1. The “Master” horizons O A E B C R organic horizon on the soil surface
surface horizon high in organic matter, but composed of mineral soil – eluviation zone
subsurf. horizon light in color due to leaching – eluviation zone
subsurf horizon, from soil forming processes – illuviation zone
least weathered (and deepest) of all the soil horizons – from R or transported in
bedrock

5. Subscripts: Processes occurring in these Horizons
O horizon Oi Oe Oa
A horizon Ap Ab
identifiable (recognizable) material
Intermediate
highly decomposed (almost all gone)
plowed surface
buried surface

6. More Subscripts B horizons t g k s h w o clay “gleying” (very wet)
carbonates (dry regions)
sesquioxides (iron, aluminum, red/yellow)
“histic” humus (high organic content)
cambic horizon A diagnostic subsurface horizon that has a texture of loamy very fine sand or finer, contains
some weatherable minerals, and is characterized by the alteration or removal of mineral material. The cambic
horizon lacks cementation or induration and has too few evidences of illuviation to meet the requirements
of the argillic or spodic horizon.
“cambic” – weakly altered by removal & chem rx, no illuviation
“oxic” highly wx’d, tropical soils (Fe, Al oxides, red)

7. Last One (whew) and Rules
C horizon
r (weathered bedrock)
k (carbonates)
u (transported-in PM: unweathered)
ox (transported-in PM: weathered (“oxidized”)
Subscript Rules
rarely use more than three
t (almost) always first
Examples:
Btg, Cr, Bw, Ap, . . .

8. Types of Parent Material - Mode of transport
Type of P.M.
Mode of transport
Degree of sorting by size
Glacial till
Alluvium
Colluvium
Loess
Lacustrine
Residuum
Ice
Low (all sizes)
High (coarse dropped 1st)
Stream/river
Gravity
Low
Ice + wind
High (silt only)
Water (lakes)
High
None NA

9. Effect of Parent Material on Soil Formation – Transported PM
Mixed alluvium A C Bw C
40cm
Eolian sand

10. Effect of Parent Material on Soil Formation - Residuum
Residual shale A AB C
Bt1
Bt2
Granite
40cm A Bw C
Shale deeper and more developed –
shale = sedimentary, small particles – hi surf area  illuviated clay B
granite = high in quartz  sand, porous, resistant

11. Influence of climate on soil pH
High (basic)
Low (acidic)
Why?
Base cations soluble
Water = biomass (acids)

12. Influence of climate on Soil Organic Matter
Hot= rapid losses
Cold = low inputs

13. Influence of climate on Clay Formation
So where find the soil with more clay, Alabama, or Nevada?

14. Influence of climate on Carbonate Layer Depth
i.e., near surface