Influence of Maize-Soybean Rotation and N Fertilizer on Bacterial Community Composition

Abstract

In soybean flowering period, took rhizosphere soil samples from three treatments including continuous cropping soybean (soybean-soybean-soybean), maize-soybean rotation I (soybean-maize-soybean) and maize-soybean rotation II (maize-maize-soybean). Each treatment had three levels of nitrogen application including 0, 50, and 100 kg ha-1. Soil microbial community changes under maize-soybean rotation system and various nitrogen applications were investigated by the techniques of denaturing gradient gel electrophoresis (DGGE) analysis. The results showed that the biological diversity and abundance of three kinds of soil microbial community had a decline trend along with the increase of nitrogen application levels. Under high nitrogen application level (100 kg ha-1), a significant decrease in diversity and abundance of rhizosphere soil microbial communities was observed in both continuous cropping soybean system and maize-soybean rotation II system. And in maize-soybean rotation I system, there was only a slightly decrease in diversity and abundance of rhizosphere soil microbial communities. Therefore, 1-year maize in rotation with soybean (soybean-maize-soybean) can alleviate the effect of nitrogen fertilizer on rhizosphere soil microbial diversity and richness, but the effect of nitrogen application significantly changed its bacterial community structure. Maize-soybean rotation II system (maize-maize-soybean) was less affected by nitrogen fertilizer and showed relatively high stability. In addition, in those three kinds of soil, there were the categories of Acidobacteria, Proteobacteria and Firmicutes, in which, Acidobacteria and Proteobacteria were predominant.