Topic 5—B: Energy Transfer and Nutrient Cycles- 4. Fertilisers and Eutrophication Flashcards
1
Q
Loss of nutrients
A
- Crops take in minerals from the soil as they grow and use them to build their own tissues
- When crops are harvested, they’re removed from the field where they’re grown rather than being allowed to die and decompose there
- This means the mineral ions that they contain e.g. phosphates and nitrates) are not returned to the soil by decomposers in the nitrogen or phosphorus cycle.
- Phosphates and nitrates are also lost from the system when animals or animal products are removed from the land
- Animals eat grass and other plants, taking in their nutrients
- When they are taken elsewhere for slaughter or transferred to a different field, the nutrients aren’t replaced through their remains or waste products.
2
Q
What does adding fertilisers do?
A
- It replaces the lost minerals e.g. ( nitrates and phosphates ) (lost by harvesting plants, removing livestock and leaching from the soil)
- This means more energy from the ecosystem can be used for growth, increasing the efficiency of energy transfer
3
Q
What are the two types of fertilisers?
A
- Artificial fertilisers (Inorganic)
- Natural fertilisers (organic)
4
Q
Artificial fertilisers
A
- They are inorganic
- They contain pure chemicals
E.g. (ammonium nitrate) as powders or pellets
5
Q
Natural fertilisers
A
- They are organic
- They include manure, composted vegetables, crop residues (the parts left over after the harvest and sewage sludge)
6
Q
Environmental issues
A
- More fertiliser can be applied than the plants need
- This can lead to fertilisers leaching into waterways
- Inorganic ions in chemical fertilisers are relatively soluble meaning that excess minerals that are not used immediately are more likely to leach into waterways
7
Q
When is leaching more likely to occur?
A
- If the fertiliser is applied just before heavy rainfall
8
Q
Definition of leaching
A
- When water-soluble compounds in the soil are washed away e.g. by rain or irrigation systems
- Often washed into nearby ponds and rivers
- It can lead to Eutrophication
9
Q
What is leaching less likely with?
A
- Natural fertilisers
10
Q
What is the reason leaching is less likely with natural fertilisers?
A
- Because the nitrogen and phosphorus are still contained in organic molecules that need to be decomposed by microorganisms before they can be absorbed by plants.
- Meaning that’s their release into the soil for uptake by plants is more controlled
11
Q
Why is the leaching of phosphates less likely than the leaching of nitrates?
A
- Phosphates are less soluble in water
12
Q
What will using fertilisers change the balance of?
A
- Nutrients in the soil
- Too much of a particular nutrient can cause crops and other plants to die
13
Q
What is eutrophication caused by?
A
Excess nutrients
14
Q
Process of eutrophication
A
- Fertiliser from fields washed into stream/lakes by rain (leaching)
- Fertiliser causes algae to grow quickly, covering the water surface
- Algae blocks out light from penetrating the water, so underwater plants die as they’re unable to photosynthesise
- Bacteria decompose the dead plants which reduces the oxygen concentration in the water by carrying out aerobic respiration
- Fish and other animals die due to anaerobic conditions