Evaporation from Soil

This chapter focuses on evaporation from bare or nearly bare soils and includes procedures for adjusting estimated evaporation for partial plant cover. Evaporation estimates from bare soil are important in early and late crop-growing periods and in nongrowing periods. They are also important for estimating effects of wet soil within vegetation on total evapotranspiration (ET). Evaporation from bare soil is often divided into two or three stages that characterize the form or nature of control on the evaporation process and rate. Several models are used to estimate evaporation from soils. When used in conjunction with total estimates of ET and on an operational basis, simplified models are often applied that do not require extensive soil hydraulic data. The examples show how the simple square root of time and FAO56 models compare with absolute measurements of evaporation taken by a precision-weighing lysimeter system.