Effects of Nitrogen Application Rate on Rhizosphere Microbial Diversity in Oilseed Rape (Brassica napus L.)

Nitrogen is one of the essential nutrients for rape growth and development, of which the demand is large. In order to reveal the response of rhizosphere microbial diversity on oilseed rape to the nitrogen fertilizer, four nitrogen application rates of N (170 kgN/hm(2)), N50% (85 kgN/hm(2)), N70% (119 kgN/hm(2)) and N150% (255 kgN/hm(2)) were set. The diversity and community structure of soil bacteria and fungi in seedling, flowering and mature stages of oilseed rape were analyzed based on the high-throughput sequencing technology. The results of rhizosphere soil microbial analysis showed that the dominant bacteria phyla were Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes and Cyanobacteria. The dominant fungi phyla were Ascomycota, Olpidiomycota and Basidiomycota. NMDS analysis showed that the community structure of soil bacteria and fungi changed significantly under nitrogen treatment. Cluster analysis showed that the bacteria at seedling and flowering stage had little effect under the condition of less nitrogen application, while the fungi had little effect on the rhizosphere soil microbial flora at flowering stage. At seedling stage, the diversity and richness of bacterial community in the rhizosphere of oilseed rape were lower under low nitrogen application (85 kgN/hm(2)). Bacteria and fungi in the rhizosphere soil of flowering oilseed rape maintained a higher community diversity under the condition of high nitrogen (255 kgN/hm(2)). The diversity of rhizosphere bacterial community was higher under conventional N application than under other N application.