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Soil Color PowerPoint Presentation

Soil Color

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Soil Color

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  1. Soil Color Why is it so Important?

  2. Why is Soil Color so Important? • Soil Colors Tell Us: • Relative Organic Matter Content • Mineralogy • Depth to Seasonal High Water Table • Geologic History • Genesis of Diagnostic Features in the Soil

  3. Munsell Soil Color Book

  4. Munsell Color System • Albert Henry Munsell • Rational Way to Describe Color • Began in 1898 with Color Sphere • Broke color down into 3 aspects Hue Value Chroma

  5. Hue Pure Color Red, Yellow, Green, Blue, Purple Yellow-red, Green-yellow, Blue-green, Purple-Blue, Red-purple Measured off in 100 compass points Allotted 10degrees

  6. Value Chroma Difference from a pure hue to a gray shade • Quality by which we distinguish a light color from a dark one

  7. Color in Soils • Reddish, yellowish, or brownish: Iron oxides • Hematite – red • Goethite – yellowish brown • Ferrihydrite – reddish brown • Grey: Quartz and silicate minerals • White: Carbonates or other salts • Green:Potassium • Black/very dark brown: Organic matter • Black: Manganese oxides

  8. Red Desert California, Arizona, Nevada

  9. Gray Desert Idaho, Utah, Nevada

  10. White Sands New Mexico

  11. Green Sands Atlantic Coast, Hawaii

  12. Red Beds Texas & Oklahoma

  13. Dark soils in the Great Plains and the Corn Belt are from rich organic matter

  14. Basics • Matrix • Dominant (background) color of soil horizon • Mottle • Splotch of Color (opposite of matrix) • Redoximorphic (Redox) Features • Specific features formed from oxidation • Reduction reactions used to predict seasonal high water tables • Caused by the presence of water and minerals in the soil

  15. Reading Soil Colors • Optimum Conditions • Natural Light • Clear, Sunny Day • Midday • Light at Right Angles • Soil is Moist (not wet & not dry)

  16. Soil Horizons

  17. Naming Soil Horizons • Soil horizons (layers in the soil) are named so differences between soils can be identified. • Naming soil horizons takes practice

  18. When soil scientists are describing a soil they will discuss a lot about what they are seeing and how it should be named. • And what they are not seeing and what it should not be called ?

  19. Organic Horizons • O - horizon - organic material (no mineral materials) 1) forest litter 2) organic soil or peat soils, or muck • Oi - undecomposed (fibris) • Oe - moderate decomp. (hemis) • Oa - decomposed (sapric)

  20. Organic Soil Profile This trenching machine is digging through the Oe horizon of an organic soil. Trenches needed to remove water so the peat will dry before harvest.

  21. Organic Soil Horizons in a forest litter Oi Oe

  22. Processes of Mineral Soil Horizon Formation • Additions - H2O, organic matter, air, soil particles, salt • Losses - H2O, organic matter, CO2 , nutrients by plant removal • Transformations - Changes to soil structure, development of clay minerals, weathering of minerals to elements, chemical Rx • Translocations - movement from one horizon to another of O.M. Clay, Water, Iron, & Nutrients in colloidal size, (very small particles) clay films on peds are evidence of this translocation = clay (film) coating

  23. Mineral Soil Horizons • A horizon - surface horizons that accumulate O.M. • Ap = plowed soil Ap EB Bt Ap BC C

  24. E Horizons A E E/B Bt BC C • E - Translocation out – • Zone of Eluviation- Leaching out • Lighter in color than horizons above or below

  25. B Horizons- 2kinds: • Translocation in - below an A, E, or O with an accumulation of clay, iron, humus (O.M. decomposed.) or carbonates (CaCO3) zones of illuviation • or alteration of the original parent material, development of color or structure - Bw Bt

  26. C Horizons • C - little affected by pedogenic processes and lack properties of O-A-B-E- or is the Parent Material Solum = A + B C horizon

  27. Rock Horizons • R = hard rock • Cr = Soft Rock

  28. Subscripts - all B horizons have a subscript, most transition horizons do not.* = Important for MN • * a - sapric - organic soils - well decomposed • * b - buried soil horizon • d - dense - geogenic soil material (compacted by glacier) • * e - hemic - mod. decomp. - organic soil • f - frozen soil - permanently frozen, permafrost • * g - gleyed soil - gray color due to low O2 - reduction of Fe • * h - accumulation of humus - O.M. other than in the A or O horizons • * i - fibric - organic - non-decomposed • * k - accumulation of calcium carbonate (CaCO3) • * m - cementation - hard - indurated

  29. Subscripts cont. • n - sodium accumulation • * p - plowing - only used with A • q - silica accumulation - very weathered or old soil • * r - soft rock - used with C or Cr • * s - sesquioxides (1.502) (Fe2O3) accumulation of Fe and Al - red color • *ss – slickensides present –shiny surface on ped face caused from soil rubbing against soil • * t - clay accumulation - clay films • * w - color or structure development (Bw) • x - Fragipan - hard, dense layer that developed with time • y - gypsum accumulation (CaSO4) • z - salts more soluble than gypsum (KCL - NaCl - NaSO4)

  30. Transition Horizons • AB - Like A - some of B • BA - Like B - some of A • AE AC BC • E/B - Both E and B particles are present - • “B & E” used for soils with Lamellae - thin bands of accumulating clay and iron in sandy soils

  31. Lithologic Discontinuity • A • Bw1 • Bw2 • 2C • L.D. isdesignated by number in front of horizon = more than one parent material 2 parent materials Loamy Mantle Outwash

  32. Practice at naming horizons – Soil from Badlands of North Dakota---Texture of horizons 1,2,3,4 = loam---Note Carbonates in horizon 3 DYAD – Name 4 horizons Using one transition horizon • --- • --- • --- • ---

  33. Sandy soil from Northeast MinnesotaTexture of Horizon 1,2,3,4 = Sand

  34. Goodhue County Soil, Southwest of Redwing Mn.Texture of horizon 1 & 2 = Silt Loam, Hrz 5 = Silty ClayHrz. 4 = Cobbly loam, Hrz. 5 = Loam • A • E • Bt • 2BC • 2C