Functional keystone drive nitrogen conversion during different animal manures composting

[Display omitted] •Significant difference in nitrogen conversion of different composting.•Functional keystone involved in the nitrogen conversion were identified.•Change in abundance of functional keystone was limited during composting.•Composting microenvironment drove functional keystone. In this study, nitrogen transformation of chicken manure (CM) and cattle dung (CD) during composting was analyzed and its related functional keystones were identified. The results showed that chicken manure showed more severe nitrogen conversion during composting. The main N conversion factors in cattle dung were nitrite nitrogen (NO2–-N) and ammonium nitrogen (NH4+-N), while the main N conversion factors in chicken manure were NH4+-N and nitrate nitrogen (NO3–-N). The nitrogen-transforming bacterial community in chicken manure was more diverse. Variations in functional keystone abundances in cattle dung tended to be confined to the cooling and maturation periods, whereas changes in chicken manure persisted throughout the composting process. Environmental factors affected the functional keystones of nitrogen transformation. This study may provide directions for regulating nitrogen conversion in animal manure composting.