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The Dirty Truth |
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You have already done several classic tests on soil. Here are a few more:
Settling
Another way to examine soils is by testing how they
settle after being shaken with water. You'll need your three soil
samples, small plastic cups, and water. Put some of the clay in
a cup. Add water and stir vigorously or, if you're outside, put
your hand over the top and shake it. Now watch and see what happens
to the soil. Carefully watch what happens. Repeat with the other
samples. Compare the settling rates for each soil. Did you find
that heavy particles like small rocks and gravel will settle to
the bottom first. Small particles like some clays may not settle
for several days. Let your cups sit undisturbed for several days.
How did they change?
Water and Soil
Different kinds of soil can absorb different amounts
of water. You'll need your three soil samples, water, three paper
towels, and three cups. Fold each paper towel in half and then
in half again.You want to have a shape that is almost a square.
Make a cup out of your paper towel by pinching three layers in
one hand and pulling the fourth layer out. Put some clay in one
"cup," humus in another, and sand in the third. Try
to use equal amounts of each soil. Set each paper towel cup in
a real cup. Slowly drip water in the clay cup and observe what
happens. Does it go right through or is it absorbed by the soil?
Does water come out the bottom of the paper towel cup? Repeat
with the other soils. How are they the same and how are they different?
Use everything you've learned about soils to figure out how planting
a garden in Minnesota (humus soil) is different from planting
one in Oregon (clay soil) or New Mexico (sandy soil).
Organic and
Nonorganic Components
The clay and sand you tested are both nonorganic. That
means that they are made of things that were never alive. The
humus has organic materials in it, things like branches and leaves.
Take some of the soil where you live and put it into a jar. Fill the jar about half full of soil. Now add water until the jar is about 3/4 full. Put the lid on really tight and SHAKE. Let the jar stand, undisturbed, until you start seeing different levels. Pour off one layer at a time and examine it with your hand lens. What did you find?
copyright 2003, Center for Hands-On Learning