|
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
- Develop a simple flow chart for your production process
- Identify the inputs necessary for each stage of production substrate, containers, starter material, water, etc..
- Develop specifications for each input pH = 5.5 to 6.0, 200 ppm N, etc..
- 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.
Nitrogen
(ppm) |
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:
- Lack of uniformity in testing procedures
- Limited experience of growers in applying results
- Cost of testing procedures and equipment
Advantages of the Pour-Through Method
- Short period required for sample extraction
- Soluble salts and pH can be measured in the field
- No container substrate is handled
- No specialized equipment is required for extraction
- No chance of rupturing controlled release fertilizer prills
Pour-Through Procedure
- Irrigate crop as needed
- Collect samples ~ 1 hr. after watering
- Place tray over a plastic saucer (bucket, etc) to collect leachate.
Elevate bottom of container.
- Add distilled water to top of cells and collect leachate. Add
enough water to collect 50 ml or 2 oz. of leachate.
- Measure pH and soluble salts with appropriate meters
- 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
- Stage of growth
- Time of year
- Fertilizer (liquid versus controlled release)
- Substrate
- 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 |
|
