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

研究了机插条件下水稻单穴间生长发育及产量相关性状、产量构成因素和产量的变异。本研究以高知大学实验农场稻田的早季稻和常规稻为研究对象，主要研究结果如下：1。每穴苗数1 ~ 10株，平均5 ~ 7株，变异系数（CV）在40%左右.与产量、产量构成因素和产量相关性状的变异系数均小于穴苗数。根据变异程度，这些性状可分为极低（CV = 5%以下）、低（CV = 5- 10%）、中（CV = 10- 20%）和高（CV = 20%以上）4类.每穴苗数越多，产量越高，但每穗颖花数和每茎平均穗重越低，这是由于最大茎数和穗数的差异造成的。每穴苗数对生殖分蘖率、结实率、千粒重、穗（或筛出稻谷）重/草重比的影响不显著.机插栽培的产量构成因素和产量变异系数均不高于每穴均匀栽苗的手插栽培。这似乎是由于手插的种植深度变化较大，与机械移栽相比。

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.