soil ph vs run-off water ph

Discussion in 'First Time Marijuana Growers' started by bizybily, Nov 24, 2011.

  1. I recent started testing my run off water ph and the soil ph after watering. Can someone tell me why my run off water ph can be as low as 4.2 and my soil ph 6.5? Which do I go by?
  2. you go by runoff. what is the pH of the water your putting in it?
  3. The water going in with or without ferts is 6.4 to 6.7.
  4. its strange that your getting such a low runoff, not exactly sure what would do that. I wouldnt worry about it to tell you the truth. If as long as the water your putting in it is correct, you should be fine.
  5. Thanx MaineCronic. I think your right because the plants look very healthy. I just realy do not understand why the two test are so far apart.
  6. How are you testing? When's the last time you calibrated your meter?
  7. ive had this same same poblem since day 1 biz, ive tried everything higher water, dolomite lie etc. nothing works but my plants look god as well so I wouldnt worry
  8. My soil meter is new and calibrated at the factory to 7.0. I have two water meters that I calibrate at least every week. Everytime I water/feed I bring the solution to 6.4 - 6.8 and water. I then test the run off and soil.
  9. first its important to know wht fertilizer you are using - organic or non-organic, if its organic and I mean 100% organic not many "bottled" fertilizer is but the general organics brand from general hydroponics is or claims to be and does a pretty good job at convincing people but it works like organic so this works for that

    organic fertilizer you pretty much dont have to worry about the ph at all, if its done correctly with microbial stuff in the soil it will adjust the ph to the correct levels and it can sometimes be low

    if you are using non-organic or chemical fertilizer like Ionic, General Hydroponics, Advanced Nutrients, and others, even FoxFarm isnt 100% organic and you ahve to adjust the ph - with these types of fertilizers you could have a problem if your run off is that low

    the soil meters can be way different depending where you put it into the soil to read it - the run off water reading is the best to use

    if you are getting run off that low you can take lots of water at 6.0-6.5 ph at least double or triple the amount of the pot size, so if you have a 5gal pot do at least 10 or even 15-20 gal of 6.0-6.5 water through it and it will flush everything out of it, just run water through it until you get a reading of 6.0-6.5 ph - even if there is no problem doing this wont really harm the plant you will just have to wait a while for it to dry out all the wait and put more nutes into it, in some cases you could cause the soil to go to a low ph state from a large flush but this can be fixed with higher ph water

    its sorta over watering to do this but if you let it completely dry out then it should be ok, it is all the times I have done this
  10. #10 Abtima, Nov 27, 2011
    Last edited by a moderator: Nov 29, 2011

    I'm having the same issue and I started a new thread to really nail down how to accurately measure soil pH. Given the tests I have done I'm not sure that using runoff to approximate soil pH is very accurate. You can check out the discussion here if you're interested, paying special attention to my posting at 8:24 am on 11-27-11 and the test results:

    The Final Word on How to Measure Soil pH. Method 1 or Method 2? - Forums

    The runoff readings I've been getting (sort of similar to your's) strike me as too wonky to be an accurate measure of soil pH. Like you, things look great but the runoff pH is measuring too low. That and the tests I did lead me to believe runoff isn't really a good measure of soil pH.

    If I were you I'd get some 7.0 pH distilled water, make a slurry with the water and 2-3 tablespoons of your medium taken from the root zone, let it sit for 30 mins to an hour and get a pH reading from the soil slurry. I'd then calibrate and use your soil tester to measure your soil pH and compare the two results. My guess is the slurry pH reading will be pretty close to your soil pen's pH reading. And I bet that if you pH'd your runoff you'd still get some wonky low pH number. I think the first two tests are more accurate measurements of your actual soil pH.

    I'd like to hear what the results are. Good luck!

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