Verification and update of WRB-codes
The World Reference Base for soil resources (WRB) is the international reference base for soil classification (FAO et al., 1998) adopted by the International Union of Soil Sciences (IUSS) in 1998. WRB was elaborated to be a reference system that can be used world-wide. It is a twotier system of soil classification, with 30 Major Soil Groups (the 'Reference Base') and 121 uniquely defined qualifiers for specific soil characteristics (the 'WRB Classification System'). A set of prefixes is also established which may be added to the qualifier to indicate the depth of occurrence or the degree of expression of certain soil features. Several qualifiers and prefixes could be used depending on the degree of precision required for soil naming. It is the reason why WRB was chosen as reference system for the extension of the SGDBE to European New Independent States (Russia, Belarus, Moldova and Ukraine) and to Mediterranean countries.