The dynamics of soil microbial community structure and nitrogen metabolism influenced by agriculture practices and rainfall

Agriculture practices, such as fertilization and cultivation, inevitably modify the soil ecological environment by altering the soil microbial community structure and the nitrogen (N) metabolism processes. The influences of rainfall combined with agriculture practices on microbial community structure and soil N metabolism were not well understood. It is important to investigate the combined effects of rainfall and agriculture practices on the soil N metabolism in varied soil layers for better agriculture management. In this paper, the effects of fertilization, cultivation as well as rainfall on N metabolism related microorganisms and key functional genes at various depths in a vegetable field were investigated. Results showed that Soil microbial community structure of 30 cm depth is more sensitive to soil properties change. Nitrogen-fixing bacteria (NFB) was promoted (from 0.07% to 1.43%) after fertilization, and cultivation shifted the dominance of NFB from Ensifer to Bacillus in 20-30 cm soil layer. Denitrifier Pseudomonas in 20 cm (from 0.93 to 5.01%) and comammox Nitrospira in 30 cm (from 3.3% to 3.82%) were promoted after rainfall. Soil C/N is a major determinant of soil N metabolism-related microorganisms. Fertilization before rainfall and cultivation at 30 cm is recommended. The findings in this paper could provide the scientific basis for better agriculture management practices.