Nitrogen Cycle

This is the process through which nitrogen cycles between living organisms in any given environment. The process typically involves conversion of nitrogen gas into consumable compounds by both animals and plants (Vitousek et al, 1997). The process takes place in four distinctive stages namely: Nitrogen fixation; Ammonificaction; Nitrification; and Denitrification. During nitrogen fixation can take place in three different ways namely: biological fixation; industrial fixation; and atmospheric fixation. Through this process nitrogen molecules are broken apart to combine with hydrogen or oxygen to form ammonia and nitrogen oxides respectively (Vitousek et al, 1997). During ammonifaction, microorganisms break down complex amino acids from wastes and dead animals into ammonium and then to inorganic nitrogen which plants can easily absorb to make their own nutrients. The process is also known as decay. Nitrification involves formation of nitrites through combination of nitrogen with ammonia by the nitrifying bacteria. Plants can only absorb nitrates therefore nitrifying bacteria coverts nitrites into nitrates. Denitrification involves conversion of nitrates present in the soil into nitrogen gas that forms the component of the atmosphere and protects the earth form ultra-radiation (Galloway, J. N, 1998).

Human activities affect the nitrogen cycle in the following ways: Human beings use nitrogen fertilizers in their farms to increase productivity while ignoring the fact that excess nitrogen accelerates the process of nitrate leaching into water from the underground and also the denitrification process. Continued use of nitrogen fertilizers will cause flow of nitrogen into natural water bodies therefore causing eutrophication process. Forest burning in search of land for cultivation and combustion of fossil fuels are other human activities that have increased release of excess nitrogen in the atmosphere therefore disrupted nitrogen cycle (Galloway, J. N, 1998).


Galloway, J. N. (1998). The global nitrogen cycle: changes and consequences. Environmental pollution, 102(1), 15-24.


Vitousek, P. M., Aber, J. D., Howarth, R. W., Likens, G. E., Matson, P. A., Schindler, D. W., … & Tilman, D. G. (1997). Human alteration of the global nitrogen cycle: sources and consequences. Ecological applications, 7(3), 737-750.