Deficiency or pH problem?
Growers at some stage will experience nutrient deficiencies of some kind. Deficiencies happen when certain macro or micro nutrients aren’t available for the plant, most likely because of pH. A salt build up can also be seen as a pH problem as extra nutrients would cause pH to drop in the root zone. Thats why it’s so important to calibrate your pH meter regularly.
Say you’re mixing a nutrient solution and correcting that solution to a pH of 6.2. You could easily be feeding outside of the desired pH range if your meter was out by 0.4 even. That would leave you with a pH of 6.6.
Flushing with pH corrected solution or water will usually fix these problems, as long as your pH meter is accurate. Depending on the meter you have, it needs to be calibrated regularly to be accurate. The good meters can go up to a month and not be that far off when calibrated again. Some very cheap meters need to be calibrated before every use.
Which pH calibration fluid to use?
Get the calibration fluid that’s closest to the pH you work at. Hydro growers correcting solution to a pH of 5.5 for example would calibrate to 4.0. Organic growers correcting water to 6.0 would calibrate their pH meter to 7.0
There is also the 2 point calibration technique used by some high end meters,. This enables meters to be more accurate across the linear equation. Calibrate the meter to 2 points, 4.0 and 7.0 by repeating the process below with more than one calibration fluid.
How to calibrate you pH meter
If you can, rinse your pH meter’s probe end off with distilled water. If you don’t have any, clean tap water is fine.
Pour a small amount of calibration fluid into a clean and dry container like a shot glass or small cup. Anything just big enough to submerge to probe into. Don’t use any metal containers. The pH meter will either have an electronic or manual calibration
If electronic, submerge the probe into the calibration fluid and press the calibration button, select which pH to calibrate to and press enter. The pH to calibrate to would depend on the calibration fluid you bought. The meter will let you know when it’s done.
If manual calibration, it would have come with a screw driver. Somewhere on the meter, sometimes in the battery compartment, there is a small screw. Submerge the pH meter’s probe into the calibration fluid. Using the screw driver turn the screw slowly so that the reading on the meter matches the pH calibration fluid’s value, 4.0 or 7.0 for example.
Do not throw the used calibration fluid back into the bottle!
Once you’ve calibrated your meter, rinse it with clean water and it will be ready to use. Close the calibration fluid bottle tightly, it will remain accurate for up to 4 weeks after opening. Replace your calibration fluid every 2-3 months. You can purchase both pH meters and calibration fluid here