On the yielding efficiency of Japanese rice varieties, : yield per tan, and average yield per tan of prefecture,

[摘要] 1. This report is one of the series of the writer's reports concerning "The yielding efficiency of Japanese rice variety" and the writer will relate here on the yield per tan of paddy rice varieties in Japan, andthe average yield per tan of each prefectures. 2. 43192 agronomic varieties of paddy rice of Japan are investigated. The minimum of yield per tan is 0.1 koku, and the maximum 4.5 koku, the mode being 2.70 koku, the mean 2.6088 koku, and σ 0.535 koku. The distribution is of a very typical monomodal asymmetrie curve, the center of the gravity of the curve inclines to the right a little, and the skewness is -17.3%. 3. The distribution curves of the yield per tan of rice varieties in every prefecture presents a typical monomodal asymmetric curves, and the centers of gravity inclines to the right a little. The minimum of the mean of the curves are 2.093 koku in Kochi, 2.110 koku in Tochigi, 2.196 koku in Tokyo, etc. The maximum of the mean of the curves are 3.43 koku in Yamagata, 3.177 koku in Ehime, 3.069 koku in Nagano, etc. These numbers are calculated by the means of about a thousand varieties. And these numbers may be estimated as the yielding efficiency of the respective localities. 4. For the cause of the difference of yielding efficiency in different locality, the geological difference must be most responsible. Generally speaking, the Kuroboku soil (volcanic origin, acidic humus soil) regions are small yielding, but as I could not gather the geological indexes, I report here only on the correlations between the yield per tan and the rice plant charactors and the correlations between the yield per tan and the climatic conditions. The charactors which show positive correlations with yield per tan are the stem length, the number of stem per plants, the number of stem per tubo, the average yield per tan of the prefecture, the vigorocity index I (stem length × number of stems per tubo), the vigorocity index II (stem length × number of stems per plants) the daily temperature fluctuation, the percentage of sun shine, and the latitudinal coefficient. The charactors which show almost no correlation with yield per tan are the accumulated temperature from seeding to heading, the date of heading. The charactors which show negative correlation with yield per tan are the number of days from seeding to heading, the amount of rain-fall. 5. From 1931 to 1940 the increase of the yield per tan occurred according to the straight line drawn by means of R=+0.0248t + 2.374 koku The increase of the yield per tan of the whole country occurred according to the straight line drawn by means of R=+0.0246t + 1.760 koku During these years the heading date shows no difference, the stem length diminishes (according to R = -0.611t + 97.49cm) and the number of stem per plant increases (accordingto R = +0.193t + 12.93 hon 6. The yearly correlation coefficient between the yield per tan of each prefecture and the heading date shows an interesting result. In Tohoku province, e. i. Aomori, Iwate, Akita, etc. the coefficients are distinctly negative, and in Tokai-Kinki regions, e. i. Aichi, Shiga, Kyoto etc. these are distinctly positive. The correlations between the yield per tan and the stem length are generally positive, and that between the yield per tan and the number of stem per plant are generally positive. The correlations between the yield per tan of the experiment station and the average yield per tan of prefectures are distinctly positive except one prefecture Yamaguchi. The correlations between yield per tan and the mean temperature in April-November are generaly positive and distinct, but in the West-Southern region the correlations are uncertain. The correlations of yield per tan with the mean temperature of July, and also with the percent of sun shine are generally positive. And the correlations between the yield per tan and the amount of rain fall are generally negative. [the rest omitted]

[学科分类] 农业科学（综合）