Monday (1/23/2012)
Let’s Get Dirty
Today’s Agenda:
1. Journal Question: Why is soil
composition important?
2. *Lecture I: Soil – Foundation of
Land Ecosystems
3. Final Exam next Monday (100
Questions) – Good Luck!
4. Free Response Questions next
Tuesday (2 Questions) –Good
Luck!
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2004 AP Environmental
Exam Report for Perspective
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Multiple-Choice Portion of Exam
Fundamental Principles & Concepts:
25 Questions
Human Population: 12 Questions
Resource Distribution & Use: 13
Questions
Environmental Quality: 24
Questions
Global Changes: 12 Questions
Social & Economic Forces: 13
2
Questions
2004 AP Report Environmental
Exam for Perspective
Free-Response
Heavy Metals In Seafood
Wind Power Cost Analysis
Radioactive Isotopes-Waste
Soils-Analysis & Conservation
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Soil Particles are Quite Small
In fact, one could say they are mini
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Soil: Foundation for
Land Ecosystems
A. Soil & Farmland
1. 90% of the world’s food comes
from land-based agricultural
systems, and the percentage is
growing as the ocean’s fish and
natural ecosystems are increasingly
depleted.
2. As the world’s population
moves beyond 7 billion, croplands
and grazing lands are being
increasingly pressed to yield more
crops and other products.
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Agriculture Practices
A. The poor agricultural
practices of the past 50
years have led to the
degradation of 23% of land
used for crops, grazing, or
forestry.
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Agriculture Practices
B. Throughout the world, agricultural soils have
been (and continue to be) degraded by erosion,
the build up of salts, and other problems that
can only undermine future productivity.
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Loss of Prime Farmland
A. In the United States, another kind of agriculture
land loss has occurred:
The loss of prime farmland.
B. This is happening because farmlands are usually
easy to develop and farmers can often sell
their land to developers at huge profits.
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Productive Soil
A. Detritus feeders and
decomposers constitute a
biotic community of organisms
that not only facilitate the
transfer of nutrients, but also
creates a soil environment that
is most favorable to the
growth of roots.
B. A productive topsoil involves
dynamic interactions among the
organisms, detritus, and
minimal particles of the soil.
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Soil
A. Soil covers much of the land on
Earth. It is made up of minerals
(rock, sand, clay, silt), air, water,
and organic material (matter from
dead plants and animals).
B. Soil provides a substrate for
plants (roots anchor in soil), a
source of food for plants, and a
home for many animals (insects,
spiders, centipedes, worms,
burrowing animals, bacteria, and
many others).
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Someone that studies soil is called…
Pedologist
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Soil Formation
A. Soil Formation: Soil is formed slowly as rock
(the parent material) erodes into tiny pieces
near the Earth's surface. Organic matter
decays and mixes with inorganic material (rock
particles, minerals and water) to form soil.
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Soil Horizons
A. Soil Horizons (layers): Soil
is made up of distinct
horizontal layers; these
layers are called horizons.
B. They range from rich,
organic upper layers
(humus and topsoil) to
underlying rocky layers (
subsoil, regolith and
bedrock).
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Soil Profiles:
The process of soil formation creates distinct
horizontal layers of soil:
O Horizon: Humus (surface litter, decomposing plant
matter). Humus = residue of partly decomposed
organic material.
A Horizon: Topsoil. (mixed humus and leached mineral
soil)
E Horizon: Zone of leaching (less humus, minerals
resistant to leaching)
B Horizon: Subsoil (accumulation of leached minerals
like iron and aluminum oxides)
C Horizon: Weathered parent material (partly brokendown minerals; glacial deposits, etc.)
-A vertical slice through the different horizons is
called the soil profile.
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
O Horizon
O Horizon - The top, organic
layer of soil, made up mostly
of leaf litter and humus
(decomposed organic matter).
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A Horizon
A Horizon - The layer called
topsoil; it is found below the O
horizon and above the E horizon.
(1) Seeds germinate and plant
roots grow in this dark-colored
layer.
(2) It is made up of humus
(decomposed organic matter)
mixed with mineral particles.
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E Horizon
E Horizon - This eluviation
(leaching) layer is light in
color; this layer is beneath the
A Horizon and above the B
Horizon.
(1) It is made up mostly of
sand and silt, having lost
most of its minerals and clay
as water drips through the soil
(in the process of eluviation).
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Tuesday (January 24)

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Today’s Agenda:
(1) Journal Question:
What is humus?
(2) What is eluviation
*(3) Soil Horizons
Continued & Soil Textures
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B Horizon
B Horizon - Also called the
subsoil - this layer is beneath
the E Horizon and above the C
Horizon.
(1) It contains clay and mineral
deposits (like iron, aluminum
oxides, and calcium
carbonate) that it receives from
layers above it when
mineralized water drips from
the soil above.
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C Horizon
C Horizon - Also called regolith:
the layer beneath the B Horizon
and above the R Horizon.
(1) It consists of slightly
broken-up bedrock. Plant
roots do not penetrate into
this layer; very little organic
material is found in this layer.
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R Horizon
R Horizon - The unweathered rock (bedrock)
layer that is beneath all the
other layers.
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Soil Horizons
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Soil Texture
A. All soils exist in layers and
can be characterized by their
texture.
B. Soil texture; as rock
weathers, it breaks down into
smaller and smaller
fragments.
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Soil Texture
C. You can see the individual rock particles
in sand, and you can see finer particles in
silt, and clay is a gathering of the smallest
particles.
D. Sand, Silt, Clay (large to small)
E. Sand, silt, and clay particles constitute
the mineral portion of the soil.
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Soil Properties
A. Soil texture, porosity (a measure of
the volume of pores or spaces per
volume of soil), and permeability
(1) The rate at which water and air
move from upper to lower layers of soil,
determines a soil’s water holding
capacity, aeration or oxygen content
(the ability of air to move through the
soil), and workability (how easily the
soil can be cultivated).
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Loam
A. A portion that is commonly
found in soil consists of roughly
40% sand, 40% silt, and 20%
clay.
B. A soil with these proportions is
called loam.
C. Loams are the best soils for
growing most crops because
they hold lots of water, but
not too tightly for plant roots
to absorb.
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Sandy Soils
A. Sandy soils are easy to work,
but water flows rapidly
through them.
B. They are useful for growing
irrigated crops or those with
low water requirements,
such as peanuts and
strawberries.
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Soil & Plant Growth
A. For their best growth, plants
need a root environment that
supplies optimal amounts of:
1. Minerals
2. Water
3. Oxygen
4. The pH (relative acidity)
and salinity (salt
concentration) of the soil are
also critically important.
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Acidic Soils
A. The uptake of nitrogen and phosphorus by
plants is reduced in acidic soils with a pH
below 5.5 and severely reduced in soils with a pH
of 4 or lower.
B. When soils are too acidic, the acids can be
partially neutralized by an alkaline substance,
such as lime.
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Alkaline Soils
A. In dry regions such as much of
the western and southwestern
United States, rain does not
leach away calcium and other
alkaline compounds, so soils
in such areas may be too
alkaline (ph above 7.5) for
some crops.
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Acid Rain’s Effect on Soil
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A. Burning fossil fuels,
especially coal, releases sulfur
dioxide and nitrogen oxides
into the atmosphere.
B. These gases form acidic
compounds that return to the
earth’s surface as acid
deposition.
C. As acidic rain or melted acidic
snow infiltrates the soil, the
result is a loss of soil fertility,
which can reduce crops and
tree growth, making them
more vulnerable to drought,
disease, and pests.
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Soil Fertility
A. Soil fertility, the soil’s ability to
support plant growth, often
refers specifically to the
presence of proper amounts of
nutrients.
B. Farmers speak of a given soil’s
ability to support plant
growth as the tilth of the soil.
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Leaching
A. Nutrients may literally be
washed from the soil as
water moves through it, a
process called leaching.
B. Leaching not only lessens
soil fertility, but also
contributes to pollution when
materials removed from the soil
enter waterways.
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Wednesday (1/25/2012)
Today’s Agenda:
A. Silent Period:
B. Work on Study Guide Questions 1-45.
C. AP Exam on Monday (100 Questions)
1/30/12
D. Two Essay Prompts on Tuesday
1/31/12
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Thursday (1/26/12)
Today’s Agenda:
(1) No Talking (-5 or +5)
(2) Be in your assigned seat. (-5)
(3) What is loam?
(4) Finish Soil Lecture III
(5) Work on Revised Study Guide for
Final Exam on Monday –Prepare to
stay late (make appropriate travel
arrangements)

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In the News 2012


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Solar flare is a bright and bold ball
of energy that is released from the
surface of the sun
A solar flare produces radiation
that is hazardous to humans.
37
Soil Development
A. Soils develop and mature
slowly.
B. It can take 200 to 1,000 years
to develop an inch (2.5 cm)
of topsoil (A horizon).
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Soil Development
C. Well-developed soil profiles,
in which distinct O,A,B, and C
horizons are visible, are
characteristic of older, wellestablished terrestrial
ecosystems.
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Soil Fertility
A. A fertile soil that produces
high crop yields has a thick
topsoil layer with lots of
humus, which helps topsoil
hold water and nutrients taken
up by plant roots.
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Topsoil Color Indications
A. The color of the topsoil often tells a lot
about how useful a soil is for growing
crops.
B. Dark brown or black topsoil is
nitrogen rich and high in organic
matter. (Indicative of fertile soil)
C. Gray, bright yellow, or red top soils are
low in organic matter and need
nitrogen enrichments to support
most crops.
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To support a good crop, the
soil must have the following:
1. Have a good supply of nutrients and a
good nutrient holding capacity.
2. Allow infiltration, have a good waterholding capacity, and resist evaporative
water loss.
3. Have a porous structure that permits
good aeration.
4. Have a pH near neutral (pH 7)
5. Have a low salt content.
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Soil Degradation
A. When key soil attributes required
for plant growth or soil ecosystem
services deteriorate over time, the
soil is considered degraded.
B. How is topsoil lost? The most
pervasive and damaging force
is erosion, the process of soil
and humus being picked up
and carried away by water or
wind.
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Soil Degradation
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C. Farming, logging, construction,
overgrazing by livestock, off-road
vehicles, deliberate burning of
vegetation, and other activities that
destroy plant cover leave soil
vulnerable to erosion.
D. Such human activities can speed
up erosion and destroy in a few
decades what nature took
hundreds and thousands of years
to produce.
45
Soil Erosion
A. Most soil erosion is caused by moving
water.
B. Three types of water erosion:
1. Sheet Erosion: occurs when surface
water moves down a slope or across a
field in a wide flow and peels off fairly
uniform sheets or layers of soils.
2. Rill Erosion: the surface water forms
fast-flowing little rivulets that cut small
channels in the soil.
3. Gully Erosion: Rivulets of fast-flowing
water join together and with each
succeeding rain cut the channels wider
and deeper until the become ditches or
gullies.
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The five golden rules for
soil conservation
A. Keep the soil covered.
B. Using minimal or no tillage.
C. Use mulch to provide nutrients for
crops (not fertilizers)
D. Maximizing biomass production.
E. Maximizing biodiversity.
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Evaluating Ecosystem
Services (ES)
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Soil Profiles in Various Ecosystems
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What do you think?
A. How do the soil profiles in plowed
farmland differ from those of
unplowed natural areas?
B. What properties of soils change by
the act of plowing, both in the
short term and in the long term?
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The Rock Cycle
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The Rock Cycle
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Make Sure You Clearly
Understand:
A. Soil and Soil Dynamics
(Rock cycle; formation;
composition; physical and
chemical properties; main soil
types; erosion and other soil
problems; soil conservation)
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