Abstract:

Background & Aim: Soil microbiome plays a crucial role in nutrient cycling and maintenance of soil ecosystem function. Nitrogen is a key limiting nutrient in plant growth, while the inactive nitrogen in the atmosphere cannot be directly absorbed and utilized by plants. Soil nutrition is supplemented mainly by applying urea to sustain and elevate crop yields in our country. In recent years, with the rapid development of high-throughput sequencing techniques and bioinformatics, the response of soil microbiome structure to urea application has been thoroughly studied. This study intends to review the pattern and mechanism of effects of urea application on soil microbial diversity and composition.

Progress: Urea application regulates soil microbial diversity and composition by affecting soil and plants. The threshold value of applying urea to reduce soil bacterial diversity in farmland (excluding rice and rice-wheat fields) is 200 kg N·ha^-1·yr^-1, and the threshold for reducing fungal diversity in wheat fields is lower than the threshold for bacterial diversity. The threshold value of urea response in rice field or rice-wheat rotation farmland is higher than that in other farmland types; fertilization increases the number of eutrophic bacteria and decreases the number of oligotrophic bacteria; urea application increases the relative abundance of saprophytic fungi and pathogenic fungi, and reduces the relative abundance of mycorrhizal fungi.

Prospects: We suggest that the food web in soil should be paid more attention in future research, and point out that the design of parallel primers and the use of multi-omics methods to study soil microorganisms are necessary.

Key words: soil microbial diversity, community structure, organic nitrogen, bacteria, fungi