Effect of Planting Date and Intercropping with Fenugreek (Trigonella foenum - graceum L.) on Yield and Essential Oil Content of Peppermint (Mentha piperita L.)

Peppermint (Mentha piperita L.) is one of the most important essential oil bearing plants. Satisfying the nutritional needs of a growing population whilst limiting environmental repercussions will require sustainable intensification of agriculture including intercropping systems. In order to investigate the effect of theses factors, a field experiment was conducted in a split plot arrangement based on randomized complete block design with three replications. Treatments were including planting dates (October 2, February 29 and April 29) as main plot and five replacement intercropping systems (fenugreek and peppermint sole crop and 1:1, 2:2 and 2:1 (two of fenugreek and one of peppermint) ratio assigned to sub plot. Yield, harvest index, phenol, essential oil and indices of advantage of intercropping were studied. Crops yield, essential oil and phenol content were influenced by planting date and intercropping systems. Results demonstrated that October 2 planting date showed the highest yield for both crops. A significant increase in essential oil content (% w/w) was found in February 29 and intercropping ratio 1:1. Even though biological yield of two crops was declined by intercropping, the advantage of intercropping system was higher than sole of fenugreek and peppermint. The highest land equivalent ratio and area time equivalent ratio were obtained from intercropping ratio of 1:1. The second harvest of peppermint had more yield and active substances than the first harvest. Therefore, it could be concluded that using of intercropping system and selection of best planting date are methods to optimize of the medicinal properties of crops. Intercropping ratio 1:1 and planting date October 2 will help to increase high value essential oil production and more benefit to peppermint/fenugreek growers and aroma industry.