A model for estimating soil moisture changes as an aid to irrigation scheduling and crop water-use studies .2. Field test of the model

A model was developed to estimate daily evapotranspiration and root zone soil moisture changes appropriate for scheduling irrigation, incorporating a modified version of the Penman-Monteith equation. The model was field tested during 1992-94, for potatoes and sugarbeet, by comparing modelled root zone soil moisture changes with field measurements taken using neutron probes. The study confirmed the accuracy of the model when predicting crop water use and soil moisture change. Linear regression of measured versus modelled data exhibited a slope of 0.99 and an intercept close to and not significantly different from zero. The relationship accounted for 80% of the variation.