Using herbicides and cover crops in corn and soybean

rows of young rye plants growing in tall corn rows

Producers looking to plant cover crops in their corn and soybean fields often ask what to do about their herbicide program. There’s not a one-size-fits-all answer to this question and, unfortunately, there are many unknowns.

However, you can help increase your odds of successfully incorporating cover crops into a corn and soybean system by paying careful attention to:

  • Herbicide labels.

  • Cover crop selection.

  • Research results.

  • The timing of herbicide application and seeding.

One challenge when adding cover crops into a corn and soybean production system is herbicides with residual activity may interfere with the establishment and growth of cover crops. Residual herbicides, however, are a key weed management tool, especially for managing herbicide-resistant weeds and combating weeds with extended emergence patterns like waterhemp. 

Grazing or harvesting the cover crop for feed or forage

If you plan to graze or harvest the cover crop for feed and forage, then you must follow any rotational or plant-back restrictions listed on the label. The herbicide label is a legal document and instructions must be followed to avoid violating federal law.

There’s more flexibility if the cover crop will not be grazed or harvested. The producer assumes all risk of injury to the cover crop if label restrictions aren’t followed, but there would be no legal issue of trying to sell an adulterated crop because the cover crop isn’t entering the food or feed chain.

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For cover crops that won’t be grazed or harvested

If the cover crop won’t be grazed or harvested and the cover crop isn’t listed on the herbicide label, consider the following six criteria to help reduce the risk of crop injury while increasing the potential for successful cover crop establishment.

Key criteria

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Lizabeth Stahl, Extension educator; Jeff Gunsolus, Extension weed scientist and Jill Sackett-Eberhart, former Extension educator

Reviewed in 2018

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