I’m looking for a winter cover crop to improve my soil for next season. What are the best choices?
Planting a winter cover crop is a great way to store solar energy through the off-season in your soil and build fertility for the following year. Cover crops can improve soil texture, boost organic matter, prevent erosion, suppress weeds, and provide food and shelter for beneficial insects.
In general, there are two basic types of winter cover crops:
1) Those that grow vigorously in fall but are easily killed by cold temperatures (such as oats and barley, in most regions).
2) Those that survive winter cold and resume growth in spring (such as field peas, winter rye and hairy vetch).
The first kind is relatively easy to manage in spring, and you can then plant the area immediately with an early garden crop, such as carrots or peas. The trade-off is that you must sow these covers earlier to get adequate growth before the plants are killed by the cold. Oats, for example, should be sown by early September in the North and a few weeks later in the South.
The second kind of winter cover crop — those that overwinter and continue growing in spring — can be sown a bit later into fall, after most garden crops have been harvested for the last time. These covers use garden space longer in spring, and they must be pulled, chopped or mowed to be killed. They can be followed by warm-season crops, such as tomatoes or melons, or a late planting of brassicas or greens. To prepare spring beds faster, instead of turning under cover crops, cut them off at ground level and add the tops to your compost or use them as mulch.
If soil fertility and increased tilth are your main goals, choose an overwintering cover crop such as Austrian winter peas or hairy vetch. When turned under, these legumes not only add organic matter, but also boost nitrogen — 3.3 pounds per 1,000 square feet for winter peas and 2.6 pounds per 1,000 square feet for hairy vetch. Most veggies need 2 to 3 pounds of nitrogen per 1,000 square feet, so if you grow these cover crops, you won’t need to add additional nitrogen fertilizer for the following crop.
Although less winter-hardy than hairy vetch, Austrian winter peas offer a cool bonus: The tender young shoots are delicious in salads — just pick off the tips.
For details on which cover crops are best for your region, see Overview of Cover Crops and Green Manures, a publication by ATTRA, the National Sustainable Agriculture Information Service. Managing Cover Crops Profitably, a free, online publication, is also an excellent resource.
— Vicki Mattern, Contributing Editor
Above: Austrian winter pea shoots add crunch and flavor to winter salads — a bonus from this cold-hardly, nitrogen-fixing cover crop.
Photo by Nate Skow
Vicki Mattern is a contributing editor for MOTHER EARTH NEWS magazine, book editor and freelance magazine writer. She has edited or co-authored seven books on gardening, and lives and works from her home in northwestern Montana. You can find Vicki on Google+.