Yield and Oil Percentage of Safflower Cultivars (Carthamus tinctorius L.) in Spring and Summer Planting Seasons Affected by Drought Stress

To investigate the effects of drought stress on yield and oil percentage of safflower, an experiment was carried in split split plot based on randomized complete block design with four replications during spring and summer planting seasons at Kaboutarabad Agricultural Research Station of Isfahan in 2015. The main factor consisted of two planting seasons (spring and summer), the sub-factor comprised of three irrigation treatments (normal irrigating from sowing to plant maturity as control, irrigation up to the beginning of flowering and irrigation up to seed filling period) and the sub-sub factor were ten safflower cultivars (Sofeh, Goldasht, Sina, Faraman, Mec117, Mec295, Mec18, Mec11, Mec7 and Mec27). The results showed that irrigation treatments had significant effects on leaf area index, relative water content, plant dry weight and grain yield. Drought stress reduced these traits. Drought stress had not significant effect on oil percentage while oil yield because of reduction of grain yield. The highest yield of oil belonged to Sofeh cultivar. Oil yield in irrigation treatments during seed filling and flowering period decreased by 26% and 46%, respectively as compared to control. Results showed that all cultivars in summer planting had lower grain and oil yield due to increasing of temperature as compare to spring planting. Although the oil percentage in summer planting was about 1% higher than spring planting, but due to lower grain yield, oil yield decreased by 60% during summer planting. Sofa and Mec11 cultivars produced the highest and lowest oil yields with 803 and 530 kg.ha -1 , respectively. Also, Sofa cultivar had the highest grain yield in both of planting seasons.