Strategic weed management is critical for cover crop success – Agweek

CAPUTA, S.D. — Managing weeds in cover crops is tricky.

Anthony Bly, soils field specialist for SDSU Extension, says that the first thing producers need to be concerned with is herbicides that were applied to the cash crop previously.

“Of course, there are label instructions, and you need to read those labels and look at those restrictions, especially if grazing is in your plan,” Bly said. “We do not want these active ingredients getting in the food chain.”

The second thing to keep in mind is the time of year your cover crops are being planted.

“Just designing what cover crops to plant based on cool or warm season and that planting date is the second thing you should probably look at,” Bly said.

There are two main ways that producers plant their cover crops.

“Many producers have done numerous things,” Bly said. “They have planted their cover crops right after small grain harvest, or they have waited and let the weeds grow a little bit and then treated the weeds with a burn-down herbicide and planted new cover crops after that.”

But Bly says the key to managing weeds is understanding which ones are causing your problems.

“You’ve got to focus on those problem weeds and design your system around those,” he said. “Don’t design the herbicide system to fit the cover crop system, you’ve still got to control weeds in your planned cash crops, so you need to focus on that.

There are no specific types of weeds affecting the cover crops in South Dakota.

“We see all kinds of weeds. I mean we’ve got perennials, Canada thistle, maybe some quackgrass in places,” Bly said. “Of course we’ve got annuals. In the southeast, it’s water hemp. In the middle part of the state, it’s probably kochia. There’s Canada thistle in both locations. That’s why it’s very important for each producer to look at what’s there.”

Bly advises producers to do their research.

“I would study those residual herbicides that you applied. I would get ahold of some publications and kind of compare and look at the effect of those herbicides on cover crops and I would look at the label, especially if you intend to graze those cover crops,” he said.

It’s important to get on top of weed control so you don’t see more weeds later on.

“Farmers don’t want to produce weed seeds for the future. Keeping that weed seed bank in the soil lower is really important for fighting them in the future,” Bly said. “There is always going to be weeds, but if you keep that seed bank as low as possible, it’s just easier to control.”