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PH Soil Tester

Posted by emnten tn (My Page) on
Tue, Aug 30, 11 at 16:01

Has anyone ever used the Control Wizard PH soil tester meter? I found it on Home Harvest Garden Supply for $64.95.
i would like a pretty good meter to check ph of soil around my azaleas and blueberries.
If anyone has or knows of a good meter, please let me know.


Follow-Up Postings:

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RE: PH Soil Tester

I was interested in buying a tester myself. The digital and analogue meters looked easy to use. So Did a lot of Googling to find the best at the best price. I ran across some people that did studies, The results where that none of the electronic were consistent in trials they made. They recomended the chemical type.
Why wouldn't the litmus paper, type work, like the swimming pools use?


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RE: PH Soil Tester

Litmus paper is a problem because dark colors will swamp out the indicator color. You would have to use a paper with subtle color changes in the 6-8 range to get a usable reading for soil, and by the time you dunk it into a brown liquid, you can't read the color changes.

Any meter needs to be calibrated or at least checked when used. Simple things like vinegar and baking soda could be used to check the calibration. The problem with pre-made calibration solutions is that they will sit in a bottle for months or years and probably not be accurate. Fresh made baking soda in water (concentration almost doesn't matter - a teaspoon in a pint of water will work) - will buffer at pH 8.3, for example. There should be a way to do this with diluted 5% vinegar to come up with a pH 5 or so standard, but I don't have that on the tip of my tongue.


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RE: PH Soil Tester

The soil pH meters I have seen usually do not accurately measure soil pH. Many will give the same reading in a soil solution as in vinegar or a baking soda solution. None of the meters will indicate why the soil pH is where it is, Calcium or Manesium deficiency, which a good reliable soil test will do. For the price of most of those meters you can have soil tests done for several years.


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RE: PH Soil Tester

Yes, just get a basic soil test done, usually about $10.

Your local cooperative extension service (see link) can give you names.

Sue

Here is a link that might be useful: Find your local Coop Ext. Service office


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RE: PH Soil Tester

At university back in the '60s we usually just used paper. Take the soil and add it to a some water, shake it up and let it settle, filter through a coffee filter. Determine pH with the paper strip. I would recommend the paper strip for fish tank water from the aquarium supply or pet store. Below the range on the fish tank strip just call it acid. Above the range on the fish tank paper just call it alkaline.


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RE: PH Soil Tester

Using litmus paper to test your soils pH will give you a ball park number but you will not know why your soils pH is where it is. The test done by a soil test lab will give you the amount of Calcium and Magnesium in your soil as well as the pH and what needs be done, if anything, to correct a low or high soil pH.


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RE: PH Soil Tester

I had looked at all the soil ph testers on amazon, and only 1 had good reviews - The luster leaf rapitest soil ph kit (model 1612).
As for the test strips, I tried using them myself, but they seemed to give the ph reading for the water that was in the soil.. rather than the ph of the soil itself.

fwiw..
The rapitest kit is color-coded, and the color scale allows for pretty good readings between 5.5 and 7. Above and below that it's more of a darker shade of color, rather than a different color.
I found the colors at 7 and above to look more blue-ish than greenish. The brown and orange were true to the color chart though.

I've learned that the ph of the water used for the test will affect the results, so I posted a question on the forums, and also emailed luster leaf about it.


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RE: PH Soil Tester

Distilled water, pH of 7.0, is the only water one should use when doing a soil pH test. Since a good reliable soil test that provides much more information then simply what the soils pH is costs relatively little ($9.00 to $13.00) you can get better information for many years for the same cost.


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RE: PH Soil Tester

I'll agree with that. The rapitest soil ph kit is apparently not as it seems. It apparently requires calculating the soil's ph, based on the combined ph of the 1 part soil and 7 parts water used in the test.
A professional test would be much more helpful I would imagine.


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RE: PH Soil Tester

If you already know the general pH range of your soil, you can use some much more specific and reasonably priced strips from scientific supply companies.

Mix soil sample with distilled water, mix well/let stand over night, and measure.

Here is a link that might be useful: link


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RE: PH Soil Tester

Someone has suggested the test strips from scientific supply companies. Have you compared prices to aquarium test strips from Walmart which will also give you soluble nitrates and nitrites?


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RE: PH Soil Tester

I did soil testing today these two testers read the moisture level differently. The other one read "wet" and Rapitest read "3" not wet. I think Rapitest is more accurate than the other one. Because I checked the soil by hand it is not wet but I don't know inside.

Any advice for a reliable soil tester will be appreciated.


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RE: PH Soil Tester

Another picture


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RE: PH Soil Tester

  • Posted by ericwi Dane County WI (My Page) on
    Wed, Nov 14, 12 at 11:14

I grow blueberries here in Madison, Wisconsin. Our native soil has pH around 7.6, and our water supply(City of Madison) also has pH around 7.6. Since blueberries do best at soil pH around 4.5, I am obliged to do my own pH testing. The least expensive, and most reliable method that I have found is to use bromocresol green indicator solution, which can be found at HMS Beagle online. This is a standard test solution, so other chemical supply companies should have it available. Using distilled or DI water, a small soil sample is made into a slurry, and next a funnel with filter paper is used to get a clean sample. Add a drop of indicator(bromocresol green), and the sample will turn yellow(pH = 3.8), green(pH = 4.6), or blue(pH = 5.4). The test result is not ambiguous. There are other indicator solutions available to cover other portions of the pH spectrum. I have also used a Hanna Instruments portable pH probe, which worked well. The test results from using the pH meter, and bromocresol green indicator solution, were in agreement. You can get better resolution with a pH meter, plus or minus 0.1 unit. With indicator dye, the result is plus or minus 0.2 unit. But that is close enough for growing blueberries. A small bottle, about one fluid ounce, of dye indicator sells for two dollars, and will allow about 100 tests. My pH meter was 45 dollars, and lasted three years. However, pH meters are fragile, they have a glass bulb that can be broken. The glass bulb can get clogged up and become inoperative, either from contamination like dirt, or from dissolved limestone. I was able to get my pH meter back up and working by cleaning the electrode with Lime-Away. Also, pH meters have a battery that must be replaced periodically. To get an reliable reading, the pH meter has to be calibrated before use, with a solution of known pH. You can buy calibration standards, but I was using regular 5% white vinegar(3.5) and Madison City tap water(7.6) to calibrate my meter, and that seemed to work OK. I don't use metal probe type pH testers because I have been told that they can't be calibrated using a solution of known pH.


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RE: PH Soil Tester

Good post ericwi, thank you. Someone mentioned above, correcting for the pH of the water you use to make the slurry, and I just wanted to confirm that a cheap jug of store bought distilled water will take care of that problem.

Chiliwin: I'm not sure I understand how your Rapitest meter works. Is there a switch or buttons to select the parameter being tested?

I think any meter is going to be more accurate with a slurry rather than sticking into semi-dry soil.


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RE: PH Soil Tester

Thank you for the replies. It is all valuable information for me. Very well explanation about soil testing methods, thank you. "bromocresol Green Indicator Solution" will be more reliable. I am interested to "Hanna Instruments Portable pH Probe" it sounds to me it will be more easier for me. I do not see any batteries of these testers and the sensors for lights are working perfectly. When I covered it the indicator changed. I used the buttons when i tested. Whenever I changed the button's position the indicator changed. Both testers have same result for the Light and Ph except the moisture. I considered Rapitest 4 in 1 is reliable (brand new and very cheap). The other one is a bit old and it has only for Moisture, Light and PH there is no marking brand name but it is made in Taiwan. I will clean it with vinegar to calibrate it. The fertility test of Rapitest is "Too Little" I checked the soil in the container as well as pot soil in the bag (new) but the result are same.

Thank you for providing me all these information.


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RE: PH Soil Tester

This thread is a little old but you all might be interested to know that Consumer Reports did a review of various soil ph test kits/methods-

Here is a link that might be useful: Click here for the Consumer Rprts article/vid


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RE: PH Soil Tester

My 4 in 1 Rapitest has broken the switch, it does not go smoothly like before. Rapitest is too short for big containers too Now I ordered another digital one.
Thanks for the link.
Caelian


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RE: PH Soil Tester

The only reliable soil pH testers you'll be able to buy are at least $175.00. Anything else is just guessing. To buy a professional grade pH tester be prepared to spend $300 or more.

I don't understand how there can be such a major deficit of reliable soil pH meters when our country has and has had hundreds of thousands of farms.

Using a color spectrum to evaluate your pH is not a good idea. In a pinch it will have to do but as a primary means of testing it simply isn't accurate. When I have to attempt to pH my plant's root zone's I collect the runoff water under their pots and use my hydro pH tester. It has to be extrapolated as it isn't a direct reading. But it's a system that can tweaked to the point of being close to accurate after many trials and errors.

Here is a link that might be useful: BlueLab pH Soil Tester


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RE: PH Soil Tester

The $40 Hana hand held meters are good to +/- 0.1 pH unit IF they are properly cared for and calibrated. If not cared for and properly calibrated, it doesn't much matter what you pay for it - it will be worthless.

The metal probe pH testers are totally worthless.

We had a good discussion about this in September - see the article liked near the bottom of this thread for some good information.


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RE: PH Soil Tester

I know that pH meters at under $40, cannot be trusted Unless you have a way to check them. AND you CANNOT calibrates them either.

I think the simplest test to find out how accurate your pH testes is to make a vinegar solution from 5% acidity vinegar: Here it is:

--- DILLUTION ----------- pH------
Straight ----- -------------- 2.40
1v/1 w------- -------------- 2.56

...............................................
1v/63w ----------------------- 3.3
to get a pH of 4 from a 5% acidity vinegar, you have to dilute it almost 1500 time( one part vinegar 1500 parts pure water). Practically, you cannot make such a solution without precise laboratory methods in your kitchen.

So what you can do is this: Make a light solution of vinegar( a drops or two in a glass of water) . Use a litmus paper and your pH meter to check it. If you can come close to 0.25 unit that is probably the best you can do. But if the difference is greater than one, then your pH meter is useless.


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RE: PH Soil Tester

This one sells for under $40, allows for 2 point calibration (pH 7 and one other - you pick the other), and works quite well, so long as you care for it properly and calibrate it with proper pH calibration buffers.

Three Extension Specialist from Missouri evaluated colorimetric soil test kits, hand held pH meters and soil pH test probes for field evaluation of soil pH. Their wrok is published in this paper. Quoting from the conclusion:

Soil test pH kits can be used by Extension agents to quickly determine whether soil acidity or alkalinity is a probable cause of poor crop health. Hand-held pH meters and pH color indicator kits were found to provide reliable in-field soil pH measurements. Personnel using a pH color kit were able to distinguished between soils with and without lime. However, interpolating between whole pH values with the color kit was difficult. A soil probe that was inserted into moist soil in plots provided poor response to soil pH and is not suitable for diagnosis of soil pH problems.

Speaking as a retired reaserch chemist with over 30 years of laboratory research experience I can tell you with certainty that the way to test a pH meter is not with a vinegar solution. It is way too variable, and unless your testing comparable pH solution, the range in which you would be testing is far too acidic to meaningful for a pH test in the range of 6-8. If you want to test you pH meter, get a calibration buffer.


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