More than half of the soils in Wisconsin are highly fertile and are used for agriculture and forestry. The rest of the soils are highly acidic or weathered. A small area of the state is comprised of a type of soil normally found in the southern part of the United States.
Most soils in Wisconsin are alfisols that developed under broad-leaved forests. Alfisols are fertile, low-acid soils with rich clay subsoil. They are some of the most productive soils in the state and are good for agriculture.
Mollisols, which comprise 10 percent of the soils in Wisconsin, are also some of the most productive in the state. They are fertile with a dark brown or black organic surface layer. Mollisols developed under grasslands, and most are now used for croplands.
Spodosols are found primarily in the northern half of Wisconsin and comprise about 19 percent of the state's soil. They developed under coniferous, and mixed deciduous and coniferous forests. Spodosols are acidic with lower layers of iron and aluminum oxides.
About 11 percent of the soils in Wisconsin are entisols, which are poorly developed and lack horizons. They developed from young or active parent material, such as sand dunes and river sediments. Entisols are found on steep slopes and floodplains where parent material has difficulty accumulating.
Inceptisols are slightly more developed than entisols and are beginning to form horizons. They are also found on steep slopes and river sediments with young or active parent material. Inceptisols comprise 4 percent of the soils in Wisconsin.
Histosols developed in bogs and swamps where organic matter decomposed slowly and accumulated over time. They are organic soils with a dark upper layer. Histosols comprise 8 percent of the soils in Wisconsin.
Ultisols are more common in southeastern United States and only 600 acres exist in Wisconsin. They are formed from thin layers of silt over sandstone. Ultisols are weathered, clay-rich soils that contain iron and aluminum oxides. They are often red or yellow.