The Nitrogen Cycle!

An overview of the different stages of this cycle :]

HideShow resource information

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.
1 of 4


  • 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.
2 of 4


  • 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
3 of 4


  • 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.
4 of 4



Condensed and quite useful. Tah.


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

Similar Biology resources:

See all Biology resources »See all Biological molecules, organic chemistry and biochemistry resources »