pH Testing

Discussion in 'Gardening Other' started by Daniel W, Dec 7, 2021.

  1. Daniel W

    Daniel W In Flower

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    I have several garden beds that have been treated differently over the years, as well as beds built from hauled in soil. Most Maritime US Pacific NorthWest soils are acidic, and deficient in calcium. I have had my main yard soil tested in the past, which confirms that. Now I'm hoping to be appropriate about adding lime or other supplements to my garden beds. I don't want to add it if they are not acidic.

    I bought a pH testing kit. The result from one test is shown below.

    65DB8E32-4315-4010-A0BB-C5AD36634921.jpeg

    83879531-9726-4202-9429-48963763A7D2.jpeg

    Now I can't figure out if the soil is pH 5.5, 6.5, or 7! The bottom row might read even higher. The instructions state use the rows that match the best.

    Years ago I tried an electronic pH meter. It didn't work at all. Maybe I should get a test kit with different color reactions? The price isn't too bad, but I am on a budget...
     
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  3. Droopy

    Droopy Slug Slaughterer Plants Contributor

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    I have questions now. How important is it to find the exact acidity in your soil? What type of calcium or other things are you planning to add? Is there big difference in plant performance if the soil is a point or so off the best PH value for the plants or will they adjust to that?

    I'm trying to think about what I would do if it were me in your situation. I came to the conclusion that as long as I knew approximate PH, I would be OK with that and try to correct the balance if needed.

    We're on the acidic side too, which is good for me since several of my favourites prefer acid to neutral soil. If I have to add calcium I usually go with crushed sea shells. Our soil is also very dense and heavy so we routinely add sand whenever we plant anything.
     
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  4. mart

    mart Strong Ash

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    From what I can see your soil looks between 6.5 and 7.0 ! Lime is always a good thing if soil is sandy ! Personally it looks fine to me !
     
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  5. Dirtmechanic

    Dirtmechanic Young Pine

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    So first thing is that is a water test. They make testers for soil, and your description of "it did not work at all" perfectly describes the main complaint. The sticks get a layer of oxides (ceramic coating) which needs cleaning off, like a vinegar (acetic acid) soak or superfine sandpaper would do. The second issue is neither dry nor wet soil works. Its all electrical, so a moist soil,like the day after a rain is about right for the stick testers. You could also use red cabbage and distilled water. Screenshot_20211207-212016.png

    Me? I use a stick the day after a real rain.
     
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  6. Daniel W

    Daniel W In Flower

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    Thank you for the informative and thoughtful posts.

    @Droopy, I don't think it has to be that precise. My plant growing tables usually give a fairly wide range, such as tomatoes needing pH 5.5 to 7.5, beans like 6.0 to 7.5, peppers 5.5 to 7.0. My goal is mid range, because more nutrients are available then. Plus, I dont want to add an alkaline material to alkaline soil and make it too high. I actually haven't tested my soil in 10 years. What prompted it this time is I needed topsoil for raised beds, and I don't know the provenance of that soil. Possibly local builders stripping topsoil before construction.

    @mart, I think you are right. The more I look at these, the more it looks like 7. I decided to obtain a different kit that used different colors, to be safe. Im on a budget but I can handle that anyway.

    @Dirtmechanic, your cabbage chart is fantastic! Stuff like that is great. It looks like the range I'm concerned with would be light purple, not much change between 3 and 6 then notable change at 7. My kit called for adding distilled water to the soil, and letting it soak 8 hours, which is what I did. The new one I just now bought is a wet chemistry test. It will take me a few days. It also tests for N P K, which will be interesting to do.
     
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  7. MIKE ALLEN

    MIKE ALLEN Seedling

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    pH testing can drive you around the bend. For the average gardener, you & I are confronted with charts and scales. The generally accepted scale sets the dividing line at 7.0 Measurements reading below this are considered acidic. Reading above being alkaline. Unless one is reading, studying for a scientific post etc, little if anything is considered about the in-betweens. Usually the scales represent for instance: 5.0 5.5 6.0 etc. So for the average gardener that is that.

    In practice. Trying your hand at pH testing, probe, water, mineral whatever. You have a problem on hand. I suggest a reasonably good test. Is to basically work backwards. Example. Select your plant. Check up on it's growing requirement. Take your pH reading. As most of the average gardener's concerns relate to a few plants, the soil/growing medium area is reduced. Stick to this. Then observe the plant's growth etc and feed/adjust etc.
     
  8. mart

    mart Strong Ash

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    Don`t overthink your garden ! Sandy soil or any other will benefit from a little lime ! And a good fertilizer which adds NPK ! We are in deep sugar sand,, about every few years I toss some lime on the soil,,regularly I just use a balanced 13,13,13 commercial fertilizer ! Usually have more than 4 families can eat ! Occasionally it gets some horse manure when stalls are cleaned !
     
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  9. Dirtmechanic

    Dirtmechanic Young Pine

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    Distilled water has a pH of 6 and it confuses me how one might use such an off neutral material to have a 7.0 basis. I actually put out sulfur once based on the instructions. tap water is pH neutral so that it does not dissolve metal pipes or the welded joints of metal pipes. The buffer capacity is not huge because it is man made. I use tap water as a standard, since they spend so much money on its quality. That will shock some people.
     
  10. Odif

    Odif Young Pine

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    That is so cool, ph testing. I tested my spring water with a good tester and the water comes out the side of the mountain at ph6.5, perfect. Some of the vegetation on my land indicates acid soil.

    Plants can regulate the ph in their rhizosphere. This is important because every single species of plant has a ph that it operates at.

    Now the post is about to get wild. Ph is a measure of acid-alkaline and it functions primarily through transfer of protons. There is another measurement you can take with plants. This is called eh. Eh measures the redox capabilities. Redox is oxidation-reduction and is concerned mainly with transfer of electrons. Reduction is the opposite of oxidation. Eh is measured in volts. Eh is more difficult than ph to measure in aerobic soils.

    D5A64BD6-5E0D-462D-9EB3-9C006C4AFCD0.png
    The above chart plots eh against ph and you can see the different perfect zones for the different life forms that inhabit the soil. Should I make a separate thread about redox or should I continue here.
     
    Last edited: Dec 9, 2021
  11. marlingardener

    marlingardener Mighty Oak

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    Odif, please continue your explanation of redox here. Simpletons like me need the background. I'd never even heard of redox, and am not sure I understand it now. You can lead us through and help us learn. Go for it!
     
  12. Daniel W

    Daniel W In Flower

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    Well I got a new testing kit that uses color indicator in solution, instead of papers. I recommends drying the soil before placing it in solution. I have four samples drying now. Probably needs a few days before can test. No hurry. I do feel anxious to see what it shows.

    The kits also test N P K so it will be nice to see what those show too.
     
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  13. Dirtmechanic

    Dirtmechanic Young Pine

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    If you have an oven that has a self cleaning mode, you can weigh the dried soil, cook it through a self cleaning cycle, and then weigh it again. The difference is your soils organic content as a percentage of starting mass. You will need some fine scale, tenths will do.
     
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  14. Daniel W

    Daniel W In Flower

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    @Dirtmechanic, I never thought of that!
    I have used the self cleaning function to strip cast iron skillets down to bare metal, then season them myself. Works wonders with a badly encrusted skillet that you have no idea what someone did with it in years past. Best done in nice weather so the windows can all be open. Lots of smoke.
     
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  15. Dirtmechanic

    Dirtmechanic Young Pine

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    That works also!
     
  16. Daniel W

    Daniel W In Flower

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    Here is the result of the new pH test kit that I bought, testing unamended topsoil that I'm using to fill the last raised bed.

    ACCA19AA-1843-4194-AA9D-6F061D30B5E3.jpeg

    I also used a sample of the same soil, using the pH test strips that I bought earlier. I used the higher dilution so suspended soil particles wouldn't interfere with my reading. I also have a sample settling for a day at the right dilution to test later.

    42DD6E1E-2645-40D5-B3BD-21423C0B0D21.jpeg

    It's difficult for me to judge. I'm estimating pH to be about 6 or 6.5.

    The test kit also included tests for N P K, and all were deficient. I don't know how accurate this test kit is.
     
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