Download Nutrients, pH and Fertility

Nutrients, pH and Fertility
Topic 2035
Anna Blight
Cation Exchange Capacity
(CEC)
• A measure of nutrient holding capacity of
soil
• Cation exchange takes place when the root
makes contact with negatively charged clay
or humus particle
• Root exchanges H+ ions for other cations
which are absorbed by roots for nutrition
CEC
• The amount of these positively charged cations a
soil can hold is described as the CEC
• Expressed in milliequivalents per 100 grams
(meq/100g) of soil
• The larger this number, the more cations the soil
can hold
• A clay soil will have a larger CEC than a sandy
soil
Cations are + charged
• Think of the ‘t’ in cation and +
• Ca++ Mg+ H+ K+ NH4+
• H+ easily hydrated to H20 when joined with
OH- ion
• NH4+ (ammonium) adheres to clay or
humus and resists leaching until converted
to NO3- by micro-organisms
Anions are • Clay and humus have many negative
charges
• NO3- is nitrate form of Nitrogen
• Most preferred form of plants
• Highly soluble and easily leached from soil
because of negative charge
pH
• Measure of H+ concentration
• pH is logarithmic function, each number is
10 times greater than the number before
• Range between 1 to 14
pH
• The pH of water and fertilizer also
important
• Influences nutrient availability
• Lots of plants like slightly acid soil of 6.5 to
6.8.
Low pH
• High H+
• ACID soil
• pH below 7
• If pH is too low, add lime
High pH
• Low H+
• ALKALINE soil
• pH above 7
• If pH is too high, add sulfur
Fertility
• Soil tests can determine pH and nutrient
availability in the soil
• Fertilizer analysis is represented as a
percentage by weight of elemental N, P2O5
and K2O
• 10-10-10 fertilizer contains 10% nitrogen,
4.4% P and 8.3% K
Fertilizer analysis
• P2O5 is 44% actual elemental Phosphorus
• Multiply P205 x .44 to obtain P
• K2O is 83% actual elemental Potassium
• Multiply K2O x .83 to obtain K
CHOPKNSCaFeMg
• “See Hopkins Café, Mighty Good!”
• Carbon, Hydrogen, Oxygen, Phosphorus,
Potassium, Nitrogen, Sulfur, Calcium, Iron
and Magnesium
Macronutrients
• NPK
• Nitrogen, Phosphorus, Potassium
• Most important nutrients used in larger
quantities by plants
• Secondary are Calcium, Magnesium, and
Sulfur (Ca Mg S)
Micronutrients
• Used in smaller quantities by plants
• Iron, Copper, Zinc
• Manganese, Boron, Molybdenum
• Chlorine
Nitrogen
• Important for overall growth of plant
• Deficiency symptoms are small, pale yellow
leaves
• Stunted growth
Phosphorus
• Growth and flower
and root
development
• Deficient plants
show purple/red on
the older leaves or
dead areas on
leaves
Potassium (K)
• Regulation of water within plant cell and
water loss through transpiration
• Disease resistance
• Potassium deficiency shows mottled
chlorosis in leaves, or dead areas on leaf
tips and margins
Resources
• http://aged.ces.uga.edu/lessons/course01461.htm
• Integrated Plant Health Management Training Program for
Landscape Maintenance Providers, MSU Nursery and
Landscape Team
• http://hubcap.clemson.edu/~blpprt/bobweb/BOBWEB24.H
TM
• http://ltpwww.gsfc.nasa.gov/globe/index.htm