The main aims of this study were to obtain grain and oil yields of sunflower ( Helianthus annuus L.) under adequate and limited soil water supply during the total growing season and under limited soil water supply at the early vegetative, late vegetative, vegetative, flowering and yield formation periods, to find out the sensitive periods to soil water deficits, and to determine yield response factors (k y ). The experiments were conducted in the fields of the Research Farm of the Agricultural Faculty, Ankara University, in 1994 and 1995. It was found that the highest grain and oil yields were obtained at the plots where adequate irrigation water was applied during the total growing season. The yield response factors (k y ) were found in the range of 0.50-0.75 for flowering period that was the most sensitive period to water deficits, 0.81 for the total growing season and, in ranges 0.35-0.71, 0.12-0.67, 0.13-0.35 and 0.16-0.23 for the vegetative, late vegetative, yield formation, and early vegetative periods, respectively.

The main aims of this study were to obtain grain and oil yields of sunflower ( Helianthus annuus L.) under adequate and limited soil water supply during the total growing season and under limited soil water supply at the early vegetative, late vegetative, vegetative, flowering and yield formation periods, to find out the sensitive periods to soil water deficits, and to determine yield response factors (k y ). The experiments were conducted in the fields of the Research Farm of the Agricultural Faculty, Ankara University, in 1994 and 1995. It was found that the highest grain and oil yields were obtained at the plots where adequate irrigation water was applied during the total growing season. The yield response factors (k y ) were found in the range of 0.50-0.75 for flowering period that was the most sensitive period to water deficits, 0.81 for the total growing season and, in ranges 0.35-0.71, 0.12-0.67, 0.13-0.35 and 0.16-0.23 for the vegetative, late vegetative, yield formation, and early vegetative periods, respectively.