There’s no question that cover crops have their benefits. After all, the right cover crop can improve nutrient availability and drainage while helping soils retain a healthy amount of moisture. It can also suppress weed growth, prevent erosion and soil compaction, and encourage beneficial insects and organisms to linger.
However, there are times when you’ll need to clear the way for your cash crop.
What do you do with a cover crop that has overstayed its welcome?
Consider using one of these four effective ways to terminate cover crops.
Winterkilling
Winterkilling, or natural termination, is the strategic use of cover crops that will naturally die off when hit by a hard freeze. With this method, there’s no need to take any direct action or worry about when to terminate. Winter does the work for you, leaving the crop residue in place on the field.
While this hands-off approach to termination may seem simple, choosing the right cover crop for your area is essential.
Winterkilling requires minimal time, labor, and resources when compared to other methods of terminating cover crops. That creates the potential for substantial cost savings.
However, it’s only suitable for certain climates, and you have far less control over the timing of the termination. Winterkilling also tends to provide both a shorter window of soil protection and a thinner layer of soil-conserving biomass.
Herbicides
Herbicides are chemical mixtures used to control undesirable vegetation. When using an herbicide program to terminate your cover crop, the plant is killed by an application of one or more herbicides at a specific time in its growth cycle. The optimal time varies by plant type, and the crop residue remains on the field unless you take action.
What’s the trick for an effective herbicide program?
As Purdue University explains, you’ll need to keep several factors in mind as you choose your herbicide and the time to apply it. Start by considering the cover crop species and its growth stage. Then, take into account the presence of any weed species. You’ll also need to consider the production crop that you’re planting. Finally, you’ll need to think about the weather on the day of application.
Using herbicides gives you more control over the timetable of your cover crop termination, but it’s imperative that you’re always thinking ahead when you use them. After all, the product that you apply today could limit your options for planting in that field tomorrow. Residues from certain herbicides can linger in the soil for weeks after an application. To avoid problems, you’ll want to terminate with an herbicide that will take out the cover crop without negatively impacting the cash crop that you’re planting next.
Mowing
Mowing is a quick way to mechanically terminate a cover crop. The blade cuts through the plant’s stem, leaving the root in place and the residue on the field.
The nature of the cut depends on the mower used.
- Sickle-bar mowers cut close to the surface
- Rotary mowers cut higher
- Flail mowers use double-edged blades that produce a finer residue that is more evenly distributed across the field’s surface and decomposes faster.
Mowing is popular and speedy, but as The Ohio State University indicates, its results can be unpredictable. Cover crop regrowth can be a problem, especially when it creates competition with cash crops for limited resources.
The chopped residues left behind by the mower’s blades also decompose more quickly than the intact residues left behind by other methods. As a result, they’re less effective than mulch.
Roller Crimping
Rolling crimping offers another form of mechanical termination. Here, hollow steel drums crush plants before blunt blades on the cylinder crush or crimp, their stems. As Sustainable Agriculture Research & Education reports, you’ll generally act when cover crops are in a reproductive stage. However, there are exceptions.
Some, like sorghum, produce better results if you wait to terminate until they’re mature. When rolling-crimping is done at the right time, the residue remains rooted in place. It forms a thick, unidirectional surface mulch that decomposes more slowly than mulches that have been chopped up by mowers.
Rolling-crimping creates an ideal environment for no-till planting because it creates a thick biomass that shields the soil and prevents weed growth. As Penn State Extension says, the keys to success with this method lie in crop selection and timing.
For starters, you’ll want to select an annual variety. In addition, you’ll want to check that the cover crop you’re considering responds well to roller-crimping. Then, you’ll want to weigh the matter of timing carefully. Regrowth can be an issue if you don’t.
What if you have a mix of cover crops in one field? It’s generally best to use the latest-maturing species as your guide. Used independently, rolling crimping is a useful approach for organic operations. When desired, it can also be combined with herbicides.
Offsetting the Costs of Cover Crop Termination
When you’re searching for financial or technical assistance with resource management, The U.S. Department of Agriculture’s Natural Resources Conservation Service can be a useful ally.
If you’re just getting started with cover crops, check out the Environmental Quality Incentives Program. With EQIP, participants can receive financial assistance for taking steps like implementing a cover crop program that improves agricultural operations while simultaneously leading to healthier soil and cleaner water and air. Meanwhile, those who would like financial support for an existing cover crop program might find it with the Conservation Stewardship Program. Depending on your operation’s location, you may also find support for your efforts from state or local programs.
