pH sensor for soil

Hey guys,

I found a few topics about measuring the pH value of water (or other fluids) but I didn't find a solution for measuring the pH value of soil. Does anyone know a sensor (module) and can recommend one?

Best regards
Stefan

My school time is some year behind me but I think to remember that a pH value is only defined for fluids. Can solids have a pH value?

I guess what you mean is the pH value a lab returns you if you send a sample. That's not my field but as far as I know that involves putting the sample in some water and then measuring the pH value of that water. I'm not aware of a sensor that is able to provide such a value.

The only PH soil analysis I have heard about would be this:

https://www.analog.com/media/en/reference-design-documentation/reference-designs/CN0398.pdf

That should give you a starting point.

Ron

No sensor that you can just jam into the ground and get a usable reading from.

pylon:
My school time is some year behind me but I think to remember that a pH value is only defined for fluids. Can solids have a pH value?

Well, its perfectly well defined as a logarithmic function of the concentration of H+ ions, concentration is nothing to do with the state of matter. However in common use pH is defined from the concentration of aqueous H+ ions (really H3O+ ions).

In soil science there's probably a particular definition used for soil pH, and maybe several different ones,
probably related to the amount of alkaline minerals present.

Quite interesting points, thank you. Actually my school time is also looong gone and I don't have any clue about pH values anymore but I'd like to work with it again to improve my plant-project.
Thank you for the answers so far, I'll start to work with them now. If someone have anymore information, don't hesitate to write them, I can't have too many information. :slight_smile:

I'm thinking about disassembling one of these (or similar) and adding a hi-z amplifier to read the analog output and send it amplified/buffered to the Arduino...
https://www.homedepot.com/p/pH-Meter-HpHMeter/204345613

You are cordially invited to do an Internet search! Woot! Woot! Using the wondrous words "arduino soil ph", you will become a winner!