Soil pH meters


#1

Has anyone purchased a pH meter (the kind you stick in the ground that displays the pH) that actually somewhat works?

I have one, but unless the soil is muddy-wet/saturated, it never reads anything but 7.0 even if a soil test has proven it’s much more acidic.

I’m not trying to substitute for a soil test, but I’d like a way to at least monitor the trends and get a general idea.


#2

I was going to purchase one but the posts I read here discouraged me.

I decided to use my aquarium ph test liquid, you fill up a test tube and add a few drops and match the color change chart. I used distilled water and added a few bits of moist soil. I couldn’t read the color because the soil turned the water dark and muddy.


#3

The problem I have with using the strips or even aquarium test, is the right soil to water ratio, and the pH of the water itself.

It seems like the meters you stick in the soil really only work if you make a slurry of water and soil in a container and swish it around first.


#4

You’re right, I just guessed. I searched for a way to do it accurately but all I got were blogs on mixing baking soda and soil in a bowl from stay at home moms. I wanted to find the ballpark so I could plant blueberries and hopefully I got a good enough result for that.


#5

I use them…but usually only to confirm what I already suspect. (And dry soil and they won’t work.)

Once I had a big problem figuring out why a friend couldn’t grow tomatoes in N. Carolina.
When I finally stuck the probe in the ground and it traveled to nearly “4” on the meter…then I knew, and suggested they grow blueberries or something!


#6

I have one that seems to work pretty well. The results I get from it seem to make sense. I tested the probe in areas that I had soil tests done by my local extension office and the results were consistent. Results are also in-line with what I expect when testing soil around my blueberries. It’s not a lab grade piece of equipment, but it seems to be in the right ballpark.


#7

I have the Kelway, but it works poorly in sandy soils. I generally run with the $15 Cornell test kit. Close enough.

I keep both standard and wide range kits in my truck.

http://css.cornell.edu/cnal-forms/CNAL_Form_%20pH.pdf


#8

The pH meters that you see on Ebay and Amazon which cost less than $100 (usually around $10 to $15) are fairly useless. There are accurate pH probes and meters selling in the $130 to $300 range but they are not simple to use, and cannot be stuffed on a shelf and neglected until the next time they are needed: Their probe ceramic or glass membranes cannot be allowed to dry out, their internal reference solution must be topped off, and the buffers used for calibration have a limited shelf life. You are far better off using pH test papers or liquid test solutions like the Cornell test kit stated by @alan.
The laboratory method for testing soil pH starts by taking several soil samples from the root zone (typically 2" to 6") and mix them thoroughly before taking a small portion for testing. Place the portion in a plastic or glass container and just cover the soil with deionized water. Stir for 5 minutes before measuring pH.


#9

And yet, in my experience, over 90% of the time the first reading tells you the story of the soil in that level over a very wide area, unless some new soil has been brought in or if there are varying levels of drainage.

Where I consistently get different readings is from the top few inches and a foot down here. It tends to be more acid in the humid regions as you get lower. During drought, the availability of adequate calcium can depend on the lower soil, but it is difficult getting lime down there after planting. Commercial guidelines therefore recommend separate readings for upper and lower depths before planting to allow tilling in lime.

If you are growing fruit without irrigation this can be important, according to the literature. Probably more for the commercial grower than others. For home growers, a lower pH lower in the soil can be helpful when growing blueberries. I’ve found that blueberries can be very healthy in soil where the upper 9" is close to neutral but lower soil is as high as 5.8.

I discovered this quite by accident while trying to prove that blueberries can flourish in a pH in the mid 6.s. I actually proved myself probably wrong, but learned something about the ability of roots to get what they need from a limited soil profile. Blueberries can also thrive with a thin layer of acid soil on the surface, as long as it doesn’t dry out during the growing season.

Somehow my son found out that Michael Phillips gave me credit for this observation in one of his recent books. Phillips never told me but read my comments in a NAFEX article. Of course, I’m probably the only one who would find that interesting.


#10

Thanks…That explains why my blueberries grow and produce well, even though my soil isn’t suited for blueberries. The soil 6" or more under my blueberries tests around pH of 7.4, regardless to how much sulfur placed down, while the upper few inches has a pH under 5. I also have the good fortune of living in an area where people bag up their pine and oak leaves and place them out by the roadside…I’ve been worrying for 30 years that they will wake up to the fact that leaves are a wonderful material and my free resource will disappear…so far that hasn’t happened.


#11

Yes, mulch is extremely useful in allowing plants to utilize the top few inches of soil, which also happens to be the richest, warmest and best aerated. I find that blueberries especially benefit from mulch and raised beds.


#12

I just use P/H strips, they are cheap and use them every year. Good enough for me.


#13

I’ve tried strips and solutions, but the soil itself discolors the water to a point where it has been difficult to get a reading.


#14

I really worried about this before I purchased mine, but now that I have one I would have to strongly disagree. I got my Apera Instruments PH20 pH meter last year for $40 and have regularly used it 2-3 times per week to monitor my hydroponic solution pH I also left it alone for a couple months with storage solution ($12) and without. I have pH calibration solution (also $12) so I can confidently say that the calibration has never drifted off by more than 0.2 pH and I check and re-calibrate maybe every other week.

I do try to take care of it now that I use it more by rinsing the end off with distilled water and keeping it in its storage solution when not in use. DO NOT STORE IT IN TAP OR DISTILLED WATER! I also am very careful to not damage or scratch the glass bulb… but probably not as careful as I could be.


For those that decide to get one here is my technique fore measuring soil pH that I based on a research paper which unfortunately I lost the source to here it is:

Get 1/4 cup of soil from 2-3" below the surface (sample 1-2 tbsp from 2-4 different areas), mix with 1/2 cup distilled water, stir / shake vigorously and let sit for 1 hour, filter through a coffee filter and then measure pH. Lastly, take whatever reading you get and add 0.3 to get your actual reading (eg: 5.0 pH measured is actually 5.3)


#15

My application is for container culture, by using rainwater and well. I use the strips before watering. Citrus , figs and some tropical trees.


#16

Thanks for sharing your pH find…I had not heard of Apera Instruments PH20 meter before, but yes, that is indeed a true pH probe/meter with glass bulb and ceramic junction. I didn’t relive they could be had in that price range. My main point is that most of the pH probes being sold on Ebay, Amazon, and in the big box stores use bi-metallics and just do not perform. And perhaps I insulted the skill and determination of the gardeners in this forum by suggesting that the true pH probe/meters are too difficult to use. Since I no longer work in an environmental lab, I may put the Apera on my Christmas wish list.


#17

I might as well mention that they also have the Apera Instruments PH60 which is usually $80 new but can be occasionally found at $60 in like-new condition on Amazon. It has several benefits over the PH20 like being able to measure down to 0.01 pH (vs 0.1), a backlit display, a o-ring gasket on the tip so the storage solution doesn’t leak out and most importantly a replaceable probe. I really like the PH20 (and will continue to use it until it breaks) but if I were to buy another pH meter and had $20-30 more to spend I would definitely get the PH60.


#18

Newly purchased ph strips correlated very well with known lab results for me. I stuck with narrow band (ph 4-7) strips. If I lived in a more arid climate, I would make sure that they went to 8.

I was careful to use distilled water in a clean vessel, put in enough water to make a milkshake like slurry, and waited about 15 minutes for the chemistry to settle down before testing. So if you have a lot to do, that’s an issue.

They were el cheapo strips too, from eBay.