Effects of N application strategies on N leaching loss in paddy soil and N use characteristics in different super hybrid rice cultivars

A rational nitrogen (N) application strategy effectively improves grain yield and N use efficiency (NUE) in the production of super rice (Oryza sativa L.). This study explored the effects of different N management strategies on N leaching loss in paddy soil and N use characteristics in different kinds of super hybrid rice cultivars. Two rice cultivars, Zhongzheyou 1 (ZZY1, a super rice of hybrid indica) and Yongyou 12 (YY12, a super rice of hybrid japonica), were chosen as representatives, and four N input levels (CK-0, N-135-135, N-195-195 and N-255-255 kg N ha(-1)) with three application strategies (P-1-60%:30%:10%, P-2-50%:30%:20% and P-3-40%:30%:30% with split N applied proportionally at the basal, tillering and panicle initiation stages, respectively) were set as treatments. An increase in the total N application rate and split proportion of basal fertilization resulted in higher N loss via leaching during the early growing stage of rice. Improving the split proportion of the second topdressing applied at the panicle initiation stage was beneficial to promoting the total N uptake and the amount of biomass accumulation, which ultimately enhanced the grain yield and NUE. YY12 obtained a 0.4-10.0% higher grain yield and 3.6-18.7% higher N recovery efficiency (REN) than that of ZZY1. Furthermore, YY12 showed greater adaptation at the high N level than did ZZY1, and allocating more N during the mid-late stage had a significant advantage in achieving high yield potential and improving NUE for YY12 compared to ZZY1. Thus, the results suggested that the N-255 level with the P-3 strategy was the optimal N management strategy that could optimize trade-offs between grain yield and NUE for YY12, while the N-195 level with the P-2 or P-3 strategy was more appropriate for ZZY1.