Effect of Nitrogen Application on Yield and Nitrogen Utilization of Rice for Mechanized Pot-seedling Transplantation on Fields at Coastal Region

To determine the appropriate nitrogen application for mechanized pot-seedling transplanting rice cultivation in the future, a field experimentation using the high salinity tolerant super rice, Yanfeng 47, was conducted in a coastal area in Liaoning. Rice yield and nitrogen utilization under varied nitrogen fertilization were evaluated. It was found that when the basal fertilizer:first-tillering-fertilizer:second tillering-fertilizer:first panicle-fertilizer:second panicle-fertilizer was 40:12:18:16:14 was applied, the greatest grain yield of 10.79 t·hm^-2 was reached. The productivity was extremely significantly higher, with much higher panicles and spikelets and filled grain numbers per ear, than those provided by the other application modes. Its 41.90% nitrogen utilization efficiency was also significantly higher than that of other treatments. The nitrogen absorption rates of the mechanically transplanted pot-seedlings during the stages from transplanting to tillering, from tillering to jointing, from jointing to heading, and frrom heading to maturity were approximately 16:53:20:11. The amount of nitrogen absorption before the jointing was 69% of the total nitrogen absorption, and the amount of nitrogen absorbed by the reproductive growth was 31%, the ratio was coincide with that of basic-tillering to panicle of the treatment with highest yield and nitrogen use efficiency. Hence, if only one available nitrogen fertilizer was applied with a total N application rate at 240 kg·hm^-2, the ratio of basal fertilizer:first tillering-fertilizer:second tillering-fertilizer:first panicle-fertilizer:second panicle-fertilizer at 40:12:18:16:14 would be appropriate for the plant growth as well as the absorption and utilization of nitrogen for the mechanically transplanted rice in the region. Then, further demonstrations could be conducted to promote the application. Moreover, the nitrogen agronomy efficiency and the nitrogen partial factor productivity were found useful as indicators for evaluating the nitrogen utilization.