Effect of Planting dates and N levels on N concentration in the leaf, grain yield and N uptake by hybrid rice

An experiment was conducted to find out grain yield, nitrogen concentration in the third leaf and nitrogen uptake by hybrid rice under different planting dates and nitrogen levels during 1999 and 2000. The hybrid rice planted on July 5 or 20 produced significantly higher nitrogen concentration in the third leaf, grain yield and nitrogen uptake by both grain and straw. The delayed planting between August 5 or 20 significantly reduced these crop parameters. The reduction in grain yield was to the extent of 14.06 and 28.23%, respectively compared with planting of July 5. Number of effective tillers, grains panicle-1, test weight, grain yield, N concentration in third leaf at different stages, nitrogen concentration and uptake by grain and straw increased significantly with increasing levels of nitrogen from 50 to 150 kg N ha-1. Highest R2 value has been observed for regression equation between N concentration in third leaf at 60 DAT and grain yield.