The Best Lawn Fertilizer Ratios for Spring and Summer

If you’re looking to have a healthy, green lawn all summer long, then you need to be using the right lawn fertilizer ratios. In this article, we will teach you what those ratios are and how to apply them for optimal results. Keep reading to learn more!

Yellow spreader for summer lawn fertilizer.

First: What do the Fertilizer Numbers Mean?

When you look at a bag of fertilizer, you will see a series of 3 numbers. These numbers are commonly referred to as N-P-K analysis

The letters represent important nutrients that your lawn requires for growth, color, and overall plant health.

NPK ratio on fertilizer bag graphic.

N stands for nitrogen, P represents phosphorus, and K stands for potassium. Together, these three elements will help feed and grow a healthy lawn.

However, when you look for the N-P-K ratio on the fertilizer label, you will notice there are numbers instead of letters. These numbers will vary greatly between fertilizers, so it is important to have a good understanding of what they mean before you buy a bag and start applying it to your lawn.

An example of an analysis you might see when scanning the fertilizer aisle is 10-10-10.

When looking at these numbers, it’s important to know that they represent percentages.
In this example, the bag of fertilizer contains 10% Nitrogen, 10% Phosphorus, and 10% Potassium. 

You may be thinking, “If you add all of those together, that’s only 30%. So what’s in the rest of the bag?

In this case, the remaining material is inert filler material that adds bulk to the product, which will make it much easier to spread and apply to your lawn.  

Once we have looked at the percentages listed in the analysis, the next step is to confirm the total weight of the bag. 

Most fertilizers will usually come in 25 or 50lbs bags.

Using our example of a 10-10-10 analysis and a 50lb bag to determine the total pounds of a given nutrient, you need to do a little math. 

You do not want to skip this step, especially in the summer. Calculating the correct amount of fertilizer to apply is crucial to avoid burning or injuring your lawn. 

To determine the amount you need to apply, the first step is to multiply the weight of the bag by the percentage in the analysis. You’ll complete this step for each number given if needed, but most recommendations will be based upon the total pounds of nitrogen you want to apply.

For example:

Bag Weight in Pounds X Percentage on the Bag = Total Pounds of that Nutrient in the Whole Bag

Step 1: 50 (lb bag) x .10 (10% N) = 5lbs of Nitrogen in the entire bag of fertilizer.

Many common fertilizer applications will call for 1 pound of nitrogen per 1,000 sq ft of lawn.

Now that you know how much total Nitrogen is in the bag, you need to determine how much of the bag you need to use to apply 1 lb.

Step 2: 50 (lb bag) / 5 (total pounds in the bag) = 10 lbs of fertilizer for 1 lb of Nitrogen

So, if you have a 1,000 sq ft lawn, you would apply 10 lbs of product through your spreader to give you the desired amount. If you have a 3,000 sq ft lawn, you would apply 30 lbs of product.

So the next time your child asks you when they will use what they are learning in math class, you can give them this example.

What is the Best Fertilizer Ratio for Your Summer Lawn?

When determining the best lawn fertilizer ratio for summer, there are a couple of important factors to consider.

While many people think that applying any fertilizer at any time is good for your lawn, that couldn’t be further from the truth.

As with all lawn care, what you’re lawn needs is going to depend on a variety of factors that are unique to your lawn. 

Soil Composition

A valid soil test from a reputable source, like your local University Extension office, will provide you with information about your soil’s current nutrient levels.

The soil test results will take the guesswork out of your fertilizer applications and help you feel confident that you are applying exactly what your lawn needs throughout the season, including your summer fertilizer applications.

Grass Type

Close up image of summer lawn.

Whether or not you do a soil test, you will need to know if you are growing cool or warm season grass. This is because warm season and cool season grass have very different needs during the hot summer months.  

For example, common cool-season grasses like bluegrass, fescue, and rye will go dormant during the summer to help protect themselves from the heat.

Applying fertilizer to a lawn that is already under stress due to high temperatures is not recommended and could do more harm than good.

On the other hand, common warm-season grasses like bermudagrass, zoysiagrass, and centipedegrass will continue to grow and thrive during the summer months.

Local Climate

The climate in which you live will also play a role in how much fertilizer your lawn needs during the summer.

For example, if you live in an area that experiences long periods of drought, your lawn may be stressed, which is not a good time to be applying fertilizer.

Additionally, if your area receives frequent rainfall and you supplement with sprinkler irrigation, you are probably safe with more frequent applications.

Type of Fertilizer

The type of fertilizer you use will also affect how much you need to apply during the summer months.

Synthetic Vs. Organic:

Synthetic fertilizer is made with inorganic materials and is best applied in small, frequent doses. On the other hand, organic fertilizers are made with natural materials and is best applied in larger, less frequent doses.

Granular Vs. Liquid:

Granular fertilizer is best applied with a broadcast spreader, while liquid fertilizer is best applied with a pump or backpack sprayer.

Liquid fertilizer will need to be applied more often than granular fertilizer, but it is easier to apply the correct amount with a liquid fertilizer since you can control the spreader settings.

Quick Release Vs. Slow-Release Fertilizer:

Quick release fertilizer will provide a quick burst of nutrients to your lawn, but it will need to be applied more often than slow release fertilizer.

Slow-release fertilizer is best for summer applications since it will provide a steady supply of nutrients to your lawn over an extended period of time. This means that you won’t have to worry about reapplying as often.

Irrigation and Watering

In order to achieve the best results, you should apply fertilizer to your lawn when it is dry and then water it deeply. This will help prevent any burn potential and ensure that the fertilizer is absorbed by the plant.

Now that you know all of the important factors to consider when determining the best lawn fertilizer ratio for summer, you are ready to choose a fertilizer ratio that will keep your lawn looking green and healthy all summer long!

Summer Fertilizer Ratios for Cool Season Grasses

Cool season grasses like Turf Type Tall Fescue, Kentucky Bluegrass and Perennial Ryegrass, will have limited growth potential in the summer and can be negatively affected by too much nitrogen when the summer temperatures are hot. 

Pushing too much growth during the summer will put more stress on the plant that is already struggling to stay alive during the peak of summer. 

Applying too much nitrogen can put your lawn under stress due to high temperatures. Remember to only apply .50lbs or less of total nitrogen per 1000 square feet of lawn. This will give your lawn the boost it needs to stay green during the summer months.

During the spring and summer, cool-season grasses will benefit from fertilizers with lower nitrogen content and higher potassium content. 

Nitrogen promotes unwanted top growth while potassium will help reduce plant stress. 

A good rule of thumb is to apply a product with at least a 1 part nitrogen to 2 part potassium ratio. When in doubt it is best to use a fertilizer that has 1-1-1 ratio.  

For summer fertilizer applications of cool season lawns, you want to refrain from applying too much nitrogen. 

As mentioned in our fertilizer calculations, you would want to apply no more than .50lbs of total nitrogen per 1,000 square feet of lawn. This application rate will be just enough to give your lawn the boost it needs to stay green during the summer months without pushing too much growth and putting your lawn under undue stress.

Recommended ratios to look for include:

  • 10-10-10
  • 15-15-15
  • 20-0-8

Summer Fertilizer Ratios for Warm Season Grasses

Warm season lawns like Bermuda grass, Zoysia, and St. Augustine thrive during the hot summer months. During early spring and summer, these grass types have the highest growth potential.

Unlike cool season lawns, warm season lawns will benefit the most from larger applications of nitrogen fertilizer. 

Common fertilizer applications for warm-season grasses during the summer should equal about 1 pound of total nitrogen per 1,000 square feet of lawn monthly. This can be accomplished by fertilizing .25 of nitrogen per 1,000 square feet a week in June, July, and August or 1 pound per square feet each summer month, respectively.

When applying summer fertilizer to warm season lawns, you will want to apply more Nitrogen.

We recommend looking for products with the following npk ratios:

  • 10-10-10
  • 15-15-15
  • 46-0-0
  • 21-0-0

When Should I Apply Summertime Fertilizer?

In most cases, the best time to apply summer lawn fertilizers is late spring.

This is because the grass will be actively growing and will be able to utilize the nutrients more efficiently.

If you live in an area with a long growing season, you can split your fertilizer applications up and apply half in early summer and the other half in mid-summer.

Remember warm-season lawns will benefit more from summer fertilization than cool-season grasses.

It’s more important to focus on fertilizing cool season grass during its growth season, which is spring and fall.

No matter what, you should avoid applying fertilizer during the hottest part of the day. It’s best to schedule your applications during the cooler mornings and evenings.

Now that you know the best lawn fertilizer ratios for spring and summer, you can keep your lawn looking green and healthy all season long! Just remember to adjust your fertilizer application depending on the type of grass you have. If you have any questions, feel free to ask in the comments below.