The soil property layer is a product of the Global Soil Data Task, coordinated by the Data and Information System (DIS) of the International Geosphere-Biosphere Programme. Specific purpose derived data sets for major classes of global soils along with spatial data on specific soil properties are generated using a supplied proprietary software called SoilData. The statistical properties are derived from the WISE pedon-database produced by the International Soil Reference and Information Center (ISRIC) (Batjes, 1995) and classified by the FAO-Unesco Digital Soil Map of the World (DSMW) (FAO, 1995). The WISE-database is linked to the DSMW, providing a basis for generating statistics on soil properties. Surface maps are created for nine different properties at two soil horizons. The properties include Alpha, BulkDens, Ks, Sand, Silt, ThetaR, ThetaS, and WaterN. The two soil horizons are 0-30cm and 30-100cm.
Soil texture classes are used to estimate field capacity, wilting point, and available water capacity (field minus wilting point) using the texture-based methods of Saxton et al (1986). Rooting depth (which determines to what depth vegetation can access water) was specified as a function of soil texture and vegetation type (sensu Nepstad et al. 1994).