Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/17/2009
Publication Date: 8/1/2009
Citation: Zheljazkov, V.D., Cantrell, C.L., Astatkie, T., Ebelhar, W.M. 2009. Peppermint Productivity and Oil Composition as a Function of Nitrogen, Growth Stage and Harvest Time. Agronomy Journal. 102(1):124-128. Interpretive Summary: Peppermint (Mentha piperita) is an aromatic plant grown for production of essential oil, a major aromatic agent, or dry leaves, which are used in herbal teas. Peppermint essential oil is used in a number of consumer products such as chewing gum, toothpaste, mouth washes, in pharmaceuticals, confectionary and aromatherapy. Peppermint is currently not a common crop in the southeastern USA. Recently, there has been an interest towards peppermint as an essential oil crop for this region. A field experiment was conducted in 2007 in Mississippi, to determine the effect of N (0 and 80 kg'ha-1), location (Verona and Stoneville), and harvesting stage (bud formation and flowering) on peppermint productivity, oil content, and composition. From this preliminary work at two locations it has been demonstrated that location and harvesting stage had significant effects on peppermint oil yields. Peppermint essential oil yields were maximized at bud formation. Location and harvesting stage had significant effects on the concentrations and the yields of the major peppermint oil constituents. The range of the quantified concentrations of peppermint oil constituents under Mississippi climate were: (-)-menthol at 26 – 30 %, (-)-menthone at 14 – 21 %, (+)-menthofuran at 5 – 11 %, and eucalyptol at 3 – 4 % of total essential oil. Overall, peppermint biomass yields, oil content and oil yields, and the concentrations of the major oil constituents in this study were similar to those found in the literature. This study demonstrated peppermint can be successfully grown as an essential oil crop in Mississippi, and possibly the southeastern USA.
Technical Abstract: The commercial production of peppermint (Mentha x piperita L.) is concentrated in more northern latitudes worldwide (north of the 41st parallel), including the United States. This 2-yr. field study in Mississippi evaluated the effect of N (0, 80, and 160 kg/ha), growth stage (bud formation and flowering), and harvest time or cut (first cut in mid-July, second cut beginning of October) on peppermint yields, oil content, and composition. Biomass and oil yields were higher from the first cut than from the second. Overall, N increased biomass and oil yields. Contrary to literature reports that peppermint requires long days north of the 41st parallel to reach flowering, peppermint in Mississippi (at 34 degrees,42'22" N lat) did reach flowering. The average oil yields at bud formation and at flowering were 165 and 122 kg/ha, respectively, and were greater than the average peppermint essential oil yields for the United State in 2008. Generally, (-)-menthol concentration in the oil from the 2007 harvest was lower than in the oil from the 2008 harvest. The average (-)-menthol concentration in the oil from the fertilized plots harvested at flowering in 2008 was 43 to 46%, but (-)-menthol in the other treatments was below 37%. Our results suggest the first harvest in Mississippi should be delayed until the end of July to promote conversion of (-)-menthone to (-)-menthol. Peppermint could provide two harvests per growing season under the Mississippi climate, with oil yields and composition similar to those from other peppermint production regions.