Transcript What is Soilx

What is the
composition
of soil?
Essential Question:
How is soil formed?
Standard:
S6E5h. Describe soil as consisting
of weathered rocks and
decomposed organic material.
Composition of Soil
• Air
• Water
• Soil Particles
–Weathered rock and mineral
particles such as clay, sand,
and silt
–Decomposed organic matter
Composition of Soil
Soil has many small spaces
between individual soil particles
that are filled with water or air.
Label your diagram
The rock and mineral
fragments come from rocks
that have been weathered.
Most of these fragments are
small particles of sediment
such as clay, silt, and sand.
Organic matter is the remains
of once living organisms.
Organic matter can come from
plant leaves, stems, roots,
animals, and microorganisms.
Organic Matter in Soil
After organic matter gets into
soil, fungi and bacteria cause
it to decay (decompose).
The decayed organic matter
turns into humus, a source of
nutrients for plants.
http://techalive.mtu.edu/meec/
module10/Decomposition.htm
As worms, insects, and animals
burrow through soil, they mix the
humus with the fragments of rock.
Turn to an elbow partner and
discuss why living organisms
are important for good soil.
Good quality soil has equal
amounts of humus and weathered
rock. Living organisms help to mix
humus around in soil.
Soil Layers
(Horizons)
Organic Matter
Soil Layers
(Horizons)
Top Soil
(Horizon A)
The topsoil has
more humus and
fewer rock and
mineral particles
than the other layers.
The subsoil has less
organic matter and is
lighter in color because
it has less humus.
Therefore, it is less
fertile.
Subsoil
(Horizon B)
Horizon C
consists of
partially weathered
rock that gave
rise to the soil
horizons above it
(parent rock).
Parent Rock
(Horizon C)
Soil Layers
(Horizons)
Most Fertile
Least Fertile
Soil can take thousands
of years to form and is
different depending on
where it is formed.