Basics of Redoximorphic Features.pdf

Redoximorphic
Features
Form in soils with aquic
conditions.
Dr. John Galbraith, 7/2006

Development of Hydric Soils
Inundation or soil saturation
Anaerobic conditions Inhibited OM decomp.
and accumulation
Chemical reduction (O, N, Fe, Mn, etc.)
by microbial action
Removal or re-oxidation

Red Soil
Coatings
Soil Color and
Oxidation/Reduction
• When reduced, Fe and Mn are mobile and can be
stripped from the soil particles
Coating of Fe 2O 3
Mineral grain (gray)
Remove Fe if
reduced
Absence of Red Coatings
Gray Soil

Redox Concentrations
Bodies of apparent
accumulation of
Fe/Mn oxides
• Masses
• Pore linings
– ped faces
– root channels
• Nodules and
concretions

• soft bodies
• frequently in the soil
matrix
• variable in shape
Masses

Pore Linings
• coatings inside a pore
on the pore surface

Nodules and Concretions
• Firm to extremely firm
bodies are often relict
• Should be irregular in
shape
• Currently active have
soft or diffuse edge
– with “halo” or “corona”
• Relict or inactive have
dark uniform colors
and are hard on edges
Fe/Mn nodules
washed from the soil

Redox Depletions
Bodies of low chroma
where Fe/Mn oxides
have been stripped out
• generally value ≥ 4
• chroma ≤ 2
• formerly called
“gray mottles”

Fe Redox Depletions and
Concentrations

Describing Redoximorphic Features
• Concentrations and Depletions
– abundance (the %, not few, common, many)
– type (masses, pore linings, etc)
– color (hue, value, chroma)
– contrast can be obtained from color charts
– location (if not evident from type)