Weeds compete with crops for resources like sunlight, nutrients, and water. In a stressful growing environment like we experienced in 2012, the effects of weed competition can be extremely visual and magnified to the point of crop death. As control measures are delayed in the year, the more visual crop stress symptoms become, and the more yield will be lost.
This video shows a general view of how weed management can affect soybean and corn growth at various degrees from slight stunting to complete crop loss. One tip is to control weeds earlier in the season to avoid weed competition. When that fails, scout for weed control problems and make detailed notes about where patches of weeds are in fields. This will help with interpreting yield monitor maps and devising best management practices for controlling those weed species in the future.
Special thanks to Dan Heider and the Diagnostic Crop Diagnostic Training Center for use of his field plots at Arlington Agricultural Research Station.
For more information, contact your county Extension office.