Soil:
A marriage of science and math?
Panhandle Math-Science Teachers' Conference
September 20, 2008, West
Texas A&M University, Canyon, TX
http://www.wtamu.edu/~crobinson/DrDirt/WT_MSTC08a.html
Dr. Dirt's K-12 Teaching Activities
Links
will open in new windows.
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The Apple as
Planet Earth: A quick, simple illustration using an apple to
help students understand the importance and limited nature of the soil
resource. The earth is shared with about 6.8 billion people, who depend
on to produce all the food, fiber and lumber to feed, clothe, and
shelter them all, so that the populace does not end up hungry, naked
and homeless.
You need an apple and a knife (sharp enough to easily cut the apple).
The basic facts you need to complete the demonstration include:
Approximately 70% of the earth's surface is
covered with water (simplify it for cutting an apple to about 75%,
three-fourths)
Half of the part that is not water is in polar
ice caps and high mountain ranges (1/2 of 1/4 - note use of math
skills, 1/8 remains)
Of the remaining 1/8, 3/4 of it is too hot,
too cold, too steep, too shallow, too wet, too dry, or has some other
problem so that it
cannot be used to
produce the food, fiber and lumber to help feed, clothe, and shelter
the 6.8 billion people on the planet. This
leaves 1/4 of 1/8, or
1/32 of the earth's surface that is used in food, fiber and lumber
production.
Actually, though, the soil is only the thin
skin (peel a fraction of the remaining slice, so that the peel hangs
down), the surface
1 to 2 meters, which
is the part used to produce the food, fiber, and lumber.
Each year, the population grows, and the soil
available for food, fiber, and lumber production decreases due to
desertification,
salinization,
sodification, urban sprawl and industrial development, etc. So, farmers
around the world have to produce more and
more food on less and
less land every year.
Use math to determine the appropriate fractions. then determine the
approximate area for each fraction of the earth's surface: water, polar
ice caps and high mountain ranges, poor land, productive land. The
approximate surface area of the earth is 510,065,600 km2 or
196,940,400 square miles.
The 1-minute video is found on the American Farmland Trust
website (at the bottom). In case the link does not work, the url
is: http://www.farmland.org/#.
TEKS:
Grade 1: 112.3.b1B
Grade 2: 112.4.b1B, 10B
Grade 3: 112.5.b1B, 3C, 11A
Grade 4: 112.6.b1B, 3C
Grade 5: 112.7.b1B, 3C
Grade 6: 112.22.b1B, 3C
Grade 7: 112.23.b1B, 2A
Grade 8: 112.24.b1B
Env Sys: 112.44c5A
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Scale
model of
a soil profile: A simple illustration that gives students an
opportunity to take home their own microscale model of a real soil
profile. It is possible to make this one as complex or simple as you
desire. Consider using: Existing road cuts or stream banks on short
field trips, 24 to 36" deep hole dug with a shovel in the school yard
or lawn, a hole about 2 meters deep x 1 meter wide x 2 or 3 meters long
dug by a backhoe, etc.
This activity uses math in developing the scale to represent the depth
of the profile. (Paint sticks and glue work even better, if there is a
place to let the glued soils dry.)
The direct url is http://soils.usda.gov/education/resources/k_12/lessons/profile/.
Several other educational activities are included at
the parent site: http://soils.usda.gov/education/resources/k_12/.
The one above is included in the lessons link.
TEKS:
Grade 3: 112.5.b3C, 11B
Grade 4: 112.6.b3C
Grade 5: 112.7.b3C
Grade 6: 112.22.b3C, 4 A&B |
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Scale
model of soil particles: A medium-sized grain of sand (0.70
mm), just visible to the eye, is held in the calipers. (Click on the
image for a larger picture, in which that is more easily seen. Click here for a close-up of the
sand grain, which is just below the word sand between the black lines
on the caliber jaws.)
If this barely visible object represents a clay particle (0.001 mm),
then silt particles would be 1.4 to 35 mm in diameter, and sands would
be 35 to 1400 mm in diameter.
So, the bb (4.4 mm), the large bead (9.0 mm), the small marble (14.3
mm), and the large marble (23.4 mm) would all be silt particles.
The golf ball (42.6 mm), the beach ball (~400 mm), and a ball with the
diameter of the meter stick would be sands.
The standard screen in the background (about 1.8 m x 1.8 m) would be
the size of a small piece of gravel.
Given the previous example, if a bb represents a clay particle
(0.001 mm), how big would a sphere representing a silt (0.05 to 0.002
mm) or sand (2.0 to 0.05 mm) particle need to be?
(The largest sand particle would be a sphere 8.8 meters in diameter.)
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The
Sponge Model: A sponge is used to represent several facets of
soil water relations
and engineering properties.
Water holding capacity of the soil.
Weigh a dry sponge. Soak the sponge. Hold the sponge above the water
until all water drains. Weigh the wet sponge to determine the quantity
of water the sponge holds against the pull of gravity. This represents
the "field capacity" of soil. Squeeze all water possible out of the
sponge. Weigh the sponge. The water removed from the sponge represents
the "plant available water" in the soil. Let the sponge air dry and
weigh it. Are the beginning and ending "dry" weights the same? Put the
sponge in a drying oven (105 degrees centigrade or 230 degrees
Fahrenheit for 24 hours). This represents the "dry weight" of soil
(rather than the air dry weight). All soil water calculations are made
relative to this dry weight. What is the percent of each water
condition relative to the sponge dry weight.
Use a different sponge. Does it have the same characteristics?
The same process can be done with soils.
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Soil is a filter: http://www.wtamu.edu/%7Ecrobinson/DrDirt/filter.html
Role of soil in the water cycle: Infiltration,
filtration, and storage. Water moves into soil during precipitation
events. The rate of water movement is determined by the soil texture
and
structure (shape of the aggregates, or clumps of soil particles joined
together). Coarse soils and well-aggregated soils tend to have
higher infiltration rates and better drainage of water through the soil
and movement of air
into the soil (aeration). The soil filters
pollutants physically, chemically, and biologically as water moves
through the soil. If the system is not oveloaded, it functions well.
Pollutants reach ground or surface waters when the soil is overloaded
with a contaminant.
Water stored in soil can be used by plants,
which transpire water back into the atmosphere. Some water stored by
soil can be lost from bare soil surfaces by evaporation.
Math can be added by drying the soil prior to the experiment and adding
the same weight of soil into each container, adding a measured quantity
of water, recording the quantity of water collected in 15-second
intervals (longer for some soils) to obtain a rate, recording the total
quantity of water collected, and weighing the container to see if the
quantity of water remaining in the soil matches the difference between
the quantity added and collected.
TEKS:
Grade 1: 112.3.b7A, 10 A-C
Grade 2: 112.4.b7A, 10 A&B
Grade 3: 112.5.b2 A-E, 3 A&C, 4 A&B, 7B, 11B
Grade 4: 112.6.b2 A-E, 3 A&C, 4 A&B, 11A
Grade 5: 112.7.b2 A-E, 3 A&C, 4 A&B, 6B
Grade 6: 112.22.b2 A-E, 3 A&C, 4 A&B, 14B
Grade 7: 112.23.b2 A-E, 3 A&C, 4 A&B (rate of
water flow), 8A
Grade 8: 112.24.b2 A-E, 3 A&C, 4 A&B, 8B, 12C, 14C
Int Phys Chem: 112.42c2 A-D, 3 A&C, 4B, 9A
Env Sys: 112.44c2 A-D, 5 B&F
Chem 112.45c2 A-E
Phys: 112.47c2 A-F
(For concepts about water storage, see The
Sponge Model: http://www.wtamu.edu/%7Ecrobinson/sponge/index.html.)
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Soil texture
Texture by feel and soil texture triangle: http://www.wtamu.edu/~crobinson/soils/unit_1/txtr_feel.html
(sample image at right)
Use a bottle or jar to estimate the amount of
sand, silt, and clay. This procedure integrates math with science.
Measure the constituents of the bottle to estimate percentages by
volume occupied.
Soil texture is determined from mass fractions. The activity by Ted
Sammis also includes densities for an estimate of percentages by mass
instead of volume.
Background: https://www.soils.org/lessons/plans/lessons/texture.html
Activity: https://www.soils.org/lessons/plans/activities/texture.html,
Ted Sammis, NMSU
TEKS:
Grade 1: 112.3.b2B
Grade 2: 112.3.b4A, 2B, 4A
Grade 3: 112.5.b4 A&B, 11B
Grade 4: 112.6.b2 A-E (using different soil types), 4
A&B, 11A
Grade 5: 112.7.b2 A-E (using different soil types), 4
A&B, 7B
Grade 6: 112.22.b2 A-E (using different soil types), 4
A&B
Grade 7: 112.23.b2 A-E (using different soil types), 4
A&B, 8A
Grade 8: 112.24.b2 A-E, (using different soil types)3
A&C, 4 A&B
Int Phys Chem: 112.42c2 A-D (using different soil types),
3 A&C, 4B, 7E
Phys: 112.47c2 A-F (using different soil types) |
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Add soil to bottle
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Add water to bottle
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Shake, then measure at 40
seconds
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24 hours later
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Depth
measurements for the bottles shown above.
Total soil: 82
mm
sand: 40
mm
silt: 62
mm
clay: 82 mm
Determine the relative volume occupied by
silt: (silt -
sand) = 62 mm - 40 mm = 22 mm
clay: (clay - silt) =
82 mm - 62 mm = 20 mm
Determine volume percentages of
sand: 40/82 * 100 = 49%
silt: 22/82 * 100 = 27%
clay: 20/82 * 100 = 24%
Using this volume
estimation, the texture would be sandy clay loam.
Using the volume/mass density conversion (Sammis), multiply the
percentage of sand by 1.19, the percentage of silt by 0.87 and the
percentage of clay by 0.94.
Determine the mass:
sand: 49% * 1.19 = 58%
silt: 27% * 0.87 = 23%
clay: 24% * 0.94 = 22%
Sammis recommends letting the bottles sit for several days (allows more
settling of the particles, especially the clays). This example shows
why this is important. The sum of the sand, silt and clay is 103%. It
cannot be more than 100%. Taking measurements after a few days should
eliminate this problem.
The texture from the
mass estimates likely will be on the sandy loam/sandy clay loam
line.
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Sand
Castles: Pre-engineering 101
These simple exercises demonstrate some basic soil engineering
properties using dry and wet sand (and other particles). Angle of
repose of a material is determined by friction, gravity, adhesion and
cohesion. In dry sand, gravity and friction dominate. Friction is
affected by particle size and shape.
Use a funnel to pour a known weight of sand onto a blank sheet of
paper. Draw a line around the circumference of the resulting cone.
Measure the height and angle the material makes with the surface.
Determine the height to diameter (width) ratio. Estimate the volume of
the pyramidal cone. Do all materials have similar angles, ratios,
volumes?
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Soil Temperature
These exercises demonstrate the
effects of
water, color, mulch, and configuration on soil temperature.
Record initial temperature. Initiate the heat lamps, and record
temperature at 5-minute intervals for 30-minutes (or longer - I use 1
hour), then remove the lamps and record temperature for another 30
minutes. Graph temperature (y-axis) versus time (x-axis). Evaluate the
shape of the graph (linear or nonlinear) in both heating and cooling
phases. Do all conditions behave the same?
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Other resources and
opportunities:
Click on the links above to find the methods for each of the activities
above. Visit Dr. Dirt's homepage to find other simple, educational
activities suited for you classroom. http://www.wtamu.edu/~crobinson/DrDirt.htm
Dig It! The
Secrets of Soil Soils Exhibit in the Smithsonian Museum of
Natural History
http://forces.si.edu/soils/
Information for teachers: https://www.soils.org/smithsonian/teachers.html
Website for kids: https://www.soils.org/digdeeper/
Soil! Get
the Inside
Scoop Hey, I Want my Own Soils Book! That's
what we said too! We made and wrote a book targeted for kids in  grades
4-6, with cool enough pictures that anyone of any age will love it! The
book talks about how "Soil is NOT Dirt" and "Yikes, It's Alive!" It
comes with your very own soils glossary and lots of pictures to explain
soil and show pretty, colorful soils from all over the world! It's now
available for purchase SSSA's
online bookstore (note, you'll need to create an account or login
to purchase).
Window on a Wider World: http://www.windowonawiderworld.org/
Look for a STEM (Science, Technology,
Engineering and Mathematics) Collaborative in February, focused on
Earth and Energy
Erosion and other topics will help
provide teachers activities to help students master middle school
science TEKS
Panhandle Math-Science Teachers' Conference, September 20, 2008, West
Texas A&M University, Canyon, TX
In June, conference
information will be accessible from the conference’s website
at www.wtamu.edu/pmsc.
If you have any questions,
please contact us at 806-651-2906 or acampbell@wtamu.edu
.
Dr. Ashley
Campbell
Mr. Gilbert Antunez
Conference
Co-Chair
Conference Co-Chair
National Science Teachers' Association: http://www.nsta.org/
Clay Robinson, Ph.D., alias Dr. Dirt
Professor of Soil Science
West Texas A&M University
http://www.wtamu.edu/~crobinson/DrDirt.htm
crobinson@wtamu.edu
office phone: 806.651.2553
fax: 806.651.2938
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