping increased tea leaf water extracts, polyphenols, and amino acids by 4.36–8.99%, 14.76–15.23%, and 14.73–16.36%, respectively, across two growth stages. Furthermore, intercropping boosted organic matter, available nitrogen (N), phosphorus (P), and potassium (K) in the tea rhizosphere. Enzyme activities, including acid phosphatase, alkaline phosphatase, urease, and β-glucosidase, were also elevated in tea/soybean intercropping. In soybean, shoot and root biomass, weight and number of nodules, and N, P, and K content increased over cultivation time. Correlation analysis showed that tea water extracts and polyphenols were positively linked to soil available P and alkaline phosphatase activities. Soybean root and nodule growth were correlated with soil N and P activation and tea water extracts, indicating that soybean-mediated underground interactions drive mineral nutrient mobilization in rhizosphere, further improving tea quality. This study provides mechanistic insights into tea/soybean intercropping, offering practical implications for sustainable tea cultivation practices. Full article

The long-term post-fire recovery phase is a critical stage for forest ecosystems to progress toward regeneration and mature succession. During this process, soil bacteria exhibit greater environmental adaptability, rapidly driving nutrient cycling and facilitating vegetation restoration. This study investigated the community structure and diversity of soil bacteria during long-term recovery after forest fires in the cold temperate zone, focusing on soils from the 2000 fires in Daxing’anling. Soil samples were classified into Low (L), Moderate (M), and High (H) fire damage intensity, with bacterial community composition and diversity analyzed using Illumina sequencing technology. After long-term fire recovery, the contents of soil organic carbon, black carbon, total nitrogen, alkaline nitrogen, available phosphorus, and available potassium were significantly higher elevated (p < 0.05), and water content was significantly lower, compared with that in the control check (CK) group. Soil urease, fluorescein diacetate, soil acid phosphatase, and soil dehydrogenase activities were significantly higher, and soil sucrase activity was significantly lower in H. There was a significant difference in the Alpha diversity index among the groups. Compared with CK, the Shannon index was significantly increased (p < 0.05) in L, while both Chao1 and Shannon indices were significantly decreased (p < 0.05) in M and significantly higher in H than CK. The results of the PCoA showed that there was a significant difference in the Beta diversity of the bacterial community among the groups (R² = 0.60 p = 0.001). The dominant bacteria groups were Proteobacteria and Acidobacteriota, while Actinobacteria became the new dominant group during the long-term post-fire recovery. AP, WC, DOC, MBC, S-DHA, and S-SC were significantly and positively correlated with soil bacterial diversity (p < 0.05). The results of the co-occurrence network analysis showed that all groups were dominated by symbiotic relationships, with M having the highest network complexity and strongest competitive effects. This study found that the physicochemical properties of soils recovered over a long period of time after fire returned to or exceeded the unfired forest condition. The Actinobacteria phylum became a new dominant bacterial group, with stronger network complexity and competition, in the process of forest recovery after moderate fire. Full article

This study investigates the impact of two months of drought stress on the microbial diversity, enzyme activities and functional diversity in four agricultural soils (Gniewkowo (G); Lulkowo (L); Nieszawa (N); Suchatówka (S)) from Poland during summer season. The physicochemical parameters (pH, organic carbon, calcium carbonate, total nitrogen, nitrate, ammonium, total phosphorus and available phosphate), microbial abundance, community-level physiological profiling, and soil enzymes (acid and alkaline phosphatases, dehydrogenase and urease) were investigated at two time intervals: zero-week (T0) and the eighth week (T8). Generally, microbial enumeration showed higher bacterial populations (496.63 × 10⁴ CFU g⁻¹ dry soil) compared to actinomycetes (13.43 × 10⁴ CFU g⁻¹ dry soil), and the fungal population was the lowest (67.68 × 10² CFU g⁻¹ dry soil) at T8. Functional diversity showed a strong, statistically significant positive effect in the G, N and S sites at T8. Acidobacteriota and Actinobacteriota declined in most places, while Firmicutes, Crenarchaeota and drought-tolerant bacteria such as Gemmatimonadota exhibited resistance. The fungal communities showed site-specific responses, with an increase in drought-tolerant Mortierellomycota and Chytridiomycota and a decrease in Ascomycota and Basidiomycota, suggesting possible adaptability. Overall, the microbial populations, enzyme activity, and functional diversity were positively correlated with soil moisture content across all four investigated sites. The significance of organic matter, soil structure, and moisture retention in determining microbial resilience to drought is underscored by these changes in microbial diversity and function, which in turn affect nutrient cycling and soil ecosystem stability. The findings of our study indicate that soil biological activities in agricultural regions can be modified by a mere two months of drought. Full article

Red mud (RM) is a strongly alkaline waste residue produced during alumina production, and its high alkali and fine particle characteristics are prone to cause soil, water, and air pollution. Phosphogypsum (PG), as a by-product of the wet process phosphoric acid industry, poses a significant risk of fluorine leaching and threatens the ecological environment and human health due to its high fluorine content and strong acidic properties. In this study, RM-based cemented paste backfill (RCPB) based on the synergistic curing of PG and ordinary Portland cement (OPC) was proposed, aiming to achieve a synergistic enhancement of the material’s mechanical properties and fluorine fixation efficacy by optimizing the slurry concentration (63–69%). Experimental results demonstrated that increasing slurry concentration significantly improved unconfined compressive strength (UCS). The 67% concentration group achieved a UCS of 3.60 MPa after 28 days, while the 63%, 65%, and 69% groups reached 2.50 MPa, 3.20 MPa, and 3.40 MPa, respectively. Fluoride leaching concentrations for all groups were below the Class I groundwater standard (≤1.0 mg/L), with the 67% concentration exhibiting the lowest leaching value (0.6076 mg/L). The dual immobilization mechanism of fluoride ions was revealed by XRD, TGA, and SEM-EDS characterization: (1) Ca²⁺ and F⁻ to generate CaF₂ precipitation; (2) hydration products (C-S-H gel and calixarenes) immobilized F⁻ by physical adsorption and chemical bonding, where the alkaline component of the RM (Na₂O) further promotes the formation of sodium hexafluoroaluminate (Na₃AlF₆) precipitation. The system pH stabilized at 9.0 ± 0.3 after 28 days, mitigating alkalinity risks. High slurry concentrations (67–69%) reduced material porosity by 40–60%, enhancing mechanical performance. It was confirmed that the synergistic effect of RM and PG in the RCPB system could effectively neutralize the alkaline environment and optimize the hydration environment, and, at the same time, form CaF₂ as well as complexes encapsulating and adsorbing fluoride ions, thus significantly reducing the risk of fluorine migration. The aim is to improve the mechanical properties of materials and the fluorine-fixing efficiency by optimizing the slurry concentration (63–69%). The results provide a theoretical basis for the efficient resource utilization of PG and RM and open up a new way for the development of environmentally friendly building materials. Full article