Check My Math: Adding Disodium EDTA to Your HydroBuddy Nutrient Recipe?

[ExNavyInSTL]

I would like someone who makes their own fertilizer to check my math.

I've learned Hydro Buddy and I have created my "ideal" nutrient recipe (in theory).

However, I want to make sure I understand the formula for adding Disodium EDTA to chelate my Fe, Mn, Zn & Cu.

From what I have extrapolated from Dr. Daniel Fernandez's various comments at the bottom of his DIY Nutrient videos on YouTube, it goes something like this.

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1) After Final Recipe has been chosen and concentrated (i.e. 1 Liter @ 200:1),
you take the millimolar concentration amount and change 'ppm' to mM' on "Main Page."

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After Switching to 'mM," it looks like this:

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2) Once you have the millimolar concentration (numbers above in yellow boxes), you add up the 4 numbers:

Fe: 4.298E-02
Mn: 9.101E-03
Zn: 3.363E-03
Cu: 4.721E-03
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= 6.02E-02 (0.0602)

Actually it is: 0.060165

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3) Once you establish this number:

Multiply by the concentration Amount (200:1). It would be multiply by 100 if 100:1.

0.060165 x 200
= 12.033

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4) Next he likes to add 20 or 25% for safety.

12.033 x 1.25
=15.041

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5) Now you take your "safe" total and multiply by the molar mass of Disodium EDTA (336.21) for your grams:

15.0412 x 0.33621

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That leaves you with the grams required.

However, the number isn't necessarily complete.
In this case, it is, but if the amount was 0.5 liter it would be different.

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For the Final Number, Multiply grams by the volume of concentration (1 Liter):

5.06 x 1.00
= 5.06 grams

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If it were for 0.5 liters, then it would be :

5.06 x 0.5
=2.53 grams

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Have I interpreted the formula correctly?

 

[DCLXVI]

Well that is far beyond my knowledge. There was a guy @Bruce Campbell who was pretty into nutrient math breakdowns. I don't know if he is still around. Good luck!

 

[ExNavyInSTL]

I hear ya. Well above mine too.

I just hope I put it in a form so that people who do know what I am talking about can make sense of it.

Here is a little more background. The first is a screenshot from me. His answer had me going back to my college chemistry classes (that I got Ds in both).

I was suddenly using a periodic table to get molar mass, then going to calculators for molar concentration, etc.

Then in another video's comments, he put it in a way that made the lightbulb go on in my head. HydroBuddy already had molar concentration inside. You just had to change one setting.

From that answer, I was able to formulate the question above (I hope).

Another Answer:

Well that is far beyond my knowledge. There was a guy @Bruce Campbell who was pretty into nutrient math breakdowns. I don't know if he is still around. Good luck!

 

[BII]

[Am I misunderstanding something here?] What type of base fertilizer is this being used with? Or are you mixing elemental components, including the individual metal salts?

If chelating a mixed fertilizer, does simply adding the chelating agent just react with the specific metal ions of interest (with the assumption made here of equal molar amounts of these few ions and chelating agent reacting fully)? Won't Ca, Mg, amino acids, inorganic (e.g., phosphoric) acids used to adjust pH, etc. also take up the chelating agent, perhaps even more strongly than the metal ions? Will the chelation be messed up when you pH adjust your feed?

Wouldn't it be better and simpler to add individually already-reacted chelated ions; that is add pure purchased chelates?

Adding 5 g/L of a sodium salt seems like adding a lot a sodium ions, generally not desirable.

 

[ExNavyInSTL]

BII

I'm building this fertilizer from scratch, which uses non-chelated sulfate metals.

The Disodium EDTA is chelating only Fe, Mn, Zn, and Cu in the recipe.

I understand your concerns about Na, but remember that is a highly concentrated (200:1) mixture.

Those 5 grams are spread over 53 gallons. If I make a batch that is doled out at 5ml per liter, that means 200 doses (liters). Converted to gallons at 3.785 L/Gal, it is 52 and some change.

Plus, Na2 is less that 14% of the molar weight (mass). Meaning, 0.7g of the 5 grams or 0.013 grams/gallon.

As for the chelating part, I promise I didn't make all of this up out of thin air. I listened to these videos over and over until it made enough sense for me to be less dangerous.

These videos are from Dr. Daniel Fernandez. He is the creator of HydroBuddy and the owner of "Science in Hydroponics."







Yes, pH could affect the chelation, but from what I understand nothing significant at the 5.8 - 6.2 pH range we use for coco. Plus, I think that is why he uses a 20-25% safety factor.

As for your question: "Wouldn't it be better and simpler to add individually already-reacted chelated ions; that is add pure purchased chelates?"

The answer is YES it would be easier. However, I decided to follow Dr. F's lead and do it his way by using sulfates for Fe, Mn, Zn, and Cu.

This is all fun to me, so I don't mind doing it the long/hard way.

By the way, I'm actually starting out at 0.5 liters at 100:1 to test out my recipe. My thinking is, why make a bunch of something that melts my plants?

Growing is my hobby, and this is just another way to add some complexity (challenge) to the process. I liken making my own fertilizer recipes to my current decision to SCROG this grow. The technique is new to me and a lot more hands-on. I'm following the Northen Scrogger method, keeping the trellis about 6 inches above the pot, which makes the plants more like vines. This way definitely more work than typical topping and LST, but I really like it so far.

What really brought me over to the DIY (nutes) side was this video by Dr. Bernstein (senior research scientist and head, Cannabis Physiology and Agronomy Lab, Volcani Center, Ministry of Agriculture, Israel).

In this video, I learned things that were counter to everything I read on forums about Veg versus Flower nutrition.

Here's the gist of what her experiments proved.

Nitrogen (elemental): No need for more than 160 ppm in Veg or Flower

Phosphorus (elemental): No more than 30 ppm in Veg or Flower. Although it has a wide forgiving range (15 - 90), but no real gain comes from going above 30.

Potassium (elemental): No more than 100 ppm in Veg or Flower. Above 100 - 175 are also safe zones you just don't gain anything.

Magnesium (elemental): 30 - 40 ppm in Veg and in Flower. Friendly range of 35 - 140 ppm, but you are damaging the quality of the end product.

This is really an amazing lecture if you have the time or nerd out on this sort of stuff. She is why I call this Israeli Mix. You have to give and take a little because we also use combination elements like in Calcium Nitrate. I went higher on the Mg because I wanted it to be closer to 1/2 of Ca.

Just for giggles, at the end, I'll post a template I am working on.

Dr. Nirit Bernstein


Side Note: For Sodium Benzoate I decided on 0.1% of mass for 200:1 and 0.75% for 100:1, with a ceiling of 0.3 grams.

[Am I misunderstanding something here?] What type of base fertilizer is this being used with? Or are you mixing elemental components, including the individual metal salts?

If chelating a mixed fertilizer, does simply adding the chelating agent just react with the specific metal ions of interest (with the assumption made here of equal molar amounts of these few ions and chelating agent reacting fully)? Won't Ca, Mg, amino acids, inorganic (e.g., phosphoric) acids used to adjust pH, etc. also take up the chelating agent, perhaps even more strongly than the metal ions? Will the chelation be messed up when you pH adjust your feed?

Wouldn't it be better and simpler to add individually already-reacted chelated ions; that is add pure purchased chelates?

Adding 5 g/L of a sodium salt seems like adding a lot a sodium ions, generally not desirable.

 

[ExNavyInSTL]

I got my answer. Even better, this way is more concise.

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I should add: I hope I got my answer.

To complete the calculation determining the amount of Disodium EDTA needed for proper chelation, you will need to know:

(1) Elemental PPMS of the 4 metals (comes from HydroBuddy (see bottom section of my attachment)

(2) Molecular Weight of the exact formula for your metal.
For example, my Fe is Iron Sulphate - Heptahydrate (Fe2H14O19S3) - 278.01 g/mol
Just Google the Formula to get your Molecular weight

(3) Once you have those 2 things, you are off to the races.

Special Note: I am just a guy on the internet. I would trust me as much as you would a teenage boy taking your daughter on a first date to a 10-kegger party.

Also, my phrases (i.e. Molecular weight, vs. molar mass, etc.) may be off, but the math solutions should be correct.

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Calculations to complete in this order:

(a) Divide individual metal element's PPM by molecular weight:

For example, in my scenario, I have 2.4 ppm of my Fe and we know the molecular weight is 278.01

2.4 / 278.01 = 0.00863

(b) Add (by multiplying) 20 to 25% to this number for a safety factor.
I'm going with 25% because of my inexperience.

0.00863 x 1.25 = 0.0108

(c) Next, multiply your 25% padded number by the molecular weight of Disodium EDTA (372.24)
In my case the m. weight was listed on my container.

0.0108 x 372.24 = 4.017

(d) Do these steps for all four of your metals to chelate.

To expedite, here are all four of my values

Fe: 4.017 grams
+ Mn: 1.541
+ Zn: 0.634
+ Cu: 0.559
--------------------
6.751 grams of Disodium EDTA

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Below, I will attach my updated "Template in the Making." I say in the making because I seem to change it every day.

I put in the formulas for all of the math, so it isn't a big deal after the first time. Of course, I still triple-check my formulas. So, it's a wash. : )

I know I can't be the only person who said they wanted to make their own nutrients, who didn't want to buy them already chelated or in a multi-metal mix (i.e. Peter's S.T.E.M.)

I'll report back if I kill my plants or my wife's tomatoes.

 

[Bob's Auto's]

Hey buddy, hehe buddy as in HydroBuddy
I know I'm late to the show, but why don't you use chelated forms of the minerals/metals? EDDHA are the best, which dissolve in water and remain stable over a wide pH range.

 

[ExNavyInSTL]

@Bob's Auto's

It's a good question. The answer is a combination of trust and ignorance.

Stand by for a TLDR response. Although I hope you will.

I completely trust the good Doctor who puts out the DIY videos and I absolutely love his HydroBuddy.

In fact, it was HydroBuddy that got the ball rolling.

At first, I used HydroBuddy to analyze current products on the market. I got this from watching GreenGene's Garden videos.

I am a Jack's 3-2-1 person at the core. But, like the old saying, "Trust, but verify."I wanted to compare them to other popular brands like Athena, Mega Crop, Master Blend, and FloraFlex (which I am using on this grow) ... among others.

The second goal was to comb the internet for other people who test theories in the lab. Thus, looking to see if the scientists had standardized the micronutrients, Many of them tell you exactly the dose of elemental ppm by the individual nutrients. I was mostly interested in micros.

Also, I wanted to compare these fertilizers to what folks like Harley Smith and Bruce Bugbee say are needed.

I wasn't exactly trying to find the bare minimum. However, I didn't want to waste money by over-fertilizing either ... this is before considering toxicity levels.

Now, on to your real question, "Why not just use already-chelated metals?"

This is where ignorance and trust cross again. When watching the main 3 videos of Dr. Fernandez showing how to make your own, it looks INCREDIBLY simple. And it really is.

The only caveat is that you have to make in concentrations (for the most part) because of the tiny amounts of some of the ingredients at the per-gallon mindset. Sure you could whip up 100 gallons, but you get the idea. For us home growers the most I ever make at a time is about 15 gallons. The idea of creating a 1-liter jar of concentrate that will make a bunch of gallons later is enticing. Pulling out a syringe or small measuring cup to do this is good too.

Prepare for a false-logic answer (when you are married to an attorney you hear that phrase fairly often.)

Just like the mindset, "Why pay for shipping water?" I also imagined that if you could separate the materials it would be better. My thinking (flawed or not) was if you use individually chelated items there would be safety margins in each of the 4 metals. Thus, having way more Chelator than you need. I thought, if I can dial it in with one safety margin I would be putting less EDTA into the mix,

And in all honesty, once I learned the chemistry (equations) for determining the correct amount of EDTA, making your own nutrient solutions is amazingly cheap. For less than $200 (initial buy-in) I can make 1000s of gallons of most of this stuff before running out. And some of the micros, I may never run out (considering I am almost 60 years old).

A lot of people try to make growing as simple as possible, it is a bragging point for them. And I respect that, just like I respect those folks who like the organic path. In fairness, I do smooth out the process somewhat with automated watering styles (AutoPots, BluMats, and SIP Buckets).

But, since I am retired I have plenty of time to fiddle-fart and overthink things (that's a good thing for me). In some aspects, I treat growing this plant as though it were my job. I would have moved on from growing if I were the type of person in search of a "formula that works, so why f**k with it" sort of thing. it's the way I seem to approach any hobby or new shiny thing.

I have had these ingredients surrounding me unopened for 2 weeks because I didn't want to start without making sure that I was winging it.

Now, that I know how to calculate Disodium EDTA, I feel as though I have a new superpower.


Speaking of Comparing Nutrient Manufacturers, if anyone is interested I would be happy to show my findings. It is set up to compare my "perfect" recipe to others, so my column is repeated alongside the other manufacturers. I also drag Harley Smith's and Dr. Bugbee's numbers along as well.

I can do screenshots here no problem.

Hey buddy, hehe buddy as in HydroBuddy
I know I'm late to the show, but why don't you use chelated forms of the minerals/metals? EDDHA are the best, which dissolve in water and remain stable over a wide pH range.

 

[Bob's Auto's]

I started out more then a decade ago growing with HydroBuddy. Never had a greenthumb and being able to calculate something and get a consistent result was amazing for me. Two years ago I discovered BioTabs and never looked back. Now I just feed the bennies and let them do all the hard work.
This season though I'm going to grow me some giant zucchini's and those grow best in hydro. Couple of years ago had a plant that drank 200L in a week!
So everything HydroBuddy related will get my attention.
About the chelates. Did you read up on pH stability on the different kinds of chelates? It's to long ago for me, but I can remember EDDHA has the widest range. And most micronutrients can be bought in powder form bonded with EDDHA. If you like I can look up a list in my archive.

About the DIY process, this is what interest's me the most. Being able to do something yourself has got my attention! So, if you want to share that process with us, this would be amazing and I would definitely read that