The World Reference Base for Soil Resources (WRB) hast two roots:
- the Legend of the Soil Map of the World
- the International Reference Base for Soil Classification (IRB)

The Food and Agriculture Organization of the United Nations (FAO) and the United Nations Educational, Scientific and Cultural Organization (UNESCO) produced the Soil Map of the World (1971-1981) at a scale of 1 : 5 million. This project was led by D.L. Bramão (1961-1968), L.D. Svindale (1968-1970) und R. Dudal (since 1970). The Soil Map of the World has 11 volumes. Volume 1 is the Legend. With this Legend, a new soil classification system was created, well known as the FAO system. It unites the soils of the world to 26 Soil Groups. In 1988, the Revised Legend was published with 28 Soil Groups. For the definitions, the Legends use diagnostic horizons, properties and materials. This principle is based on the ideas of G. Smith.


The International Reference Base for Soil Classification (IRB) was established in 1982 as a Working Group of the International Soil Science Society (ISSS - now IUSS: International Union of Soil Sciences) with E. Schlichting as chair. The Working Group presented a concept with 20 soil units. Whereas the FAO system was strongly related to land use, the IRB was more based on soil properties that reflect soil-forming processes.

In 1992, the decision was made to establish a soil classification system using the Soil Groups of the FAO system and underpinning them with the scientific structure of the IRB. This system should be called ‘World Reference Base for Soil Resources’ (WRB). At the World Congress of Soil Science in Acapulco in 1994, a WRB draft was presented and the WRB was established as an ISSS Working Group.

The first edition of WRB was published in 1998 with 30 Reference Soil Groups (RSGs). The second edition is from 2006 and comprises 32 RSGs. The second edition was only for naming soils. For creating map legends, an addendum was published in 2010.

The third edition of WRB was published in 2014. It has 32 RSGs and is a system for both naming soils and creating legends for soil maps. An update was published in 2015, which is the currently valid WRB.

The leading teams of the WRB Working Group were:

1994-1998:
Seppe Deckers (Belgium), chair
Otto Spaargaren (The Netherlands), vice-chair
Freddy Nachtergaele (Belgium, FAO), secretary

1998-2002:
Seppe Deckers (Belgium), chair
Otto Spaargaren (The Netherlands), vice-chair
Freddy Nachtergaele (Belgium, FAO), secretary

2002-2006:
Erika Michéli (Hungary), chair
Peter Schad (Germany), vice-chair
Otto Spaargaren (The Netherlands), secretary

2006-2010:
Otto Spaargaren (The Netherlands), chair
Peter Schad (Germany), vice-chair
Erika Michéli (Hungary), secretary

2010-2014:
Peter Schad (Germany), chair
Cornie van Huyssteen (South Africa), vice-chair
Erika Michéli (Hungary), secretary

since 2014, elected till 2018:
Peter Schad (Germany), chair
Cornie van Huyssteen (South Africa), vice-chair

Further reading:
Blume H-P, Schad P (2015): 90 years of soil classification of the IUSS. IUSS Bulletin 126, p. 38-45.