Originally created 11/17/00

Cover crops can enrich garden's soil



If you have a vegetable garden and only grow summer vegetables or only a few fall crops, it's time to consider ways to enrich your soil for next year's growing season.

One of the best things you can do for your garden is to plant a cover crop.

Cover crops conserve nutrients, support beneficial biological activity and produce superior soil structure. When you plow them into the soil, they're sometimes called green manures.

Green manures offer succulent growth, which decomposes easily in the soil, releasing nutrients. While they're smothering weeds, they also keep nutrients from leaching away and protect the soil over the winter.

Cover crops are any plant you sow into the garden that improves the soil. The actual benefits depend on the plant type and how much you grow.

Traditional choices for green manures are buckwheat, small grains such as rye and oats, and annual grasses such as ryegrass and wheat.

Other crops are possible. Rapeseed, for instance, makes a good green manure. But don't follow it with another planting of the cabbage family.

Sometimes legumes are grown. Austrian winter peas are a good choice to improve the soil.

Annual cover crops are turned into the soil while still green, normally just before they flower. Their greatest value is usually in the top growth. But the roots are often beneficial, too.

Varieties are chosen for their fast, vigorous growth and high production of green, succulent top growth. The green matter decomposes quickly in the soil. When it does, the result is a flush of biological activity and a quick release of nutrients, some of which the roots may have accumulated from the subsoil. The succulent residues replace some of the humus, building a dynamic soil system.

The downside of growing a green manure is that is requires the garden to be left idle for a time. That's unpopular with many gardeners.

The green manure sod not only feeds soil organisms, it also protects the soil from direct sunlight and rain.

Through the years, the combination of the high biological activity and the extensive root system of grass leads to a superior soil structure and a slow but steady increase in soil humus. When a green manure sod is plowed under, a rapid breakdown occurs with a sudden release of nutrients stored over a long time. That's why a crop cultivated after a green manure sod is usually very successful.

VEGETABLE GARDEN PESTS: During this time of year, the disease white spot can be a problem on turnips, mustard and collards. It does not kill the plant but will cause spotting and necrotic areas on the leaves.

The disease thrives in wet weather, which we certainly haven't had, but a lot of watering can also cause it. Water your plants early in the morning when dew is already on them so that the moisture will dry as the day progresses.

Excess nitrogen also promotes infection. Mulches such as straw or bark are helpful to keep soil from splashing on the plants and will reduce infection. Available fungicides for control are Top Cop Tri-Basic, Top Cop with Sulfur and Maneb. Maneb has a 14-day pre-harvest interval.

WATCH FOR APHIDS on your plants, especially broccoli. They will be on the underside of the leaves. Spray them with an insecticide such as Malathion or an insecticidal soap.

Sid Mullis is director of the University of Georgia Extension Service office for Richmond County. Call him at 821-2349, or send e-mail to smullis@uga.edu. The offices that serve Richmond and Columbia counties have a Web page at www.griffin.peachnet.edu/ga/columbia.