Greenhouse and Nursery - Check your Fertilizer Injectors

You should check your fertilizer injectors before each growing cycle for proper function. The following is some more information.

This is also a good time to check your fertilizer injector to be sure it is working correctly. To do this, take a fertilizer sample from the end of the hose the next time you fertilize and put it in a clean plastic container for testing. Test the sample using a conductivity meter or send a sample to the University of Delaware Soil Test Lab.

1) Test and record the conductivity of the water to be mixed with the fertilizer.

2) Test the conductivity of the fertilizer and water mixture.

3) Subtract the water conductivity determined in #1 above.

4) The result is an accurate indication of how much fertilizer is present (the higher the conductivity means more fertilizer).

Fertilizer companies and suppliers often can provide a chart relating conductivity to parts per million concentrations of their various fertilizers. Ask your fertilizer company for their electrical conductivity chart and compare your fertilizer reading to the chart.

For example, a 100 ppm solution of 20-20-20 from company A had a corresponding meter reading of 0.41, from company B the meter reading was 0.46. A 100 ppm 15-0-15 solution was 0.69 with one company and 0.76 with another company.

Information taken in part from Floriculture Timely Topics from UMASS Extension.