Some Iowa growers use Roundup Ready corn as buffer strips between their regular corn and Roundup Ready soybeans, reports Bob Hartzler, Iowa State University extension weed specialist.

"They buy a couple of bags of Roundup Ready corn and plant that adjacent to their Roundup Ready beans. That eliminates the concern of drift and solves a lot of weed problems," says Hartzler.

"There are obvious advantages to these approaches. The only concern from my viewpoint is relying on one tactic for weed control so weeds are going to adapt quicker," he cautions.

He says applying the same herbicide year after year will result in weed shifts.

"We just can't predict when it's going to happen - five years or 10 years down the road, who knows? And maybe it won't be a big problem at that time; maybe by then we can add somethingto the spray tank to solve it."