What PPM range for Dyna-Gro All Pro?

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Steve Johnson
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Re: What PPM range for Dyna-Gro All Pro?

Post by Steve Johnson »

4d3d3d3 wrote: Sun Jun 12, 2022 7:54 pmSorry don't really mean to nitpick, just something I've noticed that often gets omitted in fert ppm calculations. Good fert advice though and I appreciate your posts on the subject.
No need to apologize -- I've been in the precision measuring business for 35 years, and you're giving me the kind of more precise info I find both useful and interesting. And it's nice to know that I'm not over-fertilizing my cacti -- thanks! :)
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C And D
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Re: What PPM range for Dyna-Gro All Pro?

Post by C And D »

Just wanted to point out one thing I didn't see mentioned (I could have missed it)

You need to take a baseline ppm of your regular water first, then subtract that value from your ppm with Fertilizer for the correct value

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Steve Johnson
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Re: What PPM range for Dyna-Gro All Pro?

Post by Steve Johnson »

C And D wrote: Mon Jun 13, 2022 5:43 pmJust wanted to point out one thing I didn't see mentioned (I could have missed it)

You need to take a baseline ppm of your regular water first, then subtract that value from your ppm with Fertilizer for the correct value
I learned the ppm calculation method I use from Iann years ago. Getting a baseline ppm of the water makes sense, but he never mentioned it.
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Re: What PPM range for Dyna-Gro All Pro?

Post by C And D »

I use "Grow More" 20-20-20

around $60 for 25 lbs
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jerrytheplater
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Re: What PPM range for Dyna-Gro All Pro?

Post by jerrytheplater »

4d3d3d3 wrote: Sun Jun 12, 2022 7:54 pm
Steve Johnson wrote: Sat May 28, 2022 9:34 am
jerrytheplater wrote: Sat May 28, 2022 2:53 am Steve. The OP specifically asked for the concentration of the Dyna-Gro, not any one particular nutrient. I asked for clarification, and that is what he wanted to know. He has not replied since.
Since he did reply, I just wanted to follow through on what you said about diluting 1.05 ml Dyna-Gro/3785 ml water to get an NPK total of 277 ppm. When I asked you to check my math, I went about it all wrong, so let's try again...

I'm diluting 1/2 tsp. Dyna Gro 7-7-7 per gallon of water, and here are my ppm calculations for the N, elemental P, and elemental K being taken up by the cacti:

1/2 tsp. goes into a gallon 1536 times
N .07/1536 x 1,000,000 = 46 ppm
P .03052/1536 x 1,000,000 = 20 ppm
K .0581/1536 x 1,000,000 = 38 ppm
NPK total = 104 ppm.

You're diluting a little less than 1/4 tsp. of the Dyna Gro Foliage Pro 9-3-6 per gallon, so I don't know how you're getting 277 ppm.
You're assuming the density of the fertilizer is the same as that of water, but it's slightly higher. Dyna-gro 7-7-7 has a specific gravity of 1.3, meaning each mL of fert is 1.3 g.

0.5 tsp = 2.5 mL, so 0.5 tsp of fertilizer weighs 0.5 x 1.3 = 3.25 g.
7% of this is 3.25 g is "N", so 7% x 3.25 g = 0.2275 g of N = 227.5 mg of N

PPM = mg of solute / kg of solvent = 227.5 mg of N / 3.785 kg (the weight of 1 gal of water) = 60.1 ppm of N. Basically what you got if you multiply 46 by 1.3, the density of the fertilizer.

P: 26 ppm elemental
K: 49 ppm elemental
NPK total = 135 ppm

Sorry don't really mean to nitpick, just something I've noticed that often gets omitted in fert ppm calculations. Good fert advice though and I appreciate your posts on the subject
Hi 4d3

In answer to the question "What does the term Parts per Million mean? on the Dyna-Gro website FAQ https://dyna-gro.com/faq/ They answer "It is a measurement of the concentration of elements in the nutrient solution. One ppm is one part by weight of the mineral in one million parts of solution. For example 9% nitrogen in Foliage-Pro is 90,000 ppm. When you dilute this 1 tsp./gal. (1:750) you will be applying 120 ppm nitrogen."

A few things to notice: 1) They round off when calculating dilutions 1 tsp/gal = 1:750 instead of 1:768. 90,000 / 750 = 120 ppm N instead of 90,000 / 768 = 117 ppm N. And that is not a significant error when fertilizing plants.

2) Dyna-Gro is using Volume to Volume dilutions. In their calculation they are saying that each volume/part of their fertilizer contains 9% by weight N, etc. They don't tell you to weigh out their fertilizer when using it. The commercial growers I know use injectors to fertilize their plants. They stick the hose into the barrel of fertilizer concentrate and it sucks up a proportion set by the grower as the need may be.

The SDS sheet does say the density of the fertilizer is 1.39 gm/cm^3 or 11.57 lbs per gallon.
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