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Thread: Some thoughts/questions on runoff pH & EC

  1. #1

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    Default Some thoughts/questions on runoff pH & EC

    I know some could care less about runoff and get along just peachy. Id like to get there, too. I'm not too interested in chasing runoff, but maybe better understanding what the numbers can mean when symptoms lead me to check, I guess.

    Some junk in my head:

    For whatever input EC, the runoff could be say ~0.2 higher and the plants could still be feeding just fine. In this case I'd assume the ec rise being due to the salts concentrating as coco lost moisture between feeds. Increased water volume and/or frequency could combat this if even necessary. Yeah?

    Suppose the EC is rising to x due to salt build from lack of runoff or the plants just not feeding. Outright flushing aside, continued watering at x-y should bring the EC runoff down to x-y. Right? I think I've verified this for myself recently, just checking that I haven't completely lost the plot.

    If feeding coco daily with 6.0 pH'd feed wouldn't each feed reset the pH as it does the EC? I have a few plants that are consistently
    giving back 5.3-5.6 pH runoff when I've been giving them loads of 5.9-6.0 pH'd feed, +40% runoff, every 18 hours. I get that runoff isn't a perfect measurement, but is pH more susceptible to inaccuracy than EC in runoff readings?

    Appreciate any thoughts/corrections. Thanks.
    ~It's a violent universe~

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    I came across a hempy bucket grow where the guy got obsessed with the runoff pH. He kept trying to get the runoff to come out at pH 6.2. (Why?) Towards the end, he was putting in pH 4.5. wtf??? All buggered before mid flower.

    Sort of related, there's a dwc theory/strategy that when the level in the res drops, the ec should stay the same. If the ec rises, then the plants have been taking more water than nutes. Lower the ec. A lower ec means the plants are taking more nutes than water, raise the ec. My last dwc was done in a damp cellar and they hardly drank anything. I wasn't really on top of any measurements back then but I'd guess that there's a relationship between strength of lighting, ec and humidity.

    A problem with measuring runoff is being consistent. Pour in an extra litre of feed than usual and the runoff measurements will change. Keep the volume going in the same and the growing plant messes that up a bit too.

    It's possible that the pH can be reset too often and doesn't swing enough. With my Pepsi grow, I was using GH FloraNova Grow at 1.5ml/L. I was feeding every 8 hours because it seemed like a good idea at the time. Didn't take long before the leaves looked like a speckled hen. I started 2 freebies for a test, 1 at 1ml/L and 1 at 2ml/L. One feed a day only. Results weren't perfect but no speckled hen leaves.

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  5. #3

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    Quote Originally Posted by Farmer Geddon View Post
    I came across a hempy bucket grow where the guy got obsessed with the runoff pH. He kept trying to get the runoff to come out at pH 6.2. (Why?) Towards the end, he was putting in pH 4.5. wtf??? All buggered before mid flower.

    I can imagine. Lol
    I wouldn't want to get that anal about it, but I've been tempted to pH up to 6.2 on the seemingly low pH coco in question.


    Sort of related, there's a dwc theory/strategy that when the level in the res drops, the ec should stay the same. If the ec rises, then the plants have been taking more water than nutes. Lower the ec. A lower ec means the plants are taking more nutes than water, raise the ec. My last dwc was done in a damp cellar and they hardly drank anything. I wasn't really on top of any measurements back then but I'd guess that there's a relationship between strength of lighting, ec and humidity.

    Yeah, so many variables to consider, like humidity affecting transpiration, or the plants just not being particularly hungry on a given day.

    A problem with measuring runoff is being consistent. Pour in an extra litre of feed than usual and the runoff measurements will change. Keep the volume going in the same and the growing plant messes that up a bit too.

    I've tested the runoff like that as well; a few readings spread out in the same feed. As I recall the EC has always been consistently within 0.1 EC (in either direction), whereas pH can at least drop substantially, like 0.4-0.5, between a couple readings. That's all I've noticed for myself anyway.

    I guess it makes sense that the sum of the runoff could be made up of varied hot spots, peaks and troughs across the exchange sites and whatnot, not always giving an accurate picture of the coco's state overall. It just seems like given enough water it should, and I'm left scratching my head when I read diaries where the runoff seems to always make sense.

    I wonder if pot size plays a big factor? Just guessing that maybe underdeveloped roots in a 15L or so could cause unexpected, but ultimately explainable, runoff readings. I'd think so in terms of ec, but pH is still more of a mystery to me.


    It's possible that the pH can be reset too often and doesn't swing enough. With my Pepsi grow, I was using GH FloraNova Grow at 1.5ml/L. I was feeding every 8 hours because it seemed like a good idea at the time. Didn't take long before the leaves looked like a speckled hen. I started 2 freebies for a test, 1 at 1ml/L and 1 at 2ml/L. One feed a day only. Results weren't perfect but no speckled hen leaves.

    Hadnt thought of pH resets effecting swing. Sorta flies in the face of what I'm reading about the benefits of frequent fertigation and keeping the coco moist. I think...

    Maddening hobby...


    . . . .
    Last edited by Sir Digby Chicken Caesar; 01-07-21 at 02:17 AM. Reason: Oof...messed up the quote thingies..

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    If the EC is above the EC of the feed, you are over feeding

    Measuring the run off is a good indicator of things but don't rely on it as a totally accurate measurement. It is good to watch trends though
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    with coco, i like to feed low and feed often to not allow much room for drift in ph.

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    With Mz Pepsi getting a bad attack of speckled hen when fed 3 times a day, I'd guess that the starting pH was close to one end of the pH limits and couldn't swing enough the other way to allow the uptake of some minerals. That's twice in the last 12 months that I've fed more than once a day and duff results each time. The first time, last year, I killed a plant through overwatering. Hmmm vermiculite...

    It's like that board game Mastermind. The skill is in knowing what questions to ask. Ask too many questions at once and the answers will have zero validity.

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    as a general rule, when plants are young and im feeding once every 2 days, i feed at 5.5 knowing it will drift close to 6.2.

    when i start feeding daily or twice daily, i feed at 5.8 which is pretty much in the middle of the range. this way it wont drift much at all.

    bear in mind, it will drift down for some people so one would have to start at the higher end.

    when i use to check runoff, it done more harm than good. figured staying in the middle of the range was better and feeding twice daily helps do that.
    Last edited by Krofam; 01-07-21 at 11:52 AM.

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    Quote Originally Posted by Sir Digby Chicken Caesar View Post
    I know some could care less about runoff and get along just peachy. Id like to get there, too. I'm not too interested in chasing runoff, but maybe better understanding what the numbers can mean when symptoms lead me to check, I guess.

    Some junk in my head:

    For whatever input EC, the runoff could be say ~0.2 higher and the plants could still be feeding just fine. In this case I'd assume the ec rise being due to the salts concentrating as coco lost moisture between feeds. Increased water volume and/or frequency could combat this if even necessary. Yeah?

    Suppose the EC is rising to x due to salt build from lack of runoff or the plants just not feeding. Outright flushing aside, continued watering at x-y should bring the EC runoff down to x-y. Right? I think I've verified this for myself recently, just checking that I haven't completely lost the plot.

    If feeding coco daily with 6.0 pH'd feed wouldn't each feed reset the pH as it does the EC? I have a few plants that are consistently
    giving back 5.3-5.6 pH runoff when I've been giving them loads of 5.9-6.0 pH'd feed, +40% runoff, every 18 hours. I get that runoff isn't a perfect measurement, but is pH more susceptible to inaccuracy than EC in runoff readings?

    Appreciate any thoughts/corrections. Thanks.
    My run off would be impossible to check, mine get bottom fed every 3 days ish currently, last 2 grows done this way and not had a problem yet, Not everyone’s ideal method but works a lot better than checking the Ph Ec and run off etc etc, for me anyways

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