Underground Movement - 14

Think of the Cows

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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The soil-boosting diversity of cover-crop mixes can be alluring, but they can further complicate grazing opportunities. (DTN/Progressive Farmer photo by Mark Parker)

Cows are the gravy when it comes to making cover crops pay. However, herbicides used in your corn, soybean or wheat crop can make forage cover crops tricky to negotiate.

Nebraska Extension forage specialist Daren Redfearn urges growers to do some homework this spring to avoid label violations. At issue are plant-back restrictions of herbicides used during the crop-growing season. Herbicide labels dictate how long you must wait to plant certain rotational crops after a herbicide is applied.


Those restrictions are the result of an array of tests done by chemical companies to see how long a herbicide's residues could persist and affect a following crop. The tests cover common rotational crops like corn and soybeans. Cover crops aren't usually high on the companies' lists of priorities. As a result, many cover crops don't appear on herbicide plant-back restriction lists.

That doesn't mean you're off the hook, though, Redfearn noted. Instead, unlisted crops legally default to the longest possible plant-back restriction of 18 months.

According to the EPA, planting a cover crop in violation of a herbicide plant-back restriction is only illegal if you use the resulting vegetation for animal feed or grazing. If you violate a plant-back restriction for a cover crop used only for soil-health purposes and not feed, you're operating within the law, but you take on all liability for any crop failures, Redfearn added.


Spring herbicide applications pose some of the biggest problems for forage cover-croppers.

Preemergence herbicides used before corn and soybean crops often list the most restrictive plant-back rules on their labels, Redfearn said. Even the more common forage covers -- such as rye, wheat or oats -- often require a wait of four to four and a half months to plant after some preemergence herbicide mixes.

Postemergence herbicides for corn and soybeans tend to have shorter plant-back restrictions for forage crops ranging from zero days to three months.

For a detailed list of the plant-back restrictions for common forage crops following corn and soybean herbicides, see this University of Nebraska guide: http://bit.ly/… .


The soil-boosting diversity of cover-crop mixes can be alluring, but they can further complicate grazing opportunities, Redfearn said. These mixes often contain a wide range of sensitivities to herbicides, and at least one cover crop in the mix usually requires an 18-month plant-back restriction.

Fortunately, many of the cover crops most suited to livestock forage have been well-studied and are often listed on herbicide labels.

"A lot of the small grains used as cover crops have been used as annual forage crops for years," Redfearn noted. "We've just found a new use for them as cover crops, where livestock can provide the opportunity to produce some additional income and fund the establishment of the crops."

Covers like cereal rye, oats, barley and wheat are all excellent options for forage, as well as much easier to plant, graze and harvest legally, Redfearn said.

Emily Unglesbee can be reached at emily.unglesbee@dtn.com


Emily Unglesbee