Crop rotation increases Salvia miltiorrhiza growth by affecting soil microbial properties and nitrogen cycling

Long-term monoculture poses a substantial threat to the sustainable growth of Salvia miltiorrhiza. Crop rotation represents a sustainable and effective farming practice that alleviates some of the problems encountered in continuous cropping. However, few studies have investigated the changes that occur in the soil when cropping systems transition from monoculture to rotation. This study investigated plant biomass, soil physicochemical properties, and microbial community structure and functional pathways under distinct cropping systems. The rhizosphere soils of S.miltiorrhiza were sampled from three cropping systems: non-continuous cropping (SMNCC), continuous cropping (SMCC), and crop rotation (SMCR) with Nicotiana tabacum L. The results showed that continuous cropping significantly reduced the biomass of S. miltiorrhiza, while rotation with tobacco significantly increased its biomass. The soil pH and available potassium (AK) content under crop rotation were higher than those in soil under continuous cropping, while the AN content was lower. Compared with continuous cropping, rotation cropping with tobacco reshaped the soil microbial community structure, influencing taxa such as Nitrospirae and Glomeromycota. Redundancy analysis (RDA) revealed that environmental factors were strong drivers of bacterial and fungal genera. The pathways involved in nitrogen metabolism were more active in the SMCC and SMCR soil samples. Moreover, crop rotation resulted in the reduced abundance of the denitrification-related gene (nosZ), which may result in nitrogen limitation in the field. In addition, the ammonia synthesis-related genes (hcp and cynS) and metabolism-related genes (AMO, CPS1, arcC, gudB, gdhA, glnA, and GLU) exhibited significant alterations in SMCC and SMCR soils. In conclusion, this study provides valuable insights into sustainable strategies for S. miltiorrhiza cultivation.