Editing Vertisol (section)

==Classification==
In the USDA soil taxonomy,<ref name=ST/> vertisols are subdivided into:
* '''Aquerts''': Vertisols which are subdued aquic conditions for some time in most years and show [[redoximorphic features]] are grouped as Aquerts. The permeability is slowed because of the high clay content, and aquic conditions are likely to occur. When precipitation exceeds [[evapotranspiration]], ponding may occur. Under wet soil moisture conditions, iron and manganese are mobilized and reduced. Manganese may partly be responsible for the dark color of the soil profile.
* '''Cryerts''': They have a cryic soil temperature regime. Cryerts are most extensive in the grassland and forest-grassland transitions zones of the Canadian Prairies and at similar latitudes in Russia.
* '''Xererts''': These have a thermic, mesic, or frigid soil temperature regime. They show cracks open for at least 60 consecutive days during the summer, but closed for at least 60 consecutive days during the winter. Xererts are most extensive in the eastern Mediterranean and parts of California.
* '''Torrerts''': They have cracks closed for less than 60 consecutive days when the soil temperature at 50&nbsp;cm is above 8&nbsp;°C. These soils are not extensive in the U.S., and occur mostly in west Texas, New Mexico, Arizona, and South Dakota, but are the most extensive suborder of vertisols in Australia.
* '''Usterts''': They have cracks open for at least 90 cumulative days per year. Globally, this suborder is the most extensive of the vertisols order, encompassing the vertisols of the tropics and monsoonal climates in Australia, India, and Africa. In the U.S. the Usterts are common in Texas, Montana, Hawaii, and California.
* '''Uderts''': They have cracks open less than 90 cumulative days per year and less than 60 consecutive days during the summer. In some areas, cracks open only in drought years. Uderts are of small extent globally, being most abundant in [[Uruguay]] and eastern [[Argentina]], but also found in parts of [[Queensland]] and the "Black Belt" of [[Mississippi]] and [[Alabama]].

The WRB<ref name=WRB/> defines the diagnostic '''vertic horizon'''. It is usually a subsoil horizon and has at least 30% clay, shrink-swell cracks and [[soil structure|wedge-shaped aggregates]] and/or [[slickenside]]s.