Soil Organisms
The number of organism that live in the soil are countless. Microorganisms such as bacteria and fungi, algae, microscopic worms and protozoa may number in the millions in a single teaspoon of fertile soil. Other organisms such as plant roots, insects, earthworms, moles, snakes, and groundhogs are other organisms that inhabit the soil at least on a part time basis. Most numerous are the bacteria. Scientists have identified about 170,000 species of soil organisms but many remain to be identified and the roles of soil organisms are largely unknown due to the difficulty of studying them in their natural habitat.
Soil organisms are invaluable to the health of soil. They maintain soil fertility by breaking down and cycling organic material. They prevent soil erosion. They breakdown many toxic materials and cleanse water.
One of the most familiar soil dwellers is the earthworm. Earthworms tunnel through soil, aerating it, and their waste (called castings) add rich organic material to the soil. Ants also live in the soil in enormous numbers. Their tunnels and chambers also aerate the soil. Food that ants bring back to their nests may go uneaten and increase the organic material in the soil. Ants also bring in seeds which aids in plant reproduction.
There is an important symbiotic relationship in the soil that occurs between the roots of vascular plants and fungi. These associations are called mycorrhizae. The thread-like body of the fungus (the mycelium) excretes a digestive enzyme that breaks down matter in the soil. It can then absorb those nutrients and some are transferred to the partner plant. In turn, the plant provides the fungus with sugars that it produces through photosynthesis.
In the photos below, you can see on the left, what the (white) fungus looks like attached to a root hair. On the right, you can see an illustration showing how the fungi penetrate the root hairs. This is how they deliver nutrients to the plant and in turn get sugars from photosynthesis. Some fungi form large spores, easily seen in plant roots (image at the bottom).
Soil organisms are invaluable to the health of soil. They maintain soil fertility by breaking down and cycling organic material. They prevent soil erosion. They breakdown many toxic materials and cleanse water.
One of the most familiar soil dwellers is the earthworm. Earthworms tunnel through soil, aerating it, and their waste (called castings) add rich organic material to the soil. Ants also live in the soil in enormous numbers. Their tunnels and chambers also aerate the soil. Food that ants bring back to their nests may go uneaten and increase the organic material in the soil. Ants also bring in seeds which aids in plant reproduction.
There is an important symbiotic relationship in the soil that occurs between the roots of vascular plants and fungi. These associations are called mycorrhizae. The thread-like body of the fungus (the mycelium) excretes a digestive enzyme that breaks down matter in the soil. It can then absorb those nutrients and some are transferred to the partner plant. In turn, the plant provides the fungus with sugars that it produces through photosynthesis.
In the photos below, you can see on the left, what the (white) fungus looks like attached to a root hair. On the right, you can see an illustration showing how the fungi penetrate the root hairs. This is how they deliver nutrients to the plant and in turn get sugars from photosynthesis. Some fungi form large spores, easily seen in plant roots (image at the bottom).