Vahideh Moghaddasi-Kozahkonan - Department of Horticultural Sciences, Faculty of Agriculture, Miyaneh Branch, Islamic Azad University, Miyaneh, Iran.
Mehrdad Akbarzadeh - Department of Horticultural Sciences, Faculty of Agriculture, Miyaneh Branch, Islamic Azad University, Miyaneh, Iran.
Shahram Shahrokhi- Khangah - Department of Horticultural Sciences, Faculty of Agriculture, Miyaneh Branch, Islamic Azad University, Miyaneh, Iran.

Peppermint (Mentha piperita L.) belongs to the family Lamiaceae. It is one of the important medicinal plants that are used in the pharmaceutical, food, and cosmetics industry. Because of it’s important in mentioned industries an experiment carries out in order to investigate the effect of vermicompost fertilizer on essential oil of peppermint. The treatments were vermicompost fertilizer levels (0, 5, 10 ton/ hectare). The experiment was done in Khoy, Iran. Characteristics were measured including oil yields (v - w), menthol content and essential oil content. The results showed that vermicompost fertilizer treatments had significant (P<0.01) effect on essential oil content, volumetric efficiency oil and weight efficiency oil. Although, vermicompost application had no significant effect on menthol content of essential oil there observed a difference between vermicompost treatments and control and menthol amount of the vermicompost treated plants were higher than control. In conclusion, according to the results, we suggest vermicompost application to increase clean essential oils in peppermint.