How to find a right soil profile for this grid cell?

For crop modeling researchers who are in need of finding soil profiles at regional-scale in Sub-Saharan Africa (SSA), this post gives a spatial dataset that delineates SSA into 588 units and corresponding soil profiles, based on the WISE v1.1 and HC27 soil profile databases.

The Harmonized World Soil Database (FAO/IIASA/ISRIC/ISSCAS/JRC, 2009) (HWSD) delineates Sub-Saharan Africa (SSA) with 6,870 soil mapping unit (SMU) polygons. In each mapping unit, the share and detailed properties of up to 9 soils are presented in the database. The HWSD is a great data source that harmonizes regional/country-basis soil datasets in a globally consistent method, yet some aspects of the database make the properties not directly usable for complex crop systems models such as DSSAT and APSIM (e.g., no rooting depth defined; soil reference depth is harmonized for 30 cm for topsoil and 100 cm for subsoil). Thus, for researchers who uses the complex models, HWSD can provide information on some key soil variables at regional scale, but not site-specific soil profiles that crop models use.

On the other hand, the global soil profile databases, such as the ISRIC WISE Global Soil Profile Dataset, provides site-specific soil profile information at very detailed level (and also converted to the crop model-compatible format), yet their distribution is not uniform.

By mashing-up the mapping unit-based HWSD and site-specific WISE on 5 arc-minute grids, using 5 key soil variables (soil type, texture, organic carbon content, pH, and water availability), we created a simple look-up table that shows the best-matching soil profiles and their shared in each grid cell in SSA. When no appropriate soil profile is found from the WISE 1.1 Soil Profile Dataset, the HC27 Generic Soil Profiles was used to find a proxy soil profile. Following maps showing (A) the boundaries of 6,870 soil mapping units of HWSD and 588 units after the mash-up/matching process.

  

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Citation

HarvestChoice, 2010. "Mapping Spatial Distribution of Soil Profiles." International Food Policy Research Institute, Washington, DC., and University of Minnesota, St. Paul, MN. Available online at http://harvestchoice.org/node/1434.

Dec 6, 2010