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Corn+Soybean Digest

Easy Weed Control In Corn-Bean Strips: Iowans plant Roundup Ready corn and beans

While northeastern Iowa's colorful contour strips and gently flowing ridges make scenic pictures, postemergence herbicide spraying can be a nightmare.

Not only are crops planted right next to each other, the strips turn at various angles to follow land contours. In addition to timing, there's boom overlap and the ever-present threat of crop damage - even on calm summer days.

Veteran no-tillers Craig and Lee Embretson of Farmersburg say they've solved these problems by planting Roundup Ready corn alongside Roundup Ready soybeans.

"Where we have both Roundup Ready corn and Roundup Ready beans we can spray Roundup Ultra right along the edges of the contours without having to worry about damaging either crop," Craig Embretson explains. "It really works well."

In 1998, they planted 250 acres of Roundup Ready corn, about 40% of their total corn acres. They practice all no-till in a corn-soybean rotation on 1,200 acres spread across seven farms. Their 20 fields, ranging in size from 5 to 50 acres, are scattered over 16 miles, so anything that saves time helps the bottom line.

With more than 10 years of experience in no-till soybeans, they turned to no-till corn only three years ago, motivated by the 1995 Freedom to Farm law.

"About 90% of the land we farm is erodible or highly erodible, so it makes good sense to go all no-till and protect the soil," Embretson notes.

He says Roundup Ready corn is a boon to no-till farming.

"With Roundup Ready corn and Roundup Ready beans in a total no-till program, you're going to have a lot more confidence in killing perennial weeds," he states. "It simplifies everything."

Their program starts in the spring with a burndown treatment of all no-till acres. They use Roundup Ultra and vary rates from 1 pt to 1 qt/acre, depending on weed pressure and weed types.

"For example, on dandelions and quack we use a full quart," Embretson notes.

Burndown timing is carefully planned based on weed size.

"We watch weeds and try to hit them when they are about an inch or less. Burndown in a dry year helps yields by getting them early before they steal moisture and compete with crops."

Corn is planted in 30" rows starting around April 25, depending on soil temperature. Beans are planted in 15" rows, and the goal is to get both crops in by May 25.

For his Roundup Ready corn, Embretson tried two approaches. He treated 50 acres directly with Roundup Ultra at the 32-oz rate just before canopy.

He treated another 200 acres with a postemergence tankmix of Roundup Ultra (20 oz) and Harness Extra (1.5 qts) when corn was at the two- to four-leaf stage.

"Both programs worked well," he says.

This year he plans to evaluate both approaches again, and since Roundup Ultra can be applied twice on corn in '99, he plans to make two 24-oz applications - the first at the two- to four-leaf stage; the second, right before canopy.

"If it's a dry spring, we'll go a little earlier with the second trip," he adds.

For soybeans, burndown and planting are followed with a Roundup Ultra treatment when weeds are 2-4" tall. Rates vary by field from 18 oz to 1 qt. They add 1 lb/acre of ammonium sulfate to the tank to soften the hard water common to the area and help the Roundup perform better.

"Most of our fields were treated with the 20-oz rate and only one of 20 soybean fields had to be treated again," he reports.

They also like to use Roundup Ultra to trim the edges of no-till fields.

"While we see the benefits of soil conservation, we also see grasses along the edges and borders of the field creep in a foot or so every year," he says. "So we run the sprayer right along the border to trim it back. It really cleans up those edges."

Embretson believes Roundup Ready corn is the last piece of his no-till puzzle to fall into place.

"With no-till we're saving at least two trips to every field," he points out. "And with Roundup on both corn and beans, we have the confidence we need to stop perennial weeds."

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