nitrogen cycle

• The nitrogen cycle is important for describing the role of bacteria in converting nitrogen from the atmosphere into a form that plants can absorb
• Nitrogen cycle


  1. Nitrogen from the air is converted to nitrates by nitrogen-fixing bacteria

  2. Plants absorb the nitrates and use them to make amino acids

  3. Animals eat the plants and release nitrogen in waste products and dead remains

  4. Decomposing bacteria convert the nitrogen to ammonia

  5. Nitrifying bacteria convert the ammonia to nitrates

  6. Denitrifying bacteria convert the nitrates back to nitrogen gas which returns to the air
• Nitrogen-fixing bacteria


  • Convert nitrogen from the air into nitrates in the soil
• Nitrifying bacteria


  • Convert ammonia to nitrates
• Denitrifying bacteria


  • Convert nitrates back to nitrogen gas which returns to the air
• Soil contains a high level of nitrates


  Crops grow faster
• Over time, the level of nitrate in the soil falls


  As crops absorb it and denitrifying bacteria convert it to nitrogen gas
• Farmers increase nitrate levels in soil

  1. Add fertilizers (animal manure or chemical fertilizers)

  2. Use crop rotation with nitrogen-fixing plants like peas, beans, or clover