Objective The aims were to investigate the effects of intercropping cover crops on the composition and diversity of soil microbial communities in black soil farmland in Northeast China, in order to provide a scientific basis for improving soil structure, upgrading soil quality and promoting the sustainable development of agriculture.

Method Through field experiments with maize (Zea mays L.) as the main crop and ryegrass (Lolium multiflorum L.) and white clover (Trifolium repens L.) as intercropped cover crops, the changes were analyzed in the composition and diversities of bacterial and fungal communities in rhizosphere and non-rhizosphere soils using 16S and ITS sequencing technologies compared to maize monoculture.

Result ① Corn intercropping cover crops significantly affected the bacterial community. Compared with corn monoculture, soil bacterial community abundance and α-diversity of intercropping treatments significantly increased (P < 0.05), and the effect of intercropping ryegrass treatments was more pronounced, and the relative abundance of Nitrospirae, Chao1 index, and Shannon index increased significantly by 17.2%, 4.5% and 1.3%, respectively. At the same time, corn-rye grass intercropping changed the dominant phyla of soil bacterial community, and ascomycetes replaced micrococcus wartyi and had the highest relative abundance (30.98%). ② Corn intercropping cover crops had less effect on fungal community, corn-rye grass intercropping changed the composition of fungal community, and the phyla of fungi were reduced relative to corn monocropping, and Trichoderma spp. were not detected. ③ Intercropping cover crops had no significant effect on the composition and diversity of inter-root and non-inter-root bacterial communities; total carbon (TC), total nitrogen (TN), pH and porosity of soil physicochemical properties had significant effects on the microbial community changes, which were closely related to the abundance and diversity of bacterial communities.

Conclusion Corn intercropping cover crops can significantly enhance the abundance and α-diversity of soil microbial communities and optimize their community composition. Among them, the effect of corn intercropping ryegrass treatment on soil microbial communities was more prominent. The results provide a reference basis for optimizing agricultural intercropping systems, promoting soil health and improving the agroecological environment.