Statistical Researches on the Bad Harvest of Rice in Japan : II. Futher Discussional Studies for the Bad Harvest(1)

[摘要] The author investigated the relations between annual rice yields per unit area in Aomori Prefecture and monthly means of air temperatures of summer season recorded at Aomori Meteorological Observatory for sixty four years from 1866 to 1949, and came to a conclusion that the bad harvests, which gave values of actual yield 1c<75, in percentage of the mormal yields, the latters being estimated theoretically for the corresponding year, should more naturally be considered as to form another distribution apart from the ordinary harvests which gave values 1c=±25 forming a normal distribution. The aspects discussed are as follows: (1) Of all the correlation Coefficients computed between temperatures and yields, that of the highest value(r=-0.755)was found between 1c and the mean temperature for three months from June to August, while the next (r=+0.743) was that between 1c ane the mean temperatures for five months from May to September. (2) The lines of regression of 1c on temperature were found to be devided into two parts giving critical points at 1c=75, where the corresponding three months' mean temperature was 18.95°C and the five month' mean was 17.25°C (Fig.5) (3) The rate of yield reduction per unit temperature depression proved larger for temperatures below the critical point than for those above it, and consequently bad harvests being due to temperatures below that point should naturally fall out of the range of the normal distribution formed by ordinary harvests concurrent with temperatures above it.

[学科分类] 农业科学（综合）