How Soil Forms

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Terms in this set (...)

soil
It is a complex mixture of mineral particles, air water, humus and various types of living organisms on Earth's surface in which plants can grow.
soil horizon
A layer of soil that differs in color, texture, and composition from the layers above or below it.
humus
a dark colored substance that forms as plant and animal remains decay.
decomposer
the organisms that break the remains of dead organisms into smaller pieces and digest them with chemicals.
loam
soil that is made up of equal parts of clay, sand, and silt.
subsoil
layer of soil below topsoil that has less plant and animal matter than topsoil and contains mostly clay and other materials
topsoil
the crumbly, topmost layer of soil made up of clay and other minerals and humus (nutrients and decaying plant and animal matter)
bedrock
rock that makes up Earth's crust; also the solid rock layer beneath the soil
fertility
measure of how well soil supports plant growth
pH scale
measures acidity of soil

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