ENVS 200 EXAM 1 REVIEW
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47 Terms
Q: What is a soil horizon?
A: A distinct layer of soil with unique properties.
Q: What is horizination?
A: The process of separating soil into distinct layers.
Q: What are the 4 soil formation processes?
A:
1. Additions
2. Transformations
3. Translocations
4. Losses
Q: Define eluviation.
A: The removal of soil material (in suspension or solution) from an upper layer; "E" for exit.
Q: Define illuviation.
A: The accumulation of soil material in a lower layer, translocated from above; "I" for incoming.
Q: List the 5 soil-forming factors
A:
Climate
Living organisms
Organisms (vegetation, biota)
Relief (topography)
Parent material
Time
Q: Which soil horizons are considered "master horizons"?
O: Organic litter
A: Topsoil, organic matter + minerals (zone of addition)
E: Zone of eluviation (loss)
B: Zone of illuviation (accumulation)
C: Unconsolidated parent material
R: Consolidated rock (bedrock)
Q: What is soil taxonomy?
A: A hierarchical grouping of soil bodies based on measurable properties (USDA system).
Q: Define pedon.
A: The smallest 3D soil unit displaying unique soil properties (~1-10 m²).
Q: Define polypedon.
A: A group of similar pedons forming a distinguishable soil individual.
Q: Define soil profile.
A: A vertical section of soil showing all horizons.
Q: What is an epipedon?
A: A diagnostic surface horizon (O or A).
Q: What is an endopedon?
A: A diagnostic subsurface horizon (E, B, C).
Q: Mollic epipedon properties?
A: Dark, thick (>25 cm), pH 6-8, >0.6% organic C.
Q: Umbric epipedon properties?
A: Dark, thick (>25 cm), acidic.
Q: Ochric epipedon properties?
A: Light-colored, thin and/or low SOM.
Q: Melanic epipedon properties?
A: Very dark, volcanic ash, >30 cm thick, >6% OC.
Q: Histic epipedon properties?
A: Dark brown/black, organic, 20-35% SOM.
Q: Albic horizon properties?
A: Light-colored, highly leached (E horizon).
Q: Spodic horizon properties?
A: Bh, Bs; accumulation of OM, Al, Fe oxides.
Q: Cambic horizon properties?
A: Weakly developed B horizon; little/no illuviation.
Q: Oxic horizon properties?
A: Highly weathered, Fe + Al oxides, Bo horizon.
Q: Duripan properties?
A: Cemented, impermeable, dense Bqm horizon.
Q: Argillic horizon properties?
A: Bt horizon with clay accumulation.
Q: Kandic horizon properties?
A: Highly weathered clays (Bt).
Q: Natric horizon properties?
A: Btn horizon, sodium-rich, columnar/prismatic structure.
Q: Calcic horizon properties?
A: Bk horizon with CaCO₃ accumulation (calcite, dolomite).
Q: Name the 12 soil orders.
1. Entisols - poorly developed
2. Inceptisols - weakly developed
3. Histosols - organic soil
4. Gelisols - permafrost
5. Aridisols - desert soils
6. Andisols - volcanic ash soils
7. Alfisols - deciduous forest soils
8. Mollisols - grassland soils
9. Vertisols - swelling clay soils
10. Spodosols - conifer forest soils
11. Ultisols - wet, warm forest soils
12. Oxisols - tropical forest soils
Q: Define soil texture.
A: Relative proportion of sand, silt, clay (mineral fraction only).
Q: Size ranges for soil separates?
Sand: 0.05-2 mm
Silt: 0.002-0.05 mm
Clay: <0.002 mm
Q: Properties of sand?
A: Gritty, non-sticky, low surface area, rapid drainage.
Q: Properties of silt?
A: Smooth, erodes easily, holds moderate water.
Q: Properties of clay?
A: Sticky/plastic wet, cloddy dry, high surface area & water-holding capacity.
Q: What does Stokes' Law describe?
A: Settling velocity of particles in suspension (used for particle size analysis).
Q: What is an aggregate (ped)?
A: A cluster of soil particles forming a natural structural unit.
Q: Define flocculation.
A: Attraction/binding of clay particles into aggregates.
Q: Rank cations by flocculating power.
A: Na⁺ < K⁺ < Mg²⁺ < Ca²⁺ < Al³⁺
Q: Soil tilth definition?
A: Physical condition of soil as it relates to plant growth (aggregation, porosity, friability).
Q: Particle density (Dp) of typical mineral soil?
A: ~2.65 g/cm³
Q: Formula for bulk density (Db)?
Db = mass of dry soil/total dry soil volume
Q: Formula for %porosity?
%Porosity = 100(1-(Db/Dp))
Q: Relationship between bulk density and porosity?
A: As Db ↑ → porosity ↓.
Q: Pore size classes?
Macropores: >80 µm
Mesopores: 30-80 µm
Micropores: 5-30 µm
Ultramicropores: 0.1-5 µm
Cryptopores: <0.1 µm (unavailable to plants)
Q: Short-term tillage effects?
A: ↓ bulk density, ↑ porosity.
Q: Long-term tillage effects?
A: ↑ bulk density, ↓ porosity, ↓ SOM.
Q: How does compaction affect soil?
A: Increases Db, lowers porosity, reduces root penetration.
Q: How do residues & amendments affect soil?
A: Increase SOM → better aggregation, lower Db, higher porosity.