Download All soil forming factors interact!!!

Lecture #6 – Plant Nutrition and Soils
Image – a soil profile
1
Key Concepts:
• Resources
Which are required
How they are used
• Essential elements
What they are
What they do
• Soils and soil forming factors
• The rhizosphere
• Some alternate methods to acquire
nutrients
2
Resource requirements for plant
growth???
Solar energy
CO2
O2
Water
Nutrients
The sun
The atmosphere
?
The soil
3
Where do plants get these
resources???
Solar energy
CO2
O2
Water
Mineral Nutrients
The sun
The atmosphere
?
The soil
4
Where do plants get these
resources???
Solar energy
CO2
O2
Water
Mineral Nutrients
The sun
The atmosphere
The soil
5
Image – root system of a grass
Diagram – plant resource
requirements and sources
6
Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water
• Little water is incorporated into plant tissue
What does water contribute to tissue???
• Most water is in the cell solution, in the
vacuoles, or passing through in the
transpiration stream
7
Critical Thinking
• Does wood have such a high percentage
of water???
8
Critical Thinking
• Does wood have such a high percentage
of water???
• Typically not – wood is dead tissue and
xylem often becomes plugged up by
resins, etc in the interior of the tree
This is what we call “heartwood” and it is often
very beautiful
9
Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water
• Little water is incorporated into plant tissue
What does water contribute to tissue???
• Most water is in the cell solution, in the
vacuoles, or passing through in the
transpiration stream
10
Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water
• Little water is incorporated into plant tissue
Water supplies all the H to carbohydrates;
electrons and protons for photosynthesis
• Most water is in the cell solution, in the
vacuoles, or passing through in the
transpiration stream
11
Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water
• Little water is incorporated into plant tissue
Water contributes H to carbohydrates;
electrons and protons for photosynthesis
• Most water is in the cell solution, in the
vacuoles, or passing through in the
transpiration stream
12
DRY plant tissue composition by
weight:
•
•
•
•
45% carbon
Each a tad under 45%
45% oxygen
6% hydrogen
5% inorganic mineral nutrients
13
DRY plant tissue composition by
weight:
•
•
•
•
45% carbon – from ?? CO2
45% oxygen – from ?? CO2
6% hydrogen – from ?? water
5% inorganic mineral nutrients – from ??
soil
14
DRY plant tissue composition by
weight:
•
•
•
•
45% carbon – from CO2
45% oxygen – from
6% hydrogen – from
5% inorganic mineral nutrients – from
15
DRY plant tissue composition by
weight:
•
•
•
•
45% carbon – from CO2
45% oxygen – from CO2
6% hydrogen – from water
5% inorganic mineral nutrients – from
16
C, H, O – source and fate in
photosynthesis
Diagram – what goes into photosynthesis and what comes out
17
DRY plant tissue composition by
weight:
•
•
•
•
45% carbon – from CO2
45% oxygen – from CO2
6% hydrogen – from water
5% inorganic mineral nutrients – from soil
 0.75-1% of wet weight, but many are essential to
plant growth and function
18
Critical Thinking
• What is the difference between a chemical
element, a molecule and a
macromolecule???
19
Critical Thinking
Diagram – structure of chlorophyll molecule
• What is the difference between a chemical
element, a molecule and a
macromolecule???
• N vs. N2 vs. chlorophyll
20
Essential Elements
• Chemical elements
Not molecules, though some are delivered in
that form – N vs. NO3-
• Required for growth and function of the plant
• Can’t be replaced by some other element
• Some contribute to structural components
• Some contribute to metabolic processes or
the maintenance of homeostasis
21
Essential elements in structural
plant components:
• What are some essential structural
components???
?
22
Essential elements in structural
plant components:
•
•
•
•
•
Cellulose – ??
Lignin – ??
Pectin – ??
Cell membranes – ??
Proteins (cell membrane, cytoskeleton) – ??
23
Essential elements in structural
plant components:
•
•
•
•
•
Cellulose – C, H, O
Lignin – C, H, O, S
Pectin – C, H, O, Ca
Cell membranes – C, H, O, P
Proteins (cell membrane, cytoskeleton) –
C, H, O, N, sometimes S
Note – C H and O are in ALMOST ALL organic molecules
24
Essential elements for metabolic
processes:
• What are some essential molecules used
in metabolic processes???
?
25
Essential elements for metabolic
processes:
•
•
•
•
•
•
Chlorophyll – ??
Nucleic acids – ??
ATP – ??
Enzymes and other proteins – ??
Enzyme cofactors – ??
Elements that control water, charge and
solute balance – ??
26
Essential elements for metabolic
processes:
•
•
•
•
•
•
Chlorophyll – C, H, O, N, Mg
Nucleic acids – C, H, O, N, P
ATP – C, H, O, N, P
Enzymes and other proteins – C, H, O, N..S
Enzyme cofactors – many micronutrients
Elements that control water, charge and
solute balance – K, Cl, P, Ca, others
Note – C H and O are in ALMOST ALL organic molecules27
Macro Nutrients vs. Micro Nutrients
•
•
•
•
•
•
Nitrogen
Potassium
Calcium
Magnesium
Phosphorous
Sulfur
mass
All used in large
quantities to support
the structures and
processes listed before
• Chlorine, Iron, Boron,
Manganese, Zinc,
Copper and
Molybdenum
• Some plants also require
Nickel, Sodium, Silicon,
Selenium or others
Mostly used in enzymes,
as enzyme cofactors or in
electron transfers – often
reused, less required 28
Study table in book!
Table – essential nutrients, both macro and micro
29
Memory device in honor of my friend
and mentor, Dr. Chuck Davey –
celebrated in 2006 for 50 years of
service to soil science!!!
“C HOPKNS CaFe, Mg, Mn B CuZn Mo, Cl”
C. Hopkin's cafe, mighty good, managed by
cousin Mo, waitress Clara
Nickel may also be essential
30
Some minerals required, some by chance…
Images – various plants that use additional elements
Sulfur in mustards
Silicon in horsetails
Uranium in macadamia31nuts
Critical Thinking
• How do you tell which are
required???
32
Critical Thinking
• How do you tell which are
required???
• Hydroponics!
Diagram – a hydroponic experiment
33
Critical Thinking
• How do you tell which are
required???
• Hydroponics!
• How would elements NOT required
enter the plant tissue???
34
Critical Thinking
• How do you tell which are
required???
• Hydroponics!
• How would elements NOT required
enter the plant tissue???
• They are pulled toward the root in the
transpiration stream, and enter
through any membrane channel they
can fit through
35
All plants will exhibit signs of deficiencies…..
Images – signs of deficiency
36
Critical Thinking
• If the deficiency appears first in the older
leaves, is that nutrient mobile or
immobile???
37
Critical Thinking
• If the deficiency appears first in the older
leaves, is that nutrient mobile or
immobile???
• Mobile – it’s being translocated from the
older tissues to the new, growing tissues
• How???
38
Critical Thinking
• If the deficiency appears first in the older
leaves, is that nutrient mobile or
immobile???
• Mobile – it’s being translocated from the
older tissues to the new, growing tissues
• How???
• In the phloem!!!
The older tissue acts as a source
The younger tissue is the sink
39
Fe deficiency in younger leaves
(immobile)
Mg deficiency in older leaves
(mobile)
40
Critical Thinking
• Why would some elements be mobile, and
others not???
41
Critical Thinking
• Why would some elements be mobile, and
others not???
• Some get locked into membranes or other
components that can’t be broken down
42
Most plants get most of their
nutrients from the soil – absorbed
through the roots
Image – roots
43
Soil is not just Dirt!
• Soil is the “skin” of the earth
• Soil provides for virtually all our food
• Soil supports the forests that
maintain the hydrological cycle
• Soil supports virtually all terrestrial
ecosystems – from micro-organisms
to charismatic macro-fauna
44
The results of deforestation are ecological,
economic and social disaster ( )
Image – erosion after tropical deforestation
45
Removing the plants removes the soil’s protective
“blanket” and erosion is almost inevitable
46
Erosion from
deforestation in
Madagascar
More images – erosion
47
Sedimentation from erosion – this represents a
huge loss of soil “capital”
Image – sediments from eroded land flooding out to sea
48
Sediments eroding off Haiti
Image – sediments eroding off Haiti into the sea
49
Dominican
Republic
Image – the political boundary is clear from the deforestation
Haiti
50
Haiti’s drought is caused largely by deforestation –
the hydrological cycle has been snapped
Image – the drought in Haiti, where residents eat mud to survive
51
Deforestation in Warwickshire, England
Maps – deforestation in England and in the US
Deforestation in the US
52
Map – soil loss in the Southern Piedmont of the
US due to deforestation and abusive agricultural
practices
Piedmont soil
erosion in the
southeastern US
53
Image – eroded land in the Southern Piedmont
The USFS Calhoun Experimental Forest in the 1950’s
54
Union County, South Carolina
Loss of soil (along
with the boll weevil)
nearly eliminated
productive
agriculture in the
Southern Piedmont
after the 1920’s –
now most of the
Piedmont is in
industrial pine
plantations because
it can no longer
support productive
agriculture
Maps – loss of farms, rise of industrial
forestry, creating the biological deserts
of pine plantations
55
Social
Justice
You can
help!!!
56
Compassionate Thinking
• What can you do to help???
57
Compassionate Thinking
•
•
•
•
•
•
•
What can you do to help???
Give – time, money
Conserve – resources
Learn
Think
Talk
Activate – take leadership roles
• VOTE!!!!!
There are
3 R’s
58
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
59
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
60
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
61
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
62
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
63
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
64
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
65
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
66
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
67
Soil:
A dynamic natural body in which
plants grow, composed of mineral
and organic materials, air, water,
and living organisms
68
Soil Forming Factors:
Parent Material
Climate
Living Organisms
Topography
Time
All soil forming factors interact!!!
69
Parent Material
• The substrate from which soil forms
• May be bedrock or some deposited
material (sediments, organic material…)
• Determines soil texture, mineral content
• Influences soil structure and pH
70
Igneous rocks form
from molten rock
71
Pegmatite granite with large-grained feldspar (slow cooling)
72
Sedimentary rocks form from deposited
materials
73
Flat sedimentary rocks
Sedimentary rocks after
tectonic thrusting and
folding
74
Metamorphic rocks form from igneous or sedimentary
rocks that have been altered by heat and pressure
75
gneiss
76
In the Charleston area, our soils form from
unconsolidated Coastal Plain sediments
77
Critical Thinking
• Why???
78
Critical Thinking
• Why???
• We were under water from ~ 140 mya to
less than 100,000 years ago
79
Sediments were deposited on top of the
crystalline bedrock during all this time
Soil develops from what’s on top!
80
81
PM
determines
soil texture =
percentage of
sand, silt and
clay
Loam soils
have ~ equal
percentage of
each texture
class
82
C
L
A
Y
83
Clays are especially important
• Tiny (<2um)
Huge surface area per unit mass (1000X more
than same volume of sand)
• Typically platy in structure = vast additional
internal surface area (800 m2/gm)
• Typically clay minerals carry a negative
charge
84
Critical Thinking
• Why is a huge surface area of negative
charge important to soil fertility???
85
Critical Thinking
• Why is a huge surface area of negative
charge important to soil fertility???
• Many essential elements are in the soil
solution in cation form
Clay particles hold these cations and limit
leaching
• Water is also held (remember it’s polar)
Plus, smaller pore size holds more water
86
Most clays carry
negative charge
on both external
and internal
surfaces
87
Cation Exchange – remember the
root cap – protons displace cations
88
Texture also
influences soil
moisture – clays
hold onto more
water
Small pore size
and negative
charge
Relationship between soil
texture, field capacity and
water availability
89
Parent
materials
are
weathered
by other soil
forming
factors to
form soil
90
Soils are
typically
layered, in
horizons,
because of
downward
movement
of water,
clays, etc
91
Critical Thinking
• Which soil horizon has the most biological
activity???
• Why???
92
Critical Thinking
• Which soil horizon has the most biological
activity???
• The “A” horizon – the topsoil
• Why???
• More air, water and organic materials from
the surface
93
“A” Horizon
The topsoil is
the most
biologically
active horizon –
more air, water
and organic
materials from
the surface
94
Soil Profile – a cut that reveals the horizons
95
Climate
• Primarily temperature and precipitation
patterns
• Temperature controls freeze-thaw cycles
that contribute to physical weathering
• Temperature also affects the rate of
biochemical reactions
• Temperature also affects the rate of
decomposition by fungi, bacteria, and
other living organisms
96
Climate
• Precipitation contributes to soil moisture,
which affects plant growth and the activity
of decomposing organisms
• Precipitation affects erosion (the physical
loss of soil particles) and leaching
(chemical losses from the soil solution as
water passes through the soil – this
contributes to profile formation)
97
Major biomes are determined by climate – microclimate
is also important in soil development
98
Living Organisms
• Macro-organisms, including plants and
animals
• Micro-organisms, including bacteria, fungi,
single-celled “protists”, and micro-fauna
• Human activity typically results in abrupt
and very negative changes to soil
99
Living Organisms – Plants
• Contribute organic material – both from
above (shoots) and below (roots), and both
sources affect horizonation
• Help to mix the soil – root channels, wind
throws
• Cycle nutrients from soil to plant and back
(sometimes through animals, always
through decomposers)
• Help prevent soil erosion by breaking the
force of rain, providing a litter layer
100
Same parent
material will
develop into a
different soil
under
different plant
communities
101
Critical Thinking
• Why are grassland soils so dark at the
surface???
102
Critical Thinking
• Why are grassland soils so dark at the
surface???
• Organic material!
• Grasses have a lot
• of fine roots and very
• quick root turnover
• A lot of OM is
• contributed
103
Living Organisms – Animals
• Help to mix the soil by burrowing, some
even “eat” soil (earthworms)
• Contribute
organic material
when they die
• Contribute to
nutrient cycling
104
Critical Thinking
• How do animals contribute to nutrient
cycling???
105
Critical Thinking
• How do animals contribute to nutrient
cycling???
• Plants absorb nutrients from the soil
• Animals turn plant into animal
• Dead animals (plus “excess” biomass)
return those nutrients to the soil via
decomposing fungi, bacteria, etc
• Plants absorb nutrients from the soil…
106
107
Living Organisms – Micro-orgs
• Decompose organic material, cycle
nutrients, add OM
• Trillions/kg of soil (double handful of soil….)
• N-fixing bacteria = supply virtually all N for
plant growth, either free living or in nodule
the nitrogen paradox….bacteria convert
atmospheric N to forms suitable for plant uptake
• Mycorrhizae = mutual symbiotic association
between fungi and roots, present in most
plants, required by some
108
Small animals, soil dwelling micro-fauna, fungi,
bacteria, and other micro-organisms decompose dead
OM, cycling nutrients back into the soil
109
Living Organisms – Micro-orgs
• Decompose organic material, cycle
nutrients, add OM
• Trillions/kg of soil (double handful of soil….)
• N-fixing bacteria = supply virtually all N for
plant growth, either free living or in nodule
The nitrogen paradox….bacteria convert
atmospheric N to forms suitable for plant uptake
• Mycorrhizae = mutual symbiotic association
between fungi and roots, present in most
plants, required by some
110
N-fixing bacteria in symbiotic
mutualisms, mostly with legumes
111
Living Organisms – Micro-orgs
• Decompose organic material, cycle
nutrients, add OM
• Trillions/kg of soil (double handful of soil….)
• N-fixing bacteria = supply virtually all N for
plant growth, either free living or in nodule
the nitrogen paradox….bacteria convert
atmospheric N to forms suitable for plant uptake
• Mycorrhizae = mutual symbiotic association
between fungi and roots, present in most
plants, required by some
112
Critical Thinking
• What do you think mycorrhizae might
contribute to the symbiosis???
113
Critical Thinking
• What do you think mycorrhizae might
contribute to the symbiosis???
• Surface area – LOTS
114
Mycorrhizae are symbiotic mutualisms between
fungi and plants – fungal hyphae vastly
increase surface area for water and nutrient
absorption – 85% of plants depend on them
115
Living Organisms – The human impact
• Removing vegetation dramatically
increases erosion, cultivation exacerbates
• Deforestation can snap hydrological cycles
• Excessive fertilizer and pesticide use
contaminates both soil and water
• Improper irrigation salinates soil
• Wetland drainage damages wetland soils
• and on….
116
Topography – the shape of the land
• Determines the movement of water, thus
affecting erosion and leaching rates
• Determines where water accumulates, which
affects soil moisture, which affects
organismal activity, which affects soils….
• Aspect affects the amount of solar radiation
at the surface, and thus soil temperature
• Large topographic features influence
precipitation patterns
• Even micro-topography influences plant
117
distribution
Topographic Aspect – red and
blue face S and W; green and
yellow face N and E
118
Critical Thinking
• Why are the north and east slopes of a hill
cooler???
119
Critical Thinking
• Why are the north and east slopes of a hill
cooler???
• The hill itself shades those sides
120
Topography – the shape of the land
• Determines the movement of water, thus
affecting erosion and leaching rates
• Determines where water accumulates, which
affects soil moisture, which affects
organismal activity, which affects soils….
• Aspect affects the amount of solar radiation
at the surface, and thus soil temperature
• Large topographic features influence
precipitation patterns
• Even micro-topography influences plant
121
distribution
Orographic lifting makes it rain
122
Critical Thinking
• What the heck is orographic lifting and
why does it cause rain???
123
Critical Thinking
• What the heck is orographic lifting and
why does it cause rain???
• Orographic means that an air mass is
being forced by wind to go up and over a
mountain
124
Critical Thinking
• What the heck is orographic lifting and
why does it cause rain???
• Orographic means that an air mass is
being forced by wind to go up and over a
mountain
• The air mass cools at higher elevations,
condenses, and precipitation falls
125
Orographic lifting causes cooling and
precipitation, rain shadow to the leeward
126
Topography – the shape of the land
• Determines the movement of water, thus
affecting erosion and leaching rates
• Determines where water accumulates, which
affects soil moisture, which affects
organismal activity, which affects soils….
• Aspect affects the amount of solar radiation
at the surface, and thus soil temperature
• Large topographic features influence
precipitation patterns
• Even micro-topography influences plant
127
distribution
Small change
in elevation…
…big
change in
the plant
community!
128
Time….
• The length of time all these factors have
been acting determines the characteristics
of the soil
• The same parent material will develop
different soils as time passes
• Major component of primary succession
129
Soil development on glacial till
130
Soil Forming Factors:
Parent Material
Climate
Living Organisms
Topography
Time
Remember – all soil forming
factors interact!!!
131
The Rhizosphere
The area of interaction between root and soil.
A huge volume of soil, but a very narrow zone
132
The rhizosphere is the zone of cation
exchange, nutrient and water uptake
133
The Rhizosphere
• Complex zone with many interacting factors
• Plant affects soil through compounds
secreted by the plant’s roots
• Relative proportions of nutrients in the soil
solution can affect uptake of all nutrients
• Also, different species have different
nutrient requirements
• Rhizosphere is the control zone for
plant/soil interactions
134
Some plants use alternate methods
to absorb some nutrients
• Parasites, saprophytes,
carnivores
135
Key Concepts: QUESTIONS???
• Resources
Which are required
How they are used
• Essential elements
What they are
What they do
• Soils and soil forming factors
• The rhizosphere
• Some alternate methods to acquire
nutrients
136