Nitrogen cycle

• Describe what ammonification is and how it occurs ?

  • Production of ammonia from nitrogen containing compounds
  • Saprobionts breakdown N containing compounds in faeces and dead organisms
  • They release ammonia into soil which then forms ammonium ions (NH3 —> NH4+)
• Describe what occurs in nitrification and how it occurs, also what conditions it requires ?

  • Ammonium ions are oxidised by nitrifying bacteria to form nitrite ions (NH3 —> NO2-)
  • Nitrite ions are oxidised by nitrifying bacteria to form nitrate ions (NO2- —> NO3-)
  • Requires oxygen so well aerated soil
• What are the 2 different types of nitrogen fixation ?

  Nitrogen ideation and mutualistic nitrogen fixation
• What occurs in nitrogen fixation ?

  Nitrogen gas is converted into nitrogen-containing compounds
• What are the 2 types of bacteria that can be involved in nitrogen fixation ?

  Free-living nitrogen-fixing bacteria, mutualistic nitrogen-fixing bacteria
• Apart from bacteria, how else can nitrogen fixation occur ?

  Lightning
• Describe how free-living nitrogen-fixing bacteria carry out nitrogen fixation ?

  Convert nitrogen gas to ammonia which they use to manufacture amino acids, release nitrogen-rich compounds when they die and decay
• Describe how mutualistic nitrogen-fixing bacteria carry out nitrogen fixation ?

  Live in nodules on roots of legumes, obtain carbs from plant and bacteria convert gaseous nitrogen into N compounds and amino acids which the plant uses
• Describe what denitrification is and how it occurs, also the conditions needed for it to occur ?

  • Waterlogged soil low O2 conc so there’s fewer aerobic nitrifying and nitrogen-fixing bacteria
  • More anaerobic denitrifying bacteria
  • They convert nitrates into gaseous nitrogen
  • Less nitrogen compounds for plants
• How can farmers avoid denitrification from occurring in soil ?

  Keep soil well aerated to avoid anaerobic conditions