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

[YosemiteSam]

Well this thread will certainly change everything.

 

[ShroomDr]

Reading though again, i see its lexicon and punctuation you are taking exceptions with Spurr. i like you, you split hairs and i really like that, i just think youve gone the wrong direction here.

First, like Hammerhead said, ive never seen anyone call it an N-P-K 'ratio'. Maybe they do it all the time and ive just been ambivalent. And i totally agree this would be incorrect (given the way way P and K are calculated (P=43%,K=83%, or something close to that).

Perhaps your argument (other that there cannot be a '3 figure' ratio) is that when people compare K:Ca:Mg they are using the K listed from the N-P-K, not its elemental K, and i would again agree this would be incorrect. I would hope, and i assume, that anyone who is that interested in a K:Ca:Mg ratio should know that the K listed as N-P-K still has the atomic weight of the O factored in, although perhaps this is a bad assumption on my part.
Someone who is trying to read (and understand) labels better know punctuation is key. NPK = N-P-K but both are different than N:K. And an elemental listing like 100N 100P 200K = N:K = 1:1:2.

Ive never seen anyone list these 3 in this manner, but K-Ca-Mg is different than K:Ca:Mg. And 40K 20Ca 10Mg = K:Ca:Mg = 4:2:1. But again, i do see how some could try to get the ratio from the K-Ca-Mg listing, which is incorrect.

I like when you split hairs, i think i see what you were trying to go after, but i think the '3 or more figured ratio' exists, no matter how shitty/sloppy it may be. Lots of cooking recipes have 4 parts this 2 parts that, etc.

 

[habeeb]

well I might be guilty of using the word ratio, I might have..

anyways, spurr, what are your thoughts on NPK values and what they should be?

I am in the camp though, Ca is always used way to high. I might have seen one Ca def when I started growing and that's the only time.. and I also think Mg is usually way to low then what people think... but who knows, my thoughts are always changing. and would love to hear some discussions again on Ca: Mg ratios ( did I use it right? ) haha

 

[chemoboi]

The number of posts in this thread may be expressed as a ratio of the relative boredom of IC Mag members to the available discussion topics on the site. Wait...what?

 

[Avenger]

Just for you Spur, i will use the term "extended ratio" when ever I make reference to an elemental ppm comparison between the major cations, such as K:Ca:Mg 4:2:1 TO 3:2:1 FTW with may jane!

 

[desertsquirrel]

all the boys back in one room again? Sweet. Glad your back spurr.

 

[Dicomaco]

I'm confused, maybe it's because English isn't my first language. I'm still not sure how to use the ratio on my AN Grow container.

On the Grow label it says 2-1-6, exactly what does it tell me about N-P-K?

That there is 3 times more Potassium than Nitrogen in it?

 

[ShroomDr]

On the Grow label it says 2-1-6, exactly what does it tell me about N-P-K?

That there is 3 times more Potassium than Nitrogen in it?

No that is incorrect.
-

A (20-20-20) fertilizer is not equal parts N:K.
P and K are calculated as P2O5 and K2O.

The label factors in the atomic weight of oxygen.

P is 43.6% of what is labeled.

P=31 O=16.

P2O5 = (2 x 31) + (5 x 16) = 142.
P = (2 x 31)=62.
62/142 = 43.6% P in P2O5.


K is 83% of what is labeled.

K=39 O=16.

K2O = (2 x 39) + (16) = 94.
K = (2 x 39)=78.
78/94 = 83% K in K2O.

 

[spurr]

On the Grow label it says 2-1-6, exactly what does it tell me about N-P-K?

It means of the total weight of the fertilizer, 2% is comprised of N (ammonicial plus nitrate), 1% is P2O5 (~0.436% P) and 6% is K2O (~5% K).

 

[Avinash.miles]

def splitting hairs here, but that's ok bcuz im pretty sure u r technically right.
people just don like hearing it....

 

[ran outta love]

Lol two pages of discussion but no one has mentioned the correct term yet.

It's NPK rating, at least on Wikipedia: http://en.wikipedia.org/wiki/NPK_rating.

Funnily enough, when googling for the terms, the incorrect one "NPK ratio" gets over three times the hits of the correct one. Therefore the term NPK ratio could be argued as being well established. It's certainly well understood. Some people use "NPK ratios", they are probably mathematicians.

But I will try to remember to use the correct one from now on.