2.3.1) FAO Soil Classification

The FAO (Food and Agriculture Organization) developed a supra-national classification (World Soil Classification), which conveys useful generalizations about the genesis of soils in relation to the interactive effects of the main soil-forming factors. It was first published in form of the Unesco Soil Map of the World (1974) (scale 1 : 5 M.).Like the Soil Taxonomy, it makes class separations on the basis of diagnostic horizons. Some of the descriptive terminology, in simplified form, has been adopted from Soil Taxonomy, but many of the traditional Great Soil Group names have been retained, as well as new names coined, which do not suffer in translation nor do they have different meanings in different countries (Table 2.3.1.1). The Soil Units (106) are mapped as Soil Associations, designated by the dominant soil unit,

with soil phases (additional soil properties, such as petric, saline, lithic, fragipan, stony),

with three textural classes (coarse, medium, and fine), and

three slope classes superimposed (level to gently undulating, rolling to hilly, and steeply dissected to mountainous)

Soil Units have been grouped on the basis of generally accepted principles of soil formation to form 26 World Classes. Although formulated on inferred pedogenic processes, such as gleying, salinization and lessivage, which have a bearing on soil use, the World Classes have been compiled so broadly and the total variation within each class is so large that their value in the prediction of land use is limited. The FAO soil map is far from ideal (very simple classification system, units are very broad) but it is the only truly international system, incorporating Soil Units used all over the world and most soils can be accomodated on the basis of their field descriptions. The FAO soil map is intended for mapping soils at a continental scale but not at local scale.

Table 2.3.1.1. FAO Soil Units and equivalent classification in Soil Taxonomy. 

References

FAO-UNESCO, 1978. "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.

FAO-UNESCO, 1987. "Soils of the World," Food and Agriculture Organization and United Nations Educational, Scientific and Cultural Organization, Elsevier Science Publishing Co. Inc., New York, NY.

Links

FAO Soil Classification

Global and National Soils and Terrain Digital Databases (SOTER): The aim of the SOTER project is to establish a World Soils and Terrain Database, containing digitized map units and their attribute data. Objectives: improved mapping and monitoring of changes of world soils and terrain resources, and global simulation modeling.

World Soil File for Global Climate Modeling

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