Evaluation of Tillage and Herbicide Interaction for Amaranthus Control in Cotton

Amaranthus control in cotton can be difficult with the loss of glyphosate efficacy, especially in conservation-tillage cropping systems. Research was conduction from 2006 to 2008 at EV Smith Research Center, Shorter, AL, to determine the level of glyphosate-susceptible Amaranthus control provided by four initial tillage and herbicide treatments, including 1) moldboard plowing followed by a single-pass disking and field cultivation plus pendimethalin at 1.2 kg ai ha−1 preplant incorporation (PPI), 2) two-pass disking followed by field cultivation plus pendimethalin at 1.2 kg ha−1 PPI, 3) no tillage including an application of pendimethalin at 1.2 kg ha−1 PRE, or 4) no tillage without pendimethalin in 2006. No further tillage practices or pendimethalin applications were utilized after study initiation. Initial tillage operations, including inversion with disking or disking twice, resulted in Amaranthus density of ≤ 4 plants m−2 and 47 to 82% control, whereas no-tillage treatments had ≥ 4 plants m−2 and 14 to 62% control. Subsequent applications of PRE herbicides included fluometuron at 1.68 kg ai ha−1 or prometryn at 1.12 kg ai ha−1 and provided 53 to 98% and 55 to 93% control, respectively, and reduced Amaranthus density compared to no PRE herbicide to