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Soil is formed
from rocks and decaying plants and animals.
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An average soil
sample is 45 percent minerals, 25 percent water,
25 percent air, and five percent organic matter.
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Different-sized
mineral particles, such as sand, silt, and clay,
give soil its texture.
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Fungi and
bacteria help break down organic matter in the
soil.
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Plant roots and
lichens break up rocks which become
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part of new soil.
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Roots loosen the
soil, allowing oxygen to penetrate. This
benefits animals living in the soil.
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Roots hold soil
together and help prevent erosion.
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Five to 10 tons
of animal life can live in an acre of soil.
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Earthworms digest
organic matter, recycle nutrients, and make the
surface soil richer.
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Mice take seeds
and other plant materials into underground
burrows, where this material eventually decays
and becomes part of the soil.
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Mice, moles, and
shrews dig burrows which help aerate the soil.
