Once applied, fertilizer nitrogen is subject to the same transformations as other sources of nitrogen. Nitrogen Transformations Nitrogen exists in a number of chemical forms and undergoes chemical and biological reactions. The following transformation processes are numbered to coincide with Figure 1. 1. Organic nitrogen comprises over 95 percent of the nitrogen found in soil. Ammonium is not leached to a great extent.
Ammonium is available to plants.
Nitrate is the principle form of nitrogen used by plants. The nitrate form of nitrogen is a major concern in pollution. Soil microorganisms use nitrate and ammonium nitrogen when decomposing plant residues. This can be a major concern if crop residues are high in carbon relative to nitrogen. Examples are wheat straw, corn stalks and sawdust.