Aromatic Plants Agronomy Journal  Volume 101, Issue 1  2009 1 Published in Agron. J. 101:1–10 (2009). doi:10.2134/agronj2007.0144 Copyright © 2009 by the American Society of Agronomy, 677 South Segoe Road, Madison, WI 53711. All rights reserved. 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. I rrigation with treated effluent is an unavoid- able practice in arid and semiarid regions, where shortage of fresh water restricts agricultural production. Te largest source of marginal water for agriculture is secondary- treated munici- pal sewage water. Tis water contains higher levels of salts such as bicarbonates, Na, Cl, and sulfates than fresh water, that may reduce plant performance and yield quality. Treated efuents are also characterized by higher levels of organic matter, total suspended solids (TSS), nutrients, microelements, and micro- organisms than the potable water from which they originated, which may afect the irrigated plants (Feigin et al., 1991). Efuent-based agriculture therefore depends on identi fcation of crops that are able to maintain high performance under the suboptimal conditions imposed by this low-quality treated efuent water. Perennial aromatic plants are cultivated as cash-crops for fresh or dry herb production, or as a source of essential oils and natural antioxidants. Tese summer crops require substantial amounts of water, up to 7000 to 9000 m 3 ha –1 throughout the growing season, to satisfy their potential for intensive biomass production (Putievsky et al., 1990; Dudai, 2005). Hundreds of hectares of these crops are required to facilitate an economi- cally viable industrial production system. Terefore, shortage of fresh water for irrigation in arid and semiarid regions restricts utilization of aromatic plants as industrial crops. Replacement of fresh water with treated efuent for irrigation of these plants could promote development of large-scale production systems for biomass, essential oil, and natural antioxidants in arid and semiarid zones. Cultivation of aromatic plants for essential oils is suitable for irrigation with treated efuents because the heat applied during oil extraction eliminates human bacterial pathogens originat- ing in the efuents and alleviates health concerns. Additionally, the essential oil, which is extracted mainly by steam distilla- tion, will be free of inorganic ion contaminants such as heavy metals originating from the efuents, which may accumulate in the plant tissues and the soil. Oregano and rosemary are two important aromatic crops. Tese perennial members of the Lamiaceae family, in addition to their essential oil yield production, are a good source for natural phenolic antioxidants (Putievsky et al.,1988; Ravid et al., 1997; Munné-Bosch and Alegre, 2001, 2004; Chun et al., 2005; Skerget et al., 2005). No information is currently avail- able concerning the efect of irrigation with treated municipal efuent on growth and development of these crops, their essen- tial oil yield or their antioxidant production. Salinity and heavy metals contained in treated efuents may increase antioxidant activity and reactive oxygen species (ROS) production in plants. Increased antioxidant content and antioxidant activity were demonstrated in many plants in response to environmental stresses (Mittler, 2002). In rose- mary, water stress induced changes in antioxidants which were ABSTRACT Shortage of water throughout the world dictates utilization of marginal water for irrigation. Treated urban wastewater is a com- mon alternative water source for irrigation in arid and semiarid regions. In this study we aimed to evaluate the efect of irrigation with secondary-treated efuent on plant development, essential oil yield, antioxidant activity and selected antioxidant pheno- lic compounds in two commercial cultivars of the aromatic species, oregano ( Origanum vulgare L.) and rosemary (Rosmarinus ofcinalis L.). Te applied treated efuent contained higher levels of Na, Cl, HCO 3 –1 , P, K, NH 4 +1 , NO 3 –1 , Ca+Mg, B, Mn, and Fe than the local potable water used as control, and were characterized by higher values of electrical conductivity (EC), pH, and sodium absorption ratio (SAR). Since efuent efects on plants can become apparent only following several years of exposure, the plants were exposed to the water treatments for 3 yr. Despite the di ferences in water quality, the efuent did not afect yield quantity and quality in either crop. Plant morphological development, biomass production, percent dry leaves of the total bio- mass, quantity and composition of the essential oil produced, antioxidant activity, and contents of selected antioxidant-phenolic compounds were not afected by irrigation with treated efuent compared with potable water. Our results demonstrate that both oregano and rosemary are suitable as industrial crops for essential oil and antioxidant production under irrigation with secondary-treated municipal efuent because their yield quantity and quality were not afected. N. Bernstein, Institute of Soil Water and Environmental Science, Volcani Center, POB 6, Bet-Dagan, 50-250, Israel; D. Chaimovitch and N. Dudai, Aromatic, Medicinal and Spice Crops, ARO, Newe Ya’ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel. Received 17 Apr. 2007. *Corresponding author (nativdud@agri.gov.il). Abbreviations: DM, dry mass; EC, electrical conductivity; ROS, reactive oxygen species; SAR, sodium absorption ratio. Effect of Irrigation with Secondary Treated Ef fluent on Essential Oil, Antioxidant Activity, and Phenolic Compounds in Oregano and Rosemary Nirit Bernstein, David Chaimovitch, and Nativ Dudai* Published January, 2009