Long-term effects of nitrogen and phosphorus fertilization on soil microbial community structure and function under continuous wheat production.

Soil microorganisms play a critical role in the biosphere, and the influence of cropland fertilization on the evolution of soil as a living entity is being actively documented. In this study, we used a shotgun metagenomics approach to globally expose the effects of 50-year N and P fertilization of wheat on soil microbial community structure and function, and their potential involvement in overall N cycling. Nitrogen (N) fertilization increased alpha diversity in archaea and fungi while reducing it in bacteria. Beta diversity of archaea, bacteria and fungi, as well as soil function, were also mainly driven by N fertilization. The abundance of archaea was negatively impacted by N fertilization while bacterial and fungal abundance was increased. The responses of N metabolism-related genes to fertilization differed in archaea, bacteria and fungi. All archaeal N metabolic processes were decreased by N fertilization, while denitrification, assimilatory nitrate reduction and organic-N metabolism were highly increased by N fertilization in bacteria. Nitrate assimilation was the main contribution of fungi to N cycling. Thaumarchaeota and Halobacteria in archaea; Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Deltaproteobacteria in bacteria; and Sordariomycetes in fungi participated dominantly and widely in soil N metabolic processes.