jacks, silica, and pH madness

[kushtrees]

Ive been using the jacks, cal nitrate, epsom salt combo for awhile now, but I have been battling large pH swings for awhile, its gotten so bad that I will pH the res to 5.6 and in 24 hours its up to 6.2 (DTW btw).

I am using the 3-2-1 ratio at 60% with 2.5ml/ gal dynagrow protek, as well as fulpower and root excel (but I doubt those last 2 are causing the pH swings); this comes out to 1.2 EC. Run off is at 1.1 EC and currently at a pH of 7.3....

I am going to loose the silica next week to see if I can get the pH in the res to stabilize, I also plan to flush the medium really well to try and get a clean slate in there so to speak. After that, assuming that things stabilize and the plants start to look a little better, I plan to bring back the silica at 1.25ml/ gal and see if that will keep a steady pH.

Has anyone else experienced massive pH swings when using silica and Jacks? My guess is that the lower than usual EC with the normal dose of silica is the culprit here, but I wanted to see if anyone else has any ideas or has seen this before.

PS I am using 2 kinds of chow, 1 group is in 80/20 growstones coco, the other is in 80/20 growstones SS4.

 

[pugliese63]

I've used the 3-2-1 combo with Jack's for a long time. I grow in a chow mix of 50/50 rockwool and hydroton. The Protekt silica supplement is probably causing your pH swing, its very alkaline. Jack's has more than enough silica own it own. I can attest to this as my branches are thicker and stronger than ever.

Drop the Protekt and I think you'll see your pH will stabilize. It's actually ideal to let the pH swing upwards over a period of a couple of days, (i.e. starting pH is 5.8 and should rise to about 6.2 over a reasonable period of time, 48 to 72 hours). This allows for maximum nutrient absorption.

Hope this was helpful.

 

[midwestdensies]

I never stress res ph. I let it swing between 5.3-6.3 for uptake of all minerals. More feeds =more control. Dont stress that perfect ph it doesnt exist. Vegging and flowering like diff ph. Look at ph uptake chart to see what im talkig about. Change up intervals of feed possibly with more but less water. Hope this makes sense or helps

 

[dizzlekush]

Ive been using the jacks, cal nitrate, epsom salt combo for awhile now, but I have been battling large pH swings for awhile, its gotten so bad that I will pH the res to 5.6 and in 24 hours its up to 6.2 (DTW btw).

I am using the 3-2-1 ratio at 60% with 2.5ml/ gal dynagrow protek, as well as fulpower and root excel (but I doubt those last 2 are causing the pH swings); this comes out to 1.2 EC. Run off is at 1.1 EC and currently at a pH of 7.3....

I am going to loose the silica next week to see if I can get the pH in the res to stabilize, I also plan to flush the medium really well to try and get a clean slate in there so to speak. After that, assuming that things stabilize and the plants start to look a little better, I plan to bring back the silica at 1.25ml/ gal and see if that will keep a steady pH.

Has anyone else experienced massive pH swings when using silica and Jacks? My guess is that the lower than usual EC with the normal dose of silica is the culprit here, but I wanted to see if anyone else has any ideas or has seen this before.

PS I am using 2 kinds of chow, 1 group is in 80/20 growstones coco, the other is in 80/20 growstones SS4.

Alright first off, some questions

What is your water quality parameters (namely its E.C. and hardness [alkalinity quantified as mg/L CaCO3 would be optimal])?
What do you use for your pH adjusters and how often do you use them?

I can think of 3 things you can change to improve pH control regardless of how you answer the above questions. The first one you already figured out, cut out some of you Si, but i wouldn't cut out ALL of it. IIRC the application rate you're using (2.5ml/gallon) is ~29ppm Si, which is more than you need and is definitely causing some pH issues. Dr. Bruce Bugbee suggests ~3ppm Si (0.1 mM) as an average for recirculating hydroponic crops specifically . That's probably perfect for cannabis as well since all tissue analyses of cannabis i've seen has shown Si levels in the same range as Fe. Basically i would suggest starting of at 1/10 the strength you we're using (so 2.5ml per 10 gallons) to achieve that 3ppm and see how it goes from there.

The second thing you could do is add a little NH4. Ammonium Sulfate and Ammonium Di-Basic Phosphate (DAP) are your best choices there. When the plant absorbs NO3 it raises pH, when it absorbs NH4 it lowers the pH, so lessening the NO3:NH4 ratio has a pH buffering effect. I could really go into details on how to tweak your nute profile to be more optimal for your plants, but idk if you're interested in the topic or what i have to offer. I like Jacks Professional (I use it myself), but im not a fan of the 3-2-1 usage of it thats gotten popular amongst its users. Its works just as well as most other nutes that are orders of magnitude more expensive than it, its just not optimal IMO.

The third thing is to add more P to the mix (MKP, MAP or DAP). Using DAP would be killing 2 birds with one stone since it adds significant amounts of both P and NH4. P in solution has a light buffering capacity. Its not a huge buffering effect, but it does exist, and the more you use, the greater the pH buffering is. Not to get into a history lesson but thats the reason the "Lucas Formula" was made and originally popularized. I would not suggest using this during the first 2 weeks of bloom or if plant height is a huge issue as it tends to cause increased plant height, but not increased growth rates.

There are also pH buffering products like Amberlite resins and MES but i have a feeling that that's not the kind of stuff you're likely to try, since i've never even heard of cannabis growers knowingly using them.

Here's the Bugbee article i mentioned earlier, i think you might find it very informative. Ive re-read this article many times myself.

Principles of Nutrient Management in Recirculating Hydroponic Culture
Bruce Bugbee
http://www.usu.edu/cpl/research_hydroponics3.htm

 

[dizzlekush]

Jack's has more than enough silica own it own. I can attest to this as my branches are thicker and stronger than ever.

Jacks has no Si by itself, the improved branch strength you have is most likely from the increased amount of Ca you're providing to your plants compared to other formulas. Understandable how one could interpret that as Si.

 

[Capulator]

dizzlekush always dropping the knowledge. love it.

 

[Capulator]

Jacks has no Si by itself, the improved branch strength you have is most likely from the increased amount of Ca you're providing to your plants compared to other formulas. Understandable how one could interpret that as Si.

this is a huge threadjack, but if I wanted to make a gallon of 3.5 mM K solution, would I add 0.5273 grams of K to a 1 gallon jug and fill it up with water?

Just trying to wrap my head around the math of things.

 

[dizzlekush]

this is a huge threadjack, but if I wanted to make a gallon of 3.5 mM K solution, would I add 0.5273 grams of K to a 1 gallon jug and fill it up with water?

Just trying to wrap my head around the math of things.

A 3.5mM K solution is ~136.5ppm K. Out of curiosity, what were you reading that mentioned the 3.5mM K solution? PM me plz, to not completely jack thread.

 

[pugliese63]

Jacks has no Si by itself, the improved branch strength you have is most likely from the increased amount of Ca you're providing to your plants compared to other formulas. Understandable how one could interpret that as Si.

Thanks for the info. I know I haven't seen any physical reason to add silica.

 

[kushtrees]

Thanks for all the responses guys. I do not usually stress over pH, but my res keeps floating to 6.4 in a day and the runoff is just way too high. The plans are visibly stressed. I usually (with the nutes i used to use) start the res off at 5.8 let it go up to 6.1 or so and adjust down to 5.8.

Great article dizzle, it was a good read.

I currently use RO water. I had read that 25-50 ppms of silica was what you wanted. 3ppms is much much lower, but I will definitely be trying 3ppms. I'm very into the less is more philosophy these day, especially with nutes.

Thanks for the help everyone

 

[ttystikk]

I run .5-1ml/gal of protekt per gallon from veg thru peak bloom. If anything, my pH has been a bit low lately.

 

[cctt]

I could really go into details on how to tweak your nute profile to be more optimal for your plants, but idk if you're interested in the topic or what i have to offer. I like Jacks Professional (I use it myself), but im not a fan of the 3-2-1 usage of it thats gotten popular amongst its users. Its works just as well as most other nutes that are orders of magnitude more expensive than it, its just not optimal IMO.
http://www.usu.edu/cpl/research_hydroponics3.htm

Your link was a good read, though it's quite specific to recirculating systems, while OP mentions running DTW.

I'm also interested in your opinion on how to use Jack's Pro to create an optimally balanced nutrient profile for cannabis. Please share.

 

[dizzlekush]

I currently use RO water. I had read that 25-50 ppms of silica was what you wanted. 3ppms is much much lower, but I will definitely be trying 3ppms. I'm very into the less is more philosophy these day, especially with nutes

Lol. im a stoner, i thought it said your were running RDWC instead of DTW. I use DTW as well and use ~15ppm Si myself. But i have enough AgSil16H to last til i die and @ 15ppm it doesnt give me any pH/alkalinity issues. Also using NH4 wont help you control pH in your solution if using DTW, but it will help control pH in your medium, which matters more but wont help you control your solution pH which is what you originally asked, however the other things i mentioned will still help control pH of both your solution and medium.

Make sure your pH down is only phosphoric acid (no citric), it will have the best pH stabilizing effect for you.

Your link was a good read, though it's quite specific to recirculating systems, while OP mentions running DTW.

I'm also interested in your opinion on how to use Jack's Pro to create an optimally balanced nutrient profile for cannabis. Please share.

Thanks for pointing that out. I thought OP said RDWC for some reason.

A huge part of why using dry salts is optimal, aside from the price, is the level of control you have over the ability to tweak the formula. I almost never feed the same formula twice, but my go-to formula for DTW fertigating in peat moss if im in a hurry or cant use a nutrient calculator is:

Per Gallon:
2.50g Jacks Professional Hydroponic
2.50g Calcium Nitrate
0.25g Potassium Silicate
0.25g Ammonium Sulphate or Ammonium Di-Basic Phosphate depending on bloom stage

which turns out to be

NO3:NH4 ratio - 6:1
N - 150 ppm
P - 35 ppm (or 50ppm)
K - 165 ppm
Ca - 125 ppm
Mg - 40 ppm
S - 70 ppm (or 55ppm)
Si - 15 ppm

 

[midwestdensies]

love the concise and translation to some not so scientific folk of your posts dizzlekush. Great info

 

[squiggly]

this is a huge threadjack, but if I wanted to make a gallon of 3.5 mM K solution, would I add 0.5273 grams of K to a 1 gallon jug and fill it up with water?

Just trying to wrap my head around the math of things.

3.5mM = 3.5x10E-3 moles / Liter

Atomic weight potassium nitrate = 101.1032 g/mol

3.5x10E-3 mol X 101.1032 g/mol = 0.0035 mol X 101.1032 g/mol

= 0.35386 g


0.354g / L = 3.5mM KNO3

1 gallon = 3.78541L

0.354 g/L X 3.78541 L / G = 1.3400 g/G

 

[Capulator]

3.5mM = 3.5x10E-3 moles / Liter

Atomic weight potassium nitrate = 101.1032 g/mol

3.5x10E-3 mol X 101.1032 g/mol = 0.0035 mol X 101.1032 g/mol

= 0.35386 g


0.354g / L = 3.5mM KNO3

1 gallon = 3.78541L

0.354 g/L X 3.78541 L / G = 1.3400 g/G

Can you do that again with just K?

 

[squiggly]

Can you do that again with just K?

Sure.


3.5mM = 3.5x10E-3 moles / Liter

Atomic weight potassium = 39.0983 g/mol

0.0035 mol X 39.0983 g/mol

= 0.136844 g


0.137g / L = 3.5mM KNO3

1 gallon = 3.78541L

0.137 g/L X 3.78541 L / G = 0.518 g/G
Which is, you'll note, pretty damn close to your original figure.

My question is how are you getting "pure" K and then dissolving it? It's possible, it's just super exothermic is all (ie BOOM). The calculations get thrown off when it is a salt, it is important to account for the ion it is balanced with in the calculation. Be it KCl, KNO3, or what-have-you. This is because, in salt form, those ions make up part of the weight you are adding.

ppm only deals in weights which do not correlate perfectly to molarity or molality.

One cares about mass (ppm)
The other cares about molar mass, which is a different measure altogether.

The first can be simplified to mean simply weight solute per total weight solution (further simplified in water due to its density of ~1g/mL).

The second (molarity/molality) cares about moles of solute or the number of molecules which correlates to the atomic masses of its constituent atoms (per liter of solution--regardless of the weight, density, or molar mass of the solvent). We simplify this out (as in the calculation above) to tell us a mass that we input, but it's not as simple as saying how much does potassium weigh and then calculating with only the potassium.

If you want molarity, you need to know the salt and it's molar mass (and preferably whether or not it is hydrated). This is information that the manufacturer should be able to provide for you if it's not included on the label.

You cannot directly convert from ppm to molarity without compound specific information--these are different measures of concentration.

 

[Capulator]

Sure.


3.5mM = 3.5x10E-3 moles / Liter

Atomic weight potassium = 39.0983 g/mol

0.0035 mol X 39.0983 g/mol

= 0.136844 g


0.137g / L = 3.5mM KNO3

1 gallon = 3.78541L

0.137 g/L X 3.78541 L / G = 0.518 g/G
Which is, you'll note, pretty damn close to your original figure.

My question is how are you getting "pure" K and then dissolving it? It's possible, it's just super exothermic is all (ie BOOM). The calculations get thrown off when it is a salt, it is important to account for the ion it is balanced with in the calculation. Be it KCl, KNO3, or what-have-you. This is because, in salt form, those ions make up part of the weight you are adding.

ppm only deals in weights which do not correlate perfectly to molarity or molality.

One cares about mass (ppm)
The other cares about molar mass, which is a different measure altogether.

The first can be simplified to mean simply weight solute per total weight solution (further simplified in water due to its density of ~1g/mL).

The second (molarity/molality) cares about moles of solute or the number of molecules which correlates to the atomic masses of its constituent atoms (per liter of solution--regardless of the weight, density, or molar mass of the solvent). We simplify this out (as in the calculation above) to tell us a mass that we input, but it's not as simple as saying how much does potassium weigh and then calculating with only the potassium.

If you want molarity, you need to know the salt and it's molar mass (and preferably whether or not it is hydrated). This is information that the manufacturer should be able to provide for you if it's not included on the label.

You cannot directly convert from ppm to molarity without compound specific information--these are different measures of concentration.

I was just trying to do a calculation. Thank you Squiggly. :)

 

[squiggly]

I was just trying to do a calculation. Thank you Squiggly. :)

NPs

Far be it from me to miss an opportunity to insert an unsolicited chemistry lesson!

 

[kushtrees]

15ppms silica sounds good to me. I just looked at my nute calc and 2.5ml protek comes out to 50ppms silica. I am going to try .5ml/ gal to start which should get me about 10ppms and then slowly go up from there to maybe 1ml/ gal to see how that goes.

I care more about my medium pH then the res pH but I figure the 1st step in getting the medium pH back in the correct area would be Getting the solution pH sorted out. The most worrisome thing to me was the 7.3 pH run off.

Btw dizzle what pH range do you like for peat? I've been trying to keep it around 5.8-6.1 because the res waters my coco room too but next week I am going to have to get out the 2nd res so I can keep 2 different solutions.