Do we need to pH adjust our nutrient solutions?

[Keffka]

No worries Kefka! There are two ways to check the pH of your medium: slurry test and the pour through method.

Here's the info on slurry testing, and it requires distilled water and a calibrated pH meter to work, and this is how to do it:

• Take samples from a few different places where there are roots (dig down a bit rather than just use the top - I often stick a spoon down the outside edge of the pot to grab some from there as well)

• Add an equivalent amount of distilled water as grams of soil (10 grams of soil, add 10ml water). If that doesn't make a slurry, use enough distilled water to make a stirrable-but-thick slurry.

• Stir it up, wait 15 minutes, stir again. Do that for an hour and then put your calibrated pH stick in the water. That's the pH of your medium.


The pour-through test is done this way:
1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving
2. after container has drained for one hour, place a saucer under the container
3. pour enough distilled (DI) water on the surface of the container to get 50 mL (1.5 fluid ounces) of leachate to come out of the bottom of the container (Table 1)
4. collect leachate for pH testing
5. calibrate pH meter
6. measure pH of samples

AWESOME! Man.. every interaction I have here makes me love this place that much more.. Thank you for the detailed response!

 

[Cycosis101]

OK, I've spent the better part of the day reading through this whole thread and related articles to get a better understanding of my situation.

Let's start simple. I'm new to promix HP myco, coming from coco,i used everything in coco that I've used in promix. I'm 4 weeks into flower on some Ethos Mandarin Skittlez.

I use RO water. I use Jack's 3-2-1 in those ratios, I use armor si. I use calmag.
I'm growing in autopots(I think this is important).

I picked up promix on my friends recommendation, I treated it like coco. I used pH down to adjust my 10gallons of nutrient water to 5.8ph 2.7EC(including calmag, armor si, nutes).

I've had what looks to be progressively worse pH issues, all while pH in trays and res stayed 5.8-6ph.

I got fed up, flushed media with 2 gallons RO water, measured runoff, 4.5ph. Too low. Continued flushing till below 2 ec, and then circulated from tray to top of plant nute water for 20 minutes, incrementally adding GH pH up until settled at 5.8ph and vaccumed trays and ran more 5.8ph nute water through the top, measured run off, 5.8ph.

I'm using neutral alkaline RO water, my fertilizers are potential basic, for all intents and purposes I should have, if anything, seen raised pH in the media. This leads me to believe that dumping 40-50ML of pH down into my res has built up in my autopot trays/media over time throwing off balance, because I do not drain to waste.

Is this an accurate assumption to make? To prevent in the future I plan on not PHing my res. Is my recirculating phup into the media a fix for this for the last few weeks of flower or am I doomed? What would be a better way to adjust medium pH in the future?

 

[InTheShed]

OK, I've spent the better part of the day reading through this whole thread and related articles to get a better understanding of my situation.

Let's start simple. I'm new to promix HP myco, coming from coco,i used everything in coco that I've used in promix. I'm 4 weeks into flower on some Ethos Mandarin Skittlez.

I use RO water. I use Jack's 3-2-1 in those ratios, I use armor si. I use calmag.
I'm growing in autopots(I think this is important).

I picked up promix on my friends recommendation, I treated it like coco. I used pH down to adjust my 10gallons of nutrient water to 5.8ph 2.7EC(including calmag, armor si, nutes).

I've had what looks to be progressively worse pH issues, all while pH in trays and res stayed 5.8-6ph.

I got fed up, flushed media with 2 gallons RO water, measured runoff, 4.5ph. Too low. Continued flushing till below 2 ec, and then circulated from tray to top of plant nute water for 20 minutes, incrementally adding GH pH up until settled at 5.8ph and vaccumed trays and ran more 5.8ph nute water through the top, measured run off, 5.8ph.

I'm using neutral alkaline RO water, my fertilizers are potential basic, for all intents and purposes I should have, if anything, seen raised pH in the media. This leads me to believe that dumping 40-50ML of pH down into my res has built up in my autopot trays/media over time throwing off balance, because I do not drain to waste.

Is this an accurate assumption to make? To prevent in the future I plan on not PHing my res. Is my recirculating phup into the media a fix for this for the last few weeks of flower or am I doomed? What would be a better way to adjust medium pH in the future?

Well that's a lot to unpack on what it not a grow journal!

First off, ProMix HP is not coco and doesn't need to be treated as such in terms of pH of your nutes. The manufacturer says so. That said, there's no harm in setting your nutes at 5.8 if that's what makes you comfortable.

Second, once you vary from a manufacturers feeding schedule you won't know if you're giving the plants what they need without using some form of nutrient calculator. Armor Si is 0-0-4 and calmag can range from 0-0-0 to 13-0-0, so they can change the percentages by large amounts.

I don't have any experience growing in autopots and I'm not aware of folks using ProMix in bottom water situations, but that doesn't mean it can't be done. I suggest tagging someone like ReservoirDog or Azimuth into your grow journal so they can offer you advice on that.

Hope that helps!

 

[KeithLemon]

Greetings all! I recently had a running email conversation with the "Grower Services & Product Development Director" at ProMix (aka Premier Tech). I began the conversation by posting a question on their website, asking if I should be treating ProMix HP as soil or soil-less when mixing nutrients.

[Please note that we were not discussing hydro growing. This conversation does not apply to hydro.]

As we have all been taught, the pH range for nutrients is different for soil and soil-less media and I had been using the soil range in my ProMix and wanted to double check. His response left me confused, as he answered the question by giving me the ideal pH range for mineral soil and soil-less growing media. He did not address my question of the correct pH of the nutrient mix.

We went back and forth for a few days and his answers always referred to the pH of the media and not what we were pouring into the media. I kept trying to narrow my question and he continued in the same vein. I contained my exasperation so as not to short circuit the chain.

At one point he said this:
"It is the potential acidity or basicity of the fertilizer chemistry and the alkalinity content of your water that affects the pH of the growing medium. For the fertilizers, it is called ‘potential’ since it is determined by the chemistry and the quantity of fertilizer nutrients that are applied and the ‘potential’ they have to interact with the plant root system and influence the pH of the growing medium up or down."

All related to the medium. And the interesting use of the word "potential," but again ended it by talking about moving the pH of the growing medium.

Rather than bore you with the all back and forth, I will post this summary that I sent him in one of our last emails. He approved of this summary (italics mine):

1. Ideal pH range for mineral soil is 6.0-6.5. Soil-less growing media, such as PRO-MIX, have an ideal pH range of 5.5-6.0.

2. However, pH of nutrient water is irrelevant to the pH of any soil or growing media. It is the alkalinity of nutrient water and the potential acidity/basicity of the fertilizer(s) that influence the pH of the growing medium and root zone. For example, if the alkalinity of nutrient water is moderate or high, pH of growing medium will rise over time.

a. Plant roots are electrically charged and must maintain a neutral balance.​

b. For ammonium nitrogen (NH4) fertilizers, plants release of hydrogen ions to take up NH4. Hydrogen released is essentially acid and this drives pH down.​

c. For nitrate (NO3) form of nitrogen in fertilizers, plant exchange hydroxyl ions for NO3 uptake, which causes growing medium pH to rise.​

d. Alkalinity (CACO3) is essentially dissolved limestone. The higher the alkalinity of water, the greater tendency to raise pH of growing medium over time.​

3. It is more important to keep track of the pH of the growing medium than the pH of the nutrient solution we feed the plants.

And at the bottom of that summary I added one last direct question:
"If I’m growing in ProMix HP and I mix up the nutrient solution and it reads 7.4 pH, it is not necessary for me to adjust that number down using phosphoric acid or the like. I can pour it into the pot at 7.4 and my plants will be able to uptake those nutrients?"

His response was a direct "Yes."



-----------------------------------
We had discussions on the correct way to check the pH of soil or soil-less medium (none involved checking our nute runoff). I'll post the various methods he sent me in a different thread and post a link here. I don't want to distract from the info above!

This is a lot to take in half of it I do not understand, but we should be checking our soil PH as well as our nutrients PH. One affects the other. Did I get it

 

[InTheShed]

we should be checking our soil PH as well as our nutrients PH. One affects the other.

If you think you have a soil/ProMix pH problem, a slurry or pour-through test could be in order to tell you if your medium has drifted far from factory specs. You do not need to pH adjust your nutrients in soil or ProMix.

 

[SCD]

I’m in Promix and haven’t once adjusted pH of the solution this season. The plants seem to be fine with it

 

[Cycosis101]

Okay sorry for info dump. I understand now not to treat it as coco. My pour through test showed 4.5ph. So I setup a pump to recirculated water from my autopot trays back into the pot and added GH pH up until the run through settled at 5.8ph in the medium. My suspicion is that because I'm not doing drain to waste, the pH down I was needlessly adding just got "trapped" in the media, making the included lime buffer not properly able to.. buffer. That makes sense?

Right now I'm just trying to understand what caused the pH to be so low in the medium. Jack's part A and part B are both alkaline, as is armor si.

Also I'm specifically following Koots 3-2-1 nutrient program, but it's all based off of greengenes garden (YouTube) grows where he walks through tons of nutrient calculations, I've successfully grown with this regiment in coco, I wanted to switch to promix because it's much more airy.

 

[InTheShed]

My pour through test showed 4.5ph

Using the actual pour-through test method?

Steps for the PourThru method:

1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving
2. after container has drained for one hour, place a saucer under the container
3. pour enough distilled (DI) water on the surface of the container to get 50 mL (1.5 fluid ounces) of leachate to come out of the bottom of the container (Table 1 below)
4. collect leachate for pH testing
5. calibrate pH meter
6. measure pH of sample

If you didn't do that, you didn't measure the pH of your ProMix. And since you can't get to the bottom of the pot because of the res, I suggest a slurry test. It also requires distilled water and a calibrated pH meter to work, and this is how to do it:

• Take samples from a few different places where there are roots (dig down a bit rather than just use the top - I often stick a spoon down the outside edge of the pot to grab some from there as well)
• Add an equivalent amount of distilled water as grams of soil (10 grams of soil, add 10ml water). If that doesn't make a slurry, use enough distilled water to make a stirrable-but-thick slurry.
• Stir it up, wait 15 minutes, stir again. Do that for an hour and then put your calibrated pH stick in the water. That's the pH of your medium.

Soil should be 6.3-6.8 and ProMix should be 5.4-5.9

Right now I'm just trying to understand what caused the pH to be so low in the medium. Jack's part A and part B are both alkaline, as is armor si.

It's not the alkalinity of the nutes, it's the source of the nitrogen. Ammonical nitrogen will lower the pH of the substrate over time and nitrate nitrogen will raise it.

I've successfully grown with this regiment in coco, I wanted to switch to promix because it's much more airy.

ProMix may seem more fluffy but it retains water longer than coco, which can need to be watered up to 3x/day in full flower.

 

[Cycosis101]

Okay, I will do the slurry test in a while for the most accurate up to date result.

I've pulled the nutrient sheets for everything I've put in my res, and the ONLY THING that has ammonical nitrogen is the calcium nitrate I use, and it's miniscule. It's 14.5% nitrate and 1% ammonical. Jack's 5-12-26 is 5% nitrate nitrogen and epsom salts contain no nitrogen, armor si contains no nitrogen and botanicals cal mag has 2% nitrate nitrogen.

So in total I have a combined 21.5% nitrate nitrogen and 1% ammonical nitrogen.

 

[InTheShed]

Okay, I will do the slurry test in a while for the most accurate up to date result.

I've pulled the nutrient sheets for everything I've put in my res, and the ONLY THING that has ammonical nitrogen is the calcium nitrate I use, and it's miniscule. It's 14.5% nitrate and 1% ammonical. Jack's 5-12-26 is 5% nitrate nitrogen and epsom salts contain no nitrogen, armor si contains no nitrogen and botanicals cal mag has 2% nitrate nitrogen.

So in total I have a combined 21.5% nitrate nitrogen and 1% ammonical nitrogen.

I'm guessing that pour-through test wasn't done to spec, so the slurry test will give you a better picture.

 

[Cycosis101]

And again my water source is RO with like 11tds and Jack's 5-12-26 has a 170lb per ton basic potential, ie if any pH drift it should have been increased medium pH afaik

 

[CaptainLucky]

Using the actual pour-through test method?

Steps for the PourThru method:

1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving
2. after container has drained for one hour, place a saucer under the container
3. pour enough distilled (DI) water on the surface of the container to get 50 mL (1.5 fluid ounces) of leachate to come out of the bottom of the container (Table 1 below)
4. collect leachate for pH testing
5. calibrate pH meter
6. measure pH of sample

If you didn't do that, you didn't measure the pH of your ProMix. And since you can't get to the bottom of the pot because of the res, I suggest a slurry test. It also requires distilled water and a calibrated pH meter to work, and this is how to do it:

• Take samples from a few different places where there are roots (dig down a bit rather than just use the top - I often stick a spoon down the outside edge of the pot to grab some from there as well)
• Add an equivalent amount of distilled water as grams of soil (10 grams of soil, add 10ml water). If that doesn't make a slurry, use enough distilled water to make a stirrable-but-thick slurry.
• Stir it up, wait 15 minutes, stir again. Do that for an hour and then put your calibrated pH stick in the water. That's the pH of your medium.

Soil should be 6.3-6.8 and ProMix should be 5.4-5.9



It's not the alkalinity of the nutes, it's the source of the nitrogen. Ammonical nitrogen will lower the pH of the substrate over time and nitrate nitrogen will raise it.

ProMix may seem more fluffy but it retains water longer than coco, which can need to be watered up to 3x/day in full flower.

Super explanation, very impressive bro.

 

[Cycosis101]

Okay, I pH'd my bluelab pen, pulled 3-4 different spots half through the substrate and did 10grams soil to about 15grams distilled water and stirred and mixed every 15 minutes for an hour, then took my pH reading. 5.5pH. Again this is after creating a constant circulation loop and adding ph up into my flood tray to be circulated through the medium for about an hour until I hit 5.8ph.
I mixed a fresh batch of nute water. 12 Gallons of Jacks 321 @100% strength.
That's 3.6g/gal of 5-12-26 Jacks Hydro Part A, 2.4g/gal of 15.5-0-0 Calcium Nitrate, 1.2g/gal of epsom salts.
Total EC is 2.2 which is on the money. I didn't add anything else. I'm going to let it sit overnight and bubble.

 

[InTheShed]

Okay, I pH'd my bluelab pen, pulled 3-4 different spots half through the substrate and did 10grams soil to about 15grams distilled water and stirred and mixed every 15 minutes for an hour, then took my pH reading. 5.5pH

This is exactly where it should be, so what you don't have is a pH problem!

 

[Cycosis101]

I understand what you're saying, but last night it was 4.5ph with the pour through method. So I added 2 liters of nute water, which was just enough to flood the entire top of the pot. I then started adding general hydroponic pH to the top of the substrate, pouring probably 30+ ML of pH up incrementally over an hour long period and let it circulate through until the ph pen read out 5.8ph.

My concern is that this is a bandaid and substrate ph will be an issue again, and that I DO NOT KNOW what caused my pro-mix to be so low in ph in the first place.

 

[Cycosis101]

If it drifts down again, how do you recommend I fix it? Make a dolomitic limestone slurry and do my same flooding circulation method?

 

[InTheShed]

Before it was 4.5ph pour through method.

Maybe I'm missing something but was your first an test actual pour through test as I posted above? Measuring regular pH runoff is meaningless no matter how many times you circulate through.

If it drifts down again, how do you recommend I fix it? Make a dolomitic limestone slurry and water that into the media?

I don't think it actually drifted down at all. I recommend that you stop checking runoff pH since it doesn't even mean anything in coco, where pH matters.

Start a grow journal and post the link here and let's move this discussion there.

 

[Cycosis101]

Yes, I did the pour through method like you explained back in this thread yesterday afternoon before doing anything, and then didn't feel confident in my method of fixing my substrate ph and read through this whole thread at lunch today to see if I missed anything about fixing already messed up medium that has plants growing. There was virtually no information on how to ACTUALLY do anything in regards to changing substrate ph in this thread.

 

[Cycosis101]

I don't think it actually drifted down at all. I recommend that you stop checking runoff pH since it doesn't even mean anything in coco, where pH matters.

I normally NEVER measure runoff ph... because I do not have run off I'm in trays. The only reason there was runoff was due to the pour through method.

 

[InTheShed]

There was virtually no information on how to ACTUALLY do anything in regards to changing substrate ph in this thread.

That's not what the subject of the thread is...that's what grow journals are for!

I normally NEVER measure runoff ph... because I do not have run off I'm in trays. The only reason there was runoff was due to the pour through method.

So you waterd with your regular nutes, waited an hour, and added just enough distilled water to get 1.5 ounces of water? I don't remember that part.

Waiting for your journal link...