Cheap pH Meters

Discussion in 'Pesticide & Herbicide Application' started by Whitey4, Jan 28, 2008.

  1. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    I have a little el cheapo pH meter... a RapidTest analog unit. Someone told me all they actually do is measure the pH of the water you mix with the soil sample, not the pH of the soil itself. I was looking for a fast, cheap way to get a rough estimate of soil pH, but I'm not sure about this.

    I've tried using both distilled water and tap water. I know my tap water has some buffering agents in it, but there was no difference in my test results. I get 6.8 either way. Adding a couple of drops of lemon juice spikes the pH way down, and a few granules of Epsom salts spikes it the other way.

    I'm waiting for my lab soil test to come back for a cross reference, but in the meantime got another cheap pH test kit. This one comes with a small plastic test tube and a capsule (also RapidTest). Mix the soil, water, then add the capsule and check the color. Same approximate result: between 6.5 and 7.0. I kept this tube for over a week, and the color never changed.

    Does anyone know what technique the labs use? Is this meter worthless, or can I use it for rough guesstimations? Is there another inexpensive way to get fast pH results? TIA!
  2. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    It dawned on me to try a search! Duh.

    Some interesting takes on this. As most people that posted in the threads I looked at, I want to use this thing as a sales tool to get customers to pay for a Cornell soil test. (along with a small "handling" fee). I know that a cheap and dirty pH test won't tell me what I need to know in terms of what materials I should use to adjust pH, but it apparently is good enough to be somewhat reliable enough for a gross indication.

    Generally on LI, either dolemite or a cacluim pelletized lime is used. Since pH generally adjusts slowly from apps, is it a good idea to apply on a regular basis, even if the pH looks OK? If once it starts to drift down, is it harder to reverse? We have naturally acidic soil, but my lawn hasn't been treated in 2 years and is still at 6.7-6.8.
  3. rcreech

    rcreech Sponsor
    Male, from OHIO
    Messages: 6,163


    The pH meter tells you what the pH is, but is doesn't tell you if you need to add lime and how much.

    The Buffer pH (reserve acidity) on a soil test tells you if you need to add lime and the amount. You will not get this info with your meter.


    If you have a pH of 6.0 and a BpH of 6.7 or greater...then technically you can add lime but it won't change your pH.

    If you have a pH of 6.1 and a BpH of 6.1...then technically you can add lime to adjust pH if needed.

    You can't make a lime rec without a buffer pH, as that is what tells you if you need lime. The instrument you have just tells you the pH!
  4. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    That's pretty much what I was saying.... that a low pH reading with this meter means that a soil test MUST be done! Unless I misunderstood you. People seem very reluctant to shell out a few bucks for a good soil test. I JUST want to use the meter to drive the point home.... "Mr Smith we NEED a soil test... see?"

    I in no way am attempting to justify any amendments without a soil test.... I just want a way for these stubborn homeowners to PAY for one! I can talk about manganese and calcium until I'm blue in the face,,,, but a meter... gee, Joe homeowner just might understand THAT! It's either that, or suck it up and pay for the stinkin test myself.
  5. ted putnam

    ted putnam LawnSite Platinum Member
    Messages: 4,746

    I use a ph meter I got from A.M. Leonard. However, it was not what I would call cheap. About $120. I stick it in the soil of every lawn I do. I place it in about 3 locations and take an average. It is pretty handy and there has been many times I have had the customer look at the results as I am reading them.
  6. grassguy_

    grassguy_ LawnSite Senior Member
    from Ohio
    Messages: 633

    I have used the El cheapo PH meters as well, and amazingly they have been fairly accurate for PH reading when compared to sending into the lab! Though as stated, i wouldnt base the findings on whether i should lime or not, our lawns are generally slightly acidic, but it does surely give a good basis to tell the homeowner why the need a complete soil test and give even a better explanation as to why their lawn may be thinning out, or having a significant weed problem.
  7. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,800

    Good idea. I have three cheap soil pH meters. Ferry Morse Seed "Electronic Soil Tester", Rapitest pH Meter, and the best is J&M Instruments pH Tester. All under $20.

    None of them are very accurate. All come with an abrasive Scotch brite pad to shine up the electrodes--very important. Follow directions closely. They seldom agree with each other --and if you do the test three times you will probably get different results with the same meter.

    I used the nearest thing at hand to calibrate.

    Diet Pepsi pH about 4.6.

    Diet Coke about pH 5.2.

    I am pretty sure soft drink companies control this very carefully. (And see now your lunch is a business expense--LOL:cool2:)

    The first two are more convenient and cheaper. Shine the electrode with the Scotch Brite pad and stick it into the soil. Wait 30 seconds. You may need to pour some water into the soil if it is not fully moist.

    The J&M pH Tester has a fat stake, you cannot stick into the ground. Shine the two flat metal strips on the sides. You have to make up a muddy slurry in a coffee mug. Slide it in --wait 30 seconds.

    Close enough as a ballpark figure.
  8. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    The RapidTets meter said to take the soil and add water to form a thick mud. I have to admit, the results have been quite consistant. They tell you to insert the probe for 30 seconds, remove it, clean the tip, and use the Scotch Brite pad. Then reinsert the probe into the sample for 60 seconds. There is a difference between the first and second reading, but the second reading is very consistant and repeatable.

    I have some pretty pricey pH meters for my brewery. (I brew beer at home from scratch, whole barley mash, the works) I wonder if I should try one of those. Or just wait for my soil test to come back... which is likely the smarter option...
  9. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    Ok, after doing some expreiments and cross checks, I am here to say without any doubt that these cheap pH meters aren't worth the postage.

    I checked about 8 samples. All were between 6.6 and 6.8. I'm saying to myself, self, there is something wrong here. So I go buy 3 el-cheapo RapidTest soil pH test kits, the ones with the little tset ube and a samll capsule with whatever in it. Same exact results. So, I go of and collect more samples. Every single one.... 6.6 to 6.8.

    Now, I pull out my Hanna instruments pH meter, which cost me about $249, but is not intended for use in soil, the electrodes are glass enclosed. It's for measuring the barley mash pH when brewing beer from barley grain. Now those same soil samples are coming in at 5.5 to 6.2!

    These cheap units? All they do is measure the pH of the water you mix the soil with. Period. This I now know as fact. The RapidTest stuf is pure garbage, and should not even be sold as a measurement tool at all. Just thought I'd share my findings.
  10. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,800

    Ok Whitey and Badger,
    now how did the meters compare with soil tests results from Cornell?

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