Evaporation from Bare Low Humic Latosol in Hawaii

Abstract

Despite the high potential evaporation, actual evaporation from Wahiawa Low Humic Latosol measured by hydraulic lysimeters is very low under field conditions. The evaporation from Latosol at field moisture content is only one-third the rate from a pan. The heavy clay soil is so strongly aggregated that the water release for low values of soil moisture suction is determined by the aggregate rather than by the mechanical composition of the soil. The unsaturated hydraulic conductivities determined for the Latosol decrease rapidly as the soil dries, a feature in accord with the self-mulching action of the soil. Moreover, the mineralogic and aggregate composition of the soil make the material an excellent thermal insulator and the consequent restriction of heat flow also reduces the rate of evaporation since much of the water movement within the unsaturated Latosol is in the vapor phase along temperature gradients. The transfer of latent heat within the soil contributes appreciably to the heat storage in the soil.