Stages of Nitrogen Cycle

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  • The Nitrogen Cycle
    • 1. Nitrogen Fixation
      • Nitrogen gas in the atmosphere is turned into ammonia by bacteria. The ammonia can then be used by plants.
      • The bacteria used is found inside root nodules of leguminous plants.
      • They form a mutualistic relationship with the plants - providing the plant with nitrogen compounds and the plant provides them with carbohydrates.
    • 2. Ammonification
      • Nitrogen compounds from dead organisms are turned into ammonium compounds by decomposers
      • Animal waste (urine and faeces) also contains nitrogen compounds. These are also turned into ammonium compounds by decomposers.
    • 3. Nitrification
      • When ammonium compounds in the soil are changed into nitrogen compounds that can then be used by plants.
      • First nitrifying bacteria change ammonium compounds into nitrites.
      • Then other nitrifying bacteria change nitrites into nitrates.
    • 4. Denitrification
      • Nitrates in the soil are converted into nitrogen gas by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas.
      • This happens under anaerobic conditions e.g. In waterlogged soils.


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