The Study on the Effect of Different Levels of Vermicompost and Plant Density on Oil Content and Components of Evening Primrose (Oenothera biennis L

To investigate the effects of different levels of vermicompost and plant density on oil content of evening primrose and its components, an experiment was conducted as a factorial layout based on Randomised Complete Block Design with 12 treatments and 3 replications in experimental field of Faculty of Agriculture, Ferdowsi University of Mashhad during 2008-2009. The treatments were included 4 levels of vermicompost (0, 2, 3 and 5 kg.m-2) and 3 levels of plant density (9, 12 and 20 plant/m-2). Oil extraction was carried out by Soxhelet apparatus and its percentage was determined as weight. Analysis of fatty acids was done by Gas Chromatography device. Density and refractive index of the oil also was evaluated. According to the results, simple effect of vermicompost and plant density was significant only on oil percentage and its refractive index, while the interaction between them was significant on all of the traits. Fatty acids composition of oil in all treatment was the same. The major saturated fatty acid was palmitic acid and linoleic acid was the major unsaturated fatty acid. The amount of γ-linolenic acid was in optimum range (7-8 %). Overall, treatment of 2 kg.m2 vermicompost and plant density of 20 and 9 plant/m-2 was determined as the best treatments by considering the improving of oil production, oil quality and ratio of unsaturated fatty acids to saturated fatty acids, respectively.