Creating healthy soil is a key concern for any gardener. Even in regions where the soil is rich, it can become depleted if not cared for properly. Sowing a cover crop will add vital nutrients and organic matter back into the soil, prevent soil erosion, help loosen compacted soils, and even help control weeds.
Maybe you have heard about cover crops, but think they are only for large farms. Think again. Cover crops will work with gardens of any size, even raised beds! Here’s a guide to help you get the full benefits of a cover crop.
Step 1: Planting
If you have ever replanted a patch of grass in your lawn, it is as easy as that! After harvesting the last of the crops in the area you intend to plant, till the area to a depth of about 3-4 inches. For a small area, like raised beds, use a hoe; for larger areas a rototiller will do the job. Then simply broadcast the seed and rake it in. Raking allows for good seed-to-soil contact and helps protect the seed from birds.
Step 2: Care
Cover crops are pretty low maintenance compared to most crops, but they still require some care. Some cover crops need to be mowed. For example, mowing sorghum-sudangrass will increase its root growth. Also, left unchecked it can grow to 12 feet tall! White Dutch clover, a common cover for garden paths, needs to be mowed regularly to prevent it from competing with veggies and flowers.
Step 3: Kill and Till
You must kill your cover crops before they set seed and the growth get out of control. Depending on how tall the crop is, this can be accomplished with a mower or string trimmer. After mowing, wait for the plants to dry out before tilling them under.
After turning under a cover crop, wait for 2-3 weeks before tilling again and planting vegetables or flowers. The decomposition of the green material can interfere with plant growth. Also, cover crops such as rye are allelopathic, which means they produce biochemicals that inhibit seed germination.
Common Cover Crops
Legumes are known as “nitrogen-fixing” plants. Symbiotic bacteria in their roots pull nitrogen from the atmosphere and convert it to a form plants can use. These plants add organic matter to the soil with the added bonus of nitrogen.
Hairy Vetch (Vicia villosa):
Grows 2 feet tall; hardy to -15F. Hairy vetch is considered the hardiest of annual legumes. Sow 1 to 2 pounds per 1,000 square feet.
Field Peas (Pisum arvense and P. sativus):
Grows 6 inches to several feet tall. Field peas are hardy to 10 to 20F. Sow 2 to 4 lbs per 1,000 square feet.
Berseem Clover (Trifolium alexandrium):
Grows 1 to 2 feet high, hardy to 20F, and produces high amounts of nitrogen. Sow 2 lbs per 1,000 square feet.
Crimson Clover (T. incarnatum):
Grows 18 inches high, and is hardy to 10F. Crimson clover fixes less nitrogen than other clovers, and matures later. If allowed to seed, it can become invasive. Sow ½ to 2 lbs per 1,000 square feet.
Cover crops from the grass family grow quickly, tolerate cold, and improve the quality of compacted soils. Thickly sown grasses add increased organic matter in comparison to legumes. Grasses also help prevent soil erosion.
Annual Ryegrass (Lolium multiflorum):
Grows 2 to 3 feet high, fast growing, and tolerates flooding. Sow ½ to 2 lbs per 1,000 square feet.
Winter Rye (Secale cereal):
Grows 4 to 5 feet high, hardy to -30F, and is great for cold winter climates. Sow 2 to 3 lbs per 1,000 square feet.
Oats (Avena sativa):
Grows 2 to 3 feet tall; hardy to 10 to 20F. Produces the least organic matter of grasses, but is tolerant of wet soils. Sow 2 lbs per 1,000 square feet.
Barley (Hordeum vulgare):
Grows 2 to 3 feet tall; hardy to 0 to 10F. Fast maturing and tolerant of dry soils. Sow 2 to 3 lbs per 1,000 square feet.
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