CGMS soil Suitability Criteria
Comparison of CGMS-rule based suitability maps from SGDBE version 3.2 with the land cover map
The cereal suitability map based on CGMS rules and SGDBE version 3.2 (see Annex 5, map 1) showed high percentages of suited land in all countries north of the Pyrenees and Alps up to the southern part of Sweden and Finland, and through Central Europe. Further in Eastern Europe, most territory of the former Soviet Union was uniformly very suitable, except in the southern parts of Ukraine and Russia, where according to the soil map a wide strip of alkaline soils stretches along the Black Sea to the northern tip of the Caspian Sea, and therefore rated as unsuited. Over most of the land between the Pyrenees and the Ural, this CGMS suitability map for cereals overestimates the cultivated lands. North of this zone, the map shows low suitability percentages in Norway, the northern parts of Sweden and Finland, and boreal Russia which corresponds with actual land use. In reality, in the Nordic zones the land use is more determined by climatic suitability than by soil suitability, but climatic factors are not discussed here. The suited area in England is relatively low compared to actual land cover. Here, the low proportion of suited land is related mainly to the wetness of the land. In southern Europe the proportion of suited land is much lower than elsewhere, due to the presence of sloping land. In CGMS it was assumed that 15 percent (as landscape characteristic) is the maximum slope for arable farming. In Spain and Italy, the pattern of suited land is still well correlated to the land cover map, but in Italy the suitability map underestimates the amount of cultivated land. The slope factor is especially important in Italy and the southern part of the Balkans (south of Sava- Donau rivers), but not Albania, according to the SGDBE 3.2.
When looking at the CGMS rule-based suitability maps of maize (see Annex 5, map 2) and root crops (see Annex 5, map 3), in many countries and regions a strong underestimation of agricultural area can be observed, and large differences between countries. This is due to the more severe criteria applied, specifically the additional requirements that suitable soils should have no gravelly or stony phase, which rule has a large impact on the extent of suited areas across Europe. Another difference is caused by the requirement that suitable soils should be at least 40 cm deep, where 20 cm was still suited for cereals. The CGMS maps for root crops and maize show much smaller suited areas than the cereal map, but not for all countries. Little or no differences between cereal and maize maps are for the former Soviet Union, Finland, Norway, England, Scotland, and Ireland. Relative large reductions in suited areas can be seen for Sweden, Wales, the southern half of Germany, Czech Republic, Austria, Italy, Albania, Spain, Portugal, and Turkey.
The difference between root crops and maize was in the requirement that root crops cannot be grown well in fine textured soils. This leads to some additional reduction in suited area for root crops as compared to maize, visible on the map for parts of Spain, France, England, Italy, Hungary and Romania, Albania, Greece and Turkey.