"We were able to identify the highest yielding fields as those that used interrow cultivation, a sweet corn hybrid that matured in less than 84 days, and were in the northern part of the production region," said Williams. "One break in latitude came near 42 degrees north and that's right about the border line between Illinois and Wisconsin. Fields further north also had lower weed interference and produced fewer weed seeds."
For those fields that didn't do as well, weed interference was the best indicator of yield loss. During the field visits, Williams and his team also predicted yield loss due to weeds. "Ultimately, over half of the fields in the Midwest had a level of weed interference sufficient to cause yield loss," Williams said.
Planting the weediest fields in June or July was one recommendation for more successful weed management that surfaced from the study. When the fields are cleaner, earlier planting is actually beneficial for crop growth.
Williams said that information gained from the regional study was consistent with some of the controlled research in experimental field studies they've done. "We've tested various planting dates and the crop tolerates common cornbelt weeds better in a June or July planting than it does in an April or May planting. Annual weeds that emerge and then are taken out when the soil is turned over for planting, you don't have to worry about again."
Another factor that played a major role was water supply. "We have no control over rainfall, of course, but we noticed that those conditions with poor water supply had bigger problems with weeds. Soil-active herbicides aren't nearly as effective when weed seedlings are emerging in dry soil. Likewise, drought conditions reduce effectiveness of postemergence herbicides."
One surprising observation from the dat
|Contact: Debra Levey Larson|
University of Illinois at Urbana-Champaign