Houdek Soil Series

Houdek soil is a Mollisol with an argillic horizon — a clay-rich layer that developed beneath the dark prairie surface as fine particles migrated downward over thousands of years. That combination of a thick dark topsoil above a clay subsoil makes Houdek both fertile and moisture-retentive, which matters in eastern South Dakota's semi-arid climate.

The soil formed in Wisconsinan-age glacial till, the rocky debris left by the Laurentide Ice Sheet when it retreated 10,000 to 12,000 years ago. Mixed-grass prairie — blue grama, western wheatgrass, needlegrass — then grew on the rolling landscape for millennia, building the deep organic layer that farmers plow today.

Soil scientists at the USDA Natural Resources Conservation Service selected the Houdek series to represent South Dakota because it is the dominant soil of the Coteau des Prairies — the rolling upland that defines the state's wheat and corn farming region and covers more cropland than any other soil in the east.

The series is named after the Houdek family, South Dakota farmers whose land contained the type location where USDA soil scientists first formally described and classified the series. The type location is in Beadle County in east-central South Dakota.

Houdek soil is recognized by the USDA as South Dakota's state soil. It was selected because it captures the semi-arid glaciated prairie landscape that separates South Dakota from the more humid soils of neighboring Minnesota and the drier soils of the Missouri Plateau to the west.

Dig into Houdek soil and you start in very dark brown loam — nearly black at the surface, loose and crumbly from decades of plowing and centuries of prairie grass roots. Below the plow layer, the dark color persists through a second organic-rich horizon. Then the soil shifts: a brown, sticky clay loam marks the argillic horizon, tighter and denser than anything above. Deeper still, white streaks of calcium carbonate trace through a paler brown layer above the glacial till.

Houdek soil covers the Coteau des Prairies — the glaciated upland plateau that forms the eastern third of South Dakota between the Big Sioux River valley and the James River valley. It sits on upland summits and side slopes at elevations of 1,500 to 2,000 feet, in areas that receive 17 to 22 inches of precipitation per year.

Beadle County holds the type location and the densest concentration. The soil extends through the central coteau counties — Jerauld, Sanborn, Miner, Kingsbury, Hamlin, and Codington — and into Clark and Spink counties to the north.

Spring wheat is the signature crop on Houdek soil. South Dakota ranks among the top wheat-producing states, and the coteau counties underlain by Houdek soil contribute a large share of that harvest. The argillic clay layer stores enough moisture from spring snowmelt and early rains to carry wheat through the dry June and July stretch.

Corn and sunflowers have expanded onto Houdek soil in recent decades as drought-tolerant varieties reached the market. Soybeans appear on the warmer, wetter eastern margins. Flaxseed and oats are grown in rotation with wheat on farms that have maintained traditional Great Plains cropping systems.

Before dryland farming arrived in the late 1800s, Houdek soil supported northern mixed-grass prairie: western wheatgrass, green needlegrass, blue grama, and buffalograss. Small native prairie remnants persist along road margins and in prairie potholes — the shallow wetlands that dot the coteau and support some of the densest waterfowl nesting habitat in North America.