I bought one of those cheap moisture/pH probes, and I'm confused

[TheFertilizer]

So I bought one of those cheap little Moisture/pH/Light probes, it was like 5 bucks so I figured it might be useful for the moisture part at least--I have a tendency to over-water. I also wanted to see what the pH of the soil was though so I was kind of looking forward to that, but it doesn't really work the way I thought it would, or maybe I just don't understand how pH works?

Okay so here's what happened, I opened it up, and stuck it into a tote of Happy Frog, and the pH read 2. Like really, 2... I knew Happy Frog was acidic but that seemed a little drastic. So realizing the soil in the tote was only slightly moist ( the meter confirmed that ), I stuck it into one of my pots that had just been recently watered. The moisture meter maxed out, and the pH read between 5.5-6.5 on all the plants. I didn't really put together that it was the moisture at this point, until I put it into a solo cup plant that didn't have a pot to get put into, and the pH on that was down to like 3, and the moisture level wasn't very high so I finally put 2 + 2 together and realized that it wouldn't work unless the soil was moist.

This morning, I wanted to see how much the moisture level had dropped in the plants over night. So I put the meter in, the moisture hasn't been touched, and just to see I switched to pH, and almost all the pots had dropped half a point to a full point over night! Even though the soil was still "WET" on the moisture scale...

So I decided to just get a solo cup and put some fresh soil from the tote in. It wasn't very wet, the pH was super low. So then I watered it, the pH of my tap is about 7.5-8.5. Once the soil was fully saturated, the pH read much closer to 6.

Is this how pH works? I mean, as a soil dries out, does the pH lower? I think I remember reading that somewhere, but now I can't find it to confirm. Or is this just a limitation of the tool, like maybe it needs to be at total moistness to get an accurate pH reading? Or maybe it's just a piece of garbage...

Thoughts?

 

[Nulife]

I'm honestly not sure about your question. But wanted to try to help, even though I have never seen that type of meter before ever. Maybe this might help until someone with more experience can shed more light. It's my understanding when testing ph, most people test the water going into the plant, and then they test the "run off" water that comes out of the plant after watering. So perhaps you should try these two methods. Basically you're testing the water that you're putting in the plant, and then you test the water coming out of the plant because you want to know the Ph around the root zone. The reason for knowing the ph around the root zone is so you can determine if the plant is capable of taking in the nutes that are in the water or if not using nutes you want to test to see if there is any root problems. Ph fluctuates with oxygen as well, I believe, which might also be the reason for the fluctuation not to mention there is less moisture because the plant is actually taking it in. You're testing the water not the moisture for ph.

 

[Justones]

Firstly I have a similar meter found at lowe$. People will break your balls about it so beware. But it is good for measuring moisture & giving an idea of Ph. Its better than nothing in my opinion.

You are correct the soil has to be wet for it to get a good read of Ph. The water you use will obviously effect Ph. I have natural spring water here myself. Also take several measurements around the plant if a big pot. I let mine sit for about 60 seconds in the soil to level out & see where it seems to rest.

I plan on buying a nicer meter later down the road. But i have so many wants on my list for the next grow that its not high on the list yet. The one I like has a way to calibrate it using set ph fluids as a control. Some people dont even use\like ph meters. For me being my first grow, hand mixed soil & individual nutrients added as needed. I felt it an important tool to have on hand. Just to see a little more on whats going on when diagnosing issues.

 

[TheFertilizer]

D'oh! I just realized I was reading the moisture scale while thinking that was pH! My soil in the tote is actually reading just under 7, not at 2 like I thought! So that makes a lot more sense now...

Also the scale goes the other way than I thought, so apparently they have gotten more alkaline since last night, not more acidic.