Calculating EC/PPM/TDS from nutrient compositions

[ThrowMeOut]

Hi all, long time lurker first time poster.

I'm trying to figure out if there is a way to within reason calculate the EC (or PPM, TDS, whatever flavor you may choose) of a nutrient product based off it's label composition & reported SG/Density (mostly gotten from MSDS info).
(I understand this changes from batch to batch and that reported product composition doesn't accurately match their actual composition)

I've read and digested pretty much all I can find on here and in various corners of the internet on how to attempt to calculate EC, read all the threads there are from Renfro and many others, as well as what i can digest out of hydrobuddy's documentation.

From what I can gather, aside from trying to back-build how Hydrobuddy does it, you'll never really accurately get the calculated PPM or EC to match measured PPM/EC?
I've gotten to a point where I can within a margin of error calculate elemental EC/PPM and my calculations seem to match other people's work, but as I would imagine most people who have delved in to this subject have found, it never matches up with what we get when physically measuring EC.

TLDR, just wondering if anyone has ever figured out a somewhat simple yet within reason accurate way to match measured EC with elemental EC?

Side note: I also realize this is a relatively contested subject and that EC measurements are best used as a reference once you have a grasp of what your plants actually *want*

 

[twentyeight.threefive]

Hi all, long time lurker first time poster.

I'm trying to figure out if there is a way to within reason calculate the EC (or PPM, TDS, whatever flavor you may choose) of a nutrient product based off it's label composition & reported SG/Density (mostly gotten from MSDS info).
(I understand this changes from batch to batch and that reported product composition doesn't accurately match their actual composition)

I've read and digested pretty much all I can find on here and in various corners of the internet on how to attempt to calculate EC, read all the threads there are from Renfro and many others, as well as what i can digest out of hydrobuddy's documentation.

From what I can gather, aside from trying to back-build how Hydrobuddy does it, you'll never really accurately get the calculated PPM or EC to match measured PPM/EC?
I've gotten to a point where I can within a margin of error calculate elemental EC/PPM and my calculations seem to match other people's work, but as I would imagine most people who have delved in to this subject have found, it never matches up with what we get when physically measuring EC.

TLDR, just wondering if anyone has ever figured out a somewhat simple yet within reason accurate way to match measured EC with elemental EC?

Side note: I also realize this is a relatively contested subject and that EC measurements are best used as a reference once you have a grasp of what your plants actually *want*

I guess it might be interesting just to know, but seems like an awful lot of work for something that isn't very relevant.

Using Renfro's spreadsheet I'd imagine if all the math was correct you should be able to find an accurate measurement.

 

[ThrowMeOut]

I guess it might be interesting just to know, but seems like an awful lot of work for something that isn't very relevant.

Using Renfro's spreadsheet I'd imagine if all the math was correct you should be able to find an accurate measurement.

I based a lot of what I was trying to accomplish off of Renfro's work and that was a really great starting point, but I think I've hit a bit of a wall.
Short of finding a magical database of products and their measured ECs, it seems like a lot more work than I need to be bothering with.

I was hoping to see if I could figure out what measured EC a set of plants like given a certain nutrient profile, then in the future be able to make changes to a nutrient schedule and be able to easily and accurately calculate the same composition profile with new nutrients. It sort of works, just not the way I wanted it to.

 

[twentyeight.threefive]

I based a lot of what I was trying to accomplish off of Renfro's work and that was a really great starting point, but I think I've hit a bit of a wall.
Short of finding a magical database of products and their measured ECs, it seems like a lot more work than I need to be bothering with.

I was hoping to see if I could figure out what measured EC a set of plants like given a certain nutrient profile, then in the future be able to make changes to a nutrient schedule and be able to easily and accurately calculate the same composition profile with new nutrients. It sort of works, just not the way I wanted it to.

You'd have to run clones to know what nutrient profile that specific plant likes and I'm not sure why you'd want to switch nutrients after figuring that out.

Just seems like an enormous amount of work for no reason.

 

[rkymtnman]

Hi all, long time lurker first time poster.

I'm trying to figure out if there is a way to within reason calculate the EC (or PPM, TDS, whatever flavor you may choose) of a nutrient product based off it's label composition & reported SG/Density (mostly gotten from MSDS info).
(I understand this changes from batch to batch and that reported product composition doesn't accurately match their actual composition)

I've read and digested pretty much all I can find on here and in various corners of the internet on how to attempt to calculate EC, read all the threads there are from Renfro and many others, as well as what i can digest out of hydrobuddy's documentation.

From what I can gather, aside from trying to back-build how Hydrobuddy does it, you'll never really accurately get the calculated PPM or EC to match measured PPM/EC?
I've gotten to a point where I can within a margin of error calculate elemental EC/PPM and my calculations seem to match other people's work, but as I would imagine most people who have delved in to this subject have found, it never matches up with what we get when physically measuring EC.

TLDR, just wondering if anyone has ever figured out a somewhat simple yet within reason accurate way to match measured EC with elemental EC?

Side note: I also realize this is a relatively contested subject and that EC measurements are best used as a reference once you have a grasp of what your plants actually *want*

what's your target npkcamg?

 

[ThrowMeOut]

what's your target npkcamg?

That's part of why I'm after all of this, it depends on how you look at things.
My roughly calculated elemental (actual, not going off of product label %s) Veg NPK is ~3.8:1.8:4, K:Ca:Mg 4:2.9.1 and mid flower ranges more towards 1.9:3.2:4.2, K:Ca:Mg 4:3.2:1.1
Numbers are all a bit skewed though because of things like pH Down additives, but overall this seems to be working pretty well so far.

Beyond my own interests I had been hoping to compile basically a database of nutrient products and their makeups and sort out a way to basically say given a set of nutrients and their "schedule", calculate the proportions needed to achieve a set EC or PPM, but I think like twentyeight.threefive said, this is probably a lot more work than it's worth

 

[rkymtnman]

i'm not interested in ec, just the "best" ratios for myself.

i'm not sure there is one either. i've tried a bunch and they all seem to work fairly well.

 

[smokey0418]

I find that bottle value ec of botanicare would be rocket fuel fuel for me at over 2 ec grown in rdwc.
Way too much unless you like a good burn.
I feed to what my plants eat , starting low working my way to the sweet spot.

 

[ThrowMeOut]

i'm not interested in ec, just the "best" ratios for myself.

i'm not sure there is one either. i've tried a bunch and they all seem to work fairly well.

that seems like the most healthy to approach it all. i drift in to the chemistry side of things but then just get too bogged down in that and lose sight of what the plants actually want

 

[PJ Diaz]

That's part of why I'm after all of this, it depends on how you look at things.
My roughly calculated elemental (actual, not going off of product label %s) Veg NPK is ~3.8:1.8:4, K:Ca:Mg 4:2.9.1 and mid flower ranges more towards 1.9:3.2:4.2, K:Ca:Mg 4:3.2:1.1
Numbers are all a bit skewed though because of things like pH Down additives, but overall this seems to be working pretty well so far.

Beyond my own interests I had been hoping to compile basically a database of nutrient products and their makeups and sort out a way to basically say given a set of nutrients and their "schedule", calculate the proportions needed to achieve a set EC or PPM, but I think like twentyeight.threefive said, this is probably a lot more work than it's worth

With NPK ratings, N is elemental but P & K are in their oxide forms, so you have to convert them to elemental. Check the attached pdf on how to do what you want to do.

 

[ThrowMeOut]

With NPK ratings, N is elemental but P & K are in their oxide forms, so you have to convert them to elemental. Check the attached pdf on how to do what you want to do.

Thanks for that! Though I knew that part though that does remind me of one thing I've always wondered, why is N always considered "special"? By that I mean, N is typically present as NH4, NH3 etc yet everywhere I've seen is treated as 100% N and not treated the same way K (K20 converted to elemental K) and P (P205 converted to elemental P) are treated? Does this have to do with how plants absorb nitrogen & other oxides needing to be broken down first?

 

[PJ Diaz]

Thanks for that! Though I knew that part though that does remind me of one thing I've always wondered, why is N always considered "special"? By that I mean, N is typically present as NH4, NH3 etc yet everywhere I've seen is treated as 100% N and not treated the same way K (K20 converted to elemental K) and P (P205 converted to elemental P) are treated? Does this have to do with how plants absorb nitrogen & other oxides needing to be broken down first?

I asked that question once myself, but have unfortunately forgotten the answer lol.

 

[ThrowMeOut]

I asked that question once myself, but have unfortunately forgotten the answer lol.

lol fair enough, that's how most of this stuff goes for me