PEEKING OUT. Oilseed radishes emerge 4 days after seeding during a Michigan State University Extension field experiment last year covering rotation restrictions for cover crops after cash crops. Researchers are tracking the effects of soil-applied herbicides on cover crops, including radishes, clover and cereal rye.

Don’t Let Lingering Herbicides Hamper Cover Crop Success

The wrong herbicide used at the wrong time, or impacted by the wrong environmental conditions, can limit — or even destroy — a costly cover crop seeding.

Sometimes cover crops fail. This is especially true as no-tillers navigate the trial-and-error years of determining what species, seeding methods and timings work in their region and on their farm.

In cases where cover crops fail, farmers have to look at all potential causes, including herbicide carryover.

“I can’t say how often cover crop failures are due to herbicide carryover,” says William Curran, Penn State University weed scientist. “But there have been several instances where we’ve seen failures, where we’ve back tracked and, low and behold, their herbicide program was likely to blame.”

In some cases, the cover crops simply don’t come up, or come up patchy. In more obvious cases, Curran says, you can see where there was sprayer overlap or where compacted soils in point rows or other areas of heavy traffic made covers more susceptible.

Or, in Streator, Ill., no-tiller Larry Tombaugh’s case, the cover crop came up strong and suddenly failed.

“I seeded annual ryegrass one year. It came up just perfect, but when it reached 6-8 inches tall, it hit a layer of what must have been herbicide in the ground and that fried it all,” he recalls. He tracked the failure to his use of Lightening herbicide in his corn, a product that is marketed to provide season-long residual.

This is an increasing cause for concern as producers look to manage herbicide-resistant weeds or prevent their development by rotating chemistries and adding residual herbicides back into their management programs.

“With the increased use of…

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Martha mintz new

Martha Mintz

Since 2011, Martha has authored the highly popular “What I’ve Learned About No-Till” series that has appeared in every issue of No-Till Farmer since August of 2002.

Growing up on a cattle ranch in southeastern Montana, Martha is a talented ag writer and photographer who lives with her family in Billings, Montana.

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