Houdek is a type of soil composed of glacial till and decomposed organic matter. The soil series was established in 1955 in Spink County, South Dakota. It is unique to the United States, but in particular to South Dakota where it is the state soil. Surface layerDark grayish brown loamSubsoil - upperDark grayish brown clay loamSubsoil - middleGrayish brown clay loamSubsoil - lowerLight olive brown clay loamSubstratumLight yellowish brown clay loam