SOTER-based soil parameter estimates (SOTWIS) for Brazil

This harmonized set of soil parameter estimates for Brazil. The 1:5M scale Soil and Terrain Database for Latin America and the Caribbean (FAO et al. 1998), provided the basis for the current study. The data set has been prepared for the project on Assessment of soil organic carbon stocks and change at national scale (GEF-SOC), which has the Brazilian Amazon as one of its four case ... study areas. The land surface of Brazil has been characterized using 299 unique SOTER units, corresponding with 839 polygons. The major soils have been described using 584 profiles, selected by national soil experts as being representative for these units. The associated soil analytical data have been derived from soil survey reports. Gaps in the measured soil profile data have been filled using a step-wise procedure which includes three main stages: (1) collating additional measured soil analytical data where available; (2) filling gaps using expert knowledge and common sense; (3) filling the remaining gaps using a scheme of taxotransfer rules. 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, aluminum 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 2mm), 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 can be linked to the 1:5 M scale SOTER map in a GIS, through the unique SOTER-unit code. The subset for the Amazon region, the Brazilian GEF-SOC case study area, has been clipped out of the national set using GIS. It includes 193 unique SOTER units, corresponding with 571 mapped polygons. The secondary data set is considered appropriate for studies at the national scale and regional scale (greater than1:5M). Correlation of soil analytical data, however, should be done more rigorously when more detailed scientific work is considered.