Soil evaporation measurements in an agroforestry system in Kenya

Evaporation from soil ( E s) was studied in an agroforestry system using soil microlysimeters, where the tree and crop components were grown together, in monocultures where the two components were grown separately, and in bare soil. All measurements were carried out at an equatorial field site in Kenya. E s varied according to the different shade regimes and as a function of proximity to trees and/or crops. Over periods of 3–12 days, the maximum reduction in E s compared to completely bare soil was 40%. This was observed under a maize canopy when the crop leaf area index (LAI) was 2.0. When the trees had similar values of LAI (1.9), the reduction in E s was lower at 23%. However, in contrast over an entire rainy season, the presence of trees over bare soil reduced total seasonal E s by 24%, compared to an 8% reduction in E s by the maize crop. The maize crop was less effective in reducing E s largely because of its shorter duration.