EN
The application of nitrogen fertilizers can improve the soil environment and influence the nutrition and quality of plants; there are also significant impacts of soil types on soil microbial communities. Research on the coupling effects between the rates of nitrogen fertilizer and the soil types on soil microbial metabolic activities under field conditions are currently lacking. In this study, we investigated the effect of five different N fertilization rates on three types of soils (meadow black, alluvial, and sandy soil) that were over 8-year-long planted maize. Illumina Miseq sequencing methods were used to characterize the soil microbial communities. Real-time PCR were adopted to calculate the relative abundance of N, C, and P-cycling functional microbial. Results indicated that different N rates can significantly change soil available nutrients and effectively reduce soil pH. The structure of the soil bacterial communities and diversity did not change after the fertilization of N during the study period. However, it can be found that soil types can substantially influence the structure of bacterial communities in soil, meanwhile, there was a significant correlation between pH and the composition of bacterial communities. Although the composition of the soil microbial community did not influence the fertilization rate of N, they can be indirectly affected by pH. There was significant difference (P<0.05) in the relative abundances of the nutrient cycling functional genes of the rhizosphere soil under different nitrogen levels, with nitrogen application and soil type the main influencing factors. The results showed that the excessive application of N fertilizer did not increase the yields of maize, thus it is important to investigate the reasonable fertilization rates of N fertilizer to protect the ecological balance of crop soils.