No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. S cotch and Native spearmint are grown as essential oil crops in many parts of the world (Bienvenu et al., 1999;Lawrence, 2006). Both Scotch and Native spearmints have been used in the production of essential oils, teas, and to fl avor foods, prepared dishes, and drinks. Spearmint essential oils are used in the food and pharmaceutical industries and are found in various consumer products including chewing gum, toothpaste, mouthwashes, as well as in pharmaceuticals, confectionary, and aromatherapy (Mint Industry Research Council, 2009). Both whole essential oils and individual essential oil constituents such as (-)-carvone have antimicrobial properties (Aggarwal et al., 2002;de Carvalho and Da Fonseca, 2006;Chao et al., 2000;Kanatt et al., 2008;Rafi i and Shahverdi, 2007;Rasooli et al., 2009;Sivropoulou et al., 1995;Sokovic et al., 2009).Th e midwestern and northwestern United States are considered ideal for spearmint production (USDA-NASS, 2009). In 2008, the United States produced 1.09 million kg of spearmint oil, and the average essential oil yields for the same year were 132 kg/ha (USDA-NASS, 2009). With increased ethanol production from corn (Zea mays L.), some U.S. spearmint farms have recently switched to growing corn to meet the demands of ethanol production. According to the MIRC, there remains a current market for spearmint oil in the United States (R. Lundy, the MIRC, personal communication, 2008). Th e continued market for spearmint oil in the United States off ers an opportunity for growers in the Southeast to capitalize on the spearmint essential oil market. However, spearmint production practices in the Southeast have not been scientifi cally assessed. In this study, we evaluated the eff ects of N application rate and cut (harvest time) on Scotch and Native spearmint herbage yields, essential oil content, oil composition, and major oil constituent yield [(-)-carvone, (R)-(+)-limonene, and eucalyptol] on a per area basis. MATERIALS AND METHODS Field ExperimentsWhile spearmint seed is available for home gardeners, the two species are natural hybrids (Tucker and Fairbrothers, 1990;Tucker, 1992) and their subsequent progeny may produce plants with diff erent phenotypes or chemical composition. Th erefore, commercial spearmint cultivars for essential oil production in the United States and abroad are propagated only vegetatively (Ellis and Stevenson, 1950;Lawrence, 2006;Tucker and Fairbrothers, 1990;Yankuloff et al., 1996). To minimize pest and disease pressure in our studies, we obtained certifi ed virus-free planting material of Scotch and Native spearmints from the Summit Plant Laboratories, Inc. (Fort Collins, CO). Spearmint plants from each cultivar were equal in size, (approximately 10 cm high), and each had several pairs of leaves. Th e spearmint plant...

A gronomy J our n al • Volume 10 0 , I s sue 3 • 2 0 0 8 635

Nitrogen (N) and potassium (K) fertility management of maize (Zea mays L.) in the humid subtropical Mississippi Delta may differ from a temperate climate because of its use in rotation with cotton (Gossypium hirsutum L.), soil temperatures rarely falling to 08C, and heavy winter rains that facilitate nutrient losses. An experiment to determine the [N] (concentration ¼ [ ]), phosphorus [P], [K], calcium [Ca], magnesium [Mg], iron [Fe], manganese [Mn], zinc [Zn], and copper [Cu] and their total contents plant 21 of maize grown in rotation with cotton, using N fertility levels of (134, 179, 224, 269, and 314 kg N ha 21) in combination with K fertility levels of (0, 45, 90, and 134 kg K ha 21) was conducted in 2000 and 2001 at Tribbett, MS. Ear leaves, immature ears, and husks collected at growth stage R2 and grain and stover collected 21 days after R6 were dried, weighed, and analyzed for nutrient concentration. Plots were also harvested for yield, kernel weight, grain bulk density, and harvest index (HI). Increased [N] values of about 1.3 mg g 21 occurred in all organs except the stover between 134 and 314 kg N ha 21 N fertility. Stover [N] increased approximately 3.0 mg g 21 within the same N fertility range. Total N content of ear leaves, grain, and stover increased by about 11.0, 550.0, and 730.0 mg plant 21 , respectively, with N fertility increased from 134 to 314 kg N ha 21. Yields, kernel weights, grain bulk densities, and harvest indices also increased with added N fertility. Several micronutrient concentrations and contents increased as N fertility increased.