The Nitrogen Cycle

• Nitrogen cycle

  1. atmospheric nitrogen
  2. nitrogen fixation
  3. nitrogen in plants
  4. nitrogen in herbivores
  5. nitrogen in carnivores
  6. decomposition and ammonification by saprobionts
  7. nitrification by nitrifying aerobic bacteria
  8. denitrification by anaerobic denitrifying bacteria
• Nitrogen fixation is the process that causes nitrogen molecules found in the atmosphere to break apart so the nitrogen atoms can combine with other atoms
• Nitrogen fixation can occur by atmosphere fixation such as lightning strikes, industrial fixation or biological fixation by nitrogen-fixing bacteria
• Biological fixation reduces atmospheric nitrogen with hydrogen, and this is catalysed by nitrogenase in anaerobic conditions. This is carried out by free living bacteria or mutualistic bacteria
• Ammonification is the production of ammonia from organic ammonium containing compounds
• Nitrification is when aerobic nitrifying bacteria oxidise ammonium ions to form nitrate ions. Another group of nitrifying bacteria oxidise nitrite ions to nitrate ions.
• To improve productivity, soil is kept well aerated so that there is a lot of space for aerobic nitrifying bacteria, and well drained to maximise air spaces
• Denitrification is when anaerobic denitrifying bacteria use nitrate ions as an alternative to oxygen and reduce it to nitrogen gas