Transcript Unappreciated natural resource

Soil
the unappreciated
natural resource
Fred Magdoff
[email protected]
Many a hillside do the torrents furrow
deeply, and down to the dark sea they
rush headlong from the mountains, with a
mighty roar, and the tilled fields of men
are wasted.
— The Iliad
You ask me to plow the ground.
Shall I take a knife and tear my
mother’s breast?
— Native American Chief
... for soil thou art and unto
soil shalt thou return.
— Book of Genesis
Then God Yahweh formed
man out of the soil of the
earth
— Book of Genesis
Soil + Life
Adam — from Hebrew word for soil
Eve — from the word for life
Are you really “made”
out of soil?
Where did the following come from:
• calcium in your bones
• phosphorus in bones and fats and nucleic acids
• nitrogen in proteins
• iron, potassium, magnesium, etc.
Are you really “made”
out of soil?
And where did the carbon come from?
— From plants growing on and in soils
and that fixed atmospheric CO2.
What do plants
need?
What do plants
need?
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Light
Warmth
Carbon dioxide (CO2)
Oxygen (O2)
Water
Nutrients
Anchorage
What do plants
need?
 Nutrients
C, H, O,
N, P, K,
Mg, Ca,
S, Fe,
Cu, Co,
Ni, Mn,
Mo, B,
Zn, Cl
What do soils provide
to plants?
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Oxygen (O2) to roots
Help roots get rid of CO2
Water
Most nutrients
Anchorage
What else do SOILS
provide?
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Partitioning rainfall (runoff vs.
infiltration)
What else do SOILS
provide?
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Partitioning rainfall (runoff vs.
infiltration)
Storage for Carbon
carbon dioxide (CO2)
(0.04% in the atmosphere)
respiration
in stems
and leaves
photosynthesis
root respiration
and soil organic
matter
decomposition
crop harvest
crop and
animal
residues
carbon in
soil
organic matter
erosion
The role of soil organic matter in the carbon cycle.
What else do SOILS
provide?
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Partitioning rainfall (runoff vs.
infiltration)
Storehouse for Carbon
Cleansing pollutants (septic seepage
fields, manures, sludges)
Soils are a “living filter”
As water percolates through a soil
• pathogens may be deactivated
• Phosphorus is removed
• Nitrogen is removed
• Carbon is removed
• Many harmful chemicals removed
What else do SOILS
provide?
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Partitioning rainfall (runoff vs.
infiltration)
Storehouse for Carbon
Cleansing pollutants (seepage fields,
manures, sludges)
Building material
What else do SOILS
provide?
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Partitioning rainfall (runoff vs.
infiltration)
Storehouse for Carbon
Cleansing pollutants (seepage fields,
manures, sludges)
Building material
Something to build on (buildings,
roads)
What are soils made of?
Minerals
Organic matter
Pores
(water & air)
What are soils made of?
Minerals
Organic matter
Pores
(water & air)
What are soils made of?
Minerals
Organic
matter
Pores
(water & air)
Organic Matter
Living
Dead
Very Dead
Living
Plants have evolved in a
dynamic relationship
with other organisms
• Beneficial and harmful
• Above and in the soil
plant roots
bacteria
nematodes
fungi
—Living —
earthworms
mites
springtails
moles
Soil organisms and their roles in decomposing residues.
spore
— “Dead” —
Fresh residues in
early stages of
Food supply for the
decomposition
vast number of
organisms that live
in the soil
— “VERY Dead” —
Well decomposed
material, humus
Humus
• Well decomposed, colloidal
• Has many negative sites
(can hold onto cations such
as Ca++, Mg++, K+)
Add
organic
matter
Increased biological activity
(& diversity)
Reduced
soil-borne diseases,
parasitic nematodes
Aggregation
increased
Decomposition
Pore structure Humus and other Nutrients
improved
released
growth
Harmful
promoting
substances
Improved tilth substances
detoxified
and water storage
HEALTHY PLANTS
Figure 4.5 Corn grown
in nutrient solution
with (right) and without
(left) humic acids. Photo
by R. Bartlett.
In this experiment by R. Bartlett
and Yong Lee, adding humic acids
to a nutrient solution increased
the growth of both tomatoes and
corn and increased the amount
and branching of roots.
What are soils made of?
Minerals
Organic matter
Pores
(water & air)
organic matter
air
minerals
solids
Soil wets-up
during rain
water
pores
organic matter
minerals
Soil dries
down
air
water
solids
pores