Comparison of Sole and Combined Nutrient Application on Yield and Biochemical Composition of Sunflower under Water Stress
Yaser Esmaeilian, Ali Reza Sirousmehr, Mohammad Reza Asghripour, Ebrahim Amiri

Abstract
This experiment was conducted to find the influence of organic manure sources and chemical fertilizers alone or in combination on the quality and yield of sunflower and also on the macro nutrients content of seeds under water stress. Three levels of water stress (S1: full irrigation, S2: withholding irrigation at flowering stage, and S3: withholding irrigation at seed filling stage) were randomized to the main plot units and 8 fertilizer treatments (F1: control, F2: cattle manure, F3: sheep manure, F4: poultry manure, F5: chemical fertilizer, F6: 50% cattle manure+50% chemical fertilizer, F7: 50% sheep manure+50% chemical fertilizer, and F8: 50% poultry manure+50% chemical fertilizer) were randomized to the subplot units. Obtained results revealed that seed yield decreased significantly due to water stress when imposed at either of the growth stages. Assessment of the qualitative parameters of sunflower seeds showed that water stress caused a marked decrease in oil content and unsaturated fatty acids of oil, however this negative effect was greater in water stress at seed filling stage with respect to water stress at flowering stage. While, protein content increased due to water stress at flowering stage. Results also indicated that drought stress at seed filling stage significantly decreased nutrient content of the seeds, whereas drought stress at flowering stage caused to increase of nutrient uptake. Sunflower plants significantly responded to fertilizer treatments. The seed yield was highest in case of application of manure alone or in combination with chemical fertilizer than in control. Protein and oil percentage were significantly higher in F3 (sheep manure) and F6 (50% cattle manure+50% chemical fertilizer), respectively. Compared to control, all fertilization methods generally increased nutrient concentration of sunflower. The highest N content was observed in F4 and F6 treatment. Combination of poultry manure and chemical fertilizer (F8) led to the highest P content and sheep manure application (F3) resulted to the highest K content than control.

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