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