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Managing weeds with cover crops requires a lot of biomass

A soybean researcher says cover crops can be another mode of action for controlling weeds, but it will take a lot of biomass.

Shawn Conley says University of Wisconsin research through weed scientist Rodrigo Werle shows it takes almost five-thousand pounds of dry matter to effectively minimize waterhemp competition with crops.  Conley says one of his projects adds supplemental nitrogen for the cover crop. “By adding springtime nitrogen, a relatively small amount of about 25 pounds of N, we’re able to add anywhere from one thousand to 25-hundred pounds of biomass to that system and effectively, what that allows us to do is use cover crop as another mode of action for weed control.”

Conley says timely termination of cover crops makes a big difference in yields. “We can plant soybeans green and as long as we terminate within five days past planting, there’s a pretty minimal yield penalty, however, if we want to keep that cover crop longer, later, again to build more biomass, then we do acrue some form of a yield penalty.”

Conley says their research shows that planting a later maturity group soybean minimizes the yield loss on fields with cover crops terminated between five days and two weeks after planting. “I think what’s going on there is we have a longer reproductive time frame, so that plant is in a reproductive time frame longer and later in the season so we can take advantage of late-season rainfall events.”

Conley says they are entering the second year of their study of soybeans after cover crops, and more data will be available next fall.

AUDIO: Shawn Conley discusses managing weeds with cover crops with Brownfield’s Larry Lee