7.14 - Fertilisers

Fertilisers

• Plants need mineral ions from the soil to grow properly:
  • Nitrogen - For making proteins
  • Phosphorus
  • Potassium
• When a crop grows, it takes these mineral ions out of the soil, leaving the soil short of them for the next crop.
• Farmers add fertiliser to replace the missing mineral ions, or to provide extra - this boosts plant growth and so raises the crop yield.

Natural and artificial fertilisers

• Natural - Such as farmyard manure, slurry or compost. They release nutrients slowly and improve the soil.
• Artificial - Made industrially and usually rich in nitrogen, phosphorus and potassium (NPK). They're easy to apply and their mineral content is easy to measure accurately.

Problems caused by fertilisers

1. If too much fertiliser is applied and it rains, the soluble mineral ions are easily washed off the fields.
2. They leach into rivers and lakes, where the excess nutrients can lead to the death of aquatic organisms.