Soil property maps of Africa at 250m
Over the period 2008–2014, the AfSIS project has compiled two soil profile data sets: the Africa Soil Profiles (legacy) database [Leenaars, 2014] and the AfSIS Sentinel Site (new soil samples) database [Vagen et al, 2010], jointly consisting of ca. 28 thousand sampling locations.
Using these soil point observations and an extensive collection of global (SoilGrids1km) and local (African continent) environmental covariates, ISRIC - World Soil Information, in collaboration with The Earth Institute, Columbia University, World Agroforestry Centre, Nairobi and the International Center for Tropical Agriculture (CIAT), have produced (February 2015) predictions of soil properties — organic carbon, pH, sand, silt and clay fractions, coarse fragments, bulk density, cation-exchange capacity, total nitrogen, exchangeable acidity, Al content, and exchangeable bases (Ca, K, Mg, Na) — for the whole African continent at 250 m spatial resolution at two or six standard soil depths.
The predictions are obtained using an automated mapping framework (3D regression-kriging based on random forests).