Entisols are soils of recent origin. The central concept is soils developed in unconsolidated parent material with usually no genetic horizons except an A horizon. All soils that do not fit into one of the other 11 orders are Entisols. Thus, they are characterized by great diversity, both in environmental setting and land use.
Many Entisols are found in steep, rocky settings. However, Entisols of large river valleys and associated shore deposits provide cropland and habitat for millions of people worldwide.
Globally, Entisols are the most extensive soil order, occupying ~16.2% of the Earth's ice-free land area. In the US, they occupy ~12.3% of the land area.
Aquents - Entisols with a water table at or near the surface for much of the year. Found in tidal marshes, on deltas on margins of lakes, on floodplains along streams, or in areas of wet sandy deposits. Many Aquents have bluish or grayish colors and redoximorphic features. They may have any temperature regime. Most are formed in recent sediments and support vegetation that tolerates permanent or periodic wetness.
Arents - Entisols that have been disturbed and contain fragments of diagnostic horizons that are not arranged in any discernable order. They have been deeply mixed by plowing, spading, or other methods of moving by humans. The soils retain fragments that can be identified as parts of a former spodic or argillic horizon, but the fragments do not form horizons themselves and are scattered through the soils and mixed with the materials of other horizons. Not extensive in the USA but area is increasing due to modern power machinery.
Psamments - very sandy Entisols. Sandy within all layers within the particle-sized control section. Some form in poorly graded (well sorted) sands on shifting or stablized sand dunes, in cover sands, or in sandy parent materials that were sorted in an earlier geologic cycle. Psamments occur under any climate without permafrost within 100 cm of the soil surface.
They can have any vegetation and are on surfaces of virtually any age from recent historic to Pliocene or older. A few Psamments formed in material weathered from sandstone or granitic bedrock. Psamments on old stable surfaces commonly consist of quartz sand.
Fluvents - alluvial Entisols commonly found on floodplains. Most are brownish to reddish soils that formed in recent water-deposited sediments, such as flood plains, fans, and deltas of rivers. Frequently flooded and stratification of materials is normal. Strata of clayey or loamy materials commonly have more organic carbon than the overlying, more sandy strata. The percentage of organic carbon of Holocene age decreases irregularly with increasing depth if the materials are stratified. Deposits generally are loamy and recent, the percentage of carbon in the deep layers is higher than in soils formed in parent materials other than alluvium. This difference in content of organic carbon is the basis for the definition variables.
Orthents - common Entisols that don't meet criteria of other suborders. Primarily Entisols on recent erosional surfaces. The erosion may be geologic or induced by mining, cultivation or other factors. Any former soil that was on the landscape has been completely removed or truncated so the diagnostic horizons for all other orders do not occur. Orthents occur in any climate and under any vegetation.