Nitrogen cycle

• Ammonification:

  • production of ammonia from nitrogen-containing compounds
• Nitrification:

  • ammonium ions are oxidised to nitrite ions
  • nitrate ions are oxidised to nitrate ions
• Nitrogen fixation:

  • nitrogen gas is converted to nitrogen-containing compounds. Two types of bacteria carry this out:
  • free living nitrogen-fixing bacteria: reduce gaseous nitrogen to ammonia which is used to make amino acids
  • mutualistic nitrogen-fixing bacteria: obtain carbohydrates from the plant and plant obtains amono acids from the bacteria
• Denitrification:

  • when there is no oxygen in the soil fewer aerobic nitrifying and nitrogen fixing bacteria are found so there is an increase in anaerobic denitrifying bacteria
  • these convert soil nitrates to gaseous nitrogen, reducing the availability of nitrogen-containing compounds for plants