SOILS AND WATER - World Food: Production and Use - page 320

Figure 9.4. USDA world soil regions. (Courtesy of U.S. Department of Agriculture, Natural
Resources Conservation Service, Soil Survey Division, World Soil Resources, Washington, D.C.
http: // soils.usda.gov / use / worldsoils.mapindex / .)

If the textural name, percentage of sand, silt, and clay in a soil is known, it can be
related back to specific percentages of sand, silt, and clay. These are given in a textural
triangle shown in Figure 9.5. The names are easy to follow in that the word sand or
sandy indicates a large percentage of sand in the soil. The same is true for silt and

T A B L E 9.4. Partial Comparison of USDA and FAO Soil Classification Schemes

USDA Classification FAO Classification

Inceptisols Cambisols, Andisols, Rankers

Entisol Arenosols, Fluvisols, Regosols

Ultisols Acrisols

Histosols Histosols

Mollisols Chernozems, Greyzems, Kastanozems,

Phaeozems, Rendzinas

Oxisols Ferrasols

Alfisols Luvisols

Ultisols/Alfisols Nitrosols

Vertisols Vertisols

Aridisols Xerososls, Yermosols

Spodosols Podzols

Lithic subgroups Lithosols, Solonchaks (salt), Solonetz (sodium)

Planosols a No correspondence

a Have a bleached, temporarily water-saturated topsoil on a slowly permeable subsoil.
Sources:FAO-UNESCO.Report on the Agro-Ecological Zone Project, Food and Agriculture Organization and
United Nations Educational, Scientific and Cultural Organization, World Soil Resources Report 48, Rome,
Italy, 1978. FAO-UNESCO. Soils of the World, Food and Agriculture Organization and United Nations Edu-
cational, Scientific and Cultural Organization, Elsevier Science, New York, 1987. See also p. 321.