Experimenting with the Megacrop PH and Buffering šŸ“ˆ

Indoor Growing Hydroponics
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The equations are just straight line approximations of the PH titrations between 5.6-6.5 using the ubiqutous y = (m)x + b. (m) being the slope, (x) being the independent quantity of KOH, (y) being the dependent PH, and you can for the most part ignore the intercept (b) when looking for rate of change differences.

While not tied directly to time, if everything else between the two remains the same, then that should work out as youā€™ve described. At minimum, there most certainly should be a slowing of any PH change. PH is logarithmic, so Iā€™d have to twist my mind around this to figure out how a pre-existing time based problem would come into play. Iā€™m unable to do so at the moment :slight_smile:

Received the ion exchange resins, will try these when I have some free time.

Lol. If there is a purpose, Iā€™ve just been given the excuse to explore things that Iā€™ve also been curious about. Similar to your documentation of your HPA experiments (and copper).

I do hope that these types of exploration on OG will expand and help contribute to our collective knowledge and discussion no matter how itā€™s applied. And, I hope others will feel encouraged to do the same. Whether success or failure.

edit:

This ion exchange resin appears quite slow to react to changes in the OH- concentration. From the way this is acting, Iā€™m thinking that in practice there would need to be an initial preparation stage to get the PH of the resin somewhere near the target PH before placing into the final solution (initially quite acidic). The initial stabilization appears to take a bit of time but it may be improving on subsequent step changes.
This will take a bit to get figured out. Iā€™ll need to restart this titration and drop the amount of resin in solution down somewhat. I started out at a fairly large amount of resin and will scale this back to the suggested 1g/gal. This looks like itā€™ll a bit more lengthy of a titration and I may need to revise how I collect the data for this one.

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Excellent. I just replaced some plumbing parts, cleaned, and re-filled the system. I couldnt do a really thorough cleaning because I would have had to leave the roots with no mist for too long, but I can already tell that made at least some difference. My MES will be here in few days, so that will give me a new baseline for comparison.

That was fast! I am really eager to see how the resin compares.

Im curious how you are doing this physically. That resin is listed as a fine powder. Did you just add it to the liquid or is it in a bag or filter or?

Im not at all sure how it gets prepped before use. The only thing I read was it can be re-conditioned by a rinse, and soak in acid. I dont have any real details though, so no clue how long to soak or the PH of the acid needed or if the type of acid makes a difference.

Iā€™ll see if I can find anything specificā€¦

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Yes, fast to receive. Explains the expense to some extent. Cost, ~$1.30 per gram delivered.

Iā€™m just adding it to 500ml of RO + MC and stirring the entire concoction. That is for the titration curves. Not for practical use. What you would see from this is a curve would be based on the optimal solution contact with the resin.
The CG-50 is quite fine and would probably not work well in a filter bag. It may work in a ā€œcolumnā€ or an in-line style filter with a small screen size. It is really intended for columns, I think. You do get lots of surface area, conversely.

Found this from the Jay Frick, et. al., ā€œStabilization of pH in Solid-matrix Hydroponic Systemsā€ paper:

For resin bead incorporation strategies, Amberlite DP-1 (cation-exchange resin beads, 16 to 50 wet mesh, 8.1 meq/g; Sigma) were first conditioned, pH-adjusted, and nutrient loaded as in Barta et al. (1990). Conditioning involved slow column elution with 20 resin bed volumes of each of the following solutions in sequence: 1 N HCl in 3% (v/v) aqueous methyl alcohol, 1 N NaOH, 1 N HCl, and 10-3 M Ca(NO3)2.
For pH adjustment, resin beads were soaked for 48 h in a KOH solution, with KOH concentration dependent on desired pH and ionic strength of the nutrient solution. The nutrient-loading step included another column elution step with highly concentrated (10Ɨ) Hoagland 1 nutrient solution. Major cations included K+, Ca+2, Mg+2. and micronutrient cations.

The Barta paper is entitled, ā€œPreparation and use of weak acid resins for pH control in plant growth media and soil-less culture systems.ā€ I have not found an on-line copy of this paper.

So, it seems as though they are pre-loading the cation and anion sites along with adjusting the PH of the beads (as a starting point). This may not be as complicated as it sounds and could be a simple as having the beads sit in a concentrated PH adjusted nutrient formulation prior to adding it into the system. But, idk. Would need to get into the theory of how these resins work to develop a protocol.

This is a plot from the data while Iā€™m getting used to how this stuff acts:

image.png1386Ɨ560 67.4 KB

The CG-50 is the red curve. The other curves are the various MES concentrations.
The CG-50 is relatively slow to stabilize and because of that I decided to call it stabilzed when the meter shows 1/1000 of 1 PH stable for > 2 seconds or so. At around PH of 6, I changed that to let the solution stabilize for >45 minutes per point. Thatā€™s where you see the PH drop. When itā€™s stabilized, it does seem to stay fairly stable only moving several hundredths of 1 PH overnight. This is without any pre-conditioning steps on the CG-50 and a relatively large amount of the resin (500mg).
Iā€™m going to restart this today with a smaller quantity of the resin and along with longer dwell times.

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Very interesting. Im going to have to review that graph a few times I think. Im not at all sure how to interpret whats going on as far as telling if the resin is ā€œbetterā€ than the MES for our use.

The MES 0.005M and 0.010M plots are both flatter than the resin plot.

Wait - I just realized the three higher concentration MES plots and the resin plot are not covering the same range as the lower MES mixes 5.6-6.5? On the other hand, the resin looks to have similar ā€˜buffer capacityā€™ to the 0.01M MES and almost as good as the 0.02M MES.

That higher capacity is a good sign, especially since you did do any pre-conditioning.

On the other hand, that preconditioning makes me hesitate a bit. That plus the probable need for some sort of inline column filter has me hesitating a bit. Im not sure how to integrate something like that into my system without a fair amount of trouble. Iā€™ll have to think about that part a good bit.

I have not had time to do any more looking for info/details on how to prep or condition the resins. I wonder if we could email the author of that paper and see if he would forward a copy to us? I will put that on my list of things to doā€¦

Here is a quote from that HydroBUddy guy who recommended using the resins in hydro to control PH.

Ion exchange resins are insoluble and the only thing they need to be efficient is to have solution passed around them all the time. So it is simply a matter of putting the ion exchange resin in a place where fresh passing solution will be in contact with it all the time - like inside a filter connected to the irrigation system - and thats it, no more pH problems, no more additions to control pH, problem absolutely solved.

and then this as far as re-conditioning.

However not ALL ion exchange resins work. Particularly the type of resins that work well in hydroponics are weakly acidic cation exchange resins and their effect has been studied extensively on several peer reviewed publications. If you want to use these resins in your hydroponic system you need to buy the commercially available Amberlite DP-1, Amberlite IRC-50 or the more recently available Amberlite CG50. You would need about 1g per gallon of solution you wish to control and you should place the resin in an inline filter - those used for drip irrigation are great - to achieve the desired pH control levels. When the resin stops working you simply need to take it out, wash it place it in dilute hydrochloric acid (your average pH down solution will do), then wash it again, to regenerate its surface and prepare it for another crop.

I just noticed that point. The HydroBuddy guy in the link above recommends 1 gm/gallon, so your initial testing was almost 4x higher concentration. On the other hand, he says to get longer duration of PH control, you just need to add more resin.

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Iā€™ve titrated a solution containing Megacrop along with 132.3mg of CG-50 ion exchange resin.

The overall titration was monitored in 10 second intervals. Each addition of 100uL of 1M KOH would be added after allowing the solution to stabilize to some extent. The point where I considered it to be minimally stabilized was at 1/1000th of 1 PH unchanged for 40 seconds. As you note in the stabilization plot below, the true time to stabilize is quite lengthy and I was not interested in waiting the many hours per point.

The entirety of the titration over time looks as follows:

image.png875Ɨ534 9.97 KB

As you might notice, stabilization of the PH in the solution containing the CG-50 is a very slow process as the resin slowly exchanges OH- ions with H+ ions. Also notice, the CG-50 without any preconditioning acts acidic when first added into solution.
An example of the time to stabilize a step change in OH- ions:

image.png821Ɨ412 11.2 KB

The titration of the solution as compared to MES looks like the following:

image.png1369Ɨ571 67.4 KB

The dark blue plot is the ā€œamountā€ of CG-50 as suggested by others for use in hydroponics (1g/gallon = 132mg/500ml).

From the linear equation produced, the suggested amount might have a similar effect as that of 2mM MES. Whether or not the CG-50 will continue to absorb OH- ions up to the capacity of the resin at any one PH is not clear to me. Though, the rate (speed) at which the OH- ions are absorbed does appear to be a function of the solution PH.

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Very interesting. It looks like this would be usable, and might work very well, but Im not sure its as simple as that guy suggested in his blog. I think youā€™re going to have to have a re-circulating pump with the MES in an inline type filter of some sort and just let it run constantly.

I still have not received an answer from Dow on a replacement product for the CG 50. I would prefer one that wasnt a fine powder, but larger beads - I think.

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The primary advantage with CG-50 seems to be the re-usability.

Depending on how the resin is conditioned, it could also have the significant advantage of controlling which minerals are locked up by the resin when exchanging ions e.g. releasing cations such as Mg+, Ca+, K+ while uptaking PO4-, SO4-, NH3-. Or, conversely. But, how this really works and how to utilize this to your advantage, I donā€™t really have the knowledge. I think there are some papers that talk about using several different type of resins (mixed bed) to completely control the PH and the nutrients of a feed system (with a variety of preconditioning steps).

Otherwise, the disadvantages include relatively slow ion exchange, need to pre-condition / ph the beads, and the need to recirculate the solution around the beads. Another note, once the beads are hydrated with water, they must remain hydrated otherwise they will be damaged. They can not be dried once wet.

The CG-50 is quite fine. Whether it would be of use in a non-recirculating system and within some sort of a filter bag, I donā€™t really know.

At the 1g/gallon, the CG-50 resin beads appear to be on-par with MES 2mM for PH buffering. The specific circumstance might make one more worthwhile than the other. There may be a cost advantage to the resin if the system is dialed in at the expense of some additional labor.

MES and the other chemical buffers are relatively easier to use and are much faster to exchange ions. The disadvantage is that the buffer is disposed of and, hence, recurring cost.

Also, if one is able to figure out how to pre-condition the beads in such a way to avoid throwing the nutrient balance out of whack, a large quantity could possibly maintain PH buffering indefinitely. That is, if thatā€™s even possible. Or, for that matter, desirable. Perhaps, a mixed bed but thatā€™s next level. With MES and the other buffers, you donā€™t really have that possibility. There are safe maximums.

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LOL I seem to remember someone in one of these threads saying that PH was not simple. Boy is that an understatement! :slight_smile:

You bring up one of my current questions - how stable do you really want the PH to be? And - if you want a PH swing - how fast a swing is safe?

If youā€™re growing in soil, and feeding from some sort of tank, I think you want that tank to stay more or less where you set it until its empty. The advantage there is you dont have roots constantly trying to change the PH in the tank, so that should be fairly easy - unless you have my algae problem in your water.

In Hydro on the other hand, most folks agree that a PH swing is best - 5.5ish to 6.2ish seems to be the most common range. Whether MES or the resin is best will depend on the details of the system mechanics/plumbing, as well as how your plant is handling the nutes.

On mechanics/plumbing - DWC bubble buckets that only use air stones will have a harder time using resins because of no circulating pump to force the water through the resin. Same thing for me with drain to waste. I would need a circulating pump that could force water through a finely packed resin powder somewhere in the rez. Or I need to use up MES more often.

Then there is the chemistry of the roots. Some hydro systems trend downward in PH depending on EC and health of the roots, and others trend upwards in PH.

My setup was going up wildly fast, but it turns out that the cause was not roots, or nutes, but some sort of brown zombie algae/slime/crud that was forcing the PH way up way fast. Now that I seem to have killed it off, I have a new problem - the darn PH wont change on its own!

I like the idea of a PH swing from low to hi. Before I had way too much swing way to fast. Now I have zero swing and Im having to force it to go up with PH Up.

I guess this is just ā€œlifeā€ but it doesnt seem fair that fixing one PH problem causes a new PH problem! :slight_smile:

Now that the zombie algae is dead (I hope the fu%$ers stay dead!!) I have the exact opposite PH problem. I need an anti-buffer instead of a buffer!!

I still think this thread needs to be made a FAQ.

@Northern_Loki also has a few really great posts over in my HPA thread that need to get copied over here. Tons of very helpful data.

Thanks again for all the time effort and $$ you have put into this project!!

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Absolutely, but then, if you are growing in soil there is a PH range where you have all the nutrients available, being 6.5-7. In hydro there is no PH value where all the elements are available enough to allow vigorous growth with no deficiencies.

To my mind, a good way would be to look at the availability of particular nutrients at particular PH values then weight the amount of time you keep your solution at those PH values so your plants have more time in the ranges where the nutrients they need most are available.

Zinc, for example, is not needed in great quantities and is not a mobile element so to my mind you would not need to drop down to 5.5 (where zinc is available) often or for long. So long as each leaf gets some as it develops that should be enough. So in my system I have about 12-24 hours at 5.5 every four days or so.

Regarding how fast to swing, I would again take cues from the plant. In an ideal world, all the nutrients needed for a leaf to grow would be present at all times during its growth. If you only have certain elements available at any one time then you want to make sure you cover them all during the time it takes a leaf to grow.

So that should be the slowest you should allow your PH to do a full swing of PH. Any slower than that and you risk the leaf being fully grown and it has missed out on some particular nutrient. I have not actually recorded a timelapse of a leaf growing (which would be very cool, might have to do that) so I do not know for sure but I imagine that would be about four days from growing tip to full leaf. So I try to do two full swings a week. Most of the time the PH is over 5.8.

I am not sure that a change of only 0.5PH would be enough to shock the plants if the PH Up/PH Down was mixed well enough into the solution before applying it to the roots.

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That makes a lot of sense to me.

Interesting. When you say two full swings, do you mean going from 5.5 up to 6.?, then back down to 5.5? Is that two swings or one?

I see most folks talk about letting PH climb during the week, then when it is time to refresh the rez, the just start over back at 5.5 or where ever.

Itā€™s that sudden change from 6+ down to 5.5 when you start over with a fresh rez that had me concerned. On the other hand, I suspect the vast majority of hydro people do it that way, so it cant be all that bad, but it still seems like a slightly more gradual change might be betterā€¦

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I mean start at 5.5, let it go to 6.1, then drop it to 5.5 again, then rise to 6.1 and that should take a week and give you two swings across the PH range. I try to stay more time between 5.8 and 6 than any other value. At that point, I feel there has been enough PH adjustment and nutrient consumption to be cost-effective to refresh the tank.

Depending on your base water it may be better to start at 6.1 (less PH adjustment initially) then drop to 5.5 after a few days, stay there for 12-24 hours, then raise to 6.1 again for a few days finally dropping to 5.5 for 12-24 hours just before you refresh the tank. This may mean less PH Up and PH Down in your solution.

My experience is that if your run RO then you may need to go higher (up to 6.1-6.2 instead of 5.8-6.0) in PH to get better Mg uptake, I found I had more Mg available at lower PH values with tap water. But then yield and quality were lower too.

I also used to be more concerned with changes to PH but I am less so these days. I donā€™t think changing 0.5PH points is that great of a change for the roots. I would be very interested to hear from anyone with info about this sort of thing. I still am concerned with rapid EC changes as depending on how much of a change, you may have to wait for the plant to acclimatise before it will continue with vigorous growth.

It may be that adding the PH Down or PH Up in one go to make that change would cause pockets of precipitation from the PH being way out of the range where the nutes can remain in solution. It may also be that you get a wash of high or low PH nutrient solution over the roots if it is not mixed well before it gets fed to the plants. Those are the only ways I can think that a rapid change could cause issues.

I do it over about 2 hours with microdosing of PH adjuster every 10 minutes (1-2ml diluted 1:10 so 0.1-0.2ml of adjuster every 10 minutes). This limits precipitation to a very small area around the place where the acid/alkaline is introduced.

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Im jealous of your automated system. It sounds awesome!! :slight_smile:

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Well, the zombie algae in my HPA system is back and causing drastic PH upwards changes in the hi-pressure parts of my system, so I decided to test the MES to see how well it could handle this situation. The rez has been at 5.5-5.6 range, but the accumulator tank has been going up to 6.1 or higher in just an hour or so and the PH a the nozzles has been as hi as 6.5 or more. My plants are not liking this hi a PH.

I drained the nutes from my accumulator tank back into the rez. That gave me about 8 gallons total to treat. I decided to start with an MES concentration of 0.005M or 5mM. That should be a low enough concentration so the MES does not cause any additional nute issues.

After draining the hi PH water in the tank back into the rez, it was at 5.7. Then I dissolved 29 gms of MES into roughly 8 gallons/30 liters. It dissolves easily.

After a good mix, the PH in the rez dropped to 5.0. I slowly added potassium hydroxide (KOH) to the rez to bring it up to 5.5. It seemed to take a lot of the KOH to change the solution compared to usual, so thats good so far.

Unfortunately, I cant compare to @Northern_Loki graphs because I dont know the concentration of my KOH mix. I didnt think I would need to know that when I mixed it up originally, so this is just a feeling on it taking more than normal to shift the PH up.

I also added more chlorine at about 6 PPM. I have been ading chlorine every couple of days at 2 to 4 PPM and it has not helped.

All of that raised the EC from 1.05 or so to 1.2. Im assuming it was the MES that did most of that.

We will see shortly how well this does.

Cost wise, I got a 100 gm bottle for $22 shipped, so that 29 gms of MES cost me a little over $6 to treat 8 gallons. I am using about 2 gallons of nutes per day at the moment, so if I have to keep this up, it will add about $1.50 / day. Thats going to add a fair amount of extra cost over the life of a grow, and thats assuming the MES keeps the PH within reasonable range over the full time that a rez lasts - which I doubt.

I really really need to kill off this zombie algae crap.

I should have time early in the morning to check how the PH in the pressurized parts of the system are doing before I have to run off again.

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Quick up-date then I have to run again. The combination of extra chlorine shock and MES is working!

The MES alone was able to keep the nozzle PH at 5.9 while the rez was at 5.5. Lowering the PH in the rez to 5.3 dropped the nozzle PH to 5.7 and its stayed at 5.7 for the last 12 hours or so. Woo hoo!

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Ive been slowly lowering the concentration of MES in my system for the last week or so. I started at 5mM, then 2mM and now Im at or just under 1mM.

Its very obvious how well it works. It is taking far less PH Up or Down to change PH as the concentration gets lower.

I am very impressed with how well this stuff works. Thanks again to @Northern_Loki for all the research, detailed testing and educational posts!!!

Under some situations, I think this would make a viable option for someone with a nasty PH issue that needs short term handling. For long term, I still think it would be better to fix the source or what ever is causing the PH changes.

In my case, I think any treatment that killed the algae for good would kill the plant first, so the MES has saved my grow.

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Oh, you are quite welcome. Iā€™m glad it was useful. Trying it in practice means you are a key contributor to this experiment. Thank you.

Iā€™ve learned a great deal in trying this. And, itā€™s fun, too.

Yes, definitely better to try to figure out the source of any problems.
Though, I do believe that the use of a buffer can also be a helpful tools in situations even when the swings are less extreme and less pronounced. Particularly for systems where the media is a fluid and there is a significant amount of manipulation going on, RDWC, etc.

I still have several buffers/buffer combinations to try out to expand the reference information.

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Thank you @Northern_Loki

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Amazing work, wow :open_mouth: :open_mouth: :open_mouth:

How did we never see this until now? :clap:

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There has been some interest in looking at the Jackā€™s nutrient line buffering capacity so I ordered up the most recent version of the Jack 321 and RO base formulations from a local supply house.

33-103020 Jacks Nutrients 10-30-20 Bloom FeED
33-12416 Jacks Nutrients 12-4-16 Hydro FeED RO
33-15617 Jacks Nutrients 15-6-17 Clone FeED
33-51226 Jacks Nutrients 5-12-26 Part A FeED
33-55018 Jacks Nutrients 5-50-18 FeED UltraViolet
33-71530 Jacks Nutrients 7-15-30 Finish FeED

Already stocked:
Part B: PLANTEX Calcium Nitrate Purecal 10033
Part C: Dr. Teals Epsom Salt

Weā€™ll be looking at the inherent buffering of the 321 formulation to compare with previous trials. Also, will look at the RO specific version of this once received.

For the part B and C, Iā€™ll be utilizing the stock of Calcium Nitrate and Magnesium Sulfate that I already have on hand. Iā€™m assuming that the B and C are pure, which I believe is the case, and do not have anything else to change the alkalinity. Such as bicarbonates.

For 321, weā€™ll be using the Part A along with any needed Part B out of my stock (Calcium Nitrate). Part C, if added, will simply be Epsom Salts. Target will be adjusted such that the EC is 1.7 in order to favorably match the salt concentrations of previous trials.

The remaining ingredients are for a trial grow and probably not evaluated here.

Back-linked thread to an example of using the 321 successfully that has spurred this evaluation:

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Im looking forward to this series of tests.

Just to put all the notes in one place: Many people, including me, have noted that the Jacks seems to have a high buffer capacity relative to other brands of nutes. In other words, its much more PH stable than the other nutes.

In my case, I am comparing Jacks 321 hydro to past grows with Mega Crop (v1, v2, and v3) Advanced Nutes PH Perfect line, and Fox Farms nutes. Ive even added extra buffers in the form of MES to both Mega Crop and Advanced Nutes and the Jacks is still far superior in its ability to hold PH stable in my system.

You and I both suspect that a large portion of Jacks perceived extra PH ā€œbuffer capacityā€ is actually due to Jacks NOT having organics in it that can feed algae/bacterial growth. The theory being that the rise in PH in many systems is due to algae/bacteria feeding on the organics, which then drives up the PH.

I am very curious to see how this testing goes.

Once again - thanks for doing this for the community!!!

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