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Q.How Do I Create Specific NPK Ratios In A Gallon Of Water?

Zone Saint Helens, OR 97051 | BeachRock added on December 5, 2020 | Answered

My Nitrogen is 20-0-0 with a total Nitrogen of 20% Ammoniacal Nitrogen derived from Ammonium Sulfate. My Phosphorus is 9-61-0 with a total Nitrogen of 9% Ammoniacal Nitrogen and 61% of available Phosphate derived from Monoammonium Phosphate. My Potassium is 0-0-50 with 50% soluble Potash derived from Potassium Sulfate. All three are 100% water soluble. A plant has different requirements for NPK ratios depending on their stage of life, and each species of plant has different requirements compared to others. I want to be able to combine these products together to create different ratios based on the requirements I’m trying to meet. If I’m trying to create a 2-1-2 ratio, or a 4-2-3 or 5-10-7 ratio, how do I determine what part of a teaspoon measurement is necessary from each nutrient to add to 1 gallon of water?

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Certified GKH Gardening Expert
Answered on December 7, 2020

Make sure to check the instructions for mixing on the package. You will have to do a little math from there. Some nutrients have instructions for mixing per gallon, and some don't. If your does, you will have a much easier time trying to determine the amount needed. If not, then you will need to do some more math to get to your answer.

You might not get an exact number, but you will have to keep adjusting the ratio until you get as close as possible. Keep in mind that you can be pretty far off and still have a decently effective fertilizer.

First, find out how much you need for the dose, according to the package. Then divide the dose until you reach a number that is close to the one that you need. For example- You want to get nitrogen from 20 to 5. This will mean that you need to divide the original dose by 4. Continue with all of the numbers and fertilizers until you get as close as possible.

An alternative will be using a balanced fertilizer that has all three values the same. The plant will take what it needs, when it needs it. As long as you test the pH and nutrient content of your medium frequently and ensure that the pH doesn't swing too far, the plant will be happy.

Here are some articles for extra information:



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