Term
|
Definition
Soil is mineral and/or organic material at the
Earth’s surface that is capable of supporting
plant growth and that is influenced by the
soil forming factors of climate, vegetation,
parent materials, topography and time. |
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Term
|
Definition
Soil extends from zones of ice and cold
limitations at high elevations to the rooted
emergent zone in wetlands. |
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Term
Most “soil” used in
commercial
nurseries and
greenhouses is |
|
Definition
actually manmade
media
composed of pine
bark, peat, sand,
perlite, etc..
Regardless, the
same basic
principles of soil
science apply! |
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Term
Leaf litter and
roots are “bioprocessed”
and
decomposed to
form humus, |
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Definition
which
is the dark black
material seen
coloring this
topsoil layer. In the
process, nutrients
and energy are
released in the food
chain. |
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Term
|
Definition
In addition to the
obvious organisms
like trees, soils
support a wide
variety of visible and
microscopic animals,
microbes and other
organisms. |
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Term
| Soil Fertility & Nutrition |
|
Definition
The soil holds and supplies macronutrient ions
for plant uptake – N, P, K, Ca, Mg and S. |
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Term
| Soil Fertility and Nutrition |
|
Definition
cations: K+, Ca2+, Mg2+, NH4
+ |
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Term
| Soil Fertility and Nutrition |
|
Definition
Anions: NO3
-, H2PO4
- , SO4
2- |
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Term
| Soil Fertility and Nutrition |
|
Definition
| Micronutrients: B, Cu, Fe, Mn, etc. |
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Term
| TDS = Total Dissolved Solids |
|
Definition
expressed as
mg/L. Sum of Ca+K+SO4 etc. in solution.
Laborious to analyze for! |
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Term
|
Definition
Typically estimated by electrical conductance
(EC) in μS/cm where TDS = 0.7 EC. |
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Term
|
Definition
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Term
|
Definition
• Acid-base reactions; sulfide oxidation
and carbonate neutralization reactions.
• Background carbonation reactions in
non-sulfidic materials.
• Hydrolysis of primary mineral grains.
• Entrained Cl and SO4 in rocks (minor).
• Other minor weathering reactions like K
release from micas, etc. |
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|
Term
Soils develop
horizons due to |
|
Definition
the
combined process of (1)
organic matter deposition
and decomposition and (2)
illuviation of clays, oxides
and other mobile
combounds downward with
the wetting front. In moist
environments (e.g. Virginia)
free salts (Cl and SO4 ) are
leached completely out of
the profile, but they
accumulate in desert soils. |
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Term
|
Definition
• O - Organic litter layers (> 20% OM)
• A - Organic darkened mineral soil
• E - Leached light-colored eluvial zone
• B - Zone of clay/iron/OM illuviation
• C - Geochemically weathered P.M.
• R - Hard rock; not always encountered;
really a layer and not a horizon. |
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Term
|
Definition
(Bt) horizon
in soil with moderate
to high charge clays. |
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Term
|
Definition
(Bt) horizon
in soil with low
charge (e.g. Fe
coated kaolinite)
clays. |
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Term
|
Definition
• Soils are charged and retain ions against
leaching because of that.
• Soil humus, clay and oxides all contribute
to net soil charge
• Most soils are net negatively charged
• Most soils actually contain a mix of
negative and positive charges
• We can measure the magnitude of charge in
cmolc per kg. |
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Term
|
Definition
Once infiltrated into the soil, water
interacts with soil solid mineral
and organic surfaces which provide
hundreds of soluble ions and
organic substances into soil
solution via simple dissolution,
cation exchange, and metabolic
processes. |
|
|
Term
The rate of water
movement into the soil, |
|
Definition
and how much water
the soil holds for plant
growth are directly
controlled by soil
texture, structure, and
density. Deep red colors
like seen in this soil
generally indicate that
the soil is seldom
saturated. The red
color is due to oxidized
iron, like rust on a
frying pan. |
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Term
|
Definition
Many important chemical and
biological processes in soils are
controlled by the balance of H+ and
OH- ions in soils which is
estimated by measuring soil pH. |
|
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Term
|
Definition
• Soil pH estimates the concentration
of protons (H+) in an equilibrium
soil solution.
• If H+ = 0.0001 moles/liter or 1 x
10-4, then pH = 4.0. |
|
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Term
|
Definition
are highly
acidic with pH < 5.5 due to
thousands of years of organic
matter decomposition and
leaching. |
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Term
|
Definition
(<4.0) are associated with
acid sulfate weathering
processes in a wide range of
mining environments. |
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Term
|
Definition
• Soils are “reusable” resources, but are not
really “renewable”.
• Soil quality is a measure of the ability of the
soil to carry out ecological functions.
• Soil quality reflects a combination of
physical, chemical, and biological
properties. |
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Term
|
Definition
is the
chemical and physical
breakdown of rocks, soils,
and mineral particles into
smaller and frequently
different mineral forms. |
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Term
|
Definition
precedes the
formation of soils from
parent materials acted
upon by soil forming
processes. |
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Term
|
Definition
is the disintegration of
large rocks and minerals into smaller
mineral grains. This is driven by water, ice,
gravity and wind action in many different
forms. Exfoliation is the major form. |
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Term
|
Definition
is the decomposition
of primary minerals like feldspars and
quartz into secondary minerals like
kaolinite and soil vermiculite.
• As this occurs, considerable mass is also
lost as ions leach to ground water.
• Secondary minerals like kaolinite can also
weather further to very stable forms like
gibbsite. |
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Term
|
Definition
• Dark colored primary minerals contain Fe, Mg and
other metals and are easier to weather than quartz,
mica and most other light colored minerals.
• Most resistant minerals (quartz) have simplest
str structure, least amount of metal substitution takes
place near earth’s surface!
• Sedimentary rocks vary in weatherability based on
their minerals combined with their cementing
agents. Limestones vs. sandstones; Fe-cemented vs.
Ca-cemented sandstones. |
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Term
| Chemical Weathering Processes |
|
Definition
Chemical weathering is driven by rainfall and
leaching, warm temperatures, and organic
acids in the soil solution, accelerated by
microbial and vegetative action.
All the major chemical weathering reactions
(hydration, hydrolysis, carbonation,
redox, complexation, dissolution) involve
water as a reactant and driving force. |
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Term
| Overall Weathering Results |
|
Definition
Virtually any parent material, given
enough time, water, and warmth will
weather to:
• Quartz sand and silt grains
• Silicate clays like vermiculite and
kaolinite
• Fe and Al oxides that form coatings
on and between clays and silts |
|
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Term
|
Definition
• Parent Material – mineral and organic
• Climate – rainfall/temp. drive the process
• Organisms – plants, animals, microbes
• Topography – slope, aspect, landscape
• Time – All four of the factors above are
strongly interdependent and interact via soil
forming processes over time to form soils. |
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Term
|
Definition
• Igneous – Composed of primary minerals
formed from magma or extruded lava, etc.
• Sedimentary – Composed of primary and
secondary minerals deposited in oceans,
lakes or fluvial environments.
• Metamorphic – Change in form from other
rocks put under heat and pressure. Often
crystalline and similar to igneous rocks,
often layered. |
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Term
|
Definition
forms in place (in situ) via
weathering of underlying parent material, or
from organic materials deposited in place
(see next slide). |
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Term
|
Definition
• Colluvium – gradual gravity slumps
• Alluvium – fluvial stream deposits
• Marine Sediments – ocean deposited
• Glacial Till and Outwash – ice sheets and
meltwaters, respectively
• Lacustrine Deposits – lakes, often near ice
• Loess – Windblown silts
• Eolian – Windblown sands
• Volcanic Ejecta – ash, cinders, lapilli |
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Term
|
Definition
• Coastal Plain – sandy surface over
silts, limes, and mucks.
• Piedmont – crystalline igneous/
metamorphic rocks.
• Blue Ridge – Same as Piedmont, just
pushed up 300 m!
• Valley and Ridge – Folded and faulted
sedimentary rocks. Sandstone ridges. |
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Term
|
Definition
• O and A horizon genesis
• Nutrient cycling and concentration
• O.M. decomposition leading to
carbonic acid and organic acids in
solution
• Enhance infiltration and limit runoff |
|
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Term
|
Definition
• Controls runoff vs. infiltration
• Slope/aspect affect solar loading
• Lower positions receive sediments,
nutrients and salts (in arid areas)
• Often controlled by parent material |
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Term
|
Definition
• Primary minerals weather to secondary
minerals.
• Sands weather to silts and clays
• Iron oxides and gibbsite (Al)
accumulate
• May be limited by climate, P.M., etc. |
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Term
|
Definition
• 0-A-E-B-C-R – Master Horizons
• Ap, Bt, Cg –special properties.
• Bt1, Bt2, Bt3 – 3 Bt’s in sequence!
• AB – Transitional, more like A
• A/B – Mixed, more A than B
• A-B-2C – Change in parent material |
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