Department of Agriculture and Soil Physics
All that portion of South Dakota lying east of the Missouri river is covered by what is known as drift or boulder clay, except a few small isolated areas. This formation varies in depth from a few feet to two or three hundred feet, and when the entire mass of the deposit is considered it is of a remarkably uniform character throughout the state. Its chief characteristic is a light yellow color with numerous small, calcareous masses and more or less boulders, stones and pebbles in the subsoil, gradually merging into a dark brown or black loam on the surface. This dark color is due to the presence of decaying vegetable matter and the action of the elements. The sorting powers of running water, moving ice and blowing winds have caused quite a variation in the appearance of the surface in various localities throughout the state. This difference is, however, largely superficial and, in most instances, does not extend to any considerable depth. Wherever the surface soil shows any marked deviation from the normal of the state, it is not difficult to find a cause for that deviation in forces that have been at work since the time when the whole area was covered with the ice sheet. For instance, that portion of the state included within Spink, Brown, and portions of Beadle counties was once, since the glacial period, occupied by a shallow lake bed. Into this lake were brought the washings of the surrounding hills. The wave action in the lake affected a separation of the coarser from the finer particles, depositing the fine lay and silt over the bottom of the lake in a nearly level, uniform layer, while much of the larger, heavier portion remained near the margin and formed sandy beaches. The remains of these beaches are easily seen in the character of the soil in the western part of Brown county, the central portion of Beagle county, and along the foot of the hills, both on the east and on the west side of this old lake bed.
irrigation, soil moisture, soil composition
U. S. Experiment Station of South Dakota, South Dakota Agricultural College
Chilcott, E.C. and Holm, A.B., "Moisture Investigations for 1897" (1898). Agricultural Experiment Station Bulletins. 58.