5.1

Question 1

4 functions of soil

Answer 1

• medium for plant growth
• major wet storage and purification system
• habitat for organisms
• soil modifies the atmosphere through respiration of the soil organisms and plant roots

Question 2

soil layers

Answer 2

• organic/humus: top of soil with all the DOM
• topsoil: dark colour due to high amounts of organic matter
• subsoil: zone of accumulation –> minerals and particles are washed down
• parent rock: decomposed & weathered parent material

Question 3

physical and chemical weathering

Answer 3

• physical: coarser texture + just breaks up the rocks
• chemical weathering: finer texture + dissolves minerals in the rocks

Question 4

sand

Answer 4

• feels gritty because particles are big
• well drained so rarely water-logged
• warms up quickly due to high air content

Question 5

clay

Answer 5

• smallest particles / small pores
• poor drainage & prone to waterlogging
• takes long time to dry
• warms up slowly due to high water content

Question 6

silt

Answer 6

• everything in between –> smooth feel
• medium pores
• medium drainage

Question 7

good agricultural soil

Answer 7

• allows plant root growth
• nutrient retention
• free air and water movement
• crumbly and breaks up easily