Water production function of maize for Northeast Brazil

Abstract

The results of the randomized block experiment with four growth stages and four nitrogen levels to determine the water production function of maize (Zea mays L.) for Northeast Brazilian conditions are reported. The yield response factors as per Doorenbos and Kassam's equation are found to vary drastically not only for different growth stages but also with different nitrogen levels and with different water levels. Thus, this equation is not a true representation of yield response to water. A modified linear equation with an intercept (K₂) has been suggested. The coefficients of this modified equation (intercept K₁ and the slope K₂) are the modified yield response factors. These factors for maize have been developed here for all the four stages and for all the four nitrogen levels. The average highest water use efficiency of approximately 57.5 kg/ha-cm of water can be obtained but it shows no increase with increase in applied nitrogen up to 120 kg/ha. Finally crop coefficients (K _c) have been calculated. The overall values of K_c are much below the FAO estimates for all nitrogen levels. All the above information developed here will help in better irrigation scheduling and better planning of supplemental irrigation projects in the Northeast Brazil.