Studies on the Variation of Growth and Yield among Individual Hills of Rice Plant in Mechanical Transplanting Culture

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This study was undertaken to clarify the variation of growth or characters related to the yield, yield component and yield among individual hills of rice plant in mechanical transplanting culture. Research was conducted on the early or normal season rice plants in the paddy field of experimental farm of Kochi University,and the results were summarized as follows:1. Number of seedlings per hill varied from 1 to ca.10,averaged 5 to 7,and the coefficient of variation (CV) was around 40%.2. All of the CVs in characters related to the yield, yield component and yield were less than that of number of seedlings per hill. These characters could be categirized into four groups, namely, extemely low (CV = less than 5 %), low (CV = 5-10 %), medium (CV = 10-20 %), and high (CV = more than 20 %) group, by degree of CV.3. The more the number of seedlings per hill, the more was the yield, due to the difference of maximum stem number and panicle number, but the less were the spikelet number per panicle and the mean panicle weight per stem. On the other hand, number of seedlings per hill was not markedly affected on the % of reproductive tillers and ripened grains, 1000 grain weight, and panicle ( or winnowed paddy) weight / straw weight ratio.4. CVs of yield component and yield in mechanical transplanting culture was not higher than those in hand transplanting culture, in which number of seedlings was uniformly planted in each hill. This seemed to be due to higher variation of planting depth in hand transplanting, as compared with mechanical transplanting.