pH Adjustments - guide?

Basic Growing Info
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#1

Hi fellow growers…!

:microscope: I’d like to compile complete guide about pH adjustments in both hydro and organics. What are your experiences? Let’s try to get overview of latest opinions about this…

While it is probably very easy to adjust in hydro I know there are lot of reasoning and disagreement in what exactly use to adjust pH in organics. Some say that classic pH adjusting acids can kill beneficial bacteria, some can’t adjust in stable way. It is very confusing.

Myself in hydro I’m sticking to common approach:

Adjusting pH down in hydroponics

In general I aim for 5.5 but there is more broad range in between 5.5 and 6.5. Some hydroponic growers (it is said so about Netherland growers) aim for slightly lower pH about 5.2.

  • In vegetative stage: Nitric acid HNO3
  • In blooming stage: Phosphoric acid (mineral (inorganic) acid having the chemical formula H3PO4)

Of course you can switch the acids one for another with the same adjusting power, but it is better to use them as recommended. The reason is that leftovers after pH adjustment will be processed by the plant as fertilizer.

Nitrates in a form slowly assimilated by the plant and harmless to the flowering process.
Phosphates for flowering, but for healthy roots, lush foliage and harmonious growth too.

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#2

In organics, I’d really like to hear your opinions.

For example General hydroponics recommends their dry pH down instead of liquid pH down for organic schedule (e.g. GH BioSevia).

  • Liquid pH down contains phosphoric acid, citric acid.
  • GH dry pH down contains ammonium sulfate, citric acid and urea phosphate.

Is that really so crucial to use some particular pH adjuster for organics otherwise you can harm the natural equilibrium in your system? What are your opinions?

#3

In Aquaponics, I shoot for a pH range that floats between 6.4 and 6.8 (not static). I like it to float up and down as I find my plants respond in a positive way.

The organics within aquaponics naturally drop the pH over time, as plants uptake water, evaporation, and nitrification of ammonia. Infact, if I’m not careful, pH may drop too quickly, and if this happens, I’ve been known to use Potassium Hydroxide (pH up). I also use organic Calcium Sulfate. It really depends on what my systems lacking at the time my pH is too low. If I’m low on Calcium or Sulfur, I use Calcium Sulfate, but if I’m low on Potassium, I use Potassium Hydroxide.

Now that that’s said, I do use tap water to top off my system. My city tap water is very high in carbonates, which act as pH up. The carbonates in my tap are mostly Calcium base. Generally, once a week I top off my system which brings my pH from 6.4-ish to 6.8-ish, which is perfect for me.

https://youtu.be/zP1rUMyklyc
https://youtu.be/luXZXjKwXM4

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#4

in organics we dont have to worry about ph

#5

I disagree, however I’d like to hear your reasoning behind not monitoring PH.

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#6

Sure! I grows organics n’ whith natural mountain water ( pH 7-7’5), n’ I must use lemon juice or “vinagre”…

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#7

It’s a sport to fix PH swings in organics. It’s like growing athletes.

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#8

Hey guys,
I ran a thirty plant operation over the summer that was outdoors here in colorado and as organic as I could make it. We monitored pH very closely with readings for individual plants throughout the day using a blue handheld electronic reader that was a little frustrating but not terrible for getting readings. We aimed to maintain a pH a little under 6.5 by a method of largely trial and error. we had a tank that we would fill then pH the water, add pH down, cycle the water to mix it, then do it all over until you hit your mark.
That was yhe method and the liquid we used was from mad farmer (i think) and claimed to be organic. It tasted okay.
The result i got was actually a pretty resilient system that hits an equilibrium after a few weeks and is kinda tough to throw out of balance. The pH would cycle pretty naturally with raises after fertilizing and then drops with the rains. I wound up grabbing the wrong jug one day and putting pH up into the tank and then onto the plants and that was the most extreme spike which got up to 6.7 or so. So after i realized what i had done and the small result i was a little less cautious about pH measurements and didnt have a problem.
I guess my opinion is that its more about the ecosystem you build below ground and less about the specific contents of the product.

#9

I think the point is to setup your soil so it has enough calcium in it without it going alkaline. Colorado soils tend to be alkaline due to higher carbonate content. You can test for free lime with a simple test. Microbe friendly soils do enhance the ability of the plants to withstand a wider PH range, and soils high in organic matter tend to be naturally acidic. Microbes also act as chelating agents, so if PH does go out of spec, you have a wider range of macro/micro nutrient absorption.

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#10

Cross-linking relevant topics


More topics under #ph-control tag.

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#11

Hey guys, one of the most important factors of this topic is water type.

Tap
Well
R.O or distilled

Depending on the water type, the alkalinity or buffer will be different. Using nitric or phosphoric acid with R.o can be a nightmare if you don’t buffer the water. It also directly influences the amount of acid required.

****please remember that concentrated acid can be dangerous. I have a experienced grower friend who poured acid into a plastic soda bottle to go pour into the rez. as he was walking the acid ate through the bottle cutting it in half. the bottom half fell and when it hit the ground it splashed up and hit him on the face. the BEST RULE FOR WORKING WITH ACID IS “AAA” ALWAYS ADD ACID. never add water to concentrated acid.

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#12

Ive been using 1 mil white distilled vineger per litre of 7 ish spring water, with some fairly good results.
I dont have a ph meter and grow soiless promix hp seems to work.

#13

I use 98% sulphuric acid and lab grade potassium hydroxide granules for PH. Industrial I know but I need milligrams of it. During flowering I add humic acid and fulvic, which are both reasonably acidic so the sulphuric is not often required. My reason for this is that it makes getting my res to the right PH a breeze. I know exactly how much I need to get it spot on and just weigh it all with the nutes. 5.8 is my target in both coco and dwc. I let it vary a bit more in dwc.

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