Effects of atmospheric evaporativity, soil type and redistribution time on evaporation from bare soil

Abstract

Several reports in the literature show that atmospheric evaporativity (Eo), water transmission characteristics of soil and distribution of water in the profile influence the pattern of evaporation losses from soil, but few relate to their interactive effects. Experiments were conducted with silt loam, sandy loam and loamy sand soils with zero and 2 days' redistribution time before commencement of evaporation under high (15.1 ± 0.50 mm day-1), medium (10.1 ± 0.50 mm day-1) and low (6.3 ± 0.52 mm day-1) Eo to ascertain if cumulative evaporation (CE) was always greater under higher Eo irrespective of experimental conditions, and if the evaporation rates during falling rate stage were insensitive to changes in Eo in all soils. Where evaporation commenced immediately after wetting, CE up till 30 days was always higher under higher than lower Eo values in the silt loam and sandy loam soils. In the loamy sand, however, CE under medium Eo conditions exceeded that under high Eo conditions after 2 days. When evaporation commenced after 2 days of redistribution CE under medium and low Eo values exceeded that under high Eo values after 8 and 12 days in the sandy loam, and 2 and 6 days in loamy sand, respectively. Where evaporation was commenced after the 2-day redistribution, CE at 30 days in the silt loam and sandy loam was 12% less than where evaporation commenced immediately after infiltration under all the Eo values. In loamy sand these differences were 17% and 40% under low and high Eo values, respectively. CE as well as evaporation rate (ER) were sensitive to Eo in the initial period of falling rate stage in the silt loam and the sandy loam but not in the loamy sand.