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International Journal of Agronomy
Volume 2016, Article ID 8040235, 6 pages
Research Article

Glufosinate Rate and Timing for Control of Glyphosate-Resistant Rhizomatous Johnsongrass (Sorghum halepense) in Glufosinate-Resistant Soybean

Dean Lee Research and Extension Center, LSU AgCenter, Alexandria, LA 71302, USA

Received 18 November 2015; Accepted 31 January 2016

Academic Editor: Patrick J. Tranel

Copyright © 2016 Randall L. Landry 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.


Field studies were conducted over a three-year period (2011, 2012, and 2013) in Louisiana to evaluate the effect of glufosinate rate and timing on glyphosate-resistant (GR) rhizomatous johnsongrass control in glufosinate-resistant soybean. Treatments included glufosinate (0.5, 0.6, or 0.7 kg ai ha−1) applied alone POST1 (46 cm tall johnsongrass) and sequentially 3 (POST2) or 4 (POST3) wk after POST1 at 0.5 or 0.6 kg ha−1. Glufosinate (0.7 kg ha−1) applied POST1 controlled johnsongrass 77% at soybean harvest. Averaged across sequential application rate, delaying the sequential application from POST2 to POST3 increased control from 65 to 78% at harvest. Increasing sequential application rate from 0.5 to 0.6 kg ha−1 reduced johnsongrass heights 15% at harvest. Furthermore, delaying the sequential application from POST2 to POST3 reduced GR rhizomatous johnsongrass heights to 63% of the nontreated at harvest. Soybean yields were maximized following the POST1 application of glufosinate at 0.7 kg ha−1 (2670 kg ha−1) and by applying 0.6 kg ha−1 of glufosinate sequentially (2620 kg ha−1), regardless of sequential application timing. Maximum control and soybean yield were observed following glufosinate POST1 at 0.7 kg ha−1 followed by 0.6 kg ha−1 at POST3. This data indicates that glufosinate is an option for management of GR rhizomatous johnsongrass.