Soil Profile and Soil Horizons

Presented by: Mr. Brian Oram, PG, PASEO Wilkes University GeoEnvironmental Sciences and Environmental Engineering Department Wilkes - Barre, PA 18766 570-408-4619 http://www.water-research.net

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

Where is the Rock Contact ?

Where is the Regolith ?

Where is the Soil ?

Soil Regolith

Rock ?

Regolith?

Soil?

What are these?

Rock

Polypedons and Pedons

Polypedon represents a single soil series or soil individual • 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 Pedon

Soil Profile

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

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

Soil Horizons A Horizons: “ Topsoil”

A Horizon • 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

Soil Horizons: E Horizons Albic Horizon (Latin - White)

E Horizon • 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

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

Bhs Horizon 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 Bs Horizon Bw Horizon

Soil Horizons: Bx and Bt Horizons

Horizons Indicate Reduced Infiltration Capacity and Permeability 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

Area of Highest Permeability along Prism Contact

Bt: Clay accumulation is indicated by finer soil textures and by clay coating peds and lining pores

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 Horizon

R- Horizons

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

Soil Horizons and Typical Structures

Source: http://www.vanaturally.com/soil.html

Time for Review

Answer the Following Fill In the Blanks

Weathering A. _________ breakdown of parent material and organic matter.

Eluviation B. __________ removal of clay, iron, humus, and aluminum compounds by soil solution.

drying of soil solution. Redoximorphic D. __________ feature associated with the reduction of iron by wetness (saturation and anaerobic conditions) Possible Answers: Eluviation, Redoximorphic, Illuviation or Accumulation, Weathering

Soil Horizons

Presented by: Mr. Brian Oram, PG, PASEO Wilkes University GeoEnvironmental Sciences and Environmental Engineering Department Wilkes - Barre, PA 18766 570-408-4619 http://www.water-research.net