Classifications: International WRB and U.S. Soil Taxonomy - Major Soil Groups of the World - page 139

Table 4.14 Contd...

Aridisols ids Gypsisols (L. aridus = dry) Correspond to an arid (little

Calcisols water) climate whether the temperature is

high or not. But may be saturated with

water if saline. Possible diagnostic horizons:

Natric, Calcic, Petrocalcic, Gypsic,

Petrogypsic, Salic, Argillic, Duripan ( soils of

dry climates having accumulations of calcium

carbonate, gypsum or salts). Order introduced

in the 6th edition.

Ultisols ults Acrisols (L. ultimus = ultimate) Present signs of strong

development: argillic or kandic horizon or a

fragipan and has base saturation less than

35% on sum of cations ( soils on highly

weathered materials of the intertropical and

subtropical zones )

Mollisols olls For example: (L. mollis = soft ⇒ soils with soft humus)

Chernozems Present a surface mollic horizon with a base

saturation higher than 50% ( soils of the

grasslands and deciduous forests, calcareous or

non-calcareous )

Alfisols alfs Luvisol (coined term) Present an argillic or kandic or

natric horizon or a fragipan. Humid or

subhumid climate, base saturation > 30%,

slightly acid ( soils of humid climates marked by

argilluviation )

Inceptisols epts Leptosols (L. inceptum = beginning) Do not fall in the

categories presented above because they

are relatively thin and are not followed at

depth by calcic, petrocalcic, gypsic, petro-

gypsic, placic, duripan, fragipan, oxic, spo-

dic, sulphuric horizons. Contrarily, can have

horizons corresponding to immature soils:

cambic horizon or histic, mollic, plaggen,

umbric epipedon

Entisols ents Regosols (coined term) Do not fall in any of the

Arenosols preceding categories. No developed

diagnostic horizons, except ochric and

anthropic epipedons

The similarities between Soil Taxonomy and WRB are great, although
the taxa compared are not strictly equivalent in most cases. In the
various chapters of Part 2, we will come across certain problems in
classification. To mention here just a few major points:

￿ Soil Taxonomy has specifically distinguished the desert soils, the
Aridisols, so abundant in America;