There is no such thing as an NPK ratio ...

spurr · May 23, 2011

I know some may find this thread a waste of time, but I thought it was worth pointing out:

A ratio is comprised of two 'things', like A to B, cookies to milk, etc., three variables does not a ratio make.

That means there is no such thing as the N-P-K (or K-Ca-Mg) ratio, and besides, NPK only tells about percent (by weight) of the element. The N, P and K, have nothing to do with each other in terms of ratios as listed on the label.

I know the use of the word "ratio" in terms of NPK is common in the cannabis world. I just thought I may point this issue out ...

spurr · May 23, 2011

In horticulture there is the concept of ratios in terms of element X affecting uptake of element Y; but again, that is for only two elements, not three.

When someone writes the "NPK ratio", or the "KCaMg ratio", often what is meant is the amount of each element relative to each other. Often this is found via ppm of elements in solution. There are a few method one can use to find those 'ratios', IIRC. I use a method I found from Cornell, or somewhere similar (I can't find the reference right now), as below:

x ppm = x
y ppm = y
z ppm = z
element with lowest ppm = L

x/L = X
y/L = Y
z/L = Z

Ex., 200 ppm K, 150 ppm Ca and 50 ppm Mg gives a 'ratio' of 4-3-1:

200/50 = 4
150/50 = 3
50/50 = 1

Avenger · May 23, 2011

Yer off yer rocker Spurr, welcome back BTW.

The reason we use ratio instead of the simpler fraction, is so that we may compare more than two things in the simplest mathmatical form.

Merriam Webster Definition of RATIO
1a : the indicated quotient of two mathematical expressions
b : the relationship in quantity, amount, or size between two or more things : proportion

krunchbubble · May 23, 2011

Avenger said:
Yer off yer rocker Spurr,

spurr · May 23, 2011

Hey Avenger,

Yer off yer rocker Spurr, welcome back BTW.

I have been at times, off my rocker, but not on this one, me thinks. I could be wrong, but I'm pretty sure I'm not.

A ratio is only for two 'things', not more. That means N

:K can't be a ratio, even though in our lexicon in terms of fertilizers in a working solution (e.x., rez) it is called a ratio.

The numbers for N-P-K on a bottle of fertilizer isn't a ratio, either.

P.S. thanks for the welcome back note.

311devon · May 23, 2011

Youre kinda splttin hairs a bit here dont ya think?......As far as a ratio only being comprised of two parts. This is false. I mix paint as an auto refinisher in 8:4:1, 8:2:1 and many other 3 part ratios all the time. These parts being basecoat:solvent:hardener respectively. You can have mutliple parts in a ratio. This is refered to as a compound ratio. This is in the dictonary.

NPK Ratio refers to a substances quantity of n, p, and k as a ratio relative to the other components as a whole in a given substance.

So, if we are expressing our ratio as a percentage, then we have 100 part system. If our npk is 10-10-10 then in our 100 part system we have 10 parts n, 10 parts p, 10 parts k and 70 parts of whatever else it is made of. (if the "whatever else" is more than one component they are viewed together as one).

This does not provide us with an absolute quantitive value for our NPK. It does however provide us with enough to use a lil math and a scale to figure that out if desired.

Just my $.02....

Hammerhead · May 23, 2011

lol I have never referred to NPK as a ratio or have herd any use that term. Where did you see a ratio?? Its not on any of my Nutrient bottles.

Avenger · May 23, 2011

The numbers for N-P-K on a bottle of fertilizer isn't a ratio, either.

For certain there.

How would you skin this cat? if not to give the relationship between K, Ca, Mg ppm as a three part ratio?

spurr · May 23, 2011

311devon said:
Youre kinda splttin hairs a bit here dont ya think?......

My OP starting sentence:

"I know some may find this thread a waste of time, but I thought it was worth pointing out:"

311devon said:
As far as a ratio only being comprised of two parts. This is false. I mix paint as an auto refinisher in 8:4:1, 8:2:1 and many other 3 part ratios all the time.

These parts being basecoat:solvent:hardener respectively. You can have mutliple parts in a ratio. This is refered to as a compound ratio. This is in the dictonary.

You are not referring to what this thread is about. You are referring to parts, I am referring to ratios, in mathematics. To get a ratio of N

you divide N with P; but to use a compound ratio, as you suggest, for N

:K would give nothing like what one expects:

Compound ratio (i.e., the product of two or more ratios) of K:Ca:Mg at ppm of 200:150:50 is 375,094 (rounded up)

Ex.,

K:Ca = 200/150 is 1.333
K:Mg = 200/50 is 4
Ca:Mg = 150/50 is 3

then,

200*200*150 = 6,000,000
1.333*4*3 = 15.996

thus, the ratio compounded of these is 6,000,000/15.996 = 375,093.7734.

311devon said:
NPK Ratio refers to a substances quantity of n, p, and k as a ratio relative to the other components as a whole in a given substance.

There is an important point here, the two 'forms' of NPK 'ratio': (1) that on a bottle of fertilizer; and (2) that found from ppm of fertilizer working solution (fertigation water). The former does in no way have anything to do with relativity, the latterf does.

The NPK 'ratio', ex., between 100 ppm N, 50 ppm P and 200 ppm K is not a ratio, and that's not what is listed as N-P-K on the front of the fertilizer label.

311devon said:
So, if we are expressing our ratio as a percentage, then we have 100 part system. If our npk is 10-10-10 then in our 100 part system we have 10 parts n, 10 parts p, 10 parts k and 70 parts of whatever else it is made of. (if the "whatever else" is more than one component they are viewed together as one).

In the case of fertilizer label laws, kind of. There is no ratio involved (e.x., N/K or P/K), it's only percentage. I.e., a fertilizer with 10-10-10 has 10% by weight made up of N, P and K.

311devon said:
This does not provide us with an absolute quantitive value for our NPK. It does however provide us with enough to use a lil math and a scale to figure that out if desired.

Just my $.02....

The N-P-K on the front of the label is of little value other than to tell a ball bark guide to amounts of N, P and K. It's the elemental ppm that matters, and ratios therein, ex., N:K.

spurr · May 23, 2011

Hammerhead said:
lol I have never referred to NPK as a ratio or have herd any use that term. Where did you see a ratio?? Its not on any of my Nutrient bottles.

Many growers term NPK as a ratio (KCaMg, too), either as the numbers from a fertilizer label (on the front), or as a 'ratio' they found comparing elemental ppm of N, P and K.

The numbers on front of the nutrient bottle is not a ratio by any means.

spurr · May 23, 2011

Avenger said:
How would you skin this cat? if not to give the relationship between K, Ca, Mg ppm as a three part ratio?

I prefer to use true ratios, as K:Ca, K:Mg and Ca:Mg, rather than K:Ca:Mg. The true ratios give more fine grained info. But I also use K:Ca:Mg, with the method I wrote above (i.e., K/L, Ca/L, Mg/L), to get more info about cation levels relative to each other.

While we are on this topic, the idea of an ideal Ca:Mg ratio is a unicorn. There is no ideal Ca:Mg ratio, anywhere from ~1.5 to 8 (even above 10) is fine. The claim of an ideal ratio of 3 is not correct for hydro or soilless.

Basically I started this thread to point out that the word "ratio" is misused by many growers. Just a heads up I guess, trying to keep us on the 'bleeding edge' and all that

311devon · May 23, 2011

Bro, you are one literal dude. Nothing wrong with that. I had not read your second post when i wrote mine, and with the proper context in mind, i see your point.

However, being a guy who uses K.i.S.S. method, i grow nugs that get me high as fuck. Plus, since i'm perpetual, i'm never more than a week from harvest and dont care if i milk every gpw or potential trichome outta each girl i cut. This is all very esoteric to me.

With that said, I'm glad there are guys like you out there with time and resources to make it easier for guys like me to get 90% or so of what the genetics i paid for are capable of.

spurr · May 23, 2011

311devon said:
Bro, you are one literal dude. Nothing wrong with that. I had not read your second post when i wrote mine, and with the proper context in mind, i see your point.

However, being a guy who uses K.i.S.S. method, i grow nugs that get me high as fuck. Plus, since i'm perpetual, i'm never more than a week from harvest and dont care if i milk every gpw or potential trichome outta each girl i cut. This is all very esoteric to me.

With that said, I'm glad there are guys like you out there with time and resources to make it easier for guys like me to get 90% or so of what the genetics i paid for are capable of.

mad librettist · May 23, 2011

There is no such thing as an NPK ratio ...

spuurrrrrr!

missed you buddy. thanks for blowing my mind again even though I grow organic.

LouDog420 · May 23, 2011

NPK numbers and the like, I consider proportions...

This much N/product...
This much P/product...
This much K/product...

I guess they could be considered ratios when viewing the numbers as a ratio of N ions to the other ions and compounds in the product.

Split those hairs and keep toking on those sativas bro :laughing:

Hammerhead · May 23, 2011

spurr said:
Many growers term NPK as a ratio (KCaMg, too), either as the numbers from a fertilizer label (on the front), or as a 'ratio' they found comparing elemental ppm of N, P and K.

The numbers on front of the nutrient bottle is not a ratio by any means.

I totally agree. That's why I asked you what I did. No one uses that as a ratio I have no clue where you got that idea from. Maybe the people you talk to do.

I just rechecked all of my Nutrient and boosters none of them have any information regarding ratio

spurr · May 23, 2011

Hammerhead said:
I totally agree. That's why I asked you what I did. No one uses that as a ratio I have no clue where you got that idea from. Maybe the people you talk to do.

The term ratio, used as NPK ratio or KCaMg ratio, is widely used in the cannabis world and beyond, including at ICmag.

spurr · May 23, 2011

mad librettist said:
spuurrrrrr!

missed you buddy. thanks for blowing my mind again even though I grow organic.

Hammerhead · May 23, 2011

You say widly used I would disagree and say there are very few that think that. This would be the first post I have read that anyone uses NPK as a ratio

ShroomDr · May 24, 2011

Im no math teacher but im pretty sure these three are all equal and all the same ratios

4:2:1
8:4:2
800:400:200

I sincerely doubt someone who teaches math would say those 3 examples are not RATIOS.
They make take exception with the last two not being taken down the lowest denominator, but all three are still labeled as RATIOS.

I too prefer to talk about 1vs1 ratios, it makes things easier to follow. No one wants to try to decipher

8:4.3:1.6, but i still think that mess is called a RATIO.

There is no such thing as an NPK ratio ...

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