Corn+Soybean Digest

Farmers, Researchers Rate Roundup Ready Corn

Farmers who planted the newly introduced Roundup Ready (RR) corn last spring were expecting darn-near perfect weed control. And that's pretty much what they got.

"Our weed control with the Roundup Ready corn was about what we had hoped for, and certainly the best of any of our fields," reports Jeff Ward, Mankato, MN.

"Often, you see small grass in corn, but with the Roundup Ultra we had little or no grass," Ward notes. "The Roundup Ready program is simple and effective, and it saves spraying time."

Ward planted 250 acres of Dekalb's RR corn split between two hybrids. "The yields were solid, although not our very best," he says. "We had one conventional hybrid that was slightly higher. However, DK512RR averaged 182.2 bu per acre on 118 acres."

Ward plans to increase his RR corn acreage this spring, but won't go overboard. "Although we like what we have seen of the program, we have only one year's experience," he points out. "There also is the extra cost of seed to consider."

The added cost includes an $18/bag technology fee.

Dairyman Jerry Hollmann, Leigh, NE, wanted primarily to nail sandbur when he planted RR corn last spring. That weed has been getting worse in his continuous corn. He applied Guardsman-Frontier behind the planter and followed with 32 oz/acre of Roundup Ultra.

"Our soil is rich from manure - a factor that favors weeds - plus we had unusually heavy rainfall last summer," says Hollmann. "Yet I would give the Roundup an A-minus or B-plus on performance. It provided very good, if not total, weed control.

"We had 14 acres of conventional corn next to the Roundup Ready, and it was very weedy."

At Spencer, IA, Bob Barringer saved a chunk on herbicide costs with his 70 acres of RR corn.

"The field did not have overly heavy weed pressure," he reports. "We made one application of Roundup when corn was at the five-leaf stage. Weed control was very good, and the cost was only $17.66/acre."

He spent $43.68/acre on herbicides for his conventional corn.

"But the biggest thing with Roundup is that it really kills weeds," Barringer declares.

Bob Barkei, a farmer and Dekalb seed dealer at Steward, IL, planted 350 acres of RR corn spread among five hybrids.

"We applied Harness Xtra behind the planter and sprayed the Roundup Ultra at a quart rate when corn was 18" tall," says Barkei. "Our main target was hemp dogbane. And at harvest you could count the hemp dogbane plants on one hand. Those fields were clean."

Barkei, who has a yield monitor, reports that the RR hybrids yielded the same as their conventional counterparts.

"Because of the added cost of Roundup Ready corn, you need to target it for those fields with the toughest weeds, such as hemp dogbane, woolly cupgrass, wirestem muhly and shattercane," says Barkei. "We have not had corn herbicides that are really effective on those weeds."

Western Illinois University agronomist Gordon Roskamp conducted two 1998 trials with RR corn. In total, he compared 31 treatments that included Roundup alone, Roundup in combination with other herbicides and non-Roundup combinations. He also varied rates.

Roskamp rated weed control on eight weeds: giant foxtail, ivyleaf morningglory, common cocklebur, venice mallow, velvetleaf, prickly sida, common lambsquarters and redroot pigweed.

"In general, we had a few weeds come after our last application of Roundup Ultra, but they didn't seem to affect yield," Roskamp summarizes. "We did see a Roundup weakness on ivyleaf morningglory."

Roskamp measured yield for each herbicide treatment. The treatments that produced two of the best yields were: 1.67 pints Harness pre-emergence followed by 1.5 pints Roundup Ultra at 3-6" corn height, and 1.5 pints Roundup Ultra at both early and late postemergence.

To get a copy of Roskamp's report, phone him at 309-298-1569, or send him an email ([email protected]).

A Monsanto survey of 1998 RR corn users indicates that satisfaction was high. Ninety-six percent said they were very/somewhat satisfied. Just over 70% rated Roundup Ultra's control of specific weeds as much better or somewhat better than traditional herbicide programs. Eighty-three percent were very satisfied with crop safety.

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