• A typical prairie scenerolling countryside image by Derek Abbott from Fotolia.com
  
  The American prairie was formed after the last ice age. For several thousand years the climate was conducive to the growth of forests. According to the University of Illinois Natural History Survey, the formation of grassland prairie came about as the climate became warmer and drier.
  
  The prairie was further shaped by the effects of fire and grazing. Fast-moving fires swept the grassland, releasing nitrogen-rich nutrients to be absorbed in the soil, while the waste products of large numbers of grazing animals further enriched the prairie soil.
  
  

Sand Prairie Soil

• Sand prairieprairie image by davidphotos from Fotolia.com
  
  The glaciers retreated across North America and reshaped the lands as they moved. Glacial moraines formed when the great quantities of rock and soil carried by the glacier were left behind by the melting ice. Sand prairie formed on the sandy glacial outwash plains.
  
  According to Michigan State University, dry sand prairie soil is an acidic, sandy mix of soils called loam. The vegetation supported by sand prairie soil is usually sparse and patchy.
  
  

Blacksoil Prairie

• Blacksoil prairiePrairie Dog eating image by BHP from Fotolia.com
  
  The North American prairie is characterized by the black soil found in many areas. This mixture of clay, silt, and carbonate materials is some of the most fertile soil in the world. The soil formed under prairie grasses in the American West and Midwestern states.
  
  According to the United States National Park Service, the soil deposited by the glaciers was subjected to hot summers, freezing winters, wildfires that burned the grass, and the effects of grass decomposition.
  
  Grazing animals left their wastes behind as nutrients to enrich the soil. Over thousands of years, this process created the rich black loam the pioneers had so much trouble plowing in the 1800s.
  
  

Loess

• Loess, a sediment composed of clay and silt, is a common component of prairie soils. After the glaciers retreated, the wind transported silty soil from the river valleys and deposited them in large amounts on the surrounding uplands. These accumulations of loess soil became hill prairies.
  
  According to the Missouri Department of Conservation, the loess soils drain rapidly. This, in conjunction with high sun exposure and wind activity, has led plant life in the loess prairies to develop strategies for retaining moisture, such as small or waxy leaves.