It has been estimated that in one teaspoon of soil there are over 5 billion bacteria, 20 million fungi, and up to 1 million protozoa. Each works in the soil with plant life to promote essential life giving reactions.

Bacteria are single-celled organisms, one of the simplest forms of life known. They can multiply and divide at a very rapid rate with unlimited capacity to do so. In the top eight inches of soil there can be as much as 2.2 million pounds of bio-mass per acre. Bacteria are participants in all of the important bio-chemical transaction that take place in the soil to support agricultural plant life. They are responsible for such soil reactions as nitrogen fixation, sulfur oxidation, and also nitrification. These transformations are essential to plant life, providing plants with the necessary nutrients to continue in their life cycle. There are many conditions that encourage the growth of bacteria, and they are listed below.

1. Moisture:
a. Optimum moisture for most bacteria is the same as that of plants
b. The moisture content of soils will influence the oxygen supply.
2. Oxygen:
a. Some bacteria use oxygen (aerobic)
b. Some bacteria function without oxygen (anaerobic)
c. Some bacteria can be either aerobic or anaerobic (facultative)
d. Any one or all of these combinations can be present in the soil at the same time.
3. Temperature:
a. Bacterial activity is best between 65 and 85 degrees.
b. Bacterial can survive normal high and low variations in temperature.
4. Exchangeable Calcium and pH:
a. A pH between 6 & 8 and a high exchangeable rate of calcium is good for most bacteria.
b. These levels of pH and calcium determine the types of bacteria present in the soil.
5. Organic Matter:
a. Organic matter is used as a source of energy for the majority of soil bacteria.
b. There are certain bacteria that can obtain their own food (Autotrophic).