Abstract
In infiltratioin process of water to dry soils, rise of the temperature just before the wetting front arrival is observed. This phenomenon is caused by wetting heat released by adsorption of water vapor onto the soil and or wetting of the soil. The temperature change affects not only soil water potential, infiltration itself due to change in viscosity of the water but also bio-chemical phenomena by changing temperature environment. However, few quantitative experiments and analytic studies have been made on this phenomena of natural soils, many problems remain to be solved on this matter. In this research, to evaluate the soil temperature change quantitatively, infiltration experiment was conducted on three types of natural soils under thermally insulated condition and the temperature change was monitored. In addition, wetting heat of the soils was measured by calorimetric method. The experimental results showed that the temperature increased at just before the wetting front by 2.3°C, 21.6°C and 5.8°C for the Masa soil, Ando soil and the red yellow soil, respectively. We observed strong relationship between the increases in the temperature and the wetting heats of each soil. The wetting heats of each soil showed strong relationship with the cation exchange capacity.
