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Soil Genesis and Development, Lesson 5 - Soil Classification and Geography

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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 Key Characteristics U.S. Order Distribution Map Profile Examples

Mollisols

Click on the image to study, and click on the expanded image to read the detail.

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%

 

Further Details

 Drummer Series

USDA details

More information

All images courtesy of USDA-NRCS

 
Question 13:  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?

A. Insufficient rainfall for tree growth
B. Low soil fertility
C. Prairie fires during periods of low rainfall
D. Beavers and other wildlife
E. Human cultivation and agriculture

 

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