Global Soil Health Indicators and Assessment
Soil Health Indicators evaluate how well soil functions since soil function often cannot be directly measured. Measuring soil quality is an exercise in identifying soil properties that are responsive to management, affect or correlate with environmental outcomes, and are capable of being precisely measured within certain technical and economic constraints. There are three main categories of soil indicators: chemical, physical and biological. Soil carbon, transcends all three indicator categories and has the most widely recognized influence on soil quality as it is linked to all soil functions.
The status of soil health can be determined in two different ways. One is to determine an absolute rating for soil health that considers the soil in function of its deviation of an ideal soil with ideal properties (deep, fertile, well managed, having an adequate water supply, etc.), whatever the land use. The other option, more in line with the definition of soil degradation, considers a relative rating that depends on the suitability of the soil for its actual use only. As an example, a shallow slightly acid soil may be perfect for the pine forest occupying it, meaning the relative soil health is high, but would be considered as having a low marginal soil health in absolute terms because the alternatives using it for cropping for instance would be extremely limited.
A number of global soil health indicators are contained in the Global Land Degradation Information System (GLADIS) and the Status of the World's Soil Resources report (SWSR).