V. Soil Horizon Flashcards
Vertical differences that divide soil into zones or layers
Soil Horizons
A vertical section through all soil horizons from surface to unaltered parent material
Soil Profile
A relatively uniform soil layer parallel to the surface, differentiated by mineral or organic properties
Soil Horizons
Consists largely of organic material
O Horizon
Upper portion of O Horizon is primarily composed of
Plant litter (leaves, organic debris)
Lower portion of O Horizon consists of
Partly decomposed organic matter (humus)
Teeming with microscopic organisms that contribute oxygen, CO₂, and organic acids
O Horizon
Top of a profile, derived from plant and animal litter, transformed into humus
O Horizon (Humus)
Mixture of decomposed organic materials, usually dark in color
Humus
Bottom of the soil profile, consisting of either loose material or consolidated bedrock
R Horizon (Bedrock)
Largely composed of mineral matter
A Horizon
High biological activity and presence of humus (up to 30%)
A Horizon
Horizons O and A together are commonly called
Topsoil
Darker, richer in organic content, contains humus and clay particles
A Horizon (Topsoil)
Light-colored layer containing little organic material
E Horizon
Process in which water percolates through the E Horizon, carrying away finer particles
Eluviation
Process where water rinses upper horizons, removing fine particles and minerals
Eluviation
Removal of soil particles in suspension or solution from surface horizons
Eluviation
Also called subsoil
B Horizon
Where material removed from the E Horizon by eluviation is deposited
B Horizon
B Horizon is often referred to as
Zone of Accumulation
Deposition of soil materials from suspension or solution into a lower horizon
Illuviation
Accumulation of fine clay soils enhances
Water retention in subsoil
Clay accumulation in B Horizon can form a compact, impermeable layer called
Hardpan
O, A, E, and B Horizons together constitute
Solum (True Soil)
It is in the solum that
Soil-forming processes occur, and plant roots and organisms are active
Characterized by partially altered parent material
C Horizon
Horizons that show little resemblance to the parent material
O, A, E, B Horizons
Soil horizon that has not crossed the threshold separating regolith from soil
C Horizon
A blanket of loose, unconsolidated deposits covering solid rock
Regolith
Soil profiles lacking horizons due to erosion on steep slopes
Immature Soils
