Soil Profile and Soil Horizons Presented by: Mr. Brian Oram, PG, PASEO Wilkes University GeoEnvironmental Sciences and Environmental Engineering Department Wilkes - Barre, PA

Time for Review

Definition of Soils A Natural 3 - Dimensional Body at the Earth Surface Capable of Supporting Plants Properties are the Result of Parent Material, Climate, Living Matter, Landscape Position and Time- 5 Soil Forming Factors. Soil Composed of 4 Components (mineral matter, organic matter, air, and water)

Major Components of Soil Pore Space (50%) This may contain air and/or water Soil Space (50%) Organic Matter Mineral Matter

Soil Regolith Rock Where is the Rock Contact ? Where is the Regolith ? Where is the Soil ? Rock ? Regolith? Soil? What are these?

Polypedons and Pedons This is the smallest unit used for soil mapping (1 to 10 m2) This is a 3 Dimensional Structure that extends to the limits of the genetic soil horizons Unit is large enough to describe the vertical and lateral variation in the soil Polygonal Surface Described as Unit of Sampling A combination of pedons is a polypedon. Polypedon represents a single soil series or soil individual

Polypedon Pedon

Soil Profile Image Source: Field Trip North Carolina (2005) – Outer Banks Vertical or Near Vertical Arrangement of Horizons that Tend to Parallel the Ground Surface to Parent Material This is a 2 Dimensional Structure Pieces of Black Top

Soil Horizons Layer of Soil Parallel to Surface Properties a function of climate, landscape setting, parent material, biological activity, and other soil forming processes. Horizons (A, E, B, C, R, etc) Image Source: University of Texas, 2002

Master Soil Horizons O Horizon- leaf litter / humus A Horizon- organic accumulation in mineral soil E Horizon- leached horizon (elluviation) B Horizon- zone of illuviation C Horizon – unconsolidated parent material R Horizon – lithic material (Rock)> R Not All the Master Horizons Will Be Present in All Profiles

Soil Horizons O- Organic Horizons Organic Layers of Decaying Plant and Animal Tissue Aids Soil Structural Development Helps to Retain Moisture Enriches Soil with Nutrients Infiltration Capacity function of Organic Decomposition Organic Matter Critical in Maintaining Water Stable Peds O Horizon Dark in Color Because of Humus Material - 1,000,000 bacteria per cm3

Soil Horizons A Horizons: “ Topsoil” Mineral Horizon Near Surface Eluviation Process Moves Humic and Minerals from O Horizon into A horizon Subordinates Ap - Plowed A Horizon Ab - Buried Horizon Soil dark in color, coarser in texture, and high porosity A Horizon

Soil Horizons: E Horizons Albic Horizon (Latin - White) Mineral Horizon Near Surface Movement of Silicate Clay, Iron, and Aluminum from the A Horizon through Eluviation Horizon does not mean a water table is present, but the horizon can be associated with high water table, use Symbol Eg (gleyed modifier) Underlain by a B (illuvial) horizon E Horizon

Soil Horizons: B Horizons Zone of Maximum Accumulation Mineral Horizon Illuviation is Occurring - Movement into the Horizon B Horizon Receives or Accumulates Organic and Inorganic Materials from Upper Horizons. Color Influence by Organic, Iron, Aluminum, and Carbonates Subordinantes Bw - Weakly Colored or Structured Bw Horizon

Soil Horizons: B Horizons Zone of Maximum Accumulation Other Subordinantes Bhs- Accumulation of illuvial organic material and sesquioxides Bs- Accumulation of sesquioxides Bt- Translocation of silicate clay Bx- Fragipan Horizon, brittle Bw-Weakly Colored and Structured Bhs Horizon Bs Horizon Bw Horizon

Soil Horizons: Bx and Bt Horizons Bx: B horizon with fragipan, a compact, slowly permeable subsurface horizon that is brittle when moist and hard when dry. Prismatic soil structure, mineral coatings and high bulk density Horizons Indicate Reduced Infiltration Capacity and Permeability Bt: Clay accumulation is indicated by finer soil textures and by clay coating peds and lining pores Area of Highest Permeability along Prism Contact

C- Horizons Distinguished by Color, Structure, and Deposition Mineral Horizon or Layer, excluding Rock Little or No Soil-Forming May be Similar to Overlying Formation May be Called Parent Material Layer can be Gleyed (Redoximorphic Feature) Developed in Place or Deposited May be Weathered Parent Material

R- Horizons Hard, Consolidated Bedrock (Lithic Material) Typically Underlies a C Horizon, but could be directly below an A or B Horizon. R Horizon

Soil Horizons and Typical Structures Source:

Time for Review

Answer the Following Fill In the Blanks A._________ breakdown of parent material and organic matter. B.__________ removal of clay, iron, humus, and aluminum compounds by soil solution. C.__________ deposition of translocated materials due to the drying of soil solution. D.__________ feature associated with the reduction of iron by wetness (saturation and anaerobic conditions) Possible Answers: Eluviation, Redoximorphic, Illuviation or Accumulation, Weathering Weathering Eluviation Illuviation Redoximorphic

Soil Horizons Presented by: Mr. Brian Oram, PG, PASEO Wilkes University GeoEnvironmental Sciences and Environmental Engineering Department Wilkes - Barre, PA