Optimization of grain sorghum water use efficiency under high frequency irrigation by system simulation and stochastic dynamic programming

Abstract

Water deficits reduce plant growth and subsequently, crop yields. Man has relied upon irrigation to overcome these crop water deficiencies. But since the present supplies of water are limited, more efficient irrigation application methods must be developed and utilized effectively. High frequency irrigation has been shown to be an efficient means more minimizing crop water deficits while maximizing irrigation application efficiency. This research evaluated the effects of high frequency irrigation on grain sorghum growth and yield and developed guidelines for the optimal utilization of a scarce resource--water--under high frequency irrigation. An experiment was conducted in fully instrumented field lysimeters which had undisturbed soil cores. Rainfall was eliminated as a variable by an automated movable shelter which protected the lysimeters from rain. The field measurements that were made in each lysimeter were soil water content, leaf temperature, leaf resistance, leaf water potential, leaf area index, and crop height. Measurements of windspeed, air temperature, dew-point temperature, and net radiation were made above the crop. The yield and water use efficiency of grain sorghum under high frequency irrigation was decreased primarily by water deficits occurring during the boot-to-bloom growth period. Water use efficiency was increased when water deficits were carefully managed by applying small, frequent applications of water and avoiding large deficits during the boot-to-bloom period. ...