What is the Best Lawn Fertilizer Ratio? How to Know

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

When determining the best fertilizer percentage for your lawn, there are various feature 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 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. At this season, you need a lush green lawn. The grass don’t need much phosphorus as it is recovering from dormancy.

Additionally, the roots are already established from the fall. The lawn also needs some little amount of potassium to become resistance 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 growth conditions of the lawn as stated below.

1. Newly Grown Lawn

If your lawn is newly grown, it requires adequate nutrients for healthy growth and develop. It requires more nitrogen to turn into a lush green color that support photosynthesis.

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 as long as the nitrogen percentage is higher with some little potassium.

2. Established Lawn

Having an established lawn that is recovering from the fall has to be natured just like a newly grown lawn in order to change the color from brown to lush green. To do so, you will need a fertilizer that has high percentage of nitrogen, no phosphorus and some little potassium to boost the growth. Therefore, the ratio should be 30-0-4.

3. Struggling Lawn

A poor lawn on its death bed that is struggling to survive requires a lot of effort to be revived. It requires best fertilizer ratio to boost foliage growth as well as root development.

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

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

On the other hand, fertilize warm season grass when the temperature is 80 to 95 degree 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.

Best lawn fertilizer ratio for summer

Applying fertilizer on the lawn is part of care and maintenance program. However, it is challenging when the weather is dry. Applying wrong fertilizer ratio on your lawn in 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 minimizes the risk of burn while staying in the soil for longer. It can last in the soil for a period of one to three month. There is an increases 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 contains high nitrogen ratio. When applied to the grass during summer season, the microbes in the soil are unable to break down the excess nitrogen. Therefore, it dries out the grass blades to cause a burned look.

Quick release fertilizers should not be applied especially to cool season grasses such as perennial ryegrass, tall fescue, fine fescue and Kentucky bluegrass during summer. When not watered completely into the lawn, the fertilizer causes stress to the grass and hence resulting into a lawn burn.

Apply low-nitrogen fertilizers to you lawn during summer season. They releases nutrients into the soil to maintain a healthy growth throughout the summer. High nitrogen ratio fertilizers are appropriate during spring season for a lush green lawn. May cause stress or burn when applied to the lawn in summer season.

Best lawn Fertilizer ratio for fall

Fertilizer ratio you use in the fall greatly affects how your lawn fairs on come early spring. Fertilizer containing high ratio of nitrogen is what you need for your lawn at the beginning of the fall. A 36-0-6 slow release will do better at 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 to stimulate root growth as well as strengthening the lawn against insect and weeds attack. Fertilizing gives the lawn a strong foundation to thrive in the spring.

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

Nitrogen is the most important among the three primary elements of fertilizer, 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. It is recommended to use one pound of nitrogen per 1000 square feet of space to fertilize your lawn.

How to know the best lawn fertilizer for your lawn

There are different type of lawn fertilizer in the market and it may be challenging to choose the right one for your lawn. Fortunately, there are some guide that may help you to make correct decision when purchasing.

1. Conduct a Soil Test

It is impossible to know the best fertilizer for your lawn 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 ratio means. Fertilizers contains three main ingredient i.e. Nitrogen, phosphorus and potassium. They are abbreviated as N.P.K. The ratios are normally indicated on the packaging in numbers and vary depending on the type of fertilizer.

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

Some fertilizers contain more ratio of nitrogen as compared to phosphorus or potassium and vice versa. Each nutrient helps the lawn in differently way. Nitrogen improves lush green color, phosphorus promotes roots and flower growth while potassium helps the plant to become resistance against diseases and hardships.

3. Consider Climatic Conditions

Select fertilizer that is suitable to climatic conditions of your region. Fertilizer ratio varies from one region to the other basing on the climatic conditions. Fertilizer ratio suited to hotter areas like coastal plain may not give best results when applied to lawn in regions with cool or temperate climatic conditions.

Check the bag for manufacturer’s ratio recommendations for your region before purchasing.

4. Growth stage of your Lawn

Grass like any other plants have different nutritional requirements in their various stages of growth. Fertilizer that is best for planting has a high ratio of phosphorus and potassium to enhance root development and resistance to drought. While you will need fertilizer with high nitrogen ratio when the lawn is established 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 requires high ratio of nitrogen to grow while other may need medium or low amount 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 need to be based 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 prior to planting to improve drainage and the overall health of the soil.

Final Thought

When purchasing fertilizer for your lawn, read and understand the ratio numbers indicated on the package. You should also consider climatic conditions of your region, type of grass, 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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