N-P-K question

[babystarbud]

this probably sound like a daft question, but i just wanted to make sure.

NPK is expressed as a percentage, and given that most if not all ferts need diluting... is that percentage the final % when the waters added?
like a 10-10-10 fert that says to add x ammount per litre of water,
that water will then be 10% nitrogen etc. ?


reason i ask is that i got some new fert today, 10-25-25,
if i put half the ammount in the reccomended water,
would that make it 5-12.5-12.5?

[babystarbud]

whats confusing me is, if you did it the other way round, and used a double dose of fert, it wold be 50% P, 50%k, and 20% N....you cant have 120%of fert in water????

i must be missing somthing here lol

[canuck grower]

Ok I will not claim to know the answer, but my understanding was that the numbers are a percentage of the fert before dilution.

So if you have 10-25-25 then that is 10% N, and 25% each of P and K. Take 100ml of that and it contains about 10ml N, and 25ml each P and K. Dilute that with 900ml water and you have 10ml N / 1000ml = 0.01% N, and 25ml / 1000ml = 0.025% P and K in the final mix.

They are effectively ratios of N, P and K. I hope this is correct, and until someone more knowledgeable confirms it don't take it as truth.

-canuck :jointsmile:

[Garden Knowm]

I have always viewed those numbers as the ratio...

[babystarbud]

a bit of googling has revealed that the NPK ratings are the percentage as packaged, NOT the final product when diluted to reccomended ammount.

"Ok, so your confused. On some nutrients the NPK seems low, like 2-1-3. And on others it can be high, 14-24-16. Whats the deal here?

Nutrient values (N-P-K)are expressed as total percentage of weight as packaged. Organic nutrients typically tend to have lower npk values than chemical nutrients. Don't let this fool you, you can easily burn plants if you overfertilize!

Powder nutrients tend to have higher NPK values than liquid nutrients because they are not already partially diluted with water. Do not let low N-P-K values fool you, what really matters is how strong these nutrients are when diluted to recommended levels ie: thier tds/ppm/ms/eC/cf. For example SuperVeg will give you a tds of around 1000 ppm when used according to directions, while Aquafeed "V" Powder will have a tds of around 600 ppm if used as recommended. "

taken from http://www.living-learning.com/faq/npk.htm

seems to be the geneal consensus, which make sence.
although, confusingly i did find a few sites that said it was a ratio...
if that were the case though, it would mean a 1-2.5-2.5 is the same stregnth as a 10-25-25, which didnt really sit right with me...

why i didnt just google itin the first place ill never know,
google...the answer to all life questions, lol

[bejay]

you should consider it as a ratio of available npk as it doesnt really provide any relavent info to the strength once diluted or mixed according to the directions, and 1-2.5-2.5 is equivalent to 10-25-25 and the lower strength 1-2.5-2.5 could just as easily have a higher or lower ppm than the 10-25-25 when diluted following the directions, but if you are using a meter to begin with you should be able to obtain similiar ppm from both fertilizers.