In 1980, Mount St. Helens added a fresh layer of crop-nourishing ash to northwestern Montana s soils. Soil s living component is simply awesome. Several metric tons of such microorganisms may be strewn over a hectare. Professor S.A. Waksman, who signed his letters as soil microbiologist, was awarded the Nobel Prize in medicine after discovering in soils the microbes that produce the antibiotic streptomycin that cures tuberculosis. Although soil is not an organism it cannot multiply it can be said to have a metabolism, derived in part from soil organisms consuming oxygen from the soil air and giving off carbon dioxide.
Animals also churn and enrich soils with their burrowing and food gathering activities.
Moreover, the interface between the living and the non-living becomes blurred. Although no two soils are exactly alike, similar conditions do produce similar soils, making it possible to classify soils. The Soil Conservation Service adopted a new system of soil classification in 1965, which was formalized in 1974. The highest level recognized in this system is the order. Soil orders are divided into suborders, and thence into great groups and still more refined units.