Oklahoma Soils
Objective
Students will read to learn how soils are formed and
answer questions about the reading. Students will
answer questions from a chart showing the many
different varieties of soil in Oklahoma Major Land
Resource Areas.
Background
Oklahoma Academic Standards
GRADE 3
Science Process—1.2; 2.1; 3.1,2,3; 4.1,3
Earth Science—3.1,2
Social Studies PALS—1.A.1,2,4,5,7;
2.A.2,B.6,C.7,8,D.10; 3.A.1,2,B.4
Social Studies Content—3.1B,C,E
COMMON CORE
Language Arts—3.RI.1,2,4,5,7,10; 3.RF.3d,4ac;
3.W.2abcd,6,7,8; 3.SL.1abcd,2,4; 3.L.4ad
GRADE 4
Soil covers much of the land on Earth. It is
Science Process—1.2; 2.1; 3.1,2,3; 4.1,2,4
made up of minerals (rock, sand, clay, silt), air, water,
Earth Science—4.1,2
and organic material (matter from dead plants and
COMMON CORE
animals). Soil provides a substrate for plants (Roots
Language Arts—4.RI.1,2,4,7,10; 4.RF.3a,4ac;
anchor in soil.), a source of food for plants, and a
4.W.2abcde,4,6,7,8,9; 4.SL.1abc,2,4; 4.L.4,6
home for many animals (insects, spiders, centipedes,
worms, burrowing animals, bacteria, and many
GRADE 5
others).
Science Process—1.2; 2.1; 3.1,2,3; 4.1,2,4
Soil is formed slowly, as rock (the parent
Earth Science—3.1 (soil layers)
material) erodes into tiny pieces near the Earth’s
COMMON CORE
surface. Organic matter decays and mixes with
Language Arts—5.RI.2,4,5,7,10; 5.3a,4.ac;
inorganic material (rock particles, minerals and water)
5.W2abcde,4,6,7,8,9; 5.SL.1abcd,2,4,5; 5.L.4ac,6
to form soil.
The Natural Resources Conservation Service
GRADE 6
(NRCS) has identified and mapped over 20,000
Science Process—2.1,2; 3.1,2,3; 4.1,2; 5.1,2
different kinds of soil in the United States.
Life Science—5.1a
In Oklahoma, there are over 2,500 different kinds
Social Studies PALS—1.A.1,2,4,C.7,D.10;
of soil. We have a variable climate and many different
2.A.2abcdef,4,6,7,8,9,C.10
kinds of geologic materials across the state. These
Social Studies Content—1.1,2,5; 2.1B; 3.1B
factors and others influence the formation of different
COMMON CORE
kinds of soil. No one individual soil occurs throughout
Language Arts—6.RI.1,2,4,7,10;
every region of the state.
6.W.2abcdef,4,6,7,8,9,10; 6.SL.1abcd,2,4,5; 6.L.4acd,6
Soil formation is influenced by five factors:
geology (parent material), topography, climate, plants
GRADE 7
and animals (organic material), and time. These
Science Process—2.1,2; 3.1,2; 4.1,2,5; 5.1,2
factors give soil profiles their distinctive character.
Earth Science—5.2 (volcanoes)
Color, texture, size and shape of soil aggregates,
COMMON CORE
kind and amount of rock fragments, distribution
Language Arts—7.RI.1,2,4,5,7,10;
of plant roots, pH, and other features are used to
7.W.2abcdef,4,6,7,8,9,10; 7.SL.1abcd,2,4,5; 7.L.4acd,6
characterize soils. After a soil is described and its
properties are determined, soil scientists assign the
GRADE 8
soil to one of 12 taxonomic orders and/or one of many
Science Process—2.1,2; 3.1,2; 4.1,2,5; 5.1,2
suborders. (See “Dominant Oklahoma Soil Orders,”
Earth Science—4.1,2; 5.1,2
included with this lesson.)
COMMON CORE
Language Arts—8.RI.1,2,4,5,7,10;
8.W.2abcdef,4,6,7,8,9,10; 8.SL.1abcd,2,4,5; 8.L.4acd,6
www.agclassroom.org/ok
Vocabulary
agriculture— the science or occupation of
cultivating the soil, producing crops, and
raising livestock
base— any of various compounds that react
with an acid to form a salt, have a bitter taste,
and turn red litmus paper blue
climate— the average weather conditions of a
particular place or region over a period of years
constituent— one of the parts of which a thing
is made up
deficit— deficiency in amount
deposition— the action or process of
depositing
fertile— producing vegetation or crops
plentifully
geologic— having to do with the history of the
earth especially as recorded in rocks
horizon— a distinct layer of soil or its
underlying material in a vertical section of land
humus— a brown or black product of partial
decay of plant or animal matter that forms the
organic portion of soil
irrigation— the act of supplying with water by
artificial means
leach— to pass a liquid through to carry off the
soluble components
mesophytic— plants which are adapted to
neither a particularly dry nor particularly wet
environment
native— natural
organic— of, relating to, or obtained from
living things
subhumid— regions where moisture in
normally less than under humid conditions
but still sufficient for the production of many
agricultural crops without irrigation or dryland
farming. Natural vegetation is mostly tall
grasses.
substrate— the base on which an organism
lives or over which it moves
subsurface— earth material (as rock) near but
not exposed at the surface of the ground
temperate— having or associated with a
climate that is usually mild without extremely
cold or extremely hot temperatures
topography— the shape and height and depth
of the features of a place
variable— able to change : likely to be
changed
Some of our Oklahoma soils are naturally fertile, while
others are very limited in productivity. Each soil type requires
its own care and skillful use by farmers attempting to produce
crops from our soils. In some parts of the state the soil will
support crop growth, while other parts are better for grazing.
Language Arts/Social Studies/Science
1. Read and discuss background and unfamiliar vocabulary.
—Students will discuss unfamilar vocabulary, using
context clues, prior knowledge and dictionaries or other
references to find and explain the meaning.
—Students will determine the main idea of the
background passage, find the key details and explain how
they support the main idea.
—Students will list the five factors that determine soil
formation.
—Students will discuss why Oklahoma has so many
different kinds of soil. (They should consider our location
in the center of the continent.)
2. Show students the Soil Map of Oklahoma, available
online: http://www.ogs.ou.edu/pubsscanned/
EP9p16_19soil_veg_cl.pdf
—Students will find your part of the state on the map.
—Students will discuss what the map tells them about the
soils found in your part of the state.
3. Provide copies of the chart included with this lesson,
“Oklahoma Soils by Land Resource Area.”
—Look through the chart as a class, and determine which
Land Resource Area covers your part of the state.
—Students will answer the Comprehension Questions
included with this lesson.
4. Research: Part of our state is classified as plains and part is
classified as prairie. What is the difference? Students will
write their explanations.
5. Students will select one or more of the Dominant
Oklahoma Soil Orders and work in groups to build models
of them, make posters, produce multimedia presentations
or other means to provide information about them to the
class.
6. Students will use online or library resources to find
information about soil horizons and create models of
them, using breakfast cereal or other common materials.
7. Students will use online search engines or library
references to find soil maps of other states and compare
the diversity of soils in Oklahoma with those in the other
states.
8. Students will gather soils from the school yard, their
www.agclassroom.org/ok
homes and other areas.
—Students will dry the soils on newspapers and label them as to location where they were found.
—Students will sort the soils by color, particle size (Use magnifiers.) and other student-determined criteria.
—Students will produce appropriate graphs to show the results of their investigation.
9. Students will use online search engines or library references to identify and find information about
Oklahoma’s state soil (Port Silt Loam). Students will show what they find in writing.
10.Students will learn and sing the “Soil Order Song:” http://www.youtube.com/watch?v=NGTsl2rOywQ
Extra Reading
Bial, Raymond, A Handful of Dirt, Walker and Co., 2000.
Gardner, Robert, Super Science Projects About Earth’s Soil and Water (Rockin’ Earth Science Experiments), Enslow,
2007.
Lindbo, David, SOIL! Get the Inside Scoop, American Society of Agronomy, 2008.
Nardi, James B., The World Beneath Our Feet: A Guide to Life in the Soil, Oxford, 2003.
Stille, Darlene R., and Hossain and Farhana, Soil: Digging Into Earth’s Vital Resource (Exploring Science: Earth
Science Series), Compass Point, 2005.
Dominant Oklahoma Soil Orders
Alfisols—Alfisols are in semiarid to moist areas. These soils result from weathering processes that leach clay
minerals and other consituents out of the surface layer and into the subsoil, where they can hold and supply
moisture and nutrients to plants. They formed primarily under forest or mixed vegetative cover and are
productive for most crops. In Oklahoma they are found in the central part of the state, mostly east central and
along the eastern part of southern border.
Mollisols—Mollisols are soils that have a dark colored surface horizon relatively high in organic matter. The
soils are base rich throughout and therefore are quite fertile. Mollisols characteristically form under grass in
climates that have a moderate to pronounced seasonal moisture deficit. In Oklahoma they are found throughout
the central part of the state, from the northern border to the southern border.
Aridisols—Aridisols are soils that are too dry for the growth of mesophytic plants. The lack of moisture greatly
restricts the intensity of weathering processes and limits most soil development. Aridisols often accumulate
gypsum, salt, calcium carbonate and other mateirals that are easily leached from soils in more humid
environments. Aridisols are used mainly for range, wildlife, and recreation. Because of the dry climate in which
they are found, they are not used for agricultural production unless irrigation water is available. In Oklahoma
they occur in the Panhandle.
Ultisols—Ultisols are acid forest soils with relatively low native fertility. Most nutrients are concentrated in
the upper few inches. They are found primarily in humid temperate and tropical areas of the world, typically
on older, stable landscapes. Intense weathering and leaching result in a clay-enriched subsoil dominated by
minerals such as quartz, kaolinites and iron oxides. Because of the favorable climate regimes in which they
are typically found, Ultisols often support productive forests. The high acidity and relatively low quantities of
plant-available calcium, magnesium, and potassium associated with most Ultisols make them poorly suited for
continuous agriculture without the use of fertilizer and lime. Oklahoma’s Ultisols are located in the far eastern
part of the state.
Entisols—Entisols are soils that show little or no evidence of horizon development. Entisols occur in areas of
recently deposited parent material or in areas where erosion or deposition rates are faster than the rate of soil
development, such as dunes, steep slopes and flood plains. They occur in many environments. Entisols of large
river valleys and associated shore deposits provide cropland and habitat for millions of people worldwide.
Globally Entisols are the most extensive of the soil orders. In Oklahoma there are Entisols scattered in small
areas all across the state.
Vertisols—Vertisols are clay-rich soils that shrink and swell with changes in moisture content. During dry
periods, the soil volume shrinks, and deep wide cracks form. The soil volume then expands as it wets up. This
shrink/swell action generally prevents formation of distinct, well-developed horizons in these soils. They tend to
be fairly high in natural fertility. Vertisols occupy small percentages of the land in an area that goes diagonally
across Oklahoma from southwest to northeast, with a larger percentage located along the southern border in the
eastern part of the state.
Inceptisols—Inceptisols are soils with minimal horizon development. They are more developed than Entisols,
but still lack the features that are characteristic of other soil orders. Although not found in dry areas, Inceptisols
are widely distributed and occur across a wide range of ecological settings. Land use varies considerably
with Inceptisols. A sizable percentage of Inceptisols are found in mountainous areas and are used for forestry,
recreation, and watershed. Small percentages are located throughout Oklahoma, with a larger concentration in
the west central part of the state.
Oklahoma Soils by Land Resource Area
LAND
MOSTLY LOCATED IN
RESOURCE (COUNTIES)
AREA
SOIL
DESCRIPTION
SOIL
ORDERS
PARENT
MATERIAL
DEVELOPED
UNDER
Canadian
Plains and
Valleys
Cimarron
brown, loamy
Entisols
mid and short
grasses.
High Plains
and Breaks
Cimarron, Texas, Beaver Ellis,
Harper, Woodward
Central
Rolling Red
Plains
Harper, Woods, Woodward, Major,
Dewey, Roger Mills, Custer, Washita,
Beckham, Greer, Kiowa, Harmon,
Jackson, Tillman, Cotton
dark-colored and clay Mollisols
loams
Aridisols
subsoil: moderately
Alfisols
clayey
sandstone
escarpments,
basalt, associated
foot slopes
Permian shales,
mudstones, and
siltstones
mid and short
grasses.
Central
Rolling Red
Prairies
Cross
Timbers
dark to various
shades of red
subsoil: clay to loam
Alfalfa, Grant, Kay, Noble, Garfield,
Blaine, Kingfisher, Logan, Canadian,
Caddo, Grady, McClain, Garvin,
Comanche, Stephens, Jefferson,
Cleveland, Oklahoma, Payne
dark and loamy
subsoil: clayey to
loamy
Alfisols
Entisols
Inceptisols
Mollisols
limey
unconsolidated
loams, silts,
caliche
Mollisols
Entisols
Alfisols
Permian shales,
tall grasses
mudstones,
sandstones and/or
alluvial deposits
Grady, Oklahoma, Stephens, Garvin,
Cleveland, Lincoln, Logan, Love,
Payne, Creek, Osage, Okfuskee,
Seminole, Pawnee
light-colored, sandy
subsoil: reddish
Alfisols
Inceptisols
various sandy
materials
Kay, Osage, Pawnee, Nowata,
Craig, Rogers, Nowata, Washington,
Tulsa, Mayes, Wagoner, Okmulgee,
Muskogee, Hughes, McIntosh,
Pitsburgh, Coal
deep, dark-colored
subsoil: clay
Mollisols
Alfisols
Entisols
shales,
sandstones,
limestones
Garvin, Pontotoc, Murray, Johnston,
Marshall, Bryan, Choctaw
dark and loamy to
Alfisols
clayey; thin and stony Mollisols
(Arbuckles)
Vertisols
Ozark
Highlands–
Boston
Mountains
Delaware, Cherokee, Adair,
Sequoyah, Ottawa
brown to light-brown, Ultisols
silty
Inceptisols
subsoil: reddish clay Entisols
Ouachita
Mountains
LeFlore, Latimer, Pushmataha, Atoka, light-colored, acid,
McCurtain
sandy, loamy
subsoil: clayey (
Hughes, Pittsburgh, Pushmataha,
Latimer, LeFore
loamy, rocky, well
drained or very deep
and loamy
Altisols
Ultisols
Inceptisols
McCurtain, Choctaw, Atoka, and
Bryan Counties
light-colored, acid,
sandy
subsoils: clay-loam
to clay
Ultisols
Alfisols
Vertisols
Bluestem
Hills–
Cherokee
Prairies
Grand
Prairie–
Arbuckle
Mountains
Arkansas
Ridge and
Valley
Coastal
Plain
mid and short
grasses
Inceptisols
Ultisols
Alfisols)
post oak, blackjack
oak, hickory
forests with prairie
openings
tall grasses
shales,
limestones;
Precambrian
granites
(Arbuckles)
tall grasses, mid
grasses, scrub
oaks, cedars, and
shrubs
cherty limestones
(Ozarks) and
sandstones and
shales (Boston
Mountains)
oak-hickory-pine
forests and tall
grasses
sandstones and
shales
oak-hickory-pine
forests
steep slopes
and ridges or on
gentle slopes and
shales in valleys
oak-pine forests
sandstones
pine-oak (east) and
oak-hickory (west)
forests
Source: Carter, Bryan J., and Mark S. Gregory, Department of Plant and Soil Sciences, Oklahoma State University, http://www.ogs.
ou.edu/pubsscanned/EP9p16_19soil_veg_cl.pdf
Name_____________________________________________________
Comprehension Questions
Use the Oklahoma Soils by Land Resource Area chart and the information about soil orders to answer the
following questions:
1. Write the name of the county where your school is located. Locate your county on the map of Oklahoma
included with this lesson.
2. Based on the Oklahoma Soils and Land Resource Area chart, your county is located in what land resource
area or areas.
3. Describe the soil(s) mostly found in your county, based on the chart.
4. The soil in your county belongs in which soil order(s)?
5. Describe the parent material(s) on which the soil in your county was built.
6. The soils in your area were built under what kind of vegetation?
7. The soil in your area belongs to what soil order(s)? Based on the information about soil orders, is the soil in
your area suitable for farming?
Oklahoma Ag in the Classroom is a program of the Oklahoma Cooperative Extension Service, the Oklahoma
Department of Agriculture, Food and Forestry and the Oklahoma State Department of Education.