Effects of Sulfur Application Rates and Foliar Zinc Fertilization on Cotton Lint Yields and Quality

Published in Agron. J. 103:1794–1803 (2011) Posted online 26 Sept 2011 doi:10.2134/agronj2011.0166 Copyright © 2011 by the American Society of Agronomy, 5585 Guilford 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. S is an essential macronutrient in plant growth and development (Marschner, 1986). Sulfur deficiencies in crops have increasingly occurred due to less to no addition of S to soil because of increased use of S-free fertilizers, greater S removal from soil by crops with enhanced yield and under more intensive cropping systems, less S deposition to soil from the atmosphere because of tightened environmental regulations, and declined use of S-containing pesticides (Morris, 1986; McGrath and Zhao, 1995; Scherer, 2001). Soils with coarse texture, low organic matter, and good drainage are often S deficient (Scherer, 2001; Savoy, 2005; Waddoups, 2011). In addition, conservation-till soils are more prone to S deficiency since soil temperatures are usually lower (Hill, 2000). Low soil temperatures reduce the mineralization of organic S to sulfate, and thus increase the probability of crop responses to S fertilization (Havlin et al., 2005). Many areas in North America are expected to need S fertilization for optimal crop productivity (Chen et al., 2005) according to projections of S status modeling using crop S requirements, soil characteristics, atmospheric S deposition, and meteorological data (McGrath and Zhao, 1995). Since S exists in soil mainly as organic S, which is unavailable, or as sulfate, available S is expected to be low in the Cotton Belt region of the United States due to the hot, humid weather conditions and the increased likelihood of sulfate leaching. Sulfur deficiencies in cotton have been reported in the Cotton Belt region as early as the 1940s (Younge, 1942; Harris et al., 1945), and more investigations in S on cotton were conducted later (Barton et al., 1982; Mahler, 1989; Mascagni et al., 1992; Mullins and Burmester, 1993; Delgado and Amacher, 1995; Mullins, 1998). However, little information has been published on S fertilizer use in the Cotton Belt region during the past decade (Dunn et al., 2008). Information is particularly lacking on S-deficiency effects on cotton yield components. In contrast, S deficiencies have been increasingly reported as an important limiting factor in high yields and quality of other crops in the United States during recent years (Chen et al., 2005, 2008; Kalmbacher et al., 2005; Pavlista, 2005; Rehm, 2005; Malhi et al., 2007). Mullins (1998) documented that an annual application of 22 kg S ha–1 increased cotton lint yields by an average of 21% over 3 yr on a loamy sand soil in Alabama; S application at pre-planting produced equal or better performance than S application at first square; S sources generally did not differ in effects on lint yield; lint quality, except fiber length, was not affected by S application. Dunn et al. (2008) reported that cotton lint yields responded significantly to S fertilization on a fine sand soil but not on a silt loam soil in Missouri. Mascagni et al. (1992) found that even though conditions were conducive to the development of S deficiency, cotton yields were not affected by S application on two sandy soils in Arkansas. Snyder et al. (1993) observed that seedcotton yields had no response to mid-season S fertilization in Arkansas. Therefore, it is obvious that more information is needed about the responses of high-yielding cotton cultivars to S applications, particularly, under conservation tillage systems. Zinc is essential for plant growth and development, but the amount of Zn required by plant is not large. Zinc is involved in several important metabolic processes in plants (Vallee and Auld, 1990), such as membrane integrity (Cakmak and Marschner, AbStrACt