Indiana has several different soil types scattered throughout its terrain. Different types of soil are formed by different types of source materials (such as rock and organic matter), differing erosion and weathering patterns, and different ecosystems. The type of soil in a region exerts a great effect on the type of agriculture that can be done there, if any at all. Indiana is dominated by agriculturally productive soil, but there are a few regions where the soil is not productive.
Alfisols are by far the most common soils in Indiana. These soils are formed for the most part underneath forest cover in climates ranging from humid to semiarid. The subsoil is high in clay and nutrients. These soils can be very productive in terms of agriculture, but can deteriorate rapidly if not conserved. Erosion is very damaging to these soils.
Mollisols are the second most common soils in Indiana, but are only dominant in the northwest corner of the state. These soils form under grasslands and are rich in organic matter, derived primarily from the decayed roots of the grasses. They are very productive agriculturally. The soil holds water very well and has a soft, light texture.
In the southern part of Indiana there are a few large areas where inceptisols are dominant. These soils are undeveloped and can have a wide variety of features. Generally they are found on steep slopes or bedrock that is close to the surface. These soils are young and do not exhibit much evidence of weathering. They are often used more for recreation or watershed than for agriculture, as evidenced by their strong presence in the large national forests and parks in the southern portion of the state.
Histosols are scattered throughout the northernmost quarter of Indiana. They are high in organic matter and contain large amounts of carbon. These soils are present primarily in swamps, deltas or marshes. They do not drain well and retain significant moisture. Histosols make good agricultural soils when drained, but they will decompose quickly.
Entisols are quite undeveloped and are found primarily in areas of high erosion, such as flood plains, sand dunes, steep slopes and hard rock. Like the inceptisol order, they are young. Nevertheless, they are used for agriculture in many areas. In Indiana they can be found in the northeast and southeast.