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This experiment was conducted in 2000 to study the effects of four irrigation
intervals in the seed yield as well as quantitative characteristics of three sunflower cultivars. The experiment was performed on the experiment farm of Oil Seed Department, Seed and Plant Improvement Research Institute. Cultivars used were: Record, Golshid, and Hysun33. The irrigation intervals included; every seven, eleven, fifteen and nineteen days. The results indicated that with increase in irrigation interval the number of seed per head, seed yield, harvest index, oil percentage, head diameter, thousand seed weight decreased while percentage of infertile seeds increased. Hysun33 was least affected by irrigation interval so that its seed yield in the second irrigation
interval treatment was equal to that of Golshid in the first irrigation interval and it was more than the yield in Record in the first irrigation regime. Considering the good performance of Hysun33 in the second irrigation interval (every eleven days) cropping of this cultivar of good performance will result in saving water and thus seems to be recommendable.