Indoor Weird soil PH issue (too high)

[Hexeract]

Hi Guys. I mixed some nice planting soil mixed with perlite. This soil alone works well and keeps proper ph. However this time i amended it with crab shell (20 grams per 1000 grams of soil) and kelp meal (also 20 to 1000). I also added azomite 1 tbp to 1000 grams of soil. I used distilled water to hydrate after the transplant.

A week later my plant had signs of phosphorus deficiency, splotchy purple/brown spots. I check the PH and it was very high, up around 8 maybe higher. I flushed the pot with several gallons, but the run off kept coming out around 8.0

I'm not sure what caused the PH spike. Crabshell is 6.0. I tested the kelp meal alone and it was also very low. The only thing with an alkaline PH is the azomite, but I don't think it's known to increase ph. I'm very confused, and not sure how to fix.

 

[GoAuto6]

Are you checking run off? or do you have a probe?

[h=2]Rough Calculation Guide:[/h] Here's some good info on ph.....
If your runoff pH is higher than your starting pH, use this equation to determine your soil pH:*
Soil pH = Runoff pH + Difference

If your runoff pH is lower than your starting pH, us this equation:
Soil pH = Runoff pH - Difference.

For example, say your the starting pH of your solution before it goes in is 6.5 and the pH of your runoff is 7.0. The difference is +0.5, so using the above equation:
Soil pH = 7.0 + 0.5*
Soil pH = 7.5

If your starting pH is 6.5 and your runoff is 6.0, your difference is -0.5 and using the above equation:
Soil pH = 6.0 - 0.5
Soil pH = 5.5

 

[Waira]

Hex'- ... Hmmm, I've not had experience with this stuff, so I'll ask around, and including recommendations for acidifying the soil rapidly, not weeks from now; Cervantes recommends using distilled vinegar, at 1tsp/gal, to drop appx. 1 pH point... Azomite-- indeed it's alkaline, but at 8.0. it's not that harsh, and the amount you put in isn't that much... So, some other possibilities should be explored meantime,... RO water has zero buffering capacity, since the mineral carbonates have been removed,...these help stabilize pH, in both acid and alkaline directions, up to a point,... Did you confirm the pH of that soil beforehand? Funky batches happen! Your pH meter-- properly calibrated, and nice and clean on the sensitive parts? :brow: ..that bulb can get hazed over with residues, interfering with accuracy,... The P defc. does follow, as around 8.0 it's get strongly restricted according to the charts I see,...but I'd like to see the leaves first to confirm it's P defc.,... can you post some please? :thumbs:
... As GA6 mentioned, a very good friend to have is a quality soil pH probe-- something that measures soil pH directly,... Accurate 8 makes a fine one,... I dislike the run-off method because I think there's too many potential sources of measurement error in this method,...

 

[GoAuto6]

humic acid works purdy quick to buffer.

 

[Hexeract]

Thanks for the info. I was checking runoff, but I'm going to get a probe to be more accurate.

I just transplanted them again into plain soil to avoid the craziness, they seem much happier.

I think the kelp meal needs to break down as compost before it can be used in the pot. It was really stinky when i dumped it out, i think since kelp holds lots of water is was overly wet and started to putrefy, the excessive bacteria probably was creating the alkaline environment.