There are several ways to kill cover crop plantings, each suited to the crop and the region. Seed guidance can help with timing, but method and local conditions matter. Ending a cover too late or too early can undercut the soil biomass growers have worked to build.
Plan termination around farm goals. Consider the following crop, available equipment, and the broader production system. Much of this planning begins at seeding time.
Context drives timing. In dry soils, it is often best to terminate up to two weeks before establishing the next crop. Otherwise, farmers can plant into the standing cover and terminate after emergence. Where pests are a concern, aim for three to four weeks before planting.
Always end the cover before it sets seed to prevent unwanted volunteers and ease management.
Termination methods to kill cover crop plantings
The method should fit the farm and still build soil biomass. Each approach can work when well timed.
Mowing
Mowing is quick and leaves roots in place to support biomass. Cut as close to the soil surface as possible. Multi-blade mowers help chop residue for faster breakdown.
Barley, cereal rye, and vetch respond well to mowing when done at flowering but before seed formation. Hand planting after mowing can be easier than drill seeding because roots lay in multiple directions.
Natural kill
In cold climates, winter freezes can terminate certain covers. This approach is not reliable where freezes are infrequent. Planting must be timed so the cover reaches flowering, typically from mid to late summer seeding.
Oilseed radish, sorghum, buckwheat, and field peas are good candidates for natural winterkill. Oats and rye often survive and need another method. If they persist, they can flower and reseed, complicating control.
In spring, planting can proceed into the winter-killed mulch. Be aware that a full season without living roots can increase erosion and deplete soil health.
Tilling
With tillage equipment designed for vegetated fields, farmers can terminate covers effectively. Tillage removes roots, which can reduce soil biomass. If using this method, amend as needed and plant the next crop immediately.
Tillage suits persistent covers like winter rye that continue growing unless roots are disrupted. In warmer regions, it can be a practical alternative to winterkill.
Roller crimping
Roller crimping flattens the cover onto the soil surface. The crimper’s blades crimp stems to speed decomposition. Use at the reproductive stage, just as flowers open, to limit regrowth and build biomass.
This method is best for annual covers. Perennial and biennial roots may survive. It requires a tractor-mounted roller crimper, which may be impractical for small acreages.
Grazing
Intensive grazing can terminate covers when the plants also serve as quality forage for on-farm livestock. Oats, peas, cereal rye, oats, and barley can provide good feed. For this approach, seed at roughly 150 percent to 200 percent of standard density.
Dairy cows perform best on early-stage forage, so winter covers may be better suited to beef cattle. It is less suitable for those establishing native grasses, which often regrow due to deep root systems.
Graze when fields are dry. Wet conditions can harm soil structure and biomass. In cloudy, cool weather, nitrate levels can become risky for cattle. For effective termination, concentrate the herd in a small area for a short time on a sunny, dry day.
