Comparison of Weed Control, Yield, and Net Income in Conventional, Glyphosate‐Resistant, and Glufosinate‐Resistant Soybean

Abstract

Separate field experiments were conducted in central and southeast Missouri during 2009 and 2010 to evaluate the effect of preemergence (PRE) and postemergence (POST) herbicide programs on Palmer amaranth (Amaranthus palmeri S. Wats.) and waterhemp (Amaranthus rudis Sauer) control, soybean [Glycine max (L.) Merr.] yield, and net income in conventional, glyphosateresistant, and glufosinate-resistant soybean production systems. Visual control evaluations 10 wk after emergence at the waterhemp site revealed that all preemergence only applications (PRE-only) and preemergence followed by a postemergence applications (PRE fb POST) provided greater than 92% waterhemp control in either soybean system and at the Palmer amaranth site and all PREonly provided greater than 83% Palmer amaranth control across soybean systems. Averaged across all herbicide programs at both locations, glufosinate-resistant soybean provided the highest grain yield and net return followed by glyphosate-resistant and conventional soybean systems. Furthermore, with the exception of the conventional PRE-only program at the waterhemp site, all glyphosate-resistant soybean herbicide programs provided greater net return than all conventional herbicide programs. Collectively, the results from both trials indicate that programs containing PRE herbicide treatments provide the best opportunity for season-long control of waterhemp and Palmer amaranth and highest grain yields and net returns in conventional, glyphosate-resistant, or glufosinateresistant soybean systems. The results from these experiments also suggest that Palmer amaranth may be particularly difficult to control in conventional soybean systems. Problematic Weeds and Weed Management Systems Palmer amaranth and waterhemp, both members of the Amaranthus family, are two of the most troublesome agronomic weeds in the United States due to their extended period of emergence, rapid growth at high light intensities and temperatures, and prolific seed production (10,14,18,27). In Missouri, the most common pigweed (Amaranthus spp.) species Published in Crop Management DOI 10.1094/CM-2013-0028-RS © Plant Management Network 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. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Kristin K. Rosenbaum, Graduate Research Assistant, Division of Plant Sciences, 205 Waters Hall, University of Missouri, Columbia, MO 65211; Raymond E. Massey, Extension Professor, Department of Agricultural and Applied Economics, 223D Mumford Hall, University of Missouri, Columbia, MO 65211; and Kevin W. Bradley, Associate Professor, Division of Plant Sciences, 201 Waters Hall, University of Missouri, Columbia, MO 65211. Received 1 Aug. 2013. *Corresponding author (bradleyke@missouri.edu). Abbreviations: 1-pass POST, one-pass postemergence application; 1-pass POST W/Res, one-pass postemergence application with a residual herbicide; 2-pass POST, two-pass postemergence application; ALS, acetolactate synthase; POST, ; PRE, preemergence; PRE fb POST, preemergence followed by a postemergence application; PREonly, preemergence only application; WAE, weeks after emergence.