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.
Key Characteristics: 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%