Effects of Nitrogen Addition on Rhizosphere Soil Microbial Community and Yield of Wheat in Loess Plateau

Abstract

The soil microbial community diversity of wheat rhizosphere was affected by the amount of nitrogen fertilizer. In addition to bacterial community, ammonia-oxidizing archaea, nitrogen-fixing bacteria and denitrifying bacteria also play important roles in nitrogen cycle. At present, the microecological mechanism of its response to nitrogen application is still unclear. In this study, the rhizosphere soil microorganisms of winter wheat were used as the research object.The changes of soil bacteria, ammonia-oxidizing archaea, nitrogen-fixing bacteria and denitrifying bacteria communities under five nitrogen rates of 0 (N0), 90 (N6), 180 (N12), 240 (N16) and 300 (N20) kg N • hm -2 were studied by high-throughput sequencing technology. Among them, under N12 treatment, the Alpha diversity index of bacteria, AOA and nifH nitrogen-fixing bacteria and the Shannon and Simpson indexes of nirK denitrifying bacteria were significantly increased. N12 treatment significantly increased the relative abundance of Proteobacteria, but no significant difference was found at the nifH and nirK bacterial phyla levels. Under the high nitrogen treatment of N16 and N20, the dominant bacteria of nirK-type denitrifying bacteria increased significantly compared with N12 treatment, there was no significant difference in microbial community distribution between N20 and the control group. Therefore, the nitrogen addition under N12 treatment was most conducive to the absorption and utilization of nitrogen fertilizer by soil microorganisms. The effect of nitrogen addition on microbial community was weaker than that of soil properties and wheat yield, and nitrogen addition was significantly correlated with yield, reaching the highest yield at 300 kg•hm -2 .

Soil Microbial Biomass and Bacterial Diversity Enhanced through Fallow Cover Cropping in Rice–Fish Coculture

“…Contrary to these findings, this study observed a decrease in MBC and MBN with N addition in all cases, except for B. napus when used as a single cover crop. This decline is primarily attributed to the accumulation of soil N induced by N addition, resulting in an imbalanced C:N:P ratio [42,43], leading to a reduction in soil microbial community diversity, particularly affecting functional microbial communities related to the N cycle. Single cover cropping the cruciferous crop B. napus with N addition increased both aboveground biomass and soil MBN by meeting its high N demands.…”