The Soil Biology PrimerThe Primer includes units describing the soil food web and its relationship to soil health, and units about bacteria, fungi, protozoa, nematodes, arthropods, and earthworms. From the USDA, Natural Resources Conservation Service.
Chapter 1: THE SOIL FOOD WEB
Chapter 2: THE FOOD WEB & SOIL HEALTH
Chapter 3: BACTERIA
Chapter 4: SOIL FUNGI
Chapter 5: SOIL PROTOZOA
Chapter 6: NEMATODES
Chapter 7: ARTHROPODS
Chapter 8: EARTHWORMS
Bibliography with great references