Lecture 6 – Plant Nutrition and Soils

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Lecture 6 Plant Nutrition and Soils
Image a soil profile
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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

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Resource requirements for plant growth???
?
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Where do plants get these resources???
?
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Where do plants get these resources???
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Image root system of a grass
Diagram plant resource requirements and sources
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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

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Critical Thinking

• Does wood have such a high percentage of water???

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Critical Thinking

• Does wood have such a high percentage of water???

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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

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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

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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

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DRY plant tissue composition by weight

• 45 carbon
• 45 oxygen
• 6 hydrogen
• 5 inorganic mineral nutrients

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DRY plant tissue composition by weight

• 45 carbon from ?? CO2
• 45 oxygen from ?? CO2
• 6 hydrogen from ?? water
• 5 inorganic mineral nutrients from ?? soil

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DRY plant tissue composition by weight

• 45 carbon from
• 45 oxygen from
• 6 hydrogen from
• 5 inorganic mineral nutrients from

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DRY plant tissue composition by weight

• 45 carbon from
• 45 oxygen from
• 6 hydrogen from
• 5 inorganic mineral nutrients from

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C, H, O source and fate in photosynthesis
Diagram what goes into photosynthesis and what
comes out
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DRY plant tissue composition by weight

• 45 carbon from CO2
• 45 oxygen from CO2
• 6 hydrogen from water
• 5 inorganic mineral nutrients from
• 0.75-1 of wet weight, but many are essential to
  plant growth and function

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Critical Thinking

• What is the difference between a chemical
  element, a molecule and a macromolecule???

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Critical Thinking

• What is the difference between a chemical
  element, a molecule and a macromolecule???

Diagram structure of chlorophyll molecule
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Essential Elements

• Chemical elements
• Not molecules, though some are delivered in that
  form N vs. NO3-
• Required for growth and function of the plant
• Cant be replaced by some other element
• Some contribute to structural components
• Some contribute to metabolic processes or the
  maintenance of homeostasis

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Essential elements in structural plant components

• What are some essential structural components???

?
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Essential elements in structural plant components
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Essential elements in structural plant components
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Essential elements for metabolic processes

• What are some essential molecules used in
  metabolic processes???

?
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Essential elements for metabolic processes
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Essential elements for metabolic processes
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Macro Nutrients vs. Micro Nutrients
mass

• Nitrogen
• Potassium
• Calcium
• Magnesium
• Phosphorous
• Sulfur

• Chlorine, Iron, Boron, Manganese, Zinc, Copper
  and Molybdenum
• Some plants also require Nickel, Sodium, Silicon,
  Selenium or others

All used in large quantities to support the
structures and processes listed before
Mostly used in enzymes, as enzyme cofactors or in
electron transfers often reused, less required
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Study table in book!
Table essential nutrients, both macro and micro
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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

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Some minerals required, some by chance
Images various plants that use additional
elements
Sulfur in mustards
Silicon in horsetails
Uranium in macadamia nuts
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Critical Thinking

• How do you tell which are required???

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Critical Thinking

• How do you tell which are required???

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Critical Thinking

• How do you tell which are required???
• How would elements NOT required enter the plant
  tissue???

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Critical Thinking

• How do you tell which are required???
• How would elements NOT required enter the plant
  tissue???

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All plants will exhibit signs of deficiencies..
Images signs of deficiency
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Critical Thinking

• If the deficiency appears first in the older
  leaves, is that nutrient mobile or immobile???

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Critical Thinking

• If the deficiency appears first in the older
  leaves, is that nutrient mobile or immobile???
• How???

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Critical Thinking

• If the deficiency appears first in the older
  leaves, is that nutrient mobile or immobile???
• How???

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Fe deficiency in younger leaves ()
Mg deficiency in older leaves ()
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Critical Thinking

• Why would some elements be mobile, and others
  not???

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Critical Thinking

• Why would some elements be mobile, and others
  not???

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Most plants get most of their nutrients from the
soil absorbed through the roots
Image roots
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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

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The results of deforestation are ecological,
economic and social disaster ( )
Image erosion after tropical deforestation
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Removing the plants removes the soils protective
blanket and erosion is almost inevitable
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Erosion from deforestation in Madagascar
More images erosion
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Sedimentation from erosion this represents a
huge loss of soil capital
Image sediments from eroded land flooding out
to sea
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Sediments eroding off Haiti
Image sediments eroding off Haiti into the sea
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Dominican Republic
Image the political boundary is clear from the
deforestation
Haiti
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Haitis drought is caused largely by
deforestation the hydrological cycle has been
snapped
Image the drought in Haiti, where residents eat
mud to survive
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Deforestation in Warwickshire, England
Maps deforestation in England and in the US
Deforestation in the US
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Map soil loss in the Southern Piedmont of the
US due to deforestation and abusive agricultural
practices
Piedmont soil erosion in the southeastern US
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Image eroded land in the Southern Piedmont
The USFS Calhoun Experimental Forest in the
1950s Union County, South Carolina
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Loss of soil (along with the boll weevil) nearly
eliminated productive agriculture in the Southern
Piedmont after the 1920s 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
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Social Justice You can help!!!
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Compassionate Thinking

• What can you do to help???

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Compassionate Thinking

• What can you do to help???

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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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SoilA dynamic natural body in which plants
grow, composed of mineral and organic materials,
air, water, and living organisms
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Soil Forming FactorsParent MaterialClimateLiv
ing OrganismsTopographyTime
All soil forming factors interact!!!
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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

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Igneous rocks form from molten rock
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Pegmatite granite with large-grained feldspar
(slow cooling)
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Sedimentary rocks form from deposited materials
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Flat sedimentary rocks
Sedimentary rocks after tectonic thrusting and
folding
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Metamorphic rocks form from igneous or
sedimentary rocks that have been altered by heat
and pressure
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gneiss
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In the Charleston area, our soils form from
unconsolidated Coastal Plain sediments
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Critical Thinking

• Why???

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Critical Thinking

• Why???

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PM determines soil texture percentage of sand,
silt and clay Loam soils have equal
percentage of each texture class
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CLAY
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Clays are especially important

• Tiny (lt2um)
• 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

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Critical Thinking

• Why is a huge surface area of negative charge
  important to soil fertility???

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Critical Thinking

• Why is a huge surface area of negative charge
  important to soil fertility???

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Most clays carry negative charge on both external
and internal surfaces
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Cation Exchange remember the root cap protons
displace cations
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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
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Parent materials are weathered by other soil
forming factors to form soil
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Soils are typically layered, in horizons, because
of downward movement of water, clays, etc
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Critical Thinking

• Which soil horizon has the most biological
  activity???
• Why???

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Critical Thinking

• Which soil horizon has the most biological
  activity???
• Why???

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A Horizon The topsoil is the most biologically
active horizon more air, water and organic
materials from the surface
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Soil Profile a cut that reveals the horizons
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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

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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)

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Major biomes are determined by climate
microclimate is also important in soil development
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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

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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

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Same parent material will develop into a
different soil under different plant communities
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Critical Thinking

• Why are grassland soils so dark at the surface???

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Critical Thinking

• Why are grassland soils so dark at the surface???

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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

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Critical Thinking

• How do animals contribute to nutrient cycling???

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Critical Thinking

• How do animals contribute to nutrient cycling???

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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

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Small animals, soil dwelling micro-fauna, fungi,
bacteria, and other micro-organisms decompose
dead OM, cycling nutrients back into the soil
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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

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N-fixing bacteria in symbiotic mutualisms, mostly
with legumes
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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

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Critical Thinking

• What do you think mycorrhizae might contribute to
  the symbiosis???

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Critical Thinking

• What do you think mycorrhizae might contribute to
  the symbiosis???

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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
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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.

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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
  distribution

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Topographic Aspect red and blue face S and W
green and yellow face N and E
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Critical Thinking

• Why are the north and east slopes of a hill
  cooler???

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Critical Thinking

• Why are the north and east slopes of a hill
  cooler???

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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
  distribution

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Orographic lifting makes it rain
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Critical Thinking

• What the heck is orographic lifting and why does
  it cause rain???

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Critical Thinking

• What the heck is orographic lifting and why does
  it cause rain???

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Critical Thinking

• What the heck is orographic lifting and why does
  it cause rain???

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Orographic lifting causes cooling and
precipitation, rain shadow to the leeward
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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
  distribution

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Small change in elevation
big change in the plant community!
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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

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Soil development on glacial till
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Soil Forming FactorsParent MaterialClimateLiv
ing OrganismsTopographyTime
Remember all soil forming factors interact!!!
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The Rhizosphere
The area of interaction between root and soil. A
huge volume of soil, but a very narrow zone
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The rhizosphere is the zone of cation exchange,
nutrient and water uptake
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The Rhizosphere

• Complex zone with many interacting factors
• Plant affects soil through compounds secreted by
  the plants 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

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Some plants use alternate methods to absorb some
nutrients

• Parasites, saprophytes, carnivores

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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