The proliferation of beneficial bacteria influences the soil C, N, and P cycling in the soybean-maize intercropping system.

Abstract

Soybean-maize intercropping system can improve the utilization rate of farmland and the sustainability of crop production systems. However, there is a significant gap in understanding the interaction mechanisms between soil carbon (C), nitrogen (N), and phosphorus (P) cycling functional genes, rhizosphere microorganisms, and nutrient availability. To reveal the key microorganisms associated with soil nutrient utilization and C, N, and P cycling function in the soybean-maize intercropping system, we investigated the changes in soil properties, microbial community structure, and abundance of functional genes for C, N, and P cycling under soybean-maize intercropping and monocropping at different fertility stages in a pot experiment. We found that there was no significant difference in the rhizosphere microbial community between soybean-maize intercropping and monocropping at the seeding stage. As the reproductive period progressed, differences in microbial community structure between intercropping and monocropping gradually became significant, manifesting the advantages of intercropping. During the intercropping process of soybean and maize, the relative abundance of beneficial bacteria in soil rhizosphere significantly increased, particularly Streptomycetaceae and Pseudomonadaceae. Moreover, the abundances of C, N, and P cycling functional genes, such as abfA, mnp, rbcL, pmoA (C cycling), nifH, nirS-3, nosZ-2, amoB (N cycling), phoD, and ppx (P cycling), also increased significantly. Redundancy analysis and correlation analysis showed that Streptomycetaceae and Pseudomonadaceae were significantly correlated with soil properties and C, N, and P cycling functional genes. In brief, soybean and maize intercropping can change the structure of microbial community and promote the proliferation of beneficial bacteria in the soil rhizosphere. The accumulation of these beneficial bacteria increased the abundance of C, N, and P cycling functional genes in soil and enhanced the ability of plants to fully utilize environmental nutrients and promoted growth.