Soil Descriptions/Profiles

Soil Forming Factors

The continuous growth of prairie grass species for thousands of years before the agricultural development of European settlers has imparted a distinctive black color to the topsoil. Soils of eastern South Dakota have a thick dark surface layer (8-24" depth) in which the organic matter level is often 3-5%. The thickness of this "mollic" horizon indicates the depth to which roots have penetrated. Organic matter from the grass residue and roots do not decompose easily because of the lower annual mean soil temperature and lower precipitation compared to soils east and south of the region.

Most eastern South Dakota soils are in the silt, silty loam, and silty clay loam textural classes. The soil pH of the topsoil can range from 5.5 to 7.8 depending on the drainage and calcium carbonate content. Soils with high free carbonates (Na, Mg, or Ca) or sulfates sometimes have visible surface salt accumulation, precipitates, and/or calcareous nodules. The pH of the subsurface soil is often higher than the topsoil Soils on hilly terrain. Eroded soils with shallow surface horizons sometimes have calcareous nodules on the surface.

The subsoil of some soils have a buff colored silty layer which is characteristic of the loess parent material. Soils formed on glacial outwash have deep sandy or gravelly subsoil horizons with very good drainage, but tend to be droughty. However, water accumulates in these layers to form shallow water aquifers (20-80 ' from the surface) which provide drinking water to many cities and irrigation to growing crops.

Typical soils of eastern South Dakota and their parent materials might include:

Additional information about soils can be found at the Soils Resource web site compiled by the Natural Resources and Conservation Service (USDA).

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