Effect of conservation tillage on the abundance and diversities of soil diazotrophic communities in different soil layers of Mollisol

Due to the continuous high-intensity utilization in recent decades, the Mollisol fertility in Northeast China has declined.Conservation tillage is a good alternative to prevent soil degradation, which alters the abundance and diversity of soil microorganisms; however, the impact of conservation tillage on soil diazotrophic community in Mollisol of Northeast China is still unclear.We conducted an experiments including 15-year no tillage (NT) and conventional tillage (CT) treatments, and analyzed the differences in abundance, diversity and composition of soil diazotrophic community in 0~5 cm and 5~20 cm soil layers of Molloisols in Northeast China.The result showed that Proteobacteria was the most abundant phyla while Bradyrhizobium was the most abundant genus.Tillage and soil depth had no significant effects on the copy number of nifH gene, Chao 1 and Shannon index.PCA analysis showed that there were significant differences in the diazotrophic communities between NT and CT.Soil bulk density (BD) was significantly correlated with PC1.Mantel test revealed that soil diazotrophic community was significantly correlated with soil BD.The results showed that NT changed the community composition of soil diazotrophic by affecting soil BD.The study deepens our understanding of the impact of tillage regime on soil diazotrophic community and provides a theoretical basis for the application of conservation tillage in Mollisol zone of Northeast China.