nitrogen/carbon/water cycles

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nitrogen cycle

nitrogen fixation, nitrification, assimiliation, ammonification, denitrification

nitrogen fixation

• N₂ is deposited by precipitation, nitrogen fixing bacteria combines the nitrogen with hydrogen

• Converts N₂ into NH₃ (ammonia) or NH₄ (ammonium)

• Generally done by bacteria, can also be done using lightning, fossil fuels, industrial processes

assimilation

• Most plants cannot use Ammonia

• Nitrifying bacteria converts Ammonia and Ammonium into NO₂ (nitrite) then NO₃ (nitrate)

ammmonification

• Different forms of nitrogen compounds absorbed by plants through soil & roots

  • Nitrate, nitrite, ammonia, ammonium

  • used to form proteins

decomposition

• Nitrogen re-enters soil through plant/animal deaths (decomposition) or waste

• Produces ammonia

denitrification

• Nitrogen goes back into the atmosphere; gets converted into N₂ and N₂O

• Occurs where there is a lack of oxygen  

• Micro organisms need oxygen - “denitrificating bacteria” break down NO₃ and use the oxygen