Modeling crop yield as affected by uniformity of sprinkler irrigation system

The effect of sprinkler irrigation uniformity on crop yield is an important consideration for the design of sprinkler irrigation system. A model that relates yield response to evapotranspiration deficits at special growth stages to evaluate the impacts of uniformity on crop yield was developed from a crop water production function. The simulation results of the model showed that crop yield increased with increasing uniformity. Optimum irrigation amount and uniformity for the maximum net return were determined with the model. The optimum irrigation amount depends on irrigation uniformity and on economic factors, decreasing with the uniformity but increasing with the ratio of product price to water cost. The optimum uniformity increased with an increase of irrigation amount expressed by a ratio between gross and required irrigation amount, but approximated 90% when the ratio exceeded 0.85. Field experiments conducted to study the relationship between spatial distribution of soil moisture and sprinkler application uniformity demonstrated that the water in the soil was more uniformly distributed than that measured for the application at the soil surface. (C) 1998 Elsevier Science B.V. All rights reserved.