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ph Drift is GOOD!

Discussion in 'Advanced Strategies and Fertilization' started by br1dge, Jan 31, 2006.

  1. br1dge

    br1dge Junior Poster

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    Years ago, I did some "consulting" to a friend who was setting up a large scale tomato growing operation. He wanted to grow organic produce hydroponically. One of the things that we implemented was a ph drift strategy, being that hydroponically, plants uptake different nutrients at varying degrees of readiness based on ph of water. ph of 5.5 to 6.5 was found to be the best range, and intentionally forcing a drift allowed for maximum exposure. There is a corresponding chart for "dirt" grown veggies, but I will leave that out to keep us focused. Pls note, I did not create this chart, and linking to its source may be considered "questionable," considering the context of that source, so I will post as is.

    I dont claim to be a scientist, in fact far from it, but this "Strategy" has been used effectively by hydroponic growers for a long time with tremendous success. Never see this discussed here, except for the occasional mention that plants seem to do better (reds more red, etc) at very low PH levels. Could this be why?

    [​IMG]
     
  2. wapfish

    wapfish Prolific Poster

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    Re: ph Drift is GOOD!

    Hey, that's really interesting.

    I recently started cutting my hard water by 1/3 with DI water and now, with reduced buffering, I'm getting a much higher pH swing overnight (.4 unit) with CO2 on 24/7. I was thinking about getting a solenoid, just to save on CO2 and reduce the swing, but I'll have to take this line of thinking into consideration.

    You say this strategy's been used with "tremendous success". Rigorously, this would mean that plant growth has been examined with the only difference in growth conditions being a pH swing. Do you know that to be true?

    Nice post!
     
  3. Tom Barr

    Tom Barr Founder
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    Re: ph Drift is GOOD!

    The .4 pH unit difference is due to the plant uptake.
    I use CO2 only during the day.

    Note: CO2 induced ph drops are different than pH induced drops for tomatos.
    I'm pretty sure they do not use that.

    Tomatos also do not take up CO2 in an aqueous solution, they are emergent plants.

    Alkalinity likely plays a role more than pH to a large degree. And mainly due to CO2. Some plants do better at different pH's than others.

    Most all plants/organisms for that matter have optimal pH's, temp's, nutrient concentrations.

    There are trade offs for each nutrient since they are all not available equally, but even so..........plants are not passive in their uptake/availability of nutrients.

    If that where the case, then the pH would matter a lot more.
    It can help in some cases, namely with the type of trace mix and PO4 dosing routine you do.

    Recall, FePO4 forms in acidic conditions and preciptates out.
    The white milky stuff you see Flourish react with in Harder Water is Ca base preciptate, but you do not see the acidic the preciptate as easily.

    I use TMG as it's optimal pH for the chelator is better suited for our pH's and stronger(DTPH). I'm not sure but most other trace mixes use ETDA for the other trace metals like Mn, Cu, Zn, rather than gluconate or other chelators/complexes for Fe.

    The chelators have pH optima also.
    The above chart does not include chelators................so we can get around some of these issues that way.

    Regards,
    Tom Barr
     
  4. br1dge

    br1dge Junior Poster

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    Re: ph Drift is GOOD!

    Wapfish - I do not have any double blind studies I can quote, only speak from personal experience and observation. After switching to a drifting approach, I did see a substantial increase in plant growth, but part of that was also due to having a lower (average) ph than before (not just the drift.) With this ph drifting approach and CO2 injection (in the air) we saw growth rates that were staggering. You could literally see these things grow in front of your eyes. I recall one case where we had a plant (obviousy dialed right in) that grew 3 - 4 inches in just one day.

    What I wasnt sure of (still am not) is how if at all, hydroponic factors play into aquatic plant growth. After all, plants grown hydroponically still feed
    through their roots and use CO2 from the air.

    Still -we had a lot of fun, but just couldnt make any money at it; but it sure was sweet to be gnawing on a fresh, juicy better boy tomato with 4 inches of snow on the ground.
     
  5. br1dge

    br1dge Junior Poster

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    Re: ph Drift is GOOD!

    Tom - so my question to you is, do you agree that for any given plant, there is a range where certain nutrients are taken up at a greater rate than others? And to that extent, would you further agree that by forcing a ph drift, we could provide an environment conducive to greater nutrient uptake, better growth, etc? Or are the benefits not worth the effort to figure it all out? Thanks in advance for your thoughts
     
  6. wapfish

    wapfish Prolific Poster

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    Re: ph Drift is GOOD!

    Just to be clear, you were injecting CO2 by air before and after switching to the pH drift conditions, right? None of the benefit is attributable to using CO2 in one case, but not the other (which would certainly be expected)?

    Also, how did you drop the average pH?

    Sorry for the questions, but sometimes the devil's in the details :) .
     
  7. wapfish

    wapfish Prolific Poster

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    Re: ph Drift is GOOD!

    Righto. That's what I was assuming. With my KH previously at 17, I used to get very little pH change night to morning (pH6.8 day target, little change at night). Now, with a KH of 5-6, I'm getting a .4 unit range (6.4 night -> 6.8 day) with essentially the same plants, lighting, etc.

    This is just due to lowered carbonate buffering in my current situation, right? No harm except CO2 wastage and fish effects. From what I've read, this amount of fluctuation shouldn't bother fish much at all (?). Certainly they don't seem stressed in any way.
     
  8. Tom Barr

    Tom Barr Founder
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    Re: ph Drift is GOOD!

    Sure, nothing wrong with trying it, but I've been doing this for decades already. But.......folks that add CO2 24/7 has less drift, yet report good similar growth rates etc.

    I do not add CO2 at night, never liked the idea for fish safety issues. But the pH drift occurs there about 1 pH unit.

    That's about all we can hope to get out of this, not sure if this helps the plant growth rate though/nutrient uptake.

    You could argue it does, but showing it is quite another matter.
    I do not think it is something particularly significant in our case.

    Folks have long said there's little difference between 24/7 CO2 and day time CO2 only, but ADA and myself have independently suggested not to add CO2 at night.

    This might be a planted reason why, but I doubt it really means that much in terms of vegetative growth, fruit and/or specific crop production is another matter.

    CO2 dosing vs the pH's affect are often hard to tease apart, who did what and why.

    We all know adding CO2 dramatically increases crop and aquatic plant production, ph? Seems to be less so.


    Regards,
    Tom Barr
     
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