Studies on Key Components for Obtaining High Grain Yield of Hybrid Rice

The results indicated that, the annual averaged yield of hybrid rice with double cropping in Longhai was 15.6～17.6t/hm2. Among the components, the total grain number per unit area was the most important to the yield of high yielding field,and the panicle number was the most im-portant to total grain number per unit area. In high yielding condition, the modle of heading num-ber appeared “1+3+7”,i.e. under the condition of planting 25 hills in 1 m2 and one hill with one seedling, each hill will produce one main stem head, 3 tillering heads emerged during seedling peri-od and 7 tillering heads during early tillering period. More than 95% tillers emerged during seedling period was able to grow to heading. The effective tillers emerged in field-growing period were the ones emerged with the growth of first 4 leaves after transplanting, The end of effective tillering in field was found at the period when 2.0～3.5 leaves emerged before maximum tiller-ing. The remainder of leaf age after maximum tillering was 2.0～2.5 leaves, which was equal to the duration from secondary branch differentiation to spikelet differentiation.