Ultisols comprise about 8% of
land area worldwide. They often have an
ochric or
umbric epipedon, but are typified by an
argillic or clay
horizon. The argillic horizon is low in base saturation (less than 35%). They normally pocess large "E" horizons wich are light colored due to the
eluviation of clay to the underlying argillic horizon. Ultisols tend to be acidic (less than 6.0) and low in plant nutrients.
Whereas entisols are young soils, ultisols are older and highly weathered. Worldwide, ultisols are found extensively in humid tropic regions, Africa and India, for example.
Ultisols are not as naturally productive as mollisolsor alfisols. They are found in areas of long growing seasons and respond well to fertilization, so with management can be quite productive.
The suborders of ultisols are:
- aquults (wet)
- humults (high humus)
- udults (humid)
- ustults (moist to dry)
- xerults (dry summers)