The effect of inorganic nitrogen fertilizer forms and fertilization regimes on durum wheat bacterial and archaeal communities

Nitrogen fertilization has become an important agricultural practice. In this study, we examined, one- and seven-months post-fertilization, the bacterial and archaeal community structure of agricultural soils under durum wheat production conditions. Durum wheat was grown under two nitrogen fertilization regimes: soils not fertilized, and soils treated with two different forms of inorganic nitrogen fertilizers (urea 46% N and a mix of ammonia and urea). Fertilization affected the composition, diversity, and richness of wheat-associated microbial communities, as well as 16S rRNA gene-predicted functions and soil properties. Microbial taxa related to different processes of the N-cycle, such as the ammonia-oxidizer Nitrospira and Pseudomonadaceae were indicators of fertilized and not fertilized samples, respectively. Inorganic nitrogen fertilization negatively affected rhizosphere microbial richness and diversity, especially in urea 46% N form, but it significantly increased the relative abundance of both oligotrophic, such as Acidobacteria, and copiotrophic bacteria, such as Bacteroidetes. The fertilizer form affected many predicted gene categories involved in nitrogen metabolism and various N-cycling functions, such as nitrification and denitrification. Our results highlight that the choice of inorganic N fertilizer form and fertilization regimes impacts the durum wheat rhizosphere microbiome and soil characteristics, and that this effect could extend to the following cropping cycle.