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GES 175: Science of Soils

GES 175: Science of Soils. Laboratory Week 1. Bedrock. Soil Development. Soil vs Regolith. Regolith = unconsolidated material above bedrock. Soil = weathered portion of regolith. bedrock. contains characteristic layers called horizons. Soil Profile. A. E. soil. B.

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GES 175: Science of Soils

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  1. GES 175: Science of Soils Laboratory Week 1

  2. Bedrock Soil Development Soil vs Regolith Regolith = unconsolidated material above bedrock • Soil • = weathered portion • of regolith bedrock

  3. contains characteristic layers called horizons • Soil Profile A E soil B development Bedrock C Bedrock

  4. Material Transolcation/Development

  5. Soil Profile Argixerol Soil Horizons

  6. Soil Profile Soil Horizons A Bw E BE Btb Argixerol C

  7. O horizon-Organic A horizon-Mineral & Organic E horizon-Eluviation (Loss) B horizon-Illuviation (Gain) C horizon- little Alteration from Parent Material R horizon- Bedrock Master Horizons

  8. Master Horizons Ohorizons:Layers dominated by organic material. Some are saturated with water for long periods or were once saturated but are now artificially drained; others have never been saturated.

  9. Master Horizons Ahorizons:Mineral horizons that formed at the surface or below an O horizon, that exhibit obliteration of all or much of the original rock structure -an accumulation of humified organic matter intimately mixed with the mineral fraction and not dominated by properties characteristic of E or B horizons -properties resulting from cultivation, pasturing, or similar kinds of disturbance.

  10. Master Horizons E horizons:Mineral horizons in which the main feature is loss (eluviation) of silicate clay, organic matter, iron, aluminum, or some combination of these, leaving a concentration of sand and silt particles.

  11. MasterHorizons Bhorizons:Horizons that formed below an A, E, or O horizon and are dominated by obliteration of all or much of the original rock structure (1) (illuvial) concentration of silicate clay, iron, aluminum, humus, carbonates, gypsum, or silica (2)coatings of sesquioxides that make the horizon lower in value, higher in chroma, or redder in hue than overlying and underlying horizons (3)alteration that forms granular, blocky, or prismatic structure

  12. Master Horizons Chorizons or layers:Horizons or layers, excluding hard bedrock, that are little affected by pedogenic processes and lack properties of O, A, E, or B horizons. Most are mineral layers. Rhorizons or layers: Hard Bedrock

  13. 12 Soil Orders I AM A SUAVE HOG or I GAVE US OMAHA Compliments of Prof. M.J. LaForce

  14. I AM A SUAVE HOG Inceptisol- Soils with weakly developed subsurface horizons Alfisol- Soils with a subsurface zone of silicate clay accumulation and >35% base saturation Mollisol- Grassland soils with high base status Andisol- Soils formed in volcanic ash Spodosol-Acid soils with a subsurface accumulation of metal-humus complexes Ultisol- Subsurface zone of silicate clay accumulation and <35% base saturation

  15. I AM A SUAVE HOG Aridosol- Soils in Arid environments with moderate to strong development Vertisol- Clayey soils with high shrink/swell capacity Entisol- Soils with little or no morphological development Histosol- Organic soils Oxisol- Intensely weathered soils of tropical and subtropical environments Gelisol- Soils with permafrost within 2 m of the surface

  16. Twelve Soil Orders Entisol (recent) Inceptisol (L.-inceptum, begging) Mollisol (L.-mollis, soft) Alfisol (pedalfter) Ultisol (L.-ultimus, last) Oxisol (Fr.-oxide) Increasing Soil Depth Maturation (loss of Si)

  17. Twelve Soil Orders Aridisol (L.-aridus, dry) Spodosol (Gr.-spodos, wood ashes Gelisol (Gr.-gelid, very cold) Vertisol (L.-verto, turn) Andisol (L.-aridus, dry) Histosol (Gr.-histos, tissue) Climate Specific Material Specific

  18. Rock Ideal Weathering Series Entisol Inceptisol Aridisol (dry climate) Mollisol Vertisol (clay mineralogy) Alfisol Spodosol (cool and wet) Ultisol Oxisol

  19. Entisol -(ent) • Shallow to bedrock. • Limited use and management. • The most common uses are rangeland

  20. Inceptisol- (ept) • Steep slopes and cool climate slow soil development. • Inceptisols are widely distributed and occur under a wide range of environmental settings.

  21. Mollisol -(oll) • Soil formation under native grassland vegetation

  22. Alfisol (-alf) • Alfisols are mostly found in temperate humid and subhumid regions of the world. • Developmentally just past Mollisols

  23. Histosol -(ist) • Organic matter is highly decomposed and has few remaining plant fibers.

  24. Vertisol -(ert) • Abundant, ‘active’ clay particles are dominant

  25. Aridosol -(id) • Form in dry climates • White crust at the soil surface is a mixture of various soluble salts (definitely not snow!).

  26. Gelisol -(el) • Permafrost persists below 38 cm year-around. • The lack of significant microbial activity in these soils leads to an accumulation of organic matter.

  27. Gelisols are in very cold climates and typically contain permafrost

  28. Web Sites of Interest NRCS http://www.statlab.iastate.edu/soils/photogal/orders/soiord.htm Universities http://soils.ag.uidaho.edu/soilorders/index.htm http://soils1.cses.vt.edu/MJE/CSES3124/Laboratories.html Keys to Soil Taxonomy http://www.statlab.iastate.edu/soils/keytax/

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