How to Fertilize Your Lawn

Learning how to fertilize your lawn is easy, once you prepare the land and purchase the proper supplies. After figuring out your grass’s ideal application rate, uniformly apply the fertilizer. 

Use a spreader to apply granular lawn food, and a sprayer for liquid fertilization applications. Check the weather report before applying, and read the instructions on the fertilizer label. 

How to prepare for fertilization

Before diving into fertilizer application, proper preparation ensures your lawn gets the maximum benefit from the nutrients you’re providing. A well-prepared lawn allows fertilizer to reach the soil effectively, promoting even distribution and optimal absorption by the roots, while helping identify potential issues like soil compaction.

If you need help with any of the steps below, hire a local lawn care pro to handle the job hassle-free.

Step 1: Test your soil

Since fertilizer compliments the existing soil, it’s important to know what’s in your lawn dirt. A soil test tells you levels of the following:

• NPK: The three main minerals that plants need to grow are NPK — nitrogen (N), phosphorus (P), and potassium (K). 

• Additional nutrients: In addition to NPK, lawns need small doses of iron, magnesium, and other micronutrients.

• Soil pH: The pH scale gauges soil’s acidity, telling you when your lawn needs lime.

• Organic matter: When plants and animals decompose, they help grass grow. If your lawn’s low, consider an organic fertilizer. 

Step 2: Identify your grass type

Before fertilizing, you must identify your grass type. Pay particular attention to the following:

• Preferred NPK: Each type of turf has different nutritional needs. For example, the best St. Augustine fertilizer is usually 3-1-2 or 4-1-3, but centipede prefers an NPK around 15-0-15. 

• Growth cycle: The best time to fertilize grass is at the start of its growing season. Generally, warm-season grass grows in the spring and summer, and cool-season grass sprouts in the spring and fall. However, it’s important to compare your climate with the temperatures at which your grass grows. 

• Stresses: Each grass type has its own strengths and weaknesses, which affect its nutritional needs. Amanda Folck, an extension educator at the University of Nebraska–Lincoln, gave us an example, “a slight increase in nitrogen is used in traffic heavy situations for grass growth in recovery with Kentucky bluegrass.”.

After testing the soil and identifying the grass, you can select the best type of lawn fertilizer.

Step 3: Calculate lawn size

Calculate the area of your lawn in square feet. Use the area formulas listed in the table below.

Shape	Area Formula
Square	Length x Width
Rectangle	Length x Width
Square	3.14 x Radius2
Triangle	(Height x Base) / 2

If your lawn isn’t one of the above shapes, break it into sections that are. 

Step 4: Calculating how much fertilizer

First, use the fertilizer’s NPK ratio to calculate its nitrogen content. For example, an NPK of 12-3-6 indicates that 12% of the fertilizer is nitrogen (N). Thus, if the bag weighs 10 pounds, it contains 1.2 pounds of nitrogen.

10 lb.of fertilizer  x  12% = 1.2 lb. of N  

Next, determine how much nitrogen your lawn needs. Although most lawns need around 1 pound of nitrogen per 1,000 square feet, it’s best to account for soil test results, grass type, and time of year.

Finally, figure out how much fertilizer to apply based on lawn size. Let’s say:

• Lawn size = 10,000 sq. ft.
• Nitrogen needed =  1 pound / 1,000 sq. ft.
• Fertilizer NPK = 12-3-6

To fertilize the entire lawn, you’ll need about 10 pounds of nitrogen.

1 lb./1,000 sq. ft.= 10 lb./10,000 sq. ft.

Thus, you need 83 ⅓ pounds of 12-3-6 fertilizer.

10 lb. of N ÷ 12%=83 ⅓  lb.

Step 5: Select equipment

Apply granular products with a fertilizer spreader and liquids with a sprayer. In addition, don’t forget your protective gear.

Choose the right fertilizer spreader

To select the correct type of fertilizer spreader, consider:

• Broadcast spreaders quickly cover a lot of ground, making them ideal for large lawns. However, haste makes waste, so they’re less accurate than drop spreaders.

• Drop spreaders are slow but accurate. Because fertilizer falls directly under the hopper, predicting where the granules land is straightforward. Thus, they work best when the application may interfere with nearby landscaping.

Choosing the right fertilizer sprayer

Handheld sprayers are more affordable and better for small areas. Conversely, backpack sprayers are more expensive and best for large areas.

Purchasing protective gear

Nitrogen fertilizers can burn your skin or irritate your eyes. Additionally, some fertilizers are dangerous when inhaled. To avoid injury, wear the following gear:

• Gloves
• Safety goggles
• Long sleeve shirt
• Long pants
• Dust mask
• Close-toed shoes

Step 6: Prepare your lawn

Properly prepare your lawn for fertilization by:

• Killing weeds: When weeds consume lawn food, they remove nutrients from the grass and use them to grow stronger.

• Cutting your grass: Mowing the lawn a few days before fertilization makes it easier to evenly apply the fertilizer. 

• Raking leaves: When the lawn’s debris-free, it’s easier for fertilizer to penetrate the soil.

• Watering your lawn: More nitrogen will reach your grass’s roots when the lawn is watered about two days before a fertilizer application. The grass blades should be dry by the time you fertilize. 

• Checking the weather report: Most fertilizers wash away if applied within two days of heavy rain. However, formulas differ. So, it’s important to follow the weather warmings listed on your fertilizer’s packaging. 

How to apply granular fertilizer

Granular lawn fertilizer consists of small pellets that release nutrients into your turf when watered. Its benefits include even spreading with standard lawn spreaders, reduced risk of burning grass blades, minimal drift on windy days, and the ability to feed grass steadily as the granules break down.

Step 1: Read your fertilizer’s instructions

Carefully read the instructions, paying particular attention to the recommended spreader calibration. 

Step 2: Calibrate your spreader

Calibration adjusts the size of the hopper’s hole. When the hole is bigger, more fertilizer falls.

Folck says, “Don’t forget to calibrate your spreader before the first application of fertilizer. This should be done to make sure there is accurate output of fertilizer that matches the [ideal application rate].”

While the calibration process can vary by model, here’s a general idea:

1. Check your product label for recommended spreader settings.
2. Measure a 100-square-foot test area.
3. Calculate how much product you need for that test area based on the coverage rate listed on the package.
4. Put that exact amount in your spreader.
5. Set your spreader to the recommended setting.
6. Walk at a steady pace and spread the product over your test area.
7. Check your results: If you run out before finishing, the setting is too high. If you have leftover product, the setting is too low.
8. Adjust the setting and repeat until you use the exact amount of product.
9. Write down the correct setting for future use with that product.

Step 3: Fill the spreader

To fill your spreader:

1. Ensure the hooper hole is closed
2. Pour fertilizer into the hooper
3. Don’t fill the spreader with more product than you can push
4. Pour the fertilizer over a paved surface, just in case some spills 

Step 4: Apply your fertilizer evenly

After putting on your protective gear, evenly apply the fertilizer.

While fertilizing:

• Push the spreader (don’t pull it)
• Walk in straight lines
• Keep a consistent, casual walking speed
• While walking, keep the hopper hole open
• When you stop to turn, close the hopper hole

The best route:

1. Starting in a corner, walk around the lawn’s perimeter. Position the spreader, so fertilizer falls right up to the lawn’s edge.
2. Next, turn and walk across the lawn in a straight line, parallel to the last fertilized line of the perimeter. Continue making parallel applications until the lawn is complete.
3. Then, turn 90 degrees to make applications perpendicular to the previous ones (making a grid pattern). 

How to apply liquid lawn fertilizer

Liquid lawn fertilizer is a fast-acting nutrient solution that’s sprayed directly onto grass. Its benefits include immediate absorption through grass blades and roots, even coverage across the lawn, and the ability to mix with other treatments like herbicides for efficient application in a single pass.

Step 1: Read the fertilizer’s instructions

Carefully read your fertilizer’s instructions. Pay close attention to the recommended rainfall and mixing instructions. 

Step 2: Check moisture

If the soil’s dry, most packages recommend watering your lawn a couple of hours before applying fertilizer. They also recommend avoiding application right before rain. 

Step 3: Prepare the liquid fertilizer

Some liquid fertilizers come in ready-to-use bottles and others are mixed in a tank:

• Ready-to-use: Connect it to a garden hose.

• Concentrated: Mix the liquid with water, according to the product’s directions and your grass’s recommended application rate. Folck warns that the wrong mix can burn the grass. 

Step 4: Evenly apply your fertilizer

Folck also warns that uneven applications may result in fertilizer burn. So, carefully apply light, even coverage across the lawn:

1. Start at the edge of the lawn.
2. Using a steady pace, walk while spraying side to side.
3. Walk backward to avoid walking on treated turf.
4. Keep a keen eye on irregularly shaped spots.
5. Avoid re-spraying any sections.

What to do after the fertilization treatment

Clean up

After treating your grass, it’s time to clean up:

• To prevent staining, use a broom or blower to clear granular fertilizer on paved areas.
• Store fertilizer away from pets and children.
• Read the product label for proper storage instructions.
• For liquid fertilizers, don’t go on the grass until it dries.

Watering and lawn maintenance 

Read your fertilizer’s label for after-care instructions, but it’s generally best to:

• Avoid mowing until two days after the application. 
• Avoid watering the same day as liquid applications.
• Water immediately after a granular application.

FAQ about lawn fertilization

Find a lawn care pro near you

The best way to fertilize your lawn is with the help of a lawn treatment pro. Lawn Love connects you to qualified pros who will make your lawn look lush. We can help with over 30 outdoor services, including lawn mowing, bush trimming, and gutter cleaning.

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