Testing soil pH

So I’m following the instructions at the link below, and… mine looks a little different. The directions say the mix should be 1:1, 3 fluid ounces of soil, 3 fluid ounces of distilled water. Why is the water so high on the image from the video? That doesn’t make sense to me.

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The rule is equal parts…I use 1/4 cup of each.
In vid they may have just used a different measure but not stated it.

Its not by weight but by volume

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@Spiney_norman ok, I used this. Is this not an accurate way to measure 3 fluid ounces?

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Yep.
I wasnt saying you were wrong…
Slurry tests are messy and the mix looks different with different soils.
If the soil is really dry it sucks up more water too.

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If you dont get enough water to test then use a larger measure of each.

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Thanks, the directions say stir occasionally and let it sit for 24 hours before filtering out the dirt before testing pH and ppm. I’ll keep an eye on it. Would you add more to the same jar or start over?

I test after 5 minutes

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Humm, Never did it that way, always used the kit with the capsules or dropper, shake and let it separate and compared to chart on vial

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This procedure is flawed. Here’s why:

Demineralized (distilled) water initially has a pH of 7 at room temperature. But if you expose it to air the pH will drop to between 5.5-6 pH. If it doesn’t, that’s because some contaminate (if your goal is D.I Water) is raising the pH. Following this method, you’re exposing the water to air for 48 hours.

There are many guides to test soil pH, and googling will reveal methods that are faster, require less soil, and are more accurate and precise. I have to wonder if it’s even worth worrying about, past an initial test before your grow; most of our quality bagged soil will have a decent buffer capacity. As long as you pH your water and any fertigation you add, you should be fine, IMO.

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@Spiney_norman do you follow a similar process, but only let it sit for 5 minutes? Or what is your process?

@KeystoneCops If I followed the same process but only let it sit for 5 minutes as another user suggested, do you think that would provide an accurate reading?

Not an issue. There is so little input required to effect a change that ANY other input will overdrive the (now low PH) distilled water. Will it affect the reading? Maybe by .1…

I would contend that chemical processes will occur at differing rates, affecting PH if you allow to stand for 24 hours. So long as you extract dissolved solids from the soil (which is after all the point) then 5 to 10 minutes is ample. The stuff ain’t gonna get more soluble in 24 hours, you know?

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I just did a slurry test and experiment last night. This is one data point and ymmv.

For the test I used a shot glass full of soil and a shot glass full of distilled water, this is my normal procedure. I let the samples sit for no less than 15-minutes, then tested. I did not strain or remove dirt. The samples are from 4 different plants 1.5-2” below the surface in a 1-gallon pot. These are the first results #1) 6.7, 210 #2) 6.7, 210 #3) 6.4 420 #4) 6.7,210

The second measurements on the same samples were done approximately 15-hours later. The containers had lids during the wait period. The second test results #1) 6.5, 210 #2) 6.7, 210 #3) 6.3, 420 #4 6.7 210.

I recorded 2 changes one of 0.1 pH and one of 0.2 pH. I did not find these changes to be significant enough for me to pull the sample and wait longer than 15-minutes. So my procedure will be to wait 15-minutes test and move on. I am planning on performing the test again the next time I do a slurry test.

@TripleB sorry to be so long winded in your journal but I thought it may help.

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Ymmv?
How do you test if you don’t filter out the dirt?
@Bubblehead

Sorry, Ymmv - Your mileage may vary

I just put my probes right into the slurry. Hasn’t hurt them. When I’m done I clean them good but I do that every time anyway.

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I’m guess your using a meter like this then

Nope this one

And this one

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So I did the test again and filtered out the dirt a couple times after about 30 min. Stirred it two differently times and let it sit in between. The result was 6.4, which would be good but I was expecting the pH to be high. Apparent the two prongs in the dirt testers suck, but it had the pH between 7-8. Here’s some photos of my girl 2.5 weeks in. I’m concerned about the growth rate along with the leaves curling a bit and the purple stem. Apparently those are all signs of high pH. Does it look like the pH is to high based on the images? @Myfriendis410 @Spiney_norman @KeystoneCops @Bubblehead

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Looks pretty runt like? Possibly over watered? May explain the droopy leaves? Just a guess though.


The one my finger is behind is a Johaar and was born or up periscoped New Years day. This plant is going to have very large leaves. The one behind it is a couple weeks older and is a Jawa Kush. Again the leaves are pretty big. One thing I do is water sparingly, primarily around the perimeter, and only as often as needed. I ph my solution after everything has been added to 6.8.
One other thing that Ive had happen is, when a baby plant gets too much light the internode spacing stays very close and compact. In addition, leaves may stay smaller to prevent evaperation. Im wondering if you should promote a less compact plant by raising the light a tad?

@Cannabian I don’t know what born up or periscoped means, but I planted mine with a quarter inch tap root facing down on Dec 24 or 25. Speaking of terms, is there a glossary or something because people keep using terms and acronyms that I have no idea what they mean.

You don’t think it looks like a pH issue? I’ve been using RO water from my own filter. After it sits for a day or so the pH is around 7.0 and the ppm is around 25. I planted in Fox farm ocean forest and was told not to add any nutrients for the first month. I’ve been using a spray bottle, dampening the top while trying to stay away from the plant twice a day as suggested in the grow guide.