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Corn+Soybean Digest

Liberty Supplies Missing Weed Control Link

With the excellent weed control Daniel Higgins saw in his 11/2-acre field test of Liberty Link soybeans in 1997, there's a good chance he'll plant more of his acreage to the new varieties in '98.

"Before, we had no chemical to control lake weed (woolly bursage) in beans," says the Texas Panhandle grower. "But with the Liberty Link beans, we've seen excellent control. It really cleaned them up."

Higgins farms with his father, Doug, near Hart, TX. Their rotation includes about 350 acres of corn, 350 of cotton and 65 or more of soybeans.

"If we have cotton hailed out, we come back with additional bean acres," says Higgins. "They work well for us and produce about a 60-bu yield under furrow irrigation. We will have even more options with Liberty Link beans."

Liberty herbicide, from AgrEvo, is the trade name for glufosinate ammonium, which research shows is highly effective against a broad spectrum of weeds that threaten soybeans, corn and other crops. It's deadly on broadleaves such as velvetleaf, waterhemp, pigweed, ragweed, lambsquarters, cocklebur and woolly bursage. It also controls shattercane and some other grasses.

Liberty Link crops contain a gene making them resistant to the herbicide. Liberty Link corn hybrids have been available since 1995, and soybean varieties with the trait will be introduced by Asgrow Seed Co. this year. Expect to see Liberty Link cotton and sugar beets within the next few years.

Virtually every major seed company has worked in cooperation with AgrEvo to breed the gene into their corn and soybean lines.

"More than 95 seed companies have become Liberty Link partners with AgrEvo and already are offering more than 180 transgenic corn hybrids for purchase," says Jeff Springsteen, Liberty market manager.

Todd Taylor, agronomist for Midwest Seed Genetics, Peoria, IL, says Liberty's wide application window means it may be applied to soybeans from emergence all the way through bloom.

"Grass weeds should be hit when they are 4-6" tall," he says. "Broadleaves should be hit when they are 2-6" tall."

The application rate varies from 16 to 20 oz/acre for lower infestations and up to 28 oz for heavier infestations. Cost for a 20-28 oz application is $30-36 an acre, says Taylor.

Greta Schuster, a Texas Ag Experiment Station integrated pest management specialist who also helps monitor Liberty Link research, says that linking weed control to plant genetics looks like an effective way to control broadleaf weeds and grasses.

"Liberty Link did a good job of controlling weeds (in Higgins' soybeans)," she says.

Higgins usually plants Group IV beans in late May. They're prewatered, then are irrigated three more times starting just before first bloom.

"For weed control, we applied about 2 pints of Treflan in the past," he says. "It handled most weeds, but couldn't control the lake weed. A bad lake weed outbreak would reduce our yields by one-third, from 60 bushels to 40.

"But with the Liberty Link varieties, we shouldn't have that problem."

Some of his corn acres were planted to Liberty Link hybrids last year, too. Early weed control was good, but there still were a few morningglory problems later.

"In our case, we've had better luck with Liberty Link beans," says Higgins.

Liberty may be applied on corn from emergence up to the eight-leaf stage when corn is 24" tall. The application rate again is up to 28 oz/acre, and it may be applied twice each growing season.

Liberty can be tankmixed with almost any other postemergence herbicide, says Springsteen.

"Liberty does not restrict tillage practices, crop rotations or the use of other crop protection materials," he says. "It also has low volatility, is less prone to drift, and it minimizes concerns about groundwater quality because it is applied to plant foliage and not the soil."

Research indicates that the gene does not alter yield, disease resistance or other agronomic qualities of commercial seeds.

Brent Bean, extension agronomist in Amarillo, TX, believes Liberty hybrids can be an extra tool for growers. In Texas A&M University research, Liberty gave "reasonable" johnsongrass control, says Bean.

"Growers may still need to look at a preplant application of atrazine or Bicep, then come back with Liberty for weeds that get by that application. If it proves to be cost-effective, Liberty should be a good tool for us."

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