3.13 Eutrophication Flashcards
What is a fertiliser?
A substance that is applied to soil, in order to supply plants with nutrients.
Why do we need fertilisers?
- In agriculture, fertilisers are added to soils to replace lost nutrients.
- Crops take nutrients from the soil in order to grow. When crops are harvested, these nutrients are removed and do not return to the soil, as they would in a natural ecosystem.
- Nutrients are also lost when livestock or animal products are removed, because animals absorb nutrients from the plants that they eat. If livestock are removed for slaughter, these nutrients aren’t replaced through their urine, faeces or their remains when they die as they would be in a natural ecosystem.
NPK fertilisers (3)
Most fertilisers are made up of a mixture of nitrogen (N), phosphorus (P), and potassium (K) compounds. This is because these are the three main elements plants require from soil.
- Nitrogen
- Phosphorus
- Potassium
What are the 2 main processes that fertilisers can negatively impact waterways due to?
- Leaching
- Eutrophication
How does leaching occur?
Fertilisers don’t always stay in agricultural fields. Leaching occurs when nutrients in fertilisers are washed out of the soil by water. For example, by rain or irrigation systems. Leached nutrients often wash into waterways such as rivers and ponds, and this can result in eutrophication.
How can leaching become more likely and why?
When fertilisers provide plants with more nutrients than they can use; the excess inorganic ions are washed away.
What is eutrophication? (4)
Eutrophication is a process - it’s caused by excess nutrients that have leached into waterways.
- Mineral ions (e.g. nitrates) leach into lakes and rivers where they stimulate rapid growth of algae.
- The growth of algae on the water surface blocks light from reaching the plants below.
- The lack of light prevents the plants from photosynthesising enough, causing them to die.
Decomposers feed on the dead matter. The decomposers use oxygen to aerobically respire, so as the number of decomposers increases the oxygen in the water is depleted.
- The lack of oxygen in the water causes fish and other aerobic organisms to die.
What are the bacteria called that feed on the dead plant matter in the process of eutrophication?
Saprobiotic bacteria
What is the cause of eutrophication?
Excess nutrients in waterways.
During the process of eutrophication, what causes the algae in waterways to grow rapidly?
High levels of nutrients such as nitrates.
What is leaching?
Dissolved ions flowing through the soil into bodies of water.
What can reduce eutrophication?
Controlling the use of fertiliser and storing manure and slurry more securely.
