Early-season weed competition can cost you

By Stephanie Karhoff, OSU Extension Field Specialist

By the time weeds emerge, it might already be too late. Early-season weed competition can significantly reduce corn and soybean yield potential, even when weeds are eventually controlled.

Field trials completed in 2009 and 2010 at the University of Guelph, The Ohio State University, and Colorado State University found that corn yield losses began as early as the V1 to V3 growth stages (Page et al., 2012). Delaying weed control beyond this point led to yield losses of up to 72% in some environments. Even when weed biomass was relatively low, the timing of weed emergence relative to the crop made a difference.

Early-season weed competition has a similar effect on soybean yield as well. A study across 64 site-years in Wisconsin found that glyphosate applications often occurred too late, typically at the V3 to V4 stage, when weeds were already 7.5 in tall on average (Fickett et al.,… Continue reading