T2-1 Soil Science & Management, 4E

Chapter 2

Soil Origin and Development

T2-2 Soil Science & Management, 4E

Objectives

• Define a soil body

• List examples of five soil-forming factors

• Describe how soils develop

• Describe the horizons of a soil profile

T2-3 Soil Science & Management, 4E

Terms to Know• Alluvial fan• Alluvial soil• Chemical weathering• Colluvium• Delta• Eluviation• Eolian deposit• Floodplains• Frost wedging• Glacial drift• Glacial outwash

• Glacial till• Hydrolysis• Igneous rock• Illuviation• Lacustrine• Leaching• Levee• Loess• Marine sediment• Master horizon• Metamorphic rock (continued)

T2-4 Soil Science & Management, 4E

Terms to Know• Mineral soil• Organic soil• Oxidation-reduction• Parent material• Pedology• Pedon• Physical weathering• Plow layer• Polypedon• Residual soil• River terrace • Root wedging

• Sedimentary rock• Soil genesis• Soil horizon• Soil profile• Solum• Solution• Subsoil• Talus• Topsoil• Transported soil• Weathering

T2-5 Soil Science & Management, 4E

The Soil Body

Figure 2-1

T2-6 Soil Science & Management, 4E

Rocks and Minerals

• Igneous rock

• Sedimentary rock

• Metamorphic rock

T2-7 Soil Science & Management, 4E

Figure 2-4

Rocks and Minerals

T2-8 Soil Science & Management, 4E

Igneous Rock

Figure 2-5

T2-9 Soil Science & Management, 4E

Metamorphic Rock

Figure 2-6

T2-10 Soil Science & Management, 4E

Parent Material

Figure 2-8

T2-11 Soil Science & Management, 4E

Parent Material• Glacial ice• Wind• Water• Gravity• Volcanic deposits• Organic deposits

Figure 2-9

Figure 2-11

T2-12 Soil Science & Management, 4E

Climate

Figure 2-13

T2-13 Soil Science & Management, 4E

Organisms

Figure 2-14

T2-14 Soil Science & Management, 4E

Topography

• Influences soil development mainly by affecting water movement

T2-15 Soil Science & Management, 4E

Time

• Soils change over time due to aging process

• Humans

T2-16 Soil Science & Management, 4E

The Soil Profile

• Master horizons• Subdivisions of

master horizons

Figure 2-19

T2-17 Soil Science & Management, 4E

Summary• Soils form from minerals broken up by

action of weathering, plant roots, and the addition of decaying plant parts

• Five factors govern soil development:- Parent material- Climate- Life- Topography- Time