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Managing risk when using herbicides and cover crops in corn and soybean

When adding cover crops into a corn and soybean production system, one challenge is herbicides with residual activity may interfere with the establishment and growth of cover crops.

However, residual herbicides are a key weed management tool, especially for managing herbicide-resistant weeds and combating waterhemp and other weeds with extended emergence patterns.

By paying careful attention to herbicide labels, cover crop selection, research results and the timing of herbicide application and seeding, you can help increase your odds of successfully incorporating cover crops into corn and soybean systems.

seeding cover crops
More farmers are seeding cover crops into corn and soybean. Annual rye, radish, turnips and hairy vetch were broadcast-seeded into this field around the V7 stage of corn.

Grazing or harvesting cover crops for feed or forage

Any rotational or plant-back restrictions listed on the label must be followed if you graze or harvest cover crops for feed or forage. The herbicide label is a legal document and instructions must be followed to avoid violating federal law.

Many herbicides have rotational restrictions, which specify the length of time until a crop can be planted in the same field after application.

Rotational restrictions are placed on herbicide labels to protect the food chain from pesticide residues and/or the succeeding crop from injury. If a rotational restriction isn’t listed for a particular cover crop, the rotational restriction listed for “other crops” must be followed.

More about rotational restrictions of corn and soybean herbicides:

As always, refer to the product label for the most up-to-date information.

There’s more flexibility if the cover crop won’t be grazed or harvested. The farmer 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.

Rotational restrictions listed on the label must be followed if the cover crop will be grazed or harvested. If the cover crop will not be grazed or harvested, a farmer has more flexibility. In this case, however, the farmer assumes all risk of injury to the cover crop if label restrictions are not followed.

If you won’t graze or harvest the cover crop

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.

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Lizabeth Stahl, Extension educator

Acknowledgements

Document reviewed by Jeff Gunsolus, Extension agronomist and Jill Sackett-Eberhart, former Extension educator.

Photo credit: Lizabeth Stahl.

Product names are listed for reader convenience. Inclusion isn’t intended as an endorsement, while absence doesn’t imply disapproval.

Reviewed in 2018

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