The Nitrogen Cycle

• whats the percentage of nitrogen in the air

  78%
• what 2 elements is ammonia made from

  hydrogen + nitrogen
• why can't nitrogen be used directly by plants or animals

  as it's unreactive
• what is nitrogen essential for

  • formation of amino acids -> forms proteins -> growth
• state 2 ways nitrogen fixation can occur

  • lightening
  • nitrogen-fixing bacteria
• what does nitrogen in the air have to first be turned into

  nitrates
• what is nitrogen fixation

  process of turning N2 from air into nitrogen-containing ions in the soil
• how is lightening a way nitrogen-fixation occurs

  • large amount of energy released when lightening strikes
  • causes nitrogen in the air to react with oxygen
  • produces nitrates
• how is nitrogen-fixing bacteria a way for nitrogen-fixation to occur

  • found in soil + roots of some plants in parts called NODULES
• name the 4 different types of bacteria involved in the nitrogen cycle

  • decomposers
  • nitrifying bacteria
  • nitrogen fixing bacteria
  • dentrifying bacteria
• name 2 places you can find nitrogen-fixing bacteria

  soil + roots of some plants in nodules
• describe how nitrogen is passed along a food chain

  • plants absorb through roots
• describe the role of decomposers in the nitrogen cycle

  • decompose urea + proteins -> ammonia
  • forming ammonium ions in solutions
• describe the role of nitrifying bacteria in the nitrogen cycle

  turns ammonia -> decaying matter -> nitrites -> nitrates
• what do denitrifying bacteria do

  turns nitrates back into nitrogen gas
• describe how nitrogen is passed along a food chain

  • plants absorb through roots
• state 2 ways farmers can increase the amount of nitrates in the soil

  • using fertilisers + crop rotation
• how can crops increase the nitrate content + fertility of the soil

  • farmers grow crops like peas + beans
  • forms nitrates
  • as they have nitrogen-fixing bacteria in the roots
• what do crop plants do

  takes in the nitrate + use it to make proteins for growth
• what is crop rotation

  • growing different crops each year in a cycle
• describe how fertilisers can be used to increase the concentration of nitrates in the soil

  • natural fertilisers provide source of nitrate -> increase crop yield
  • expensive artificial fertilisers like ammonium nitrate applied to fields
• what are some examples of natural fertilisers

  manure/compost
• what is an example of expensive artificial fertilisers

  ammonium nitrate
• describe the process of crop rotation

  • rotation of plants containing nitrogen fixing bacteria
  • leads to a buildup of nitrates
  • helps grow target plants
• explain how crop rotation increases the concentration of nitrates in the soil

  • nitrogen-fixing bacteria turns atmospheric N2 -> nitrates/ammonia
  • which can be used for other crops for protein
• what can an extreme buildup of nitrates lead to

  eutrophication