NPK Fertilisers

• Formulated fertilisers are better than manure as they are more widely available, easier to use, do not smell and have the perfect amount of nutrients plants need to grow.Plants need nitrogen, phosphorous and potassium.Elements can go missing from the soil is they are used by a previous crop.Fertilisers replace these missing elements or provide more of them. They increase crop yield and make them grow faster and bigger.
• NPK fertilisers are formulations containing salt of Nitrogen, Phosphorous and Potassium.

  NPK fertilisers are made of compounds which contain all three elements.

  With the right mix of nutrients, crop growth will be maximised, yields will be high and farmers will have lots to sell.

  For example, Nitrogen allows a plant to make plant proteins, allowing them to grow faster and increase productivity.
• Ammonia is used to produce nitrogen-containing compounds.

  Ammonia can be reacted with oxygen and water in a series of reactions to get nitric acid.

  You can react ammonia with acids, including nitric acid, to get ammonium salts.

  Ammonia and nitric acid react together to produce ammonium nitrate.

  Ammonium nitrate is an especially good fertiliser as it has nitrogen from two sources.
• How fertilisers are made in industry

  • Reaction is carried out in giant vats, at high concentrations, resulting in a very exothermic reaction.
  • Heat released is used to evaporate water from the mixture and make a very concentrated product.
• How fertilisers are made in the lab

  Carried out at a much smaller scale by titration or crystallisation.

  Reactants are at much lower concentrations so less heat is produced.

  After titration, the mixture needs to be crystallised.

  Crystallisation is not used in industry because its very slow.
• Potassium chloride and potassium sulfate are mined so can be used as a source of potassium.

  Phosphate rock is mined but phosphate salts in the rocks are insoluble so the plant cannot directly absorb them and use them as nutrients.

  Reacting phosphate rock with a number of different types of acids produces soluble phosphates.
• Phosphate Rock Reactions

  Reaction with Nitric Acid produced phosphoric acid and calcium nitrate.

  Reaction with sulfuric acid produces calcium sulfate and calcium phosphate. (single superphosphate)

  Reaction with phosphoric acid only produces calcium phosphate. (tripe superphosphate).