Perhaps you’ve read about how beneficial cover crops can be for building your vegetable garden soil in the off season, and planted one over the summer. Now it’s time to get the fall garden going, and you’re wondering what to do with the cover crop. You’re not alone! Learning the best methods of cover crop termination for your garden will help make sure you get all the benefits and minimize the problems associated with less than ideal cover crop endings.
Methods of Cover Crop Termination
There are five main methods of bringing a cover crop to the end that can be used at the home garden scale:
- Mowing or Weed-whacking
- Tilling
- Smothering or Tarping
- Crimping
- Winter Killing
It’s important to match the termination method to the type of crop and to the stage of plant growth. It’s also possible to combine some of the methods for even more effectiveness. Read on for more information!
Mowing or Weed-whacking
This method can be very efficient and will be most effective after the cover crop has moved into the reproductive, or flowering phase. Otherwise, the crop may just keep growing. Mowing will leave the crop biomass on the soil surface. It will break down (eventually), but if you want to speed up the process, chop it up into very small pieces. You can leave the residue on the soil surface to block weeds and prevent erosion. Or turn it into the soil several weeks before planting your next crop. Be aware that even mowing will be difficult in crops that develop woody stems as they age. Sun hemp is an example of a warm season cover crop that becomes woody over time. It’s much easier to terminate the crop before that happens.
Tilling
If you have a large in-ground garden you can till your crop directly into the soil. This method is generally easier and more effective during the vegetative, or growing, phase before you see flowers developing. If you wait too long, small hand tillers will have a very hard time churning through all the vegetation, which may become wrapped around the tines. Mowing prior to tilling can help. You may need to make several passes. Be sure to do this several weeks prior to your next planting.
Smothering or Tarping
If you have small beds and plenty of time, simply covering the crop with opaque sheeting will effectively kill a cover crop. Smothering works by keeping sunlight from the crop, starving it of the ability to feed itself. Don’t use clear plastic for this task! Although the process will take time, it does not require tools or heavy equipment. It is also a good method for no-till gardens, because it doesn’t disturb the soil. And if you can leave the cover on long enough, a tarp can lead to faster decomposition than simply mowing it. Be sure your cover is securely fastened so winds cannot lift it up. And if your cover crop is very tall, you may need to combine termination methods. Cut or mow it down first, then lay it on the surface of the soil so the tarp will lie flat.
Crimping
Less familiar to many home gardeners is crimping, or flattening a crop to destroy its vascular tissues. The goal is simply to crush the stems. This makes it impossible for the plants to transport water and nutrients, and leads to plant death. As with mowing, the crop is left on the surface of the soil to act as a mulch. Crimping works best when crops are in the reproductive phase, when they are directing most of their energy into flower and seed production. At that stage they usually cannot recover. You can buy a crimping tool, or make your own with a post or 2×4, using a rope attached to both ends as a handle. Crimping works well on crops such as buckwheat, barley, millet and oats. It can be combined with tarping.
Winter Killing
For winter killing to work, temperatures must be in the frost or freeze range, and the crop must be susceptible to those those temperatures. This will likely not be a good method for terminating a cool season cover crop like rye, crimson clover or Austrian winter pea. It may work on warm season cover crops such as cowpea, sun hemp or soybean. Typically, however, we remove those crops prior to frost.
Summary
Whatever termination method you choose, match it to the type of cover crop you have, and its stage of growth. Make sure it fits your gardening goals and tool or equipment use skills. Terminate the crop in time for it to serve its purpose to the next crop. By giving this stage of cover cropping a little thought, you can gain the maximum benefit and more effectively build your garden soil.
More Cover Crop Resources
For more information about types of cover crops, see Cover Crops for the Edible Garden on UF IFAS Extension Gardening Solutions.
To learn more about how cover crops can benefit your garden and soil, see the EDIS document Managing Cover Crops for Improved Soil Health at Ask IFAS.
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