Different tillage practices change assembly, composition, and co-occurrence patterns of wheat rhizosphere diazotrophs

Tillage has a considerable effect on the soil ecosystem and its services, including microbial communities. Harnessing beneficial microbes is a sustainable way to optimizing crop management and agricultural production. Although diazotrophs play a major role in global biological nitrogen fixation, the effects of tillage on diazotrophic communities in the rhizosphere are not fully understood. In the present study, we investigated the diazotrophic community in wheat rhizosphere soil under different tillage treatments in a long-term experiment, i.e., plow tillage (considered as conventional tillage), chisel plow tillage (considered as conservation tillage), and zero tillage (considered as conservation tillage). Tillage led to a divergent distribution in the rhizosphere diazotrophic community and significant changes in community structure. Tillage caused specific responses from members/modules of the rhizosphere diazotrophic community co-occurrence network, and the relative abundance of keystone taxa was higher under conservation tillage than under conventional tillage. The increased abundance of tillage-sensitive modules under conservation tillage had a broad and significant positive correlation with rhizosphere nutrient availability, whereas the opposite was true for conventional tillage. Differences in nutrients under different tillage practices may lead to different assembly processes of diazotrophs. Overall, our findings indicate that tillage significantly affects the assembly and composition of the rhizosphere diazotrophic community, emphasizing the importance of improved substrate availability for rhizosphere diazotrophic modules under conservation tillage. This knowledge could deepen our understanding of the rhizosphere functional microbial community (e.g., biological nitrogen fixation).