Abstract:

We investigated the alleviation of salt-affected soil in the coastal regions of the Yellow River Delta, China, using different combinations of maize straw and biochar. The soil samples were treated for 120 days under laboratory conditions to optimize the straw and biochar combination, which would form a theoretical foundation for field application. The experiment involved six treatment conditions (T1-T5 and CK): 100% straw, 75% straw+25% biochar, 50% straw+50% biochar, 25% straw+75% biochar, 100% biochar and CK. At the end of 120 days, parameters such as changes in soil physical and chemical properties, nutrient content, soluble ion composition and soil microbial diversity were analyzed. The results showed that (1) maize straw decreased the concentration of soluble nitrogen. The release of soluble nitrogen was enhanced during incubation, and soluble nitrogen of T1-T5 and CK in the end increased by 250.51%, 81.21%, 18.19%, 32.77%, 67.55%, 64.20%, respectively, compared with the initial. (2) Maize straw increased the phosphate content of the soil. The fixation of phosphate was enhanced during incubation, and the lowest concentration was 0.99 mg·L^-1 at T1. (3) Soluble sodium decreased through the whole incubation. T3 resulted in the maximum reduction of sodium in the soil, which was 356.80 mg·L^-1. In contrast, an increase in potassium content during incubation was observed, with the maximum potassium content observed in the treatment with increased biochar addition. When the ratio of straw to biochar was >1:1, a decrease in soluble calcium and magnesium content in the soil was observed. However, with an increase in biochar treatment, an increase in calcium and magnesium content in the soil was observed. (4) Both straw and biochar increased the initial organic matter of the soil; maize straw addition enhanced the soil respiration rate. (5) Straw and biochar decreased the relative abundance of Proteobacteria and Actinobacteria. Soil microbial diversity was closely related to ion composition and electrical conductivity. However, pH, soluble nitrogen, phosphorus, and potassium had no significant effect on microbial diversity. In conclusion, the combined application of straw and biochar affected soil physical and chemical properties, ion composition and soil microbial diversity. Furthermore, T3 performed the best. The content of salt and soluble sodium in the soil reduced significantly, indicating alleviated salt stress. Our results indicate that optimal combination of maize straw and biochar effectively alleviated salt stress, reduced the risk of nitrogen and phosphorus leaching and helped maintain soil fertility.

Key words: Yellow River Delta, straw, biochar, salt-affected soil, nutrients, microbial diversity

摘要：

以黄河三角洲典型滨海盐碱土壤为对象，研究秸秆直接还田与炭化还田措施对其作用效果，筛选最佳配比，为实践推广奠定理论基础。设置6种不同处理，分别为T1（100%秸秆）、T2（75%秸秆+25%制炭）、T3（50%秸秆+50%制炭）、T4（25%秸秆+75%制炭）、T5（100%制炭）及CK（空白对照）。在120 d室内培养条件下，分析土壤基本理化性质、养分含量、水溶性盐基离子组成及土壤微生物多样性等指标的变化。结果表明，（1）秸秆降低土壤中可溶性氮浓度，培养过程增加其释放，T1—T5和CK较培养第1天的含量分别增加250.51%、81.21%、18.19%、32.77%、67.55%、64.20%。（2）秸秆增加磷酸盐质量浓度，培养过程增强磷酸盐的固持，T1最低，为0.99 mg·L^-1。（3）土壤中水溶性钠离子质量浓度在培养过程中持续下降，实验结束时，T3处理最低（356.80 mg·L^-1）。相反，水溶性钾离子的浓度不断上升，并随生物质炭添加量增加而增加。当秸秆直接还田与制炭比高于1:1配施时，土壤中的水溶性钙、镁离子含量基本呈现下降趋势；而当秸秆制炭量占优时，则与之相反。（4）秸秆和生物质炭均可增加土壤初始有机质含量，且秸秆强化土壤呼吸速率。（5）秸秆和生物质炭降低优势菌门变形菌门（Proteobacteria）和放线菌门（Actinobacteria）相对丰富度，土壤微生物多样性与离子组成及电导率关系密切，pH、可溶性氮、磷、钾含量对其没有显著影响。综上可知，不同秸秆和生物质炭配施影响土壤理化性质、离子组成及土壤微生物多样性，T3处理最佳，此处理下可显著降低土壤盐分和水溶性钠离子含量，缓解土壤盐胁迫，同时降低氮、磷的淋失风险，有利于土壤肥力保持。

关键词: 黄河三角洲, 秸秆, 生物质炭, 盐碱耕地改良, 养分, 微生物多样性