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."

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

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2) Once you have the millimolar concentration, you add up the 4 numbers:

Fe: 4.298E-02
Mn: 9.101E-03
Zn: 3.363E-03
Cu: 4.721E-03
-------------------
= 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

---

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

---

That leaves you with the grams required.

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

---

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

5.06 x 1.00
= 5.06 grams

---

If it it were for 0.5 liters, then it would be :
5.06 x 0.5
=2.53 grams

---

Below I'll show an example (not final) of my "template" worksheet:

Items in RED are to remind me to double check things that can change:

 

[ExNavyInSTL]

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

---

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.

---

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

---

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

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 nutrtients, 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 tomatos.

 

[ExNavyInSTL]

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

---

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.

---

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

---

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.

 

[Delps8]

Howdy from the Left Coast!

I read this the other day and meant to vector in @farside05. Have you seen his threads on DIY nutes?

 

[farside05]

Welcome to the rabbit hole of DIY nutes @ExNavyInSTL.

First a word of caution, the program you are using and its creator are kind of dirty words around here. I don't know all the particulars, but there have been conflicts between the person/program in question and the ownership/management of this forum, so mentioning either may get your posts removed and/or edited.

I don't use that program. I tried it on a couple occasions and found it buggy and difficult to use so I built my own Excel spreadsheet to make all my calculations. I also bought all my heavy metals as individual chelated elements rather than buy salts, a combination of the heavy metal and Sulfur, ie Iron Sulfate, Manganese Sulfate, etc. I believe the start up costs in buying all the ingredients is the #1 deterrent that keeps more people from going the DIY route. I have about $300 invested in my supplies but it will make years worth of fertilizer.

I've been building my own for several years now. I refer to them as Farside Nutrients Fertilizer, or FN Fertilizer for short. I've tweaked the recipes over time and am currently on Version 3. It looks like this:

FNv3 powder list.jpg

• farside05
• Feb 6, 2023

V3 Breakdown.jpg

• farside05
• Jan 23, 2023

* Weights of powders above are to make a gallon of concentrated fertilizer solution which is then fed at a rate of 10ml per gallon for mature plants.

Comparing your proposed mix to mine, you may be a little short on K. Adding in a Silica supplement (ie Potassium Silicate) would provide Silica and help bump that K a bit. You also have an abundance of Ca, Mg, and S. One of the benefits of having all the individual chelated heavy metals is that you're able to control the S more easily since they aren't combined with the extra Sulfates.

It doesn't look like a problem with your current proposal, but when making concentrated nutrient solutions, make sure that your Sulfates and Phosphates are in a separate product from the product that contains Calcium or you may get precipitation.

 

[ExNavyInSTL]

@farside05

Thank you so much for that.

Edited to Add: Thanks for the warning about the man who shan't be named. Like most folks, I would imagine he is the first finding for people like me.

---

I knew there were others out there doing this who have worked out the kinks (for the most part).

Let me tell you the "why" of some of my numbers.

It started with this video by Dr. Nirit Bernstein. Here she is giving a lecture to folks in the Cornell University Hemp/Cannabis program. It discusses the optimum amount of N-P-K and Mg.

Dr. B is the senior research scientist and head, Cannabis Physiology and Agronomy Lab, Volcani Center, Ministry of Agriculture, Israel.

This is why I named my recipe, Israeli Mix.

---

​

Nirit Bernstein: The power of nutrient management for optimizing Cannabis yield quantity and quality​

Video is at the end.

I'll give you the gist of Dr. Bernstein's findings (as I interpret them). It is going to be somewhat counter to what is currently theorized on the forums. I expect to hear a "No way, that's Bullshit," from folks out there once reading, But I encourage everyone to hear her out in the video.

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): 35 or so ppm in Veg and in Flower is needed. Friendly range of 35 - 140 ppm, but you are damaging the quality of the end product the higher you go.

---

My Calcium is high because I grow in Coco. I already feed the Coco as well as the plant, so I thought why not skip the supplemental 3ml a gallon of cal/mg added already for the Coco?

My Mg is elevated because I was trying to keep Mg in the 2:1 with Ca.

Keep in mind, I come to my opinions based on various things I read, but there is so much conflicting info. At some, you just have to plant your flag and see what happens.

Believe me, I wouldn't fight to the death over my thinking. Heck, I wouldn't even thumb wrestle.

---

 

[ExNavyInSTL]

@farside05

One other area that I need help with is my preservative.

Do you know the rule of thumb for how much Sodium Benzoate?

I've seen 0.25% - 0.1%, but I don't know if that is for the volume of liquid or the weight of the mass.

I have also seen 0.1 - 0.3 grams, but I am not sure what to tie that to as well.

 

[farside05]

I'll give you the gist of Dr. Bernstein's findings (as I interpret them). It is going to be somewhat counter to what is currently theorized on the forums. I expect to hear a "No way, that's Bullshit," from folks out there once reading, But I encourage everyone to hear her out in the video.

Been swamped at work, I'll have to check the video out later.

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

Agreed. Most commercial lines fall in this same range, except for Fox Farms which is about 200ppm N at full strength. I also do not cut N in flower, which flies in the face of many beliefs. Under 120ppm and you generally get yellowing plants. Over 175ppm and you start to see leaf tip burn.

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.

Agreed. This is what led me to start making my own nutes. Many commercial lines are P heavy. Fox Farms being the worst at over 100ppm P. I've run experiments using as little as 19ppm through flower with no adverse effects.

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

Here is where I would disagree. I've encountered K deficiencies at a level of 150ppm K. 180-220 seems to be where I don't have any issues. At levels of 280-320ppm K we've seen plants self destruct in a matter of days. From lush to crispy almost overnight.

Magnesium (elemental): 35 or so ppm in Veg and in Flower is needed. Friendly range of 35 - 140 ppm, but you are damaging the quality of the end product the higher you go.


My Calcium is high because I grow in Coco. I already feed the Coco as well as the plant, so I thought why not skip the supplemental 3ml a gallon of cal/mg added already for the Coco?

My Mg is elevated because I was trying to keep Mg in the 2:1 with Ca.

Depending on who's advice you go with, the ratio should be between 3:1 to 2:1 Ca to Mg. When I embarked on my learning of all this, I followed Dave Neal's (CEO of Dyna-Gro) advice that he stated on the Dude Grow's podcast. He said that the ratio should be 3:1. Therefore, I shoot for 100ppm Ca and 33ppm Mg. The fertilizer company Jack's has a ratio of 1:1 if you use their 3-2-1 program. FYI, their 3-2-1 doesn't refer to N-P-K but rather rough weights of 3 different fertilizer products.

I don't grow in coco, but rather in a peat based soil-less mix which is also a blank canvas. Are you using tap, well, or RO water? Tap and well water will also contain Ca.

Keep in mind, I come to my opinions based on various things I read, but there is so much conflicting info. At some, you just have to plant your flag and see what happens.

There's so much conflicting, or plain outright incorrect, info out there its staggering.

@farside05

One other area that I need help with is my preservative.

Do you know the rule of thumb for how much Sodium Benzoate?

I've seen 0.25% - 0.1%, but I don't know if that is for the volume of liquid or the weight of the mass.

I have also seen 0.1 - 0.3 grams, but I am not sure what to tie that to as well.

I've never used any preservative to advise. I make gallons of concentrated fertilizer solutions which last me about 3 months and have had no issues with spoilage while they wait to be used.

 

[ExNavyInSTL]

Addressed inside your comments.

Agreed. Most commercial lines fall in this same range, except for Fox Farms which is about 200ppm N at full strength. I also do not cut N in flower, which flies in the face of many beliefs. Under 120ppm and you generally get yellowing plants. Over 175ppm and you start to see leaf tip burn.

Bug thumbs up on this!!!

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Agreed. This is what led me to start making my own nutes. Many commercial lines are P heavy. Fox Farms being the worst at over 100ppm P. I've run experiments using as little as 19ppm through flower with no adverse effects.

I'll attach my recent homework, for the non-nerds, which shows an across the line comparisons.

Here is where I would disagree. I've encountered K deficiencies at a level of 150ppm K. 180-220 seems to be where I don't have any issues. At levels of 280-320ppm K we've seen plants self destruct in a matter of days. From lush to crispy almost overnight.

I'm starting at the ground floor on most of this. I've only been growing for 1-1/2 years. But, I know nothing beats experience. So, I may adjust my K up. I don't have anything set in stone yet. I am definiely listening. I just want to lock in on a winning program, or close enough so that my experiements from that baseline are less scary.

---

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Depending on who's advice you go with, the ratio should be between 3:1 to 2:1 Ca to Mg. When I embarked on my learning of all this, I followed Dave Neal's (CEO of Dyna-Gro) advice that he stated on the Dude Grow's podcast. He said that the ratio should be 3:1. Therefore, I shoot for 100ppm Ca and 33ppm Mg. The fertilizer company Jack's has a ratio of 1:1 if you use their 3-2-1 program. FYI, their 3-2-1 doesn't refer to N-P-K but rather rough weights of 3 different fertilizer products.

I'm ok with 3:1. That would put me closer to Dr. Bernstein's claim. However, I do want to get a better feel for Calcium and Coco. The fact that Coco grabs calcium for itself (even if buffered) worries me. Although, I think the more important worry is more about proper pH levels. I tend to believe deficiencies and toxities are more related to the pH situation, and not the abundance or lack of the nutrients.

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I don't grow in coco, but rather in a peat based soil-less mix which is also a blank canvas. Are you using tap, well, or RO water? Tap and well water will also contain Ca.

I use RO water. I do this because I have a whole-house water-softening setup.

There's so much conflicting, or plain outright incorrect, info out there its staggering.



I've never used any preservative to advise. I make gallons of concentrated fertilizer solutions which last me about 3 months and have had no issues with spoilage while they wait to be used.

---

Regarding Sodium Benzoate: The good news here is that I just noticed my answer is right on the label. How about that? : )

It says to use only in Concentrated Stock of 100:1 and up. General Use: 0.1 - 0.3 grams per liter. Or 0.38 - 1.13 grams per gallon. That's simple enough.

In the beginning, I plan to start with 250ml or 0.5 liters until I get my sea legs. After that, I may make gallons at a time.

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Here is a small sample of comparisons I have ongoing. I'll add yours to it later. : )

 

[Delps8]

I believe it's in one of Bugbee's documents on res management that he says pretty much the same thing. While pH at 5.8 is "optimal", there's a fair amount of wiggle room. Second, nutrient issues are far more often caused by over abundance of chemicals than by a lack of chemicals.

A really helpful document re. res management is "Nutrient Management in Recirculating Hydroponic Culture" and "Principles of Nutrient and Water Management for Indoor Agriculture", was helpful informative, as well.

"Optimization of N, P, K for soilless production of Cannabis sativa in the flowering stage using response surface analysis" is a good read, too. I think @Farside looked at this a while back and had some comments about their methodology.

 

[farside05]

Here is a small sample of comparisons I have ongoing. I'll add yours to it later. : )

Another spreadsheet geek like myself! I don't feel as alone now...lol Over HERE are some more breakdowns you can add to that sheet if you like.

There's a number of different growers here that are using numbers similar to mine, they are just doing it by blending different "off the shelf" products rather than individual salts.

 

[ExNavyInSTL]

Yes, another spreadsheet geek.

I like to joke that I am this way because my mother potty-trained me at gunpoint.


I appreciate the other nutrient specs.

I bought another cheap magnetic stirrer today, once it is in my hands I'm going to make my first batch.

I did heed your advice and have tweaked my recipe some.

Another spreadsheet geek like myself! I don't feel as alone now...lol Over HERE are some more breakdowns you can add to that sheet if you like.

There's a number of different growers here that are using numbers similar to mine, they are just doing it by blending different "off the shelf" products rather than individual salts.

 

[ExNavyInSTL]

@farside05

Alright, you got me thinking. So, I made some adjustments.

Now that I have had time to really go over your v3, I have a few questions:

Zn - What was your reasoning for 1.32 on your Zn?
Harley says 0.5 - 1, and Bugbee has it at 0.02

Mn - Same Question for Mn at 1.32?
Those guys have it at 0.5 - 1.0 (H), and 0.2 (B)

I could go lower on the Moly-B, and H & B are right in line with your lower number.

However, the Mfr's look like this for Mo:

0.145 Mega Crop
0.126 Jack's
0.119 Master Blend
0.016 FloraFlex is similar in Veg
0.016 Flex is even lower in Flower
0.114 Athena (V)
0.013 Athena (F) - they get down there in Flower.

Mo - What made you comfortable going so low with Mo?

BTW: Harley thinks like you with 0.01 - 0.05. Dr. B goes even lower with 9.6 pbb.

I just love this stuff. Thanks for the back and forth.

 

[bluter]

i'm impressed with anyone who has the patience and interest to dive into this.

@farside05 i think that hb spreadsheet has been tweaked a bit over time. it gets a fair amount of traction in other places now.

 

[farside05]

@farside05

Alright, you got me thinking. So, I made some adjustments.

I like the looks of that now, especially as a fertilizer to compliment RO.

Now that I have had time to really go over your v3, I have a few questions:

Zn - What was your reasoning for 1.32 on your Zn?
Harley says 0.5 - 1, and Bugbee has it at 0.02

Mn - Same Question for Mn at 1.32?
Those guys have it at 0.5 - 1.0 (H), and 0.2 (B)

Mo - What made you comfortable going so low with Mo?

BTW: Harley thinks like you with 0.01 - 0.05. Dr. B goes even lower with 9.6 pbb.

My micro decisions were made in a very unscientific fashion. When I first went down this road, I wanted to start off on the cheaper end of the spectrum. Rather than buy all the individual chelated micros, I bought a product by Greenway Biotech called Micro Green. I used it for the micro component and then designed Part A and B around it. I had great success with that strategy. Rather than reinvent the wheel, when time came to buy all the individual chelated elements, I just reverse engineered Micro Green. I've got all the components now and could tweak the micros as I see fit, but haven't tried to fix what's not broken.

 

[ExNavyInSTL]

Thanks again. This has been fun.

My next CustomHydro purchase will include Potassium Silicate.

I like the looks of that now, especially as a fertilizer to compliment RO.



My micro decisions were made in a very unscientific fashion. When I first went down this road, I wanted to start off on the cheaper end of the spectrum. Rather than buy all the individual chelated micros, I bought a product by Greenway Biotech called Micro Green. I used it for the micro component and then designed Part A and B around it. I had great success with that strategy. Rather than reinvent the wheel, when time came to buy all the individual chelated elements, I just reverse engineered Micro Green. I've got all the components now and could tweak the micros as I see fit, but haven't tried to fix what's not broken.

 

[ExNavyInSTL]

@farside05

Made my first batch of 0.5L of 200:1 (A&B).

I think everything went well. However, there was some precipitate the next morning. It had "shards" like objects that definitely float to the surface. They seemed gel-like but with a shake broke up easily and then returned to the surface of the flask.

I wonder if that was the Sodium Benzoate? It was an SOB to dissolve. The beaker looked like a snow globe for a long time.

I haven't tested it yet. I'll make up a liter and then check PPM and E.C. compared to the program's estimates.

These are the items I mixed and in the order instructed.

 

[ExNavyInSTL]

@farside05

Alright, Testing is complete.

Let's look at A & B individually.

"A" Solution (1L):
Predicted: 1.334 E.C.
Actual: 1.648 E.C.
5.35 pH

"B" Solution (1L):
Predicted: 0.781 E.C.
Actual: 1.085 E.C.
4.61 pH

Once A & B were combined in 2 x :
Predicted: 1.782 E.C.
Actual: 1.353 E.C.
4.51 pH

That's quite a bit off. I'll make a second batch to make sure I didn't mess up a measurement.

I divided the mixes into 2 x 1000ml beakers and brought the mixtures up to 6.0 pH.

Then I fed 1L (each) to 2 limping-along Tomato Plants.

They are my wife's tomatoes, so I'll write back soon if I am looking for a new place to live.

 

[ExNavyInSTL]

I don't know what the heck I did yesterday.

Today, I made another liter, using 5ml of A & B, and got the following:

2.41 EC
4.38 pH

That is hotter than I wanted, based on the estimate provided. But it is easy enough to dial in the rest of the way with more water, or a little less than 5ml.

Overall, I am happy.

 

[farside05]

Maybe something to consider. Rather than work things out to a specific injector ratio of say 200:1, I work my numbers so 10ml of fertilizer of each different fertilizer solution/product is a full dose. Knowing that I have about 150ppm of N in a full dose, and there's 10ml in a full dose, that's 15ml of N per ml. So say I have a plant that's not fully mature and I want to feed it around 90ppm of N, I can just dose all the products at 6ml each.