South Carolina soils developed over a series of landforms that rise from the Atlantic coastal plain through the gently rolling upstate Piedmont to the base of the Blue Ridge Mountains. Soils of the coastal plain and their associated inland sand hills are generally sandy and well drained. As elevation increases from east to west across the state, soils are deeper and more fertile. Does this Spark an idea?
The coastal plain soils are relatively infertile. Nutrients are leached out by 36 to 52 inches of rainfall annually. They are sandy to loamy (some clay) sand in the upper 12 inches, with subsoil of loamy sand to loam (clay and sand equal). Hard pans restrict the root zone unless broken by deep plowing. Available water is in the top 2 feet. In contrast, deep, strongly acidic soils of the gently rolling Piedmont developed over bedrock and retain the rock’s fertile weathered minerals.
Charleston County is a representative South Carolina coastal location. There are 11 soil types in its 919 square miles, ranging from the frequently flooded Tidal Marsh group along the coast to the well-drained Wondo-Seabrook group developed on level terrain or gentle slopes. Wondo-Seabrook is found at the highest elevations (6 feet) of Edisto Island, James Island and North Charleston. In Francis Marion National Forest, Sewanee-Rutledge well to poorly drained soils developed on nearly level, low ridges above the Rutledge-Scranton-Pamlico group of poorly drained to mucky soils in Big Wambaw Swamp.
Edgefield County is representative of the Piedmont Uplands in western South Carolina on the Georgia border. Most of the 480-square-mile county is gently sloping and well drained, with clay subsoil under a loamy surface layer suited for agriculture. However, the Lakeland-Troup-Wagram group in southeastern Edgefield County are deep, well-drained to dry soils with sandy surface soil and loamy or sandy subsoil developed on gently sloping to steep ridges.
Oconee County upstate borders North Carolina and Georgia. About 60 percent of the county’s 652 square miles is Piedmont Plateau, a 200- to 1,000-foot plain fronting the Blue Ridge Mountains. The remainder of the county is mountainous. Soils fall into two groups: alluvial soils of fine sandy loam developed over recent stream deposits, and residual upland soils developed mostly over granite, gneiss and mica schist. The residual soils all have red sandy clay subsoils. The residual Cecil topsoils are 5 to 8 inches deep brown sandy loam containing quartz fragments. The residual Porter topsoils are 6- to 12-inch gray to yellow fine sandy loam.
For South Carolina, the Natural Resource Conservation Service selected deep, poorly drained Lynchburg soils as the “state soil.” Lynchburg developed in depressions on 865,000 acres of marine coastal plain sediments from Virginia to Alabama. Half of all Lynchburg is in South Carolina. Well-drained Lynchburg makes excellent farmland, but wetter Lynchburg supports loblolly pine (Pinus taeda). The surface layer is black loamy fine sand, with grayish brown loamy fine sand subsurface. Upper subsoil is brownish-yellow fine sandy loam, over subsoil of gray sandy clay loam.