6.10 - Soil Moisture Regimes
Worldwide soil moisture regimes map. (Images courtesy of the USDA-NRCS, edited by UNL)
Worldwide soil moisture regimes map by continent. (Images courtesy of the USDA-NRCS, edited by UNL)
Soil Moisture Regimes - Descriptions
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:
- Aquic (or Perudic): Saturated with water long enough to cause oxygen depletion.
- Udic: Humid or subhumid climate.
- Ustic: Semiarid climate.
- Aridic (or Torric): Arid climate.
- Xeric: Mediterranean climate (moist, cool winters and dry, warm summers)
Management considerations vary based on different moisture regimes. Soils with an aridic (torris) moisture regime require irrigation to be used for crops. Soils with a ustic moisture regime can grow rain-fed crops, but moisture will be limited during some of the growing season. Soils with a udic moisture regime have sufficient moisture for crops. Crops may be grown in the udic moisture regime without irrigation, but irrigation is needed for crops in most years in an ustic moisture regime. Soils with an aquic (perudic) moisture regime need artificial drainage for most cropping practices.