Deriving empirical models of evaporation from soil beneath crops in a Mediterranean climate using microlysimetry

Abstract

Microlysimeters were used to measure evaporation from bare soil and from soil under wheat and lupin canopies. The data were used to develop empirical relationships between evaporation, potential evaporation, soil water content, and leaf area index to allow estimation of evaporation losses in seasons when evaporation was not measured directly. Canopy cover was found to decrease evaporation losses from soil in both Stage 1 and 2 evaporation. This finding has significance to applications of the Ritchie model (1972) in Mediterranean climates since the model assumes Stage 2 evaporation to be independent of canopy cover. The empirical models derived during one season were successful in predicting evaporation from soil beneath crops during a second season. The model parameters were derived over the complete range in water content, leaf area index, and potential evaporation expected for crops at the site, suggesting that the models may be reliably applied to predict evaporation from soil at the site for other seasons. The technique may be useful for general application in estimating evaporation fromsoil beneath crops in field studies, although the model parameters may be site and/or soil specific. Further research into the generality of the relationships is warranted.