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Soil Food Web

The structure of soil is similar to that of a house made of bricks. To form bricks, straw and sand must stick together. Then the bricks are held together with mortar to form walls. The house has structure when the walls are arranged in certain patterns (Dr. Elaine Ingham of Soil Foodweb, Inc.).

In the soil food web, various organism groups perform the same function for soil structure. Bacteria glue the clays, silts and sands together into micro-aggregates – the bricks. The micro-aggregates are bound together by underground fungal vegetative growth, root hairs and roots – the mortar. Insects and earthworms make the structure of the rooms – the house. When all the organisms are present and active, roots and water move into and through the soil with ease.

A spoonful of healthy soil contains millions of different organisms, including bacteria, fungi, nematodes and protozoa, which:

• Keep disease-causing organisms in check
• Recycle and store nutrients and make them available to plants
• Provide a pathway through which air and water can pass

This intricate food web not only provides nutrients but also serves as a pollution control system. The many pathways created in the soil food web allow it to:

• Break down pesticide and hydrocarbon pollutants
• Bind heavy metals into immobile forms
• Convert soluble fertilizers into complex stored organic forms

This is known as biofiltration or bioremediation and is what keeps these pollutants from entering ground and surface waters. In healthy soil, this happens naturally. We can help the soil in our yards to do this by adding organic amendments, or compost, to the soil.

Additional information on soil biology and soil function can be obtained from the Soil Foodweb, Inc. (external) and the U.S. Department of Agriculture NRCS Soil Quality Institute (external).

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