aridisol

Aridisols are soils of arid regions that experience limited leaching due to low precipitation. They are one of the 12 soil orders in the USDA Soil Taxonomy. A defining feature is the accumulation of carbonates, gypsum, or soluble salts in subsurface horizons, forming calcic, gypsic, or salic horizons. The surface horizons are typically pale with low organic matter and weak development, and the soils lack the argic horizons that characterize some other orders.

Moisture regime and horizon development: Aridisols generally have an aridic moisture regime, meaning moisture availability for plant use is limited for most of the year; in some cases a xeric or ustic regime can apply. The key diagnostic property is the subsurface accumulation of secondary materials such as carbonates, gypsum, or soluble salts, not strong clay illuviation. They often display surface crusts and low biological activity due to harsh conditions.

Distribution and formation: Aridisols occur in deserts and semiarid regions worldwide, including parts of North Africa, the Middle East, the southwestern United States, Central Asia, and Australia. They form on a variety of parent materials, frequently as wind-deposited loess or alluvial sediments, where high evaporation concentrates salts and carbonates in the lower horizons.

Uses and management: Because of low fertility and potential salinity or alkalinity, aridisols are usually not cultivated without irrigation and drainage. They are commonly used for rangeland, salt-tolerant crops, or mineral resources. Management practices may include controlled irrigation, drainage to prevent salinization, addition of organic matter, gypsum or lime amendments, and erosion control to maintain surface crusts.