Live Stoner Chat Hey stoners! Question about pH in medium vs feed solution

[lunarman]

I have one of these.
https://controlwizardproducts.com/proddetail.php?prod=Accurate-pH-8
Supposed to be a really good soil PH probe. Highly recommended by @Waira

I have not used it since it seemed I have no PH issues once I started using AN Perfect pH. And have not used it when using megacrop either. I just create my solution and then check PH with a good and always calibrated PH pen and then PH it up or down (usually PH up a bit) to 6.4-6.5.

And with the autopots reservoir where I usually dump in 5 gallons at a time, I do check PH once a day too and it usually goes up a bit over the first day so I sometimes ph down whats in the res too. But just to keep it around 6.5.

My medium is a mix of peat and coco and perlite with very small amounts of amendments biochar and EWC and DE sprinkled in for bug prevention.

I don't feel like I have any PH issues but I wanted to just check whats going on in the pot so I used the probe. When I use the soil probe to check PH of the medium around the roots it's PH of 5 or so. Very low PH value. Is this normal? To have your feed solution PH to 6.5 but the medium is 5?

I dont believe I can calibrate the Accurate 8. Not even sure if its accurate or how to check it by comparing with my ph pen. Maybe I should find a way to see if other ways of measuring ph of the medium gives me 5 as well.

Here is a couple of pics of some recent plants where they are growing under these conditions. Bigger plants are Meph autos day 28. Pics taken with COB lighting on which makes pics a bit whiter/brighter.

 

[Waira]

:smoking: hey Lunar,... yes, I'm sure we talked about this before,.. in-pot pH can change quite a bit, especially in the root zone; there are lots of influencing factors at work in there... microbial activity, exudates from the roots, nutrient uptake, actual nute solution, etc. etc.,... what goes in at a certain pH doesn't necessarily stay that way, and AN's "self buffering" is in solution only,... Most nute's make an acidic solution as you know,... In your mix, aim for low 6's going in, and in-pot....
When you used the A8, how deep did you go, and was it near the center or edge? proximity matters here, because the immediate root zone is very dynamic for pH flux for the above mentioned reasons,... Go too deep and you're hitting saturated medium from the Autopot feed,... point is, there's a sweet spot to when to place the probe tip, and usually taking a reading at a couple different depths will give a better overall picture,...
The A8 isn't some high tech instrument mate, but for the $, and if used right and maintained, it's a reliable enough unit to give you reasonably accurate readings,... I recently did a slurry test of new soils I was trying out, using the pH meter vs. A8... they were within 0.2 of each other, and my unit is 3+ years old now..... try the same thing with yours! A basic slurry test is easy; do you have some of that medium mix around? ... take a 1/2cup of medium, add the same amount in RO/Di water, or low ppm water drinking water... add and stir, let sit for about 20min, then drain off liquid; let it settle out some, and test pH with meter.... with the A8, make up a small cup of medium and same water, moistened to usual levels and test,...

 

[lunarman]

:smoking: hey Lunar,... yes, I'm sure we talked about this before,.. in-pot pH can change quite a bit, especially in the root zone; there are lots of influencing factors at work in there... microbial activity, exudates from the roots, nutrient uptake, actual nute solution, etc. etc.,... what goes in at a certain pH doesn't necessarily stay that way, and AN's "self buffering" is in solution only,... Most nute's make an acidic solution as you know,... In your mix, aim for low 6's going in, and in-pot....
When you used the A8, how deep did you go, and was it near the center or edge? proximity matters here, because the immediate root zone is very dynamic for pH flux for the above mentioned reasons,... Go too deep and you're hitting saturated medium from the Autopot feed,... point is, there's a sweet spot to when to place the probe tip, and usually taking a reading at a couple different depths will give a better overall picture,...
The A8 isn't some high tech instrument mate, but for the $, and if used right and maintained, it's a reliable enough unit to give you reasonably accurate readings,... I recently did a slurry test of new soils I was trying out, using the pH meter vs. A8... they were within 0.2 of each other, and my unit is 3+ years old now..... try the same thing with yours! A basic slurry test is easy; do you have some of that medium mix around? ... take a 1/2cup of medium, add the same amount in RO/Di water, or low ppm water drinking water... add and stir, let sit for about 20min, then drain off liquid; let it settle out some, and test pH with meter.... with the A8, make up a small cup of medium and same water, moistened to usual levels and test,...

We have been over this before. Nice memory recall! Muscle memory? LOL.

I did a slurry test using my trusty calibrated pen. 1 part medium, 5 parts distilled water. I did this with young plants in autopots, and also pots I have precharged for the next run. PH value is 6.5. Just like my solution I feed them. I think my A8 might be unusable now. I rubbed her down good with various material. She reads 5. Slurry test is 6.5 like the solution. I'm going with the slurry.