Fertilisers

• Natural fertilisers: consist of dead and decaying remains of plants and animals as well as plant waste
• Artificial fertilisers: mined from rocks and deposits blended together to make an appropriate balance of minerals for a particular crop
• How fertilisers increase productivity:

  • contain nitrogen which synthesises DNA and ATP
  • plants develop earlier, grow taller and have a larger leaf surface area
  • this increases photosynthesis rate and improves crop productivity
• Effects of nitrogen-containing fertilisers:

  • reduced species diversity
  • leaching
  • eutrophication
• Leaching = minerals are carried deep into the soil beyond the reach of the roots
• Eutrophication:

  Excessive growth of algae due to nitrogen ion concentration increase means light cant reach the lower depths of the water.

  Light becomes a limiting factor for the underwater plants growth, so the plants die.

  The amount of saprobiontic bacteria increase which need O2 for respiration, so there’s an increased demand for O2.

  Less O2 for aerobic organisms like fish so they die

  More anaerobic organisms appear due to less competition so they decompose the dead material releasing more nitrates and toxic wastes

  This makes the water putrid