Table of Contents
ISRN Agronomy
Volume 2012, Article ID 947395, 8 pages
Research Article

Influence of Soybean (Glycine max) Population and Herbicide Program on Palmer Amaranth (Amaranthus palmeri) Control, Soybean Yield, and Economic Return

Department of Crop Science, North Carolina State University, P.O. Box 7620, Raleigh, NC 27695-7620, USA

Received 1 July 2012; Accepted 7 August 2012

Academic Editors: D. Chikoye, O. Ferrarese-Filho, Y. I. Kuk, and W. P. Williams

Copyright © 2012 Amy E. Hoffner et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Palmer amaranth (Amaranthus palmeri S. Wats) has become one of the most prominent and difficult weeds to control in soybean (Glycine max (L.) Merr.) in North Carolina. A survey was conducted in North Carolina during fall 2010 to estimate the magnitude of this problem. Palmer amaranth was present in 39% of 2,512 fields representing 0.24% of soybean ha in North Carolina. In recent years, growers have reduced soybean seeding rates in an effort to decrease production costs associated with technology fees. However, given the increase in prevalence of Palmer amaranth and the difficultly in controlling this weed due to herbicide resistance, growers may need to reconsider reductions in seeding rates. Therefore, research was conducted during 2010 and 2011 to determine if Palmer amaranth control, soybean yield, and economic return were affected by soybean plant population, preemergence (PRE) and postemergence (POST) herbicides, and herbicide resistant traits (glufosinate-resistant and glyphosate-resistant cultivars). Applying PRE or POST herbicides and increasing soybean population increased Palmer amaranth control, soybean yield, and economic return when compared with POST herbicides only or when lower soybean populations were present. Efficacy of glufosinate and glyphosate did not vary in most instances, most likely because these herbicides were applied timely, and the frequency of glyphosate resistance did not exceed 10% in these fields.