Soybean-Bupleurum Rotation System Can Optimize Rhizosphere Soil Microbial Community via Impacting Soil Properties and Enzyme Activities During Bupleurum Seedling Stage

To avoid continuous cropping problems with <i>Bupleurum</i>, we screened suitable preceding crops for rotation with <i>Bupleurum</i> through different crop rotations. Therefore, the objective of this study was to find out the relationships between microbial community characteristics, soil properties, and enzyme activities under four different rotation patterns, including fallow-<i>Bupleurum</i> (CK), maize-<i>Bupleurum</i> (M), soybean-<i>Bupleurum</i> (So), and sunflower-<i>Bupleurum</i> (Su). Results indicated that under all four rotation patterns, So treatment significantly enhanced soil nutrients and enzyme activities compared to CK. So not only optimized the composition of soil bacterial and fungal communities but markedly enhanced microbial α diversity. Additionally, So exhibited high similarity in bacterial and fungal community composition with M, and featured complex symbiotic relationships within the soil microbial network. While no clear discrepancies were detected in the abundance of the top twenty metabolic pathways in the predictive functions of bacterial and fungal communities across four rotation patterns, the metabolic pathway function MET-SAM-PWY (methionine synthesis pathway) in bacterial communities and the metabolic pathway function VALSYN-PWY (valine synthesis pathway) in fungal communities were particularly prominent under the So rotation pattern. RDA suggested that soil properties (available phosphorus and pH) and enzyme activities (sucrase and alkaline phosphatase activities) were the driving forces for bacterial community composition, while soil properties (soil organic matter and available potassium) and enzyme activities (sucrase and catalase activities) regulated fungal community composition. Hence, the soybean-<i>Bupleurum</i> rotation pattern represents a cultivation practice more beneficial for the sustainable development of the bupleurum industry, which can significantly improve soil fertility and the micro-ecological environment.