Interest in soil quality and health has grown with awareness that soil is central to the cycle of life on earth. Soils support the growth of plants and microorganisms, regulate the flow and storage of water in the biosphere, and serve as a primary interface with the global environment affecting quality of both the water we drink and the air we breathe. The thin layer of soil covering the Earth’s surface represents the difference between survival and extinction for most terrestrial life. One tablespoon of fertile soil contains up to 9 billion microorganisms, 1 and ½ times the human population of the earth. Soil health (quality) has been broadly defined as the capacity of a living soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health (Doran et al., 1996).