Doug Buhler is as concerned about weeds as any no-tiller. The weed specialist from Ames, Iowa, is apprehensive about the increased resistance to herbicides that weeds are showing in an ever-increasing frequency.

“I think it’s alarming,” says the U.S. Department of Agriculture researcher. “It’s a serious issue. Weed populations in the fields really are a function of the production practices we use. Weeds respond very rapidly to tillage, they respond to the herbicides we use and they respond to rotations.”

Many Weed Species

Buhler says most no-till fields have 20 or 30 weed species and because of their ability to invade crops and substantially decrease yield, a more comprehensive weed management program is needed.

“Go back to the 1940s when 2,4-D came along and was very effective on many broadleaf species, but 2,4-D didn’t kill grasses,” he says. “Then we shifted to weeds that can tolerate tillage and the herbicides we were using. Then we moved into the weeds that were coming along like velvetleaf and cocklebur, large-seeded weeds that came up from deeper in the soil and are more herbicide tolerant.”

The next era brought no-tillage to the forefront and weed species with an ability to survive in undisturbed habitats, such as winter annuals and small-seeded summer annuals, that lay on the surface and give no-tillers fits. Buhler says waterhemp is an example of a weed that became resistant to certain herbicides in a no-till situation.

“Waterhemp is very well-adapted to no-tillage,” he says. “It doesn’t come up until…