Improving nitrogen management for zero-tillage rice in China

Zero-tillage has become increasingly attractive in rice production in China.This study was conducted to determine the feasibility of two possible improved N management practices with fewer N applications in zero-tillage rice:(1)two split applications of urea at75 kg N haat mid-tillering and 45 kg N haat panicle initiation(U),and(2)a single application of cross-linked polyacrylamide-coated urea(a slow-release fertilizer)at midtillering at a rate of 150 kg N ha(PCU).Three field experiments were conducted to compare grain yield and N-use efficiency among several N treatments:a zero-N control(CK),U,PCU,a single application of urea at mid-tillering at a rate of 150 kg N ha(U),and a commonly recommended N management practice for conventional tillage rice(three split applications of urea with 75 kg N haas basal,30 kg N haat mid-tillering,and 45 kg N haat panicle initiation)(U).Treatments with N application(U,PCU,U,and U)produced 1.08–3.16 t hahigher grain yields than CK.Grain yields under both Uand PCUwere comparable to that in U.Recovery efficiency of N(RE),agronomic N-use efficiency(AE)and partial factor productivity of applied N(PFP)were increased under Uand were similar under PCUto those under U.Ushowed lower grain yield,RE,AE,and PFPthan U.These results suggest that Ucan be replaced with Uto achieve both an increase in N-use efficiency and a reduction in number of N applications and or by PCUto achieve a maximum reduction in number of N applications in zero-tillage rice production in China.