fertilisers

• • manure is used as fertiliser
  • formulated fertilisers are better because they are:
  • widely available
  • easier to use
  • don't smell
  • have enough nutrients for crops to grow
• • the three main compounds in fertilisers are: nitrogen, phosphorus and potassium
  • NPK fertilisers contain all three compounds
  • fertilisers increase crop yield - crops grow faster and bigger
• • ammonia can be reacted with oxygen and water to make nitric acid
  • ammonia can be reacted with acids to make ammonium salts
  • ammonia and nitric acid react together to produce ammonia nitrate
  • it is a good fertiliser because it has nitrogen from two sources
• essential elements:

  • ammonium nitrate - nitrogen
  • ammonium sulfate - nitrogen
  • ammonium phospate - nitrogen, phosphorus
  • potassium nitrate - potassium, nitrogen
• • fertilisers must be soluble in water so they can be absorbed by the root hair cells
  • ammonia and nitrate ions are sources of soluble nitrogen
• • urea is used as a fertiliser and it provides nitrogen
• • potassium chloride and potassium sulfate are mined and can be used as fertilisers because they contain potassium ions
• • phosphate rock is mined
  • it cannot be used as a fertiliser because it is insoluble, so cannot be absorbed by root hair cells
• • phospate rock can be reacted with:
  • nitric acid - produces cacium nitrate and phosphoric acid (neutralised with ammonia to make ammonium phosphate)
  • sulfuric acid - single superphosphate (mixture of calcium sulfate and calcium phosphate)
  • phosphoric acid - triple superphosphate (calcium phosphate)