fertilisers and farming

Question 1

give the natural cycle of nutrients through soil due to plants (3 marks)

Answer 1

• crop removes nutrients from soil
• plant uses nutrients to make new biological molecules for growth
• dead plant decomposed by saprobionts returning nutrients to soil

Question 2

explain how farming disrupts natural cycle of nutrients through the soil (3 marks)

Answer 2

• crops removes nutrients from soil
• crops uses nutrients to make new biological molecules for growth
• crops are harvested and removed from soil meaning no nutrients returned to soil
• nutrient concentration of soil decreases

Question 3

why are fertilisers used

Answer 3

to replace minerals/lost nutrients

more energy for growth

so increases efficiency of energy transfer

Question 4

what are the 2 types of fertiliser

Answer 4

artificial

natural

Question 5

give 3 characteristics of artificial fertilisers

Answer 5

• inorganic matter
• contain pure chemicals
• powder or pellet

Question 6

why do artificial fertilisers pose a risk to the natural environment

Answer 6

they are soluble so there is immediate release of nutrients

causes issues in environment (due to run off in rivers)

Question 7

give a characteristic of natural fertilisers

Answer 7

organic matter

Question 8

how do natural fertilisers release nutrients into the soil

Answer 8

saprobionts hydrolyse organic matter (manure, composted vegetables) to release nitrogen and phosphorus into the soil

Question 9

why does the concentration of fertilisers added to soil need to be carefully controlled

Answer 9

too much fertiliser can:

• decrease plant growth
  as decreases water potential of soil = so water moves out of plant but plant needs this to grow
• eutrophication (caused by too many nutrient ions in an ecosystem caused by leaching of mineral ions)

Question 10

define leaching

Answer 10

when mineral ions dissolved in water are washed away

Question 11

describe the process of eutrophication

Answer 11

• fertiliser is added to a grass field
• fertiliser dissolves in water
• mineral ions leached from soil in field into pond/lake/river
• in lake plants grow at bottom some fish and algae
• rapid growth of algae on surface of pond. blocking light from reaching plants below
• plants can’t photosynthesise due to lack of light reaching them so they die
• so rate of decomposition by sapriobionts increases
• number of aerobic bacteria increase
• oxygen concentration in water decreases as bacteria respire aerobically
• fish and other organisms die due to decreased oxygen concentration