Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
The Soil System
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Soil formation is a slow process:
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Mature soils are arranged in a
series of zones called SOIL
HORIZONS:
“O” HORIZON = freshly fallen and partially
decomposed leaves, twigs, animal
waste. You can find fungi and other
organic materials.
“A” HORIZON = porous mixture of partially
decomposed organic matter (humus) as
well as bacteria, fungi, earthworms, and
other decomposer organisms interacting
in complex ways. inorganic
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
“B” (subsoil) and “C” (parent material)
HORIZON contain most of the soil’s
inorganic matter, mostly broken-down
rock consisting of varying mixtures of
sand, silt, clay, and gravel..
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Soil Content
Clay (very fine particles) <0.002mm
Silt (fine particles) 0.002-0.05mm
Sand (medium-size particles) 0.05-2.0mm
Gravel (coarse to very coarse particles) >2.0mm
Soil Texture is determined by the relative amounts of the different
types and sizes of mineral particles.
Loam is soil composed of sand, silt, and clay in relatively even
concentration (about 40-40-20% concentration respectively). Loam
soils generally contain more nutrients and humus than sandy soils,
have better infiltration and drainage than silty soils, and are easier to
till than clay soils. Loams are gritty, moist, and retain water easily.
Topic 3
The Soil
System and
Food
Production
Students will be able to:
-to outline how soil systems integrate
aspects of living systems.
-compare the structure and properties of
sand, clay and loam soils including their
relevance to primary productivity.
Soil Texture Triangle
100%clay
0
80
20
60
Increasing
percentage clay
http://www.youtube.
com/watch?v=knrmC
bctGEA
clay
40
silty
clay
sandy
clay
40
60
sandy clay
loam
20
clay
loam
silty clay
loam
loam
silty
loam
sandy
loam
0
Increasing
percentage silt
loamy
sand sand
100%sand
80
80
silt
60
40
Increasing percentage sand
20
100%silt
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Soil texture helps determine SOIL POROSITY, a
measure of the volume of pores or spaces per
volume of soil and the average space between
those spaces.
INFILTRATION is the downward movement of
water through soils.
As the water seeps down, it dissolves various soil
components in upper layers and carries them
down to lower layers in a process called
LEACHING.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
SOIL PERMEABILITY is the rate at which water and
air move from upper to lower soil layers.
Water
High permeability
Water
Low
permeability
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Properties of Soils with Different Textures
Texture
Nutrient
Capacity
Infiltration
WaterHolding
Capacity
Aeration
Workability
Clay
Good
Poor
Good
Poor
Poor
Silt
Medium
Medium
Medium
Medium
Medium
Sand
Poor
Good
Poor
Good
Good
Loam
Good
Good
Good
Good
Good
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Soil erosion is the movement of soil components,
especially surface litter and topsoil.
• The two main agents of erosion are:
1. wind
2. flowing water
• Loss of plant cover by farming, logging, construction,
overgrazing by livestock, off-road vehicles, deliberate
burning of vegetation and other activities leave soil
vulnerable to erosion.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Two major harmful effects of soil erosion:
1. Loss of soil fertility and its ability to hold water
2. Runoff of sediment that pollutes water, kills fish
and shellfish, and clog irrigation ditches, boat
channels, reservoirs, and lakes.
serious concern
some concern
Stable areas
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Desertification is the enlargement of
deserts through human activities.
Causes
Consequences
Overgrazing
Worsening drought
Deforestation
Famine
Surface mining
Economic losses
Erosion
Lower living
standards
Salinization
Soil compaction
Environmental
refugees
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
SALINATION
WATERLOGGING
1. Irrigation water
contains small
amounts of dissolved
salts.
• Precipitation and
irrigation water
percolate
downward.
2. Evaporation and
transpiration leave
salts behind.
• Water table
rises.
3. Salt builds up in soil.
• Causes roots to
drown.
Both result in stunted plant growth, lower crop yields, dead plants
and ruined land.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Soil Conservation involves reducing
soil erosion and restoring soil fertility.
http://www.youtube.com/watch?v=MQQcnId3Z7A
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Contour planting and strip cropping: each row acts as a
small dam to help hold soil and slow water runoff.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Alley cropping or agroforestry: several crops are planted together
in strips or alleys between trees and shrubs that can provide fruit
or fuel-wood, shade, help retain and slowly release soil moisture,
and fodder for livestock.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Windbreaks or shelterbelts of trees reduce wind erosion, help
retain soil, supply wood for fuel, and provide habitats for birds,
pest-eating and pollinating insects, and other animals.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Terracing retains water
for crops at each level
and reduces soil
erosion
by controlling runoff.
Topic 3
The Soil System
and Food
Production
Students will be able to:
-to outline how soil systems integrate aspects of living systems .
-compare the structure and properties of sand, clay and loam soils including their relevance
to primary productivity.
Soil Restoration
•
•
•
•
•
•
•
Organic fertilizer
Manure
Compost crop rotation
No till farming
Contour farming
Terracing
Nitrogen fixation-legumes