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www.nrcs.usda.gov/wps/portal/nrc...health/biology/

The online Soil Biology Primer is an introduction to the living component of soil and how it contributes to agricultural productivity and air and water quality. The Primer includes chapters describing the soil food web and its relationship to soil health and chapters about soil bacteria, fungi, protozoa, nematodes, arthropods, and earthworms.

The online Primer includes all of the text of the printed original, but not all of the images of the soil organisms. The full story of the soil food web is more easily understood with the help of the illustrations in the printed version.

Soil Biology Primer