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Raising soil pH

Discussion in 'Plant Problems: Pests, Disease & Deficiencies' started by Rabiez, Sep 5, 2006.

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  1. #1 Rabiez, Sep 5, 2006
    Hi everyone,

    First time poster, long time reader, but on this occasion unable to search out the answers I require. Hope the usual suspects will come to my aid. Loving the city btw.

    I'm experiencing a slight problem with low soil pH.

    Water run off measures about pH 5.5

    I have always pH balanced water and nutes to 6.5 before feeding.

    I have flushed several times with tap water that has been stood for 24hrs and measures pH 7.5, but it seems to make little or no difference to the run off measurement.

    How many flushes should I be looking at to raise the pH 1pt?
    Will too much flushing cause any problems?
    Should I pH+ the water a little higher? If so, how high?

    Any other suggestions? Don't be shy, I can handle constructive critisism, and would appreciate any help offered.

    Hit me with it.

    --
    FYI:
    Pots are roughly 12" tall x 10" diameter, approx. 2-3 of your US gallons I guess
    Leaf curl presented about 4 days ago, and worsening regardless of epsom salt foliar feeding.
    It's a peat based potting compost, which according to my research does promote acidity.
    I'm considering re-potting into plain topsoil/verm/perlite, but would rather treat the problem as it stands if possible.
    I've tried adding a bit of lime to the soil, but all info points to this taking some time to work its magic.
    Please ask if you need more info.
     
  2. #2 froggy, Sep 5, 2006
    dolomite lime will do the trick.
     
  3. #3 Lucian, Sep 5, 2006
    Flushing won't raise pH, well it might but it would take well, forever. I had the same problem using Promix which has a pH of 5.5. You should can try buying a small bag of dolomite lime and figure out how much you could spread on top for how much soil you have in your pot. Unfortunately, lime usually takes a few weeks to raise pH. The problem, I think, maybe too much peat in your soil mix which lowers pH. Like I said, I used untreated promix my first grow and it was ok. For my second grow, I bought a storage bin to hold my dirt, dumped it in and mixed in lime, wetted it down and let it sit for a few weeks before use. Eventually, I moved on to Sunshine mix #4 and then foxfarm dirt.

    I am not sure what you can do about it mid grow. I suggest using the lime as a top dressing as it seems to be suggested alot for this but I am unsure if it works. I would think it would make the soil on the top skyrocket in pH while the soil on the bottom of the pot remains untouched. Hmmm.

    Ahhh I just read your footnote and see you know about lime. Well, to be better safe than sorry, if they are young enough to not have alot of roots, you could transplant but once the root ball gets too big, there is no way to get all the bad soil out so your stuck. I wouldn't panic though if you leave them. They will still grow but you'll just have to keep an eye on other problems that may pop up.

    If th leaves are curling down and getting droopy, that could be from overwatering as well as low pH. If the edges are curling up, then epsom salt like you tried and remist 2 days later and then you should see recovery.

    Hope this babble helps some.
     
  4. #4 Rabiez, Sep 5, 2006
    This is my take on it also.

    Age is unknown, both plants came to me 8" tall, with 2 nodes and no new growth. They are now approx. 12" tall (after some judicious topping), with plenty of bushy new growth. I think clearing the dirt from the roots is unfeasible. They were only transplanted about a week ago, so I guess I can at least give them around 2-3" of new topsoil around the outside of the root ball.

    Ahh, that's useful, ta. I was expecting some kind of instant/overnight recovery, which didn't happen. I shall be patient.

    I welcome all opinions, and thankyou.

    I'd enjoy some more input if anyone else feels like it. Dier? VteC? Anyone?
     
  5. #5 Num, Sep 5, 2006
    re-calibrate ur ph meter before u go adding any alkali ;)
    baking soda (sodium bicarbonate) is pretty harmless as ph up.
     
  6. #6 Rabiez, Sep 5, 2006
    Wise words indeed. I shall.
     
  7. #7 Rabiez, Sep 7, 2006
    And i did. pH meter was spot on.

    I flushed again last night. The run-off is getting clearer (less brown), and pH is now hovering just below 6.

    Leaf curling isn't getting any worse. :)

    LST is now underway.

    As an aside, whilst fannying about in the growroom this morning, I noticed a badge on the side of the potting compost declaring "Now with time released nutrients". Well, naturally after reading all the bad news about time release, I had this horrible sinking feeling come over me.

    Fortunately, on further investigation, it turns out that the ferts were in a seperate 240g sachet inside the bag. Whew!

    So, everything's cool, plants look good, I'll be harvesting my tomatoes by christmas.

    FOR SALE: One 240g sachet of time released nutrients - Mess up your grow like an MG pro!
     
  8. #8 dannyg, Sep 7, 2006
    dolomite lime is your friend. it helps stabilize pH levels. when i had mg deficiency i mixed a bunch of dolomite lime in with my soil and watered it. helped out a bit.
     
  9. #9 SmknVTEC, Sep 8, 2006

    Ha
    Very funny.
    I like that.
     
  10. #10 Rabiez, Sep 8, 2006
    Danny, thanks.

    I've added lime, but it takes time, to make the soil less acid,
    I couldn't wait, until that late, my plants were getting flaccid.

    ^^Sorry about that, can't resist a rhyme. :D



    Heh, I've read a lot of your stuff, and had a feeling that might draw you in if you were reading. ;)
     
  11. #11 froggy, Sep 8, 2006
    one can add dolomite lime to water. roughly 1 teaspoon per quart of water.

    this can be a quick pH up if u need it.
     
  12. #12 Rabiez, Sep 8, 2006
    See, now I thought about that on Weds night, and couldn't decide if it would be any faster than mixing the lime with the soil.

    So, pH meter, cups, and lime in hand, off I trotted to the bathroom to check.
    I mixed varying quantities of lime & pH tested water in different cups, and kept coming back to check pH evry half hour or so.

    Results: No change in pH in any of the cups.

    I decided to help things along by sticking a new head on my electric toothbrush, and sticking it in the cup with most lime in to work as an agitator.

    Left it for 24 hours, and there's still no change in pH, so I conclude lime ain't the answer for a quick fix.

    I've read conflicting opinions on soil pH. Some say that it relates directly to the soil, others say it is simply the pH of the moisture contained in the soil. If it's the latter, then I'd have thought that a few flushes with water pH balanced just above my desired level would sort it.

    Anyway, it's getting there...slowly. Thanks for your help.
     
  13. #13 froggy, Sep 8, 2006
    i dont get it. u put lime into water and checked the pH and it didnt move??

    well, maybe that wouldnt show up because there is nothing for the lime to ion transfer. i dont know about ur experement but they have been using lime to move soil pH for many years. i have to put down about 5-7lbs of lime per 100sqft or not much grows. and i know that i can cure any nut lock on the low pH side by adding lime water to the watering scheduel.

    also, hydrated lime works instantly. if i were going to raise the pH instantly, that is the lime i would use. but that is some hot stuff so be careful.

    but i think the real issue is ur soil. maybe ur soil is soooooo pH low that it doesnt matter how much lime u put in...its gonna take a while. maybe u should explain what ur soil mix is?

    hi amounts of fert. and hi amounts of peat will both give u low pH. is this where ur problem is?
     
  14. #14 Rabiez, Sep 8, 2006
    Indeed, not even after leaving it 24 hours.

    I don't know about the chemistry of it in fairness, but my old mum's an avid gardener, and she agrees that lime is the way to combat acidic soil, but will take time.

    Aww crap, I hope I haven't gone and bought 'time released' lime by mistake. ;)

    All the info I've read suggests a minimum of 3 weeks for lime to do its thing, so I'm doing my best to control it with high pH flushes in the meantime. It seems to be doing the trick at the moment.

    Soil is a peat based potting compost + roughly 20% perlite, and 20% vermiculite. It could possible be described as 'a little loose'. As previously stated, I'm aware of the peat encouraging acidity, but don't think I'll be able to remove it all from the roots without causing more problems than I solve.

    I've used Canna Terra Vega (great for tomatoes I'm told) for 1 feed @ 25% of the recommended strength, and 1 feed @ 50% recommended, both times pH upped a little high to try to combat the soil pH. Bearing in mind that the low soil pH was noted before any ferts were in play, I think we can safely say they're not the problem.

    My OP was because I didn't see any difference in run-off pH after flushing, but I think I was a bit shy with the volume of water I flushed through it, not wanting to drown the plants. Last flush I put maybe 5 times the volume of water through, and saw better results
    I reckon another flush on Sunday should see run-off up to pH6.2 (maybe a touch more if I'm feeling a bit brave with the pHup).

    We'll see on Sunday I guess.
     
  15. #15 chimera, Sep 8, 2006
    ya want ta raise your ph in a hurry just get some ashes from a wood stove(about a cup) mix with hot water and let stand over night.
     
  16. #16 froggy, Sep 9, 2006
    peat is more than a 'little bit pH low'.

    and fert is almost always pH lowering also.

    and u should flush with 2x the amount of pot u have. if u have a 3 gal pot, u should flush with 6gal. if u have a 10gal pot, u need to flush with 20gal, etc...

    there is no 'slow release lime'. there is dolomite lime and calcium lime. and they can hydrate either so that it is in a quicker water reacting formula, that is what hydrated lime is. but its extremely hot stuff.

    yea wood ash will help also but that can carry in some bad stuff also. i wouldnt put more than a teaspoon per gal into the soil. like everything, a little bit is good, alot is bad.
     
  17. #17 Rabiez, Sep 9, 2006
    Heh.

    'A little loose' - not packed tight into the pot.

    Weird innit? It's like someone made it up as part of some poorly executed attempt at humour. ;)

    [c]*Scribbles notes in pHup recipe book*[/c]

    Useful, ta!
     
  18. #18 Rabiez, Sep 11, 2006
    With a little messing about, last nights flush brought run-off up to pH 6.5

    Job's a good'un. Thanks for the help.
     
  19. #19 froggy, Sep 11, 2006
    whilst this grow is going on, i think u need to figure out a system that isnt so outta pH range.

    maybe ur water?
    maybe ur food?
    maybe ur soil?
    maybe ur...?

    i think u need to isolate each input. then we can figure out what is going on. but the real story is that u have went thru the process and done ur homework. next time will be easier, i promise.
     
  20. #20 Rabiez, Sep 11, 2006
    I'm pretty sure it's down to the soil.

    I balanced a bit of water last night, and ran it through a pot of 'straight out of the bag' soil.

    pH 4.8 for the run-off. Nuff said? I think so.

    Thanks for the encouragement. I see lots of pasta sauce in my future.
     
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