The following is information on how to calibrate your fertilizer injector by the electrical conductivity method.
Electrical Conductivity Method
1 Electrical Conductivity Meter
1 Standard Solution for Meter Calibration
1 Plastic Measuring Cup
Calibrate the EC Meter according to the directions included with the meter before use.
1) Run the irrigation water for at least 5 minutes without any injected fertilizer, this can be done before the fertilizer injector, or after the injector with the injector turned off. Collect a sample of this in the plastic measuring cup. Using the calibrated meter, take the EC reading from this sample.
2) Collect a sample of fertilizer solution at the output end of the hose after allowing the injector to run for at least 5 minutes in the cleaned and dried plastic measuring cup. Subtract the EC reading for the clear water from the EC reading for the fertilizer solution.
Note this number: _____ = EC of the Fertilizer Solution
Many fertilizer companies list the Electrical Conductivity for various dilutions on the bag or publish this information in literature available from the manufacturer. Compare your EC reading of the Fertilizer Solution with that provided by the manufacturer of the material.
Information by Chuck Schuster int the September 4, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center