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AP Environmental
Soils Study Guide
Review Chapter 10 (sections 1, 2 & 4)
Key ideas from the reading:
Case Study (page 198 - Farming the Cerrado
(What are the costs and benefits?)


South America the fastest growing agricultural area of the
world
Soils
o Acidic and poor in nutrients
o High in Iron
o Warm humid climate
 Pests
 Rapid breakdown of organic material
Benefits
Costs
New Varieties of soybeans
 Genetically modified crops
 Brazil is now the largest exporter
 Main Market -----> China
 BioPlastics
Arc of Destruction –
Encroachment on the Amazon
 Land Dries rapidly
 Increases in Drought
 Increasing large industrial farms
 Conflict between small local farms and
large agriculture industry
Chapter 10.1 Farming- p. 199 – What is Soil

Soils are composed of mineral grains (sand, silt and clay), organic matter, organisms, water
and air
o Problem: Soil is renewable at an average rate of 1mm/year. Soil loss can be as high
as 25mm/year on bare unprotected soil

The Big Six – Soil composition
o Sand and gravel
o Silts and clays
o Dead Organic material
o Live Organic material
o Water
o Air.
o
Really, Split into three:….
1. Particle Size
2. Organic Matter
3. Abiotic Factors
Particle Size <-------> see diagram
 Abundant clays make soil sticky and wet.
 Abundant organic material and sand make the soil soft
and easy to dig.
AP Environmental
Soils Study Guide
 Sandy soils drain quickly, often depriving plants of moisture.
 silty soils are ideal for growing crops, but they are also light and blow away easily
 Compacted soils have few air spaces, making soil fauna and plants grow poorly.
o
o
Soil Texture - Texture helps determine
whether rainfall drains away quickly or
ponds up and drowns plants. Loam soils
are usually considered best for farming
because they have a mixture of clay, silt,
and sand
Color - reddish soils, including most
tropical soils, often are colored by ironrich, rust-colored clays, which store few
nutrients for plants. Deep black soils, on
the other hand, are rich in organic
Si
San
material, and thus rich in
nutrients.
o Organic Matter.
 Living: One gram of
soil can contain
hundreds of soil
bacteria and 20
meters of tiny strands
of fungal material.
 Dea
d: The bacteria and
fungi start the process
See p. 201
of decomposing
organic matter. Further digestion and decomposition
occurs when other animals eat the bacteria and fungi.
 (The composition) affect soil fertility, erodibility and other factors

The health of the soil ecosystem depends on environmental conditions, including:
 climate,
 topography,
 parent material (the mineral grains or bedrock on which soil is built),
 frequency of disturbance.

Soils vary in texture, color and horizon development.
o
o
o
o
O for organic – Decomposing leaves, fungi and bacteria
A (Topsoil) – Organic matter (roots, worms etc.) and minerals
E (Eluviated) - Mainly sands and very few nutrients. May not be present in all soils.
B (Subsoil) – Clays that hold soluble nutrients.
AP Environmental
Soils Study Guide
Erosion: The carrying away of materials by wind, water or ice. Wind and water erosion are the
primary causes of degradation. Additional causes include: Salt accumulation from using sea water
and physical deterioration, such as compaction from heavy machinery.
Types:
o Sheet Erosion – Water washes away a thin layer of the soil
o Rill Erosion – Water creates channels in the soil
o Gully Erosion – A larger version of rill erosion that cannot be removed by tilling the soil.
o Wind Erosion – Usually occurs when the plant and surface litter have been removed.
Practice Questions
A large number of practice questions can be found online
Our Text!
http://glencoe.mheducation.com/sites/0021364567/student_view0/chapter10/practice_quiz.html
1 . A variety of pesticides are used and they differ from each other in
A. the type of organism killed.
B. the degree of toxicity.
C. the degree of persistence in the environment.
D. all of the above
Another Environmental Science Text
http://glencoe.mheducation.com/sites/0003192012/student_view0/chapter13/practice_quiz.html
Mechanical weathering of soil
A. occurs quickly.
B. does not change the chemical nature of the rock.
C. changes the chemical makeup of the parent material.
D. is not important in soil production.
Basic Earth Science Text –Check out the section 1 and 3 practice tests too!
http://glencoe.mheducation.com/sites/0078778026/student_view0/unit2/chapter7/section_2_selfcheck_quiz-eng_.html
Section 2 Self-Check Quiz-Eng.
1. A soil's composition is dependent on weathering because __________.
Need a Hint?
A. it makes the soil more fertile
B. it contributes sediment to the soil
C. it keeps the soil moist
D. it moves the topsoil to other areas where it is more needed