CGMS soil Suitability Criteria
Conclusion on the applicability of CGMS and ESCAPE-rule based suitability maps
In conclusion, we have shown that the CGMS-cereal rules and all ESCAPE rules lead to a general overestimation of the cultivated area, and the more severe CGMS-rules for maize and root crops to a general underestimation. In general there are large differences between countries, which are partly caused by lack of uniformity in the soil map and soil database. The application of new pedotransfer functions to estimate values of single soil properties per STU for use as suitability criterion is an important step to fill gaps in the database and towards more data consistency. The extension of the soil database with derived soil parameters makes it possible to formulate suitability criteria on the basis of specific parameters only, which is more precise than criteria based on lumped parameters as soil name or soil phase, which have a large internal variation. The old CGMS rules made direct use of soil names and soil phases as criteria.
The ESCAPE rules applied on the new SGDBE version 4.0 are more flexible and precise than the old CGMS rules. The refinement of the ESCAPE rules for the search of more plausible and accurate selections of suited soils calls for searching additional criteria. Because changes in suitability rules often lead to irregular responses across countries, it is important to follow a systematic approach in analyzing these differences. The necessary condition for choosing criteria is based on the matching of soil requirements of a given land use with the available soil properties. This process requires knowledge of reasonable land use specific sets of requirements, and of the available data sets in terms of geographic distribution of single soil factors and correlation between soil factors.