Effects of Polyethylene and Organic Mulches and Irrigation Intervals on Oil Content and Fatty Acids Composition of Sunflower

In order to investigate the effects of polyethylene and organic mulches in different irrigation intervals on oil content and fatty acids composition in sunflower, an experiment was conducted at the research farm of college of Aboureyhan, University of Tehran, in 2009. The study was conducted in split-plot design based on randomized complete blocks with three replications. The main factor consisted of three irrigation intervals including 7, 12, and 17 days, and the sub-factors were the control (without mulch) and different types of mulch (polyethylene, cow manure including 8.5 ton/ha,17 ton/ha, 25 ton/ha, wheat stubble mulch at three levels of 2.5 ton/ha, 5.5 ton/ha, and 7.5 ton/ha). The results indicated that increasing irrigation intervals and the effect of water deficit stress cause considerable reduction in the amount of oil seed. Also, the highest oil yield was obtained from polyethylene and stubble mulch (7.5 ton/ha). Investigation on fatty acids compositions in sunflower seed indicated that highest fatty acids i.e. palmitic (6.26%) and stearic (4.1%) were obtained under intensive water deficit stress and oleic (40.44%) and linoleic (51.76%) were obtained under mild water deficit stress, respectively. Besides, the highest fatty i.e. acid, palmitic (6.44%) and linoleic (51.17%) were obtained in stubble mulch (7.5 ton/ha) and the highest fatty acid oleic (40.31%) was obtained in cow manure mulch (25 ton/ha). The overall test results showed that mulches can increases the quality and quantity of seed yield by reducing irrigation water use. Considering the results of the study and non-toxic effects of stubble mulches in agriculture, we suggest their usage.