What is the Best Lawn Fertilizer Ratio? How to Know

Fertilizing your lawn with the best fertilizer ratio has a greater influence on the color and ability to recover from stress. It also helps the lawn withstand drought, pests, diseases, and weeds. So, what is the best lawn fertilizer ratio?

When determining the best fertilizer percentage for your lawn, there are various things to consider, such as climatic conditions, grass type, stage of growth, NPK ratio numbers, and the fertilizer formula.

Lawn fertilizer contains three main elements, nitrogen, phosphorus, and potassium. They are found in different ratios to give the best results when applied to the lawn correctly.

Best lawn fertilizer ratio for spring

The best lawn fertilizer ratio for spring is when the percentage of nitrogen is higher than that of phosphorus and potassium. In this season, you need a lush green lawn. The grass doesn’t need much phosphorus as it is recovering from dormancy.

Additionally, the roots are already established from the fall. The lawn also needs a small amount of potassium to become resistant to insects and diseases attack.

Therefore, the best lawn fertilizer ratio for spring should be 15-0-6, 20-0-5 or 30-0-4. All of these ratios have a higher percentage of nitrogen, no phosphorus, and some potassium.

The fertilizer ratio may vary depending on the growth conditions of the lawn, as stated below.

1. Newly Grown Lawn

Your lawn requires adequate nutrients for healthy growth and development if it is newly grown. It requires more nitrogen to turn into a lush green color that supports photosynthesis.

A newly grown lawn requires enough chlorophyll to produce enough energy for growth. Therefore, the best fertilizer ratio should be 30-0-4. You may use another ratio if the nitrogen percentage is higher with some little potassium.

2. Established Lawn

An established lawn that is recovering from winter has to be cared for, just like a newly grown lawn, to change color from brown to lush green. To do so, you will need a fertilizer with a high percentage of nitrogen, no phosphorus, and a little potassium to boost growth. Therefore, the ratio should be 30-0-4.

3. Struggling Lawn

A poor lawn that is struggling to survive requires much effort to be revived. It requires the best fertilizer ratio to boost foliage growth and root development.

The ideal fertilizer ratio should be 22-23-4. The percentage of nitrogen and phosphorus are high to stimulate lush green color and promote root development. The potassium ratio is small just to boost the process.

The best time to fertilize your lawn in the spring is one or two weeks after the last frost when the temperatures are warm. If you have grown cool-season grass, fertilize when the temperatures are between 60 and 75 degrees Fahrenheit (15.56 to 23.89 degree Celsius).

On the other hand, fertilize warm-season grass when the temperature is 80 to 95 degrees Fahrenheit (26.67 to 35 degree Celsius). Fertilizing your lawn too early in the season may cause stress, and the plants won’t absorb the fertilizer fully.

Also read: When is it too cold to fertilize a lawn?

Best lawn fertilizer ratio for summer

Applying fertilizer on the lawn is part of the care and maintenance program. However, it is challenging when the weather is dry. Applying the wrong fertilizer ratio on your lawn in the warm season of summer can be detrimental. You may end up with a burned-out lawn.

The best lawn fertilizer ratio for summer is 25-0-5-50% slow release. 25% Nitrogen (N), 0% phosphorus, 5% potassium, and 50% of filler materials.

Slow-release fertilizer is better in the summer. It is coated with plastic resin or sulfur-based polymers to break down slowly when exposed to heat from the sun, water, or soil microbes.

Slow-release fertilizers minimize the risk of lawn fertilizer burn while staying in the soil for longer. It can last in the soil for a period of one to three months. There is an increased risk of lawn burn-out when you use quick-release fertilizers.

The idea behind quick-release fertilizers is to give the lawn a boost by releasing nutrients into the soil fast. However, it should be applied in an appropriate season.

Quick-release fertilizers contain a high nitrogen ratio. When applied to the grass during summer, the soil’s microbes cannot break down the excess nitrogen. Therefore, it dries out the grass blades to cause a burned look.

Apply low-nitrogen fertilizers to your lawn during the summer season. They release nutrients into the soil to maintain healthy growth throughout the summer. High nitrogen ratio fertilizers are appropriate for a lush green lawn during the spring season.

Best lawn Fertilizer ratio for fall

The fertilizer ratio you use in the fall greatly affects how your lawn fairs on come early spring. A fertilizer containing a high nitrogen ratio is what you need for your lawn at the beginning of the fall. A 36-0-6 slow release will do better in the early fall.

Fertilizing your lawn again in the late fall with 13-25-12 is also essential. The extra phosphorus and potassium will help stimulate root growth and strengthen the lawn against insect and weeds attack. Fertilizing gives the lawn a strong foundation to thrive in the spring.

Grass grows best with regular fertilizer application, rich in nitrogen and other nutrients. Spacing fertilizer application too far may lead to slow and uneven growth spurts. The grass also becomes stressed and more vulnerable to pests, diseases, and weeds attack.

Nitrogen is the most important of the three primary fertilizer elements, but not always. It is important to understand that excessive application of nitrogen in the fall is associated with various problems, such as excessive top growth.

Using one pound of nitrogen per 1000 square feet of space is recommended to fertilize your lawn.

How to know the best lawn fertilizer for your lawn

There are different types of lawn fertilizers in the market, and it may be challenging to choose the right one for your lawn. To know the best lawn fertilizer ratio to use, here is what to do:

1. Conduct a Soil Test

Knowing the best fertilizer for your lawn is impossible without conducting a soil test. Soil test help to determine a specific nutrient that is inadequate in the soil. It also provides recommendations on the proportions needed.

2. Understand the Ratio Numbers on the Package

It is challenging to choose a suitable fertilizer for your lawn without understanding what the NPK ratio means on the fertilizer label. Fertilizers contain three main ingredients; Nitrogen, phosphorus, and potassium. They are abbreviated as N.P.K.

For instance, a 50kg bag of fertilizer with indications of 25-5-15 comprises 25% Nitrogen (N), 5% phosphorus (P), and 15% Potassium. The remaining 65% is made up of filler materials and other substances that improve the flowability of the fertilizer.

Some fertilizers contain more nitrogen ratio than phosphorus or potassium and vice versa. Each nutrient helps the lawn in different ways. Nitrogen improves lush green, phosphorus promotes roots and flower growth, and potassium helps the plant resist diseases and hardships.

3. Consider Climatic Conditions

Select fertilizer that is suitable to the climatic conditions of your region. The fertilizer ratio varies from one region to the other based on climatic conditions. Check the bag for manufacturer’s ratio recommendations for your region before purchasing.

A fertilizer ratio suited to hotter areas like coastal plains may not give the best results when applied to lawns in regions with cool or temperate climatic conditions.

4. Growth stage of your Lawn

Like any other plant, grass has different nutritional requirements in its various stages of growth. The fertilizer that is best for planting has a high ratio of phosphorus and potassium to enhance root development and resistance to drought.

When the lawn is established, you will need a fertilizer with a high nitrogen ratio to promote lush green color growth.

5. The type of Grass

There are different types of grass, and each has different nutritional requirements. Some grasses require a high ratio of nitrogen to grow, while others may need medium or low amounts of nitrogen. When purchasing grass seeds, inquire about their nutritional requirement to know the best lawn fertilizer to use.

6. Fertilizer type and Formula

Choosing the best fertilizer for your lawn must depend on the type and formula. There are two main types of fertilizers: synthetic and organic fertilizers. Both synthetic and organic fertilizers have the necessary nutrients required by plants.

However, organic fertilizer can be incorporated into the soil before planting to improve drainage and the soil’s overall health.

Also read: How long does it take granular fertilizer to work?

Final Thought

When purchasing fertilizer for your lawn, read and understand the ratio numbers indicated on the package. You should also consider the climatic conditions of your region, the type of grass, the stage of growth, and the fertilizer formula. Applying the best lawn fertilizer ratio to your lawn ensures a lush green color throughout the year.


  1. University of Illinois Extension: Choosing Fertilizers for Home Lawns
  2. Oregon State University Extension: Fertilizing Lawns
  3. University of Nebraska–Lincoln Turfgrass Science Program: Ideal fertilizer ratio for turfgrass

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