Impact of various fertilization types and application rates on Salvia miltiorrhiza quality and the composition of its root microbial community

Salvia miltiorrhiza , a widely used traditional Chinese medicine, has been extensively studied for its pharmacological properties and therapeutic applications in various medical conditions. Due to the lack of scientific fertilization guidance in agricultural cultivation, the excessive use of chemical fertilizer resulted in the decrease of the content of tanshinones in the root of S. miltiorrhiza . This study, through field fertilization trials and pot-based inoculation experiments, aims to explore the effects of fertilization type and amount on the quality of S. miltiorrhiza and the microbial communities in different ecological niches, while elucidating the mechanisms by which key strains regulate the quality of the Chinese medicinal herbs. In the current study, microbial organic compound fertilizers enhanced rhizosphere soil physicochemical properties, the diversity of rhizosphere soil bacterial community and the network complexity of rhizosphere soil fungi community, and the yield and quality of S. miltiorrhiza . The high-level (300 g/m²) microbial organic compound fertilizer application treatment (SXH) showed the most enhancement in the production of tanshinone compounds in S. miltiorrhiza . Through the structural equation modeling (SEM) analysis, soil bacterial community had the greatest impact on the production of tanshinone compounds in S. miltiorrhiza , followed by pH, organic matter, and alkaline nitrogen. Additionally, this study identified two core microorganisms, Sphingomonas daechungensis and Nitrospira japonica , in the rhizosphere soil of S. miltiorrhiza , which were related to tanshinone synthesis pathway. Inoculation with Sph. daechungensis bacterial suspension significantly enhanced both the biomass of S. miltiorrhiza and the accumulation of its active compounds. In conclusion, microbial organic compound fertilizer demonstrates superior efficacy in enhancing the quality of S. miltiorrhiza compared to chemical fertilizers. Under high fertilization rates, the core microbial species become more enriched, thereby further improving the quality of S. miltiorrhiza . This research provides a scientific basis for targeted cultivation practices aimed at producing high-quality S. miltiorrhiza . • The microbial organic compound fertilizer (MOCF) increased tanshinone compounds in Salvia miltiorrhiza . • The content of tanshinone compounds in S. miltiorrhiza with high-level MOCF application were the highest. • Compared with chemical fertilizer, MOCF increased soil alkali-hydrolyzable nitrogen and available potassium. • MOCF promoted the diversity of rhizosphere soil bacterial community. • Sphingomonas daechungensis was the core microorganisms and correlation with tanshinone synthesis pathway.