The Bugwood Network

Quality Control and Nutrient Management

Dr. John M. Ruter - University of Georgia - Tifton

Ruter, J.M. 2001. Quality Control and Nutrient Management In: D.J. Moorhead (ed.) Proceedings of the Longleaf Pine Container Production Workshop. Jan. 16-18, 2001. Tifton, GA. USDA Forest Service and University of Georgia.

Quality Control

  1. Develop a simple flow chart for your production process
  2. Identify the inputs necessary for each stage of production substrate, containers, starter material, water, etc..
  3. Develop specifications for each input pH = 5.5 to 6.0, 200 ppm N, etc..
  4. Develop procedures to verify that each input meets specifications test EC for each batch of substrate

Testing to see if your fertilizer injector is working properly! Every company should provide charts.

20-20-20 General Purpose
Soluble Salts
(dS/m or mMhos/cm)

50 0.20
100 0.40
150 0.60
200 0.80
250 1.00
300 1.20

Measuring Soluble Salts and pH with the Pour-Through Method

Growers have been slow to adopt regular testing because:

  1. Lack of uniformity in testing procedures
  2. Limited experience of growers in applying results
  3. Cost of testing procedures and equipment

Advantages of the Pour-Through Method

  1. Short period required for sample extraction
  2. Soluble salts and pH can be measured in the field
  3. No container substrate is handled
  4. No specialized equipment is required for extraction
  5. No chance of rupturing controlled release fertilizer prills

Pour-Through Procedure

  1. Irrigate crop as needed
  2. Collect samples ~ 1 hr. after watering
  3. Place tray over a plastic saucer (bucket, etc) to collect leachate. Elevate bottom of container.
  4. Add distilled water to top of cells and collect leachate. Add enough water to collect 50 ml or 2 oz. of leachate.
  5. Measure pH and soluble salts with appropriate meters
  6. Graphically track on weekly basis!

Interpretation for Nursery Crops

pH = 5.2-6.2
EC (sensitive crops on liquid feed) 0.5 to 0.75 dS/m
EC (general crops on liquid feed) 0.75 to 1.50 dS/m
EC (controlled release fertilizer) 0.20 to 1.00 dS/m

Factors for Consideration

  1. Stage of growth
  2. Time of year
  3. Fertilizer (liquid versus controlled release)
  4. Substrate
  5. Environment

Keep in mind that different labs use different testing procedures and interpretation will be different!!!

What to do!
If soluble salts are high Leach or reduce liquid feed
If soluble salts are low Fertilize and check irrigation volume
If pH is high 1)inject acid, 2) iron sulfate, 3) use ammonium-N fertilizers, 4) check alkalinity of irrigation water
If pH is low 1) dolomitic lime, 2) calcium carbonate, 3)hydrated lime, 4) liquid lime, 5) potassium bicarbonate, 6) nitrate-N fertilizers
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Last updated on Tuesday, July 09, 2002 at 10:18 AM
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