Real meaning of N-P-K?

Hollatchaboy said:

Iirc, a 1 lb. bag of dry amendment, 4-4-4, would be 4% nitrogen, 4% phosphorous, 4% potassium. So would a teaspoon.

I believe cannabis prefers a close balance of ferts.

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Not exactly, at least in the US.

Nitrogen is listed as actual nitrogen percentage, but the P and K percentages are for the oxide, not the elemental weights.

So a 10-10-10 for example is

10% N
10% P2O5 (4.4% P)
10% K2O (8.3% K)

It's elemental label would be 10-4-8

I may be wrong, but I think the EU and/or Australia lists both the oxide and elemental percentages on the bag, unlike the US.

Billy the Mountain said:

Not exactly, at least in the US.

Nitrogen is listed as actual nitrogen percentage, but the P and K percentages are for the oxide, not the elemental weights.

So a 10-10-10 for example is

10% N
10% P2O5 (4.4% P)
10% K2O (8.3% K)

It's elemental label would be 10-4-8

I may be wrong, but I think the EU and/or Australia lists both the oxide and elemental percentages on the bag, unlike the US.

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Roger that!

Billy the Mountain said:

Not exactly, at least in the US.

Nitrogen is listed as actual nitrogen percentage, but the P and K percentages are for the oxide, not the elemental weights.

So a 10-10-10 for example is

10% N
10% P2O5 (4.4% P)
10% K2O (8.3% K)

It's elemental label would be 10-4-8

I may be wrong, but I think the EU and/or Australia lists both the oxide and elemental percentages on the bag, unlike the US.

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Awesome! I didn't realize that! Thanks!

Billy the Mountain said:

Not exactly, at least in the US.

Nitrogen is listed as actual nitrogen percentage, but the P and K percentages are for the oxide, not the elemental weights.

So a 10-10-10 for example is

10% N
10% P2O5 (4.4% P)
10% K2O (8.3% K)

It's elemental label would be 10-4-8

I may be wrong, but I think the EU and/or Australia lists both the oxide and elemental percentages on the bag, unlike the US.

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Why you recon they don't just put the elemental weight?

Hollatchaboy said:

Why you recon they don't just put the elemental weight?

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IIRC, it's a vestige of the measuring techniques used a century ago and too ingrained to change.

Tomatoesonly said:

Dude you come in here asking basic questions and when someone answers correctly, you say "If that actually had merit"???
You are too ill informed on the topic to be telling people their answer is wrong.
There are huge amounts of info from the farming community, think actual food products, that have used these numbers and from which, is how the labeling even began.

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Whoa what are you talking about? How is my logic flawed? Again this isn't a "help me figure how to feed my plants". Just following the basics I've done that no problem. I just want to know the scientific specifics. Which Hollatchaboy answered well I believe. That nute numbering refers to how much of NPK is in any volume, be it a tsp or a cup. What amneziaHaze said was yeah if it's 42 on nitrogen then he uses 1/3 the dosage. You tomatoes are missing the purpose of the question. AmneziaHaze isn't wrong on if you got a nute with high numbers using less will reduce burn. But my question isn't about that. It was about what those numbers truly mean. Which again I believe the consensus is it's a %/volume.

I meant no disrespect and got nothing but love and appreciation for every growmie, especially those(almost all) that have more experience than mine. Don't be so quick to fire up, anyone whose followed my previous grow and posts knows I'm not here to be a prick. My bad damn

Billy the Mountain said:

Not exactly, at least in the US.

Nitrogen is listed as actual nitrogen percentage, but the P and K percentages are for the oxide, not the elemental weights.

So a 10-10-10 for example is

10% N
10% P2O5 (4.4% P)
10% K2O (8.3% K)

It's elemental label would be 10-4-8

I may be wrong, but I think the EU and/or Australia lists both the oxide and elemental percentages on the bag, unlike the US.

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This is what I'm talking about about!!! Those little extras/intricacies that get down to the nitty gritty of what these labels truly are.

Just FYI I thank everyone who has responded. Only way I'll get better and smarter at this is healthy discussions.

Just happened to read this from the beginning... concerning the H2O2 or bleach... one part,,, has no meaning. One part bleach to 9 parts water,, means you make a 10% solution of your bleach in water. To a chemist "bleach" has no definitive meaning either. Chemically it too (my Clorox jug) is a mixture of 4.5% Sodium Hypochlorite in 95.5% of a liquid (most likely water). Like Sodium Hypochlorite (bleach), H2O2 (hydrogen peroxide) is also sold in diluted form... ie 12% Hydrogen peroxide is 12 parts H2O2 (hydrogen peroxide) and 88 parts H20 (water). Another way of stating this would be " a 12 part solution of hydrogen peroxide in 100 total parts of a liquid solution. Further clarification (or mudding the water) would be whether this solution is made up of parts by volume or parts by weight. This solution could also be referred to as a 120,000 ppm (parts per million) solution of H2O2. Basic math that can get confusing as hell. LOL

As far as the NPK numbers go they are a ratio. I could be wrong here, but I beleive that a tablespoon of 16:16:16 added to a gallon of water will behave like four tablespoons of 4:4:4 added to a gallon of water.

DaveT said:

Just happened to read this from the beginning... concerning the H2O2 or bleach... one part,,, has no meaning. One part bleach to 9 parts water,, means you make a 10% solution of your bleach in water. To a chemist "bleach" has no definitive meaning either. Chemically it too (my Clorox jug) is a mixture of 4.5% Sodium Hypochlorite in 95.5% of a liquid (most likely water). Like Sodium Hypochlorite (bleach), H2O2 (hydrogen peroxide) is also sold in diluted form... ie 12% Hydrogen peroxide is 12 parts H2O2 (hydrogen peroxide) and 88 parts H20 (water). Another way of stating this would be " a 12 part solution of hydrogen peroxide in 100 total parts of a liquid solution. Further clarification (or mudding the water) would be whether this solution is made up of parts by volume or parts by weight. This solution could also be referred to as a 120,000 ppm (parts per million) solution of H2O2. Basic math that can get confusing as hell. LOL

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I just understand .3 grams pool shock to 10 gallons water. 2.5cc’s kln per half gallon water. How much bleach or h202 did they intend on telling me to add to 3 gallons water? How many ML’s or cups ? Thats all I understand.

It quickly got harder trying to google my question, many different answers making less and less sense. I never figured it out but I just said F it and put a nice amount of pool shock and dwell, done.

I moved on to a way more reliable clone method anyway.

I add 10 to 20 ml of 12% H2O2 to my 4 gallon reservoir daily. Seems to be used up within 24 hours.