Plant Nutrition and Soils

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Plant Nutrition and Soils

• Chapter 29

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Plant Nutrition

• Plant Nutrition- uptake from the environment of
  all raw materials required for essential
  biochemical processes.
• More than 60 elements have been identified in
  plants.
• 1880s- ten chemical elements were designated as
  essential for plant growth.
• Carbon, hydrogen, oxygen, potassium, calcium,
  magnesium, nitrogen, phosphorus, sulfur, iron.
• 1900s- manganese, zinc, copper, chlorine, boron,
  molybdenum, and finally nickel.

17 Essential Elements
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Essential Elements

• Three criteria are used to judge essentiality
• If it is needed for the plant to complete its
  life cycle.
• If it is part of any molecule or constituent of
  the plant that is itself essential.
• Magnesium in chlorophyll molecule.
• Nitrogen in proteins.
• If deficiency symptoms appear in the absence of
  the element.

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2 Types of Essential Elements

• Macronutrients- required in large amounts.
• 1000 mg/kg or gt of dry matter.
• Micronutrients (trace elements)- required in very
  small amounts.
• 100 mg/kg of dry matter.
• Certain plants contain unusually
  high and low amounts of specific
  elements.

Silicon
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Macronutrient Functions

• Sulfur- amino acids and coenzyme A.
• Phosphorus- ATP, nucleic acids, phospholipids.
• Magnesium- chlorophyll molecule.
• Calcium- cell walls, cofactors, cellular
  membrane.
• Potassium- osmosis and ionic balance, stomatal
  activity.
• Nitrogen- amino acids, proteins, nucleotides,
  nucleic acids, chlorophylls.
• Oxygen, Carbon, and Hydrogen- almost all chemical
  molecules, 96 of the plant.

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Micronutrient Functions

• Molybdenum- nitrogen fixation and nitrate
  reduction.
• Nickel- enzyme functioning in nitrogen
  metabolism.
• Copper- involved in some REDOX reactions.
• Zinc- activator or component of many enzymes.
• Manganese- enzyme activator, membrane integrity,
  oxygen release in PSN.
• Boron- Ca2 utilization, nucleic acid synthesis,
  membrane integrity.
• Iron- chlorophyll synthesis.
• Chlorine- osmosis and ionic balance.

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Global Nitrogen and Phosphorus Use
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Nitrogen Losses
1500 lbs/day or 500/day!
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Asynchrony Between N Supply and Demand
Source G. Philip Robertson IN Ecology in
Agriculture, L.E. Jackson, ed.
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NUISANCE ALGAE BLOOMS
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Eutrophication Lake Tahoe story
Data courtesy of C.R. goldman and J.E. Reuter,
Tahoe Reesrach Group, U. of California-Davis,
http//www.news.ucdavis.edu/tahoetv/
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Soil

• Soil- primary nutrient (inorganic ions), water,
  suitable gaseous environment, and support medium
  for plants.
• Provides a chemical and physical environment for
  plant growth.
• Minerals- naturally occuring inorganic compounds
  that are usually composed of two or more
  elements. i.e.- Quartz (SiO2), Calcite (CaCO3).

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Soil Layers (Horizons)

• Soils consists of at least 3 horizons (layers)
• A Horizon topsoil.
• B Horizon subsoil.
• C Horizon soil base.
• Bedrock below the horizon.

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Soils Are Composed of Solid Matter and Pore Space

• Solid Matter- fragments of rock and minerals in
  the soil.
• Coarse Sand 200-2000 µm
• Fine Sand 20-200 µm
• Silt 2-20 µm
• Clay lt 2 µm
• Pore Space- the space around the soil particles.
• Air
• Water

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Plant Pathology- bacteria
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Plant Pathology- viruses
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Plant Pathology- fungi