ABSTRACT:This paper presents a methodology for the estimation of response functions of crops to irrigation and soil moisture. A system analysis framework is applied to describe the relationships involved. Two subsystems are distinguished, with the first one involving the relationship between irrigation decision variables and soil state variables, and the second involving the relationship between soil state variables and crop yield.A method for tracing and predicting soil moisture profile variations over time and depth is presented, and empirical estimates of the response function of grain sorghum to soil moisture are derived. In the specification of the response function the concept of “critical days” is applied with a “critical day” being defined as one where the soil moisture is depleted below a certain critical level. The paper provides empirical evidence for the usefulness of the
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