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Soiless pH problems

Discussion in 'Indoor Growing' started by bbtwos, Nov 12, 2017.

  1.  
    bbtwos

    bbtwos Member

    Hi, using Pro-mix soiless medium, A/N at 3/4 strength, (which tests out at 5.7/5.8 pH before watering) but my medium run-off is always 6.5 range?? Soil probe says it's even higher, but it's a cheap probe (have ordered a better one)
    I tested various pH level (non-nute, R/O) water through my raw medium, and whatever goes in, seems to come out basically the same. Doesn't seem like the Promix is causing the increases....???
    I flushed 5x the pot volume through these plants, with plain pH 5.0 water (testing after each flush) and I can NOT get run-off lower than 6.5?? Calibrated metre often, tested against known samples, I think my #'S are accurate. Flushing brought my tds/EC down to nothing.....but pH didn't change much. WTF?? What could cause soiless pH to resist change like this? TDS ppm came down to 40 (pH balanced R/O water), but pH remained bullet proof. Brought last run-off sample home, did a fresh pH calibration & 24 hr. later, sample still reads 6.4
    I know I am having nutrient lock-out issues, and think this pH is causing my grief.
    Any thoughts appreciated.
     
  2.  
    Gquebed

    Gquebed Well-Known Member

    Youre using Promix....which is just peat moss with perlite, i believe?

    I use promix mycrohazea (sp?) And AN nutes. I just make sure my ph is around 6.2 to 6.5 going in. Never worried about ph on run off... never had a problem.

    Id bet your problems have more to with either over watering or salt build up.
     
  3.  
    bbtwos

    bbtwos Member

    pots
    I use the mycorrhizae as well, and I flushed the soil over & over until the run-off EC was coming out below 100 ppm, but the pH just refused to get lower, poured 5.0 in, 6.5 came out......over and over and over again. After that many flushes, how can the pH not drop?
     
  4.  
    70's natureboy

    70's natureboy Well-Known Member

    Pro Mix is usually more acidic. I never saw a PH meter i could trust. I 'd say your nutes have a high PH or too much PH buffers for Pro Mix or your PH meter is screwy. Since i don't trust meters i would have to test it the old fashioned way to believe the ph was really staying high. I used to add lime to my Pro Mix just to keep it neutral.
     
  5.  
    bbtwos

    bbtwos Member

    Thanks for the response, but I checked the plants in veg room, and the metre is working fine. Run-off water tested fine. I'm one of 1000's of people using Promix & Advanced Nutrients so I gotta believe it's not the nutrients. And as I said, I flushed with LOTS of plain R/O water, pH adjusted to 5.0 I was then going to change & flush with 5.5 once I got it down around 6.0. Gallon after gallon and it stayed at 6.5. I repeatedly tested & recalibrated tester. I then tried both my test strips & titrate tester for hot tub, same results. 6.5.....I'm looking for answers that explain why plain 10 ppm water, at 5.0, won't lower the soiless mix pH?
     
  6.  
    bbtwos

    bbtwos Member

    And I have tested run-off from new Promix just in a pot with no plant to see what comes out at 1st, then after a 2nd watering etc. It behaves as stated, this is just weird??
     
  7.  
    Gquebed

    Gquebed Well-Known Member

    Dont know what to tell you other than i never cared about outgoing ph as long as the plants are healthy and neither should you. The fact is 6.5 is great ph for promix.

    I think youre chasing a ghost with all the flushing and thats caused over watering problems. You likely suffocated the roots at some point and they couldnt uptake any nutes so they started canabalizing themselves, turning spotted and crispy.

    They do the same if you don't get them enough fresh air. I can show you some really sad pictures of burnt up plants because I chased a pH problem when really all I needed was fresh air.

    Everybody here is so focused on ph but the truth is it really doesn't matter that much as long as you're in a decent range. It's not that the plants can't up take nutes they just do so better at specific pH points

    Weve all done it... chase the wrong problem and makes it worse. Thats the pain that is learning...
     
    arcalion and bbtwos like this.
  8.  
    bbtwos

    bbtwos Member

    Thanks, will try to relax a little. Plants aren't dying, but definitely not healthy.....frustrating. They've survived a lot of shock getting moved around and living in less than ideal spaces for awhile. (Long, boring story).
    Will see how things react next few days, tried a few different feeding levels after flushing so will hopefully learn some stuff this week. Thanks again for the response
     
  9.  
    arcalion

    arcalion Active Member

    Pics?
     
  10.  
    bbtwos

    bbtwos Member

    IMG_2083.JPG
    Oh, and forgot my main response....haven't done any massive flushes other than this one.......
    We always wait until fairly dry, then water to drain, give them regular 0 ppm r/o doses to help keep salts down, every couple feedings. I am just going to worry about the ongoing pH though...
    this is new growth coming up the middle of a plant that has been 'trained' outward.
     
  11.  
    bbtwos

    bbtwos Member

  12.  
    arcalion

    arcalion Active Member

    Sure they'e not just overfed? Im with promix and I've never had problems with PH of 6.5; I've had huge problems when it was 5.0-5.5 though
     
    Gquebed and bbtwos like this.
  13.  
    bbtwos

    bbtwos Member

    1st one looks a bit like a deficiency and 2nd in definitely nite burn, tip burn, clawing from too much N.....ppm were high, the flush may stabilize this?? Hope
     
  14.  
    bbtwos

    bbtwos Member

    That is what is confusing....some leafs look deficient & some look over fed??
     
  15.  
    Gquebed

    Gquebed Well-Known Member

    Hate to say it but this is classic, exemplary damage from overwatering. Ive been there and done that.

    The grey/blue in the leaves are signs of phosphorous deficiency (which leads to the yellowing on the edges), the curling tips, the wrinkled leaves... all of it... from over watering. I just went through all of this on my last run (trying to dial in a watering regimen for led cobs).

    Anyway...who told you that your ph should be down to 5.5? Thats even too low for true hydro. Everybody growing in promix knows 6.5 is the sweet spot for veg and 6.2-3 ish for bloom.

    So you cam keep chasing the ph problem that you dont have or...you can just transplant these into bigger pots and save them.
     
    bbtwos and arcalion like this.
  16.  
    bbtwos

    bbtwos Member

    I will let pH come up, but the pots are almost too big. I don't water until the plants feel very light, so not sure how I can be overwatering? I water a couple litres in each, let it soak in well for 5 minutes, then go back & then add more until I get decent run-off. The plants are on kitchen cooling racks, on a sloped water-proof table, with an effective drain. They NEVER sit in any amount of water, and are free to drain. Is this not the proper way to water? Wait till light, dry down a couple knuckles deep, then water 10-20% to drain.
    Still confused. Sorry.
     

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