Abstract: A model about the affects of the irrigation amount and uniformity to the crop yield was developed in this study by assuming that the sprinkled water was linearly distributed. The simulation results demonstrated that crop yield increased with increasing irrigation uniformity for a given irrigation amount. The model was used to determine optimum irrigation amount for obtaining maximum net return. The results showed that the optimum irrigation amount depends upon irrigation uniformity and economic factors, decreasing with the uniformity but increasing with the ratio of product price to water cost. The model was also used to determine optimum irrigation uniformity for various irrigation amounts. The optimum uniformity increases with an increase of irrigation amount expressed by a ratio between gross and required irrigation quantity, but approximates 90% when the ratio exceeds 0. 85.