The study on the effect of irrigation levels and mulch application on growth indices and essential oil content of peppermint (Mentha piperita L.)

In order to study the effects of different irrigation regime and mulch types on growth indices and, essential oil content of peppermint (Mentha piperita L.) in 2010 in research field of Agricultural college of Ferdowsi University of Mashhad as factorial randomized complete block design was performed in four replicates. Irrigation treatments included three levels (100, 80 and 60 percent of water requirements calculated by evaporation pan class A and two types of mulch (black plastic and wood chips) and the uncoated control. Traits include inter-node distance, number of flowers/plant, branch number/plant, plant height, fresh weight, dry weight, chlorophyll content, leaf relative water content, leaf area, essential oil percentage and yield were evaluated during full flowering. The results showed that the effect of irrigation on fresh weight, dry weight, leaf relative water content and leaf area was significant (at 0.05 level). The effect of mulch on fresh weight, dry weight, leaf area, inter-node distance, number of branch and leaf relative water content was significant (at 0.05 level). Interaction between irrigation and mulch on inter-node distance, number of branches, fresh weight, dry weight, relative water content of leaves and leaf area and height were significant (at a 0.05 level). The effect of irrigation, mulch and interaction effects on traits such as flower number, chlorophyll content, percentage essential oil (at 0.05 level) was not significant.