If you’re one of the many farmers who planted winter cover crops this year to help your summer crops, it’s time to terminate them, according to Kansas State University specialists.

In the Feb. 17 Agronomy eUpdate, K-State weed and soil specialists remind farmers that some cover crop species, like oilseed radish or fall-planted oats, were likely killed by winter freezes. But other covers will need to be terminated by chemical or mechanical methods in the spring. And the Natural Resources Conservation Service has guidelines for that termination timing in order for farmers to stay in program compliance.

Mechanical methods

Considering the limited availability for many chemical herbicides this spring, farmers may be more likely to choose mechanical termination to save herbicide use for in-crop applications on their corn and soybeans, say Peter Tomlinson, environmental quality specialist, and DeAnn Presley, soil management specialist. Some mechanical methods include:

Roller or roller-crimper. This is effective for monoculture plantings of winter cereal grains like cereal rye. For a successful kill, use a roller-crimper at milk or dough stage on winter cereals. For legumes, use at full bloom stage.

Tillage. Tillage is an effective option in some cropping systems, but some species of clovers may not be effectively killed — and multiple passes cancel out any soil health or conservation benefits.

Mowing. This is best-suited for smaller acreages.

Herbicides

Herbicides are an effective cover crop termination tool, according to Sarah Lancaster, weed management specialist and Anita Dille, weed ecologist. Farmers need to consider:

Cover crop species. Match the herbicide to the species in your cover crop blend. Selective herbicides might be best for single-species plantings, but nonselective herbicides such as glyphosate, glufosinate or paraquat are recommended for mixed-species plantings.

Growth stage. In general, as in any plant, herbicides are more effective on younger, less mature plants. They lose effectiveness once the plant has entered reproductive development.

Residuals. Residual herbicides like Prefix or Authority Maxx can be used, and research shows including them can control waterhemp and protect soybean yields better than chemical termination without residuals. Be sure, though, to consider potential injury to the following crop.

To learn more, visit bit.ly/ccterm.

K-State Research and Extension contributed to this article.