Effect of Nitrogen and Two Types of Green Manure on the Changes in Percentage and Yield of Peppermint (Mentha piperita) Essential Oil

Abstract

An experiment was conducted during 2015-2016 as a split factorial in a randomized complete block design (RCBD) with three replications. Experimental factors were nitrogen fertilizer at four levels 0, 50, 100 and 150 kg/ha as the main factor and two types of green manure. Alfalfa (Medicago sativa) and secale (Secale montanum) in two states (use and non-use) were considered as sub-factors. Medicago sativa and Secale montanum were cultivated as green manure in September 2015 and returned into the soil by ploughing at the fall of 2015. Thereafter, Mentha piperita was planted and the crop was taken care of in order to collect the samples. The highest increase of peppermint essential oil percentage and essential oil yield in different treatments resulted from the application of 150 kg/ha of pure nitrogen with 0.35% and 45.60 kg/ha, as well as the use of M. sativa with 0.43% and 55.80 kg/ha, the use of S. montanum with 0.44% and 49.50 kg/ha, respectively. The highest essential oil percentage and essential oil yield were recorded under the influence of the double interaction use of 150 kg/ha of pure nitrogen and use of green manure of M. sativa with average 0.62% and 80.30 kg/ha, respectively. The triple interaction of experimental factors on traits tested showed that nitrogen treatment of 150 kg/ha with M. sativa and S. montanum produced the highest percentage of essential oil and essential oil yield of average 0.73% and 91.65 kg/ha, respectively.