B6e: Life in soil

Question 1

Describe clay soil(particle size, air spaces, permeability to water)

Answer 1

small

few and small air spaces

low ­ water retained in soil, soil can flood

Question 2

Describe loam soil(particle size, air spaces, permeability to water)

Answer 2

mixture of small and large;

many air spaces and variable in size

medium permeability ­- water retention is good

Question 3

Describe sandy soil(particle size, air spaces, permeability to water)

Answer 3

large (0.05 ­ 2 mm)

many air spaces and large

high - little water retained in soil

Question 4

What is loam soil

Answer 4

soil that contains a mixture of clay and sand

Question 5

What is humus

Answer 5

dead material in soil that is largely decomposed

Question 6

Experiments to compare the humus, air and water content of different soils (3)

Answer 6

humus: weigh, burn, reweigh
air: add water to sample until the water reaches the top and measure volume of water added
moisture: weigh, bake, reweigh(evaporates the water)

Question 7

What does life in soil depend on and why? (2)

Answer 7

supply of oxygen for respiration

supply of water to carry out reactions in cells

Question 8

Explain the importance of humus in the soil (2)

Answer 8

decomposes to release minerals needed for plant growth

improved aeration, +air/oxygen content; helps retain water

Question 9

Explain why earthworms are important to soil structure and fertility (4)

Answer 9

bury organic material in soil for decomposition by bacteria/fungi, improving nutrient content

burrows aerate soil, increase oxygen content; allow water to drain, ­reduce waterlogged and reduce ­chance of flooding

mix up soil layers, distributes nutrients more equally and allows dead material to be decomposed

neutralises acidic soils to grow more crops as neutral/alkaline soil are more fertile(plants will not grow if pH is too low)

Question 10

What did Charles Darwin do in terms of agriculture?

Answer 10

highlighted importance of earthworms in agriculture: improving the fertility and structure of the soil