Determination of Optimal Water-Yield Production Function and Evaluation of Cotton Production Indices of Varamin and Khordad Cultivars in Sarayan Area of South Khorasan

This research was carried out to determine the optimal water-yield function for cotton plant and to evaluate the cotton production indices in a factorial based on a completely randomized block design with three replications for one year in Sarayan area. The research factors included four levels of I1, I2, I3 and I4 irrigation depths of 50, 75, 100 and 125% of the plant water requirement as the main factor and two cotton cultivars (V1Varamin and V2Khordad) as a sub factor. The best production function was selected from four production functions (linear, CubbDuglass, Quadratic, and Transcendental) for two cotton cultivars. For both cotton varieties of Varamin and Khordad, the second-order function was selected as the optimal production function. The average final production index for irrigation water in Varamin was 37/80 kg / ha for irrigation water depth per centimeter and 36.71 for cotton in Khordad. The final production value of irrigation water (VMPi) for cotton in the Varamin variety was equal to 2268185 Rials and for cotton in Khordad 2202727 Rials. Comparison of these figures indicates that Varamin cotton is more resistant to water shortage and more economical in terms of cultivating it in Sarayan area.