The Three Stages of Drying of a Field Soil
1974
Idso, S. B. | Reginato, R. J. | Jackson, R. D. | Kimball, B. A. | Nakayama, F. S.
Six major drying experiments were conducted on a smooth, bare field of Avondale clay loam at Phoenix, Arizona, during all seasons of the year. Intensive measurements of evaporation, soil-water contents, soil temperatures, soil heat flux, albedo, and net radiation allowed us to delineate the three classical stages of soil drying. The first stage was characterized by potential evaporation. The second stage was characterized by drying of the soil surface, resulting in a significantly reduced evaporation rate. This stage continued until the volumetric water content at the soil surface reached a value of about 0.06, the predicted starting point for stage three for this soil—based on the assumption that physical adsorption takes place in the first two molecular layers of water surrounding the soil particles. Simple albedo measurements often predicted the transition points between the different stages.
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