SOTER-based soil property estimates for Central Africa

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A harmonized set of soil property estimates has been developed for Central Africa, comprising Burundi, the Democratic Republic of the Congo and Rwanda, using a 1:2 000 000 scale Soil and Terrain Database (SOTERCAF) and taxotransfer rules derived from profiles held in the WISE database. 

The land surface of Central Africa, comprising some 2.4 million km2, has been characterized using 244 unique SOTER units, corresponding with 504 polygons. Each SOTER unit may consist of up to 6 soil components; each of these has been characterized by a representative profile. The main soil units mapped for the region have been characterized using 167 real profiles, selected by soil experts as being regionally representative for these units; soil analytical data were derived from soil survey reports. These sources seldom hold all the physical and chemical attributes ideally required by SOTER. The primary database also includes 129 virtual profiles for which only the FAO classification is known; inherently, there are no measured data for these profiles. Gaps in the soil profile data have been filled using taxotransfer procedures; these were developed using soil profiles from WISE (n= 5672) having similar FAO soil unit names as those mapped for the SOTERCAF region.

Property estimates are presented by FAO soil unit for fixed depth intervals of 0.2 m to 1 m depth for: organic carbon, total nitrogen, C/N ratio, pH(water), 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 fragments > 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 (PDF), and analyses of global environmental change. 

Results are presented  tabular format (MS Access) and have been linked to the 1:2 000 000 scale SOTERCAF map using GIS (ArcGIS9.2).