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Soil is the foundation for living things in our gardens.
The right mix of soil components yields healthy gardens. While we are
constantly observing the plants and animals of soil, third grade takes a closer
look the characteristics of different soils around our schools. We
are very fortunate that most of the soil at the Primary and
Elementary schools is in pretty good shape.
There have been schools on
this property for more than 50 years, so the topsoil had not been removed.
In addition, though the soil on the surrounding hills is clay, ours is not.
It's old river bottom, which means it's rocky
and covered with about a foot of topsoil. This
creates its own problems, but is preferable to clay.
Whatever type of soil one has, though, the best way to improve it is through
adding compost. |
| Soil type is defined by the amount of sand, silt, or clay present in a
given sample, as well as the texture or how it feels.
Soil is created by
weathering of rock over a long period of time
and the decomposition of dead plants and animals. Soil
has five main components.
Humus is completely
decomposed organic matter. It is dark and crumbly, retains moisture,
provides good drainage, and has pore spaces that help soil hold water and air.
Humus keeps soil loose, and is a major source of nutrients for plants and soil
animals.
Gravel is small rocks that
are the largest particle of soil. Particle size is anything larger than
2.0mm. Gravel creates pore spaces, but too much gravel
results in poor water retention.
Sand is
small rock material you see at most beaches.
The particles are easily seen and generally 0.02-2.0mm in size.
Sandy soil has less than 20% silt
and/or clay. Water drains through sandy
soil very quickly.
Silt is rock particles that measure from 0.004-0.006mm.
Individual particles cannot be seen with the
unaided eye. To the touch, silt feels like flour.
Clay is the smallest rock
particle, less than 0.002mm in size stuff
that pottery is made of. Clay soil is
made of at least 30% clay particles. Clay soil is
dense. When it's wet, clay soil feels sticky and causes water to puddle.
When it's dry, clay soil feels hard like a clay pot.
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Materials: You will need the following materials for each
group:
1. One cup of sand
2. One cup of clay
3. One cup of potting soil
4. Six paper or styrofoam cups
5. Three paper towels
6. One measuring cup
7. One nail
8. Six popsicle sticks
Procedure:
1. Make a filter by using the nail to punch six to eight holes in each
of three of the cups. These are the "filter cups."
2. Cut a piece of paper towel that will just cover the bottom of the
cup and put it inside the "filter cups"
3. Fill, to within one inch of the top, each of the filter cups with a
different type of soil--pack the soil
4. Place two popsicle sticks across each of the remaining cups
5. Sit a filter cup of soil on the popsicle sticks
6. Slowly add one cup of water to each of the soils
7. When the water stops dripping from the filter cups--measure the
amount of water in the bottom cups |
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How can we slow down soil erosion? |
Materials: The following materials are needed for each group of
students
1. One one-half gallon milk carton
2. Two plastic containers for basins
3. Four quarts of water
4. Several books
5. Soil--soil from the flowerbed will do fine
6. Leaves, sticks, and small rocks
Procedure:
1. Prepare erosion trays by cutting the top off the
milk carton.
2. Cut the bottom portion of the carton in half
lengthwise--these are your erosion trays
3. Put equal amounts of soil in each erosion tray
4. Spread leaves, sticks, and rocks over the top of
the soil in one tray--leave the other tray with just soil
5. Use the books to tilt both trays at the same angle and
place the basins below the trays to catch runoff
6. Predict which tray will lose the most soil, then
slowly sprinkle one quart of water over each tray
7. Observe how the soil erodes in each tray |
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How
much of the land on earth can be used to produce food? |
Materials:
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One apple per each group of two children
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Two paper plates per group--one marked available for use the other marked
unavailable for use
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One plastic knife per group.
Procedure:
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Slice an apple into quarters. Place three of the quarters into
the plate marked unavailable for use. These represent the oceans of the
world. The fourth quarter roughly represents the total land area left. Place this on the available for use plate.
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Slice this land quarter in half, giving you two 1/8 world pieces. Set
aside one of these pieces on the unavailable for use plate. This is land
inhospitable to people--the polar areas, deserts, swamps, very high or
rocky mountainous areas. The other 1/8 piece is the land area where people
live, but not necessarily grow the foods needed for life.
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Now slice this 1/8 piece into four sections, giving you four 1/32 pieces
of the original apple. Set three of these pieces on the unavailable
for use plate. These are areas too rocky, too wet, too cold, too steep,
or with soil too poor to actually produce food; they also include the areas
of land that could produce food but are buried under cities, highways,
suburban developments, shopping centers, and other structures that people
have built.
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This leaves us with a 1/32 slice of the earth left on the available for
use plate. Carefully peel this slice and leave only the peeling on the
available for use plate. This tiny bit of peeling represents the surface,
the very thin skin of the earth's crust upon which mankind depends.
It
is less than five feet deep, and in comparison to the not available for
use plate, it represents a very small fraction of earth that is available
to produce food crops.
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Related lesson
plans |
Grade |
When in Our Garden
Cycle |
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Granny's
Harvest for Vegetable Soup -
The fall
harvest is the basis to understand
what plants need to grow and to examine soil
texture and observable soil properties that support plant
and animal growth. A sense of
community is fostered when the school-wide bounty is served to
students as vegetable soup in the cafeteria. |
3 |
September |
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Soil
Formation
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Soil samples are used
to demonstrate the components of soil and to discuss the
importance of soil in the growth of plants and animals. |
3 |
October |
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| "Don't judge each
day by the harvest you reap, but by the seeds you plant." Robert Louis
Stevenson |
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