Soils Introduction

Nota:

• Soils do not occur randomly; they do occur in a predictable fashion across a land surface and they change throughout time.

1. Colour

   Nota:

   • Standard notation: HUE Value/Chroma 10 YR 9/10 = white10YR 5/6 = Brown 10YR 1/2 = BlackDark = OrganicRed = IronWhite = Loss of IronBrown = Organic matter, less than blackValue: 0 (Black) - 10 (White)Chroma: 0 (Pastel) -  10 (Bright)
2. Texture

   Nota:

   • Aeration and drainage: textural discontinuities between layers can lead to reduced drainage Rooting depth: heavy clay soils and compaction can reduce the ability of plants to root adequately Fertility: clay retains nutrients better Erosion control: wind or water can transport sand and silt, because clay readily aggregates. 
3. Structure

   Nota:

   • Structural units develop as a result of adhesive substances ("glue," clay and organic matter) and external forces (compaction, swelling/wetting, freezing, bioturbation).
   1. Texture: a property that is inherited from soil parent material Structure: forms in response to pedogenetic processes

      Nota:

      • Both structure and texture have influence on soil performance. Susceptibility to erosion: increased in structureless soils, especially those high in sand and silt (lacking "glue") Susceptibility to compaction: increased with blocky or massive structure; high clay content Aeration: structure creates porosity. When soil aggregates (clay + OM), empty space is left behind as pores. Drainage: Water can move through the profile to lower horizons. This is impacted largely by clay. Impeded by blocky structure. Root growth: Lower bulk density makes this easier for plants Microbial activity: Granular, loamy soil is best for a microbial habitat.

1. Parent materials may be

   Nota:

   • Parent materials are a large determining factor is soil TYPE, but they are not the only factor.
   1. Organic vs Mineral
   2. Residual vs transported
      1. Sorted or unsorted

         Nota:

         • Mode of transportation alters texture, making it sorted or unsorted. Mode of transportation also provides some common patterns of surface expressions across a landscape.
      2. Modes of deposition for transported PM
         1. Alluvial: moving water

            Nota:

            • Fluvial deposits will be sorted, but vary - larger rocks will be deposited higher up the river channel, where there was more energy, and smaller and smaller sized rocks will be desposited further down. 
         2. Lacustrine: standing water

            Nota:

            • These materials will be VERY fine and very well sorted. 
         3. Marine: tides
         4. Eolian: wind

            Nota:

            • Highly sorted, fine material
         5. Glacial: ice, moraines

            Nota:

            • Morainally deposited materials are angular in shape, but have SOME rounding. They are highly unsorted materials
         6. Colluvial: gravity

            Nota:

            • VERY unsorted and VERY angular. (Note that while ice is also angular, this is MORE ANGULAR)

1. Factors of Soil Formation

   Nota:

   • Soil = f(Cl, O, R, P, T)
   1. Climate
   2. Organisms
   3. Parent material
   4. Relief'
   5. Time

1. Soil forming processes
   1. Additions

      Nota:

      • Additions of organic matter, water, etc. Organic matter comes from dead organisms and water usually comes from precipitation and then percolates throughout the profile.
   2. Losses

      Nota:

      • Water percolation can cause losses through horizons, or can cause the loss of organic matter from the surface. Clay, iron oxides, and organic matter can also be "pulled" through the soil profile
   3. Translocation

      Nota:

      • A horizon to other horizons. Predominately clay moving, and Fe oxides. Clay is translocated as a solid, and Fe Oxides are translocation as dissolved substances in soil soultion.
   4. Transformation

      Nota:

      • OM, minerals... transformation occurs when something completely becomes something else (X -> Y). The molecular makeup of the object changes