Fundamentals: "How to start thinking soil science"

This module is designed to offer a firm set of facts that every student involved in agronomic, or environmental sciences should know, by heart.
The information offered below is presented in a condensed manor suitable for flash card study and examinations can be drawn from every bit of this.
The bold words are terms to commit to memory.

What is a-soil?

Functions of soils in our ecosystem

What is a typical soil composed of?

Approximately 50% solids and 50% pore space

Communicating soil information

Soil Morphology

The study of structure or form; properties characterized by sight, feel, smell or sound

Description of Soil Horizons

Master Horizons

O horizon or layer

a surface layer dominated by organic materials (> 20% organic carbon)

A horizon

- a mineral horizon, <20% organic carbon, which forms at the surface or beneath an O horizon

- characterized by a darker color than the rest of the profile due to the accumulation of organic matter; high biological activity

- eluvial horizon (loss of materials such as iron/aluminum oxides and clays)

E horizon

- an intensively leached eluvial horizon in which organic matter along with iron/aluminum oxides and clay have been removed; most commonly found in forest soils

- typically white or light gray in color due to the lack of coatings on the mineral surfaces

B horizon

horizon formed beneath an A, E or O horizon and is a zone of accumulation (illuvial horizons). May accumulate clay, iron/aluminum oxides, organic matter, carbonates, etc.

C horizon or layer

a layer of unconsolidated material showing little weathering (alteration) and biological activity (e.g., beach sand, alluvium deposited by rivers, glacial till deposited by glaciers)

R layers

consolidated rock that can not be dug with a shovel and shows little evidence of weathering (e.g., granite, sandstone)

L layers

layer can include organic and limnic (limnic = of or pertaining to fresh water; freshwater) materials. deposited in water by precipitation or through the actions of aquatic organisms, such as algae and diatoms, or derived from underwater and floating aquatic plants and subsequently modified by aquatic animals. They are used only in Histosols (organic soil)

M layer

root limiting subsoil layer consisting of nearly continuous, horizontally oriented, human-manufactured materials

W layer

indicates water layer(s) within or beneath the soil. [Wf if frozen; so the f is for frozen]

Transition horizons

A special kind of horizon that contain properties of two types of master horizons.

Example = AB horizon - has a dark color due to organic matter (A-like), plus red color due to accumulation of iron (B-like)

Common transition horizons: AB, BA, BC, CB

The dominant master horizon designation is listed first.

Not every soil contains all of the master horizons

Additional Terminology