The Influence of Fertilizers on the Production and Quality of Peppermint in Central Washington1

Sypnosis Oil quality and yield of peppermint were related to the plant nutrient status. Nitrogen, P, K, and S produced in that order decreasing influences on oil and hay yield. Menthol content of oil, especially in 1953, was decreased in those plants with increased nitrogen content, whereas menthofuran was increased. Leaf N was slightly more effective than leaf P in predicting menthol content and three times as effective in predicting menthofuran content. Menthol and menthofuran accounted for 76% of the variation in optical rotation of the oils in 1953. Menthol was more important in determining optical rotation in 1953.