Biology Life in Soil

Soil forms a home for a multitude of living creatures, from moles and gophers to bacteria and viruses. Larger animals like earthworms, which aerate the soil, are assets to the garden; other animals, such as pocket gophers, may be pests. The most important organisms, however, are microscopic.

Soil microorganisms do most of the hard work of turning organic matter into humus that makes good soil structure and into nutrients that feed plants. Knowledgeable gardeners tip their hats to hardworking soil organisms by amending, mulching, and keeping soil moist to support and encourage the beneficial underground population.

Some organisms appear to have little or no effect on gardening soils; others can carry diseases harmful to plants. Many of these tiny organisms, however, perform vital roles in decomposing organic material and converting atmospheric nitrogen into nitrates. Also, they may be directly beneficial to plant growth processes in ways not yet well understood.

Microscopic soil dwellers include fungi (members of a plant group noted for lack of chlorophyll) that live on decaying animal and plant matter, bacteria (typically single-celled organisms) that live on fungi and the surface of soil particles, and protozoa (single-celled animals).