I work in a tissue culture laboratory and we have several custom made medias that I would like to know the NPK ratio for. How would I work that out? For example, one of the medias contains 7-8 different chemicals (along with sugar, agar etc). I know this is a gardening website but I am assuming the method would be the same? Apologies if I am wrong.

I'm not sure that's an at-home thing. I think you would have to take your samples to a soil lab for a chemical analysis.

The manufacturer of the various ingredients in your media would have to provide the chemical analysis of their product. There is no way for a user to discover that info from some generic
ingredient label. In some cases of substances used to feed animals or people or to be used as soil amendments, the Dept. of Agriculture and other government bodies publish tables of nutrient composition. I imagine it would otherwise be quite difficult to come up with meaningful NPK figures for mixtures that are not specifically marketed as fertilizers. Perhaps a commercial laboratory could help you out with this, as they do with soil samples.

Do you not know if you're using the best medium, or not trust what the vendor tells you?
I think this is way outside the experience of almost every user here.

I feel like a tissue culture lab would have a lot more specific knowledge than almost every user here.

Googled this out of curiosity
https://labassociates.com/6-pl....

https://labassociates.com/8-co...

First, sugar and agar have no NPK value. You have to have available nitrogen, phosphorus, or potassium. You need to check with whoever made your culture medium to see what they used in the preparation.

You can not calculate the NPK value. If you have a soil sample your county extension agent can run a simple test to determine the value for you..

Hey all, thank you for your responses.
We make our media from scratch at the lab so I know everything that goes into it. However, we've never had to calculate the NPK before so I'm unsure how to do it.

Some media's contain both Potassium Phosphate and Potassium Sulphate. Knowing the chemicals and the amount used, is there some sort of calculation I can do or is it much more involved than that?

I suspect much more involved than that but organic chemistry was my waterloo.

For garden/horticulture use, we look for the grade on the package, expressed as three numbers-
Such as NPK 18-4-10
Which is just a calculation of the percentage by weight of each individual nutrients.

https://hgic.clemson.edu/facts...

Clemson University Cooperative Extension Service said:
If the net weight of this 18-4-10 fertilizer was 100 lbs., then there are 18 pounds of nitrogen (N), 4 pounds of phosphate (P2O5), and 10 pounds of potash (K2O).

To find the ratio of N and P and K, however, in that same bag, make another 3 calculations

Clemson University Cooperative Extension Service said:
These three numbers also represent a ratio that describes the relative proportions of N, P2O5, and K2O in a fertilizer. Calculate the fertilizer ratio by dividing the numbers in the fertilizer grade by the lowest number in the fertilizer grade. For example, the ratio of this 18-4-10 fertilizer is 4.5:1:2.5 or 4.5 parts nitrogen to 1 part phosphate to 4.5 parts potash.

https://hgic.clemson.edu/facts...

So, after you read that article, that's what we know as gardeners: the grade and then we can manually figure out the RATIO OF NPK of a fertilizer product.

This ratio is likely what you are seeking, but you need it for your MS media?
This article may help with ratios:
How to Calculate a Fertilizer Ratio
https://extension.psu.edu/how-...


I'm sure I'm not understanding your needs... but you know the amounts you are using of these macronutrients?

Plant Cell Technology said:
The nutrient composition of MS media:

Macronutrient:
The macronutrients in MS medium are the primary elements that plants need in large amounts for their growth and development. They include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). These macronutrients are provided in the form of inorganic salts, such as ammonium nitrate (NH4NO3), potassium phosphate (KH2PO4), calcium chloride (CaCl2), magnesium sulfate (MgSO4), and potassium sulfate (K2SO4).
Link:
https://www.plantcelltechnolog...

I would consult a local university horticulture or chemistry lab professional to help find the info you need.

Thank you. That's all really good information.
I understand how to do a standard NPK calculation from the back of a fertiliser container. What I would like to know is how to do it if I have a group of chemicals such as:

Ammonium Nitrate 1650mg/L
Potassium Phosphate 330mg/L
Potassium Nitrate 2000mg/L
Potassium Phosphate 323mg/L
Calcium Phosphate 44mg/L
(All this is made up for the example)

How do I calculate the NPK?

The chemicals above contain different forms of N, P and K and I can't find online how to factor all that in together.

The calculations use weight as a general basis. You would need to transform your mg/L into the total weight of the amount of actual chemical that you use. Then you would need to find out how much of that weight is usable N, P and/or K. Then you would need to calculate that weight into the total weight of the final solution. Remember the total weight would also include that of the nutrient additive you are calculating for. And, I wouldn't be surprised if there are addition steps needed. I am not a chemist.

Yes, finding out how to calculate percentage of N (for instance) is in a molecule of Ammonium sulfate is difficult, IMO. I am not a chemist, but I would assume you could use the weight of a nitrogen atom against that of the molecule. You will need to investigate the validity of this assumption. Remember also that the macro nutrient percentages given on a fertilizer label is not consistent. The percentage of nitrogen is given as N. The percentage of potassium is give as K₂O, whether or not the K in the product is in that form or not. So additional calculations may be needed. Be wary, too, that a chemical may be offered in a hydrated form (or possibly in some other form), usually for shelf stability, thus requiring another set of calculations.

So my whole point here is that this could become incredibly complex. Yes, if you could find an aforementioned table, or similars, as aids, it'd be helpful, but is beyond anyone here, IMO. Good luck!