Global Soils
PHYSICAL GEOGRAPHY 101

Soil Orders

Soil profiles which are distinguished based on the presence or absence of soil horizons .
Diagnostic horizons are horizons within a profile that are unique or easily identified.
There are three groups of soil orders

Soil Group I

Well developed horizons.
Develop in areas where soil has had a long period of adjustment.
Generally have high base status
- high base status - rich in nutrients
- low bas status - poor in nutrients
7 orders - Oxisols, Ultisols, Vertisols, Alfisols, Spodosols, Mollisols, Aridisols

Soil Group II

Soils with a thick, organically rich upper layer.
1 order - Histosols
Commonly called peat or muck.
Forms in lakes/ponds that fill up with organic debris.

Soil Group III

Soils with poorly developed horizons or no horizons.
Recent accumulations of material.
Poorly developed horizons indicates that the soil formation process has only recently begun.
3 orders - Entisols, Inceptisols, Andesols

Additional Topics

One or both of the following topics may also be discussed in class:
Earthworms in Soil
Accelerated Soil Erosion in the United States

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