Field experiments of winter wheat-summer maize rotation were conducted in Xushui,Hebei Province,North China Plain irrigation area,to explore the effects of dairy effluent irrigation on diversity and community structure of nir Kand nirS-type denitrifying bacteria through terminal restriction fragment length polymorphism(T-RFLP) analysis and gene sequence analysis. Five treatments were designed,including no fertilizers treatment(CK),conventional fertilization(CF)and dairy effluent irrigations with 3 fertilize...