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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. 

Since you’re most likely going to mix and apply the 0-20-20 fertilizer in early spring or fall, the weather might get cold and damp. Therefore, a solid pair of shoes is a must-have. In my experience, keeping dry and comfortable feet tremendously affects the pace and effectiveness of my work, even though it doesn’t really have anything to do with what I’m doing with my hands!

It’s important to add filler material when making 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. With phosphorus and potassium making up 40% of the entire thing, you should dedicate 60% to filler. Be wary of not adding too much of it, as it might dilute the active ingredients, making your fertilizer less effective. As I already mentioned above, though, filler needs to make up the majority of the fertilizer, as highly concentrated active ingredients may damage your plants.

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 turn 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 nutrients 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% phosphorus, 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.

    Never eyeball the amounts of phosphorus, potassium and filler. I made that mistake in my early gardening days and completely ruined my plants! Too much active ingredients, and it will eat away the delicate parts of your precious vegetation. Overly copious amounts of filler will dilute the fertilizer too much, rendering the active ingredients useless, preventing you from achieving the desired effects.

  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. Don’t use plastic bags for long-term storage. It is not effective at preventing outside agents from getting into the mixture, potentially ruining your 0-20-20 fertilizer. The best way to store your fertilizer over long periods of time, especially over winter, is to place it in a plastic container that you can tightly seal so that moisture doesn’t reach the substance. That way, you’ll preserve your fertilizer’s quality for the next season.

Regardless of how long you’re planning to put your homemade 0-20-20 fertilizer away for, you’ve got to remember to keep it in a space that’s completely shaded, cool, and dry.

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. Even if the conditions in your basement, garden shed, or garage are impeccably clean, the active ingredients in 0-20-20 fertilizer are susceptible to even the tiniest of changes, and you don’t want to sell a product that doesn’t meet the highest quality standards.

What Is 0-20-20 Fertilizer Used For?

The main reason why people make 0-20-20 fertilizer is that they want to fertilize their garden or lawn in the late fall. Also known as “winterizing,” it is a particularly important aspect of caring for your backyard or garden. This is because the cold temperatures during the winter months make plants susceptible to all sorts of damage, as well as rendering them much weaker. That, in turn, makes them likely to not survive until the spring without proper help from their caretakers.

The 0-20-20 fertilizer 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. In other words, these elements strengthen plants, helping them survive the winter.

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

Common Problems and How to Deal With Them

When you’re mixing 0-20-20 fertilizer at home for the first time, you might run into some issues, particularly when it comes to getting the proportions right, as well as the kind of plants you want to use this nitrogen-free fertilizer for.

Measuring Out the Ingredients

Getting the ingredient ratios right primarily depends on the size of your backyard. Earlier on in this article, I’ve gone into detail describing the ingredient mix for a 1,000 square-feet space. However, if your backyard is smaller, then using these measurements will result in a fertilizer that is much too potent for the amount of land at your disposal. To avoid ruining your plants, get the exact square footage of your backyard, and calculate how many pounds of fertilizer you’ll need. You can use 1lb/1,000 sq ft guideline as a starting point. Then, follow the calculations we presented above.

What Plants Don’t Respond Well to 0-20-20 Fertilizer

Zero-nitrogen fertilizers are effective for winterizing most plant types, but vegetables don’t fall into this category. If you’ve got a small veggie garden where you grow tomatoes and such, do not fertilize its soil with 0-20-20 fertilizer, as vegetable plants need a lot more nitrogen to remain healthy.

The Bottom Line

Your backyard plants need all the extra help they can get during the winter months, when they get much less sun than usual, and are exposed to frequent rain and snowfall. Not to mention the harsh cold temperatures and strong winds that occur around that time in many regions of the world!

The 0-20-20 fertilizer is one of the most effective ways to strengthen your plants’ roots, stems, and overall health. Moreover, it is fairly easy to make on your own, if you don’t mind getting your hands a little dirty.

The key things you should remember are the fact that you need to be very precise when measuring out the nutrient-to-filler ratio, and that your homemade 0-20-20 fertilizer needs to be stored correctly in order for it to be usable in the seasons to follow.

At A Nest With A Yard, we publish tips, guides, and other interesting, gardening-related articles on a regular basis. Don’t hesitate to visit our website whenever you need some advice from seasoned gardeners!

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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About The Author

Nadya Jones

Nadya is a writer, entrepreneur, and designer based in Raleigh. She writes in her blog, the one you are visiting right now, where she shares her love for landscaping, gardening, and outdoor design. Her husband Brett provides her with a lot of inspiration and behind-the-scenes content. Together, they work on creating beautiful outdoor spaces that serve as an extension of their home and inspire others to do the same. If you are interested in landscaping, gardening, or outdoor design, be sure to check out the blog! Also, follow Nadya on Twitter, Instagram, Pinterest, and Flickr!

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