Soil Profile and Soil Horizons

Presented by:

Mr. Brian Oram, PG, PASEOWilkes University

GeoEnvironmental Sciences and Environmental Engineering DepartmentWilkes - 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 Positionand 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 singlesoil 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 HorizonsO- 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 HorizonsA Horizons: “ Topsoil”

• Mineral Horizon NearSurface

• 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 HorizonsAlbic Horizon (Latin - White)

• Mineral Horizon NearSurface

• 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 HorizonsZone 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 StructuredBw Horizon

Soil Horizons: B HorizonsZone 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- HorizonsDistinguished 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: http://www.vanaturally.com/soil.html

Time for Review

Answer the FollowingFill 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, PASEOWilkes University

GeoEnvironmental Sciences and Environmental Engineering Department

Wilkes - Barre, PA 18766570-408-4619

http://www.water-research.net