Water stress may be imposed in safflower to increase water use efficiency and to prevent excessive vegetative growth without significant decrease in yield. This study was conducted to determine the appropriate irrigation regime on the basis of cumulative water evaporation from standard evaporation pan (class A) and to find out the effects of these irrigation regimes on vegetative and reproductive growth stages of safflower. The experiment was conducted in 2005 at the Lavark Agricultural Research Station, Isfahan University of Technology located near Nejaf-Abad using a randomized complete block design with a split plot layout and four replications. The study included four irrigation treatments (irrigation after 70, 85, 100 and 115 mm cumulative pan evaporation) as the main plot and two varieties (Kouseh and IL111) as subplot. The effects of irrigation treatments on head visible, start and end of flowering and physiological maturity stages were non-significant, but delay in irrigation slightly reduced these stages. Kouseh matured 6 days later than IL111. Delay in irrigation from 70 to 115 mm pan evaporation reduced LAI non-significantly (1.12 unit) at 60 day after planting. The effect of variety on LAI was non-significant. The effects of irrigation treatments on number of first and second degree branches were non-significant. IL111 significantly produced more first degree branches than Kouseh, but Kouseh produced six second degree branches per plant more than IL111. The effects of irrigation treatments on yield component were non-significant, but delay in irrigation from 70 to 115 mm, reduced number of seeds per head (27.7 %) and number of head per plant (12.5 %). The maximum (2434 kg/ha) and minimum (1692 kg/ha) seed yields were obtained with 70 and 115 mm irrigation treatments, respectively. Variety had significant effect on seed yield. Kouseh produced 9% higher seed yield per unit area than IL111. Irrigation regimes did not significantly effect seed oil percentage, but had significant effect on oil yield. Oil yield reduced with delay in irrigation and this reduction was mainly due to reduction in seed yield. Kouseh had higher oil percentage and oil and seed yields than IL111 and seems to be superior to IL111 for planting in conditions similar to the present experiment
