Published on 08/14/08

Wheat, rye and grasses are all cover crops

By Bob Westerfield
University of Georgia

As we prepare for the brisk fall air to arrive, summer gardens may begin to look a little anemic. Many gardeners choose to let their gardens fizzle out slowly and be finished off with a final blow from the first frost.

Rather than letting summer vegetables die out and leaving the soil exposed, a much better idea is to consider planting a winter cover crop. Cover crops are usually grasses or legumes, such as clover, planted on the existing garden site to help hold and build up the soil.

Cover crops have many pros

The benefits of growing cover crops include:

• reduced erosion

• improved soil structure and reduced surface crusting

• increased water-holding capacity of the soil

• reduced winter weed growth

• reduced herbicide injury

• hardpan penetration in the winter

• improved soil relations for the next crop

• nitrogen production(if the cover crop is a legume)

Soil improvement through the use of a cover crop is a long-term venture. Cover crops can and will add organic content to the soil over time.

Too legume or not to legume

There are two general types of fall cover crops – leguminous and nonleguminous. Leguminous cover crops, such as vetch and clover, add nitrogen to the soil. Nonleguminous ones, like wheat and rye, are preferred on soils that erode.

Crimson clover is probably the most commonly used and most desirable of the clovers grown as cover crops. It matures earlier and produces more nitrogen and dry matter earlier than most other clovers. An excellent crop of crimson clover can produce up to 120 pounds of nitrogen per acre. However, production of 30 to 50 pounds of nitrogen is more common.

Nonleguminous cover crops, such as rye, ryegrass and wheat, have several advantages. They are less expensive to establish and they provide longer and better erosion control because they produce more winter growth and a more fibrous root system.

However, nonleguminous cover crops do not create nitrogen and usually require some nitrogen fertilizer when planted.

It is important to plant cover crops early to establish early root growth before cold weather occurs. This helps the crop better survive a hard winter. Grasses should be planted in early October to mid-November, and legumes should be planted in mid-September to mid-October.

A soil test from a University of Georgia Cooperative Extension agent will accurately determine lime, phosphate, and/or potash needs for the cover crop you select. If applications are needed, apply in the fall just prior to seed bed preparation.

If you are growing a legume cover crop, do not add nitrogen fertilizer. It is important to treat the seed with the correct nitrogen-fixing bacteria (inoculant) to ensure good germination.

Prepare the garden site

Prepare the seed bed just as you would for a spring garden. Either remove or till in old crops and work the soil while it is slightly moist, but not wet. Grass type cover crops should be raked or dragged in to a depth of one-half inch. Clover type cover crop seed is very tiny and should be lightly raked to provide good soil contact without burying the seed.

Cover crops, or green manures as they are often called, are an economical way to both protect and build soil. Their bright green colors also make what was a drab and brown garden plot more attractive. When spring arrives again, cover crops should be tilled in to help feed next year’s crop.

Bob Westerfield is a University of Georgia Cooperative Extension consumer horticulturist with the College of Agricultural and Environmental Sciences.