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NPK Fertilizer: What You Need to Know About Its Function on Your Lawn

The type of fertilizer you use determines how much of each of these essential nutrients your lawn will have. NPK fertilizer is a type of fertilizer that contains all three of these nutrients in the correct proportions to feed your lawn.

What is NPK Fertilizer?

NPK stands for Nitrogen, Phosphorus, and Potassium. Nitrogen (N), Phosphorous (P), and Potassium (K) are the main nutrients that make up a complete fertilizer. These nutrients are essential for the health of your lawn. Without all of these nutrients, your lawn will not be able to grow.

In general, a complete fertilizer has enough nitrogen to feed your grass, but not too much. It has enough phosphorous to help your grass stay green and strong, but not so much that it burns it. And it has enough potassium to promote healthy root and green leaf growth.

NPK fertilizers are a type of complete fertilizer that contains all three of these nutrients in the correct proportions to feed your lawn.

Nitrogen is an element required by plants, and it plays an important role in photosynthesis. It also helps form amino acids which are necessary building blocks for protein. Nitrogen is vital during periods of growth and stored when energy levels diminish; it’s a crucial component of chlorophyll-a molecule indispensable to performing photosynthesis.

Phosphorus is responsible for several aspects of plant growth. It ensures proper functioning, such as the production of oils and starch that supplies energy to plants. Additionally, it aids in cleaning solar light into chemical form, helping with photosynthesis (energy) within a given organism by turning carbon dioxide and water into organic molecules.

Potassium is an essential element of plant growth. It helps activate enzymes in the plant. It also boosts plants' ability to survive disease and severe weather conditions. It also dictates characteristics like shape, size, and color.

Along with the three predominant elements mentioned, there are also other macronutrients and micronutrients in fertilizers.


Besides magnesium and sulfur, which help photosynthesis (alongside other processes), some amount of iron, zinc, and boron copper is present to help fight diseases in plants and synthesize proteins.


Along with a lot of others such as calcium phosphorus, potassium, and sodium chloride that serve various purposes like strengthening plant cells or aiding flowering/fruit production - it's important not to forget about iron, zinc, boron, and copper. These four serve to fight off illnesses while helping produce chlorophyll for your plants.

How to Apply NPK Fertilizer

You should always follow the instructions on the bag of fertilizer or granular that you buy. However, there are a few general instructions you should know before applying any type of fertilizer.

  1. First, check with your local municipality to make sure that you aren’t violating any city or county laws by applying fertilizer within city or county limits.
  2. Next, read and follow the directions on the bag of fertilizer. These will vary depending on the type of lawn that you have. For example, if you have an average size lawn, you would apply about 2 lbs. of fertilizer per 1,000 sq. ft. of lawn. However, if you have a large lawn, you would apply about 3 lbs. of fertilizer per 1,000 sq. ft.
  3. If you have a small lawn, you will want to apply fertilizer in the spring. If you have a large lawn, you may want to consider applying fertilizer in the fall.
  4. With any type of fertilizer, it is a good idea to rake your lawn before applying fertilizer. It will allow some of the old grass and weeds to break down. They can serve as a nutrient to the new grass.
  5. Finally, be sure that there is no rain predicted for at least 24 hours after you apply any fertilizer. Rain can wash away the nutrients in your soil before your grass and plants absorb them.

When to Use NPK Fertilizer

You should apply nitrogen-based fertilizers when your lawn signs are creating growth. This process usually occurs in two stages.

The first is when the lawn is actively growing, but it isn’t quite getting the nutrients that it needs to sustain that growth.

The second is when the lawn has reached its full growth potential and is now going to seed. At this point, you should apply nitrogen fertilizer to help your grass survive and thrive.

You are probably wondering what the best time of day to fertilize your lawn is. It is best to wait until late in the afternoon or early evening. You should never fertilize if there is direct sunlight because it will lead to a burning risk. If you want an even safer option and do not mind waiting for the ground to cool down, you can wait until nightfall before watering/fertilizing.

Types of NPK Fertilizers

Traditional 20-20-10

20-20-10 fertilizer is fast release, with plenty of nitrogen and phosphorus. 20% Nitrogen, 20% Phosphorus, and 10% Potassium. A well-balanced fertilizer will have close to all three nutrients stated by the numbers in its N-P-K analysis (Nitrogen - Phosphorus - Potassium).

If your yard is in poor condition, use a traditional NPK fertilizer; there is no point in adding more nitrates if your lawn actually needs phosphates. Keep on top of this so that you don't end up having nutrient deficiencies in one place and overfertilization in another.

Remember that phosphates and potassium stay around long after nitrogen does in the soil. It can lead to problems later; make sure your lawn still has them when it needs them.

20-5-5 Slow Release

It is a type of fertilizer that has 1/2 of its nitrogen as slow-release and the other half in traditional form.

Phosphorus and potassium are only at 5% when you choose this type of fertilizer-they will be sufficient if used 2 to 3 times annually. This type of fertilizer encourages even growth. It is suitable for already healthy and well-established lawns.

8-2-1 100% Organic

Organic nitrogen sources are from dried poultry. This long chain of amino acids releases very slowly over the year.

Note that 8% is a percentage of the nitrogen content; you will need more products to get the same amount as food for your lawn with this type of fertilizer because it contains less nitrogen than traditional fertilizers do.

With organic fertilizers, it takes longer to see results. Some people also like using an organic source with traditional lawn fertilizer - a method known as combined application - to help condition and build nutrient levels into the soil.

As with traditional fertilizers, follow the manufacturer's directions for application rates and frequency.

This is a very good choice for areas where you do not want to see any damage from over-fertilizing or where you are growing a new lawn.

Unfortunately, this type of fertilizer does not work as well on mature lawns because it takes longer to release its nutrients into the soil.

Click on The Image Below to Calculate How Many Fertilizer You May Need For Your Lawn
Lawn Fertilizer Calculator

How to Read the Label

Reading the label on your fertilizer can help you determine how much to apply. It will contain several pieces of information, including:

  • The type of fertilizer that it is
  • The number of nutrients that are in each bag
  • The pH level of the fertilizer
  • The best way to apply the fertilizer

The bag should also contain a fertilizer analysis chart. It will tell you how much nitrogen, phosphorous, and potassium are in the bag as well as the percentage of each.

You could also consider getting a soil test to see what nutrients are in your soil and how much of each nutrient your lawn needs. It will help you determine the right amount of fertilizer to apply.


There are plenty of great options on the market for fertilizing your lawn, including different types of NPK fertilizer.

NPK fertilizers are a type of complete fertilizer that contains all three of these nutrients in the correct proportions to feed your lawn. They are especially helpful for newly established lawns that need a jumpstart.

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