Characteristics that differentiate soil horizons

Characteristics that differentiate soil horizons

Color Texture Density

StructureConsistence

Organic Matter content Acidity

Mineral Accumulations Biological activity

Color Texture Density

StructureConsistence

Organic Matter content Acidity

Mineral Accumulations Biological activity

Original Russian Concept

o

Zone of eluviation

Zone of illuviation

Only 1 letter “l”

E

Illinois once was covered by a complex mix of prairie

and forest

Prairie dominated the flat expanses

Forest dominated the hilly land

thin A horizon

weak E horizon

strong B horizon

Young Soil in NC

Old Soilin NC

Well Defined Horizons

High Degree of Weathering

Highly Leached

Thick Solum

http://www.mo15.nrcs.usda.gov/features/gallery/

Poorly Defined Horizons

Low Degree of Weathering

Slightly Leached

Thin Solum

Water driven translocations

http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/soil_systems/soil_development_profiles.html

Eluviation

Illuviation

Illuviation

Illuviation

Sediment

Precipitationplus solutes, aerosols and particulates

Organic residues humus

Primary Secondary

minerals minerals

Leaching ofdissolved ions & OM

E(i)lluviationof

clayCaCO3

dissolved ionsdissolved OM

Capillary rise ofsalts

Capillary rise of

dissolvedions

Loss of gases

N 2, N 2

O, CO 2

Sediment

Soil forming processes

TRANSFORMATIONS

Adapted from Stewart (1990)

AdditionsLosses

Losses

Ad

dit

ion

s

Ad

ditio

ns

TRA

NS

LOC

ATI

ON

S

Lo

sse

s

TRA

NSL

OC

ATI

ON

S

http://courses.soil.ncsu.edu/resources/soil_classification_genesis/soil_formation/soil_transform.swf

Conceptual chronosequence

Horizon nomenclature

Master horizons are designated using capital letters (O, A, E, B, C).

Lowercase suffixes (aka subscripts) are used to denote specific horizon characteristics or features

(e.g., Oi, Oe, Oa, Bt, Btg, Bx)

Numbers following master horizon letters indicate unspecified changes in properties (e.g., A2, A3)

Numbers preceding master horizon letters indicate changes in parent material (e.g., 2A, 2B)

Combinations of master horizon letters indicate transition zones (e.g., AE, BC)

Sometimes a soil’s horizons are very

difficult to interpret.

Consider the profile to the left:

How many different parent materials are

represented ?

Where would one find such a soil ?

The best way to look at

soil profiles

Soil profiles can be investigated

using a soil auger

What is this guy doing ??

Making a soil monolith

Chroma

Val

ue

Hue

Munsell colorbook

Low #s

“Texture by feel”

Soil Structure

Granular crumb structure

Platy Blocky

Prismatic Columnar

Soil Consistence

Loose Friable

Firm Very Firm