Effects of Intercropping Proportion on the Quantity and Quality of Essential Oil in Isabgol and Ajwain

In this study، the effect of planting date and cropping systems were examined on the quantity and quality of ingredient materials and intercropping efficiency at isabgol- ajwain intercropping. The experiment was performed on split plot with two planting date; January 10 and February 9 comprising the main treatments، and six combinations of isabgol and ajwain (sole isabgol، sole ajwain، 25% isabgol + 100% ajwain، 50% isabgol + 100% ajwain، 75% isabgol + 100% isabgol and 100% isabgol + 100% isabgol) as sub-treatments that were applied with three replications. The experiment was conducted at the Zabol University research farm in Zabol، south Iran during 2013. Chemical analysis was performed using combination of capillary GC، GC-MS after fractionation on column chromatography and detected 33 compounds. p-Cymene and Gamma terpinene was the major oils compounds. The percentage، yield and chemical composition of oil differed between planting date. Delay in planting increased thymol and percentage of oil، while the greatest yield of oil and p-CymeneandGamma terpinene was achieved in January 10. The maximum percentage and yield of essential oil was obtained at sole ajwain، and increasing of plant population decreasedthymol and p-Cymenewhile increased Gamma terpinene. Sole isabgol had the greatest yield of mucilage and decreasing of population has significant impact on this parameter. Treatment of 50% isabgol + 100% ajwain had the greatest Land Equivalent Ration (LER=2. 53)، indicated yield advantage in intercropping over monocropping.