Temporal variation of bacterial community structure and dynamics in urea-fertilized irrigated rice rhizosphere

Due to a lack of understanding of plant-microbe-soil interaction, nitrogen (N) biogeochemistry in rice ecosystems remains a mystery. Specifically, data on temporal shifts in rhizospheric microbial communities under urea fertilization in irrigated rice systems are limited. This study investigated the temporal dynamics of bacterial community structure in the rhizosphere of urea-fertilized irrigated rice. The bacterial community exhibited higher species richness and evenness following the first and second dose of urea application but declined after the third dose. The results also revealed that soil N content had the most impact on the structures of the bacterial communities. The application of urea reduced bacterial families such as Sphingomonadaceae, Nocardioidaceae, and Kineosporiaceae, related to N fixation, organic matter decomposition, nutrient solubilization and methanogenesis, indicating their sensitivity to increased N levels. Conversely, Methylocystaceae, a methene oxidizing group, was increased after urea application suggesting their ability to proliferate under these conditions. Functional annotation using the KEGG pathway revealed elevated isoquinoline alkaloid biosynthesis after N applications. The findings of this study provide a basis for uncovering the bacterial community structure in the rice rhizosphere that is influenced by N fertilizer application.