Evaluate for winter kill
If the above ground cover crop is brown and near the soil surface no green plant material is present then your cover crop winter-killed. Cover crops such as tillage radishes and oats typically winter kill and then no additional spring management is needed. Other cover crops, such as winter or cereal rye, winter wheat, triticale, and barley, consistently over-winters in Iowa. In late March, double check plant stems near soil surface to see if the plant has survived.
Herbicides, tillage or a combination of the two can be used to effectively manage cover crops in the spring. Keep in mind any tillage will reduce the effectiveness of the cover crop residue to protect against erosion and suppress weeds.
Herbicide: For successful herbicide termination, make sure the plant has “greened-up” and has enough living surface area for the herbicide to work. Experienced farmers suggest spraying during the middle of the day and, if possible, spray when air temperature is at least 45 or 50F. Unless you have experience, separate nitrogen application from a “burndown” herbicide application.
Tillage: Terminating cover crops with tillage can be effective, but may take more than one tillage pass. Wet periods can delay tillage to terminate cover crops and wet conditions following tillage can allow cover crop plants to survive tillage operations.
Consider nitrogen needs
Cover crops effectively sequester nitrogen and as the plant residue breaks down it will release its nutrients, making them available for the crop later in the season when they need them the most. However, there is the potential for lower available nitrogen early in the growing season, especially following an overwintering grass cover crop like cereal rye. To protect yield, farmers growing corn after a cereal rye cover crop may want to apply 30-50 lbs of nitrogen at or near corn planting. This is not additional nitrogen, but within the farmer’s total fertilizer program.
Start planning now for cover crop needs
Determine what cover crop(s) work with your current or planned crop protection program. Some residual herbicides have carryover restrictions for certain species of cover crops. Consult with an agronomist and/or cover crop seed representative to look at specific management system with integration of cover crops.
(Source – http://www.newtondailynews.com/2015/04/06/ag-secretary-shares-tips-for-managing-cover-crops/as5imnz/)