The Regions Soils

Varied edaphic materials and inconsistent slopes in the Coastal Plain's physiographic regions and subregions under the influence of climate, vegetation, and microorganisms have resulted in soils classed mainly as red-yellow ultisols. These are sediments in which iron and aluminum are slowly leached from the surface soil into the subsoil. Movement of iron is particularly noticeable, as the soils in which podzolization is advanced are lighter-colored at the surface and darker red below. Oxidation of the leached iron results in the red color, exemplified by the rust of a safety pin or jackknife left out in the weather. As the pin or knife soon will not open and close because of the rust of oxidation, so too subsoils are stiffer—the particles "rusted" together—than those at the surface. When a spade is thrust into the ground, it is suddenly impeded when the tool meets the denser subsoil somewhere between 4 and 40 inches below the surface.

Classifiers refer to the soils of the Appalachian Mountains as gray-brown alfisols. True podzols occasionally interrupt the surface strata of these podzolic soils at the higher elevations. Gray color at the surface indicates their presence, for the word podzol, from the Russian, means ash-white. (Soils like the true podzols occur in cold, moist climates throughout the world.)

Podzolics are in the process of becoming true podzols as iron and aluminum oxides leach from the surface to the lower horizons of the soil. It is the loss of those elements that gives the light color to the soil particles. With podzolics, leaching is never complete, so the reddish color of iron oxide does not disappear. Lithosols, denoting shallow soils containing many weathered rock fragments, even at the surface, are relatively recently derived and are usually found on ridges of the South's mountainous areas. Calcareous black soils are called rendzinas. These are found on the

Figure 1.4 Average annual precipitation. Within the area outlined by the dotted line, summer rainfall is 40 to 50% of the annual total; elsewhere it is 50 to 60%. (after USDA, 1941; and G. Trewartha, 1961)4
Figure 1.5 Average annual number of days with thunderstorms. (after USDA, 1941)5

Figure 1.6 Horizons of virgin forested soils in the Piedmont province. The upper A horizon contains perhaps 5% organic matter. The B consists of more compact clay, while the C is mineral parent material from which the soil was derived through weathering and dissolution. Here the D zone of bedrock contains partially weathered material.

Figure 1.6 Horizons of virgin forested soils in the Piedmont province. The upper A horizon contains perhaps 5% organic matter. The B consists of more compact clay, while the C is mineral parent material from which the soil was derived through weathering and dissolution. Here the D zone of bedrock contains partially weathered material.

non-forested prairies that occur as a crescent in Alabama's midsection and the finger-like intrusions into Texas from Oklahoma at the western edge of the southern forest. Old seabeds of marl or chalk encourage the development of these soils in humid zones.

As the South escaped glaciation, its soils lack the accumulation of the many nutrient-supplying minerals released from the rocks that were carried and ground into powder by the massive movement of the ice sheet, as in the Northeast and Lake States.

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