The Effect of Nitrogen on Grain Yield of Hydrid Rice

The experiment was conducted in Longhai,Fujian,China during 1991-1993.Results showed that the relationship between nitrogen absorbed by rice plant and amount of nitrogen fertilizer applied appeared as a curve;The nitrogen use efficiency of rice plant was decreased when the amount of nitrogen applied increased;However,both of the accumulation of dry weight and grain yield of hybrid rice showed as parabola related to the rate of nitrogen applied;The optimum rate of nitrogen for hybrid rice in Longhai was about 130-144 kg N/hm2;The nitrogen contain in leaf at different growing stages was an important index for obtaining higher grain yield of hybrid rice.Those indexes were 4.3%-4.5%,3.7%-4.1%,2.8%-2.9% and 1.4%-1.5% at tillering,panicle initiation,heading and maturing stage,respectively.