PH A Basic explanation

  • Thread starter Aqua Man
  • Start date
  • Tagged users None
Aqua Man

Aqua Man

Staff member
Supporter
I have not had a grow in pro mix hp or ocean forest that ever ran out of lime (or oyster shell) even with a 12 week flowering plant.

If ph got low or high it was grower error. It is almost always nutrient or water stress related.
Yes this. If you have an issue its usually because of an inadequate water source or grower error.
 
Glassdub

Glassdub

Yes this. If you have an issue its usually because of an inadequate water source or grower error.
Tell me my error, I was watering only after drying (If not under-watering) & in the the end my run off pH was 5-5.3 was not over feeding, like a quarter of recommended doses yet huge build ups due to lack of uptake, the water was acid & over time drove the medium down over time marring that uptake as far as I can tell.
 
Aqua Man

Aqua Man

Staff member
Supporter
Tell me my error, I was watering only after drying (If not under-watering) & in the the end my run off pH was 5-5.3 was not over feeding, like a quarter of recommended doses yet huge build ups due to lack of uptake, the water was acid & over time drove the medium down over time marring that uptake as far as I can tell.
There are lots of factors at play so I cant tell you exactly your cause. But let me point this out to you before listing some. We almost always PH our nutrients down correct?

So if your soil PH was low then adding you PH down would not solve your issue. And it was infact grower error not ph adjustment.

Just because you feed at low doses does not mean you cannot have a buildup of nutrients and that usually causes low soil PH.

Ferts with ammonium nitrogen lower soil PH because the plants release h+ ions in the process used to uptake it.

Underwatering can also cause this... as you indicated. This is because as the soil dries nutrients become more concentrated and nutrients are generally acidic

Iron will also lower soil PH and to much cal mag thats usually is in nitrate form with iron added can also play a role.

The amount of bacteria respiration and air exchange capacity of the soil can affect PH.

Typically if you have a PH drop in your prebuffered soil such as promix its nutrient related and if you have a rise in soil PH it usually water source related.
 
Last edited:
Aqua Man

Aqua Man

Staff member
Supporter
Tell me my error, I was watering only after drying (If not under-watering) & in the the end my run off pH was 5-5.3 was not over feeding, like a quarter of recommended doses yet huge build ups due to lack of uptake, the water was acid & over time drove the medium down over time marring that uptake as far as I can tell.
If I'm going to hazard a guess its that you did not give adequate runoff. Nutrients need to be dissolved in water for the plant to be able to uptake them. Because of this when you give good runoff they can be washed out of the soil. If you do not give good runoff they stay in the soil and build up becoming more concentrated after each watering. This leads to PH and salinity issues which prevent the plant from uptake as it should.

Its not at all the plant didn't take them up so they built up... its that they were over fed.
 
Glassdub

Glassdub

If I'm going to hazard a guess its that you did not give adequate runoff. Nutrients need to be dissolved in water for the plant to be able to uptake them. Because of this when you give good runoff they can be washed out of the soil. If you do not give good runoff they stay in the soil and build up becoming more concentrated after each watering. This leads to PH and salinity issues which prevent the plant from uptake as it should.

Its not at all the plant didn't take them up so they built up... its that they were over fed.
This is true & this is why I'm moving to 5 gal terracotta pots this run over fabric, as I had a hell of a time getting runoff on them comparatively to the 2 liter (partly because the trays were too tight.), so I didn't bother upon up-potting until the end, right now I'm running a bit high at 6.5-6.6 aiming to get that down.
 
Aqua Man

Aqua Man

Staff member
Supporter
This is true & this is why I'm moving to 5 gal terracotta pots this run over fabric, as I had a hell of a time getting runoff on them comparatively to the 2 liter (partly because the trays were too tight.), so I didn't bother upon up-potting until the end, right now I'm running a bit high at 6.5-6.6 aiming to get that down.
Tiny amount of ammonium based nitrogen should help. Just be careful on how much it can create tox easily and would not go over 10% in soil. In hydro 5% or less preferably
 
MIMedGrower

MIMedGrower

There are lots of factors at play so I cant tell you exactly your cause. But let me point this out to you before listing some. We almost always PH our nutrients down correct?

So if your soil PH was low then adding you PH down would not solve your issue. And it was infact grower error not ph adjustment.

Just because you feed at low doses does not mean you cannot have a buildup of nutrients and that usually causes low soil PH.

Ferts with ammonium nitrogen lower soil PH because the plants release h+ ions in the process used to uptake it.

Underwatering can also cause this... as you indicated. This is because as the soil dries nutrients become more concentrated and nutrients are generally acidic

Iron will also lower soil PH and to much cal mag thats usually is in nitrate form with iron added can also play a role.

The amount of bacteria respiration and air exchange capacity of the soil can affect PH.

Typically if you have a PH drop in your prebuffered soil such as promix its nutrient related and if you have a rise in soil PH it usually water source related.

Nice list. Heres one to add. Promix takes a week out of the bale usually watered in before the ph raises above 4-5 ph while waiting for the lime to activate. It also has an included nutrient charge. So if you feed early just like with ocean forest or any amended soil your runoff may com back acidic and with an unusually high ppm.

You can flush this charge out easy or just wait longer to start feeding. Even when i have done this. Corrected the pro mix has always risen back to about 6.2 ph.
 
Aqua Man

Aqua Man

Staff member
Supporter
Nice list. Heres one to add. Promix takes a week out of the bale usually watered in before the ph raises above 4-5 ph while waiting for the lime to activate. It also has an included nutrient charge. So if you feed early just like with ocean forest or any amended soil your runoff may com back acidic and with an unusually high ppm.

You can flush this charge out easy or just wait longer to start feeding. Even when i have done this. Corrected the pro mix has always risen back to about 6.2 ph.
Probably a very common thing to try to adjust. Add more lime then stuck with trying to bring down a high PH soil.
 
MIMedGrower

MIMedGrower

I hope i never have to deal with that

I hope for you too but they are fast becoming a weed epidemic like spider mites did in colorado when they legalized. I am positive they came from the grow store.

I go to the feed store for bales now. No more weed industry anything is my plan.
 
Top Bottom