Soybean growers in the earliest-maturity zones have pretty much had to watch as farmers to their south have reaped the benefits of Roundup Ready (RR) varieties. No more.

"For the 2000 growing season we will have three new Roundup Ready varieties in Group 0 and two in early Group I," reports Trent Leopold, Asgrow brand manager. "This is our first major move into these maturities."

Other seed companies also are on board with super-early RR varieties. And many of the new releases possess good yield and agronomic qualities, along with the RR gene.

"Until recently, Roundup Ready varieties in the earliest maturities generally had some yield lag and other agronomic limitations, compared to conventional varieties," notes Alex Renk, vice president of Renk Seed Co. "Now there is only about a 1.5-bu yield difference, based on what we have seen."

That lag should disappear completely under a straight Roundup program, says Renk. He points out that one of the beauties of RR varieties is that Roundup does not set back the plants as other herbicides often do. That's especially important in the far North with its limited growing season.

"Most of our early Roundup Ready varieties have good tolerance to iron chlorosis," notes Asgrow's Leopold. "Many Northern growers need that protection."

The RR varieties will give those growers more flexibility since they fit well in rotation with wheat and sugar beets, Leopold adds.

Ron Staples, who grows 400 acres of soybeans near Morris, MN, may go 100% RR in 2000. He grew 150 acres of RR seed beans in 1998 and 320 acres in '99.

"One of our main reasons for planting Roundup Ready beans is to control Canada thistle and milkweed," Staples explains. "Our crop consultant told us, 'Don't just hurt them, control them.' So that is what we have done the past two years."

Staples has nailed those tough perennial weeds with two applications of Roundup. He has browned them with the first application, at 1 qt/acre, then finished them off with a 24-oz application.

"Overall, the weed control with Roundup has been excellent," Staples reports. "The Roundup Ready beans have been the cleanest I have ever raised. And we didn't need to apply anything specific to control Canada thistle and milkweed in corn that followed those beans."

Yield-wise, Staples' RR seed beans averaged the same as his conventional soybeans in 1998. His 1999 yields were not yet in when this was written. Staples says his RR weed control costs, plus the tech fee, are about equal to the cost of conventional herbicides.

"But the tankmix we use on conventional beans sets them back four to five days," he adds.

For more information on RR yield performance, see "Roundup Ready Yields Lag," Mid-March Soybean Digest.