玉米-大豆轮作及氮肥施用对土壤细菌群落结构的影响

在大豆开花期分别对3个施氮水平下(0、50和100 kg hm^-2)大豆连作(大豆-大豆-大豆)、玉米-大豆轮作I (大豆-玉米-大豆)及玉米-大豆轮作II (玉米-玉米-大豆)，应用PCR-DGGE技术研究了玉米-大豆轮作及施氮对土壤细菌群落结构变化的影响。结果表明，随着施氮水平的提高，3种种植方式土壤中细菌群落多样性、丰富度均呈减少趋势。高氮处理(100 kg hm^-2)明显降低了大豆连作、玉米-大豆轮作II根际土壤细菌群落多样性及丰富度，玉米-大豆轮作I根际土壤细菌群落多样性及丰富度略有降低。玉米-大豆轮作I种植方式可减轻氮肥对其根际细菌群落多样性和丰富度的影响，但施氮明显改变了其细菌群落结构。玉米-大豆轮作II中大豆根际土壤细菌群落结构较为稳定，受氮肥影响较小。在3种种植方式的土壤中，分布着酸杆菌门、变形菌门及厚壁菌门细菌，其中前两门菌群占主导地位。

Influence of Maize-soybean Rotation and N fertilizer on Bacterial Community Composition

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.