With 20 years of experience raising seed soybeans, Michael McCallie knows the value of herbicide application timing.

McCallie, of Almyra, AR, grows just over 1,000 acres of Roundup Ready soybeans.

"We raise all seed beans, and we're required to use Roundup on them for purity reasons," he says.

To get early season weed control and improve application timing, McCallie also uses a soil-applied, residual herbicide on half of those acres. He incorporates Tri-Scept at planting, then later applies 24 oz of Roundup per acre.

"The fields that we put the preplant herbicide on stay cleaner longer, on average," he says. "A soil-applied herbicide holds the competition down, and then you come back and clean them up with Roundup. It gives the beans a chance to get a good start."

Crop consultant Roger Carter also recommends that growers who plant Roundup Ready beans use a broad-spectrum soil-applied herbicide.

"Reducing competition early allows the crop to grow and mature more rapidly," says Carter, president of Agricultural Management Services, Clayton, LA.

Weather and weed species are two of the most important variables to consider in a Roundup Ready program.

"We're not always guaranteed excellent weather, and Roundup relies on adequate moisture," Carter says.

Morningglory can be particularly troublesome if it's allowed to get too big before the herbicide application. For McCallie, soil-applied herbicides provide the needed early season and residual control.

"Roundup performs well on morningglories if you get it on early enough," adds McCallie. "But if you wait, they get longer runners, and they're much harder to control."

He typically plants beans from maturity Groups V, VI and VII. Except for 250 acres of dryland, no-till beans, he uses conventional tillage and row irrigation.

"On the early beans in particular, I feel more comfortable with the pre-emergence application," he says. "It works for me."