How does nitrifying bacteria increase soil fertility?
Nitrifying bacteria are not the same as nitrogen-fixing bacteria. Nitrogen fixation—the making N available to plants—is not to be confused with nitrification, which “designates the oxidation of ammonium salts to nitrites, then nitrates.” Nitrogen-fixing bacteria (Azotobacter in aerated soils, Clostridium in unaerated soils, and Rhizobium in legume plant roots) use N2 and bring it into the organic cycle. There is a direct correlation between the number of nitrogen-fixing organisms in the soil and the soil’s fertility.
