The Knobtop series consists of moderately deep, moderately well drained soils formed in loess and the underlying residuum from igneous rock.
Permeability is moderately slow.
These soils are on uplands and have slopes of 2 to 14 percent. Mean annual temperature is 55 degrees F, and mean annual precipitation is 43 inches. Depth to bedrock ranges from 20 to 40 inches. Coarse fragment content is 0 to 25 percent for the A, E and Bt horizons and 5 to 60 percent for the 2BC horizon. Some pedons are stony on the surface.