Studies on the height limit of paddy field in Japan

Abstract

(1) T=21.5-0.641(φ-36.5)-0.017(φ-36.5)2-4.726hT=the average air temperature from May to Octoberφ=latitude h=height (unit: kilometer)We gained the above formula as the relation among the average air temperature from May to October, the latitude and the height, by using the observed value of 149 observatories in Japan. The error between the estimated value from this formula and the observed value is very small.(2) Every temperature of height limitting places at 5 divisions of Japan which gained from above formula is as follows.The temperature of height limitting place at Hokkaido is about equal to the temperature of level land from 44°N to 45°N. similarly that of North-East division to that of from 41°N to 43°N, the Central division to from 42°N to 44°N, the South-West division to from 38°N to 41°N, and the South to from 33°N to 36°N. From this fact we can consider the correspondency of cultivating form.(3) The minimum of the average air temperature from May to October is 14°C for rice plant growing. But the actual height limit is not always equal to the height which T=14 of above formula gives. This is due to various causes-natural features, duration of sunshine, & C. In this paper, the author studied only the relation between height limit and absolute height, and land distribution.