秸秆还田配施化肥对稻-油轮作土壤酶活性及微生物群落结构的影响

秸秆还田是农业生态系统提高土壤肥力和维持作物生产力的有效管理措施.为了研究秸秆还田配施化肥对巢湖地区稻-油轮作农田土壤养分含量、酶活性和微生物群落的影响，开展连续4 a （2016~2020年）的田间定位试验，设置无秸秆+无施肥（CK）、常规施肥（F）、秸秆还田+常规施肥（SF）和秸秆还田+常规施肥减20%（SDF）这4个处理，探究不同处理下影响土壤酶活性与细菌、真菌群落发生变化的关键环境因子.结果表明，秸秆还田配施化肥较常规施肥处理能够提高土壤养分含量，SF处理的土壤养分含量最高.与F相比，SF处理的水稻季土壤有机质（OM）和全磷（TP）含量显著提高了7.94%和24.07%（P<0.05），油菜季碱解氮（AN）含量显著提高了13.62%（P<0.05）.SF较F处理的土壤磷酸酶和脲酶在水稻季显著提高了28.54%和24.13%，在油菜季显著提高了38.97%和30.70%，而SDF处理的4种土壤酶中仅脲酶活性较F处理显著提高，水稻季和油菜季分别提高了20.31%和24.33%（P<0.05）.秸秆还田对水稻季土壤细菌的Chao1和Shannon指数有所增加，油菜季则有所减少，而对真菌群落的Chao1和Shannon指数均增加.对于微生物群落结构而言，SF和SDF较F处理的变形菌门相对丰度在水稻季分别增加了8.22%和7.88%，油菜季分别增加了18.53%和5.68%.与F相比，SF和SDF处理的绿弯菌门相对丰度在水稻季分别增加了12.00%和11.25%，油菜季分别增加了15.02%和8.43%.水稻季SF和SDF处理的担子菌门较F相比相对丰度显著提高了70%和43.42%（P<0.05），油菜季SF和SDF处理的子囊菌门与F相比显著提高了69.79%和43.72%（P<0.05）.综上，秸秆还田配施化肥可提高土壤养分含量，土壤脲酶和磷酸酶对秸秆还田的响应更为敏感，稻-油轮作农田土壤的细菌群落构成发生改变主要受土壤TP和速效磷（AP）影响，而土壤OM、AN和pH则是引起真菌群落构成变化的主要环境因子，因而秸秆还田有利于提高农田土壤肥力和维护生态系统健康.

Effects of Straw Returning with Chemical Fertilizer on Soil Enzyme Activities and Microbial Community Structure in Rice-Rape Rotation

Straw returning is an effective technique for improving soil fertility and maintaining crop productivity in agro-ecosystems. The effects of straw returning, when combined with chemical fertilizer, on soil nutrients, enzyme activity, and microbial community were explored in rice-rape rotation farmland in the Chaohu Area. We carried out a 4-year field experiment (2016-2020) and set up four treatments (no straw+no fertilization, CK; conventional fertilization, F; straw returning+conventional fertilization, SF; and straw returning+conventional fertilization minus 20%, SDF) to explore the key environmental factors affecting soil enzyme activity and microbial and fungal communities. The results showed that straw returning combined with chemical fertilizer could improve soil nutrient content, with the SF treatment resulting in the highest soil nutrient content. Compared with F, the SF treatment significantly increased the organic matter (OM) and total phosphorus (TP) content of the soil, by 7.94% and 24.07%, respectively, in rice seasons (P<0.05), while the alkaline nitrogen (AN) content was significantly increased by 13.62% in rape seasons (P<0.05). Compared with F, the SF treatment also significantly increased soil phosphatase and urease, by 28.54% and 24.13% in rice seasons and 38.97% and 30.70% in rape seasons, respectively (P<0.05). Compared with F, SDF treatments significantly increased urease activity by 20.31% in rice seasons and 24.33% in rape seasons (P<0.05). The results indicated that straw returning increased both the Chao1 and Shannon indices of soil bacteria in rice seasons, whereas decreased these indices in rape seasons. However, the Chao1 and Shannon index of the fungal community increased after straw returning. In terms of microbial community structure, the relative abundance of Proteobacteria in SF and SDF treatments increased by 8.22% and 7.88% in rice seasons and 18.53% and 5.68% in rape seasons, respectively, compared with the F treatment. Compared with F, the relative abundance of Chloroflexi in SF and SDF treatments increased by 12.00% and 11.25% in rice seasons and 15.02% and 8.43% in rape seasons, respectively. Compared with F, the relative abundance of Basidiomycota in SF and SDF treatments in rice seasons increased by 70% and 43.42% (P<0.05), respectively, while ascomycetes in rape seasons increased by 69.79% and 43.72% (P<0.05), respectively. In conclusion, straw returning combined with chemical fertilizer can improve soil nutrient content. Soil urease and phosphatase were more sensitive to straw returning. The compositional changes in the bacterial community of the soil were mainly affected by soil TP and available phosphorus (AP), whereas OM, AN, and pH were the main environmental factors causing changes in the fungal community composition. Consequently, straw returning can improve soil fertility and maintain ecosystem health.