Response of soil characteristics and bacterial communities to nitrogen fertilization gradients in a coastal salt‐affected agroecosystem

Abstract

AbstractUnderstanding the relationship between fertilization and soil bacterial communities in a salt‐affected environment is essential for alleviating the adverse impact of excessive salinity on soil biochemical functioning. However, how soil bacterial communities respond to consecutive fertilization across nitrogen gradients in coastal agroecosystem has not yet been clarified. We conducted a field plot experiment with four nitrogen fertilization rates (0, 150, 300, and 450 kg N hm−2 yr−1) on coastal salt‐affected soil for three consecutive years. Temporal dynamics of soil chemical and microbial properties was characterized, and soil bacterial community composition against N fertilization rates was investigated using 16S rRNA gene sequencing. Results indicated that consecutive N fertilization significantly increased soil organic carbon, total nitrogen (TN), available nitrogen (AN), available phosphorous, microbial biomass carbon (MBC), microbial biomass nitrogen and net nitrogen mineralization rate (NMR). N fertilization rates and cultivation years exhibited interactive effect on TN, AN, MBC and NMR. Soil bacterial community richness and diversity increased with the nitrogen rates. Predominant bacterial classes were Deltaproteobacteria, Anaerolineae, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Actinobacteria and Planctomycetia. Increasing nitrogen fertilization resulted in an elevation in the relative abundance of classes Alphaproteobacteria, Gammaproteobacteria, Planctomycetia and Nitrospira, and a decline in Anaerolineae, Acidobacteria_Gp6, Cytophagia, Bacilli and Acidobacteria_Gp10. Community composition of Alphaproteobacteria, Planctomycetia and Nitrospira was significantly associated with potential nitrification rate (PNR), whereas that of Actinobacteria was relevant to carbon mineralization rate. Results underlined that nitrogen fertilization improved nutrients, biochemical characteristics and metabolic activities to create more suitable bacterial microhabitats in the coastal agroecosystem.