Spatial Variability of Soil Water and Evapotranspiration

Abstract

Spatial variability in evapotranspiration from a crop covered field exposed to homogeneous climatic conditions is partly caused by field variability in soil physical properties and partly by field variability in pertinent crop properties. The present paper presents an analysis of the spatial variability in soil water content and evapotranspiration for two 0.5 ha grass fields of different soil texture, viz. a coarse sand and a sandy loam. Soil physical properties and soil water profiles were determined 1 m apart at 16 points systematically located in each field. The analysis of soil water profiles in relation to soil physical properties indicates an appreciable variability within a range of 1 m. For this reason a relatively simple model was used to simulate the variability pattern of the evapotranspiration, taking into account the variability in plant available water content. The results of the simulations are compared with the evapotranspiration patterns determined on the basis of a short term water balance.