PDA

View Full Version : Ph testers


wcb607a
01-22-2009, 11:40 PM
Have any of you guys used the ph testers from Gemplars. The ones that you stick in the ground and wait 1 minute. What do you guys think about them and are they any good for accuracy?

mngrassguy
01-22-2009, 11:51 PM
Yes, I have used one. No, they are not accurate.

A soil test is the only good way to measure Ph. jmo

Whitey4
01-23-2009, 03:45 AM
Hanna Instruments have a good accurate pH meter for under $100. Only meters with a glass electrode are accurate, the rest are trash.

RigglePLC
01-23-2009, 03:16 PM
I have three cheap meters--cost about $15, each. Soil test on my lawn by a major laborotory was at pH 6.8.
J&M Instruments meter reading averaged 6.5
Rapidtest meter 7.1
Ferry Morse meter 7.03
The variation was that they were off by up to 6 tenths of a point.
I also tested mine using Diet Coke as a test: found pH of 5.8.
It is best to compare it with a known soil test, before you begin to use it. Accuracy only fair. Even if you follow the directions carefully.

Ric
01-23-2009, 03:34 PM
I have three cheap meters--cost about $15, each. Soil test on my lawn by a major laborotory was at pH 6.8.
J&M Instruments meter reading averaged 6.5
Rapidtest meter 7.1
Ferry Morse meter 7.03
The variation was that they were off by up to 6 tenths of a point.
I also tested mine using Diet Coke as a test: found pH of 5.8.
It is best to compare it with a known soil test, before you begin to use it. Accuracy only fair. Even if you follow the directions carefully.

Riggle

I have an older Hanna pH/EC meter and even the good ones need to be calibrated regularly to be correct. Fact is by the time you buy the calibrating solutions you have close to the cost of the meter. But even brand new meters right out of the box are not always calibrated correctly. BTW I also had a $ 15 Rapidtest that wasn't to far off.

phasthound
01-23-2009, 07:30 PM
I have three cheap meters--cost about $15, each. Soil test on my lawn by a major laborotory was at pH 6.8.
J&M Instruments meter reading averaged 6.5
Rapidtest meter 7.1
Ferry Morse meter 7.03
The variation was that they were off by up to 6 tenths of a point.
I also tested mine using Diet Coke as a test: found pH of 5.8.
It is best to compare it with a known soil test, before you begin to use it. Accuracy only fair. Even if you follow the directions carefully.

For those who don't know, it is important to remember that a change of one pH unit represents a tenfold change in hydrogen ion concentration; for example, a solution with a pH of 6 has 10 times the hydrogen ions as one of pH 7, and pH 5 has 100 times the hydrogen ions of pH 7.

ted putnam
01-23-2009, 08:00 PM
I have a Kelway in each of my trucks. I always thought I had a decent tool(even though not a lab test) but a quick way to get a general idea of pH. I guess maybe I have a piece of crap and didn't know it:confused: I guess I need to do some research on it....

Whitey4
01-24-2009, 01:08 PM
I have cross checked quite a few meters. My findings where that any pH meter that did not use a glass electrode were simply measuring the pH of the distilled water used to make the slurry. Sure, a drop of lemon juice would change the reading, but the metalic sensors only measure the pH of the liquid, not of the soil. I found the same results with litmus paper testing too.

I started with a RapidTest meter, but the results were always the same, which made me rather suspicious. Then I started adding lemon juice, or epsom salt... and that changed the reading, but only because it was dissolved in the liquid.

A meter tests the conductivity of the solution.


How a pH meter works
When one metal is brought in contact with another, a voltage difference occurs due to their differences in electron mobility. When a metal is brought in contact with a solution of salts or acids, a similar electric potential is caused, which has led to the invention of batteries. Similarly, an electric potential develops when one liquid is brought in contact with another one, but a membrane is needed to keep such liquids apart.
A pH meter measures essentially the electro-chemical potential between a known liquid inside the glass electrode (membrane) and an unknown liquid outside. Because the thin glass bulb allows mainly the agile and small hydrogen ions to interact with the glass, the glass electrode measures the electro-chemical potential of hydrogen ions or the potential of hydrogen. To complete the electrical circuit, also a reference electrode is needed. Note that the instrument does not measure a current but only an electrical voltage, yet a small leakage of ions from the reference electrode is needed, forming a conducting bridge to the glass electrode. A pH meter must thus not be used in moving liquids of low conductivity (thus measuring inside small containers is preferable).
The pH meter measures the electrical potential (follow the drawing clock-wise from the meter) between the mercuric chloride of the reference electrode and its potassium chloride liquid, the unknown liquid, the solution inside the glass electrode, and the potential between that solution and the silver electrode. But only the potential between the unknown liquid and the solution inside the glass electrode change from sample to sample. So all other potentials can be calibrated out of the equation.


http://www.seafriends.org.nz/dda/ph.htm

Metalic electrodes are too conductive. Only a high impedance glass electrode measured against the reference elctrode are accurate.

Whitey4
01-24-2009, 01:19 PM
Not sure if this is clear, but bottom line... any accurate pH meter has to use a glass electrode, be battery powered and must be calibrated with reference solutions on a regular basis. The elctrodes must also be stored wet, in a special storage solution. This helps maintain the impedance of the electrode. If allowed to dry out, it must be soaked in storage solution for 24 hours before used for making measurements.

Whitey4
01-24-2009, 01:26 PM
This is the key part of the whole thing, excepted from above:

Because the thin glass bulb allows mainly the agile and small hydrogen ions to interact with the glass, the glass electrode measures the electro-chemical potential of hydrogen ions or the potential of hydrogen.

ONLY the hydrogen ions penetrate the high imedance of the glass... while a metalic probe will measure many more larger free ions, which skews the measurement. Thus, the metalic probe measures all ions, not only the hydrogen ions as a glass electrode does. That is why it measures the pH of the solution used to make the slurry, not of the soil itself.

muddstopper
01-24-2009, 01:39 PM
I have a question for all of you that treat soil based on a Ph meter. If your soil ph is 5, what do you use to correct the Ph. Supposed your ph is 9, now what do you use to correct the ph. One thing for sure, your ph meter, no matter how accurate, cant tell how much or which amendment to use to correct your problem.

In my examples of ph5 and ph9, calicitic lime will move both ph's closer to ph7, but in nether case would calcitic lime be the correct answer 100% of the time.

Whitey4
01-24-2009, 02:11 PM
I have a question for all of you that treat soil based on a Ph meter. If your soil ph is 5, what do you use to correct the Ph. Supposed your ph is 9, now what do you use to correct the ph. One thing for sure, your ph meter, no matter how accurate, cant tell how much or which amendment to use to correct your problem.

In my examples of ph5 and ph9, calicitic lime will move both ph's closer to ph7, but in nether case would calcitic lime be the correct answer 100% of the time.

The soil here is sandy loam, which tends to be acidic. I only lower pH in garden beds, never on turf and I rarely have need to do that unless it is a new account where the LCO got sloppy with his lime apps.

I've never seen a pH over 7.2 here, it's usually around 5.8 before I would treat. I would use 20 to 30 pounds/k of dolomitic pelletized lime typically, depending on my measured results. I would repeat my measurements again at 6 month intervals. Even at that, I don't use much lime.

The LCO's around here put it down every year. It's a cash cow for them. I like to make my pH measurements right in front of the customer and explain why lime is often a waste of money.

Your question this sounds like a setup question... if not lime, then what?

Whitey4
01-29-2009, 12:55 PM
I have a question for all of you that treat soil based on a Ph meter. If your soil ph is 5, what do you use to correct the Ph. Supposed your ph is 9, now what do you use to correct the ph. One thing for sure, your ph meter, no matter how accurate, cant tell how much or which amendment to use to correct your problem.

In my examples of ph5 and ph9, calicitic lime will move both ph's closer to ph7, but in nether case would calcitic lime be the correct answer 100% of the time.

Bump for a request that Mudstopper expound a bit on this post...

ted putnam
01-29-2009, 02:17 PM
Whitey, Thanks for the visitor message. My Kelway has a brass tip with what appears to be aluminum contacts on the side. I'm not sure what is in the guts of the thing. I'll have to research it. I paid over $100 for each of them at A.M. Leonard. They sell quality hand tools and it was the most expensive pH tester they had so I thought I was getting a quality(accurate) tool.

Ric
01-29-2009, 06:10 PM
I have a question for all of you that treat soil based on a Ph meter. If your soil ph is 5, what do you use to correct the Ph. Supposed your ph is 9, now what do you use to correct the ph. One thing for sure, your ph meter, no matter how accurate, cant tell how much or which amendment to use to correct your problem.

In my examples of ph5 and ph9, calicitic lime will move both ph's closer to ph7, but in nether case would calcitic lime be the correct answer 100% of the time.

Muddstopper

10 pounds of 0-0-0-90 sulfur per thousand will lower pH one point in 30 days. But just like adding lime it is only a short term solution. Follow up application should be done by pH testing.

Raising pH should also be done by soil testing. Calcium lime is not always the correct product.

Whitey4
01-29-2009, 06:22 PM
Whitey, Thanks for the visitor message. My Kelway has a brass tip with what appears to be aluminum contacts on the side. I'm not sure what is in the guts of the thing. I'll have to research it. I paid over $100 for each of them at A.M. Leonard. They sell quality hand tools and it was the most expensive pH tester they had so I thought I was getting a quality(accurate) tool.

There ARE some metalic probe based in-soil testers that are supposed to work well, and I am not familiar with the meter you are using... so I may have gone a bit over the top when saying they aren't accurate. I DO know the cheap metalic probes aren't accurate though, like the RapidTest meters. An in soil tester would have to be housed in something that would not get damaged when inserted into the soil, so I would guess that there are more sensitive parts inside the housing on an expensive in soil tester. I also believe that any accurate meter does require a power supply of some kind, a battery, whatever but can't swear to that either.

Kelway should be able to offer you more info on this I would think. The brass probe may be treated with other materials that sheild the measurement from other free ions that are not hydrogen free ions. The Hydrogen ions are smaller than most other free ions are, more mobile, which is why a high impedance probe only measures the hydrogen. The other free ions can't penetrate the high impedance glass. Does Kelway caution against using any kind of abrasive cleaner on the probe?

ted putnam
01-29-2009, 07:28 PM
. Does Kelway caution against using any kind of abrasive cleaner on the probe?

Yes. Each tester comes with a carrying case and a special cleaning cloth.

timturf
01-29-2009, 08:17 PM
I have a question for all of you that treat soil based on a Ph meter. If your soil ph is 5, what do you use to correct the Ph. Supposed your ph is 9, now what do you use to correct the ph. One thing for sure, your ph meter, no matter how accurate, cant tell how much or which amendment to use to correct your problem.
In my examples of ph5 and ph9, calicitic lime will move both ph's closer to ph7, but in nether case would calcitic lime be the correct answer 100% of the time.

Ric posted:
Muddstopper

10 pounds of 0-0-0-90 sulfur per thousand will lower pH one point in 30 days. But just like adding lime it is only a short term solution. Follow up application should be done by pH testing.


Two great post!

Even if hand held ph meters where extremely accurate in giving the soil ph, they don't tell you how much material to add to increase or decrease the soil ph! You must use a soil test from a quality soil testing lab

Generally
If ph greater than 7, you must use sulfur, and a ph lower than 7, you need to use lime! In lowering the ph, which liming material to you use? Dolomitic or calicitic? A soil test will tell you. PH of 7 isn't the magic number, it depends on the species of grass you are growing!

I can't understand how calicitic lime will lower the soil that has a ph of 9 to a 7 ph.

Kiril
01-30-2009, 12:14 AM
Chasing pH is generally a futile pursuit. Keep your SOM at a decent levels will go a long way towards buffering changes in pH. Beyond that, select plants that are adapted to the indigenous soil & climatic conditions so you won't have a need to adjust the pH.

Whitey4
01-30-2009, 08:50 AM
Ric posted:
Muddstopper

10 pounds of 0-0-0-90 sulfur per thousand will lower pH one point in 30 days. But just like adding lime it is only a short term solution. Follow up application should be done by pH testing.


Two great post!

Even if hand held ph meters where extremely accurate in giving the soil ph, they don't tell you how much material to add to increase or decrease the soil ph! You must use a soil test from a quality soil testing lab

Generally
If ph greater than 7, you must use sulfur, and a ph lower than 7, you need to use lime! In lowering the ph, which liming material to you use? Dolomitic or calicitic? A soil test will tell you. PH of 7 isn't the magic number, it depends on the species of grass you are growing!

I can't understand how calicitic lime will lower the soil that has a ph of 9 to a 7 ph.

I would never argue that a soil test is best, nut I think there is some misunderstanding about whether or not calicitic or dolomitic lime is the right choice:

In summary, the Ca:Mg ratio concept is unproven and should not be used as a basis for fertilization or liming practices. Having sufficient levels of Ca and Mg is the proper method of evaluation, rather than trying to manipulate ratios.

Why the interest in Ca:Mg ratios?
Good question. From the above-mentioned statement that Ca and Mg levels are higher than needed for crop production in Iowa soils, you can easily conclude that ignoring the ratio is just fine. Research confirms that this conclusion is justified; however, promotion of the ratio concept persists today despite many years of research that indicates otherwise.

http://www.ipm.iastate.edu/ipm/icm/2003/4-21-2003/camg.html

Cation Ratios and Crop Production:
Although the concept of optimum cation ratios has been debated and promoted by agronomists over time, there is very little research evidence to show that these ratios have either a positive or negative effect on crop production. Liebhardt (1981) showed a direct relationship between soil pH and exchangeable Ca(+)Mg. The relationship of pH to crop growth was verified in greenhouse trials in Ohio (Eckert and McLean, 1981). It is reasonable to believe that increased growth reported by Bear and coworkers in their earlier research was a consequence of changes in soil pH rather than changes in cation ratios.

http://www.extension.umn.edu/distribution/cropsystems/DC6437.html

Basically, it is my understanding that as long as there is sufficient Ca and Mg in the soil, it really doesn't matter much if one uses dolimitic or calicitic lime to manage pH. I also have not personally seen any notable difference in turf health on lawns with a pH of 6.0 vs. 6.8. The natural pH around my area runs around 6.1 to 6.2, and only occassinally do I see it below 6.0, which is why I don't attempt to make any adjustments until or if it goes to 5.8.