Transcript How Do Soils Form? - Hicksville Middle School

How Do Soils Form?
Stop treating your soil like DIRT!
Soil is a much more complex living thing
than most people realize. All the mineral
soil on earth today ultimately came from
rocks created by ancient geologic
forces. As this mineral soil is mixed
with organic matter, bacteria, fungi and
other soil organisms, it develops into a
vibrant and very dynamic ecosystem
with thousands (some say billions!) of
different organisms.
What is soil?
• A mixture of weathered rock and
organic remains that cover the bedrock
of an area
• The nature of the soil depends on the
rocks from which the weathered
material came, and the local climate
Soil Horizons
• The further
weathering of soil
produces distinct
layers called
horizons
• Most soils of NYS
do not exhibit the
complete
development of soil
horizons
Organic material
Topsoil
Subsoil
Partially
Weathered
rock
Horizons in a Soil Profile
• Unweathered bedrock is the source of
particles to make up soil
• Partly weathered bedrock is the first
stage towards soil formation
Topsoil
• Contains weathered rock and organic
material
• Humus is the term for organic material
from decayed plants and animals
• Also called Horizon A
• Best layer for growing plants
• Usually dark in color
Subsoil
• Below the topsoil
• Also called Horizon B
• When water passes through the topsoil,
it leeches minerals and deposits them in
the subsoil.
• Subsoil is rich in in minerals but poor in
organic material so it is not good for
growing
Transported Soils
• Formed from weathered rock in another
location and have been moved by an agent
of erosion
Residual Soil
• Formed from the weathering of the
bedrock that they overlie
• Have the same mineral composition of
the local bedrock
Soil Conservation
• Depletion may occur if the same crops
are planted in soil year after year
• Crop Rotation, contour plowing and strip
cropping can prevent depletion
Contour Plowing
Strip Cropping
Cross wind strip cropping laid out perpendicular
to the prevailing wind direction.