VOLUME 84 Advisory Board John S. Boyer University of Delaware Paul M. Bertsch University of Georgia Ronald L. Phillips University of Minnesota Kate M. Scow University of California, Davis Larry P. Wilding Texas A&M University Emeritus Advisory Board Members Kenneth J. Frey Iowa State University Eugene J. Kamprath North Carolina State University Martin Alexander Cornell University Prepared in cooperation with the American Society of Agronomy Monographs Committee Diane E. Stott, Chair Lisa K. Al-Almoodi David D. Baltensperger Warren A. Dick Jerry L. Hatfield John L. Kovar David M. Kral Jennifer W. MacAdam Matthew J. Morra Gary A. Pederson John E. Rechcigl Diane H. Rickerl Wayne F. Robarge Richard Shibles Jeffrey Volenec Richard E. Zartman Edited by Donald L. Sparks Department of Plant and Soil Sciences University of Delaware Newark, Delaware 2004 Amsterdam · Boston · Heidelberg · London · New York · Oxford · Paris · San Diego San Francisco · Singapore · Sydney · Tokyo ELSEVIER B.V. Sara Burgerhartstraat 25 P.O. Box 211, 1000 AE Amsterdam, The Netherlands ELSEVIER Inc. 525 B Street Suite 1900, San Diego CA 92101-4495, USA ELSEVIER Ltd The Boulevard Langford Lane, Kidlington Oxford OX5 1GB, UK ELSEVIER Ltd 84 Theobalds Road London WC1X 8RR UK q 2004 Elsevier Inc. All rights reserved. This work is protected under copyright by Elsevier Inc., and the following terms and conditions apply to its use: Photocopying Single photocopies of single chapters may be made for personal use as allowed by national copyright laws. Permission of the Publisher and payment of a fee is required for all other photocopying, including multiple or systematic copying, copying for advertising or promotional purposes, resale, and all forms of document delivery. Special rates are available for educational institutions that wish to make photocopies for non-profit educational classroom use. Permissions may be sought directly from Elsevier’s Rights Department in Oxford, UK: phone (+44) 1865 843830, fax (+44) 1865 853333, e-mail: [email protected] Requests may also be completed on-line via the Elsevier homepage (http://www.elsevier.com/locate/permissions). In the USA, users may clear permissions and make payments through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA; phone: (+1) (978) 7508400, fax: (+1) (978) 7504744, and in the UK through the Copyright Licensing Agency Rapid Clearance Service (CLARCS), 90 Tottenham Court Road, London W1P 0LP, UK; phone: (+44) 20 7631 5555; fax: (+44) 20 7631 5500. Other countries may have a local reprographic rights agency for payments. Derivative Works Tables of conten