Abstract
In the previous paper, it was revealed that the use of simple daily cumulative temperature could be applied more effectively for evaluating the combinations of corn varieties than the use of the effective daily cumulative temperature, because of its least annual and local fluctuations in Hokkaido. This experiment was carried out to clear the reason why the simple daily cumulative temperature fitted with growths of corn varieties by examining the effect of temperature beyond the effective regime on the growth of corn plant. The results obtained were as follows ; 1. Even where the daily mean temperature was under 10℃, germination or emergence of seeds and grain yield or kernel weights were remarkably increased. In addition to this, it was recognized that the corn were growing under the condition of daily mean temperature below 10℃, because they have several hours of high temperature above this in the daytime. 2. Since there are few days being higher than 25℃ of daily mean temperature in Hokkaido, it hardly needs to apply higher temperature than 25℃. Moreover, it was supposed that high temperature itself might give good effects on crop growth under the condition of sufficient rainfalls. 3. In conclusion, it was estimated that some part of the effective temperatures to crop growth were excluded in the case of applying the effective daily cumulative temperature. But in using the simple daily cumulative temperature, it was recognized that it accumulated all effective temperatures and consequently had little local and annual fluctuations.
