Reliability of ph testers

Discussion in 'First Time Marijuana Growers' started by intothemystic, Sep 21, 2009.

  1. I'm getting different readings and not sure what to do. Using a 3-way probe tester by Active Air, the readings are low-- one plant at 5.5, the other at 5.8 or so. With a Mosser Lee tablet kit, the ph seems right between the 6.0 and 7.0 colors on the chart.

    I've tested multiple times and get the same results. Should I trust the 3-way and add ph up? Thanks for any help on this.
  2. no, don't trust those pH meters. the stick-in-the-soil pH testers are notoriously inaccurate.

    the only reliable way to test soil pH is to run pH 7 water through the soil until water drains out the bottom, then measure the pH of this runoff water using either a real pH meter or a dye indicator solution. that pH reading will be a great measure of your soil pH. if the pH is below 6, run pH up solutions through the soil until the run off is 6.2-6.8, at which time flush with lots (~3x's the size of the pot) of pH 7 water to rinse out the pH adjusting solutions as well as any salt buildup.
  3. Thanks chiefton8-- your reply came right on time as I was about to head out and look for another tester.

    Any thoughts on the accuracy of those tablet kits where you take a soil sample and mix it up with the tablet and water in a test tube? I went to a fairly reputable nursery and they that said "real" gardeners gave it good reviews. If the water runoff testers are better I'll pick one up-- cheers!

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