Plant Nutrition and Soils
Chapter 29
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
Essential Elements
Three criteria are used to judge essentiality
1) If it is needed for the plant to complete its life
cycle.
2) If it is part of any molecule or constituent of
the plant that is itself essential.
a) Magnesium in chlorophyll molecule.
b) Nitrogen in proteins.
3) If deficiency symptoms appear in the absence
of the element.
2 Types of Essential Elements
• Macronutrients- required in large amounts.
– 1000 mg/kg or > 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
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.
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.
Global Nitrogen and Phosphorus Use
Nitrogen Losses
~ 1500 lbs/day
or $500/day!
Asynchrony Between N Supply and Demand
Source: G. Philip Robertson IN Ecology in Agriculture, L.E. Jackson, ed.
NUISANCE ALGAE BLOOMS
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/
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).
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.
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
< 2 µm
• Pore Space- the space
around the soil particles.
– Air
– Water
Plant Pathology- bacteria
Plant Pathology- viruses
Plant Pathology- fungi