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Natural Resources
S
ome people call it “dirt.” Others call it “earth” or “the ground.”
What they are talking about is soil. Soil is the layer on top of
the land. Soil is what you dig up with a shovel. You can stir soil
with water to make mud or turn it over with a plow.
The soil in your schoolyard is different from the soil in a field. The
soil in a field is different from the soil in a desert. In fact, soils are
different just about every place you look. But in some ways, soils all
over the world are the same.
All soils have two basic ingredients: rock and
humus
. The rock
part of the soil comes in a variety of sizes, including gravel, sand, silt,
and clay. Particles of gravel are rocks the size of rice and peas. Sand
particles are smaller rocks. Silt particles are so small it’s impossible to
see just one. Clay particles are smallest of all.
Humus is black
decomposing organic matter
. It comes from
the dead and discarded parts of plants and animals.
Soil in a field prepared
for planting
Soil in the Mojave Desert
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