Intro to Soil Science

Question 1

Definition of Soil

Answer 1

“The layer(s) of generally loose mineral and/or organic material that are affected by physical, chemical, and/or biological processes at or near the planetarysurface and usually hold liquids, gases, and biota and support plants.”

Question 2

Function of Soils (six ecological roles)

Answer 2

• medium for plant growth
• recycling system for nutrients and organic waste
• modifier of the atmosphere
• habitat for soil organisms
• engineering medium
• system for water supply and purification

Question 3

Soil components

Answer 3

45% mineral, 25% air, 25% water and 5% organic matter

Question 4

Soil & climate change

Answer 4

4 per 1000

carbon sequestration in soils for food security and climate

Question 5

Soil importance in global and local health

Answer 5

globally; soil science can help predict where arsenic contamination of groundwater is
locally; soil influence on food, water filtration, and chemical/pathogen exposure

Question 6

The five soil forming factors:

Answer 6

1. Parent material
   •The starting material from which a soil develops
2. Climate
   •Temperature and moisture
3. Biota
   •Kinds of plants, worms, rodents, insects, fungi, microbes
   4.Topography
   •Slope steepness, position, orientation
4. Time
   •Younger soils tend to be less developed than older soils

Question 7

How does soil formation lead to horizons?

Answer 7

The effects of climate, biota, topography, and time on the parent material bring about the vertical differentiation we see in soils.

Question 8

What is Soil profile and what is it composed of?

Answer 8

A vertical excavation exposes a 2D cross-section called the soil profile.

The soil profile is composed of layers called horizons.
•Variable thickness
•Parallel to the land surface.

Question 9

What is a soil pedon?

Answer 9

Pedon= A representative volume (3D)

Incorporates the natural vertical & lateral variabilityof a specific soil

Question 10

How do horizons form?

Answer 10

Translocation and accumulation of material in a soil.

Question 11

Soil Horizon notations:

Answer 11

• The O, A, E, and B horizons = solum
• The A, E, B, and C horizons are = regolith.
• R horizon (Bedrock): Hard rock. Little evidence of weathering.

Question 12

C Horizon:

Answer 12

~parent material~

-Can be dug with a shovel but retains the structural features of the sediment or rock from which the soil formed.

Question 13

O Horizon:

Answer 13

Fresh and partially decomposed organic layer at the soil surface. “Litter layer”

Question 14

A Horizon:

Answer 14

Dominated by mineral particles but darkened by the accumulation of organic matter (i.e.“Topsoil. ” )

Question 15

E Horizon:

Answer 15

• The “leached and bleached”horizon = zone of eluviation.
• The E horizon is a layer from which nearly all of the clay and iron have been removed and organic matter have not accumulated.

Question 16

B Horizon:

Answer 16

Subsoilzone of accumulation (illuviation) or alteration. For example: clay, calcium carbonate, silica

Question 17

R Horizon:

Answer 17

Hard bedrock