What You Will See

• Steve Baccon/Digital Vision/Getty Images
  
  Soil organisms can be divided into two groups: animals (fauna) and plants (flora). Macro-organisms are larger than 2.0 mm in diameter, meso-organisms are 0.2 to 2.0 mm in diameter and micro-organisms are less than 0.2 mm. Microorganisms' require the observer to use a magnifying glass or microscope. Scoop some garden soil with a trowel, and spread it out on a sheet of paper. Inspect the dirt for the presence of insects such as worms, beetles, ants, spiders, mites, centipedes and millipedes.
  
  

Under the Magnifying Glass

• BananaStock/BananaStock/Getty Images
  
  Soil can be examined at various degrees of magnification. Take a petri dish and layer it with agar. Take a sample of soil, spread it thinly over a glass microscope plate, then spread the sample over the agar. At 10x magnification; macrofauna, such as earthworms, beetles and ants are visible along with the structure of the mineral content of the soil.
  
  

Under the Microscope

• At 50x magnification, mesofauna (collembola, mites) become visible, as do particles of silt or sand-sized grains. Decomposing plant material will become visible. At 100x--200x magnification, microfauna -- such as single-cell protozoa, mites, nematodes -- silvery worm-like creatures, insect larva, rotifers -- can be seen. At 1000x magnification, bacteria, actinomycetes, fungi and even viruses are visible, as is mycorrhizae fungus, which helps plants absorb nutrients through their roots.
  
  

Trapping Arthropods

• Make a pitfall trap to catch large arthropods, by sinking a container such as a yogurt cup into the ground. Keep the rim level with the soil surface. Cover the container, to keep the rain out and pour in 1/2 inch of non-hazardous antifreeze to preserve the creatures. After a week, you should have soil creatures to view in your trap. For smaller arthropods, place a 1/4-inch rigid wire screen in the bottom of a funnel, made from the bottom of a plastic soda bottle. Half fill the funnel with soil, and suspend it over a cup with a bit of anti-freeze or ethyl alcohol in the bottom as a preservative. Position a light source a few inches over the soil to corral the organisms from the soil, into the cup. Leave the light on for 3 days to dry out the soil. Then pour the alcohol into a shallow dish. Use a magnifying glass to examine the organisms.