Dynamic changes in the rhizosphere bacterial community in monoculture and intercropping maize and soybean during various crop growth stages 

Abstract Although rhizosphere microorganisms have been studied for a long time, rhizosphere microbial communities based on monoculture and intercropping soybean and maize have rarely been studied. To define the effect of crop monoculture and intercropping on soil physicochemical properties and rhizosphere bacterial communities, field experiments were conducted using maize and soybean cultivars at five different crop growth stages, including monoculture maize, monoculture soybean and maize-soybean intercropping. The rhizosphere bacterial communities were analyzed by using the 16S rRNA Illumina sequencing. The pH and soil organic matter (SOM) were the key factors affecting crop rhizosphere soil bacterial communities. The intercropping soybean-maize increased the available phosphorus (AP) content at five different crop growth stages. And the available potassium (AK) content in the intercropping soybean soil samples was higher than corresponding monoculture soil samples. The content of available cadmium (ACd) in monoculture soybean rhizosphere soil samples decreased and then increased, but the intercropping soybean soil samples indicated an opposite trend. Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria and Firmicutes were the dominant phyla in the soybean and maize rhizosphere soil samples. Crops of the same plant species showed little difference in the bacterial community diversity under the two planting modes. The results indicated the intercropping planting pattern altered the absorption of ACd in the maize and soybean soil since the S2 stage and showed a different change in different crop growth stages. And the maize-soybean intercropping system also changed the bacterial community and soil physicochemical properties.