Soil processes (W3)

Question 1

Physical weathering of minerals

Answer 1

Physical weathering is the brittle fracture of rocks by the physical processes of: unloading and growth and expansion of ice.

Question 2

Decomposition of organic matter

Answer 2

Decomposition of organic matter describes the process by which soil organisms use soil organic compounds as a food source.
Example. Breakdown of leaf litter.
Stage 1. Primary decomposers break up litter detritus.
Stage 2. Secondary decomposers break down organic matter into smaller molecular structures
Stage 3. Corpses and faeces of decomposers provide substrate for further decomposition.

Question 3

Waterlogging

Answer 3

saturated with water. slows down rate of organic matter decomposition

Question 4

Soil ripening

Answer 4

Soil ripening occurs when a soil that is waterlogged or flooded dries out.
Changes can be physical, chemical or biological.

Question 5

Pedoturbation

Answer 5

Physical mixing of soil profile (e.g. by soil creep)

Question 6

Infiltration

Answer 6

Process by which water enters the soil and transports chemicals into the soil profile

Question 7

percolation

Answer 7

When water moves downwards through the soil.

Question 8

gleying

Answer 8

Gleyed soils are produced when waterlogging is irregular or seasonal

Question 9

Physical ripening

Answer 9

cracking followed by redox changes due to air entry

Question 10

Chemical ripening

Answer 10

oxidation of organic matter, iron and manganese

Question 11

Bioturbation

Answer 11

biological mixing of the soil by plants and animals

Question 12

Cryoturbation

Answer 12

physical mixing of the soil by frost

Question 13

eluviation

Answer 13

General term for the transfer of soil material in solution from one horizon, comprising two processes:
leaching and chetvulation

Question 14

Leaching (eluviation)

Answer 14

movement of soluble organic and inorganic soil components (solutes) in percolating water.

Question 15

Cheluviation (eluviation)

Answer 15

soluble organic complexes move metal cations through soil profile (especially iron and aluminium)

Question 16

Illuviation

Answer 16

introduction of salt by water by percolation from another horizon.

Question 17

What are the 6 soil horizons?

Answer 17

• O (organic)
• A (surface)-Mixed inorganic-organic layer of eluviation (leaching)
• Ea- Bleached horizon from which clays and iron oxides have been removed
• B (Subsoil)- Iron-rich horizon of illuviation (i.e. accumulating material)
• C (Substratum)- Weathered parent material on which soil is forming
• R (Bedrock)

Question 18

Podzol

Answer 18

infertile acidic soil

Question 19

Classification of world soils, FAO Soil Classification

Answer 19

• Classification of major soil groups based on their properties and dominant soil forming factors.
  -Organic soils 1 soil order:
  HISTOSOLS
  -Mineral soils 11 soil orders

Question 20

Organic soils: HISTOSOLS

Answer 20

Consist of organic debris which accumulates at the surface under wet or dry conditions