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

Abstract EN

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.