Water-based Media Extraction



Water-based extractions of soilless root media are simply methods to solubilize nutrients in the root medium so that their concentrations can be measured as an estimate of nutrient availability for uptake by the plant. Water-based extraction procedures include saturated medium extractions (SME), 1:2 medium dilutions, pour-thru extractions, and (for plugs) a squeeze method. Analyses can be run on the extracted solution, including NH4-N, NO3-N, PO4-P, K, Ca, Mg, and other nutrient ions, as well as pH and EC.

FACT SHEET:Submission Procedures for Samples
Maria collects root medium samples from several pots that contain plants showing the symptomology and combines these into one sample, and does the same for plants that appear healthy. She then sends the samples to Scott’s Testing Lab in Allentown, Pennsylvania, where an SME is completed and analyzed for most macro- and micronutrients.


A helpful guide to interpreting results from a substrate analysis:
Greenhouse Substrates and Fertilization
Douglas A. Bailey, William C. Fonteno, and Paul V. Nelson, North Carolina State University
See p.11 for interpretation guidelines for tests results.
Results From Plants Showing Symptoms (ppm) From Plants without Symptoms (ppm)
NO3-N 126 132
NH4-N 7 7
P 11 9
K 198 174
Ca 219 197
Mg 71 68
Fe 2.3 2.6
Mn 0.9 0.7
Zn 0.4 0.5
Cu 0.2 0.3
Other Analysis    
pH 6.25 6.31
Electrical Conductivity (mmhos/cm) 0.80 0.74



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