Biological effects of phosphorus fertilizer application and plant density on the quantity and quality of medicinal plant essential oils in Ajowan (Trachyspermum copticum L.)

In order to evaluate the performance of biological phosphorus fertilizer and plant density on the quantity and quality of essential oils in Ajowan (Trachyspermum copticum L.)، this research was performed as a two factors factorial experiment in a randomized complete block design with three replications at the research field of the Research Institute of Forests and Rangelands in spring 2010. The treatments consisted of four levels of the phosphorus bio-fertilizer (Control (non-inoculated) seed soaked with liquid fertilizer، soluble fertilizer to the plants and seed soaked with liquid fertilizer & soluble fertilizer to the plants) and three levels of density (250000، 125000، 83000 plants per hectare). The studied characteristics included essential oil percentage، oil yield، percentage of thymol، terpinolene and p-cymene were in volatil oils. Results showed that the effect of bio-fertilizer phosphorus on the studied characteristics were significant at 1%، so that the highest amounts of oil percentage (4. 34%) and oil yield (143. 12 kg per hectare) were obtained in double inoculation treatment (seed soaked with liquid fertilizer & soluble fertilizer to the plants). In addition، the highest percentages of thymol (33. 9%)، terpinolene (41. 5%)، and p-cymene (23. 3%) were obtained in the treatments of seed soaked with liquid fertilizer، double inoculation treatment، and soluble fertilizer، respectively. The effect of plant density on the studied characteristics was significant at 1% level of significance، so that the highest amounts of oil percentage (4. 1%)، oil yield (104. 07 kg ha-1)، thymol (37. 4%)، terpinolene (44. 5%) and p-cymene (23. 9%) were obtained in plant density treatments of 83000، 250000، 125000، and 83000 plants per hectare، respectively. However، significant interaction effects were also observed on oil percentage (5. 37%)، oil yield (149. 5 kg per hectare)، percentage of thymol (40%)، percentage of terpinolene (49. 1%) and percentage of para-cymene (25. 6%).