SOTER-based soil parameter estimates (SOTWIS) for Southern Africa

This harmonized set of soil parameter estimates for Southern Africa has been derived from the 1:2M scale Soil and Terrain Database for Southern Africa (SOTERSAF ver. 1.0) and ISRIC-WISE soil profile database. The land surface of Southern Africa has been characterized using 4022 unique SOTER units, corresponding with 6099 polygons. The major soils have been described using 941 profiles, selected by national soil experts as being representative for these units. The associated soil analytical data have been derived from soil survey reports. These sources seldom hold all the physical and chemical attributes ideally required by SOTER. Gaps in the measured soil profile data have been filled using a step-wise procedure that uses taxonomy-based pedotransfer rules, based on some 9600 soil profiles held in the WISE2 database. Parameter estimates are presented by soil unit for fixed depth intervals of 0.2 m to 1 m depth for: organic carbon, total nitrogen, pH(H2O), CECsoil, CECclay, base saturation, effective CEC, aluminium saturation, CaCO3 content, gypsum content, exchangeable sodium percentage (ESP), electrical conductivity of saturated paste (ECe), bulk density, content of sand, silt and clay, content of coarse fragments (less than 2 mm), and available water capacity (-33 to -1500 kPa). These attributes have been identified as being useful for agro-ecological zoning, land evaluation, crop growth simulation, modelling of soil carbon stocks and change, and analyses of global environmental change. The current parameter estimates should be seen as best estimates based on the current selection of soil profiles and data clustering procedure. Taxotransfer rules have been flagged to provide an indication of the possible confidence in the derived data. Results are presented as summary files and have been linked to the 1:2M scale SOTERSAF map in a GIS, through the unique SOTER-unit code.