EVAPORATION THROUGH A SOIL MULCH IN RELATION TO MULCH CHARACTERISTICS AND EVAPORATIVITY

A simple equation describing the effects of atmospheric parameters and soil mulch characteristics upon vapour flux density through a dry soil mulch was successfully developed. Determination of vapour flux density was made from columns of diameter 0.1 m and length 0.95 m. These were filled with silt loam and sandy loam soils with surfactant-treated soil mulch on the surface which varied in thickness and porosity. The experiments were conducted under different atmospheric evaporativities (E0), which comprised a number of combinations of wind speed and ambient temperature. The observed vapour flux density and that computed with Hanks' equation matched well. The results indicated that evaporation under a given E0 was affected more by temperature than wind speed. However, vapour flux density showed a strong interaction with wind speed, temperature and the soil mulch characteristics such as porosity and thickness.