The Geff series consists of very deep, somewhat poorly drained soils formed in 24 to 40 inches of loess or other silty material and the underlying stratified loamy outwash on low stream terraces and flood plains.
Permeability is moderately slow.
Slopes range from 0 to 5 percent. Mean annual air temperature is about 54 degrees F., and mean annual precipitation is about 42 inches. The solum ranges from 50 to more than 80 inches in thickness. Depth to the loamy outwash sediments is 24 to 40 inches. The particle size control section averages from 27 to 35 percent clay and ranges from 0 to 10 percent rock fragments.