PourThru Extraction
Win Dunwell, Amy Fulcher and Carey Grable
UKREC Nursery Crop Development Center, Princeton, KY
For a video of how the UKREC Hort Group does it see https://www.youtube.com/watch?v=uGIOAaiZ0s4
30 minutes – 2 hours after irrigation. Whichever delay after irrigation it should always be the same for comnparison of one sampling date to another.
Set the plant container in a shallow pan. It can be of value to use a spacer to raise the container above pan surface.
Pour ½ cup (4 fl. oz). over the media (pine bark/sand more for mixes with peat or compost) surface of a one gallon container or 1.5 cups over a three gallon container.
Place the EC probe in the leachate/extract in the pan or pour the leached/extracted liquid from the pan into the EC meter cup for measurement.
Read the meter. We use a Myron-L AG-5 or AG6/PH or Hanna HI9811-5 (EC&pH) or Hanna equivalent.
To test the conductivity of media leachates/extracts:
Test and record the conductivity of the irrigation water.
Test the conductivity of the leachate/extract
Subtract the water conductivity from the leachate/extract conductivity.
The resulting figure is an accurate indication of how much fertilizer is present.
Desirable nutritional levels for Virginia Tech Extraction Method (VTEM) interpretation of the solution, liquid or CRF fertilizers.z | ||
. | Desirable levels y | |
Nutrient parameter | Solution only or | CRF only |
pH | 5.0 to 6.0 | 5.0 to 6.0 |
EC, dS/m (mmhos/cm) | 0.5 to 1.0 | 0.2 to 0.5 |
Nitrate-N, mgL (ppm) | 50 to 100 | 15 to 25 |
Phosphorus, mg/L | 10 to 15 | 5 to 10 |
Potassium, mg/L | 30 to 50 | 10 to 20 |
Calcium, mg/L | 20 to 40 | 20 to 40 |
Magnesium, mg/L | 15 to 20 | 15 to 20 |
Manganese, mg/L | 0.3 | 0.3 |
Iron, mg/L | 0.5 | 0.5 |
Zinc, mg/L | 0.2 | 0.2 |
Copper. mg/L | 0.02 | 0.02 |
Boron, mg/L | 0.05 | 0.05 |
z Table and data adapted from Best Management Practices: Guide for Producing Container-Grown Plants; Southern Nursery Association. Marietta, GA. (Yeager, et al., 1997).