A Handful of Soil

In soil, the role of all these living organisms is to break down raw materials and turn them into soil.

There is a theory put forth that for every naturally-occurring organic compound there is a microbe or enzyme system to decompose it.

Bacteria in Soil

Bacteria are plants that live in, among other places, the soil. Millions of bacteria exist in a gram of compost. They ‚”eat” organic substances, convert them to various enzymes, reproduce, die and add their tiny bodies to the organic soup.

In fact, bacteria in the soil do many things. Most importantly, they help decompose organic material and make the nutrients available to plant roots.Bacteria reproduce incredibly fast by dividing themselves in two. (One cell becomes two, two becomes four, etc.) One single-celled bacterium can produce 16 million more clones in one day.

Aerobic and Anaerobic Bacteria

There are two types of bacteria: aerobic and anaerobic. Aerobic bacteria have an oxygen-based metabolism. Anaerobic bacteria do not have oxygen-based metabolisms.

In any good soil, aerobic bacteria are necessary (and always present). They work quickly, decomposing organic material. Anaerobic bacteria work very slowly. Aerobic bacteria kills most pathogens and weed seeds in soil, while anaerobic bacteria does not. Additionally, anaerobic bacteria produces methane gas, a gas harmful to the environment.

Rhizobia in Soil

Plants require nitrogen to produce chlorophyll. However, they can’t take nitrogen from the air. Rhizobia are specialized bacteria that live near plant roots, taking in nitrogen, and transforming it into ammonium, which is a form of nitrogen that plants can absorb.

Protozoa in Soil

These are single-celled animals (as opposed to bacteria, which are plants). They are much larger than bacteria, but that doesn’t mean much. They’re still microscopic.

They feed on bacteria, other protozoans, fungi, and organic matter. The name comes from the combination of two Greek words: proto meaning first and zoia meaning animal but there is a lot of scientific information about protozoans, and some scientists believe that the difference between protozoa and bacteria is not that large. Included among protozoans are amoeba, rotifers and flagellates.

Protozoans are important because they help make mineral nutrients available to plants. For instance, plants need nitrogen to live. Bacteria contain large amounts of nitrogen. But they don’t release it readily. Protozoans need very little nitrogen. Protozoans eat bacteria. The nitrogen they don’t use, they release in the form of ammonium, which is then taken in easily by the roots of plants.

Interestingly, while protozoa eat bacteria by the billions, they actually encourage growth of bacteria. Many of the bacteria they eat are pathogens, so protozoa help prevent disease. They also are food for larger organisms. Billions of protozoa live in a handful of soil.

Fungi

Fungi can be tiny or large organisms, more primitive than plants. Most individual fungi in compost are microscopic or incredibly small and usually invisible. However, they grow in long strands, which, though small, can be seen by the naked eye. The strands resemble tiny spider webs or white roots and can grow several yards long.

Related articles include

Testing The Soil

Basic Soil Composition

Living Things in Soil