Influence of Cereal Rye Termination Timing on Residual Herbicide Efficacy in No-Till Corn

Field experiments were conducted in 2017-2018 and 2018-2019 at three locations in Indiana to assess weed suppression by cereal rye and residual herbicide premixes in no-till corn. Cereal rye biomass ranged from 540 to 3700 kg ha -1 when terminated in late April and early May. When cereal rye termination was delayed until corn planting in mid-May to mid-June, cereal rye biomass ranged from 1710 to 6200 kg ha -1 . Early-season weed biomass was suppressed 27 to 84% by cereal rye residue in three of five site-years. Early-season weed biomass reduction by a residual herbicide premix was similar whether applied to cereal rye or non-cover crop treatments in four of five site-years. In one site-year, weed biomass reduction by a residual herbicide premix was 16% greater when applied to cereal rye compared to non-cover crop ground. Weed biomass decreased by approximately 12% for every 1000 kg ha -1 of additional cereal rye or wheat biomass, and peak weed biomass suppression was estimated to occur at 8000 kg ha -1 of cover crop biomass. Corn yield was similar in all treatments in all but one site-year, when a 57% yield reduction from cereal rye was observed in 2018 due to corn stand reduction from cereal rye competition. Overall, cereal rye did not reduce residual herbicide efficacy regardless of herbicide application timing.