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Nitrogen Cycle Nitrogen Cycle Nitrogen Cycle

N2
atmosphere
lightning fixed Fertilizer Factory Fertilizer Factory
Denitrifying bacteria Denitrifying bacteria
Nitrates
Plants Bacteria
Decay Waste
Animals Ammonia
Decomposers

Bacteria in Nodules
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Nitrogen Cycle Explained

• Nitrogen is critically important to life, as it
  is a basic building block for amino acids and
  proteins.
• The chief reservoir of nitrogen is the
  atmosphere, which is about 78 nitrogen.
• Nitrogen gas in the atmosphere is composed of two
  nitrogen atoms bound to each other. Nitrogen is a
  fairly non-reactive gas it takes a lot of energy
  to get nitrogen gas to break up and combine with
  other elements, such as carbon or oxygen.

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Nitrogen Fixation

• Nitrogen gas can be taken from the atmosphere
  (fixed - reacted) in two basic ways.
• 1. Lightning provides enough energy to "burn" the
  nitrogen and fix it in the form of nitrate, NO3-.
  This process is duplicated in fertilizer
  factories to produce nitrogen fertilizers.
• 2. Nitrogen fixing bacteria use special enzymes
  to fix nitrogen (react the nitrogen with oxygen
  or hydrogen).

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The Cycle Begins

• 1. Most plants can take up nitrates and convert
  it to amino acids and then possibly proteins.
• 2. Animals acquire all of their amino acids when
  they eat plants (or other animals).
• 3. When plants or animals die (or release waste)
  the nitrogen is returned to the soil.
• 4. The nitrogen that is usually returned to the
  soil in animal wastes or in the output of the
  decomposers, is ammonia. Ammonia is rather toxic.
• 5. Nitrifying bacteria in soil or water convert
  ammonia to nitrates, which are taken up by plants
  to continue the cycle.