Abstract
By comparing yield per Tan of aquatic rice, wheat, common barley and naked barley in the towns and villages of Okayama prefecture with climatic factory. which have close relations with the yields, we deterniincd the climatic divisions. for crop culture. The date of the yield per Tan red for this research are of 367 towns and villages concerning the yields from 1920 to 1930, and the meteorological data were obtained from 38 meteorological observatories from 1916 to 1940.
First of all, we researched what kind of climatic factors had most to do. with the yields of aquatic rice, wheat, common barley and naked barley. As its result, we found that the yield of aquat ie rice had a close relation with vegetable period; the number of days over 5°C in a year (D1), and amount of precipitation from Mey to October (P1), and on the other hand, wheat, common burley, nd naked barley had a close, relation with the n inber of days under 5°C in a year (D2) and amount of precipitation from April to June (P2) respectively.
As the formula for the relation between the climatic factors and town and village yield per Tan, we obtained the results as shown in Tab. 2.
Two times probable error of D calculated out by putting yield per Tan in Y are shown in the rightest column of Tab. 2 and these two tunes probable error w named as variability of climatic. The climatic divi;dons which were dividCd by these variability of climat are shown in Fig. 2. 3 and 4
