Effect of Organic and Chemical Fertilizers on Yield, Yield Components and Seed Quality of Sunflower under Drought Stress Conditions

This experiment was conducted to study the response of sunflower to organic، chemical and integrated fertilizers as well as temporary drought stress in the reproductive growth stage as split plot on the basis of a randomized complete blocks design with 24 treatments and three replications. Main factors composed of S1: control (full irrigation)، S2: temporary interruption of irrigation in the flowering stage and S3: temporary interruption of irrigation in the seed filling stage and sub plots composed of F1: control، F2:30 ton ha-1 cattle manure، F3:20 ton ha-1 sheep manure، F4:10 ton ha-1 poultry manure، F5: recommended chemical fertilizer، F6: half of cattle manure + half of chemical fertilizer، F7: half of sheep manure + half of chemical fertilizer، and F8: half of poultry manure + half of chemical fertilizer. The results illustrated that drought stress caused reducing of seed yield and 100-seed weight and increasing of seed hollowness، but had not any significant influence on capitol diameter، stem diameter and plant height. Among the fertilizer treatments، F2، F4 and F6 had the highest effects on yield and on other measured traits and the lowest amount was related to the control (F1). Drought stress in the flowering stage caused an increase in seed protein content than other treatments. Seed oil content and Oleic and Linoleic unsaturated fatty acids at the full irrigation treatment had the highest and at the drought stress in seed filling stage treatment had the lowest values. Protein yield and oil yield، because of great effect of the drought stress in the reproductive growth stage on seed yield، showed significant decreases. Drought stress in the flowering stage increased the concentration of the nitrogen، phosphorous and potassium، while in the seed filling stage it caused decrease of nutrient concentration in the seeds as compared to the full irrigation treatment. Among the different fertilizer sources، the protein percentage and protein yield showed the highest amounts in F3 and F4 treatments، respectively. But، the highest values of the oil percentage and oil yield were obtained from F6 treatment. Linoleic acid percentage in F4 and oleic acid percentage in F3 treatments were higher compared to the other treatments. Results also clarified that application of the manures or its combination with chemical fertilizers had more effect on the increase of nutrient concentration of seed than that with application of the chemical fertilizers.