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

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5.7 - Alfisols

Alfisols are found in cool to hot humid areas, and in the semiarid tropics; they are formed mostly under forest vegetation, but also under grass savanna.  Extensive areas of Alfisols are found in the Mississippi and Ohio River valleys in the USA, through Central and Northern Europe into Russia, and in the South-central region of South America.

Alfisols generally show extensive profile development, with distinct argillic (clay) accumulations in the subsoil. Extensive leaching often produces a light-colored E horizon below the topsoil.



Generally fertile and productive, these soils typically have a high concentration of nutrient cations (Ca, Mg, K, and Na) and form in regions with sufficient moisture for plants for at least part of the year. Natural fertility and productive capacity of Alfisols is considered to be greater than that of Ultisols, but less than that of Mollisols.

Soil Order Key Characteristics U.S. Order Distribution Map Profile Examples

Alfisols

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

Alfisols

  • Found under forest and savanna vegetation
  • Clay accumulations in subsoil horizons
  • Often are leached below topsoil (E horizon)
  • Generally fertile, with high base saturation%.
  • Comparable in productivity to Mollisols and Ultisols.
  • Extensive in humid mid-latitudes
  • Extent of world ice-free land area: 10%

 

Further Details

 

Menfro Series

Missouri State Soil

USDA details

More information

All images courtesy of USDA-NRCS

 
Question 14:  What type of Native Vegetation is most commonly associated with formation of soils of the Alfisol Order?

A. Tallgrass prairie
B. Deciduous forest
C. Coniferous forest
D. Sage and scrub brush
E. Tropical rainforest


 
Question 15: What sequence of horizons could be expected to be found in a well-developed (mature), unplowed Alfisol soil profile?

A. A – B – C
B. O – B – C
C. O – A – E – B – C
D. A
EB C




 

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