Study on the Effect of Water Stress at Different Growth Stages on the Yield and Grain Quality of Wheat

Drought is an important environmental factor which reduces wheat production in arid and semi arid regions. The response of wheat to three levels of water stress at three growth stages, namely, heading, flowering and grain filling was studied under field conditions at Kahriz Station of Uromieh for two years. The experimental design was factorial (complete block) in three replications. Experimental treatments were time and amount of irrigation and included : t₁=irrigation at heading , flowering and grain filling stages. t ₂= irrigation at flowering and grain filling stages. t ₃= irrigation only at grain filling stage. Treatments of water amount were: W₁, W2, W3, respectively, 40, 70, and 100% of evaporation from class A pan. The MSTATC software was used for statistical analyses of grain yield  water use efficiency , 1000grain weight, and protein percentage. The main effect of irrigation timing and amount and their interaction showed significant differences for grain yield, water use efficiency, 1000 grain weight and protein percentage. The comparison of means was done by Duncan^, s method. The highest significant grain yield, 5.59 t/ha, was obtained with t₁ W₂ (irrigation at   3 growth stages with water application 70% of class A pan). At all stages of growth, moderate and severe water stress decreased plant height,1000grain weight, grain yield and water use efficiency. Wheat was most sensitive to water stress during the flowering stage. Results suggest that in Kahriz area and similar other locations, when water is scarce or limited, wheat crop should be irrigated at heading and flowering stages with an amount equal to 70% of evaporation from class A pan