Long-term intercropping shaped soil bacterial microbiome composition and structure of maize fields in a semiarid region

Intercropping has gained attention for its potential to enhance soil health and increase crop yields in agroecosystems, in which soil microbial community play a key regulatory role. Bacteria is critical for a variety of soil biological processes, so promoting the understanding of soil microbiome within bacteria can improve the agricultural management practices. Here, the responses of soil bacterial community composition, functions, and assembly to long-term intercropping were assessed using 16S rRNA gene sequencing in the mountainous area of Southern Ningxia, spanning approximately 10 years until summer 2022. The experiment comprised three field treatments: maize monoculture (MM), intercropping of maize and potato (MP) and intercropping of maize and soybean (MS). The results showed that intercropping altered the relative abundance of major phyla and genera, and life-history strategies, mainly influenced by microbial biomass carbon and enzyme activities. The ratio of K- to r-strategy bacteria showed a trend of MP (0.77) > MM (0.76)> MS (0.56). Soil bacterial community structure of MP and MS was significantly different and similar to that of MM, respectively. Bugbase and PICRUSt2 analysis predicted the phenotype and metabolic pathways of soil bacterial community in maize fields, revealing that maize-legume intercropping increased the oxygen tolerance of soil bacteria. Moreover, intercropping enhanced the co-occurrence network complexity and the roles of homogeneous selection and drift, while bacterial community assembly was mainly driven by stochastic processes in MM (62.32 %), MP (60.68 %), and MS (59.17 %) soils. A variety of complex factors strongly governed bacterial community and assembly processes, such as soil nutrient elements and moisture. In brief, the study revealed the effect of intercropping on soil bacterial community, contributing to the further understanding of agricultural management practices.