Soil Orders Study Guide – Part I

These slides are to help organize in your mind:• Key diagnostic features for each Soil Order• Their developmental progression• Diagnostic surface & subsurface layers

See also – for the individual orders:

• the text’s description and plates• Soil Orders Study Guide – Part II (on course website)

Note their: • Relative order• Key formation factors

Soil Orders: Key Formative Factors

Processes Leading to Diagnostic Surface Layers (Epipedons)

See text for full descriptions

Argillic

Oxic

Calcic

Albic

Cambic

SpodicUnweathered

material

Light colored horizon

Weakly developed horizon

Acid weathering, Fe, Al oxides

Accumulation oforganic matter

Accumulation of silicate clays

High clay content

Clay skins evident

Extreme weatheringFe, Al oxides

Accumulation of inorganic salts

Carbonatesprimarily CaCO3

No

sig

nifi

can

t a

ccu

mu

latio

n

Modified from text: full version = Figure 3.5 (p. 83)See text for full descriptions

Processes Leading to Diagnostic Subsurface Layers

Missing: Andisols, Gelisols

Diagnostic Key to Soil Orders

In addition, see the text’s version: Figure 3.11 (p. 90)!

Development of soil orders

Bo

Bk ice

Bt

AAB Bh

Bs

Hi Base SatHi pHLo Base Sat

Lo pH Missing: Inceptisols, Andisols, Vertisols, Histosols

Development of soil orders

These are plausible, but not the only genetic profile descriptions that are possible for each soil order

Effect of time on soil development