In this study three methods of Supplementary Irrigation (SI) and a control treatment without irrigation were evaluated in two different stages of growth on three wheat cultivars in 1998. The experimental design was split plot with three replications. The results show that SI had a significant effect on grain yield, kernel weight, spike number per plant and harvest index, but there was not significant difference on straw yield and grain number per spike. Among the cultivars, it was observed that there were significant disparity for kernel weight and number of spike per plant. The SI treatments had a significant difference of 5 per cent compare to rain-fed treatment (no irrigated). The maximum grain yield stood at 1785 kg/ha which is equal to two-time irrigation in autumn and spring with classic system, and the minimum grain yield stood at 921kg/ha which is equivalent of the rain-fed treatment. Sabalan cultivar had the maximum grain yield (1536 kg/ha) but there were not significant differences among other cultivars. The Sabalan cultivar had maximum grain yield (1845 kg/ha) with combined treatment of two-time SI and wheel-move system. Such cultivar was second best treatment (1807 kg/ha grain yield) with two-time classic system and SI. The treatments without SI had the lowest grain yield in comparison to other treatments.
