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.
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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
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3
Q

What are the two types of fertilisers?

A
  1. Artificial fertilisers (Inorganic)
  2. Natural fertilisers (organic)
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4
Q

Artificial fertilisers

A
  • They are inorganic
  • They contain pure chemicals
    E.g. (ammonium nitrate) as powders or pellets
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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)
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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
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7
Q

When is leaching more likely to occur?

A
  • If the fertiliser is applied just before heavy rainfall
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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
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9
Q

What is leaching less likely with?

A
  • Natural fertilisers
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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
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11
Q

Why is the leaching of phosphates less likely than the leaching of nitrates?

A
  • Phosphates are less soluble in water
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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
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13
Q

What is eutrophication caused by?

A

Excess nutrients

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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
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