Soil
Science
Chapter 14 (R&B)
Chapter 14 (Miller)
Ch 21 (R&B)
Some diagrams and information in this presentation have been used and/or
modified with permission from Dr. Greg Pillar, Soil & Environmental
Science professor at Queens University in Charlotte, NC.
Your Responsibility!!!
SOIL READING GUIDE
Major Soil Groups
Soil Problems
… in both R&B and Miller books!
The Rock Cycle
IGNEOUS
ROCK
MAGMA
Erode & Weather
Melt
METAMORPHIC
ROCK
SEDIMENT
SEDIMENTARY
ROCK
What is SOIL????
The relatively thin surface layer of the
Earth’s crust consisting of mineral and
organic matter.
Soil is not DIRT!
Q: What’s the difference
between soil and dirt?
A.Location,
location, location!
Dr. Greg Pillar, Queens College
The 5 Soil-Forming Factors
Formed from parent material (bedrock)
that’s slowly broken down through
weathering processes.
• climate (water, wind, temperature)
• biology (macro- and microorganisms, plants)
• relief (topography)
• parent material (rocks/minerals)
• time
Which is the MOST important??
CLIMATE!!!
What is Soil?
How would you describe soil?
Color
• Texture
Texture
Dr. Greg Pillar, Queens College
Why the color?
http://www.msstate.edu
http://www.cs.cmu.edu
http://www.mii.org
Hematite:
red
Goethite:
yellowish brown
Ferrihydrite:
reddish brown
http://www.beg.utexas.edu
http://www.pitt.edu
Calcite:
off white
Quartz:
white
http://www.organicgardeninfo.com
Organic matter:
black
Dr. Greg Pillar, Queens College
Soil Color Variation
• Did you know ??????
There are more than 20,000
different soil types in the
United States
….and each one tastes
different
Dr. Greg Pillar, Queens College
Dr. Greg Pillar, Queens College
Soil Composition
Mineral matter
comes from
parent material
Water
(~25%)
Air
(~25%)
Humus
(~5%)
Mineral
(~45%)
Air & Water
percents are
interchangeable
Humus is
organic matter!
Soil Composition continued…
Mineral Matter
– Provides nutrient
minerals for plants
– Provides pore space
for water & air
Older soils are:
– More weathered
– Lower in certain
essential nutrient
minerals
Humus: black/dark brown organic material
remaining after decomposition
– Leaf litter, animal dung, & decaying organisms
– Increases the soil’s water-holding capacity by acting
like a sponge
Soil Composition continued…
Porosity
POROSITY =
amt of soil pore spaces
Pore spaces occupy ~50% of a
soil’s volume
– Filled with varying proportions
of soil water and soil air
Soil Air contains the same
gases as atmospheric air, but
in different proportions.
– More CO2 and less O2
(from organism respiration)
– Some bacteria need nitrogen
(why??)
– The CO2 can accelerate
weathering
• CO2 + H2O  H2CO3
(carbonic acid)
Soil Composition continued…
As water infiltrates the soil, it can carry
dissolved materials with it.
Leaching: Removal of dissolved
materials from the soil by water
percolating downward
Illuviation: Deposition of leached
material in lower layers
– Some substances completely leach out of
the soil because they’re so soluble that they
migrate right down to the groundwater.
Observe this SOIL PROFILE through soil
O: Organic material
(may be absent)
A: Topsoil - Organic
material & mineral
grains
E: Leached zone
(may be absent)
B: Subsoil – rich in
clay, iron, aluminum
C: Weathered bedrock
Soil layers are
horizons and
assigned letters
R: Bedrock
(parent material)
Soil Pedon
Dr. Greg Pillar, Queens College
Soil Color by Horizon
A horizon: organic coatings
B horizon: Iron coatings
Fun Fact: It takes
100 to 600 years to
form an inch of
topsoil.
C horizon: little coating
Dr. Greg Pillar, Queens College
http://nesoil.com
Soil Color – Variation by Geography
Red soils:
Southeast US
Dr. Greg Pillar, Queens College
Soil Color – Variation by Geography
Brown/black soils:
Midwest
Dr. Greg Pillar, Queens College
Soil Color – Variation by Geography
White (gypsum) sands:
New Mexico
Dr. Greg Pillar, Queens College
http://www.scienceclarified.com
Soil Organisms
Ex: bacteria, fungi, algae,
microscopic worms, protozoa,
plant roots, insects, earthworms,
moles, snakes, groundhogs, etc.
Soil organisms provide several
Ecosystem Services (important
environmental functions).
–
–
–
–
–
maintaining soil fertility
preventing soil erosion
breaking down toxic materials
cleansing water
affecting atmospheric composition
Earthworms & Ants:
– Cycle minerals
– Aerate the soil
– Decomposing corpses
contribute organic matter
– Assist plants in reproduction
by burying seeds
Mycorrhizae
– Symbiotic relationship
between fungi and the roots
of vascular plants
– Fungus absorbs nutrients
from the soil, and provides it
for the plant.
– Plant produces food
(photosynthesis), and
provides it for the fungus.
Dr. Greg Pillar, Queens College
Physical
Soil Properties
PHYSICAL properties:
Texture (%sand, silt, clay)
Porosity & Permeability
Ionic Charge
Physical Property: Texture
Texture is determined by its % sand,
silt, and clay.
Loam:
ideal for
agricultural
soil
Texture determines the
type of soil, and the
soil’s properties.
Soil Components
Q: What did the shy
pebble say to the big
rock?
A. Do you think I’ll ever be a
little boulder?
Dr. Greg Pillar, Queens College
http://school.discoveryeducation.com
Fine Texture - Clay
Dr. Greg Pillar, Queens College
https://www.soils.org/lessons
Course Texture - Sand
Dr. Greg Pillar, Queens College
https://www.soils.org/lessons
Soil Texture
The relative portions of sand, silt, and clay-sized particles
Sand: 2.0 – 0.05 mm
Silt: 0.05 – 0.002 mm
Clay: < 0.002 mm
Dr. Greg Pillar, Queens College
Soil Texture Diagram Practice
What type of soil has:
(1) Loam
(2) Sandy clay
(3) Silty clay
loam
1. 20% clay, 40% silt, 40% sand
2. 40% clay, 10% silt, 50% sand
3. 30% clay, 60% silt, 10% sand
Find the % of
each particle at:
1. A
2. B
3. C
A
B
60%clay, 20%silt, 20%sand
30%clay, 40%silt, 30%sand
10%clay, 30%silt, 60%sand
C
Why is Soil Texture Important?
Property
Sand
Silt
Clay
Water holding
Low
Med-high
High
Aeration
Good
Med
Poor
Nutrient supplying
Poor
Med-high
High
Pollutant Filtering
Low
Med
High
SOIL TOUCHY
FEELY TIME!
Physical: Porosity & Permeability
again… Think it is important??
Porosity
Definition?
– amt of soil pore spaces
Permeability
Definition?
– ability of water to percolate through
____ porosity = ____ permeability
Physical: Ionic Charge
Soil minerals are often present as ions.
Minerals ions are either positively or
negatively charged.
Clay particles have mostly negative charges
on their outer surfaces.
– Positively charged mineral ions are attracted to
the soil particles and are held for plant use.
• potassium K+ and magnesium Mg2+
– Negatively charged mineral ions are repelled by
the soil particles and are washed away from roots.
• nitrate NO3-
Physical Characteristics
(review)
Why would 100% sand be undesirable for plants?
Why would 100% clay be undesirable for plants?
Answer SAND / SILT / CLAY for the following:
– A soil with a lot of _____ would have good drainage,
but poor nutrient-holding characteristics.
– A soil with a lot of _____ would have poor drainage,
but good nutrient-holding characteristics.
– A soil with a lot of _____ would have low porosity.
– A soil with a lot of _____ would have high permeability.
Demonstration
Two soil cores
Bottom of core
contains filter
paper and
cheese cloth
Demonstration
Two unknown
liquids
Liquids passed
through soil
cores
Pollutant #1
Leachate
collected below
Pollutant #2
What did you observe?
Demonstration
What happened to
the original liquids?
Soil
Soil
What does
a change or no change
in color mean?
To what extent did the
soil contribute to
this change?
Adsorption of Organic Dyes
HO
Cl
Cl
OH
O
S
O
O
Chlorophenol red
Cl-
N
N
S+
CR-
N
Methylene blue
MB+
CRMB+
MB+
MB+
MB+
CR-
MB+
MB+
MB+
MB+
MB+
MB+
Soil
CRCR-
Chemical Property: Acidity
Most soil pH is 4-8. Plants are happiest at 6-7. 
Plants are affected by soil pH.
(1) The solubility of certain nutrient minerals varies with
differences in pH
• Low pH = Al & Mn are more soluble, and can be absorbed in
toxic amounts.
• High pH = some salts are less soluble, and are less available to
the plants.
(2) Soil pH affects the leaching of nutrient minerals.
• Acidic soil = positively charged ions are less soluble and are
unavailable for plants.
http://www.wvu.edu/~Agexten/hortcult/turf/liming.htm
Soil Conditioners (Lime)
CaCO3 or MgCO3
Soil amendment / conditioner… not a fertilizer!
Important functions:
1.
2.
3.
4.
5.
Corrects soil acidity
Adds important plant nutrients— Ca & Mg
Reduces solubility & toxicity of certain elements in
the soil
Al, Mn, Fe
This toxicity could reduce plant growth under acid
conditions.
Promotes availability of major plant nutrients.
Zn, Cu, P
Increases bacterial activity & mutualistic
relationships.
http://www.wvu.edu/~Agexten/hortcult/turf/liming.htm
Soil Conditioners (Compost)
Decayed organic matter
Replaces some nutrients
Improves soil structure
– The soil becomes more porous,
increasing air circulation and the ability of
the soil to absorb and hold moisture.
– Makes the soil more spongy!
What is Soil?
Why is Soil Important?
Soil supports
life
Fun
FunFact:
Fact:There
1 teaspoon
are more
of
living
goodorganisms
soil contains
in amore
cubic
than
foot 1
ofmillion
soil then
bacteria!
all of
China!
Dr. Greg Pillar, Queens College
http://www.Istockphoto.com
L. Clarke and Corbis, 2008
Soil stores important nutrients
Nitrogen (NH4+) (ammonium)
Potassium (K+)
Calcium (Ca2+)
Magnesium (Mg2+)
Phosphorus (P) (PO4-3)
(PO4-3 combines with +charged
particles in soil)
Dr. Greg Pillar, Queens College
http://www.lesco.com/
Soil Holds Water
Dr. Greg Pillar, Queens College
Soil provides support for buildings
Dr. Greg Pillar, Queens College
http://www.pbase.com
Soil filters, buffers, detoxifies….
Soil
Dr. Greg Pillar, Queens College
http://extension.missouri.edu
Inputs/Outputs
Are these Soil Inputs or Soil Outputs?
Mass Movements (landslides, etc) O
Precipitation I
Parent Material I
Leaching O
Infiltration I
Uptake by Plants O
Organic Matter I
Energy I
Transfers/Transformations
Recall:
Transfers simply MOVE things…
they reorganize the soil!
Transformations CHANGE things…
they alter the soil’s makeup in some way.
Are these Soil Transfers or Transformations?
Decomposition transformation
Erosion transfer
Deposition transfer
Weathering transformation
Nutrient Cycling transformation
Soil Pollution
Part II
Chapter 21 (R&B)
Soil Pollution
= any physical or chemical change in soil that
adversely affects the health of plants and
other organisms living in and on it.
Many soil pollutants…
– ARE MOBILE!
• move into groundwater, surface water, or air
– ARE PERSISTENT!
• seep into tiny cracks called micropores and adhere to the
soil particles
– COME FROM FERTILIZERS / PESTICIDES!
– CAN ACCUMULATE!
Sustainable Agriculture practices can help…
…more on this later…
Salinization of Irrigated Soil
Irrigation water soaks through the soil area where
the plant roots grow, adding to the existing water.
The additional irrigation water causes the
underground water-table to rise, bringing salt to
the surface.
When the irrigated
area dries & the
underground water
table recedes, salt
is left on the
surface soil.
Each time the area
is irrigated this
salinity process is
repeated.
ALL IRRIGATION WATER CONTAINS SOME DISSOLVED SALTS.
Salinization of Irrigated Soil
This is in Australia – occurred not from
irrigation, but from lack of water-loving plants.
Extra water flows through the
soil, mixing w/ salt underground,
and bringing it to the surface.
Irrigation salinization is basically
the same concept, and the ground
would look just like this.
Effects of Salinized Soil on Plants
Normally, the water
concentration inside
plant cells is lower than
that in the soil resulting
in a net movement of
water into the root cell.
When soil contains a
high amount of salt, its
relative water
concentration can be
lower than the water
concentration inside
cells. This causes water
to move out of the roots
into the soil, even when
the soil is wet.
Salinization Lab 
1. Answer Prelab Questions
2. Gather Materials
– 4 ziploc bags
– 20 radish seeds
– 4 paper towels
3.
4.
5.
6.
Follow instructions on the lab sheet
BE SURE TO LABEL YOUR BAGS!!!
Leave them in the box in the front.
We’ll inspect their germination progress
and take data over the next week.
Soil Remediation
Until recently, the only way to remove
soil contaminants was to…
DIG
IT UP
& INCINERATE IT!
Why is this a bad thing to do??
– Impractical, kills all beneficial organisms,
creates waste, expensive…
Soil Remediation Techniques
Small Groups: define these, then make a
pro/con list. Use your book if necessary.
Dilution
– Add lots of water; leach out pollutants
Vapor extraction
– Inject air into soil to remove volatile organic compounds
Bioremediation
– Use microorganisms to degrade organic contaminants
(oil, sludge)
Phytoremediation
– Use plants to absorb contaminants such as salts or heavy
metals.
DILUTION: Pump & Treat / Soil Washing
Water
GROUND LEVEL
Extraction well
Pollutant low sorption potential = not attracted to soil
easily washed away
Pollutant high sorption potential = not easily washed
12 - 28
… But what’s the problem here?
GROUND LEVEL
How can this problem be fixed???
Source Identification and Removal !!!!
12 - 30
Bioremediation (Bioventing)
12 - 32
15.06.b
Activities that Threaten Soil
Overgrazing
Erosion Control
Removing vegetation
Soil contamination
Preventing Soil Erosion
• Agricultural: 10% of the worlds best agricultural land
damaged due to soil erosion and overuse over last 50
years.
-
contour plowing
no-till agriculture (no plowing)
terracing slopes
crop rotation - fallow
Your Responsibility!!!
Soil Reading Guide
Major Soil Groups
Soil Problems
Soil Conservation & Regeneration
… in both R&B and Miller books!
Soil Pedon
USDA Soil Profile Activity:
http://soils.usda.gov/education/resources/k_12/lessons/profile/