Fertiliser

• A fertiliser is a substance that is added to soil to make it fertile
• Synthetic fertilisers are salts and tend to be ammonium salts and nitrate

  • e.g. ammonium nitrate and ammonium phosphate
• Fertilisers makes the soil fertile after it becomes worn out
• 3 main elements needed in fertilisers is

  • nitrogen
  • phosphorous
  • potassium
• Urea is a fertilizer made from ammonia using CO2 and a common liquid is formed

  • 2NH3 (aq) + CO2 (aq) → CO(NH2)2(aq) + H2
• NKP fertilisers contain nitrogen, potassium and phosphorus for improved plant growth

  • Nitrogen makes chlorophyll and protein and promotes healthy leaves
  • Potassium promotes growth and healthy fruit and flowers
  • Phosphorus promotes healthy roots
• Fertiliser compounds contain the following water-soluble ions:

  • Ammonium ions, NH4+ and nitrate ions, NO3-, are sources of soluble nitrogen
  • Phosphate ions, PO4^3- are a source of soluble phosphorus
  • Most common potassium compounds dissolve in water to produce potassium ions, K+
• Ammonium salts and nitrate salts are commonly used as fertilisers, including:

  • Ammonium nitrate, NH4NO3
  • Ammonium phosphate, (NH4)3PO4
  • Potassium nitrate, KNO3
• Different fertilisers contain different amounts of fertiliser compounds

  • So, each fertiliser contains different proportions of nitrogen, potassium and phosphorous
• You may be asked to select a compound or combination of compounds from a list which would be the most effective as a fertiliser

  • Look for the compound or combination of compounds that contain the most elements from nitrogen, phosphorous and potassium.