Effects of long-term nitrogen application on soil bacterial community structure and analysis of driving factors in black soil farmland

In this study, we selected three different N fertilization treatments in a 21-year long-term fertilization experiment to investigate the characteristics of soil bacterial community structure under different N fertilization conditions, and to reveal the main biotic and abiotic driving factors for the changes in the community structure. The results show that the application of nitrogen fertilizer significantly affects the soil bacterial community composition, increases the relative abundance of Proteobacteria by 21.9% - 24.3%, but decreases the relative abundance of Acidobacteriota and Gemmatimonadota by 6.4% -7.5% and 12.5% - 14.8%, respectively. At the genus level, application of nitrogen fertiliser significantly reduces the relative abundance of the genera RB41, Latescibacterota, g_Gemmatimonadaceae, Subgroup_7, MB-A2-108, significantly increases the relative abundance of the genera o_Acidobacteriales and Candidatus_Solibacter. Nitrogen fertiliser application has little effect on the Alpha diversity of the soil bacterial community, but significantly affects the Beta diversity of the soil bacterial community. Soil bacterivores and environmental factors affect 31.9% and 11.0% of bacterial community changes, respectively. Ammonium nitrogen in the soil is the main environmental factor driving changes in soil bacterial communities, and Eucephalobus, Plectus, and Mesorhabditis are the main biotic factors driving changes in bacterial community structure at the phylum level and genus level. The study clarifies the response characteristics of soil bacterial community structure and its driving mechanism under different amounts of nitrogen fertiliser application in the Northeast Black Soil Region, which can provide a theoretical basis for the rational application of nitrogen fertiliser on farmland and the maintenance of soil ecosystem health.