This is the process in which
nitrogen is converted between its various chemical forms. The conversion can be
carried out, both in the form of biological and physical processes. The vital
processes in the completion of nitrogen cycle include fixation, nitrification,
denitrification and ammonification. The main component of the nitrogen cycle
starts with the element of nitrogen in the air. Two nitrogen oxides are found
in the air as a result of interactions with oxygen. Nitrogen only reacts with
oxygen in the presence of high temperatures and pressures found near lightning
flash and in combustion reactions in power plants or internal combustion
engines. Nitric oxide, NO, and nitrogen dioxide, NO2, are formed under these
conditions.
Nitrogen in the atmosphere becomes a
part of biological matter mostly through the actions of bacteria and algae in a
process known as nitrogen fixation.
Legume plants like clover, alfalfa, and soybeans form nodules on the roots
where nitrogen fixing bacteria takes nitrogen from the air and convert it into
ammonia, NH3. The ammonia is then transformed by other bacteria first into
nitrite ions, NO2-, and after which into nitrate ions, NO3-. Plants make use of
the nitrate ions as a nutrient or fertilizer for its growth.
Human activities such as the use of
artificial nitrogen fertilizers, fossil fuel combustion and the release of
nitrogen in waste-water have technically altered the global nitrogen cycle.
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Nitrogen cycle
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