The Roundup Ready trait has more weed control value in soybeans than in corn. That's the conclusion after 10 years of research by University of Minnesota weed scientist Jeff Gunsolus. And it's one of the reasons Gunsolus recommends that corn and soybean producers diversify their weed management strategies.

“Soybeans can tolerate early emerging annual weeds for a longer time period than corn can,” says Gunsolus.

“In general, weeds that emerge with corn must be controlled within two to five weeks after emergence to prevent a yield loss. Soybeans generally tolerate about four to six weeks of competition from weeds. This extra one to two weeks can be very important when you're trying to control weeds over a large number of acres and you can't spray a field because of moisture or wind,” he says.

Gunsolus says soybeans are also better at shading out late-germinating weeds and preventing late-emerging weed escapes. This is important when using a herbicide that lacks soil-residual weed control.