Home pH Testing of Soil

Hello folks...

Is there a way to test garden soil at home using one of the digital, pocket pH testers?

I have a Hach Pocket Pro pH Tester but am unsure how to go about turning garden and/or container soil into a liquid sample to test with the Tester.

I would imagine the pH of whatever liquid you would use to dissolve the soil would have to be taken in account when reading the pH that appears on the tester.

Thanks!

Mike

[Worth1]

Originally Posted by MikeBiondo

Hello folks...

Is there a way to test garden soil at home using one of the digital, pocket pH testers?

I have a Hach Pocket Pro pH Tester but am unsure how to go about turning garden and/or container soil into a liquid sample to test with the Tester.

I would imagine the pH of whatever liquid you would use to dissolve the soil would have to be taken in account when reading the pH that appears on the tester.

Thanks!

Mike

Just use distilled or RO water that way the PH will always be neutral.
You can also just test the water alone and this will tell you what the PH is of the water.
Pure water should be 7.

I then just turn the soil sample into a slurry to test the PH.
Works for me.

Worth

[moray-eel-bite]

Distilled or RO water are never actually 7. Because there are no buffering components left in them, they will often read as low as 5 simply because they are exposed to atmospheric CO2 etc (this is why global warming and excess CO2 from fossil fuels cause such problems. However, using distilled water to test the pH will work very well and cause very little interference. All this is to say that if you test the distilled water and don't get 7 that is to be expected.

Cheers.

[solid7]

Yes, but what you fail to mention, is that Distilled or RO water that has not been left exposed to ambient air, will still be fine to use for testing.

RO water into a sterile contiainer, or Distilled water, use immediately upon opening to make your slurry.

Test the water to confirm, in the manner mentioned above.

[Worth1]

Well I assumed that everyone had an RO filtering system so it would be fresh.

My bad.

Worth

[solid7]

Originally Posted by Worth1

Well I assumed that everyone had an RO filtering system so it would be fresh.

My bad.

Worth

I don't think it's a bad assumption, but it was a good point to raise bout the CO2 absorption. I used to raise aquatic plants, and when I first got into the hobby, I had a heck of a time with PH swings, and could never figure out why... ahaaa ha ha...

[moray-eel-bite]

For the purposes of testing soil even water exposed to the air and allowed to equilibrate will be fine. The concentrations of ions in the soil will swamp any CO2 contamination. The difference will be less than a 0.1 pH shift, which for soils and general testing is irrelevent.

[TomNJ]

I recall reading many moons ago that one should mix the dried and screened soil with distilled water in equal volumes, shake well, allow the soil to settle, and then measure the pH of the water layer. Can anyone confirm this? I would think that measuring a slurry would result in a varying amount of soil particles between the electrodes which may affect the readings.

TomNJ/VA

Thanks for the responses!

So, if I calibrate my pH tester with 7.0 buffered standard, and then take a reading my distilled water and it's not reading 7.0, is there any adjustment I can make to the soil pH reading I measure? In other words, if my dilution liquid is not neutral, won't that throw off the reading? And, if so, is there a way to extrapolate the correct pH from the tester reading, or do I just go out and try another bottle of distilled water?

Thanks again...

Mike

[Worth1]

I guess you could fool around with the water to make it 7.

Vinegar to make it go down and baking soda to make it go up.
Never really tinkered with it that much and I dont know where my meter is.

If you have your meter already give your tap water a test and see what it is.

A PH of 7.1 is ten times higher than a PH of 7, 8 is 100 times more alkali than 7 and so forth.

Worth

[drew51]

Originally Posted by moray-eel-bite

Distilled or RO water are never actually 7. Because there are no buffering components left in them, they will often read as low as 5 simply because they are exposed to atmospheric CO2 etc (this is why global warming and excess CO2 from fossil fuels cause such problems. However, using distilled water to test the pH will work very well and cause very little interference. All this is to say that if you test the distilled water and don't get 7 that is to be expected.

Cheers.

Ha! Now that is funny. Current co2 is .04% Only one other time in earth's history has co2 been this low. Don't buy into the political stuff which is not allowed here.
Besides the fact that PH is a measurement of hydrogen ions. How many hydrogen ions in co2?
BTW I live surrounded by automotive factories. My rainwater is 7.0. A side effect of clean air. I grow blueberries and have to add acid even to my rainwater.
I use rainwater to test soil PH as it is neutral.

[ChrisK]

Yes, it is difficult to accurately measure the pH of pure water as posted above. Get some DI, RO or distilled water. Don't worry about trying to measure its pH before you add the soil.

Also, it would be better to calibrate your pH meter with two points that span the pH of your sample. e.g. pH 4 and 7 if your soil is acidic and pH 7 and 10 if basic.

[PhilaGardener]

Right, the point about pure water is that it has very little buffering capacity - that is the ability to resist a pH change when acid or base is added to it - so that is why the starting pH is not really relevant.

Originally Posted by PhilaGardener

Right, the point about pure water is that it has very little buffering capacity - that is the ability to resist a pH change when acid or base is added to it - so that is why the starting pH is not really relevant.

Okay, gotcha! Does that also mean it doesn't make too much difference how much water you used to dilute the soil sample?

Mike

[PhilaGardener]

Most sources recommend a 1:1 or 1:2 mix of soil to water as was suggested earlier in the thread.

Here is a document from Clemson that gives a lot of detail (including variations on how to improve the accuracy of the method) if you are interested:
http://www.clemson.edu/sera6/SoilpH_...20Dec%2015.doc