?
SOIL PROFILES
Is soil the same all the way down, no matter how
deep you dig?
INTRODUCTION
TOOL KITS #1 AND #2
In this activity you will study a soil profile, which
is a side view, just like your profile is a side view
of your head. You will also begin to understand
how a soil profile is formed.
#1
Four processes form soil
• Additions: items that become soil after chem­
ical, biological, or physical actions, such as
grass clippings, leaves, plant residue, dead
roots, compost
D
IT O
o Pencil or pen
SOIL FORMATION PROCESSES
Unscramble the letters of the four processes that
form soil.
• mafsotnoitranr
• sonraltnoactsi
• Removals: things that leave the soil, usually
with water, such as salts, nitrates, phosphor­
ous, and even soil (that is eroded)
• amrvesol
• Translocations: things that are often moved
down through the soil profile, such as iron
oxide, calcium carbonate, clay minerals
SOIL HORIZONS
• tddsniioa
A typical soil has five horizons (layers), which
are labeled with the letters O, A, B, C, and R.
• Transformations: things that are changed
due to chemical, biological, or physical
actions such as hardening, decomposition,
mineralization
O Surface horizon made
of fresh decaying plant
resdue
ATopsoil contains humus,
roots, and organisms;
lacks structure or is
granular
FIGURE 1.
Primary Layers
of a Soil Profile
Courtesy USDA NRCS
B Subsoil; clays accumu
late, structure forms,
some roots, and leached
materials
CParent material from which the soil was made;
could be weathered bedrock but is not consid­
ered a soil (yet)
Drawing by J. Harsh
Solid rock called bedrock (layer R, not shown)
underlies the parent material.
29 PURDUE EXTENSION
o Vanilla wafers
SOIL HORIZONS
o Granular sugar
Use the horizon definitions and Figure 1 to label
each of the following characteristics of the hori­
zons using the letters for the horizons (O, A, B,
C). You may use any letter more than once, and
one of the answers is a word, not a letter.
o Rock candy
#3
A
D
IT O
D
IT O
#2
Layer with parent material
Underlying rock below the other horizons
Layer still contains fresh decaying plant
residue
Layer where clays accumulate
Soil structure becomes more developed
Layer where humus accumulates, making
it darker
TOOL KIT #3A
Make Your Own Soil Profile
MAKE YOUR OWN SOIL
PROFILE
• Prepare the index card
with a title, place to
write the location of
your sample, and places
for your four soil horizon
samples (see Figure 2).
• Find a place that has
not been disturbed by
excavation or filling
from construction.
SOIL STUDY
Collection Location
surface
1” deep
6” deep
12” deep
It is best to find a farm
FIGURE 2.
field, woods, or pasture
Soil Study Card
area that has no evidence
of digging, filling, or
construction.
Be sure you have permission to dig.
o Pen or pencil
Do not dig around your house; that soil has
been disturbed.
o Shovel, trowel, or spade
o Soil from a garden or crop field
o Index card, 4x6 or larger, or card stock
o Pen or marker
o Double-sided tape or carpet tape
TOOL KIT #3B
Make Your Own Tasty Soil Profile
o Index card, 4x6 or larger, or card stock
o Double-sided tape or carpet tape
o Grated coconut, about 1 tablespoon
o Green food coloring
• Dig a hole. Dig until you see at least one
change in color or texture in the soil.
• Attach a strip of carpet tape or double-sided
tape to the right of each arrow.
• Collect samples from the surface, right under
the surface of the soil and at depths of 6
inches and 12 inches.
Pull the top cover off the double-sided tape.
Collect the sample.
Attach the sample to the tape.
• Complete Table 1 to describe the characteris­
tics of the sample you collected at each level.
o Bowl and spoon
Color
o Oreo cookie
Moisture level
o Gummy worms
Texture (how it feels) PURDUE EXTENSION 30
B
D
IT O
#3
MAKE YOUR OWN TASTY SOIL
PROFILE
The soil profile can be made on an index card as
in Do It #3A, or layer the different horizons from
the bottom up in a clear jar.
• Prepare the index card
with a title and places
for your four soil horizon
samples (see Figure 3).
• Attach a strip of carpet
tape or double-sided tape
to the right of each
horizon.
• Create the soil samples
and attach to the tape at
the following levels:
Surface litter, surf grass:
Mix the coconut and a
FIGURE 3. couple drops of the green
Soil Study Card
food coloring.
Courtesy
USDA NRCS
Organic matter: The top of the Oreo cookie
(cream filling removed), finely ground.
Topsoil: Mix the bottom of the Oreo cookie
(cream filling removed) with half a vanilla
wafer and some gummy worms in the bowl.
(A little bit of the remaining green coconut is
fine in this.)
Subsoil: A vanilla wafer, finely ground.
Parent material: Mix a ground-up vanilla
wafer, a little ground and/or lightly broken
rock candy, and some granular sugar.
More complete instructions, and information
about what each item represents, are available
in the Edible Soil Profile activity by Doug Wolf
available at the Indiana 4-H Soil and Water
Science project website: www.four-h.purdue.edu/
Natural_resources/Projects/soil&water. Edible
soil profiles can make a great interactive
demonstration!
LIFE SKILLS
• Acquiring knowledge
• Thinking critically
TABLE 1.
Level
Color
How it Feels (check one)
Gritty Smooth Sticky
Moisture (check one)
Dry
Damp
Surface
1 inch deep
6 inches deep
12 inches deep
31 PURDUE EXTENSION
Moist
Wet
at
ch
DIG DEEPER
Share What Happened:
• Is soil the same when you dig a hole 1 foot or
2 feet down?
• What causes soil differences?
Apply:
• What are soil horizons?
• Why are soils different at different horizons?
Generalize to Your Life: How might soil dif­
ferences affect someone who is building a house
or planting a garden?
NOTES:
PURDUE EXTENSION 32
• Make a soil monolith that shows a soil
profile using How to Make Miniature Soil
Monoliths (AY-234-W), available at Purdue
Extension’s Education Store,
www.edustore.purdue.edu; search
monolith or AY-234-W.