Consider whether the cover crop might compete with the cash crop for moisture, nutrients or sunlight before trying overseeding. Farmers rarely use fertilizer and pest control with cover crops because they usually do not realize a net economic return from those inputs. That leaves killing or controlling the cover crop as the only other management. Some cover crops, such as spring oats, are selected specifically because they will die during the winter in cold regions. Cover crops that survive the winter and live into the spring provide additional benefits such as erosion control or snow trapping, but need to be controlled or killed before planting a summer cash crop.
Herbicides can provide a simple killing method, but many farmers use other methods, such as tillage.
Some farmers prefer to suppress, rather than kill, the cover crop while the cash crop is getting established, then allow the cover crop to gradually continue growing as an understory ground cover. White Dutch clover, for example, provides erosion control and weed suppression, some nitrogen supplementation, and possible habitat for beneficial insects.