Cereal-forage rotation facilitates the colonization of particular rhizobacteria to improve crop productivity

Cereal-forage rotation is a crucial advantageous agricultural measure to accelerate sustainable agricultural development. However, the interaction mechanisms of crop productivity with soil characteristics and soil microbiome under this rotation regime remain controversial, leading to large uncertainties in assessing the stability of agroecosystems. The aim of this study is to investigate the effects of cereal-forage rotation on the rhizosphere microbial communities, soil properties, and crop productivity as well as the complex relationships among them. To achieve this, the rhizosphere soils of maize and alfalfa were collected from a field experiment with different cropping systems (rotation and monoculture systems of alfalfa or maize) to analyze the microbial communities and further to evaluate their roles on participating in soil nutrient cycling and improving crop productivity. Cereal-forage rotation significantly affected the microbial community compositions rather than diversities in rhizosphere soils, resulting in obvious changes of interspecific interactions. The increased alterations of crop productivity were more correlated with the shifts in bacterial community rather than fungal community, which was actuated by soil pH. Some bacterial recruitment under rotations was observed, primarily showing potential phosphorus cycling and nitrogen assimilation functions. Specifically, the accumulated beneficial rhizobacterial taxa included those with potential antagonistic activities (e.g., Brevundimonas, Gemmatimonas, Lysobacter, Pseudonocardia, and Pseudomonas) and positively responding to biological anabolism (e.g., Luteolibacter, Hyphomicrobium, and Sphingomonas). Such findings reveal that cereal-forage rotation could effectively shape rhizosphere soil microbial community structure and particularly lead to the recruitment of a group of salutary rhizobacteria, which would positively provide some valuable theoretical bases for the developments of high-quality and high-yield agriculture.