Zhengqian Ye

Coastal saline–alkali soils are valuable yet constrained by salinity and nutrient deficiency. Organic amendments are widely used, but their combined effects and trade-offs on soil properties, microbes, and rice production remain unclear. This study applied biochar, peat, and straw, alone and in all combinations, to coastal saline–alkali soil. Straw alone significantly increased rice yield, most combined treatments containing biochar or peat increased yields, but the effect was not significant. Combined treatments elevated rice N and P contents, as well as soil available K, Na, EC, SOM, and SOC within 0.053–0.25 mm aggregates, but promoted rice Na⁺ accumulation while suppressing K⁺ uptake. Soil urease and alkaline phosphatase activities were significantly enhanced by SP2 and SB3P1. Combined treatments also improved microbial richness, increasing the relative abundances of dominant chemoheterotrophy and aerobic chemoheterotrophy. Mantel analysis indicated that soil K, P, SOM, EC, urease, and catalase activity were positively correlated with rice yield, and rice P content in roots and stems also mattered. Overall, organic amendments improve soil fertility and microbial diversity but may introduce salt-related trade-offs, highlighting the need for balanced combination strategies in saline–alkali soil management.

Phosphorus (P) is an essential nutrient for rice growth, and the presence of phosphate-solubilizing bacteria (PSB) is an effective means to increase soil P content. However, the direct application of PSB may have minimal significance due to their low survival in soil. Biochar serves as a carrier that enhances microbial survival, and its porous structure and surface characteristics ensure the adsorption of Bacillus megaterium. Inoculating rice husk biochar-immobilized with Bacillus megaterium (BMB) resulted in dissolved inorganic and organic P levels of 39.55 and 31.97 mL L−1, respectively. Subsequently, rice pot experiments were conducted to investigate the response of soil microbial P mobilization and P uptake in rice to fertilizer inputs. The organic fertilizer (OF) combined with BMB treatment (MOF) showed the highest soil available phosphorus (AP) at 38 days, with a value of 7.83 mg kg−1, as well as increased the pqqC abundance while decreasing the abundance of phoD bacterial communities compared with the control. Furthermore, the bioavailable P reservoir (H2O–Pi and NaHCO3–Pi) in soil was greatly increased through the fertilizer input and microbial turnover, with the highest H2O–Pi (3.66 mg kg−1) in OF treatment and the highest NaHCO3–Pi (52.65 mg kg−1) in MOF treatment. Additionally, carbon utilization analysis was applied using the commercial Biolog system, revealing that the MOF treatment significantly increased the utilization of carbohydrates, polymers, and amino acid carbon sources. Moreover, compared to the control, MOF treatment significantly increased the shoot (0.469%) and root P (0.516%) content while promoting root development and thereby supporting rice growth. Our study demonstrates that the MOF treatment displayed higher P levels in both soil and rice plants, providing a theoretical basis for further understanding the role of biochar-based bacterial agents in rice P management.

Hexavalent chromium (Cr(VI)) contamination in soil presents significant risks due to its high toxicity to both the environment and human health. Renewable, low-cost natural materials offer promising solutions for Cr(VI) reduction and soil remediation. However, the effects of unmodified tea leaves and tea-derived biochar on chromium-contaminated soils remain inadequately understood. In this study, tea tree pruning waste was converted into biochar at various temperatures, and the impacts of both unmodified tea leaves and tea biochar on soil Cr(VI) content, chromium fractionation, and soil biochemical properties were assessed using a soil incubation experiment. The results showed that the combined treatment of tea and tea biochar produced at 500 °C reduced Cr(VI) content by up to 49.30% compared to the control. Chromium fractionation analysis revealed a significant increase in the residual chromium fraction, accounting for 32.97% of total chromium, substantially reducing its bioavailability and mobility. Soil properties were markedly improved, with notable increases in pH (14.89%), cation exchange capacity (CEC; up to 100.24%), and organic matter content (up to 167.12%) under the combined treatments. Correlation analysis confirmed that Cr(VI) content reductions were positively correlated with increases in pH, nutrient retention, and enzyme activities, highlighting their role in chromium stabilization. This study underscores the synergistic potential of unmodified tea leaves and tea biochar as an innovative, eco-friendly strategy for Cr(VI) remediation, enhancing both soil quality and heavy metal stabilization.

Objective Long-term ‘non-grain production’ utilization of cultivated land has caused severe soil acidification，which seriously restricts the safe production of grain in re-tillage land.Rational application of lime-based conditioners and biochar can effectively address soil acidification. Method A field experiment was conducted on Lei bamboo forest reforested farmland in Taihuyuan Town，Lin’an City，Zhejiang Province.A total of ten treatments were designed：no amendment（CK），three lime application levels of 1.5（L₁），3（L₂），4.5（L₃）t/hm²，three rice husk biochar application levels of 3（B₁），6（B₂），9（B₃）t/hm²，three limestone powder application levels of 3（LP₁），6（LP₂），9（LP₃）t/hm².In this study，a field experiment was conducted to study the effects of different application techniques of lime，rice husk biochar and limestone powder on soil physical and chemical properties，wheat growth and grain yield， thus providing theoretical basis and technical support for efficient acid reduction and quality improvement of acidified soil in ‘non-grain production’ re-tillage land and improvement of wheat yield. Result The application of lime and limestone powder amendments significantly increased the soil pH at the regreening stage and mature stage of wheat，and the effect was better than that of biochar amendments.Under the current experimental conditions，with the increase of lime and limestone powder dosage，the improvement effect of acid remedy also increased.The effect level of three modifiers on improving soil available nitrogen，available phosphorus and available potassium ranking from high to low was biochar，limestone powder and lime respectively.Compared with the control without amendment（CK），the three amendments of lime，rice husk biochar and limestone powder all positively contributed to the absorption of total nitrogen，total phosphorus and total potassium in wheat plants.However，the effectiveness of different amendments on nutrient absorption by wheat were different.The ability of applying biochar and limestone powder to increase the total nitrogen content of wheat was stronger than that of lime.The application of limestone powder had a better effect on the total phosphorus content of wheat，and the application of biochar had a more significant effect on the total potassium content of wheat.Moreover，the application of three amendments increased grain ear weight，1 000-grain weight and grain yield of wheat to a certain extent.The effect level of increasing wheat grain yield ranking from high to low was biochar，limestone powder and lime.The treatment with biochar application rate of 6 t/hm² had the best effect on increasing wheat grain yield，followed by the treatment with biochar application rate of 3 t/hm².Correlation analysis showed that soil available nutrients had a significant effect on wheat nutrient absorption.Among them，soil available potassium also had a significant correlation with wheat yield. Conclusion Based on the effects of soil fertility，crop yield and safety application dosage，biochar amendment was more effective than lime and limestone powder in improving the content of available nutrients in the soil of ‘non-grain production’ re-tillage land.At the same time，biochar amendment had a significant positive effect on wheat nutrient absorption and yield.Therefore，the rational application of low and medium rates of biochar is expected to provide an effective way for the healthy production of ‘non-grain’ re-cultivated soil.

To increase the efficiency of phytoremediation to clean up heavy metals in soil, assisted with alternating current (AC) electric field technology is a promising choice. Our experiments utilized the hyperaccumulator Sedum alfredii Hance and the fast-growing, high-biomass willow (Salix sp.). We investigated the efficiency of AC field combined with S. alfredii—willow intercropping for removing Cd from soils with different pH values. In the AC electric field treatment with S. alfredii—willow intercropping, the available Cd content in acidic soil increased by 50.00% compared to the control, and in alkaline soil, the increase was 100.00%. Furthermore, AC electric field promoted Cd uptake by plants in both acidic and alkaline soils, with Cd accumulation in the aboveground increased by 20.52% (P < 0.05) and 11.73%, respectively. In conclusion, the integration of AC electric fields with phytoremediation demonstrates significant favorable effectiveness.

Magnesium plays a crucial role in plant physiological processes. However, the specific mechanisms underlying the response of tea plants to altered magnesium nutrition under acid stress remain unclear. This study investigates how root environment acidification impacts tea seedlings and the role of magnesium (Mg) in mitigating these effects. We examine varying pH and Mg levels’ influence on tea seedlings’ resistance to abiotic stress, focusing on antioxidant capacity and nutritional content. In a hydroponic experiment, we varied root pH (3.5, 5.0, 6.5) and Mg concentrations (0.01, 0.4, 0.8 mM), assessing parameters like antioxidant capacity, peroxidative damage, and nutritional content at 1, 7, 15, and 30 days post treatment. Root environment acidification and Mg deficiency worsened peroxidative damage in tea plant leaves and roots. Increased Mg supplementation enhanced antioxidant enzyme activity, reducing malondialdehyde and mitigating oxidative damage from root environment acid stress. Under acid stress, 0.8 mM Mg significantly increased tea leaf polyphenols, amino acids, and water-soluble extracts. Mg notably boosted chlorophyll content, surpassing lower Mg levels at pH 5. Additionally, Mg reversed root vitality inhibition induced by acid stress, leading to increased nitrogen, potassium, and Mg concentrations in leaves, promoting balanced nutrient absorption. Mg supplementation is crucial for enhancing tea plant antioxidant capacity, alleviating growth inhibition from root-environment acid stress, and improving chlorophyll content and root vitality, highlighting Mg’s significance in tea cultivation and broader agricultural practices.

This study investigates how root environment acidification impacts tea seedlings and the role of magnesium (Mg) in mitigating these effects. We examine varying pH and Mg levels' influence on tea seedlings' resistance to abiotic stress, focusing on antioxidant capacity and nutritional content. In a hydroponic experiment, we varied root pH (3.5, 5.0, 6.5) and Mg concentrations (0.01, 0.4, 0.8 mM), assessing parameters like antioxidant capacity, peroxidative damage, and nutritional content at 1, 7, 15, and 30 days post-treatment. Root environment acidification and Mg deficiency worsened peroxidative damage in tea plant leaves and roots. Increased Mg supplementation enhanced antioxidant enzyme activity, reducing malondialdehyde and mitigating oxidative damage from root environment acid stress. Under acid stress, 0.8 mM Mg significantly increased tea leaf polyphenols, amino acids, and water-soluble extracts. Mg notably boosted chlorophyll content, surpassing lower Mg levels at pH 5. Additionally, Mg reversed root vitality inhibition induced by acid stress, leading to increased nitrogen, potassium, and Mg concentrations in leaves, promoting balanced nutrient absorption. Mg supplementation is crucial for enhancing tea plant antioxidant capacity, alleviating growth inhibition from root environment acid stress, and improving chlorophyll content and root vitality, highlighting Mg's significance in tea cultivation and broader agricultural practices.

This study explored the effects of soil acidification on degradation of Chinese hickory forest under field experimental conditions. Responses of plant nutrient absorption and non-targeted metabolomics based on LC-MS were analyzed to understand the mechanisms of Chinese hickory plant to acid resistance and susceptibility. In this field experiment, Chinese hickory plants were treated with CK (T1, control), nitrogen application (urea) (T2), and aluminum application (aluminum sulfate) (T3). Results showed that Al is the key toxic factor of acidification of soils planted with Chinese hickory. T2 and T3 treatments significantly inhibited absorption of nutrient elements (N, P, K, Ca, Mg, Cu, B and Zn) by Chinese hickory (except N in T2). The metabolomics data analysis showed that there were differences in plant metabolites between the experimental group (T2 and T3) and the control (T1), including p-coumaroyl quinic acid, chlorogenic acid, catechin, (+) germacrene A, myricetin 3-galactoside, and neoglucobrassicin. These metabolites may be the main regulators of Chinese hickory to soil acid stress or related to the effect of soil acidification on Chinese hickory resistance. KEGG metabolic pathway enrichment analysis showed that these differential metabolites were mainly enriched in four metabolic pathways: Flavonoid biosynthesis, Phenylpropanoid biosynthesis, Tyrosine metabolism, Stilbenoid, diarylheptanoid, and gingerol biosynthesis. This study provides a reference for metabolomics studies in Chinese hickory.

Heavy metal contamination to soil is tricky due to its difficult removal, long retention time, and biomagnified toxicity. The green and low-cost phytoremediation with electric field treatment and planting pattern selection is an emerging and more effective approach to remove heavy metals from soils. In this study, alternating current (AC) electric field-assisted phytoremediation was examined with different planting patterns, i.e., monoculture willow (Salix sp.), monoculture Sedum alfredii Hance, and interplanting of willow and S. alfredii. AC electric field greatly increased phytoremediation efficiency to soil cadmium (Cd) regardless of planting patterns, either single plant species of willow or S. alfredii. The Cd removal capacity of willow and S. alfredii raises apparently under 0.5 V cm⁻¹ AC electric field. Under different planting patterns of AC electric field treatment, Cd accumulation in the whole plant by interplanting was 5.63 times higher than monoculture willow, but only 0.75 times as high as monoculture S. alfredii. The results showed that AC electric field-assisted interplanting of willow and S. alfredii is a promising remediation technique for efficiently clean-up Cd-contaminated soil.