Importance of Soil Bacteria

One tsp. of soil can contain as many as 1 billion bacteria, notes the U.S. Department of Agriculture. These bacteria play an important part in supplying nutrients for plants and keeping your garden healthy.

Types

• Some of the most important soil bacteria fall into several groups -- the actinomycetes, which digest tough fibers like chitin and cellulose; nitrogen-fixing bacteria, which turn atmospheric nitrogen into ammonia; nitrifying bacteria, which change ammonia into nitrates; and denitrifying bacteria, which convert nitrates into atmospheric nitrogen.

Function

• When plants or animals die, bacteria like actinomycetes and other organisms called decomposers break down and digest their remains. These decomposers return the nutrients stored in the tissues of living organisms back into the soil so plants can use them.

Effects

• Nitrogen-fixing and nitrifying bacteria fulfill an even more important role than the decomposers. All living organisms need nitrogen, but atmospheric nitrogen is too nonreactive for plants and animals to capture and make use of it. Nitrogen-fixers and nitrifiers convert atmospheric nitrogen into forms plants can use; without the nitrogen-fixers, plants couldn't survive. Denitrifying bacteria return some of the nitrates back to the atmosphere.