5.6 - Mollisols

The Mollisol order takes its name from the Latin word mollis, meaning soft. These mineral soils  have developed on grasslands, a vegetation that has extensive fibrous root systems. The topsoil of Mollisols is characteristically dark and rich with organic matter, giving it a lot of natural fertility. These soils are typically well saturated with basic cations (Ca2+, Mg2+, Na+, and K+) that are essential plant nutrients. These characteristics of Mollisols place them among the most fertile soils found on Earth.

Soil order - Mollisols. Image courtesy of USDA-NRCS

Profile example - Drummer Series. Image courtesy of USDA-NRCS

USDA Details

Further Information by the University of Idaho

Key Characteristics:  Mollisols – Grassland Soils

  • Mineral soils developed under grassland vegetation
  • Thick, dark-colored ‘A’ horizon, rich in organic matter 
  • Dominant soil order of the North American Great Plains region.
  • Large areas of Mollisols are also found in Eastern Europe, Russia, China, and South America.
  • Generally very fertile for plant growth due to clay and organic matter content.
  • Considered to be among the most fertile soils on Earth.
  • Extent of world ice-free land area: 7%

U.S. Order Distribution Map for Mollisols. Image courtesy of USDA-NRCS

Further Detail by the NRCS



One of the key factors in the development of Mollisol Order soils is the prevalence of grassland vegetation. Which of the following elements would be most limiting to the development of woody shrubs and trees in a semi-arid grassland ecosystem?‏

Looks Good! Correct: Yes! Hot-burning prairie fires kill young woody plants and trees, but stimulate the growth of native prairie grasses.