Soil Genesis and Development, Lesson 6 - Global Soil Resources and Distribution

Soil Moisture Regimes
(Images courtesy of the USDA-NRCS, edited by UNL)

Soil Moisture Regimes by Major Continent Areas
	North America Europe Asia South America Africa Australia
All images courtesy of USDA-NRCS.  Image editing courtesy of UNL.

Soil moisture regimes are defined based on the watertable level and the presence or absence of available water (water that can be used by plants).  All moisture regimes, except aquic, are based on regional climate.  Aquic moisture regimes are based on the length of the period that the soil was saturated. 

Soil moisture regimes are used as a soil classification criterion because they affect soil genesis (formation), affect the use and management of soils, and can be used to group soils with similar properties and morphology.

The soil moisture regime classes include:

1. Aquic (or Perudic):  Saturated with water long enough to cause oxygen depletion.
2. Udic:  Humid or subhumid climate.
3. Ustic:  Semiarid climate.
4. Aridic (or Torric):  Arid climate.
5. Xeric:  Mediterranean climate (moist, cool winters and dry, warm summers)
   (See Principles Lesson 3.2.2 for more information)