Topic 6: Securing Earth's mosaic of Soil

Question 1

Name the layers of soil

Answer 1

• A horizon: topsoil
• B horizon: subsoil
• C horizon: regolith (parent material)

Question 2

What are aggregates?

Answer 2

Aggregates are collection of particles existing in soil, made of clay and organic matter which bind aggregates together.
These play a critical role in soil formation

Question 3

Identify and describe soil forming factors

Answer 3

CLORPT
- Climate: affects rate of weathering and movement of soil materials
- Organisms:
+ within soil: affect chemical reactions and turnover of materials, translate materials
+ at surface: protect from erosion
- Relief: soil at higher area is different lower area
- Parents material: different types of rock make different types of soils
- Time

Question 4

Name top 3 factors affecting soil capability

Answer 4

Climate, parent material, topography

Question 5

identify and describe different soil processes

Answer 5

• Argilluviation:
  + mechanical movement of fine-clay sized particles down a soil profile due to percolating water
  + clear and abrupt change in texture, usually distinguishing A and B horizons
• Vertization:
  + a series of sub-processes in smectite-dominant soil stemming from shrink/swell behavior, including cracking, lenticular ped formation and slickenside production
  + >35% or more clay throughout the profile; large cracks when dry
• Ferrallitization: the concentration of Fe and Al due to the loss of Si, caused by prolonged weathering of primary minerals and some secondary minerals
• Solonization: a saline soil is leached, leaving Na dominant on the exchangeable sites, dispersion and hydrolysis follow, leaving the texture-contrast soil with a very alkaline subsoil pH

Question 6

identify and describe different aspects of soil security

Answer 6

• Capability: natural state of soil, very hard to change
• Conditions: “health” of soil, can be changed
• Capital: value of soil
• Connectivity: connection with people, awareness
• Codification: policy to preserve soil

Question 7

What does it mean when soil has high clay content?

Answer 7

Higher ability to hold water

Question 8

What does it mean when soil has high cation exchange capacity?

Answer 8

Higher charges –> higher ability to hold nutrients

Question 9

What is the ideal range for pH level and how does pH affect soil?

Answer 9

Ideal pH range is 5.5-7.5 and adjusting pH helps ensure nutrients availability.