Effect of Nitrogen Application Level on Head Milled Rice in Association with Source-bank Structure in Mid-season Hybrid Rice

In this paper,the relationship between the effects of nitrogen application level on head milled rice and source-sink structure at full panicle stage was investigated with 26 mid-season hybrid rice combinations.The results indicated there was a highly significant negative correlation between the head milled rice under 2 amounts of nitrogen application and in number of spikelets per panicle.The reason was that under low nitrogen application level,leaf-grain ratio,grain filling rate of the small-or middle-panicle type hybrid rice combinations was very high,so that the grain filling plumpness and the head milled rice was not high;while under the high level of nitrogen application,the leaf-grain ratio and grain filling rate was increased further,so that the grain unit weight and the head milled rice was decreased further.It suggests that the number of spikelets per panicle below 194 under seedlings were transplanted at 4.5-leaf stage,with a planting density of 19.98 cm×26.64 cm and 2 seedlings per hill.A total of 150 kg N per ha was applied during the entire growth period.This was an index for selecting variety of good quality rice in southern region of Sichuan Province,China.