Describing soils

World Reference Base for Soil Resources (WRB)

The World Reference Base for Soil Resources (WRB) is the international standard taxonomic soil classification system endorsed by the International Union of Soil Sciences (IUSS). It was developed by an international collaboration coordinated by ISRIC–World Soil Information and sponsored by the IUSS and the FAO.

The third edition, update 2015, is the currently valid WRB: Download main document (pdf, 2.3 MB).

The definitions in the WRB are based on field and laboratory data. The field data are according to the FAO Guidelines for Soil Description (FAO 2006) and the laboratory data according to the Procedures for Soil Analysis (Van Reeuwijk 2002). The latter are published by ISRIC–World Soil Information.

More information

See also our sections on: WRB structure | New Zealand and the WRB

Explore WRB teaching materials, including a video explaining how to describe and classify a soil according to FAO and WRB guidelines.