Eliciting the Response of Rhizospheric Soil Microbial Community Structure to Zinc Amendment: A Case Study of Sugar Beet Cultivation in Black Soil

In the traditional black soil growing area of sugar beet (Beta vulgaris L.) in northern China, the occurrence of soil barriers due to multiple planting of sugar beet limited it's yield improvement. Zinc (Zn) fertilization can promote sugar beet growth,; however, the regulatory mechanism of Zn on sugar beet roots and soil ecology in the long-term cultivated black soil area is still unclear. In this study, the effects of zinc application on the growth of sugar beet roots and their rhizosphere soil chemical properties and microbial characteristics were investigated in the field of black soil at harvest time. The results showed that exogenous Zn application increased the content of available Zn (DTPA-Zn), increased the microbial biomass C and N, and species diversity of bacterial communities and decreased the species diversity of fungi and the abundance of bacterial and fungal species; In particular, the bacterial abundance of Proteobacteria and Acidobacteria increased after Zn application, while Actinobacteriota and Chloroflexi decreased; the relative abundance of Basidiomycota increased and Mortierellomycota decreased. Ultimately, the incidence of sugar beet root rot was reduced by exogenous Zn application, which significantly increased the root yield and sugar content of sugar beet. Conclusively, Zn application improved the species composition and functional structure of the rhizosphere soil bacterial and fungal microbial communities, suppressed the incidence of root rot in long-term cultivated sugar beet black soils, and promoted sugar beet growth. Zinc addition was an effective means of improving the soil ecology.