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How to lower PH in clay soil?

Discussion in 'Homeowner Assistance Forum' started by mlong30, Oct 20, 2007.

  1. mlong30

    mlong30 LawnSite Member
    Messages: 111

    Hi All,

    How can I lower the pH in clay soil from 8.0 to 7.0-6.5?


  2. bug-guy

    bug-guy LawnSite Bronze Member
    Messages: 1,029

    down here in fl we use sulfur to lower the ph check with your local county extension or a lesco in the area
  3. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I live in Virginia and we have a good deal of clay soils, I almost always use Lime and Gypsum (aka Clay Buster). They sell both at Home Depot, the Clay Buster is around 5.49 a bag, the lime around 3.59 or so, both are in about the same area of the garden section.

    I usually use:
    Light application: 3 bags of each per 1/4 acre, 10-14 bags each per full acre
    Medium application: 4-6 bags each per 1/4, I don't go past 16 bags each per full acre (due to the WEIGHT, 1200+ pounds here).

    In your case I would go with a medium application, I don't normally go heavier, roughly the apps correspond to:
    3-4 bags = 120 - 160 pounds, 1/4 acre = 11k sq.feet.
    so a bit over 10 pounds per k, maybe 15?

    Which, how it tells you to apply it on the bag, the label:
    Light: 10 pounds per 1000 square feet.
    Medium 20 pounds / k
    Heavy: 40 lbs / k
    So, in the ball park.

    The stuff comes in 40 pound bags, the only consideration here is by the time you're putting down 6 bags each we're also talking 480 pounds LOL, so consider this as you load the bags onto the cart, 4 bags each per 1/4 acre might be a good thing for starters.

    Then, repeat every 6 months until the desired effect is achieved, also adjust the formula as needed (more, or less, or keep the same, if in doubt keep it the same). I usually do this once in spring, once in fall, for my customers I do 3-4 per 1/4, rarely do I go over 6, it's just one of those things, has to get done.

    You'll see some effect right away, but it takes 6-12 months for the stuff to work its way through, hence twice / year is enough.
    I'd recommend seasonal core aeration as well, this would help work the soil around so the material gets worked through faster.

    Lime and Gypsum, yes sir.
  4. Marcos

    Marcos LawnSite Gold Member
    Messages: 3,720

    mlong30, just like 'big guy' said, it will take MULTIPLE applications of split-pea sulfur to get a pH reading down from 8.0 to 7.0. And topsites, lime RAISES the pH reading, sulfur LOWERS it! And as far as gypsym is concerned, it is only useful for adding calcium, and 'breaking up' clay soil. But if it's not worked into the soil with a really good aeration, and if it's just 'broadcast spread' like you described, the lawns tend to develop a 'shell' on the top that act as a mechanism for water to tend to begin to 'sheet runoff' the yard. But again, good, deep aeration helps cure that.
  5. Marcos

    Marcos LawnSite Gold Member
    Messages: 3,720

    Hey- I just remembered that you were the one that sent over the digital pictures of the 'bluegrass desert', and the ones of the good aeration job later. How is the it coming along?.......And what I meant above by 'multiple applications' of sulfur was to do them in STAGES; one this fall, one next spring, one next fall, until the pH is corrected. Remember that the alkalinity / acidity changes (up or down) 10 X for each 'point' between numbers, say for example, between points 7.9 and 8.0, and so forth. So therefore, it takes a lot of TIME for that material, (and the CORRECT material), to penetrate the soil structure to chemically change things- (especially CLAY, since clay particles are REALLY small!) I'd go with 50# of sulfur per 1000 sq feet ( 11 bags for a SOLID 1/4 acre lawn). And I'd recommend repeating this next spring and fall as well. Then do another soil test in the spring of 2009. Good luck.
  6. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    well dang cores DO get pulled up and if you do this every year for 5-8 years it would be like tilling it all up at least once...
    The gypsum 'sifts' into the top layer, but once however much you dump is done reacting, maybe the top 1/4 to 1/2 inch of soil has been broken up but the BASE is still all clay... So you aerate it in order to pull up some clay plugs and then dump MORE gypsum, which also goes down in the holes and thus it penetrates further down, it does work it in there...
    Yes I agree it takes time, aeration or not the gypsum takes time, but beyond that the aeration helps it get into the soil and down to the base, and it's not a one-time application either, has to be repeated once or twice a year until the problem is gone, but the effects are cumulative and aeration also helps break it up, which...

    Gypsum is calcium yes but so is lime, lime is calcium carbonate and gypsum is calcium SULFATE (dihydrate)....
    Gypsum in and of itself does nothing to the ph, lime raises it...

    And yeah he did say lower ph...
    In clay soil...

    Sorry that's just odd, I got caught off guard...

    Because there's not much you grow in a 8.0 ph clay soil, really almost nothing grows there...
    But that's hella funny too, because a high acid clay is good for some things, and more often than not it's a high acid clay, or a low ph clay... Low ph = high acid, is it my confusion or their mistake?

    And no, just because someone throws 8.0 and 7.0 and 6.5's around doesn't mean I assume it has been tested.
    Those are standard measuring points on the scale, anybody could've said those figures 'must be where the ph is'...
    Because more often than not it's high acid clay where GRASS isn't growing.
    As for if it's 8.0 clay and you'd want to grow grass then I'm sorry, just use a high nitrogen high phosphorus fertilizer...
    If you can find that, might have to use two fertilizers, one starter, one regular.
  7. Marcos

    Marcos LawnSite Gold Member
    Messages: 3,720

  8. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Ok, at least now I'm beginning to understand why some folks around here insist on dumping sand in their yard... But I'm out East and dumping sand here is near the dumbest thing I've ever heard of, my attitude is do you see lawn growing on VA beach?!

    But I get you guys now, sorry for the mix up.
  9. Marcos

    Marcos LawnSite Gold Member
    Messages: 3,720


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