Transcript Chapter 1 - Charleville Gardens

Soil
Soil in Our Environment
What is soil? Or is it Dirt?
“Gold’s father is dirt, yet it regards itself as noble.” Yiddish Proverb
Is it alive?
Is it fragile?
Formations of Soils
How much time does it take to form
about 1” of topsoil?
About 1,000 years!
Destruction of Soils
How long does it take to deplete about
1” of topsoil?
In a few short years – less than 5 years
in some areas
Destruction of Soils
What forces of nature do you suppose
cause the largest amounts of erosion?
A hint . . .
Uh Huh . . .
Wind!
What Else?
Another hint?
That’s Right . . .
Water!
Destruction of Soils
So what do you suppose causes soil, on
a large scale, to be so susceptible to
wind and/or water erosion?
Destruction of Soils
Mismanagement . . .
poor agricultural practices
Carelessness
Neglect
Leads to . . . (and the magic word is?)
Erosion – wind and water
Soil loss through plowing
The Outcome?
How about the failure of the local
civilization?
What about from a
landscape perspective?
Do we still see erosion?
What about soil fertility?
And plant health and vigor?
Chapter 1
Soil Composition and Importance
Pages 1 – 24
What is soil?
The uppermost layer of the Earth’s
surface – the tectonic plates . . .
The tectonic plates?
Tectonic Plates
?
What is soil . . .
. . . A product of?
Geologic processes
weathered rock – parent materials
Weathering?
Physical and chemical process
Physical process . . .
freeze-thaw
tumbling down hills and streams
Weathering?
Chemical process . . .
chemical reactions between rocks and
water
Decomposition of parent
materials/rocks
End product are soils
What is soil composed of?
Minerals . . .
altered physically and chemically
from original bedrock
Organic chemicals
Biomass
Gasses – air, water
Dissolved materials
Soil Composition . . .
Made up of three fractions . . .
mineral fraction
organic fraction
gasses and water
Mineral fraction
Sand – 2mm to 0.05mm
Silt – 0.05mm to 0.002mm
Clay - <0.002mm
Analogy – compare a basketball to a
baseball to a BB
Organic fraction . . .
Living organisms including:
plants and plant roots
bacteria & fungi
worms, insects, etc.
dead/decomposing organisms
Organic fraction . . .
Organic materials provide a reservoir
of plant nutrients
Nutrients are continually recycled as
organic materials
Gasses and water . . .
Oxygen (O)
Carbon dioxide (CO2)
Nitrogen (N), etc.
H2 O
Gasses and water . . .
Fills in pore spaces between the soil
particles
Larger pore spaces contain more gasses
Smaller pore spaces contain more water
Soil pore spaces can take up to 50% of
the volume of a given soil sample
Soil texture
What did we say made up the mineral
fraction?
Sand . . .
Silt and . . .
Clay
So soil texture is . . .
The percentage (%) of . . .
Sand . . .
Silt and . . .
Clay . . .
By volume
We’ll come back to that later. . . .
Name 2 reasons soils are
studied?
Agricultural reasons . . .
ability to support plant life
soil fertility
Structural reasons . . .
building construction
ability to support foundations, footings,
etc.
Some definitions
Actually, a whole bunch of
definitions . . .
Rocks . . .
What are rocks?
consolidated mass of minerals
Minerals . . .
And minerals?
unique, repeatable combination of
elements
stable
consistent hardness, melting point,
etc.
Elements . . .
What about elements?
found on the periodic table . . .
unique combination of protons and
neutrons in a nucleus . . .
surrounded by electrons
The nucleus . . .
Nucleus of an atom contains . . .
protons (+)
neutrons (-)
and electrons
Three types of rocks . .
Rocks are found in three forms . . .
igneous - divided into two groups
metamorphic
sedimentary
Igneous rocks
Extrusive igneous rock - lava
volcanic in nature
formed by being pushed out of the
Earth’s crust
small to no crystals caused by rapid
solidification when exposed to air or
water
ex. basalt
Igneous rocks
Intrusive igneous rock
forms as magma cools within the
crust
can form large, distinct crystals
caused by slow cooling under ground
ex. granite (Sierra Nevada mountains,
Southern California batholiths)
Sedimentary rock
Made from sediments
eroded igneous, metamorphic or
sedimentary materials
deposited horizontally by wind or
water
solidifies over time and as sediments
continue to build over time
Sedimentary rock
typically softer than igneous or
metamorphic rock
ex. sandstone (western Rocky
Mountains, Utah, Grand Canyon)
Metamorphic rock
The name implies change . . .
igneous, sedimentary or other
metamorphic rock
changed by being subjected to heat
and or pressure
hard, strong and resistant to
weathering
Tropical region soils . . .
Often subjected to much leaching
Basalts – minerals leached out settle
out as clays
Tropical region soils . . .
Clay soils in tropical areas start out
fairly fertile
leaching from rainfall . . .
high temperatures . . .
extensive plant growth . . .
they loose fertility
Tropical region soils . . .
Tropical clay soils tend to be shallow
erode quickly when disturbed . . .
by clearing of vegetation and
agriculture
Temperate region soils
Often granitic, sandy soils
fertility varies
soil depth vary
Parent materials
It’s all about the rock!
Rocks weather
How?
Physical and chemical weathering
Decomposition of rocks creates soils
Geography & local weather
Affect:
soil formation
development of plant species and
varieties
Organic soils
Formed exclusively from organic
matter
formed as peat bogs dry out
peat soils
muck soils
Ex. areas of the Sacramento River
Delta
Soil horizons . . .
Separate and distinct layers of soil
down to parent materials
and basement rock
Examples:
O-Horizon
A-Horizon
B-Horizon
C-Horizon
Soil horizons . . .
Soil horizon layers and content . . .
very much based on their surroundings
ex.
topography
deposition history
local weather, etc.
Hatch Act of 1887
Set aside land around the country for
agricultural studies
Created series of agricultural
experimental stations
Provides funds for Land Grant schools
founded under the Morrill Act 1862
USNRCS
US Natural Resource Conservation
Service
formerly: US Soil Conservation
Service
under the United States Department
of Agriculture (USDA)
part of the Executive Branch of the
US Government
USNRCS
Provides an interactive website with
regional soil maps
http://www.nrcs.usda.gov/
Topography . . .
Study and graphic representation of
changes of relief features . . .
in surface configurations of a given
area
Indicates changes in elevations and
positions on a map
Alluvial fans . . .
Distinct fan-shaped
formation of soil
deposition . . .
Found at base of
hills or downstream ends of
rivers