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Lowering PH,

Discussion in 'Fertilizer Application' started by LawnsharkMB, Apr 18, 2012.

  1. LawnsharkMB

    LawnsharkMB LawnSite Senior Member
    Posts: 582

    What is the fastest and safest way to lower the ph of a lawn? I have 7 lawns that the ph is 7.0 to 7.4. All are centipede. I have never applied sulfur to a lawn before. I have read that aluminum sulfate is the quickest but it will burn the lawn. I know SCU and ammonium sulfate will lower the ph but doesn't this take a while? Thanks for any advice in advance.
  2. RAlmaroad

    RAlmaroad LawnSite Silver Member
    from SC
    Posts: 2,194

    I'm in the region also. Sulfur with 10%dolemite (clay) does a great job on our sandy soil. I buy the flakes and spread it at 10lb/K. It needs warm soil to activate it. It brakes down rather quickly. Your centipede will do great if you use ammonium sulfate (21-0-0)@ 1/2lb/K which is a sulfur based Nitrogen. I bet you are a granular guy! Luckily, it can be had in the granular form. I use 14-0-46 liquid and boost it with the ammonium + iron and micros.
    Lesco has the sulfur but it is way too high. I get mine from the co-op at about half of their price. I put it down in November and then again in April and just waited on the heat.
  3. Ric

    Ric LawnSite Fanatic
    Posts: 11,956


    10 pound per thousand sq ft of 0-0-0-90 Sulfur with 10% Bentonite not dolomite will lower pH one point in 30 days. pH is the inverse logarithm of the hydrogen Ion in a solution. Therefore as a Inverse, the More hydrogen atoms the lower the pH number. Small p in math stands to an inverse and the capital H stands for Hydrogen.

  4. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    This is the equation for pH, it is NOT an inverse log, it is a negative log.

    pH = -log [H+]

    The inverse log (or better known as the exponent) of the negative of the pH is the hydrogen ion concentration.

    [H+] = 10^(-pH)


    If I have a [H+] = 0.0002, what is the pH?

    pH = -log(0.0002) = 3.70​

    If I have a pH = 3.70 what is the [H+]?

    [H+] = 10^(-3.70) = 0.0002​
    Last edited: Apr 29, 2012
  5. Ric

    Ric LawnSite Fanatic
    Posts: 11,956

    My Bad, I am getting old and have CRS. The negative log is a Inverse of the positive log. In the case of pH, the measurement of Hydrogen ions in a solution is a reverse of numbers. The higher the pH, the lower amount of Hydrogen ions. The lower the pH the higher the Hydrogen ion count.

  6. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    logarithmic functions are inversely related to the exponential function is the easiest way to remember it, at least for me.

    logbx is the inverse of b^x where b = base

    I think the most important relation to remember here for most people is for every unit change in pH, there is a 10 fold change in [H+]

    Using the example above, increasing pH to 4.7 reduces [H+] by a factor of 10.

    [H+] = 10^(-4.70) = 0.00002
    Last edited: Apr 29, 2012

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