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The Nitrogen Cycle

The Nitrogen Cycle. The Nitrogen Cycle. Is the process in which Nitrogen (N 2 ) is converted between its various chemical forms . The Nitrogen Cycle. Is the process in which Nitrogen (N 2 ) is converted between its various chemical forms.

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The Nitrogen Cycle

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  1. The Nitrogen Cycle

  2. The Nitrogen Cycle • Is the process in which Nitrogen (N2) is converted between its various chemical forms.

  3. The Nitrogen Cycle • Is the process in which Nitrogen (N2) is converted between its various chemical forms. • The majority of the Earth’s atmosphere (78-80%) is Nitrogen, however (like carbon) atmospheric Nitrogen cannot be used straight from the air – it must be passed through the Nitrogen cycle first!

  4. The Nitrogen Cycle

  5. Why does it have to be cycled? • Atmospheric Nitrogen is mostly unusable by plants – Nitrogen needs to be ‘fixed’ in order to convert gaseous nitrogen into forms usable to plants.

  6. Why does it have to be cycled? • Atmospheric Nitrogen is mostly unusable by plants – Nitrogen needs to be ‘fixed’ in order to convert gaseous nitrogen into forms usable to plants. • Some fixation of nitrogen occurs as lightning strikes, but most is converted by free-living or symbiotic bacteria. For example Rhizobium, which live in the root nodules of legumes.

  7. Why does it have to be cycled? • Atmospheric Nitrogen is mostly unusable by plants – Nitrogen needs to be ‘fixed’ in order to convert gaseous nitrogen into forms usable to plants. • Some fixation of nitrogen occurs as lightning strikes, but most is converted by free-living or symbiotic bacteria. For example Rhizobium, which live in the root nodules of legumes. • This helps nutrient-poor soils become more enriched with Nitrogen.

  8. Other factors to the Nitrogen Cycle • When a plant or animal dies, the initial form of Nitrogen is organic. Bacteria (or sometimes fungi) convert the organic Nitrogen into ammonia (NH3).

  9. Other factors to the Nitrogen Cycle • When a plant or animal dies, the initial form of Nitrogen is organic. Bacteria (or sometimes fungi) convert the organic Nitrogen into ammonia (NH3). • For ammonia to be converted to Nitrate, it needs to be converted to Nitrite (NO-2) first, and it does this through nitrifying bacteria. Now, Nitrate (NO-3) can be used by plants.

  10. Other factors to the Nitrogen Cycle • When a plant or animal dies, the initial form of Nitrogen is organic. Bacteria (or sometimes fungi) convert the organic Nitrogen into ammonia (NH3). • For ammonia to be converted to Nitrate, it needs to be converted to Nitrite (NO-2) first, and it does this through nitrifying bacteria. Now, Nitrate (NO-3) can be used by plants. • Denitrification is the reduction of nitrates back into the largely inert nitrogen gas (N2), completing the nitrogen cycle. This process is performed by bacterial species.

  11. The Nitrogen Cycle

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