Term
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Definition
is the smallest (1 to 10 m2 on
surface) 3-D body of soil that can be
classified. It is the fundamental unit of
classification and it carries the full range of
characteristics of a particular soil. |
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Term
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Definition
is a landscape grouping of
contiguous and similar soils. It is the basis
of mapping as is also called a soil
individual. |
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Term
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Definition
our most detailed level
or class of soil classification and
represents a group of soil pedons with
similar and defined properties. |
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Term
| Soils are classified based on |
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Definition
measureable
morphological and physical properties in
the field along with a minimal amount of
lab tests. Lab tests verify a field
identification. |
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Term
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Definition
are the critical
component utilized in Soil
Taxonomy. |
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Term
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Definition
thick, dark colored, high base saturation, strong structure. Does
not become hard
and massive
when dry. soft, high pH and OM |
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Term
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Definition
Thick and dark,
but too low in base
saturation to be
mollic. Otherwise,
shares all other
characteristics
with a mollic
epipedon |
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Term
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Definition
too light colored, low organic content or thin to be mollic, may become massive and hard when dry. light colored surface layer.
Probably the dominant epipedon on 90%
of Virginia. |
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Term
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Definition
has
20 to 40 cm of
saturated cm of organic soil materials. wet during some part of year usually in marshes and swamps. |
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Term
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Definition
| thick, black, high in organic matter, common in volcanic ash soils |
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Term
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Definition
| Highly leached and weathered, light colored, clay and Fe and Al oxides mostly removed |
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Term
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Definition
| Illuvial high charge clay, most common subsoil, silicate clay accumulation |
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Term
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Definition
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Term
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Definition
| Weak color/structure B, second most common, clay accumulation, changed or altered by physical movement or by chemical reactions, generally non illuvial |
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Term
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Definition
| Illuvial Fe/Al+humus, organic matter |
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Term
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Definition
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Term
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Definition
Completely weathered down
to Fe + Al oxy-hydroxides – tropical, non sticky type silicate clays |
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Term
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Definition
dominantly dense,
brittle, root- and waterlimiting
layers that are
common in many
different geomorphic
settings of transported
material. Water and
roots flow/grow only in
a few vertical
macropores between
prism structures, usually loam textured, course prisms |
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Term
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Definition
Cold soils with shallow permafrost;
or deep permafrost plus frequent
frost churning (cryoturbation). |
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Term
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Definition
Soils with a thick (40 cm or more of
the top 80 cm) layer of organic soil
materials. Requires high OM
inputs and generally cold or wet to
inhibit OM decomposition. No
andic properties. |
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Term
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Definition
Coniferous/ericaceous acidic forest
soils in sandy parent materials with
Spodic horizons (Bh or Bhs). Can
also be wet sandy soils in coastal
regions. No andic properties. Fe, Al osides and humus accumulation |
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Term
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Definition
Soils formed from volcanic ash.
High in allophane and CEC, low in
density. Must have andic soil
properties. Allophane fixes high
amounts of P. |
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Term
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Definition
Highly weathered tropical soils
dominated by Fe+Al oxides and
virtually no weatherable minerals left
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Term
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Definition
Soils with high shrink/swell clay
content in the upper 50 cm and that
crack open regularly to form
slickensides. |
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Term
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Definition
Dry soils with a dry moisture
regime (< 90 days moist) and
accumulation of a secondary
mineral. |
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Term
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Definition
Highly weathered forest soils with an
argillic/kandic horizons (Bt) and low
subsoil pH and Base Sat. (< 35%) |
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Term
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Definition
Soils of the prairies with high > 50% base
saturation throughout. |
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Term
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Definition
Moderately weathered forest soils with
an argillic horizon (Bt) but moderate
subsoil pH and Base Saturation
(high Ca + Mg and Low in Al) |
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Term
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Definition
Soils with a weak diagnostic B
horizon (such as a Bw [Cambic]) or
a diagnostic epipedon other than
Ochric, or other weak diagnostic
characteristics. |
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Term
|
Definition
Soils without diagnostic B
horizons or characteristics and
without any epipedon except
Ochric. Development is limited
by the soil forming factors such
as time, climate, P.M., etc. |
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Term
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Definition
| Based primarily on moisture |
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Term
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Definition
Based on presence of other
important diagnostic horizons beyond |
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Term
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Definition
If not typical (“Typic”) of the
central concept of the Great Group, then
the differing property is named. |
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Term
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Definition
Wet at surface in growing
season |
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Term
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Definition
| Moist most of growing season |
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Term
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Definition
| Signficant periods of drought |
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Term
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Definition
| Dry in the growing season |
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Term
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Definition
Prounounced wet/dry
Mediterranean type climate |
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Term
|
Definition
particle size, mineralogy class, CEC
class and soil temperature class. |
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Term
|
Definition
Most defined classification level for soil
individuals. All members of series have similar
parent material, horizons, depth, drainage class,
and overall morphology. |
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Term
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Definition
slope, erosion, stoniness, etc.
classes used in mapping. |
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Term
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Definition
| rare freezes, can grow citrus |
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Term
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Definition
Long growing season, can grow
cotton, loblolly but not citrus commercially |
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Term
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Definition
Moderate growing season, can grow
corn but not those crops listed above |
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Term
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Definition
| Short growing season, can grow wheat |
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Term
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Definition
| Too cold for commercial crops |
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Term
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Definition
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Term
| Reds and yellows are due to |
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Definition
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Term
| Browns and overall black hues are due to |
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Definition
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Term
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Definition
are the background color of soil
without anything masking it. Usually indicate
wet reducing conditions because of removal or
reduction of red oxidized Fe coatings on grains
leaves a gray color. |
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
– organic compounds (acids)
– Clays (phyllosilicates, metal oxides, amorphous)
– Colloids (very fine clays and oranics)
– Weathering minerals |
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Term
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Definition
– Quartz (SiO2)
– Rock fragments (esp. if high in SiO2 !!!) |
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Term
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Definition
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Term
Over time, primary soil particles like
silts and clays become |
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Definition
held together
by humus or electrostatic forces, or
cemented by Fe-oxides. |
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Term
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Definition
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Term
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Definition
The degree (strength) and size/shape of the
peds has great influence over pore size
amount and distributions. |
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Term
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Definition
The units are approximately spherical or polyhedral and are bounded by curved
or very irregular faces that are not casts of adjoining peds. Found only in A
horizons. Formed by organic carbon, some clay, and organisms. |
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Term
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Definition
The units are flat and platelike. They are oriented horizontally. Found mainly in E
and B horizons, unless the surface is compacted. Formed by freeze expansion
or compaction (vertical pressure), or remain from bedding planes. |
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Term
Prismatic Shape – easy to
physically separate |
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Definition
The individual units are
bounded by flat to
rounded vertical faces.
Units are distinctly
longer vertically, and the
faces are casts or molds
of adjoining units. Form
by wetting and drying of
adjacent aggregates, and
always contain some
substructure. There are
physical prisms that can
be extracted from the soil
intact, and those in some
fragipans that can be
seen but not extracted. |
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Term
|
Definition
The units are blocklike or
polyhedral. They are
bounded by flat or
slightly rounded surfaces
that are casts of the faces
of surrounding peds. The
structure is described as
angular blocky if the faces
intersect at relatively
sharp angles; as
subangular blocky if the
faces are a mixture of
rounded and plane faces
and the corners are
mostly rounded. Form by
wetting and drying of
adjacent aggregates. |
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Term
|
Definition
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Term
|
Definition
Determined as dry mass (g or Mg) of soil
per unit volume (cm3 or m3). Noted as
Db. |
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Term
|
Definition
Db/Dp = solid space ratio in decimal form
Ex: 1.5/2.65 = 0.57 or 57%
(1 – Db/Dp) x 100 = pore space %
Ex: 1.00-0.57 = 0.43 x 100 = 43% |
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Term
| Factors Promoting Aggregation |
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Definition
Polyvalent (e.g. Al3+ or Ca2+) rather than
monovalent exchangeable cations like Na
• Shrink-swell from wet-dry and freezethaw
cycles
• Active microbial biomass generating
humic substances and “glues”
• Fe and Al-oxides stabilize many
aggregates |
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Term
|
Definition
Tilth is an old generic term used to
describe the physical condition of the soil
in relation to plant growth
• “Good tilth” means the soil is loose, nonplastic,
and not dense.
• We use consistence (Table 4.5) to
estimate and “semi-quantify” tilth. |
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Term
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Definition
Can a soil hold a give
slope? |
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Term
| Compression and compactibility: |
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Definition
Will a soil
material readily compact to serve as a roadbed
or foundation? |
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Term
| Expansion or shrink-swell potential: |
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Definition
Will a soil
change in volume with normal wetting and
drying cycles to a point of foundation damage? |
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