1994 Volume 63 Issue 3 Pages 452-459
To elucidate the effect of the number of seedling per hill on yield components and yield, rice plants cv. Nipponbare and Hourei were transplanted at three levels (1, 4, and 7) and two levels (4 and 7) of the seedling number per hill in 1984 and 1985, respectively. The hill density was at two levels and the amount of fertilizers was at one or three leves. The tillering stage was divided into three or four periods and the percentage of fruitful culms and panicle characteristics were investigated in each period. In the higher seedling number per hill, the number of panicles per square meter was larger, but the number of spikelets per panicle and the percentage of ripened grain were smaller. The 1000-kernel-weight was not affected by the seedling number per hill. In every tillering period, the number of spikelets per panicle, the percentage of ripened grains and the percentage of fruitful culms showed a significant positive correlation with the diameter of the first elongated internode at the base at harvesting time. A highly negative correlation was found between the sum of the number of culms at the emergence of a tiller and the number of tillers which emerged in the same tillering period, and diameter of the first elongated internode of tillers at harvest time. The degree of the diameter decrease for the increase of sum of culms and tiller in the higher hill density was larger than the degree of diameter decrease in the lower density. The increase of the number of culms per hill decreased the rate tillering emergence, and leaf blades with a high seedling number were light green in colour. These results imply that the high seedling number per hill induces a large culm number per hill and the small growth of a culm reduces the spikelets per panicle, the percentage of ripend grains and the percentage of fruitful culms. Finally, a high seedling number per hill lowers the grain yield. The rice plant responses to three cultural factors are discussed in terms of competition in a hill.
