抄録
At the upland field in Nakasatsunai village, Hokkaido, heat balance components, soil temperature, and soil water suctions were measured during cultivating periods over ten years. The following results were gained :
1) From the results of the monthly average of heat balance components and soil water suctions, soil moisture for the growth of upland crops decreased or became deficient in late May and June, and there was a surplus from August.
2) The amounts of evapo-transpiration of the monthly average were 3.1 in late May, 3.6 in June, 3.0 in July, 2.7 in August,1.9 mmd-1 in September and early October.
3) In early June and early July, the ratio of soil heat flux during the daytime to net radiation with wet soil condition on a sunny day was more than that with dry soil. In early June, the ratio of latent heat flux during the daytime with wet soil on a sunny day was about 50% and somewhat less than that with dry soil. In early July, the ratio with wet soil on a sunny day was about 80% and more than that with dry soil.
4) In early July, though the range of soil temperature at lcm depth with dry soil on a sunny day was more than that with wet soil, the range at 5 cm depth with dry soil was less than that with wet soil.
5) Numerical analysis of the changes of soil temperatures with wet and dry soil conditions should be carried out to clarify which is better for the raising of the plow layer temperature in early cultivating periods.
