35 terms

Soil Science Vocabulary

Mollic Epipedons
dark, colored mineral horizon, thick (>25cm), high concentration of base cations (Ca, Mg, K), developed under native prairies

A diagnostic surface horizon of mineral soil that is dark colored and relatively thick, contains at least 0.6% organic carbon, is not massive and hard when dry, has a base saturation of more than 50%, has less than 250 mg/kg P2O5 soluble in 1% citric acid, and is dominantly saturated with bivalent cations.
Umbric Epipedons
same as mollic, except % base sat. <50% due to leaching of basic cations, develops with higher rainfall than mollic

A diagnostic surface horizon of mineral soil that has the same requirements as the mollic epipedon with respect to color, thickness, organic carbon content, consistence, structure, and P2O5 content, but that has a base saturation of less than 50%
Melanic Epipedon
very black due to high organic matter, volcanic ash

A diagnostic surface horizon formed in volcanic parent material that contains more than 69% organic carbon, is dark in color, and has a very low bulk density and high anion adsorption capacity.
Organic Epipedons
Histic - naturally sat. with water
Folistic - like histic but not sat. with water more than 30 days
Ochric Epipedons
Fails to meet definitions: too light, thin, low in organic matter

A diagnostic surface horizon of mineral soil that is too light in color, too high in chroma, too low in organic carbon, or too thin to be a plaggen, mollic, umbric, anthropic, or histic epipedon, or that is both hard and massive when dry.
Task of Soil Survey
1) define each soil unit to be mapped.
2) to compile information about the nature and classification of each soil.
3) to delineate the boundaries where each soil unit occurs in the landscape.
Soil Pit
a rectangular hole large enough and deep enough to allow one or more people to enter and study a typical pedon. clean away loose debris from pit face, examine colors, texture, consistency, structure, plant rooting patterns, etc. to determien which horizons are present and at what depths their boundaries occur.
Soil Survey
The systematic examination, description, classification, and mapping of soils in an area. Soil surveys are classified according to the kind and intensity of field examination.
Argillic Horizon
A horizon that accumulates clay that has translocated from above. The Bt horizon identifies the argillic horizon.
Natric Horizon
Like the argillic, more than 15% exchangeable sodium, columnar soil structure
Kandic Horizon
accumulation of Fe and Al oxides, kaolinite clays, low cation-holding capacities, form in areas of intense weathering
Oxic Horizon
High weathered, very high in Fe and Al oxides, 10% weatherable minerals, found is humid tropical and subtropical regions
Spodic Horizon
Illuvial horizon, accumulation of collodial organic matter, aluminum oxide and iron, highly leached forest soils of cool humid climate on sandy parent materials
Albic Horizon
Light colored eluvial horizon, low in clay and other oxides (leaching), white or light tan
Calcic Horizon
Illuvial accumulation of carbonates (CaCO3), carbonates react with HCL to form CO2
Cambic Horizon
A slightly altered layer that has not undergone enough illuviation to become argillic. Bw horizon designation
Taxonomic Structure
Orders, suborders, great groups, subgroups, families, series
Soil Orders
Based on conditions under which the soil developed
Grouped by similarities in soil formation (wetter/dryer, colder/warmer)
Great Groups
Based on differences between soil horizons
Sub Groups
Describes profile characteristic
Based on soil properties that affect management and root penetration (texture, temperature, clay minerals, CEC, and depth)
Named from the town or landscape feature near where the soil was first recognized
soil order that has little profile development. parent material main determiner. productive: very fertile alluvial soils, unproductive: recently deposited sandy, shallow rocky soils
Few diagnostic features, proces of soil formation being in its early stages
dry soils, when irrigated - productive
frozen layers, very cold regions
organic soils formed in wetland accumulations of plant residues, cool and cold climates, drained and fertilized flower and vegetable production
recent volcanic ash deposits, subjected to only mild weathering, dark in color, low in density, early managed, minerals high capacity to hold phosphorus in unavailable forms, productive if fertilized
argillic subsurface least 35% sat. with basic cations, mild acid weathering, broad leafed forests and savannas
dark soils of grasslands (grain)
high levles of swelling-type clays, vertical mixing, deep cracks
acid soils in forested areas found is moist regions, not fertile
highly weathered soils under forests in humid areas
most highly weathered, primary minerals destroyed, subsurface oxides, nutrient low