"ROUNDUP READY"

"ROUNDUP READY" SOYBEANS MAY MEAN CHEAPER WEED CONTROL

Contact: Dr. John Sij or Dr. Jim Stansel (409 752-3045)

For photos: Dr. Thomas R. Hargrove (409 762-2763)

by Tom Hargrove

BEAUMONT—"Roundup Ready" soybeans—varieties carrying non-soybean genes that make them resistant to the herbicide Roundup—may soon allow cheaper and more effective control of yield-robbing weeds, says Dr. John Sij, agronomist at the Agricultural Research and Extension Center at Beaumont.

"Such 'transgenic' soybeans may be the most important agricultural advance since hybrid corn," says Sij, who specializes in alternative crops for the Texas Rice Belt. Commercial breeders made conventional varieties "Roundup Ready" through biotechnology—they transferred genes that confer resistance to the herbicide from a soil microbe into the soybeans.

Transgenic soybeans reduce the farmer's risk and expenses by allowing weed control after the crop is established, Sij says.

"Roundup, or glyphosate, will kill conventional soybean varieties, so farmers can now use it only before planting the crop, or with a hooded sprayer," he explains. "If the crop is protected through a traditional pre-emergence herbicide program, and fails because of hail, floods, or drought, the farmer must start over, paying twice for herbicide as well as new seeds."

But a farmer can allow weeds to come up with transgenic soybeans. Once the crop is safely established, the farmer can kill the weeds with Roundup. The resistance genes protect the soybeans.

Sij is comparing 20 Roundup Ready soybean varieties in field trials at Beaumont, using only Roundup for weed control. The varieties range from early to late in maturity, and were developed by five companies: Hornbeck, DeKalb, AgriPro, Hartz, and Delta & Pineland.

Transgenic varieties that resist the herbicide sulfonylurea may open other doors to broader weed management strategies.

"Roundup controls grasses well, but not yellow nutsedge and broadleaf weeds such as morning glory, sicklepod, and red stem," Sij says. So the agronomist is testing management systems that involve both a Roundup Ready and a transgenic STS or "sulfonylurea tolerant soybean." Sulfonylurea controls sedges and some broadleaves better than Roundup.

"Farmers may rotate transgenic Roundup Ready and STS soybeans on alternate years," Sij says. "The herbicides can complement one another."

Some farmers think the transgenic soybeans have lower yield potential than conventional varieties. But if a "yield drag" exists, it won't last long, Sij says. Commercial breeders will soon raise the transgenics' productivity.

"Besides, Roundup can control weeds at about half the cost of other management practices," Sij points out, "so farmers using Roundup Ready soybeans can absorb up to a 5-bushel per acre yield drag and still come out ahead."

But extensive use of transgenics could result in herbicide-resistant weeds. "It's like the development of pest-resistant insects," Sij says. "If herbicides are sprayed year after year, selection pressure might shift the weed population to weeds that tolerate the herbicide better."

Soybeans were almost non-existent in Texas until the mid-1950s, and production has been erratic ever since.

"Soybean production often depends on cotton in the Texas Panhandle," Sij says. "When the crop is hailed out, it's often too late to replant cotton—but soybeans will still make a crop."

Soybean production in Texas peaked at about 1 million acres in the early 1980s, then dropped to around 200,000 acres. About 420,000 acres are grown today, and production is increasing.