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What Do The 3 Numbers On Lawn Fertilizer Mean?

With summer just around the corner, it is time to start thinking about the new garden that you want to grow in your yard. If it has been a while since you grew a garden or you want to really get a high-yield on your produce, picking the right fertilizer is critical. 

The three numbers on lawn fertilizer are there to tell you the concentration of Nitrogen, Phosphorus, and Potassium that are inside the fertilizer. Once you know how much of each nutrient your plants need to thrive, you can choose the fertilizer that will work best for your garden.

Let’s explore more about each of the three numbers, learn why they are important, and how you can use these to get the best garden ever. 

Related: The Best Broadcast Fertilizer Spreader For Small Yards

What Do Those Three Numbers Mean?

When you take a look at any lawn fertilizer you want to use at home, you may notice there are three numbers that show up. If you are like most other homeowners, you may ignore the numbers and not care what they mean. But these numbers are important for helping your lawn and plants grow. 

Nitrogen, Phosphorus, and Potassium

These three numbers tell us the value of the three macro-nutrients that all plants need. These nutrients are needed whether you are growing a beautiful vegetable garden or you need to help your grass grow more. The three macronutrients that will show up on the bottle include nitrogen, phosphorus, and potassium. They will be written out as NPK (usually in that order too), for short. 

Higher Numbers Mean Higher Concentrations

The higher the number that comes on the bottle, the more concentrated the nutrient is inside that fertilizer. For example, if you have a fertilizer that lists out the NPK as 20-5-5, it means that there is four times the nitrogen compared to the amount of potassium and phosphorus. But a fertilizer that is listed as 20-20-20 is twice as concentrated as one that is 10-10-10. It is also possible for the fertilizer to only have one macro-nutrient. If the NPK is written as 10-0-0, this means that it only has nitrogen. 

Plants Require Different Concentrations

Each plant has different requirements for how much of each nutrient you need. Some plants need more nitrogen while others thrive on higher levels of potassium. If you are looking for fertilizer for a specific type of plant, you should study how much of each nutrient it needs to thrive before purchasing any fertilizer. 

These numbers are also useful to help you figure out how much fertilizer to use in each area. You are able to use the concentration of each macro-nutrient to help you figure out how much you need to add to the soil. 

Why Are These Numbers So Important?

importance of three numbers on fertilizer bags

Now that we understand what these numbers mean, it is important to see how all these numbers work and why you should care. All plants need all three of these nutrients to grow. Without enough of any of them, the plant will end up failing. However, each plant will need different concentrations and ratios of these nutrients which is why the numbers on the package are important. 

Each nutrient is responsible for helping out a different part of the plant. For example:

Knowing the right NPK values of any fertilizer you would like to use helps you select one that is best for any plants you would like to grow. For the leafy vegetables, you need to choose a fertilizer that has higher concentrations of nitrogen to promote the growth of the leaves. If you have flowers, then a higher phosphorus concentration is better to encourage the blooms. 

The Best NPK Values for Your Garden

The Best NPK Values for Your Garden

It is important to pick the right NPK values for your garden. This will often depend on which types of plants you would like to grow. If your garden is going to be full of leafy greens or another plant with large leaves, then adding extra nitrogen to the soil is important. Nitrogen is great for supporting the leaves of all plants and can give you some of the best lettuce, spinach, and other leafy greens. 

However, if you plan to work with something like tomatoes or another flower, then making sure the flower has some extra phosphorus in the soil is important. Phosphorus takes care of not only the roots of the plant, but also any fruit that comes from it or the flowers so it can be great for a big flower garden. 

Potassium is needed to improve the functioning of the plant in all areas. All plants can benefit from having a little bit extra potassium in them, ensuring that the roots are strong and the plant is able to function well in the soil. If your plants seem a little droopy during the summer, you may want to add more potassium. 

How to Test Your Soil

To make sure that your garden is as successful as possible, you need to test the soil and then add in the right fertilizer. Testing the soil level will help you learn the pH level and see which nutrients are there already and which ones need replenished with the fertilizer. Most soils are low in at least one of the main macro-nutrients, depending on the area and type of plants you want to grow. Testing the soil will help you determine which ones and make changes. 

There are several ways that you can test out the soil and analyze the nutrient composition inside. Two options include:

Do It Yourself

There are several kits you can use to check out the soil and see the levels of nutrients that are present. You simply purchase the kit and then follow all the instructions that come with it. This will help you know the pH level of the soil and figure out what will work best in that area. 

If you want to test your own soil, I recommend the My Soil Test Kit.

Have a Lab Test Done

If you are worried about getting a specific type of nutrient into the soil, you can consider doing a lab test on the soil. This can be a good investment since the lab is able to do a thorough analysis of the soil around you. Some of the things you can learn about when you have a lab do your soil test includes:

  • The nutrient content of the soil: If you do this test and learn the nutrient content, you can then determine the type of fertilizer, and how much, that you need to make plants grow well. 
  • Soil problems in your region: This kind of test is a good way to identify any local problems. The oil lab is able to tell you the amount and type of fertilizer to have in the summer. 

Both of these options allow you to look closer at your soil and determine whether you need to add more of one nutrient or another in to help you get the best crop possible. 

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