13.4 - Use Of Natural And Artificial Fertilisers

Question 1

What do fertilisers do

Answer 1

Add mineral ions such as ions of nitrogen, phosphorus and potassium back into the soil

Question 2

How do we replace the minerals lost from agricultural ecosystems

Answer 2

• Adding fertilisers
• ensures crops and livestock can continue to grow and increase in biomass as normal, ensuring yields remain high

Question 3

Explain why fertilisers are needed in agricultural ecosystems

Answer 3

• crops/livestock take in nutrients (e.g. inorganic ‘mineral’ ions) from the soil as they grow and use these nutrients to generate biomass
• the crops/livestock are eventually removed from the fields. Instead of dying and decomposing there naturally
• therefore, the mineral ions (e.g. nitrates and phosphates) now contained in the biomass of these crops or livestock aren’t returned to the soil by microorganisms
• this interrupts the crucial processes of nutrient recycling (e.g. nitrogen and phosphorus cycles)
• if this interruption occurs over a long period of time, the conc. of nutrients in the soil will decrease eventually leading to a decrease in crop yields or meat and milk from livestock

Question 4

What 2 types of fertilisers are there + examples

Answer 4

Natural fertilisers
- e.g. slurry, bone meal, manure, dead/decaying remains of animals or plants

Artificial fertiliser
- e.g. mined from rocks and converted into different forms then blended together. Most contain N.P.K. (Nitrogen, Phosphorus, and potassium)

Question 5

What is the difference between Artificial and natural fertilisers

Answer 5

• artificial = inorganic. They contain pure chemicals as powders or pellets
• natural = organic matter

Question 6

Why might plants require potassium

Answer 6

• enzyme activation
• stomata regulation
• photosynthesis
• starch/protein synthesis
• translocation

Question 7

How do fertilisers increase NPP in plants

Answer 7

1) Nitrates: needed for protein synthesis for growth of new tissues/biomass
2) Phosphates and nitrates: needed to synthesise ATP providing energy for active transport and cell division
3) Phosphates and nitrates: needed to synthesis nucleic acids required for enzyme production which control all metabolic processes like photosynthesis

Question 8

Suggest a reason why, after a certain point, the addition of more fertiliser no longer improves the productivity of acrop.

Answer 8

Some other factor is limiting photosynthesis, e.g. light, CO,, and only the addition of this factor will increase photosynthesis and hence productivity.