Planting that first field of genetically engineered Roundup-tolerant soybeans in 1996 could be a memorable event for many Arkansas farmers. And based on the results of trials by University of Arkansas weed scientists Drs. Dick Oliver and Ford Baldwin, it should be a pleasant memory.
Oliver, an agronomy professor in the Dale Bumpers College of Agricultural, Food and Life Sciences, conducts soybean weed control research for the Arkansas Agricultural Experiment Station. Baldwin is a Cooperative Extension Service weed scientist.
The Roundup-tolerant varieties approved for sale by Asgrow and Hartz seed compames 2 in 1996 represent the first significant fruits of genetic engineering to impact soybean producers. A gene was added to selected soybean varieties that makes them virtually immune to damage by Roundup herbicide, which will kill most other plants.
Oliver and Baldwin have conducted field trials funded in part by the Arkansas Soybean Promotion Board to provide an objective basis for Cooperative Extension Service recommendations for the use of this new technology.
A gene was added to selected soybean varieties that makes them virtually immune to damage by Roundup herbicide, which will kill most other plants.
"It works great," Baldwin said recently.
If Roundup-tolerant seed is sold for a premium of $6.50 over regular seed, as forecast, and if the price of Roundup stays at about $4 a pint, this system will provide excellent soybean weed control for about $15 per acre, he said.
The recommended treatment level under most conditions is two applications, 1 pint each, of Roundup at 14 and 21 days after emergence, Baldwin said.
Baldwin and Oliver reported that, based on test results, Roundup offers the potentiai for broader spectrum weed control; solving resistant weed problems; better control of tough weeds such as sicklepod, Palmer amaranth, red rice and rhizome johnsongrass; and the ability to control larger weeds than with the currently labeled herbicides.
They cited the long-term benefit of having new chemistry to rotate with existing herbicides to reduce the chances of weeds developing herbicide resistance. Yet another benefit is that the Roundup Ready system will work well with minimum-till or no-till systems, Baldwin said.
Despite its benefits, the system is not foolproof, the weed scientists cautioned.
The farmer must be sure the Rounduptolerant variety planted is well adapted to the field conditions. Roundup drift onto other plants or accidental spraying on normal soybeans could be a problem.
Applications must be timed according to weed size and environmental conditions for good herbicide activity. Overuse will allow weed species shifts in a field.
All things considered, the Roundup Ready L system is clearly the next major advance in soybean weed control technology, Oliver and Baldwin said.
The Roundup Ready system is clearly the next major advance in soybean weed control technology.
Other major advances over the past four decades were Treflan for pigweed and grass control in the early 1960s, Basagran for cocklebur and prickly sida control in the midseventies, and Scepter and Canopy for broad spectrum broadleaf weed control in the mid-eighties.
Research by Oliver and Baldwin in the 1980s provided the basis for the first state Extension Service recommendations for applying herbicides at a rate lower than that recommended on the herbicide label. Reduced rate applications require careful observation of weed species in the field and careful timing of the applications.
Baldwin and Oliver said test results indi cate that reduced rate recommendations can be developed for the use of Roundup on Roundup-tolerant varieties based on continued study of the biology and competitiveness of weeds in Arkansas soybean fields.
