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

摘要

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. Treatmentsincluded 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 soybeanharvest. 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% atharvest. 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.