Chapter 1 - Intro to Soil Science

Question 1

Functions of Soils (6)

Answer 1

• Medium for plant growth
• Maintains water supply
• Recycle materials
• Habitat for other organisms
• Engineering medium
• Modifier of the atmosphere

Question 2

Function: medium for plant growth

Answer 2

• Physical support
• Contains nutrients, water
• Ventilation system due to respiration: CO2 vents out, O2 replaces
• Buffer temperatures

Question 3

Function: maintain water supply

Answer 3

• Filters H2O - cleans it

* Slows H2O movement

Question 4

Function: recycle materials

Answer 4

• Soil is a big compost pile, decomposes plant and animal materials
• Producers-Consumers-Decomposers-Minerals-Producers cycle

Question 5

Biomass

Answer 5

• Living mass - organic matter

* Made of CHON (90% of living things)

Question 6

Function: habitat for other organisms

Answer 6

• Microorganisms

* Macroorganisms (earthworms, moles, etc.)

Question 7

Function: engineering medium

Answer 7

• Retaining walls to bridges

* Goal is to compact the soil

Question 8

Function: modifier of atmosphere

Answer 8

• Dry soil, limited plants = creates dust

* Affects temperature with enough dust in the air

Question 9

Soil

Answer 9

An unconsolidated layer of minerals and OM on the earth’s surface

Question 10

Regolith

Answer 10

Soil

Question 11

Soil is composed of

Answer 11

minerals, gases, water, OM, and microorganisms

Question 12

3 Minerals of soil

Answer 12

Sand, Silt, Clay

Question 13

Sand attributes

Answer 13

- Largest size, between .05 and 2.0 mm in diameter
Primary mineral (not broken down by chemical means, weathering)

Question 14

Silt attributes

Answer 14

• Primary & secondary minerals, some broken down

- between .05 and .002 mm in equivalent diameter

Question 15

Clay attributes

Answer 15

• Smallest size, <.002 mm in diameter

Heavy weathering

Question 16

Organic Matter (OM) - description and functions

Answer 16

• Living or once-living, carbon-based material
• Breaks down and releases elements back to the environment
• Feeds the “producers”, the plants, and all other organisms there

Question 17

Humus - description

Answer 17

• Dark-colored organic compound
• Very broken-down OM
• Very colloidal in nature

Question 18

Colloid - description

Answer 18

• A very small particle
• Large surface area vs. volume
• Glue-like, can pull things together

Question 19

Soil profile

Answer 19

A vertical view of the soil material (to any depth), contains horizons

Question 20

Soil horizons

Answer 20

Horizontal layers of the soil profile

Question 21

O Horizon

Answer 21

Organic, topmost layer; feeds the layers below it

Question 22

A Horizon

Answer 22

Topsoil; “plow layer”; usually a darker material (due to OM breaking down) with the most organisms

Question 23

E Horizon

Answer 23

Zone of eluviation

Question 24

Eluviation

Answer 24

Leaching; “the transportation of dissolved or suspended material within the soil by the movement of water when rainfall exceeds evaporation”

Question 25

B Horizon

Answer 25

Subsoil; less OM; accumulates some leaching; typically more clays than A horizon; lighter color

Question 26

C Horizon

Answer 26

Coarse layer of materials; limited weathering

Question 27

R Horizon

Answer 27

Consolidated/solid rock

Question 28

Influences on horizons

Answer 28

Weather
Erosion
Parent materials
Slopes
Plant types
Organisms

Question 29

Soil texture

Answer 29

• Describes the size of the soil particles
• The proportion of SSC (sand/silt/clay) in a soil, usually expressed as percentages
• Hard to change

Question 30

Loam

Answer 30

Soil having moderate amounts of SSC (a healthy balance, but not necessarily equal)

Question 31

Soil structure

Answer 31

• Describes the manner in which soil particles are aggregated, and defines the nature of the system of pores and channels in a soil.
• The arrangement of soil particles (SSC, OM) into aggregates, or soil peds
• Can be changed “easily” (such as compaction)

Question 32

Macropore size and purpose

Answer 32

> .08 mm

• movement of air/gasses and water, plant roots, micro-organisms
• generally found between peds (interpore peds)

Question 33

Biopores

Answer 33

Macropores that are created by plant roots, earthworms and other organisms

Question 34

Micropore size and characteristics

Answer 34

t permit much gas movement