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Nutrients absent in red clay topsoil in North Georgia
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In terms of its natural setting, North Georgia can count many blessings.

Earthquakes are very rare, and never catastrophic. Hurricanes lose most of their force when they pass through. Many times, they have even helped break a summer drought by bringing much-needed rain.

Flash floods occur, but homes not located in a floodplain are usually safe. Even tornadoes, nature’s most violent windstorms, are rare compared to states farther to the west.

One item where we drew the short straw, though, is topsoil. The Piedmont and the Georgia mountains are very old. No glaciers moved across the area during the Ice Ages of the past 2 million years.

So the force of the sun, and countless years of rain, have washed nutrients out of the soil that are plentiful in the Midwest, where ice sheets plowed things over and under. What’s left here is a topsoil consisting mostly of clay. The calcium needed to keep acidity low is largely gone.

Most plants like to grow in an environment of near-neutral acidity. Chemically, that’s a pH of 7 (1 would be a strong acid, 14 would be highly alkaline).

In addition to needing input of lime to replenish its calcium content, clay has a few more undesirable qualities. It soaks up lots of water, as you can tell by the soft mud that forms in low spots during rain. But the clay also holds on to the water tightly, giving plant roots a hard time as they try to absorb it.

Experienced farmers and gardeners add organic matter to loosen up the soil texture. Compost is best. But even plowing the leaves from last fall into the ground instead of burning them improves conditions.

Yet another problem with the clay is that its density prevents water from soaking into it quickly. Instead, the resulting surface runoff makes it vulnerable to erosion.

Red streams going across the driveway during rain showers indicate the topsoil is washing away, or eroding. But topsoil, including our problematic clay, is a nonrenewable resource. It’s important to protect bare stretches of red topsoil with any kind of “cover crop.”

Clover is beneficial, but even rye grass serves the purpose. The action needed to protect our topsoil therefore consists of adding lime (the county Ag Extension Service can advise), organic plant matter and a plant cover that prevents rain from splashing directly onto it.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. 

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