Integrated microbiology and metabolomics analysis reveal responses of soil bacteria and metabolic functions to different combinations of N and Zn fertilization in tea plantation

Optimal combined application of nitrogen (N) and zinc (Zn) fertilizers has potential benefits in improving N bioavailability in soil and enhancing N uptake in plants. However, the deeper understanding of the response and underlying mechanisms is not fully understood yet. In this study, we combined microbiology with non-target metabolomics to explore different combinations of N and Zn fertilization affect soil biochemical response, soil bacterial communities and metabolic functions based on 16S rRNA gene sequencing and UPLC-MS/MS platforms in tea plantation. Results showed that N fertilization and Zn-N co-fertilization significantly increased the soil total N, NH4+-N, NO3--N, MBN contents and the activities of S-UE. Results from 16S rRNA gene sequencing indicated that soil bacterial community diversity, structure and composition were also changed under different combinations of N and Zn fertilization. Bacterial taxa related to N fixation and Zn activation were enriched in soil after N-Zn co-fertilization treatment, constructing more complicated and stable soil bacterial networks. Soil metabolomics analysis showed that different combinations of N and Zn fertilization significantly altered soil metabolite spectrum, and the differential metabolites were significantly enriched to 15 main metabolic pathways. Moreover, bacteria taxa were also closely related to the accumulation of metabolites based on correlation analysis. Our findings demonstrated that optimal combined application of N and Zn plays an important role in regulating soil microbial metabolism in tea plantation, and their interactions in soil provide valuable information for understanding the underlying mechanisms of the synergistic effect between N and Zn fertilization.