Altering microbial community for improving soil properties and agricultural sustainability during a 10-year maize-green manure intercropping in Northwest China

Maize is a crop that is cultivated worldwide. The Hexi Oasis is one of the most important areas for high-yield maize seed production in China. Green manure, a plant fertilizer, has great potential for increasing crop yield and agricultural sustainability. However, the role of microorganisms in soil health and the microbiological mechanism of green manure in improving soil fertility and crop production in the Hexi Oasis area remain unknown. The effects of maize-green manure intercropping on the soil microbial community structure and diversity and the mechanism of soil improvement were investigated in a 10-year field experiment. The study revealed that microbial phylotypes were grouped into four major ecological clusters. Module #2 is a soil core ecological cluster enriched with many plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi. The application of green manure led to significantly increased soil pH, nutrient contents, and enzyme activities, and significantly reduced the relative abundance of potential plant pathogens compared with monocropping, which should ensure high and stable maize yield under long-term continuous cropping. It also increased the economic benefits by 56.39% compared with monocropping, owing to the additional products produced by the green manure. These improvements were associated with changes in the microbial community structure and activity, consistent with the structural equation model results. Therefore, soil microorganisms are the key drivers of the potential benefits of maize-green manure on agricultural sustainability.