Effects of Plant Density and Nitrogen Application Rate on Grain Yield and Nitrogen Uptake of Super Hybrid Rice

The nitrogen uptake, yield and its components for two super-high-yielding hybrid rice combinations, Guodao 6 and Eryou 7954 were investigated under different plant densities (15, 18, and 21 plants/m(2)) and different nitrogen application rates (120, 150, 180, and 210 kg/hm(2)). The experiment was conducted on loam soil during 2004-2006 at the experimental farm of the China National Rice Research Institute in Hangzhou, China. In these years, the two hybrid rice clearly showed higher yield at a plant density of 15 plants/m(2) with a nitrogen application rate of 180 kg/hm(2). Guodao 6 produced an average grain yield of 10 215.6kg/hm(2) across the three years, while the yield of Eryou 7954 was 9 633.0kg/hm(2).With fewer plants per unit-area and larger plants in the plots, the two hybrid rice produced more panicles per plant in three years. The highest nitrogen uptake of the two hybrid rice was at a plant density of 15 plants/m2 with a nitrogen application rate of 180 kg/hm(2). Further increasing nitrogen application rate was not advantageous for nitrogen uptake in super-high-yielding rice under the same plant density.