Production Function for Cotton With Dated Irrigation Quantities and Qualities

Abstract

A dynamic crop‐water production function model is estimated for cotton. Evapotranspiration (ET) depends on soil moisture and soil salinity which in turn depend on irrigation volumes and qualities. Crop yield is a function of ET. A maximum likelihood approach is developed for estimating the ET function when moisture and ET observations are not available on a daily basis. The estimated ET function varies by crop growth stage and generally shows decreasing ET as soil water potential decreases. Soil salinities following irrigation are explained quite well using a piston flow model of salt transport. Several yield‐ET relations are estimated. The model can be used for predicting crop yield, ending soil salinity and soil moisture levels, and drainage volumes and qualities, given irrigation timing, quantity and quality of applied water, and initial levels of soil salinity and soil moisture.