Good Soil Ph, Low Ph Fertilizer Solution, High Ph Runoff. How?

Discussion in 'Growing Marijuana Indoors' started by mantriur, Aug 25, 2014.

  1. Has anyone ever had trouble with high (7-7.6) runoff PH when water and soil PH seems fine?
     
    I've switched soil and fertilizer brand at the same time (bad move) and since have had major unspecific problems with all plants in a perpetual grow. The last harvest was a complete disaster. Overfertilization is possible, as I have always fertilized at the upper end (= too much) and if the new fertilizer is stronger, that might have tipped it. On the other hand I've also noticed a very high runoff PH. So now I'm trying to better control all factors I can think of. Unfortunately the PH doesn't like me. :)
     
    Four weeks ago I decided to give all plants a good flush, the ones with old soil were flushed with a mild nutrient solution. PH of the flushing water was 6.3-6.5 and contained a little Cannazym. Runoff has ALWAYS been above PH 7, sometimes up to 7.6. Though when I started checking the PH I realized that the fertilizer is extremely acidic and I must have watered with a very low PH for a few weeks prior.
     
    When I took soil samples from three plants, the two where the samples were from the middle of the soil had a good PH range (6.2-6.4). Another soil sample from the bottom (different plant) read 7.4.
     
    How can the middle soil PH be in a good range with runoff always being way too high? Is it possible that only high PH stuff gets flushed out with the runoff and/or acidic soil/fertilizer contents concentrate more at the bottom of the soil?
     
    The soil is a local mix from peat, perlite, and humus (couldn't get anything else at the time), and the fertilizer is the Bio Canna line.
     

     
  2. How are you testing the soil pH?
     
  3. #3 mantriur, Aug 25, 2014
    Last edited by a moderator: Aug 25, 2014
     
    Mushing soil in a test tube with distilled water and then sticking a PH probe into it. :)
     
    I'm starting to think it's that BioCanna crap. Just did a pre-harvest flush on a plant that had a runoff PH of 7. I've since given it a watering with full strength bloom fert and now the flush runoff was 7.5. We're talking 15L of water through a 15L texpot. First 5L were soft water adjusted with lemon to PH 6.2. When that didn't help, I added another 10L of PHed hard water to get better a better buffer. Runoff was still PH 7.5. This time I tested the soil PH after watering from near the top, and it was also 7.5, too. This makes no sense ...
     
  4. Uhhh...that's not really gonna work.
     
  5. how do your plants look?
     
  6. was just thinking this
     
    if plants are doing well, might just be overthinking it OP, or have a completely different issue. soil ph will fluctuate
     
  7. Yeah that's exactly what I was gonna say next ^.^
    Only check runoff pH if you have a problem or else you'll constantly be chasing your tail
     
  8. plus it's near impossible to get an accurate measurement of soil PH anyway..
     
  9. This is true!
     
  10.  
    Then how does one measure soil PH?
     
     
     
    Not so hot. It got a lot better since I flushed all of them, but it's been four weeks and they are still growing very slowly. The necrosis either stopped spreading or is spreading a lot slower, but they are far from being healthy.
     
    Just to get an idea of how strong the PH buffer in the soil is I added some lemon to the runoff. It took only four ml to get 10 liters down from 7.4 to 6.8, whereas it took about twice as much to get 10L of hard water from 7.3 to 6.3. Yet between the first flush (5l soft water 1ml lemon) and the second the runoff PH didn't change at all. But the EC on the second flush was much higher (after substracting the base EC) - maybe more things got dissolved on the second flush, because the soil was rather dry before. I'm getting the feeling that the real PH is much higher, because the water from the second flush should have been a quite strong buffer.
     
    Last harvest were about 10 grams from a 1.5 meter plant ... it has gotten better since then. Pretty sure overfertilization played a part in it ...
     
    I'm really thinking that the BioCanna is doing weird things. They explicitly tell you that PH doesn't matter with their fertilizer, which is pretty strange to begin with. When mixing a full strength solution with osmosis water, you end up with a PH of almost four. So I've started to use harder water and a lot less fertilizer to end up around 6-6.2, sometimes I use Rizothonic to adjust the PH up. Maybe that low PH in the solution changes somehow once its in the soil and then the high initial water PH backfires?
     
  11. #11 CanadianOrganic, Aug 25, 2014
    Last edited by a moderator: Aug 25, 2014
    Really the only gauge of soil pH you have is the runoff :/
    What is your soil comprised of?
     
  12. As far as I know, the soil is humus, peat, and perlite in even quantities. It's a local mix they sell at the growshop - all professional products are very hard to get here at the moment (I'm in Chile). I scored 3 bags of BioBizz light mix last week, which I hope will help solve the problem, but it's too late for the four plants currently flowering.
     
    I have a small avocado tree, which was planted in the same soil, but never fertilized. I watered it today and checked runoff: PH 7.1 and I used the rock hard (EC 1.0) tap water lowered to PH 6.3 with lots of lemon juice. So it's probably the soil rather than the fertilizer.
     
    What's easy to get and good for lowering soil PH? I have another water option (using bottled water usually with four brands to choose from) with a base PH of 5.5. Would it be a good idea to use that for a while or is that too much? I usually use very purified water with PH 6.8, but it has like zero buffer capacity. You can see the PH dropping when you put a fruit basket next to it. :)
     
  13. This topic has become moot, but thanks for the input everyone! :)
     
    I replaced the soil of all plants (even those in flower) with BioBizz after washing out most of the old soil from their roots. I tried to get the soil PH down aggressively on one plant in a 2.5L container. It took 3 liters of PH 3.5(!) water to get the runoff down to 7. That was the point where I decided that the soil is hopeless.
     
    I wonder what could cause such a strong and high PH buffer. Peat is supposed to lower PH, so either the humus or the perlite must have had some strange properties.
     
  14. #14 waktoo, Aug 27, 2014
    Last edited: Aug 27, 2014
    The soil isn't/wasn't hopeless.  Your grow methodology is.  Why does ANYONE growing in soil attempt to implement hydroponic protocol concerning pH monitoring and adjustment of feed water?  Especially when using soil "runoff" to determine where to start.  What a joke...
     
    pH fluctuation in soil systems is dynamic.  It changes constantly.  Trying to measure and control it is a fools errand...
     
    Farmers don't worry about that shit.  Why should you?
     
    Try this.  Water your plants when they need it, straight from the tap.  Fertilize them sparingly.  See what happens...
     
    Contrary to popular belief, cannabis is not some sort of magical plant that needs "special nutes" or attention.  The cannabis cultivation industry has generated a shit ton of money made from those that have learned how to cultivate plants by reading "grow bibles" and taking the advice presented by same in forums such as this...
     
    You want to learn how to grow good herb?  Start reading horticulture books...
     
  15.  
    I'm not worried about 0.1 points in soil, but when the whole garden has major health issues, especially in a perpetual grow with four different strains and 10 plants all in different stages, it doesn't hurt to check. And if one discovers that the soil PH is above 7.5, one can assume it's at least a significant part of the problem. Yeah, Cannabis survives more or less in any type of soil, but you need a specific PH range (and soil texture) to get good results. I can assure you, you don't get good results in such basic soil. I harvested 10 grams from a plant that should have yielded at least 50. But yeah, it did survive and could have reproduced in the wild.
     
    I did learn however that trying to control soil PH is indeed a fools errand. Nothing I tried could lower the soil PH significantly - at least not with a plant already in it. Since there wasn't much of that soil left, I decided to just buy decent soil instead of experimenting with something I have no real clue about. I dumped it in dead spot in my yard. Maybe the rain can fix it. :)
     
    Farmers probably don't worry about PH much, because they cultivate their fields with tried and tested methods for decades, and don't add some soil mixed by clueless people. Once your method is dialed in, there isn't much need for control. Though there are situations where even farmers have their soil tested and PH is part of that test. When necessary they also add lime to control the soil PH. I'm not familiar enough with the agricultural industry to know how common of an occurrence that is though.
     
     
     
    You're right on fertilizing sparingly - I went overboard with that, but it was never a problem in the other soil mixes I used before, so I'm fairly certain it wasn't the one major contributing factor to my problem. I'm not using tap water anymore, because it's rock hard here (EC of 1, sometimes more), full of chlorine, and smells like industrial waste. Second world problems. :)
     
    Every plant needs "special" nutes, as the amount and mix of minerals they need differs. That's not a problem in an open system, like when growing outdoors, but in containers it can be if the balance is too far off, as unused salts will accumulate. What's wrong with using Cannabis specific nutes? Tomato nutes would probably work almost as well, but why complicate things? (I'm not talking about all the strange snake oils out there, though some of them have their uses.)
     
    I don't read grow bibles. :) I get my information from the internet, yes, but usually by comparing different sources on the same topic and then trying to pick the correct answer using common sense. I rarely actually ask things on forums, because most have been answered plenty of times before. It works quite well most of the time, except for some niche voodoo methods, where everyone has an opinion and very few people real knowledge. In that case I try to find some scientific publications on the topic, which are a pain in the ass to decipher. :)
     
    The specific problem that prompted me to post here simply did not make any sense to me and it still doesn't, but it's a moot point now.
     
  16. Seems like your last post answered your question.

    Dolomite lime.

    Probably the peat moss mucking things up. As long as youre not using bottled nutes you should be ok. But if you are.....maybe you shouldnt be.
     
  17.  
    I did consider that, but from what I read it's more suitable to raise PH than to lower it. I think it buffers towards a PH of 7, which is already better than 7.5, but since I'm generally clueless about soil biology and didn't have that much left, I figured it's better to use a proper soil prepared by people who know what they are doing.
     
    I want to start experimenting with reusing soil. I'll hopefully learn some details on the way with that. :)
     
     
     
    Unfortunately I am. I'm only growing for about two years and since I never had any issues with soil or the nutes before, I've mostly obsessed over light (I use LEDs), temperature, humidity ... the kind of stuff a person lacking the green thumb can easily control. :)
     
    My biggest issue with preparing my own nutrients or soil is the language barrier and availability. I'm a native German speaker and most English terms are too specialized for me to have come across them before. Then I live in Chile and my Spanish still sucks, which makes it very hard to find things that are not sold in the garden center or grow shop. I'll go there when I run out of other aspects to improve. :)
     
  18. I was born and raised in California. Studied english in college. Your english seems better than mine :)

    For what it's worth.
     
  19. @[member="mantriur"]
     
    Why not spend some time doing some reading over in the organics forum?  Soil mixing, soil biology/chemistry, natural pest control... all sorts of interesting information that would allow you to grow without the need for bottled chemical nutrients is there.  There are a lot of smart people there who understand it all, too, with plenty of references provided by/contained within scientific books and publications.
     
    Lots of folks here in the 'States have issue with "availability" and effectively sourcing natural materials for building soils.  And they speak ENGLISH!  So do the people that they're trying to communicate with that have no idea what "neem meal" or "rock dust" is...  ;)
     
    Where there's a will, there's a way.  Natural products for building soil are available all around the world.  You just have to know what to look for where you live, and then you need to know where the best places are to source those products.  Get set up properly for your next grow.  The organics crew can help you figure it out, if you have the will...
     
    My post in response to yours was a bit "ass-holeish".  My apologies...  :unsure:
     

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