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The Nitrogen Cycle

Created: Thursday, 16 June 2011 10:54 | Published: Thursday, 16 June 2011 10:54 | Written by Super User | Print | Email

Nitrogen Fixation


The majority of Earth's atmosphere (approximately 78%) is nitrogen. The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. Nitrogen in the air becomes a part of biological matter mostly through the actions of bacteria and algae in a process known as nitrogen fixation.



Important Processes

•    Nitrogen Fixation
•    Mineralization
•    Nitrification
•    Denitrification
 



Why Nitrogen is important for all life?

Nitrogen is a component in all amino acids, is incorporated into proteins, and is present in the bases that make up nucleic acids, such as DNA and RNA. In plants, much of the nitrogen is used in chlorophyll molecules, which are essential for photosynthesis and further growth.


The nitrogen cycle is one of the most difficult of the cycles because there are so many important forms of nitrogen. In atmosphere it is about 78% and it is composed of two nitrogen atoms bound to each other. It is a non-reactive gas and to break up and combine with carbon or oxygen.



How the Nitrogen gas can be taken?

1.    Lightning provides enough energy to "burn" the nitrogen and fix it in the form of nitrate.
2.    Nitrogen fixing bacteria use special enzymes instead of the extreme amount of energy found in lightning to fix nitrogen.




Three forms of nitrogen-fixing bacteria:

1.    Free-living in the soil
2.    Symbiotic, mutualistic associations with the roots of bean plants and other legumes (rhizobial bacteria)
3.    Blue-green algae commonly in water.



How Nitrogen gets converted?


Five main processes cycle nitrogen Cycle:

1.    Nitrogen fixation
2.    Nitrogen uptake
3.    Nitrogen mineralization
4.    Nitrification
5.    Denitrification
 




•    After nitrogen is incorporated into organic matter, it is often converted back into inorganic nitrogen by mineralization. Most plants convert nitrate to amino acids.
•    Animals acquire amino acids when they eat plants or other animals.
•    Ammonification: When plants or animals die or release waste the nitrogen is returned to the soil in the output of the decomposers, is ammonia.
•    Ammonia is toxic, but the nitrite bacteria in the soil and in the water which take up ammonia and convert it to nitrite, which is nitrogen with two oxygens.
•    Nitrite is also bit toxic, but nitrate bacteria take nitrite and convert it to nitrate, which can be taken up by plants to continue the cycle.



The role of Human Beings:

Humans have significantly contributed to the transfer of nitrogen trace gases from Earth to the atmosphere, and from the land to aquatic systems. Human alterations to the global nitrogen cycle are most intense in developed countries and in Asia, where vehicle emissions and industrial agriculture are highest.



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