Though there is no direct geographica; equivalence between Arisdisols and Arid Zone soils, it is useful to obtain an impression of the definition and extent of desertic regions. A comparison is made between the criteria used by Unesco in its "Arid Zone research"programme; those used by Soil Taxonomy and Newhall-Van Wambeke as regards "aridic moisture regime"; and the ones of FAO in its "agro-ecological zones" project.
Soils in desertic areas, wheter Aridisols or others, have commonly specific features, which are described and denominated. The reasons for occurence of Aridisols outside the desertic areas are explaine; ....
(Presented at tte Fourth International Soil Correlation Meeting (ISCOM), October 1987, Lubbock, TX USA