Plant Fertilization Strategies
20152015 UT Extension Master Gardener Winter School
2015 UT Extension Master Gardener Winter School
Debbie Joines
Manager
Soil, Plant and Pest Center
Nashville
Outline
• Plant nutrition
• Why use soil, media or tissue analysis?
• Proper sample
procedure
• Fertilization
Systematic Approach
• Sun/shade
• Soil depth/drainage
• Slope
• Traffic- people & pets
• Water
• Planting depth
• Disease/Insects
• Plant nutrition
Required Plant NutrientsMacronutrients
• Primary• Nitrogen (N)
• Phosphorus (P)
• Potassium (K)
• Secondary• Calcium (Ca)
• Magnesium (Mg)
• Sulfur (S)
Micronutrients*• Boron-B
• Copper- Cu
• Manganese – Mn
• Iron – Fe
• Zinc - Zn
• Molybdenum – Mo
• Chlorine – Cl
*Required in very small amounts.
Nitrogen• Required for chlorophyll synthesis
• Produces dark green color
• Plant available forms• Ammonium (NH4)
• Slowly released
• Nitrate (NO3)• Used in large amounts
• Very mobile-Rapid uptake (and loss)
• Deficiency symptoms– Slow, stunted growth
– Yellowing on oldest leaves first
Nitrogen
• Nitrification must occur for plant availability
– Soil pH reduces nitrification
– Moisture- waterlogged reduces
– Temperature- s/b above freezing and below
85oF
– Aeration- needs oxygen
Phosphorus
• Root growth and bloom/seed production
• Essential for growth & maturity
• Plant available forms
– Phosphate (P2O5)
• Deficiency symptoms
– Stunted plants
– Purple leaf coloring
– Distorted leaves
Potassium (K)
• Strong stalks and stems
• Cell function & photosynthesis
• Winter hardiness
• Plant available form
– K+
• Deficiency symptoms
– Firing or scorching
– Lodging
Calcium
• Root and leaf development
• Metabolic functions
• Cell wall structure
• Plant available form
– Ca2+
• Deficiency symptoms
– Abnormal growing points
– Premature shedding buds
Magnesium
• Active in photosynthesis
• Aids phosphate metabolism
• Plant available form
– Mg2+
• Deficiency symptoms
– First to appear on older (lower) leaves
– Interveinal yellowing
Photo credit: IPNI
Sulfur
• Chlorophyll production (green)
• N fixation in legumes
• Enzymes and vitamins
• Plant available form
– SO42-
• Deficiency symptoms
– Pale green color
– Spindly growth
Fe deficiency can make more
susceptible to leaf spot
Rust can mimic nutritional deficiency
Low fertility in Dogwood
Cold or winter injury
Soil Analysis
• Only reliable method of determining nutrient
availability
• Critical to determine pH,
nutrient levels
• Cost efficient
• Environmentally sound
Sample specifics
• 6 inch depth
• Representative- mix
cores
• “Soil test results can
be no better than
sample submitted”
• At least one cup of
mixture
How to sample
Soil pH
• Measures acidity of soil
• Increased acidity reduces availability
• Alkaline soils may induce toxicities
• 6.5 Target for most plants
• 5.5 Acid loving shrubs
Relative Nutrient Availability at Varying Soil pH Values
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0
extreme strong slight
acidity acidity acidity slight alkalinity strong alkalinity
nitrogen
phosphorus
potassium
sulfur
calcium
magnesium
iron
molybdenum
manganese
copper and zinc
boron
Interpretation of Soil Test Results
• Low (L)- If nutrient is not applied, deficiency symptoms may occur; up to 75% reduction in yield or performance
• Medium (M)- Plants may or may not respond; should produce 75% or more
• High (H)- Soil should produce at or near 100% of potential; amounts recommended to maintain
• Very High (V)- > 100% or Excess
Container Media (soil-less mix)
• Plant tissue analysis is a quantitative
measurement of nutrients in leaves
• Nutritional status is revealed when used in
combination with soil testing. Nutrient availability (soil) + uptake (plant tissue)
Plant Tissue
Analysis
Why Tissue Analysis?
• Monitor nutritional statusLeaf samples taken same time of day over period of
time
Collect from same area of field
Can reveal “hidden” hunger during growing season
• Troubleshoot problems/confirmation Sample most fully mature leaves from plant(s)
Sampling Procedure
• Varies; at least 25 leaves- 50 best
– 4 – 8 leaves per tree
• Representative, plentiful sample:1/2 gal.
• Package in paper bag
• Ship during week; avoid weekends
• No diseased or dead material
• Do not submit leaves recently treated with chemicals
• Wash with mild detergent if needed
Parts of plant to sample
Photo credit: Ag Services Lab, Clemson University
Interpretation of Results
Adapted from: Sufficiency Ranges for Plant Analysis in the Southern United States, July 2000. Southern
Cooperative Series Bulletin, SCSB #394.
Applying Fertilizer/Amendments
• Chemical fertilizers are generally in plant
available forms
• Organic amendments not composted (or
incomplete) can create nutrient deficiencies
• Most gardens/lawns/ornamentals require ½ to 1
lb. nitrogen, then 0 – 3 lbs. P &/or K (per 1,000
sq. feet)
• 2 cups pelleted fertilizer typically weighs 1 lb.
Fertilizer Calculations
• Divide pounds of nutrient needed by
percentage of nutrient in
fertilizer/amendment
– 1 lb. nitrogen
• 1 / 0.46 (urea 46-0-0) = 2.2 lbs.
• 1/ 0.07 (SBM 7-1.2-1.5) = 14.3 lbs.
- 3 lbs. 34-0-0
• 3 * 0.34 = 1 lb. N
Key Points
• Use a systematic approach
• Evaluate history and current conditions
• Utilize soil testing before applying lime or
nutritional amendments
• If problems persist, try plant tissue analysis
• Follow recommendations for optimal results
• Stay informed
Acknowledgements
AESL Plant Analysis Handbook , 2009. University of Georgia
Agricultural and Environmental Services Lab.
http://aesl.ces.uga.edu/publications/plant/index.htm
Reference Sufficiency Ranges for Plant Analysis in the Southern
Region of the United States, 2000. Southern Cooperative
Series Bulletin, SCSB# 394.
http://www.clemson.edu/agsrvlb/sera6/publications1.htm
www.facebook.com/SoilPlantPestCenter