Parent Materials/Geology
Soils in eastern South Dakota are derived primarily from glacial till, glacial outwash, loess, and lake bottom sediments associated with the Wisconsin glaciation period. Excellent crops can be grown on soils derived from glacial till and lake bottom sediments since the soils form on nearly level landscapes, have favorable drainage, good water holding capacity, and good root penetration characteristics. Some soils formed on glacial outwash and moraine deposits are very stony, steep, or poorly drained so they are less suitable for cultivation. In the extreme southeastern part of the state, soils were formed on parent materials deposited from an earlier glaciation event. Crop production potential is excellent on these soils and land prices are the highest in the state because of their great yield potential.
Soils near the Missouri River have a very thin veneer of glacial parent materials because they occur near the terminus of former glacial activity and erosion removed most of it. The shale or limestone bedrock is very close to the surface. Soils formed on the shale have characteristics similar to the soils of western South Dakota. They have poor drainage and are somewhat droughty. Farmers refer to these soils as "gumbo soils".