This two-years study was conducted to determine the effects of planting date and plant population on seed yield, oil content and certain plant characteristics of sunflower under dryland conditions in the Marmara Region of Turkey. Three planting dates (March, April, May) were established with two hybrids (Sunbred-265 and H-1) and open pollinated cultivar (VNIIMK-8931) at three plant populations (30,000, 47.500 and 95.000 plants/ha).

Seed yield and yield components decreased significantly with later planting dates. The highest seed yield, 1000-seed weight, seed weight per head. oil content and oil yield were obtained when sunflowers were sown in mid-March or mid-April. Compared with mid-May, the plantings in mid-March and mid-April increased seed yield by about 41% and 34%, respectively. Number of days from planting to flowering (50%) decreased as planting dates were delayed. Plant population significantly affected seed and oil yields and other plant characteristics measured. As plant population increased, head diameter. 1000-seed weight, and seed weight per head decreased, but plant height increased. The highest seed yield, oil content and oil yield were obtained at 95.000 plants per ha.