Fertilisers and eutrophication

Question 1

Name the 2 categories of fertiliser and state the purpose of using fertiliser

Answer 1

• Organic: Decaying organic matter & animal waste
• Inorganic: minerals from rocks, usually containing nitrogen, phosphorus, potassium
• To increase gross productivity for higher yield

Question 2

Outline 2 main environmental issues caused by the use of fertilisers

Answer 2

1) Leaching: Nitrates dissolve in rainwater and runoff into water sources
2) Eutrophication: Water source becomes putrid as a result of algal bloom

Question 3

What happens during eutrophication?

Answer 3

1) Aquatic plants grow exponentially since nitrate level is no longer a limiting factor
2) Algal bloom on water surface prevents light from reaching the bottom and plants die
3) Oxygen level decrease as population of aerogic saprobionts increases to decay dead matter, so fish die
4) Anaerobic organisms reproduce exponentially and produce toxic waste which makes water putrid

Question 4

How can the risk of eutrophication be reduced?

Answer 4

• Sewage treatment marshes on farms
• Pumping nutrient-enriched sediment out of water
• Using phosphate-free detergent