Effect of nitrogen fertilizer and biofertilizer application on yield and quality of sunflower (Helianthus annuus L.)

In order to study the effects of different soil nutrition methods and plant growth promoting rhizobacteria (PGPR) on grain and oil yield and fatty acid composition in sunflower (Helianthus annuus L.), a field experiment was conducted on research farm at college of agriculture, Tarbiat Modares University, Tehran in 2006-2007 and 2007-2008 growing seasons. The experiment was studied in a split plot arrangement oftreatments in a randomized complete block design with three replications. Five fertilizer treatments including 100% organic (F1), 75% organic + 25% chemical (F2), 50% organic + 50% chemical (F3), 25% organic + 75% chemical (F4), 100% chemical (F5) were randomized to the main plots and two treatments of non-bacterial inoculation (I0) and bacterial inoculation (I1) were randomly assigned as the subplots. The results showed thatintegrated treatments produced significantly more grain, biological and oil yield and protein content than those grown in each of organic or chemical treatments. The maximum and minimum oil contents (51.1% and 46.3%) were obtained with the 100% organic and 50% organic + 50% chemical treatments, respectively, whereas thesame treatments were in the converse position for protein content (20.9% and 18.3%). Saturated fatty acids decreased significantly, while unsaturated fatty acids (linoleic acid and oleic acid) increased in response to raising the organic manure and using biofertilizer. The highest linoleic acid (52.6%) and oleic acid (39.8) were observed in 50% organic + 50% chemical and 100% organic treatments, respectively. Application of biofertilizerincreased the grain (7.8%), oil (11.3%) and biological yield, and also protein (4.9%) and oil (2.6%) content and improved the oil quality of sunflower seeds. Therefore, it seems that sunflower productivity and seed oil quality can be improved using different nitrogen nutrition methods.