I first learned about how to use cover crops in a workshop I attended on organic gardening. As I listened to the instructor, it made perfect sense that cover crops were a good option for my home garden because they provide care and feeding to the soil. Cover crops are one of the tools that organic gardeners can use to build healthy soil. Crop rotation is another practice that when used in conjunction with cover crops can result in superior vegetable production.
In the first half of the 20th century, cover crops were used extensively by farmers With the introduction of herbicides, farmers started moving away from cover crops in the 1950s. Today, there is increased focus on soil health and this has led to a renewed interest in the benefits of cover cropping.
Soil is a living ecosystem and is a farmer’s most precious asset. A farmer’s productive capacity is directly related to the health of his or her soil.
Howard Warren Buffett
COVER CROPS DEFINED
A cover crop is a crop that is planted, not for harvest, but rather for soil improvement. Grains, grasses and legumes are types of cover crops. Late summer/early fall is the most common time to plant. In the spring, the cover crops are incorporated into the soil before planting the first spring crop. Cover crops are also known as ‘green manure’ because they improve the overall quality of the soil. While fall is the most common time to plant, there are other timing considerations:
- ‘Over winter’ crop (e.g. planted late summer/early fall).
- ‘Under sown’ crop meaning that you plant under a crop to be harvested like tomatoes or cucumbers.
- ‘Main’ crop, in this case, the cover crop is in place of a regular vegetable crop. This may be useful if a garden bed will not be used for the coming season.
TYPES OF COVER CROPS
There are two broad categories of cover crops:
- Legumes (Field Peas, Hairy Vetch, Clover)
- Nonlegumes/grasses (Annual ryegrass, Barley, Oats, Rye, Wheat). Note, winter wheat and rye can be difficult for the home gardener to turn under in the spring due to the deep roots that develop.
To determine the best cover crop to plant, it is important to have a goal. As a home gardener, my goal is to improve the overall soil structure and add nitrogen/organic matter to the soil. I also want a cover crop that will be easy to incorporate into the soil come spring. In my vegetable garden beds, I have used both hairy vetch and clover. Gardeners who want to work their soil in early spring should consider a winter-kill cover crop such as oats. In the US, gardeners who want to start cover cropping can contact their county Cooperative Extension agent to find out more about which options are most suitable for their region.
Red Clover
BENEFITS OF COVER CROPS
The benefits vary depending upon the type of crop planted. It is also possible to plant two different varieties of cover crops together. This improves the chances of success and you can get the benefits from both categories. Here is an overall summary of the benefits:
|
Benefit |
Legumes |
Nonlegumes/Grasses |
|
X |
X |
|
X |
X |
|
X |
X |
|
X |
|
|
X |
X |
Broadfork
Compost
HOW TO PLANT COVER CROPS
When planting cover crops as an overwintering crop, allow the crop to get four weeks of growth before the weather turns too cold. In northern climates, this would mean planting sometime between mid-August and mid-September.
- Remove any mulch that might remain from the previous crop.
- Loosen up the top six inches of your soil with either a pitchfork or a broadfork.
- Add a one-inch layer of compost to the soil. It is also helpful to add a balanced fertilizer (such as 15-15-15) to the soil.
- Gently rake the compost and fertilizer into the soil.
- Dampen the soil with water.
- Broadcast the seeds over the soil based upon the rate given on the seed packet.
- Gently rake the soil and seeds.
- Water the seeds. Just like all other seeds, it is important to keep the soil moist during germination.
In the spring, when the soil is dry, incorporate the cover crop into the soil before planting the first spring crop. Depending upon the crop planted, you may want to use a trimmer to chop and shred the crop as this will allow for faster decomposition. Then use a pitchfork or shovel to incorporate into the soil. Plan to incorporate the cover crop 3 weeks ahead of the planting date for the spring crop. This will allow enough time for the cover crop to decompose and add organic matter to the soil. Finally, watch the growth pattern and be sure that you incorporate the cover crop into the soil before it goes to seed. If a cover crop goes to seed, it can become weeds and compete with vegetable crops.
Check out my blog post on Autumn clean-up in the vegetable garden for tips on preparing your garden for the winter.
Good luck!
REFERENCES
Oregon State University Extension Cover Crops for Home Gardens
Penn State Extension What Cover Crop should I plant?
University of Maryland Extension Cover Crops: Protect and Improve your Soil
University of Wisconsin Extension Using Cover Crops and Green Manures in the home vegetable garden
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