American West
Maps showing consequences of Aridity
A soils map of the United States created from the United Nations Food and Agriculture Organization digital soils map of the world. Soils are classified by their number of agronomic limiting factors. Soils with a high number of limiting factors are problematic and require remediation for agricultural production. The best soils for agriculture have no or few limiting factors.
(Spource: http://biology.usgs.gov/luhna/chap3.html)