1. Soil:

• unconsolidated mass of organic & inorganic material, water and air

• inorganic material is measurably different from its parent material in physical and chemical properties

• exhibits layering

2. last lecture examined weathering processes that would alter the physical and chemical properties of parent material

3. today we'll examine:

• the soil profile

• soil characteristics

• soil classification & distribution

 

1. Processes affecting profile formation

• additions

• transformations: weathering & decomposition of organic matter

• vertical transfers: eluviation and illuviation; capillary rise; bioturbation

• removals: erosion; leaching

2. Horizons

• O Horizon: litter layer; common in forests

• A Horizon: topsoil; dark; nutrient rich

• E Horizon: eluvial horizon

  • clay, iron & aluminum eluviated most often

  • sand & silt concentrated here

  • light colored

• B Horizon: illuvial horizon

  • clay, iron & aluminum illuviated here

• C Horizon: weathered parent material

• R Horizon: consolidated bedrock

 

1. Color

2. Texture

• proportion of clay, silt & sand

• inherited from parent material

• affected by weathering

3. Organic Matter

• CO₂ generated during decomposition; helps promote chemical weathering

• affects water holding capacity & cation exchange capacity

4. Structure: size, shape and organization of peds

5. Bulk Density: weight of soil per unit volume

6. Soil Water Retention & Movement

7. Chemical Properties

• cation exchange capacity

• pH

 

• typical profile for each soil order

• defining set of characteristics for each soil order

• specific geographic distribution for each soil order related to climate and time