week 7

Question 1

Why are soils different?

Answer 1

• There is no true inheritance or genetics, unlike biology
• The concept of the pedon as a discrete object within the soil continuum
• Emphasis on defining mappable classes rather than classification

Question 2

What is the International standard soil classification system?

Answer 2

– Endorsed by the International Union of Soil Scientists (IUSS)
– Sponsored by the IUSS and United Nations Food and Agriculture Organisation (FAO)
– Based on soil morphology

Question 3

What is International standard soil classification system not good for?

Answer 3

NOT designed to be used for detailed mapping

– Regional, national, global soil distribution

Question 4

Soil features that are not present in Australia?

Answer 4

• Large areas of frozen soil
• Soils derived from volcanic ash
• Large areas of loess-derived soils

Question 5

What are Australian soil classifications?

Answer 5

Northcote’s Factual Key

Australian Soil Classification

Question 6

What are the broad divisions of Northcote’s Factual Key?

Answer 6

1. Organic Soil
2. Uniform Soils
3. Gradational Soils
4. Texture Contrast or Duplex Soils

Question 7

What is Australia’s primary soil classification system?

Answer 7

Australian Soil Classification

Question 8

What are the Five hierarchical levels of the Australian Soil Classification?

Answer 8

Order
Sub-order
Great Group
Subgroup
Family

Question 9

What is the A1 horizon?

Answer 9

This mineral horizon is usually where maximum biotic activity occurs with relatively higher organic matter content and darker colours

Question 10

What is the A2 horizon features?

Answer 10

Less organic matter than adjacent horizons
Not all profiles have an A2 horizon but it can be used (pale subsurface horizon) to assist in identification of other horizons
A2 differentiated from B horizon by its paler colour or by coarser texture (sandier)

Question 11

What is the B horizon?

Answer 11

• Intermediate soil mineral horizons designated B
horizons
• Below A horizon: have undergone significant
changes, so original parent material structure no
longer discernable
• Deep plant roots obtain water; low in organic
matter; however most nutrients found

Question 12

B1 features?

Answer 12

It has more in common with underlying B2

horizon

Question 13

B2 features?

Answer 13

Higher content of clay, iron, aluminium

Stronger soil colours than horizons above and below

Question 14

C horizon features?

Answer 14

parent material - weathered bedrock,

transported sediment or organic matter