CONCEPT OF THE WEATHERING PROFILE : CONCEPT OF THE WEATHERING PROFILE
Weathering Zone: Zone of Alteration Differing Physically, Chemically, or Mineralogically from Adjacent Zones, and Extending Laterally Beneath the Land Surface.
Weathering Profile: Vertical Assemblage of Weathering Zones from the Land Surface to and Into the Unweathered Parent Material.
CONCEPT OF WEATHERING PROFILE : CONCEPT OF WEATHERING PROFILE Includes Not just the Soil, but any Near-surface Material Affected by Weathering.
For Upper Midcontinent of North America: Parent Material is Originally Calcareous (Glacial, Eolian, Etc.)
MIDCONTINENT WEATHERING PROFILE : MIDCONTINENT WEATHERING PROFILE I Eluviated, organic, deeply weathered, leached of carbonates, oxidized
II Illuviated, inorganic, deeply weathered, leached of carbonates, oxidized
III Not strongly weathered, leached, oxidized
IV Not strongly weathered, unleached, oxidized
V Unaltered parent material, unleached, unoxidized
THE SOIL PROFILE : THE SOIL PROFILE Soil Profile: “Layered” Upper Part of the Weathering Profile Resulting from Alteration of Parent Material by Primarily Biochemical Processes.
“Layers” Better Known as Soil Horizons.
Soil Profile Coincides with Zones I and II and the Upper Part of Zone III of the Weathering Profile.
THE SOIL PROFILE : THE SOIL PROFILE Criteria for Distinguishing Major Soil Horizons
Organic Content [Amount and Type of Veg.; Preserv’n] Chelation Water Absorption Carbonic Acid
Color
Soil Texture
Soil Structure
SOIL HORIZONS : SOIL HORIZONS O: Large Amounts Organic Matter
A: Humus And Mineral Matter
E: Low In Clay, Sesquioxides
B: Accumulation Of Clay, Sesquioxides
C: Slightly Weathering Parent Material
D: Unweathered Parent Material
R: Bedrock
TYPES OF A HORIZONS : TYPES OF A HORIZONS MOLLIC: Dark, > 1% Organics, > 50% Base Saturation
Usually Developed Under Grass.
UMBRIC: Dark, > 1% Organics, < 50% Base Saturation
Usually Developed Under Forest.
OCHRIC: Light, < 1% Organics
Usually Developed Under Semiarid Vegetation.
TYPES OF B HORIZONS : TYPES OF B HORIZONS ARGILLIC: High in Clay (Textural B)
NATRIC: High in Exchangeable Sodium
SPODIC: High in Organics and Sesquioxides
OXIC: High in 1:1 Clays, Hydrated Oxides of Fe and Al
CAMBIC: Oxidized to Red (Color B)
FACTORS OF SOIL FORMATION S or s = f (cl,o,r,p,t…..) : FACTORS OF SOIL FORMATION S or s = f (cl,o,r,p,t…..) S = the soil; s = any soil property
cl = climate: precipitation and temperature
o = biota; vegetation usually predominant
r = topography; position on a slope; affects soil drainage, soil erosion; slope aspect also
p = parent material
t = time; duration
independent factors??
SOIL CLASSIFICATION LOWER LEVELS : SOIL CLASSIFICATION LOWER LEVELS Soil Series: Soils with Similar Profiles because of Same or very Similar Parent Materials. Example: Miami Series (P.M. Wisconsinan Till)
Soil Type: Subdivision of Series Based on Range of Textures. Examples: Miami Silt Loam, Miami Sandy Clay, Miami Clay Loam
SOIL CLASSIFICATION HIGHER LEVELS : SOIL CLASSIFICATION HIGHER LEVELS 11 Orders Distinguished by Diagnostic Horizons
Suborders Named for Diagnostic Physical or Chemical Property Prefix: that Property Suffix: Reflects Order
Great Groups and Subgroups: More Detailed Properties
SOIL CLASSIFICATION AN EXAMPLE: Humodic cryudent : SOIL CLASSIFICATION AN EXAMPLE: Humodic cryudent ent = entisol (order) a soil with a weakly-developed, A-C profile, little or no clay accumulation
ud = udic (suborder) moist and has low to moderate organics
SOIL CLASSIFICATION RELEVANT TABLES IN TEXT : SOIL CLASSIFICATION RELEVANT TABLES IN TEXT T3.8/69 Formative Elements of Orders of USDA System
T3.7/68 Orders and Suborders
T3.9/70 Naming Suborders
T3.10/70 Naming Great Soil Groups
Also Useful: 3.13/69
SOIL CLASSIFICATION AN EXAMPLE : SOIL CLASSIFICATION AN EXAMPLE cry = cold (great group)
odic = sodic B horizon + Hum = weakly developed (subgroup)
Try one yourself.
CLIMATE AND VEGETATION AS SOIL-FORMING FACTORS : CLIMATE AND VEGETATION AS SOIL-FORMING FACTORS Podzolization
Humid, Temperate Climates
Forest Vegetation
Acidic Conditions
Removal of Bases
Translocation of Fe, Al (Primarily By Chelation)
Creation of E Horizon
SOIL-FORMING FACTORS : SOIL-FORMING FACTORS Podzolization
North: Spodosols, Alfisols Colder, More Organic Matter
South: Ultisols Warmer, Less Organic Matter, More Oxidation
SOIL-FORMING FACTORS : SOIL-FORMING FACTORS Laterization
Tropical Conditions
Organics Oxidized
Silica Leached
1:1 Clays or Hydrated Al Oxides and Hydroxides
Oxisols
SOIL-FORMING FACTORS : SOIL-FORMING FACTORS Calcification
Dry Cimates
Calcium Carbonate Accumulation, Depth Related To Precipitation
Subhumid to Semiarid: Mollisols
Arid: Aridisols
PALEOSOLS : PALEOSOLS Soils that Formed on a Past Landscape
Types:
Buried Welded: Ground Soil Merged with it
Exhumed
Relic
PALEOSOLS : PALEOSOLS Importance
Influence on Ground Soil Development
Stratigraphic Correlation
Reconstruction of Paleoclimate, Vegetation