A field experiment was carried out during the 1998-growing season of corn (Zea mays L.) variety Hageen 310. The objectives of the present study were to develop the crop-water production functions (CWPF) of corn and determine how the levels of K- fertilization affect the crop-water production functions. The irrigation was applied when the soil moisture depletion in the root zone reached to 20, 40, 60 and 80% of available soil water. Potassium fertilization was applied at four levels i.e., 0, 15, 30 and 60 kg K₂O/fed in the form of potassium sulphate (48% K₂O). The texture of the experimental soil was a clayey. The treatments were arranged in a split plot design with four replicates. The CWPF's used in the present study were: De Wit (1958), Jensen (1968), Penman (1970), Hanks (1974), Stewart et al. (1977), Helweg (1991), Gaussian, Exponential, Linear, and Logarithmic models. The comparison for the accuracy of the predicted yield responses from each model was examined. Accordingly, the Gaussian and polynomial models have the highest values of R². It is account as 0.9680** and 0.9337**, respectively. The Jensen and Logarithmic models have the same values of R², 0.9008** and 0.9003**, respectively. Likewise the Penman and modified Stewart models have the same values, 0.8828** . The De Wit, Linear, Exponential and Hanks have approximately the same values, 0.8006**, while the Stewart model has the lowest R² value, 0.4255^ns. The present results support the hypothesis that K fertilization can improve the water utilization efficiency by plants. Therefore, more study is needed to explain the role of fertilization in the shape of crop-water production function as related to rate and frequency of fertilizer application.