Help a stoner with math!

Basic Growing Info
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Hi guys. Math isn’t my strong suit but I am trying to figure this out. A bit too stoned for this so I would love a second opinion.

Let’s say a fertilizer brand is 20-20-20 and says to add 1 Tbsp per gallon of soil. Assuming the soil has no nutrients in it, what mathematical formula would I use to figure this out?

I am thinking if one tbsp has a 20-20-20 rating than once I dilute it 256 times (256 tbsp in a gallon) it comes out at 20 divided by 256 = .07

So my soil would have an npk of .07-.07-.07 right? Or am I way too stoned to try to be doing math right now?

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It would still be 20-20-20 because those numbers are the ratio. Same as if you add two scoops it’s not 40-40-40 :wink:

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Buddy I think you are higher than me.

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I can assure you I am not… However, that doesn’t mean I’m right

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Don’t do math… the sativa is lying to you… :rofl: :+1:

Bad Sativa… bad…

Cheers
G

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Either you aren’t thinking straight, or maybe I didn’t explain myself properly.

The ratio could be 1-1-1 or 20-20-20. They are the same thing. That is ratio, not strength. So that 40-40-40 fertilizer if you mix it in half with sand becomes 20-20-20. The ratio didn’t change, but the strength did.

I am saying if I add one tbsp of 20-20-20 to a gallon of soil what does the nutrient value within that soil become? It definitely doesn’t turn that gallon of soil into 20-20-20 fertilizer. It becomes diluted, not the ratio, but the strength. If a gallon of soilless mix is comprised of 255 tbsp of a substance with a nutrient value of 0, and one tbsp with a nutrient value of 20-20-20 then what is the total nutrient value of that gallon of soil? It definitely is not 20-20-20.

Fox Farms soil has an NPK of .30- .30-.05. I am trying to figure out the correct math where I can accurately formulate my own soils npk levels after I amend it. I am not necessarily trying to mimic that, but I am trying to learn the math to reach the numbers I want within my soil.

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I’d like to tag @ifish to help out with your issue. :blush::v:t4:

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Riiiggghhhttt… I get it. Yeah, that obviously makes sense. Second “day” on nights, so my brain is a little foggy. I would say your math is spot on then. But once again, I’m dumb, so I don’t really know

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Hey, no worries. You aren’t the only one. I wouldn’t be asking other stoners to double check my math if I was a rocket scientist.

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What I said did technically kind of make sense, even though it wasn’t correct. I’ll chalk that up as a solid win :stuck_out_tongue_winking_eye:

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When it says 20-20-20 that means that 20% of each nitrogen, phosphorus, and potassium make up the today weight so in a 100 grams, 20 grams would be nitrogen, 20 grams phosphorus and 20 grams potassium and 40 grams of others

So yes if your adding 1 tbsp of something that is present in 20% of that scoop then you would take that 1/5 or .20 of a tablespoon and divide it by the 256 in a gallon and that would give you .0007

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Just to throw a wrench in, if considering say how much that works out to elmentally NPK wise vs label wise

A 10-10-10 is actually a 10-4.4-8.3 when talking elementally due to how nutrients are labeled.

Also typically most nutrients will say whatever grams per gal or liter = so many ppm oh nitrogen and that’s what you go from.

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Not sure I follow in this, look at any fertilizer bag on the back and those npk numbers are the percent of that element in the total weight of the bag, how does a 10%-10%-10% translate to a 10-8.3-4.4?

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See that is my original thought, but when doing that math in my head it led to crazy numbers. I mean how much alfalfa at 2-1-2 would I need to get my K up to .12 in a soilless mix with no outside nutrients added? I ended up getting insane results and assuming I had to be wrong!

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.12(5) is an 8th of total weight

U would need to add 154-160 tbsp of 2-1-2 in a gallon fo achieve the .12-12.5% nutrient rating

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Traditional ratio ( what’s on bag or bottle ) is the amount of raw material used in relation to each other
The elemental ratio is when water mixes with the traditional ratio , what’s then is avail to the plant ( ppm ) and then that’s turned into elemental ratio

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I’m going of off back of the bags showing “guaranteed analysis” with the npk percentages that match the front of the bag, for example Dr earth 4-6-3, under guaranteed analysis showing 4% 6% 3% for the npk

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When they say add 1 tsp to a gallon , is that to gallon of water or soil

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This is a hypothetical question. But the answer is soil.

On a real world, simple explanation, I want to know how to calculate my nutrient values in my own blended mixes.

So if I have one gallon of soilless mix made up of coco coir, vermiculite, perlite, etc. A medium that is completely devoid of nutrients and then I add amounts of a fertilizer with a known value I want to know how do I calculate that value the way Fox Farms or any other brand puts a guaranteed analysis on the bag.

I just made the medium have a value of 0, and the fertilizer be an even 20-20-20 for simplicity.

A real world example would be blood meal is 15-0-0 and says add 1 tbsp per gallon of soil. Well what the hell does that equate to in relation to other brands that I am aware of? If I know Fox Farms sells their Happy Frog brand at 0.30 N and I want to be able to replicate that, how much blood meal (at 15-0-0) would I need to add to a soilless mix with a nutrient profile of 0.0 N in order to make it 0.30 N?

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Are you going salts or organic
Salts avail instantly
Organics more like over time ( breaking down )