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How To Mix A Powerful 0-20-20 Fertilizer At Home (And Why You May Need It)

Just how much do you know about 0-20-20 fertilizer? What do these numbers represent? If you’re a novice gardener, one of the things you should familiarize yourself with is the three essential macronutrients included in fertilizers. These are nitrogen, phosphorus, and potassium. 

These three numbers represent the measure of each macronutrient in the fertilizer. Hence, 0-20-20 fertilizer means there is zero nitrogen content, 20 percent phosphorus, and 20 percent potassium

In the following post, I’ll explain how you can mix a 0-20-20 fertilizer and the benefits these minerals offer to your garden.

What Do You Need To Mix A 0-20-20 Fertilizer?

  • Straight edge shovel (for mixing)
  • Filler material
  • Bucket (with lid) or a few bags
  • Permanent marking pen
  • Tarp
  • Gardening gloves
  • Shoes or gardening boots

While you can garden in any pair of shoes, it’s often better to choose footwear designed for this activity, such as boots. I recommend gardening boots over other footwear because they’re rugged, waterproof, and very easy to clean with a quick spray of a hose. 

It’s important to add filler material when making the fertilizer. This helps evenly disperse the concentration of the fertilizer’s active ingredients: phosphorus and potassium. In excessive amounts, these active ingredients can burn delicate roots and stems. 

Step By Step Instructions – How To Mix A 0-20-20 Fertilizer


Here is a step-by-step guide on how to properly mix a 0-20-20 fertilizer:

  1. Decide Where You Want To Apply It

    The first step is determining where you want to apply the fertilizer.

    Depending on how you’ve designed your garden and the type of plants it contains, you’ll be able to decide where to apply fertilizer. In addition to the type of plants, you’ll also need to account for the current season.

    Determining which plants to fertilize and at what time is crucial.

    This is because some plants, like ferns, are highly sensitive to over-fertilization. Ferns also need lower amounts of nitrogen, as excessive amounts can cause leaves to yellow and wilt.

    When it comes to season, the majority of perennials require fertilizing in early spring. Annuals, on the other hand, should be fed a high-phosphorus fertilizer at least three or four times during the growing season.

    Lawns require a second application of fertilizer in the early fall, whereas trees and shrubs need fertilizing in the spring and fall.

  2. Calculate The Required Amount Of The Ingredients

    Understanding the amount of nutrient required in a particular area can be somewhat confusing, especially when you’re making your own blend.

    But it doesn’t have to be.
    As this article by Aggie Horticulture at Texas A&M University suggests, the first thing that you may want to do is perform a soil test to determine the phosphorus and potassium requirements for the type of soil in your garden or grass species you already have or plan to plant in your lawn.

    If you already know what your plants need, you can skip the soil test.

    Once you’ve determined the recommended amounts, you can work out how much of each ingredient to add to your blend.

    Don’t worry, I will guide you through the math and give you some examples down below.

  3. Buy The Ingredients

    all purpose mop 28potassium 29-fertilizer
    image credit:

    Once you’ve figured out the quantity of fertilizer you need to apply on your lawn or garden, the next step is to purchase each ingredient. You should look for a phosphorous-only fertilizer and a potassium-only fertilizer.

    The phosphorus-based fertilizer should have a ratio of 0-20-0 and the potassium-based one should have a ratio of 0-0-20.

    I recommend buying each ingredient separately, as it makes it easier to mix. But, if you go for a fertilizer that contains both phosphorus and potassium, ensure that it has equal portions of each. As an example, you can pick a fertilizer with 0% nitrogen, 5% phosphorous, and 5% potassium.

    You’ll also need to look for filler material. As we calculated above, phosphorus and potassium minerals only make up 40% of the fertilizer mix and you still need 60% of some other material to complete your fertilizer.

    The filler material can be anything from sand to sawdust, granular limestone, peat moss, or sterile soil.

    The type of filler material you use will depend on the goal you’re trying to achieve. For instance, if you want to prevent the growth of weeds, grass clippings are an excellent option. Sawdust filler is great for improving the soil’s ability to retain moisture and nutrients.

  4. Make The Mix

    Finished Bag of Fertilizer
    image credit:

    And now to the fun part — mixing! If you have a concrete area in your garden, this is a good spot to do the mixing. If you don’t, you can use a tarp instead.

    Spread it out on the ground. Next, place equal portions of the phosphorus and potassium fertilizers on the tarp. Then, add in the right amount of filler material.

    Stick to the ratio you calculated in Step 2. For instance, if you measured out two scoops of phosphorus, add two scoops of potassium and six scoops of the filler.

    If you cannot use scoops and can only use the weight of the ingredients, check out my table for calculations below which should help you.

  5. Mix

    Next, mix all the ingredients thoroughly using your straight edge shovel. Continue mixing until the ingredients are well-blended.

Table for calculations

I created a table that should help you with your calculations.

In the table, you will see “X lb”. X stands for the amount of phosphorus you want to use based on your plant requirements and/or soil tests. You should get in the second step above.

0-20-2- Fertilizer mixing table


Let’s say we determined that the amount of phosphorus needed for a 1,000 square-foot lawn is 1 pound.

Since the formula of our fertilizer is 0-20-20, it means we need the same amount of potassium as phosphorus, or 1 pound.

The number 20 in the formula stands for the percentage. It means that the final mix should consist of 20 percent potassium and 20 percent phosphorus.

Now, how much of the filler do we need to add?

Percentage-wise, it would be 60 percent. Why? Because: 

20% potassium + 20% phosphorus = 40%

100% – 40% = 60% 

Now, let’s translate this into pounds:

  • 60% is 3 times more than 20%
  • According to our calculations above, 20% should be 1 pound
  • So, 3 times 1 pound is 3 pounds.

This means we need 3 pounds of filler. 

In total, for our example, you would get 5 lb of fertilizer:

1 lb phosphorus + 1 lb of potassium  + 3 lb of filler

Keep in mind that this is only an example. The figure you use for your computation will depend on your soil test results.

How To Store The Fertilizer

When you’ve finished mixing your fertilizer, transfer the mix to a bucket or sack for storage

If you’re making just a small portion of the fertilizer to use within a few days, you can store it in a plastic bag. Be sure to label the sack or bucket as 0-20-20 fertilizer to avoid confusion.

Storing your 0-20-20 fertilizer is important to ensure safety. The ideal storage area should be dry and away from other chemicals. Proper storage is also crucial if you are making a 0-20-20 fertilizer for sale.

Why Make 0-20-20 Fertilizer?

The main reason why people make 0-20-20 fertilizer is that they want to fertilize their garden or lawn in the late fall

This ratio is considered ideal for this season since plants need smaller amounts of nitrogen in the winter. However, phosphorus and potassium are essential — phosphorus improves root growth, while potassium boosts overall plant health. 

If you need to fertilize your lawn during summer, take a look at a fertilizer with the ratio 10-10-10.

Diagram of how 3npk fertilizer benefits plants

Did you enjoy my tutorial? If you did, please share it with others. You can also post comments or questions in the box below.

How To Mix A Powerful 0-20-20 Fertilizer At Home Infograph

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