You may not realize it, but when you walk on soil you are walking on billions of creatures. I found this information on a Purdue University Web site: “Soil is alive! In fact, a single shovel full of rich garden soil contains more species of organisms than can be found above ground in the entire Amazon rain forest.”

These microorganisms are so tiny that it takes a powerful lens to see them. They are working the soil, eating and recycling, which in turn feeds the plants that grow in that soil.

You can do an easy experiment to prove to yourself that the soil is teeming with creatures. Water a small area well, then layer it with newspaper (black ink only), cardboard, leaves, aged chicken manure, compost and perhaps some old lettuce or other soft plant material. Moisten each layer, then cover with black plastic, making sure all sides are secure. Don’t walk on this area, as compacting the soil will slow or even stop the process.

Peer under the plastic occasionally and you will be amazed by the activity taking place: the cardboard and paper will slowly disintegrate. You will see many more creatures than before, especially red wiggler worms, which love to eat decaying vegetation. Sow bugs and millipedes will be plentiful. But the most numerous workers are the ones you can’t see: the fungi, bacteria, protozoa and nematodes.

If you keep this spot covered long enough and keep your workers happy, the materials you layered will soon be transformed into rich, dark soil made up of worm and sow bug droppings. The soil will be well mixed because the creatures have been moving up and down in it. I have found red wigglers one foot deep in a raised bed.

Even soil that appears dry, compacted or frozen can still contain microorganisms waiting for the soil to become wet and warm again.

Plants thrive in soil that has been amended with compost. Compost is not fertilizer. It improves the texture of the soil by separating soil particles to allow air, water and microorganisms to move freely. When forests and open fields are left to do their own thing, soil creatures turn the fallen leaves and dead grass into humus. In cultivated landscapes like farms and gardens, we have to help the process along.

Worms are “shredders” in that they tear leaves and other organic material apart. Their work gives soil microbes more surface to feed on. All worms are not alike. Earthworms live in the top 12 inches of soil, and they sift soil through their gut, removing what they can use. In a way, they are turning the soil for you. Their castings, or droppings, are very high in nutrients that plants can use. Red wigglers eat decaying matter. Night crawlers eat the same material, but they come out at night.

Plant roots also aerate the soil, allowing water and nutrients to penetrate. At the same time, roots live in symbiosis with soil fungi and bacteria. The roots feed these microorganisms, and in turn the microorganisms improve the roots’ ability to absorb soil nutrients. The circle of life is right there under your feet.

To learn more about the world under our feet, take a look at Teaming with Microbes: A Gardener’s Guide to the Soil Food Web by Jeff Lowenfels and Wayne Lewis (Timber Press, 2006). It is written for the lay person and makes it easy to understand this natural cycle.

Napa County Master Gardeners are available to answer questions in person, by phone or on their Web site. Call 253-4221 or visit www.mastergardeners.

org for information.