Deficit irrigation trial has conducted to determine the response of wheat to the amount of irrigation water and frequency at different growth stages at Werer Research Center for three years (2014-2016). The experiment laid in Randomized Complete Block Design (RCBD) with three replications. Eight irrigation water amount were applied where wheat variety suitable for lowland irrigated area (Ga’ambo) was planted on experimental plots of 5 x 10m2 size. Establishment irrigation were given for all plots after planting and irrigation water application events WERE monitored from soil moisture readings. Soil moisture content measurements done every two to three days at 30-cm depth interval up to the maximum root depth during the growing stage, and Water WAS applied when soil moisture content reaches at FAO recommended (55%) allowable moisture depletion level. Similarly, irrigation depths (amount of water applied) were calculated from cumulative ETC values in a given period and plots were irrigated with depths that was replenish 100 %, 75%, and 50 % of the cumulative ETC as per the treatment to be applied. Measured amount of irrigation water applied to every plot measured by using 3’’Parshall flume. At harvest, grain yield and all other agronomic data collected were analyzed using appropriate statistical software SAS version 9.0. Results indicated those grain yields significantly affected by irrigation levels. The highest mean grain yield of 1416 kg/ha obtained from optimum irrigation at all growth stages except development stage application, while the lowest mean yield of 867 kg/ha was obtained from treatment with no irrigation was applied throughout growth stages but only pre irrigation. Therefore, based on the present findings, irrigation scheduling of optimum irrigation at all stages except at development growth stage could be the best option and recommended for irrigated wheat production.

Keywords: Deficit Irrigation, Growth stages, Water use efficiency, Irrigated Wheat