Questions about ppm in liquid fertilizer and final nutrient solution measurements

[RookieMuffin]

Somehow my calculated ppm's don't match the measured nutrient solutons ppm... WHY?

Infos about my fertilizer (keep in mind this is just one bottle of a 3 part nutrient formula):

1 Liter fert solution weights 1.213kg

Nitrate nitrogen 4%
Ammoniacal nitrogen 1%
Total nitrogen (N) 5%

Potassium oxide (K2O) 1.3%

Boron (B) 0.01%
Calcium oxide (CaO) 6%
Copper (Cu) 0.01%
Iron (Fe) 0.12%
Manganese (Mn) 0.07%
Molybdenum (Mo) 0.002%
Zinc (Zn) 0.02%

When calculating the PPM of each element based on those values with 1ml nutrient solution for 1 litre distilled water you get this:

Nitrate nitrogen 49 ppm
Ammoniacal nitrogen 12 ppm
Total nitrogen (N) 61 ppm

Potassium oxide (K2O) 13 ppm

Boron (B) 0.1213 ppm
Calcium oxide (CaO) 73 ppm
Copper (Cu) 0.1213 ppm
Iron (Fe) 1.4558 ppm
Manganese (Mn) 0.8492 ppm
Molybdenum (Mo) 0.0243 ppm
Zinc (Zn) 0.2426 ppm

All those ppms together is 149.8145 ppm in total. (Don't make the mistake to add both total nitrogen and nitrate nitrogen/ammoniacal nitrogen)

Here is my question. When I add 1 millilitre of fertilizer to 1 liter of distilled water I would expect my EC meter to read the same value that I have calculated but that is not the case!

When I calculate the ppms as above I get about ~150 ppm for 1 ml fertilizer in 1L distilled water BUT my EC meter reads about EC 490 uS!

WHY? Let's just assume we convert EC to PPM on the 0.5 scale that would be EC 490 uS = 245 ppm

Why does my meter measure 245 ppm when there is only 150 ppm worth of nutrients in the solution based on the manufacteurers label and my calculations?

Does the manufacturer put other stuff in the liquid fertilizer which changes the reading of my EC meter (like ph buffers and so on idk what in liquid fertilizers is)?

The EC meter is not broken! It's a very good EC meter. Calibrated before measuring with lab grade EC calibration solution from the manufacteurer! So the meter is 100% working!

What is the problem here?

I was thinking I have 245 ppm (EC 490 uS) of nutrients in my reservoir but when calculating whats stated on the bottle I was only feeding 150 ppm of nutrients! Does someone know what's going on?

 

[hotrodharley]

What water are you using? Tap? Sorry. See distilled buried in all that. Have you measured the EC of your distilled water? Because virtually all distilled has “minerals” added.

 

[medidedicated]

1 bottle of a 3 part? meaning 1ml of one bottle?

What brand, GH flora trio? .5 EC is what you would get in distilled if using 1ml per gal of all 3 parts, not just one. If you clarify, I think I would understand the question, if it is 1ml of all 3 bottles then this is normal.

If it is just from one bottle, idk that is wierd. What style set up? coco or all water?

 

[Boatguy]

Somehow my calculated ppm's don't match the measured nutrient solutons ppm... WHY?

Infos about my fertilizer (keep in mind this is just one bottle of a 3 part nutrient formula):

1 Liter fert solution weights 1.213kg

Nitrate nitrogen 4%
Ammoniacal nitrogen 1%
Total nitrogen (N) 5%

Potassium oxide (K2O) 1.3%

Boron (B) 0.01%
Calcium oxide (CaO) 6%
Copper (Cu) 0.01%
Iron (Fe) 0.12%
Manganese (Mn) 0.07%
Molybdenum (Mo) 0.002%
Zinc (Zn) 0.02%

When calculating the PPM of each element based on those values with 1ml nutrient solution for 1 litre distilled water you get this:

Nitrate nitrogen 49 ppm
Ammoniacal nitrogen 12 ppm
Total nitrogen (N) 61 ppm

Potassium oxide (K2O) 13 ppm

Boron (B) 0.1213 ppm
Calcium oxide (CaO) 73 ppm
Copper (Cu) 0.1213 ppm
Iron (Fe) 1.4558 ppm
Manganese (Mn) 0.8492 ppm
Molybdenum (Mo) 0.0243 ppm
Zinc (Zn) 0.2426 ppm

All those ppms together is 149.8145 ppm in total. (Don't make the mistake to add both total nitrogen and nitrate nitrogen/ammoniacal nitrogen)

Here is my question. When I add 1 millilitre of fertilizer to 1 liter of distilled water I would expect my EC meter to read the same value that I have calculated but that is not the case!

When I calculate the ppms as above I get about ~150 ppm for 1 ml fertilizer in 1L distilled water BUT my EC meter reads about EC 490 uS!

WHY? Let's just assume we convert EC to PPM on the 0.5 scale that would be EC 490 uS = 245 ppm

Why does my meter measure 245 ppm when there is only 150 ppm worth of nutrients in the solution based on the manufacteurers label and my calculations?

Does the manufacturer put other stuff in the liquid fertilizer which changes the reading of my EC meter (like ph buffers and so on idk what in liquid fertilizers is)?

The EC meter is not broken! It's a very good EC meter. Calibrated before measuring with lab grade EC calibration solution from the manufacteurer! So the meter is 100% working!

What is the problem here?

I was thinking I have 245 ppm (EC 490 uS) of nutrients in my reservoir but when calculating whats stated on the bottle I was only feeding 150 ppm of nutrients! Does someone know what's going on?

Try measuring by weight rather than volume and see if you get the same results.
Going by ec rather than ppm would give you the most accurate results, and their would be no assumptions.

 

[PJ Diaz]

I'm thinking it's because you are basing your math from the oxide forms vs the elemental forms. As an example K20 is only 83% elemental potassium, and Ca0 is only 71% calcium, the rest is oxygen.

 

[RookieMuffin]

What water are you using? Tap? Sorry. See distilled buried in all that. Have you measured the EC of your distilled water? Because virtually all distilled has “minerals” added.

Yes I always measure the distilled water. When they add minerals it isn't distilled water anymore...

EC is always 0

1 bottle of a 3 part? meaning 1ml of one bottle?

What brand, GH flora trio? .5 EC is what you would get in distilled if using 1ml per gal of all 3 parts, not just one. If you clarify, I think I would understand the question, if it is 1ml of all 3 bottles then this is normal.

If it is just from one bottle, idk that is wierd. What style set up? coco or all water?

Yes. Just 1 bottle of the 3 part. Just the Micro bottle. And yes just 1 ml of the micro bottle in 1 Litre distilled water.

setup is DWC so all water.

Try measuring by weight rather than volume and see if you get the same results.
Going by ec rather than ppm would give you the most accurate results, and their would be no assumptions.

I always measure in EC... I just calculated the info on the bottle in ppm. But I measure my nutrient solution always in EC because there is no conversion problem when talking to other people (0.5, 0.75 scale and so on)

I'm thinking it's because you are basing your math from the oxide forms vs the elemental forms. As an example K20 is only 83% elemental potassium, and Ca0 is only 71% calcium, the rest is oxygen.

And my EC meter measures the elemantal forms PLUS the oxygen??? Is oxygen conductivity?

 

[RookieMuffin]

I'm thinking it's because you are basing your math from the oxide forms vs the elemental forms. As an example K20 is only 83% elemental potassium, and Ca0 is only 71% calcium, the rest is oxygen.

So the EC meter measures 245 ppm because it measures the oxygen too and my calculated element forms is just ~60% of that because I calculate the elemental form without the oxygen?

 

[RookieMuffin]

When I calculate whith whats on the bottle label with how much I was feeding I was feeding in total:

Nitrogen 58
Phosphorus 49
Potassium 88

Magnesium 68
Sulfur 113
Calcium 69
Iron 1.38
Boron 0.11
Manganese 0.8
Zinc 0.23
Molybdenum 0.023
Copper 0.1153

TOTAL 447.6583 PPM

And my plants were very deficient! Looking at the numbers it's understandable why they are deficient right??? It wasn't enough of all those elements right?

Now after calculating what I was feeding with the info that's on the bottle label I saw I was feeding not enough and now I'm feeding almost double and they start to look way more healthy...

Look at the number above that I was feeding would you also say it was way to low?

 

[medidedicated]

That is 3.79 ml per gal which is about what it would be with the two other bottles. I am metric as heck lol Had to do some math. .5 EC is for seedlings, mature plants I am seeing feed charts reflect about the same for coco in terms of EC. Was wondering why go dwc, but I am addicted to coco lol.

Plants can handle a nice amount of ec and speaking of Gh and your line specifically, they go 1.0 EC on most feed charts. Nice you mention this is plant related, sounds like they are doing good.

To know more than the general EC of solution I thought you need advanced equipment for which most do not have. Sounds fine to me, the liters just threw me off.

 

[RookieMuffin]

That is 3.79 ml per gal which is about what it would be with the two other bottles. I am metric as heck lol Had to do some math. .5 EC is for seedlings, mature plants I am seeing feed charts reflect about the same for coco in terms of EC. Was wondering why go dwc, but I am addicted to coco lol.

Plants can handle a nice amount of ec and speaking of Gh and your line specifically, they go 1.0 EC on most feed charts. Nice you mention this is plant related, sounds like they are doing good.

To know more than the general EC of solution I thought you need advanced equipment for which most do not have. Sounds fine to me, the liters just threw me off.

The strange thing is when I go by feeding chart or by what people say (for example EC 1.0 like u mentioned) I get heavy deficient plants.

Right now I'm feeding about 1.7 EC and they start to look better and EC is falling so they eat more than they drink...

Anyway I'm still wondering why my EC measurements are not the same as my calculated ppm from the bottle label...

By the way EC 1.0 sounds very low. I know other websites who recommend 0.8-1.3 EC for seedlings! Lol

 

[medidedicated]

The strange thing is when I go by feeding chart or by what people say (for example EC 1.0 like u mentioned) I get heavy deficient plants.

Right now I'm feeding about 1.7 EC and they start to look better and EC is falling so they eat more than they drink...

Anyway I'm still wondering why my EC measurements are not the same as my calculated ppm from the bottle label...

By the way EC 1.0 sounds very low. I know other websites who recommend 0.8-1.3 EC for seedlings! Lol

Yea depends on the brand but GH are about 1.0 to 2.5 EC. I used tap water and one part powder GH with no issues. It can be related to VPD or a host of other things that don’t happen with coco. I fed up to 2.2ec total with no calmg, no other issues. It is addicting lol.

I was under the impression with hydro the nutrients have a sufficient amount of everything and you dial it in according to your lights and temps. I thought I could help because coco is hydro and I tried diagnosing issues based on runoff and came to the conclusion described. I don’t use an ec meter anymore.

Edit: Conclusion was, hydro nutes have it all and trying to split hairs on what is going in or out was useless IME but with dwc you control ph. Visual signs are better.

 

[Coldnasty]

Somehow my calculated ppm's don't match the measured nutrient solutons ppm... WHY?

Infos about my fertilizer (keep in mind this is just one bottle of a 3 part nutrient formula):

1 Liter fert solution weights 1.213kg

Nitrate nitrogen 4%
Ammoniacal nitrogen 1%
Total nitrogen (N) 5%

Potassium oxide (K2O) 1.3%

Boron (B) 0.01%
Calcium oxide (CaO) 6%
Copper (Cu) 0.01%
Iron (Fe) 0.12%
Manganese (Mn) 0.07%
Molybdenum (Mo) 0.002%
Zinc (Zn) 0.02%

When calculating the PPM of each element based on those values with 1ml nutrient solution for 1 litre distilled water you get this:

Nitrate nitrogen 49 ppm
Ammoniacal nitrogen 12 ppm
Total nitrogen (N) 61 ppm

Potassium oxide (K2O) 13 ppm

Boron (B) 0.1213 ppm
Calcium oxide (CaO) 73 ppm
Copper (Cu) 0.1213 ppm
Iron (Fe) 1.4558 ppm
Manganese (Mn) 0.8492 ppm
Molybdenum (Mo) 0.0243 ppm
Zinc (Zn) 0.2426 ppm

All those ppms together is 149.8145 ppm in total. (Don't make the mistake to add both total nitrogen and nitrate nitrogen/ammoniacal nitrogen)

Here is my question. When I add 1 millilitre of fertilizer to 1 liter of distilled water I would expect my EC meter to read the same value that I have calculated but that is not the case!

When I calculate the ppms as above I get about ~150 ppm for 1 ml fertilizer in 1L distilled water BUT my EC meter reads about EC 490 uS!

WHY? Let's just assume we convert EC to PPM on the 0.5 scale that would be EC 490 uS = 245 ppm

Why does my meter measure 245 ppm when there is only 150 ppm worth of nutrients in the solution based on the manufacteurers label and my calculations?

Does the manufacturer put other stuff in the liquid fertilizer which changes the reading of my EC meter (like ph buffers and so on idk what in liquid fertilizers is)?

The EC meter is not broken! It's a very good EC meter. Calibrated before measuring with lab grade EC calibration solution from the manufacteurer! So the meter is 100% working!

What is the problem here?

I was thinking I have 245 ppm (EC 490 uS) of nutrients in my reservoir but when calculating whats stated on the bottle I was only feeding 150 ppm of nutrients! Does someone know what's going on?

Short and sweet: mix per the directions then dilute to proper ppm

 

[waterproof808]

Anyway I'm still wondering why my EC measurements are not the same as my calculated ppm from the bottle label...

EC/TDS meters only measure electrical conductivity of a solution and use a conversion factor to estimate PPM’s. They don’t measure the actual ppm of a solution nor do they detect any nonelectrolytes in your solution.

 

[medidedicated]

To attempt to answer your remaining question, I can add that working with flora liquid is not very precise, you need some top notch syringes and the variance in air bubbles or etc might disturb the precision you are after if you or they are not using them in a test or etc.

Weighing powder (lol) I feel is more accurate but it is all very concentrated and little variances can accour (undissolved clumps) but generally within a 0.0 scale, you are going to 0.000 , as described their goal is probably to just have everything you need on a 0.0 scale, or even 0.00 EC as I seen messing around with my ec meter.

My question to maybe help find your answer is, why does it need to be so percise? Is this a precision question, or help with sick plants? future sick plants? Most work with 0.0 scale and get lost when I toss in one more digit.

Edit: I would ask the manufacture directly, they can best answer what impurities or exact variables are causing your slight difference in measurement which ec meters arent a report of everything in it.

 

[Hollatchaboy]

The strange thing is when I go by feeding chart or by what people say (for example EC 1.0 like u mentioned) I get heavy deficient plants.







Right now I'm feeding about 1.7 EC and they start to look better and EC is falling so they eat more than they drink...







Anyway I'm still wondering why my EC measurements are not the same as my calculated ppm from the bottle label...







By the way EC 1.0 sounds very low. I know other websites who recommend 0.8-1.3 EC for seedlings! Lol

Just run flora nova bloom, or the Lucas formula. If you want powdered, run maxi bloom. It's much easier using only 1 or 2 parts. It makes it easier to make adjustments. Flora gro just screws everything up.

 

[RookieMuffin]

Yea depends on the brand but GH are about 1.0 to 2.5 EC. I used tap water and one part powder GH with no issues. It can be related to VPD or a host of other things that don’t happen with coco. I fed up to 2.2ec total with no calmg, no other issues. It is addicting lol.

I was under the impression with hydro the nutrients have a sufficient amount of everything and you dial it in according to your lights and temps. I thought I could help because coco is hydro and I tried diagnosing issues based on runoff and came to the conclusion described. I don’t use an ec meter anymore.

Edit: Conclusion was, hydro nutes have it all and trying to split hairs on what is going in or out was useless IME but with dwc you control ph. Visual signs are better.

Since hydro nutes have it all I stopped using supplements. Now if they look deficient I just add more nutes lol! As long as they look good I don't care how high the EC is lol!

 

[RookieMuffin]

EC/TDS meters only measure electrical conductivity of a solution and use a conversion factor to estimate PPM’s. They don’t measure the actual ppm of a solution nor do they detect any nonelectrolytes in your solution.

I don't even measure ppms. I only measure the EC.

I've calculated the ppms based on what the bottle states on the labels! And based on what I've calculated I was not feeding enough so I increased the EC.

 

[RookieMuffin]

To attempt to answer your remaining question, I can add that working with flora liquid is not very precise, you need some top notch syringes and the variance in air bubbles or etc might disturb the precision you are after if you or they are not using them in a test or etc.

Weighing powder (lol) I feel is more accurate but it is all very concentrated and little variances can accour (undissolved clumps) but generally within a 0.0 scale, you are going to 0.000 , as described their goal is probably to just have everything you need on a 0.0 scale, or even 0.00 EC as I seen messing around with my ec meter.

My question to maybe help find your answer is, why does it need to be so percise? Is this a precision question, or help with sick plants? future sick plants? Most work with 0.0 scale and get lost when I toss in one more digit.

Edit: I would ask the manufacture directly, they can best answer what impurities or exact variables are causing your slight difference in measurement which ec meters arent a report of everything in it.

I use medical syringes to measure the nute amount.

Yes that's true weighing powder is more accurate... I'm thinking about mixing my own nutrient powder... But first I will use up all my liquid nutes so they don't go to waste lol!

It was a questions because I was wondering why my plants were deficient. I did all what people say. They always recommended something like EC 1.0 but my plants got deficient so I calculated what's in my nutrient solution when I'm at 1.0 EC and what the label of my nutrients say. After calculating how much of each nutrient is in my nutrient reservoir I came to the conclusion that it's not enought at EC 1.0 and I need a minimum of 1.7 to reach a good NPK ppm (and the rest of the nutrients of course).

My plants were sick. And with low EC (1.0 for example) like people recommended they were still deficient.

EC 1.0 stats:
N 58
P 49
K 88
Mg 68
Ca 69

EC 1.7 stats:
N 96
P 82
K 147
Mg 114
Ca 115

Now with EC 1.7 they start to look better.

But the initial question was: Why I have calculated fewer ppms than my EC meter measures (I measure in EC but I've calculated in ppm)

I've calculated the nutrients ppm with the information on my fertilizer bottle and it says 750ppm for all nutrients.

But I've measured 1.7 EC. Why do I measure more EC than the actual nutrients in there?

I've calculated 750ppm and measured 1.7 EC. So convert both to the same I have calculated 1.5 EC but I'm measuring 1.7EC. Why? Meter is calibrated and working fine. I was wondering if there is something in the fertilizer thats changing the EC but is not mentioned on the label like ph buffers or something. I measure 0.2EC more than I've calculated based on what the fertilizer bottle says.

 

[RookieMuffin]

Just run flora nova bloom, or the Lucas formula. If you want powdered, run maxi bloom. It's much easier using only 1 or 2 parts. It makes it easier to make adjustments. Flora gro just screws everything up.

I already use the lucas formula!

But people recommend everywhere to use a lower EC like 1.0 so I've diluted the EC from full 100% Lucas to about 45-50% strength to get EC 1.0.

But I get deficiencies when I dilute it that low but people say that lower EC is better but when I do it my plants get deficient. So I've calculated how much of each nutrient I have in my reservoir when using the 45-50% strength and it's way to low in my eyes. So I went back to a higher EC. Minimum 1.7 right now.

 

[Hollatchaboy]

I already use the lucas formula!



But people recommend everywhere to use a lower EC like 1.0 so I've diluted the EC from full 100% Lucas to about 45-50% strength to get EC 1.0.



But I get deficiencies when I dilute it that low but people say that lower EC is better but when I do it my plants get deficient. So I've calculated how much of each nutrient I have in my reservoir when using the 45-50% strength and it's way to low in my eyes. So I went back to a higher EC. Minimum 1.7 right now.

I use Lucas for dwc, but right now I'm using the h3ad formula in coco. 1.7 ec is what I get when I'm done mixing. My plants love it, and I can't take it lower without deficiency. FTW! Lol