Integrated Fertilization Systems Enhance Quality and Yield of Sunflower (Helianthus annuus L.)

Effects of various fertilizers such as farmyard manure (FM), urea, and plant growth promoting rhizobacteria (PGPR, including the genera Azotobacter and Azospirillium) were checked on yield, fatty acids, protein, and oil contents of sunflower. A two-year field experiment was conducted in a semi-arid region in Iran in 2007 and 2008. The experiment was a split plot in a randomized complete block design with three replicates, with five fertilizer treatments as the main plots and two PGPR treatments as sub plots. Results demonstrated that the integrated fertilizers significantly increased the leaf area index, plant height, grain production, biomass, oil yield, and protein content in comparison with organic or chemical fertilizers. The maximum and minimum oil contents were obtained by applying 100% farmyard manure (F1) and 50% FM + 50% chemical (F3), respectively; however, opposite results were observed for protein content. When higher FM rates were used with PGPR, the saturated fatty acids (palmetic and stearic acids) declined significantly, while unsaturated ones (linoleic and oleic acids) were increased. The highest contents of linoleic acid (52.6%) and oleic acid (39.8%) were observed in F3 and F1 treatments, respectively. Bacterial inoculation also increased the leaf area index, plant height, biomass, grain and oil yields, oil and protein contents up to 12, 3.7, 7.8, 10, 6.5, 5.6 and 5%, respectively.