The World Reference Base for Soil Resources (WRB) has come forth from an initiative of the Food and Agriculture Organization of the United Nations (FAO) and the United Nations Educational, Scientific and Cultural Organization (UNESCO), supported by the United Nations En/vironmental Programme (UNEP) and the International Union of Soil Sciences (IUSS).
WRB aims to establish an international reference base for soil classification. A Working Group of the International Union of Soil Sciences (IUSS) with collaboration of soil scientists from all over the world has worked out and tested proposals for WRB, leading to the publication of the World Reference Base for Soil Resources by FAO in 1998. It was endorsed by the IUSS as the union’s system of soil classification during the 16th World Congress of Soil Science in 1998 in Montpellier, France. The latest version of WRB was presented during the 18th World Congress of Soil Science (WCSS) at Philadelphia in 2006.
WRB is a two-tier system of soil classification, with 32 Major Soil Groups (the “Reference Base”) and over 120 uniquely defined qualifiers for specific soil characteristics (the “WRB Classification System”). Qualifiers (defined as prefixes and suffixes) are used to indicate the depth of occurrence or the degree of expression of certain soil features (see PDF). In 2010, Guidelines for constructing small-scale map legends using the WRB were published (PDF).
Dr. Otto Spaargaren, past WRB Chair and responsible for WRB-activities at ISRIC, went on full-retirement in 2009.