Long-term Continuous-cropping System Altered the Microbial Communities and Nutrient Cycles in Karst Agroecosystems

Abstract Purpose Understanding the response of microbial communities and their potential functions is essential for the long-term continuous-cropping karst agroecosystems. However, there are few studies on the interaction between soil physicochemical factors and microbial community dynamics in karst agroecosystems under long-term continuous-cropping conditions. Methods We investigated the physicochemical properties, metabolites, and microbial diversity of rhizosphere soils in which tobacco was cropped continuously for 0, 5, and 20 years. Results Compared with CK, the bacterial diversity significantly increased and then decreased with the duration of continuous cropping. In addition, the fungal diversity increased significantly, indicating that the change in fungi may shift the nutrient cycles of continuous-cropping karst agroecosystems. Soil pH and the contents of available phosphorus (AP) and alkali-hydrolyzable nitrogen (AN) were the key environmental factors leading to changes in the structures and functions of microbial communities in continuous-cropping soil. The metabolites released by tobacco, such as palmitic acid, 3-hydroxypropionic acid, stearic acid, and hippuric acid, reduced soil pH. Conclusion Continuous cropping system altered the ecological balance of the soil microbial communities.