Effect of fertilizer treatments and irrigation regimes on seed yield and seed quality characteristics of sunflower

The current study was conducted to investigate the effects of different soil fertility treatments on qualitative and quantitative yield of sunflower (Helianthus annus L.) under different irrigation regimes. The experiment was conducted in Tarbiat Modares University research field at 2012 and 2013 growing season. Treatments were arranged as split plots based on a randomized complete block design with three replicates. Irrigation regimes were randomly assigned to the main plots and the subplots were eight different fertilizer types. The results indicated that the maximum seed yield was obtained in normal irrigation treatment (irrigation after consuming 30% of available soil moisture). Under water deficit stress conditions (irrigation after consuming 50 and 70% of available soil moisture), organic treatments amended with more zeolite (zeocompost, zeoponix and zeocompost zeoponix) improved seed yield. Under severe water deficit stress condition (I3), zeolite-amended organic treatments (zeocompost, zeoponix and zeocompost zeoponix) increased seed oil percentage by 8, 9 and 13 percent in the first year and by 13, 10 and 12 percent in the second year of the experiment in comparison with chemical treatment (F1). In addition, organic treatments improved oil quality through increasing linoleic and oleic acid percentage. Overall, the results suggest that combined application of processed organic fertilizers such as vermicompost, zeocompost and zeoponix not only increases sunflower seed yield and oil quality but also reduces chemical fertilizers need in sunflower production.