Transcript All About Soil_4.7A

AllAllAbout
About
Soil
Soil
4.7A
Soil can basically be separated
into 5 main parts:
1.
2.
3.
4.
5.
Humus
Clay
Silt
Sand
Gravel
Humus: A dark, moist soil composed of bits of
dead, rotting insects, animals, leaves, roots, sticks,
and food. Humus adds nutrients to the soil which
plants need to grow and live.
Clay: A soil that holds water. When wet, clay feels
slippery and slimy. It is made of particles that are
smaller than 0.004 millimeters.
Silt: Soil that looks like fine grains or tiny pieces of
rock. Particles classified as silt measure from
0.004 millimeters to 0.006 millimeters.
Sand: Soil that is coarse and drains quickly. Sand
particles measure from about 0.006 millimeters to
2.00 millimeters.
Gravel: Visible rock particles, sometimes referred
to as pebbles.
Soil Profiles
• A soil profile is a view of
a cross section of soil.
• Most living material
exists in the top section,
or topsoil.
• Plant roots often extend
into the second layer,
called the subsoil.
• The bottom two layers
consist mostly of rock.
Characteristics of Soil Horizons
•
•
•
•
0 Horizon-located on surface, mostly O.M. (organic materials)
A Horizon-Called Topsoil, good amounts of O.M. and minerals.
B Horizon- Known as Subsoil, Less O.M.
C Horizon- Mostly parent material, does little for plant growth.
Soil Texture
Soil texture is the
relative sizes of the
different soil particles.
Major Soil Texture Classes
• Sand is the largest particle.
• Silt is a medium-sized
particle.
• Clay is the smallest particle
in size.
Characteristics of a
Sandy Soil
Characteristics of a
Silty Soil
Characteristics of a Clay Soil
Soil Structure
• Sand, silt and clay
particles combine with
one anther to form
cluster called
aggregates.
• The way in which
aggregates or clusters
are arranged is
referred to as soil
structure.
Soil Structure Categories
Modified from a presentation by Carrie
Nagle, Mecklenberg Public Schools.