1. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 5 Soil Materials and Formation

2. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Soil Makeup, Origins, and Use Soft material covering Earth’s surface Formed by heating, cooling, water, wind, decomposing plant/animal material Provides place for plant’s roots to grow; food and water for plants; home for small animals

3. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Soil Body Top—where atmosphere or shallow water begins Bottom—farthest reach of deepest rooted plants Pedon—section of soil (usually about 3' x 3' x 5' deep) used to study soil makeup of particular area

4. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Soil Formation All soil begins with solid rock, which is broken into smaller pieces by weathering –Physical: temperature, water, wind, root wedging, other factors –Chemical: dissolution, hydrolysis, hydration, oxidation- reduction

5. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Rocks of Earth’s Crust Igneous—formed by cooling and solidification of molten materials deep in Earth Examples: –granite (made of feldspar, quartz, other minerals): harder, coarse-grained –basalt: softer, fine-grained

6. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Rocks of Earth’s Crust (continued) Sedimentary—formed by loose materials like mud or sand being deposited by water, wind, other agents –slowly cemented by chemicals and/or pressure into rock –overlays 3/4 of igneous crust Examples: sandstone, limestone

7. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Rocks of Earth’s Crust (continued) Metamorphic—igneous or sedimentary rocks subjected to great heat/pressure –limestone subjected to great heat and pressure changes to marble –soils arising from metamorphic parent materials resemble soils from original sedimentary or igneous rock

8. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Soil-Forming Factors Five traditional factors –parent material –time –climate –organisms –topography One additional factor: humans

9. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Parent Material Rock or other material in which soil is formed; limestone most common Affected by glaciers, wind, water, gravity, volcanic deposits, organic deposits

10. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Time Young soils—low in nitrogen, high in phosphorus Mature soils—generally productive Old soils—high in nitrogen, low in phosphorus, become more severely weathered, more highly leached, often less productive

11. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Climate 1st effect—physical and chemical weathering of rock 2nd effect—temperature and rainfall –higher temperature, faster chemical reaction –rainfall leaches lime, clay, plant nutrients, other chemicals

12. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Organisms Plants, insects, microbes –grassland soil: highest organic matter –forest soil: less organic matter –desert soil: least organic matter –vegetation also affects location of nutrients and other ions in the soil

13. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Topography and Human Factor Topography—soil’s position in landscape influences soil development mainly by affecting water movement Human—rapid, dramatic, and different from other factors –Examples: air pollution and earth moving

14. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Soil Horizons and Profile Horizons—layers where additions, losses, translocations, transformations happen Profile—vertical section through soil extending into unweathered parent material that exposes all horizons

15. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Horizons Master — A: topsoil; B: subsoil; C: parent material Other — O: organic layer—generally undisturbed — E: greatest eluviation, or loss by leaching — R: underlying hard bedrock