Search Results (276)

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

Eco-enzymatic stoichiometry provides a basis for understanding soil ecosystem functions, with implications for land management and ecological protection. Long-term climatic factors and human interferences have caused significant land-use transformations in the Qinghai–Tibet Plateau region, affecting various ecological functions, such as soil nutrient cycling and chemical element balance. It is currently unclear how large-scale land-use conversion affects soil ecological stoichiometry. In this study, 763 soil samples were collected across three land-use types: farmland, grassland, and forest land. In addition, changes in soil physicochemical properties and enzyme activity and stoichiometry were determined. The soil available phosphorus (SAP) and total phosphorus (TP) concentrations were the highest in farmland soil. Bulk density, pH, SAP, TP, and NO₃⁻-N were lower in forest soil, whereas NH₄⁺-N, available nitrogen, soil organic carbon (SOC), available potassium, and the soil nutrient ratio increased. Land-use conversion promoted soil β-1,4-glucosidase, N-acetyl-β-glucosaminidase, and alkaline phosphatase activities, mostly in forest soil. The eco-enzymatic C:N ratio was higher in farmland soils but grassland soils had a higher enzymatic C:P and N:P. Soil microorganisms were limited by P nutrients in all land-use patterns. C limitation was the highest in farmland soil. The redundancy analysis indicated that the ecological stoichiometry in farmland was influenced by TN, whereas grass and forest soils were influenced by SOC. Overall, the conversion of cropland or grassland to complex land-use types can effectively enhance soil nutrients, enzyme activities, and ecosystem functions, providing valuable insights for ecological restoration and sustainable land management in alpine regions. Full article

Elevational gradients in temperature, moisture, and vegetation strongly influence soil nutrient content and stoichiometry in mountainous regions. However, exactly how total, microbial, and enzymatic carbon (C), nitrogen (N), and phosphorus (P) stoichiometry vary with elevation in karst peak-cluster depressions remains poorly understood. To address this, we studied soil total, microbial, and enzymatic C:N:P stoichiometry in seasonal rainforests within karst peak-cluster depressions in southwestern China at different elevations (200, 300, 400, and 500 m asl) and depths (0–20 and 20–40 cm). We found that soil organic carbon (SOC), total nitrogen (TN), and the C:P and N:P ratios increased significantly with elevation, whereas total phosphorus (TP) decreased. Microbial phosphorus (MBP) also declined with elevation, while the microbial N:P ratio rose. Activities of nitrogen- (β-N-acetylglucosaminidase and L-leucine aminopeptidase combined) and phosphorus-related enzymes (alkaline phosphatase) increased markedly with elevation, suggesting potential phosphorus limitation for plant growth at higher elevations. Our results suggest that total, microbial, and enzymatic soil stoichiometry are collectively shaped by topography and soil physicochemical properties, with elevation, pH, and exchangeable calcium (ECa) acting as the key drivers. Microbial stoichiometry exhibited positive interactions with soil stoichiometry, while enzymatic stoichiometry did not fully conform to the expectations of resource allocation theory, likely due to the functional specificity of phosphatase. Overall, these findings enhance our understanding of C–N–P biogeochemical coupling in karst ecosystems, highlight potential nutrient limitations, and provide a scientific basis for sustainable forest management in tropical karst regions. Full article

Plant growth regulators (PGRs) enhance crop stress resistance but their roles in microbial-mediated phosphorus cycling within intercropping systems are unclear. Thus, We conducted a two-year field study using corn (Zea mays L. cv. Denghai 605) and soybean (Glycine max L. cv. Hedou 22) in fluvisols and luvisols soil according to World Reference Base for Soil Resources (WRB) standard. Under a 4-row corn and 6-row soybean strip intercropping system, three treatments were applied: a water control (CK), and two plant growth regulators—T1 (EC: ethephon [300 mg/L] + cycocel [2 g/L]) and T2 (ED: ethephon [300 mg/L] + 2-Diethyl aminoethyl hexanoate [10 mg/L]). Foliar applications were administered at the V7 stage (seventh leaf) of intercropped corn plants to assess how foliar-applied PGRs (T1/T2) modulated the soil phosphorus availability, microbial communities, and functional genes in maize intercropping systems. PGRs increased the soil organic phosphorus and available phosphorus contents, and alkaline phosphatase activity, but not total phosphorus. PGRs declined the α-diversity in fluvisols soil but increased the α-diversity in luvisols soil. The major taxa changed from Actinobacteria (CK) to Proteobacteria (T1) and Saccharibacteria (T2) in fluvisols soil, and from Actinobacteria/Gemmatimonadetes (CK) to Saccharibacteria (T1) and Acidobacteria (T2) in luvisols soil. Functional gene dynamics indicated soil-specific regulation, where fluvisols soil harbored more phoD (organic phosphorus mineralization) and relA (polyphosphate degradation) genes, whereas phnP gene dominated in luvisols soil. T1 stimulated organic phosphorus mineralization and inorganic phosphorus solubilization in fluvisols soil, upregulating regulation genes, and T2 enhanced polyphosphate synthesis and transport gene expression in luvisols soil. Proteobacteria, Nitrospirae, and Chloroflexi were positively correlated with organic phosphorus mineralization and polyphosphate cycling genes, whereas Bacteroidetes and Verrucomicrobia correlated with available potassium (AP), total phosphorus (TP), and alkaline phosphatase (ALP) activity. Thus, PGRs activated soil phosphorus by restructuring soil type-dependent microbial functional networks, connecting PGRs-induced shifts with microbial phosphorus cycling mechanisms. These findings facilitate the targeted use of PGRs to optimize microbial-driven phosphorus efficiency in strategies for sustainable phosphorus management in diverse agricultural soils. Full article

The biomass allocation patterns between aboveground and belowground are an essential functional trait for plant survival under a changing environment. The effects of arbuscular mycorrhizal fungi (AMF) communities on plant biomass allocation, particularly in degraded Festuca ovina grasslands in ecologically fragile karst areas, remain unclear. Therefore, we conducted a field investigation combined with a greenhouse experiment to explore the importance of AMF compared to bacteria and fungi for plant biomass allocation. The results showed that plant biomass in degraded grasslands exhibited allometric biomass allocation, contrasting with isometric partitioning in non-degraded grasslands. AMF, not bacteria or fungi, were the primary microbial mediators of grassland degradation effects on plant biomass allocation based on structural equation modeling. The greenhouse experiment demonstrated that the selected AMF keystone species from the field study performed according to ecological network analysis, particularly multi-species combinations, enhanced the belowground biomass allocation of F. ovina under rocky desertification stress compared to single-species inoculations, through decreasing soil pH, enhancing alkaline phosphatase (ALP) activity, and increasing the expression level of AMF-inducible phosphate transporter (PT4). This study highlights the critical role of the AMF community, rather than individual species, in mediating plant survival strategies under rocky desertification stress. Full article

Partial substitution of mineral N fertilizer with manure (organic substitution) is considered as an effective way to reduce N input in intensive agroecosystems. Here, based on a 3-year field experiment, we assessed the influence of different organic substitution ratios (15%, 30%, 45%, and 60%, composted chicken manure applied) on vegetable productivity and soil physicochemical and biochemical properties as well as microbiome (metagenomic sequencing) in an intensive greenhouse production system (cucumber-tomato rotation). Organic substitution ratio in 30% got a balance between stable vegetable productivity and maximum N reduction. However, higher substitution ratios decreased annual vegetable yield by 23.29–32.81%. Organic substitution (15–45%) improved soil fertility (12.18–19.94% increase in soil total organic carbon content) and such improvement was not obtained by higher substitution ratio. Soil mean enzyme activity was stable to organic substitution despite the activities of some selected enzymes changed (catalase, urease, sucrase, and alkaline phosphatase). Organic substitution changed the species and functional structures rather than diversity of soil microbiome, and enriched the genes related to soil denitrification (including nirK, nirS, and nosZ). Besides, the 30% of organic substitution obviously enhanced soil microbial network complexity and this enhancement was mainly associated with altered soil pH. At the level tested herein, organic substitution ratio in 30% was suitable for greenhouse vegetable production locally. Long-term influence of different organic substitution ratios on vegetable productivity and soil properties in intensive greenhouse system needs to be monitored. Full article

The utilization of the widely distributed saline–alkali lands by planting forage grasses is a hot topic. However, the promotion of plant growth remains a great challenge during the exploration of this stressful soil. While halotolerant bacteria are beneficial for plants against saline–alkali stress, their stable colonization on plant roots should be further strengthened. In this study, we investigated the effect of moss biochar on the root colonization of the exogenous halotolerant Halomonas salifodinae isolated from saline lake sediments. During the incubation with the bacteria, the biochar strongly bound the bacterium and induced biofilm formation on the biochar surface. When the biochar and the bacterium were added into the culturing soil of the forage grass Medicago sativa, the biochar remarkably assisted the root binding and biofilm formation of this bacterium on the plant roots. Under the biochar–bacterium combined treatment, the numbers of total bacteria, halotolerant bacteria, and nitrogen-fixing bacteria increased from 10^5.5 CFU/g soil to 10^7.2 CFU/g soil, from 10^4.5 CFU/g soil to 10^6.1 CFU/g soil, and from 10^4.7 CFU/g soil to 10^6.3 CFU/g soil, respectively. After 30 days of culturing, the biochar and the bacterium in combination increased the plant height from 10.3 cm to 36 cm, and enhanced the accumulation of chlorophyll a, reducing sugars, soluble proteins, and superoxide dismutase in the leaves. Moreover, the combined treatment increased the activity of soil enzymes, including peroxidase, alkaline phosphatase, and urease. Meanwhile, the levels of various cations in the rhizosphere soil were reduced by the combined treatment, e.g., Na⁺, Cu²⁺, Fe²⁺, Mg²⁺, Mn²⁺, etc., indicating an improvement in the soil quality. This study developed the biochar–halotolerant bacterium joint strategy to improve the yield of forage grasses in saline–alkali soil. Full article

Replacing partial chemical fertilizers with organic fertilizer can increase organic carbon input, change soil nutrient stoichiometry and microbial metabolism, and then affect soil organic carbon (SOC) storage. A 6-year field experiment was used to explore the mechanism of SOC storage under different ratios of manure substitution in northeast China, with treatments including chemical fertilizer application alone (nitrogen, phosphorus, and potassium, NPK) and replacing 1/4 (1/4M), 2/4 (2/4M), 3/4 (3/4M), and 4/4 (4/4M) of chemical fertilizer N with manure N. Soil nutrients, enzymatic activity, and SOC fractions were analyzed to evaluate the effect of different manure substitution ratios on SOC storage. A high ratio of manure substitution (>1/4) significantly increased soil total N, total P, total K, and available nutrients (NO₃⁻-N, available P, and available K), and the 4/4M greatly decreased the C/N ratio compared to the NPK. Manure incorporation increased microbial biomass carbon (MBC) by 18.3–53.0%. Treatments with 50%, 75%, and 100% manure substitution (2/4M, 3/4M, and 4/4M) enhanced bacterial necromass carbon (BNC), fungal necromass carbon (FNC), and total microbial necromass carbon (MNC) by 31.9–63.5%, 25.5–107.1%, and 27.4–94.2%, respectively, compared to the NPK treatment. Notably, the increase in FNC was greater than that of BNC as the manure substitution ratio increased. The increasing manure substitution significantly enhanced particulate organic C (POC) and total SOC but did not affect mineral-associated organic C (MAOC). High soil N and P supplies decreased leucine aminopeptidases (LAPs) and alkaline phosphatase activities but increased the activity ratio of β-glucosidase (BG)/(N-acetyl-glucosaminidase (NAG) + LAP). Treatments with 25% manure substitution (1/4M) maintained maize and soybean yield, but with increasing manure rate, the maize yield decreased gradually. Overall, the high ratio of manure substitution enhanced SOC storage via increasing POC and MNC, and decreasing the decomposition potential of manure C and soil C resulting from low N- and P-requiring enzyme activities under high nutrient supplies. This study provides empirical evidence that the rational substitution of chemical fertilizers with manure is an effective measure to improve the availability of nutrients, and its effect on increasing crop yields still needs to be continuously observed, which is still a beneficial choice for enhancing black soil fertility. Full article

Soil enzymes secreted by microorganisms play a key role in carbon (C), nitrogen (N), and phosphorus (P) metabolism in soil organic matter. As major drivers of climate change, warming and nitrogen addition affect soil physicochemical properties and enzyme activity, but their combined effects on these parameters across different soil aggregate size scales in desert steppes remain unclear. This study used a 2 × 2 factorial split-plot design (control; warming; nitrogen addition: warming + nitrogen addition) conducted from 2006 in Inner Mongolia’s desert steppe. Soil samples were collected in 2018–2019, and aggregates were fractionated into >2000 μm, 250–2000 μm, and <250 μm sizes using a modified dry-sieving method. Physicochemical properties and enzyme activities were measured. Our results show that warming significantly reduced the total nitrogen (TN) and organic carbon (SOC) content in aggregates, while nitrogen addition significantly decreased the pH value in aggregates but had no significant impact on other soil nutrient content indicators. For soil enzyme activity, warming significantly reduced the activity of Urease and Alkaline Phosphatase (ALP) in soil aggregates, and nitrogen addition significantly reduced the activity of Urease, ALP, and β-glucosidase (BG) in aggregates. However, the size of the aggregates had a significant impact on the activity of Urease and BG. The influence of soil physicochemical properties on different enzyme activities varied across different years. These findings indicate that under the global change scenario, the physicochemical properties and enzyme activity of desert steppe soils are affected by warming and nitrogen addition to varying degrees, and the impact of these two factors shows significant differences across different years. Moreover, the interactive effects of warming and nitrogen addition did not simply result in an additive effect influenced by single factors. Full article

Microplastics (MPs) and cadmium (Cd) in the soil environment are expected to pose a serious threat to agricultural production. However, the effect of the interaction between them on the soil–plant system and the mechanism of MPs on plant Cd uptake are still unclear. Therefore, the effects of different concentrations of polyethylene (PE-MPs, 0, 1.0% and 2.0%), alone or combined with Cd, on soil properties, plant growth and Cd uptake were investigated through pot experiments. The results showed that the single contamination of MPs and Cd and their interaction (MPs + Cd) significantly decreased soil moisture and pH; however, it increased soil organic matter (SOM) and total nitrogen (TN). Soil urease and catalase activities were significantly decreased and sucrase and alkaline phosphatase activities were increased with or without Cd addition. The exposure of PE and Cd, alone or combined, significantly and negatively affected plant biomass, photosynthetic parameters, and caused oxidative damage to plants, and the overall toxicity to plants increases with the increase in PE concentration. Moreover, co-pollution causes greater plant toxicity than the individual pollution of PE or Cd. Plants can resist oxidative stress by increasing superoxide dismutase (SOD) and peroxidase (POD) activities. The heat map showed that soil environmental factors were significantly correlated with plant growth; and the results of redundancy analysis (RDA) indicated that for plant physiological characteristics, soil properties under PE, alone or co-contaminated with Cd, explained a total of 85.77% and 97.45%, respectively. This indicated that the alteration of the soil microenvironment is the key factor influencing plant growth. The results of the partial least squares path model (PLS-PM) indicated that plant oxidative damage and biomass had significant positive and negative direct effects on plant Cd uptake, respectively. The linear model of relative importance (%) further revealed in depth that soil moisture (relative importance: 33.60%) and plant biomass (relative importance: 20.23%) were, respectively, regarded as the most important soil environmental factors and plant indicators affecting their Cd uptake. This study provided theoretical support for assessing the risks of MPs and Cd co-pollution to agricultural ecosystems. Full article

Saline–alkali land is a critical factor limiting agricultural production and ecological restoration. Utilizing salt-tolerant plants for bioremediation represents an environmentally friendly and sustainable approach to soil management. This study employed the highly salt-tolerant crop Portulaca oleracea L. cv. “Su Ma Chi Xian 3” as the test material. A plot experiment was established in coastal saline soils with planting P. a- oleracea (P) and no planting (CK) under three blocks with the different salt levels (S1: 2.16 g/kg; S2: 4.08 g/kg; S3: 5.43 g/kg) to systematically evaluate its salt accumulation capacity and effects on soil physicochemical properties. The results demonstrated that P. oleracea exhibited adaptability across all three salinity levels, with aboveground biomass following the trend PS2 > PS3 > PS1. The ash salt contents removed through harvesting were 1.29, 2.03, and 1.74 t/ha, respectively, in PS1, PS2, and PS3. Compared to no planting, a significant reduction in bulk density was observed in the 0–10 and 10–20 cm soil layers (p < 0.05). A significant increase in porosity by 9.72%, 16.29%, and 12.61% was found under PS1, PS2, and PS3, respectively, in the 0–10 cm soil layer. Soil salinity decreased by 34.20%, 50.23%, and 48.26%, in the 0–10 cm soil layer and by 14.43%, 32.30%, and 26.42% in the 10–20 cm soil layer under PS1, PS2, and PS3, respectively. The pH exhibited a significant reduction under the planting treatment in the 0–10 cm layer. A significant increase in organic matter content by 13.70%, 12.44%, and 13.55%, under PS1, PS2, and PS3, respectively, was observed in the 0–10 cm soil layer. The activities of invertase and urease were significantly enhanced in the 0–10 and 10–20 cm soil layers, and the activity of alkaline phosphatase also exhibited a significant increase in the 0–10 cm layer under the planting treatment. This study indicated that cultivating P. oleracea could effectively facilitate the improvement of coastal saline soils by optimizing soil structure, reducing salinity, increasing organic matter, and activating the soil enzyme system, thereby providing theoretical and technical foundations for ecological restoration and sustainable agricultural utilization of saline–alkali lands. 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 rhizosphere serves as a critical interface for plant–soil–microorganism interactions. Rhizosphere soil refers to the soil directly adhering to root surfaces, while non-rhizosphere soil denotes the surrounding soil not in direct contact with roots. This study investigated the characteristics of soil microbial community structure, diversity, and enzyme activity dynamics in both rhizosphere and non-rhizosphere soils of Salix cupularis (shrub) across different restoration periods (4, 8, 16, and 24 years) in alpine sandy lands on the eastern Qinghai–Tibet Plateau, with unrestored sandy land as control (CK), while analyzing relationships between soil properties and microbial characteristics. Results demonstrated that with increasing restoration duration, activities of sucrase, urease, alkaline phosphatase, and catalase in Salix cupularis rhizosphere showed increasing trends across periods, with rhizosphere enzyme activities consistently exceeding non-rhizosphere levels. Bacterial Chao1 and Shannon indices followed similar patterns to enzyme activities, revealing statistically significant differences between rhizosphere and non-rhizosphere soils after 8 and 24 years of restoration, respectively. Dominant bacterial phyla ranked by relative abundance were Actinobacteria > Proteobacteria > Acidobacteria > Chloroflexi > Gemmatimonadetes. The relative abundance of Actinobacteria exhibited highly significant positive correlations with carbon, nitrogen, phosphorus, and enzyme activity indicators, indicating that Salix cupularis restoration promoted improvements in soil physicochemical properties and nutrient accumulation, thereby enhancing bacterial community diversity and increasing Actinobacteria abundance. These findings provide fundamental data for restoration ecology and microbial ecology in alpine ecosystems, offering a scientific basis for optimizing ecological restoration processes and improving recovery efficiency in alpine sandy ecosystems. 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