Check Your Greenhouse Crop pH and EC Lately?
Make sure you have the correct pH and soluble salts in your growing media for the plants you’re growing now.
Greenhouse growers who have been in business a long time and those new to the business need to remember some plant-growing basics when plugs, cuttings, or established plants are not putting on the growth you expect.
Have you taken a pH reading and an EC or soluble salts reading? All greenhouse growers should have a portable pH meter and EC meter (solubridge) available to periodically check their growing media. When a problem is noted, collect a few tablespoons of growing media from at least five containers, five cell packs or one per row from five different plug trays. Run a pH and EC test on each of the five samples. If they show similar results, you can feel comfortable you don’t need a larger sample size. There are a couple of different sampling procedures that can be used in greenhouse crops including: the PourThru method, which utilizes the leachate water that is recovered from the container for analysis; or the 1:2 dilution process, which utilizes a media slurry for the analysis.
Both of these on-farm greenhouse tests will give you useful information on the pH and EC of the growing media if performed correctly. Details on how to conduct both methods are described in Purdue Extension Bulletin HO-277-W, entitled “pH and Electrical Conductivity Measurements in Soilless Substrates” available at: www.extension.purdue.edu/extmedia/HO/HO-237-W.pdf
For more comprehensive information on the PourThru method, check out the NC State University document “Monitoring and Managing pH and EC Using the PourThru Extraction Method” available at www.ces.ncsu.edu/depts/hort/floriculture/hils/HIL590.pdf.
Soilless greenhouse media with a pH of 5.4 to 6.2 will allow fertilizer nutrients to be available for plant growth for most plants. However, each plant has its own optimal range for growth. The publications listed above have tables that show acceptable pH and EC readings for most commonly grown greenhouse crops.
Don’t forget that pH meters need to be calibrated before use. Remember to have a set of pH standard solutions (pH 4.0 and 7.0) available on hand. They can be purchased from your greenhouse supply firm. Often the calibration solutions I see in a greenhouse are old and no longer usable. Buy a new set at least once each season. Use them to calibrate your pH meter and you’ll feel better about the results the meter provides.