Cotton Agronomy Journal  Volume 100, Issue 6  2008 1763 Published in Agron. J. 100:1763–1768 (2008). doi:10.2134/agronj2008.0036 Copyright © 2008 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. W ater is one of the most important limiting factors in proftable cotton production in the southeastern United States. Although Georgia receives on average 56 cm of rainfall during the growing season (i.e., 1 May–31 September; Southeast Regional Climate Center, 2002), the shallow, coarse- textured soils of the Coastal Plain along with erratic rainfall patterns allow episodic drought events to occur. Moisture defcit from these drought events can decrease yields and afect crop characteristics including increased fruit abortion and decreased fowering (Guinn and Mauney, 1984a, 1984b; Pettigrew, 2004). Overhead sprinkler irrigation of crops can alleviate the negative efects of moisture defcit and provide growers with a system that provides timely water application without requir- ing close supervision (Bordovsky and Porter, 2003; Krieg and Sung, 1986). Consequently, acreage in Georgia under sprinkler irrigation has increased 10-fold since 1970 (Harrison and Tyson, 2001). In 2004, about 550,000 ha of cropland in Georgia were irrigated using overhead irrigation systems (Hook et al., 2004). Water consumption from agriculture irrigation in Georgia in 2002 was 4.86 GL and accounted for 42% of the total water use for the state (Georgia Department of Natural Resources, 2003), making irrigation efciency an important production consideration. Water from overhead systems can be lost by droplet evaporation and drif (McLean et al., 2000; Ocampo et al., 2003) before reaching the soil surface. Tese processes can result in signifcant losses of water intended to be used by crops. Subsurface drip irrigation (SSD) has been sug- gested to be a more efcient irrigation method than overhead irrigation. Many studies of SSD irrigated crops have observed favorable yields and reductions in water application when compared with crops grown with other irrigation technologies (Bordovsky and Porter, 2003; Camp, 1998; Cetin and Bilgel, 2001). However, most of these studies have been performed in dry climates where irrigation has historically had a large infu- ence on yield. Subsurface drip irrigation research in the humid southeastern United States has shown some of the same positive efects as SSD irrigation in other parts of the country. In South Carolina, research has demonstrated that irrigation from SSD tube place- ments in alternate furrows could provide positive cotton yield efects over rain-fed cotton (Camp et al., 1997). Sorensen et al. (2003) showed that SSD-irrigated cotton had similar yields as overhead irrigated cotton in Georgia. Additionally, research in North Carolina reported cotton yields from SSD irrigation equal or better than yields from overhead sprinkler irrigation (Grabow et al., 2002; Nuti et al., 2006). Another possible beneft of SSD pertains to fruit abortion. Burke (2003) reported that overhead irrigation induced fower abortion when compared with drag sock irrigation where water did not contact open fowers. Is seems reasonable the indeter- minate growth habit of cotton may compensate for sprinkler- ABSTRACT Subsurface drip (SSD) is used as a water-efcient alternative to overhead irrigation in many crops. Tis study compared soil water, water use, crop maturity, lint yield, and fber quality of cotton ( Gossypium hirsutum L.) grown with SSD to cotton grown with overhead irrigation. Tree experiments were conducted at two Georgia locations in 2004 and 2005. Treatments consisted of overhead irrigated, nonirrigated, SSD matched to overhead irrigation rates (SSD Matched), and SSD based on soil water (SSD Fed). Cotton maturity was afected by irrigation treatment as nonirrigated cotton matured earliest, whereas overhead irrigated cotton matured latest. Subsurface drip irrigated cotton produced similar or higher lint yields than overhead irrigated cotton. Subsurface drip provided adequate soil water and irrigation amounts were 4.4, 8.2, and 0.5 cm less than overhead irrigation at the three locations. Water use efciency (WUE) of cotton SSD irrigated was 23 and 15% higher than overhead-irrigated cotton in two experiments. Irrigation method did not substantially afect fber quality; however, micronaire was higher in cotton from the SSD Fed treatment than cotton in the Overhead treatment in two locations. We conclude that SSD irrigation provides the same positive efects as overhead irrigation in cotton production while reducing irrigation water use and may allow for improved irrigation efciency. J.R. Whitaker, North Carolina State Univ., Williams Hall 4401D, P.O. Box 7620, Raleigh, NC 27695-7620; G.L. Ritchie, Univ. of Georgia, P.O. Box 748, Tifon, GA 31794; C.W. Bednarz, Texas Tech Univ. and Texas AgriLife Research, Box 42122, Lubbock, TX 79409; C.I. Mills, Texas Tech Univ., Box 42122, Lubbock, TX 79409. Manuscript T-4-593. Received 23 Jan. 2008. *Corresponding author (craig.bednarz@ttu.edu). Abbreviations: DAP, days afer planting; HVI, high-volume instrument; NACB, node with a harvestable boll; NAWF, nodes above the frst fower; SSD, subsurface drip irrigation; WUE, water-use efciency. Cotton Subsurface Drip and Overhead Irrigation Ef ficiency, Maturity, Yield, and Quality Jared R. Whitaker, Glen L. Ritchie, Craig W. Bednarz,* and Cory I. Mills Published November, 2008