Bacteria vary in their requirements for air, but most beneficial ones need some air to thrive. Bacteria need adequate calcium and a balance of micronutrients, which are essential to the enzymes used to perform their biochemical tasks.

Bacteria have a virtual monopoly on three basic soil processes that are vital to higher plants and crops: nitrif1cation, sulfur oxidation, and nitrogen fixation. Bacteria, which occur by the millions in each gram of soil, transform nitrogen and sulfur to a form usable by plants and crops. 

Nitrification. Nitrogen occurs in several different forms in the soil, but some of them are unavailable to plants and crops until they are transformed by bacteria. Soil organic matter, for example, holds nitrogen in the form of complex proteins. Bacteria and other organisms help to break down these proteins into the form of ammonium.

Sulfur Oxidation Sulfur undergoes similar chemical and biological transformations in the soil. Specialized bacteria turn organic sulfur compounds into sulfates, the form most usable by plants and crops.

Nitrogen Fixation. Nitrogen-fixing bacteria transform elemental nitrogen from the atmosphere into protein and eventually make it available to other organisms. To make synthetic fertilizers, humans imitate this process at a high energy costly burning tremendous amounts of natural gas to synthesize ammonia from atmospheric nitrogen. Some nitrogen-fixing bacteria live in symbiosis with leguminous plants, and other nitrogen-fixing bacteria live free in the soil. Bacteria transform nitrogen from the atmosphere into a form usable by plants and crops.

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