To evaluate the effect of water stress at different crop growth stages on yield, yield components and water use efficiency, a field experiment was carried out in 2015/2016, 2016/2017 and 2017/2018 for bread wheat (Gambo variety) at Werer Agricultural Research Center. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications having 15 experimental treatments. Combination of water stress with crop growth stages was applied in the major investigation of the

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... riment. The highest grain yield was obtained from the control treatment irrigation at all stages (no stress). Stressing irrigation water at initial stages and maturity stages gave second highest yield (29.23 and 28.57 qt/ha) and lower water use efficiency (0.43 and 0.35 kg/m 3 ) respectively. While irrigating only at the initial stage gave highest water use efficiency (0.79 kg/m 3 ) and lowest grain yield. Application of irrigation water at all stages except initial and maturity gives optimum grain yield (26.73 qt/ha) and water use efficiency (0.62 kg/m 3 ) for the study area. Therefore, wheat should not be stressed at development and mid stage to obtain optimum water use efficiency (WUE) without a significant grain yield reduction.