Green manuring facilitates bacterial community dispersal across different compartments of subsequent tobacco

Green manure–crop rotation is a sustainable approach to protect crops against diseases and improve yield. However, the mechanism by which green manuring manipulates the crop-associated microbial community remains to be elucidated. In this study, we explored the horizontal processes of bacterial communities in different compartments of the soil–root interface (bulk soil, rhizosphere soil, rhizoplane and endosphere) of tobacco by performing a field experiment including four rotation practices, namely, tobacco rotated with smooth vetch, ryegrass, radish, and winter fallow (without green manure). Results showed that the co-occurrence networks constructed by adjacent compartments of the soil–root interface with green manuring had more edges than without green manuring, indicating dramatic microbial interactions. Green manuring increased the dispersal-niche continuum index between bulk soil and other compartments, indicating that it facilitated the horizontal dispersal of microbes. For the different green manuring practices, the neutral community model explained 24.6–27.6% of detection frequency for bacteria, and at least one compartment under each practice had a normalized stochasticity ratio higher than the 50% boundary point, suggesting that the deterministic and stochastic processes jointly shaped the tobacco microbiome. In conclusion, green manuring generally facilitates bacterial community dispersal across different compartments and enhances potential interactions among adjacent compartments. This study provides empirical evidence for understanding the microbiome assembly under green manure–crop rotation.