Ruth Correll: Benefits of cover crops

Ruth Correll • Updated Aug 2, 2017 at 9:45 PM

Cover crops planted in late summer are an inexpensive way to build better soil for gardening. Cover crops often are called green manure crops. They are grains, grasses or legumes that will grow during fall and winter and that you can plow, spade or till under in the spring.

During their growth, cover crops help reduce soil compaction and prevent erosion. Their roots penetrate and help loosen heavy-textured soils, allowing better air and water penetration. Inoculated legume cover crops add nitrogen to the soil. When you turn cover crops under, they add organic matter to the soil – building better soil structure and fertility.

A deep-rooted cover crop allowed to grow for two seasons in problem soil can help break up a hardpan and greatly improve soil tilth. Cover crops also are called catch crops. A growing grass or legume crop catches and uses the nitrogen and other mineral nutrients that winter rains might otherwise leach away.

When you turn the cover crop under in the spring, these nutrients return to the soil, ready for your crop of vegetables. Nearly all garden soil needs organic matter to maintain the bacteria, fungi, earthworms, and other forms of life needed to make a healthy, fertile soil. However, organic matter is quickly used in the food chain of earthworms and other soil organisms – so you will need a continuous supply. In addition to green manure crops, manures, sawdust, bark dust and composts also supply organic matter.

Cover crops should grow quickly, cover the area to shade out weeds and be easy to work into the soil in the spring. You can combine a legume with a grass or cereal plant crop to produce and store nitrogen. Vetch with rye or oats, or Austrian peas or garden peas with winter wheat or rye make good combinations for the home garden

You can plant cover crops in your garden from about mid-August until late September. Plant them early enough to be well established before cold weather arrives. If fall vegetable crops are still growing in your garden, plant the cover crops between the rows. 

Before planting your cover crop have your soil tested to correct deficiencies in plant nutrients or pH. Depending on your soil type and pH, you may need to lime or add phosphorus or potassium to correct deficiencies in plant nutrients or pH extremes.

Plant your cover crop early enough to permit 4 weeks of growth before cold weather stops that growth. After preparing the soil, you can plant large-seeded cover crops such as peas, vetch and wheat in shallow, closely spaced furrows. Broadcast small-seeded crops such as clover, annual rye, small grains, turnips or buckwheat over the surface and cover with a light raking. If the soil is dry, irrigate often enough to keep the soil damp and germinate the seeds.  

Some cover crops may be killed during the winter, but they are valuable as they provide cover for the soil to conserve moisture and prevent weeds and in the spring can easily be incorporated into the soil.

In the spring, as soon as the ground dries enough for tilling or plowing, turn the cover crop under. To allow time for the organic matter to decompose, turn the cover crop under at least three weeks before you intend to plant. If the cover crop is too tall to turn under easily, mow it first. Do not allow cover crops to go to seed. Some, such as vetch, annual rye or small grains may become weeds in the garden if they are allowed to spread seeds.

Organic matter additions to the soil are a continuing necessity. You can supply organic matter through manure, compost, vegetable matter or animal matter – or through an annual planned program of cover-crop planting and management.

For more information, contact the UT-TSU Extension Office in Wilson County at 615-444-9584. You can also find us on Facebook or visit extension.tennessee.edu/wilson. Ruth Correll, UT Extension-TSU Cooperative Extension agent for Wilson County, may be reached at 615-444-9584 or [email protected]


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