Cotton 1032 Agronomy Journal  Volume 102, Issue 3  2010 Published in Agron. J. 102:1032–1036 (2010) Published online 5 Apr. 2010 doi:10.2134/agronj2009.0474 Copyright © 2010 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights re- served. 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. T he Southern High Plains of Texas, charac- terized by hot periods that may last from April through October, provides highly favorable conditions for cotton growth and development. However, within this growing period, a relatively low annual average rainfall of 475 mm and a relatively high average potential evapotranspiration of 1000 mm results in water supply being a limiting factor for cotton in this region. Tus, information about how to maximize yield with limited water is needed. Furthermore, planting seed costs are currently higher than in the past due to advances in transgenic technology and the adoption of seed patents. A proper plant density may not only maximize cotton yield and fber quality for a given level of available water but may also reduce inputs by reducing excessive plant density. Current research has shown that boll size and boll number per unit land area are readily infuenced by irrigation rate (Pettigrew, 2001). Additionally, Bednarz et al. (2000) have shown that the number of bolls per plant and size of the bolls were infuenced by plant density. Worley et al. (1974) indicated that boll number per unit land area was the largest contributor to lint yield, followed by seed number per boll and lint mass per seed. Harrell and Culp (1976) suggested that more seeds per boll may be desirable due to the greater amount of surface area for lint production within the boll. Bridge et al. (1973) reported a general change to smaller bolls, smaller seeds, and higher lint percentage in successful Delta cultivars. Miller and Rawlings (1967) also found that, as yield increased by selection, lint percentage and seeds per boll increased while boll and seed size decreased. Tese fndings illustrate that within-boll yield components have evolved as a result of selection for increased lint yield. Are within-boll yield components infuenced by irrigation and plant density as well? If so, it should be possible to identify crop management practices that may capitalize on the most basic yield components. Moreover, Bednarz et al. (2006) reported that within-boll yield components difer among cultivars. Terefore, it is reasonable to assume that within-locule yield components difer among cultivars as well. Te objective of this study was to determine how yield components in two contemporary cotton cultivars were altered through irrigation and plant density management. MATERIALS AND METHODS Cultural Practices Experiments were conducted in 2006 and 2007 at the Agricultural Complex for Advanced Research and Exten- sion Systems (AG-CARES) facility in Lamesa, TX on an Amarillo fne sandy loam (fne-loamy, mixed, superactive, thermic Aridic Paleustalfs). All treatments were arranged in a split-split plot design with three replications where irriga- tion rate (6.33 and 4.32 mm d –1 ) was the main plot, variety (‘FM9063B2RF’– Bayer CropScience, Research Triangle, ABSTRACT Cotton ( Gossypium hirsutum L.) lint yield is integrated through whole-plant and within-boll yield components. Crop management prac- tices such as irrigation and plant density may impact yield. Tus, yield dynamics due to irrigation and plant density may result from changes in the most basic yield components. Tis study investigated how within-boll yield components are altered through irrigation and plant densities. Field experiments were conducted at the Agricultural Complex for Advanced Research and Extension Systems in Lamesa, TX in 2006 and 2007. Two contemporary cotton cultivars were arranged in a split-split plot design with irrigation rate as the main plot, cultivar as the subplot, and plant density as the subsubplot. Plants from 3 m of one row were removed from each plot and hand harvested by fruiting position. Ten frst fruiting position bolls from nodes 9 and 14 had their seeds separated by locule position. Seed number, mass and surface area, and lint mass and fber number for each seed position were recorded. Individual seed surface area and mass increased as irrigation increased and plant density decreased. Seeds per locule increased with increased irrigation and decreased plant density. Supe- rior within-locule yield components occurred in seed positions between the base and midpoint of the locule. Moreover, fber number per unit seed surface area was not altered by any treatment, indicating it is probably a heritable yield component. Irrigation rate and plant density efects on cotton yield components occurred at the levels of the plant, within the boll, and even within the locule. L. Feng, Chinese Academy of Agricultural Science, Cotton Research Institute, Anyang, Henan, China 455000; V.B. Bufon and C.I. Mills, Texas Tech Univ., Box 42122, Lubbock, TX 79409; E. Hequet, Texas Tech Univ. and Texas AgriLife Research, Box 45019, Lubbock, TX 79409; J.P. Bordovsky, Texas AgriLife Research, 823 W US HW 70, Plainview, TX 79072; W. Keeling and R. Boman, Texas AgriLife Research, 1102 East FM 1294, Lubbock, TX 79403; C.W. Bednarz, Texas Tech Univ. and Texas AgriLife Research, Box 42122, Lubbock, TX 79409. Journal article no. T-4-606. Received 17 Nov. 2009. *Corresponding authors (craig.bednarz@ttu.edu). Abbreviations: SDI, subsurface drip irrigation. Effects of Irrigation and Plant Density on Cotton Within-Boll Yield Components Lu Feng, Vinicius B. Bufon, Cory I. Mills, Eric Hequet, James P. Bordovsky, Wayne Keeling, Randy Boman, and Craig W. Bednarz* Published May, 2010