February 4, 2025

By Darlene Florence
Depending on your location, the weather either looks like winter is going to hang on for a while longer or spring is just around the corner. Did that winter weather terminate your cover crop? Or will you have to take matters into your own hands?
Ideally, you considered termination options before the cover crop was planted. The most straightforward termination option is to plant a species that is almost always killed by the Midwestern winter. Oats and oilseed radish are two of the most common species. It’s unlikely that this winter will be as mild as last year, where some stands survived into spring.
The most common cover crop termination method, after winter kill, is herbicide application. Although the specific product and timing will vary with your cover crop species, cash crop species, weed pressures, soil type and the weather, there are a few general guidelines. The primary consideration is timing. Plants need to be actively growing for herbicides to work well. And all herbicide applications should be made in accordance with the label restrictions. If there are additional weed species of concern, consult your state’s weed-control guide.
The second consideration is the cover crop species. Crimson clover and Austrian winter pea are two commonly planted legumes that rarely winter kill, but they also rarely cause issues, as they generally have less biomass than their grass companion and are readily terminated with the same herbicide program that will kill the grass species. For grass cereal rye, it is recommended to terminate either when it is 6 to 12 inches tall or two weeks before the expected planting date, whichever comes first.
Additional considerations
When field work is delayed due to a wet spring, spraying either a few days before planting or a few days after can prevent tall cereal rye from forming a wet mat on the soil surface. It can attract pests and be tough for planting. If your spring crop is corn, include nitrogen in your starter fertilizer. If you’ve been noticing nitrogen deficiency-type symptoms with sufficient nitrogen applied, consider adding sulfur to the starter.
A mechanical option of termination may become of interest. For cereal rye, termination with roller-crimping is most effective when rye is flowering and pollination has begun. Most years, this is later than when you might prefer to get your soybeans planted. Thankfully, soybeans can be planted into standing cereal rye, and they can tolerate crimping up to 4 inches tall. In some situations, tillage also can be used to terminate the cover crop.
Florence is a state agronomist with the Natural Resources Conservation Service. She writes on behalf of the Indiana Conservation Partnership.
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