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Granny's
Garden School
Connecting children
with nature
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| We were very fortunate that most of the soil at the Primary and
Elementary schools was 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 its not.
It's old river bottom which means it's rocky covered with about a foot of
topsoil. This creates it's 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. It is produced by
weathering of rock over a period of time. Five main types of soil may be
identified and are defined by composition.
Humus is the dark, moist layer found on the top of a soil profile.
This is because it is made up of dead and decaying matter. It is fairly fertile
in that the decay process adds nutrients to the soil that plants love to soak
up.
Gravel is made of, well, gravel. Particle size is anything larger than
2.0mm. In other words, it contains highly visible rock particles or pebbles
Sand is the stuff you see at most beaches. In terms of texture, it is
made of large particles, 0.02-2.0mm in size. Sandy soil has less than 20% silt
and/or clay. Water drains through sand very quickly.
Silt has particles that measure from 0.004-0.006mm. The grains in silt
look like tiny pieces of rock. Silt will generally float on the top of a layer
of water and will take time to settle out of the mixture.
Clay is the stuff that pottery is made of. In terms of texture, it is
made of particles smaller than sand, less than 0.002mm in size. Clayey soil is
made of at least 30% clay particles. Since it is composed of the smallest
particles, it will take the longest to settle out of solution. Also, because of
the small particulate size, water tends to puddle on clayey soils.
A soil profile of any given position may contain one or all or any
combination of the above. (Check out "Soil
Recipes" for an activity that shows this diversity in your area.)
Since there is no single soil type in all fields, even within one field,
agronomists must know their growing area in terms of soil type, water retention,
and nutrients available. |
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How much water do different soils hold?
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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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Do all soils settle out of water at
the same rate?
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Materials: The following will be needed for each group of students:
1. One two liter bottle for each type of "dirt"
tested
2. Enough water to fill each two liter bottle at
least 3/4 full
3. Samples of various "dirts"--You can have
students bring soil samples or you can go out onto the school ground
and collect some different
kinds.--Be sure to get some sand, some clay if possible, some dirt from a flower
bed,
and perhaps some potting
soil.
4. Plastic spoons
Procedure:
1. Have the students fill their bottles about
three-fourths full of water
2. Using the plastic spoon put at least 1/2 cup of
soil into the water (you will need to do this slowly and carefully
because the opening to the two
liter bottle is small
3. Place the lid on bottle and shake the soil and water
mixture. Allow the mixture to stand for several minutes
4. Make the following observations:
a. Does the soil settle to the
bottom in layers?
b. What kind of material settled
first? Last?
c. Is there material floating on
top of the water?
d. What is the color of the
water?
e. Allow water to stand for
several days. Does all the material eventually settle out of the water? |
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How can we slow down soil erosion?
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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--just 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. Set 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 1/8th 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 1/8th piece is the land area where people
live, but not necessarily grow the foods needed for life.
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Now slice this 1/8th piece into four sections, giving you four 1/32nd 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 1/32nd 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
too produce food crops.
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Free
coffee for garden volunteers.