high soil pH 7.8 and what I should do about it

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ffgrowery

New Member
Details about the grow:
  • 4x4x6 tent
  • 1000W HPS light, running %75, recently lowered to about 21" above plants.
  • AC Unit set to go off at 75
  • Temps have been between 68-78F (20-25C)
  • Humidity between 35%-60%
  • RO Water pH 6.0 with CalMag 1tbs/gallon. No neuts yet.
  • Recently transplanted from 4" pots into 3 gal. Air pots.
  • Soil is FFOF

I have recently re-potted my plants into 3 gallon air-pots, filled with FFOF soil. I have watered with pH 6.0 water, and let the runoff sit for a day. Once collected, the runoff tested pH 7.8! Before you ask, I'm using an electronic Oakton EcoTester, and I've recently calibrated it.
This worries me because I'm afraid that the actual soil pH is somewhere well above 8, and that it might cause nutrient lockout soon. The plants are looking pretty healthy, although some of the plants are significantly shorter than others, and are slightly more yellow.
Here's what I am thinking of doing. I am all for doing a flush in hopes of lowering the pH, but instead of wasting a ton of water, I'm thinking of collecting the runoff, lowering the runoff with pH down, and running it through again. Does anyone see a problem with this? I'm considering it might be good to recycle the runoff, and put all of the nutrients in the FFOF back in the soil, while lowering the pH.
Has anyone tried this? Would this work? I'm in Cali, and with the drought, I feel crappy simply wasting runoff water. I've also heard of people adding vinegar, or lemon juice to their water in hopes to raise the acidity. Any alternatives, or other solutions to this problem are welcome!
 
st0wandgrow

st0wandgrow

Well-Known Member
I wouldn't trust runoff as an accurate reflection of soil ph. *IF* your soil is in fact alkaline, you can simply add more sphagnum peat to it. Peat is very acidic and will lower the aggregate ph. You can pick up a 3cf bail of it at any Home Depot for $12.

Also, I wouldn't use the cal/mg anymore if your PH is that high. You're not helping matters by using it.
 
F

ffgrowery

New Member
How much does Cal-Mag raise the pH? I didn't realize it raised it by much. I've never heard of sphagnum peat. I'll check it out. How quickly does it lower the pH? Is this something that needs to be added in the mixing stage, or can you add it as a supplement to an existing grow?
 
Nullis

Nullis

Moderator
I don't even see how it got up that high with RO water... but a TABLESPOON of CalMag/gallon is what you are using? Sounds like too much.
 
rob333

rob333

Well-Known Member
do nothing about it lol leave it if it in soil i never do it and mine look fine few warped leaves but they are powering
 
rob333

rob333

Well-Known Member
when ur growing alot why bother u gunna loose grams but if ya gunna jew it and grow 1 well maybe look into it cause u want every inch of that plant to bud right ;)
 
F

ffgrowery

New Member
Wow thanks for all the replies. The general consensus that I'm getting here is that I shouldn't be testing the pH if my soil? I was under the impression that soil pH should be 6.5 and that to much higher or lower than that can cause nutrient lockout... I guess I should concentrate more on how the plants actually look, and not meddle with the details to much...
 
DonAlejandroVega

DonAlejandroVega

Well-Known Member
ffgrowery said:
Wow thanks for all the replies. The general consensus that I'm getting here is that I shouldn't be testing the pH if my soil? I was under the impression that soil pH should be 6.5 and that to much higher or lower than that can cause nutrient lockout... I guess I should concentrate more on how the plants actually look, and not meddle with the details to much...
Click to expand...
*DING DING DING*

make sure you start with buffered soil, and never look back at ph again (in soil).
 
Dr. Who

Dr. Who

Well-Known Member
That is correct.....
pH of the run off is just that,,,,the pH of the run off,,,,,,,NOT the soils !
If the soil is quality and your keeping you myco's or "living Bio's" alive or adding some back now and then with a "zyme" product when using synthetics. You shouldn't even bother with pHing.

Soil works to pH it's self. The living things IN the soil help balance the pH out to the plants needs.
Now then, when you water the pH goes up,,,,and as the soil dries back out, it goes back down...naturally!

Keep your soil healthy and simply forget about pHing it.
 
rob333

rob333

Well-Known Member
Dr. Who said:
That is correct.....
pH of the run off is just that,,,,the pH of the run off,,,,,,,NOT the soils !
If the soil is quality and your keeping you myco's or "living Bio's" alive or adding some back now and then with a "zyme" product when using synthetics. You shouldn't even bother with pHing.

Soil works to pH it's self. The living things IN the soil help balance the pH out to the plants needs.
Now then, when you water the pH goes up,,,,and as the soil dries back out, it goes back down...naturally!

Keep your soil healthy and simply forget about pHing it.
Click to expand...
i agree phing in soil can do more harm then good
 
Uncle Ben

Uncle Ben

Well-Known Member
Actually, trying to buffer soil's pH with adjusted water does no good. Soil is a powerful buffer. I've done experiments using drenches of water at 4.2 and 9.4 and the effect is temporary.
 
Uncle Ben

Uncle Ben

Well-Known Member
ffgrowery said:
Wow thanks for all the replies. The general consensus that I'm getting here is that I shouldn't be testing the pH if my soil? I was under the impression that soil pH should be 6.5 and that to much higher or lower than that can cause nutrient lockout... I guess I should concentrate more on how the plants actually look, and not meddle with the details to much...
Click to expand...
Yep, and identifying the countless myths presented at this website. Speaking of "consensus". Question them and all popular thought before deciding if it's correct. Most times it's not.

Good luck with that!
 
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Nullis

Nullis

Moderator
ffgrowery said:
Wow thanks for all the replies. The general consensus that I'm getting here is that I shouldn't be testing the pH if my soil? I was under the impression that soil pH should be 6.5 and that to much higher or lower than that can cause nutrient lockout... I guess I should concentrate more on how the plants actually look, and not meddle with the details to much...
Click to expand...
Soil pH isn't homogenous. It isn't like under 6.5 everything immediately locks out and oh no! A pH of 5.9 is fine. A pH of 7 is fine. A pH of 7.5 is more likely than not fine. Even if you had a pH pen, it isn't 100% accurate... and again, soil pH (and pH in the rhizosphere) isn't homogenous. pH is also temperature dependent (since acid dissociation/equilibrium constant (Kₐ) is temperature dependent).

Soil has cation exchange capacity, and thus itself has buffering capacity: resisting pH changes as UB described.
 
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