Effect of Nitrogen Applied Before Transplanting on NUE in Rice

Nitrogen (N) application before transplanting, where N fertilizers are applied in seedling-bed and carried to the paddy field with seedlings, is a novel method proposed in this article aiming for improving nitrogen utilization efficiency (NUE) in rice. The effect of this method on mineral N distribution in the rhizosphere soil was investigated in a field experiment with a japonica variety, Ningjing 2, in seasons of 2004 and 2005. There were four levels of N applied 16 h before transplanting: zero N (N0), 207 kg ha−1 (NL), 310.5 kg ha−1 (NM), and 414 kg ha−1 (NH). The result indicated that N fertilizer before transplantation had positive effect of increasing mineral N content in the rhizosphere soil of rice. Generally, N content in the rhizosphere soil of rice tended to increase with the amount of N fertilizer before transplanting, with the NH treatment having the largest effect. Additionally, N fertilizer before transplanting had significant influence on rice NUE and grain yield. Compared with other treatments, the NM treatment showed the largest influence, with basal-tillering NUE, total NUE, and grain yield being 15%, 12%, and 529.5 kg ha−1 higher than those of N0 treatment. This result indicated that N fertilizer before transplantation had positive effect on mineral N distribution in the rhizosphere soil of rice, thus improving NUE and grain yield.