Effects of harvest time and mycorrhiza fungus application on quantitative and qualitative yield of thyme (Thymus vulgaris L.) essential oil at different irrigation levels

To evaluate the effects of mycorrhizal fungus Funneliformis mosseae application and harvest time on the quantity and quality of thyme (Thymus vulgaris L.) essential oil in the different irrigation regimes, a field experiment was carried out as a split-split plot in a randomized complete blocks design (RCBD) with 12 treatments and three replications at the Agriculture Faculty, University of Maragheh, Iran, in 2019. The factors and their levels included 1- the main factor: irrigation regime at three levels of irrigation after 20% (W20 as control), 50% (W50 as moderate stress), and 80% (W80 as severe stress) of maximum allowable depletion, 2- the subfactor: application and non-application of mycorrhiza, and 3- sub-sub factor: harvest time at two levels of June harvest (first harvest) and September harvest (second harvest). The results demonstrated that the highest amounts of plant height, canopy diameter, and dry matter yield of thyme were obtained in the W20 (control)+ application of mycorrhiza fungus+ first harvest treatment. In addition, the highest essential oil content was recorded in W50 followed by W80, which were 38.2 and 23.7% higher than W20 (control), respectively. Also, the application of mycorrhiza fungus increased the essential oil of thyme by 8.5% compared to the non-application of fungus. The highest and lowest content of thymol, γ-terpinene, and p < /em>-cymene were obtained in W50 and W20, respectively. Also, the application of mycorrhiza fungus increased the amount of mentioned compounds, respectively by 3.8%, 3.9%, and 7.1% compared to the non-application of fungus. Overall, it can be concluded that W50 (moderate stress) along with the application of mycorrhizal fungus F. mosseae improved the essential oil quality and quantity of thyme.