Abstract
Currently, it is difficult to synergistically improve rice yield and nitrogen (N) use efficiency (NUE) resulted from the overuse of N fertilizer under different rotations has become a major issue in China. This study was undertaken to optimize N application and evaluate the feasibility of reducing the amount of N fertilizer in rice crops under different rotations. Three rotations (mustard-rice, rape-rice, and wheat-rice) and different N application strategies (conventional N management and optimum N application strategies according to the Stanford equation) were tested in 2019 and 2020. The relationship between yield or NUE and N accumulation and translocation was, respectively, investigated. Correlation analyses revealed that the yield or NUE was significantly correlated (r = 0.446-0.977, P < 0.05) with the N translocation in stem-sheaths, N translocation contribution rate in blades, and N accumulation from full heading to maturity stage. These results suggest that the N application strategy should be adjusted according to different rotations in order to obtain the highest yield and the best NUE. When the N fertilizer was 105, 125, and 150 kg ha(-1), and the N fertilizer ratio all were 30:30:40 base to tiller to panicle fertilizer, rape-rice, mustard-rice, and wheat-rice rotations each achieve a synergistic increased N accumulation and translocation from full heading to maturity stage and hence, attained higher yield and NUE. The results further indicated that it is practicable to reduce the amount of N fertilizer applied in rice crops planted after rape or mustard but not when grown after wheat.