The Nitrogen Cycle!

An overview of the different stages of this cycle :]

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Nitrogen Fixing

  • This is where nitrogen gas from the atmosphere is turned into ammonia by nitrogen-fixing bacteria (called Rhizobium). The ammonia can then be utilised by plants.
  • Rhizobium are found inside root nodules of leguminous plants e.g peas.
  • The form a symbiotic relationship with the plants, they provide the plant with nitrogen compounds and the plant provides them with carbohydrates.
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  • This is where nitrogen compounds from dead organisms (detritus) are turned into ammonium compounds by decomposers.
  • Animal waste (urine and faeces) also contain nitrogen compounds. These are also turned into ammonium compounds by decomposers.
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  • This is where ammonium compounds in the soil are changed into nitrogen compounds that can be used by plants.
  • First, nitrifying bacteria (Nitrosomonas) change ammonium compounds into nitrites.
  • Then, other nitrifying bacteria (Nitrobacter) change nitrites to nitrates.
  • Ammonium Compounds ---> Nitrites ---> Nitrates
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  • This is where nitrates in the soil are converted back into atmospheric nitrogen by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas.
  • This happens under anaerobic conditions (NO OXYGEN) e.g in waterlogged soils.
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Condensed and quite useful. Tah.



Excellent resource.. to the point without all the waffle. Thanks a bunch x

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