The concept of "land" is much wider than that of "soil". Land evaluation must be an integrative, multi-disciplinary exercise considering agronomic, social, economic and other ecosystem factors than soil (notably climate and water resources).
Soil Assessment focuses on the matching of the specific soil requirements of the land use with the properties of the soil. Most of soil assessments have been made for agricultural land uses and cropping systems, but the same principles could be applied for other applications.
Matching Land Use with Soil Quality
Studies have been made to correlate specific crop responses to a number of soil characteristics and soil qualities. The most comprehensive ones are those undertaken on a general level under ECOCROP and the more specific ones that are part of the Global Agro-ecological Zones web site. Both these approaches make use of standard soil parameters determined in routine soil surveys and are not based on rigorous testing but involve common sense and a certain arbitrary judgement. Another way of studying crop responses to soil factors is done by field tests and production functions that link in a statistical sound way a yield response to changes in a specific soil parameter. These results can then be introduced in a computer model that is able to generate responses for a wide range of soil conditions.