Fertilizer 101: Tips on How to Apply Fertilizer to Your Lawn

Man seeding and fertilizer a residential lawn

You always dreamed of owning a big yard, but you never imagined how much work came with keeping it green and healthy. Our simple fertilizing tips will take the stress away. 

From picking the right product to fertilizing at the right time of year, our Fertilizer 101 guide has you covered. Don’t know the first thing about fertilizer? Don’t worry –– you don’t need to be a pro to get the greenest lawn in the neighborhood. 

Why is it important to fertilize?

All living things require food to grow. Your soil provides your turf with nutrients, but just like you need a variety of proteins, fruits, and veggies, your lawn needs an array of nutrients, too. Sometimes, your soil doesn’t always have a good supply of various plant nutrients. 

That’s where fertilizer comes in. Fertilizer enhances the soil’s fertility by supplying the nutrients your turfgrass needs to grow strong. 

Whether your turf is enduring drought stress, winter winds, or scorching heat, fertilizer helps improve your lawn’s health. The healthier your turf, the better it wards off pests, diseases, and weeds. 

What do the three numbers on the bags mean?

When shopping for fertilizer, you’ll likely notice three numbers printed on the packaging. These numbers represent turf’s three essential nutrients: Nitrogen (N), phosphorus (P), and potassium (K). Nitrogen is the most important nutrient your grass needs. 

Most store-bought fertilizer bags display the ratio of these three numbers in the order of N-P-K. For example, a package showing 20-0-3 means the fertilizer contains 20% nitrogen, 0% phosphorus, and 3% potassium (also known as potash in the context of fertilizer). 

What are the different types of fertilizer?

The two most common forms of fertilizer are granular and liquid fertilizers. Each type meets your lawn’s needs in different ways. Let’s take a look below to see how they compare:

Granular fertilizer

Granular lawn fertilizer is a dry fertilizer that typically comes in the shape of pellets. Most granular fertilizers are slow-release fertilizers, which means they slowly release nutrients to grass over a long period. 

Users can apply the dry fertilizer with a broadcast spreader, drop spreader, or hand-held spreader. 

Pros: 

✓ Slow-release fertilizer can last on the lawn for several weeks or months, which means you don’t need to apply it as often as quick-release liquid products. 
✓ Slow-release fertilizer promotes long-term grass health.
✓ Granular fertilizers are usually less expensive than liquid fertilizers. 
✓ Granular fertilizers have a longer shelf life than most liquid fertilizers. 

Cons: 

✗ Since granular fertilizer releases its nutrients slowly, it’s not an ideal solution for a dying lawn that needs an immediate nutrient boost. 
✗ Spreading granular fertilizer is more physically demanding than applying liquid fertilizer.
✗ Spreading granular fertilizer uniformly throughout the lawn can sometimes prove difficult. According to the PennState Extension, granular fertilizers that contain significant amounts of dust, broken particles, and different-sized pellets may lead to poor distribution of nutrients. The extension recommends using products with uniform particle sizes and minimal amounts of dust and broken granules.

Liquid fertilizer

Person using a host attachment sprayer for fertilizer
Jerry Norbury | Flickr | CC BY-ND 2.0

Liquid fertilizer is often available as a liquid concentrate that the user must dilute with water. It also can begin as a dry, water-soluble substance that the user must dissolve in water. 

Most liquid lawn fertilizers are quick-release solutions, which means they’ll supply nutrients to the grass immediately after application. 

Pros: 

✓ It gives turf an immediate boost of nutrients. Quick-release liquid fertilizer is beneficial for struggling lawns that require immediate attention. 
✓ Every drop of liquid has an identical ratio of nutrients, creating an even distribution of plant food. 
✓ Applying liquid fertilizer is less labor-intensive than spreading granular fertilizer. 
✓ Quick-release liquid fertilizer typically shows results sooner than slow-release granular fertilizer. If you’re throwing a big event and need to green up the lawn quickly, liquid fertilizer is likely the better choice. 
✓ Because liquid fertilizer provides nutrients right away, it’s an ideal starter fertilizer for new lawns

Cons: 

✗ Because liquid fertilizers provide nutrients quickly, users typically need to reapply liquid fertilizer more frequently than slow-release granular fertilizer. 
✗ Liquid fertilizer can sometimes trigger a growth surge, which isn’t so healthy for an established lawn. A growth surge can stimulate rapid shoot growth and hinder root growth, making the grass vulnerable to stress, pests, and disease
✗ Liquid fertilizer is typically more expensive than granular fertilizer. 
✗ Liquid fertilizer has a shorter shelf-life than granular fertilizer. 

How often should I apply fertilizer?

One to two fertilizer applications per year should be enough to maintain an established lawn’s beauty and health. When and how much you apply will all depend on your lawn’s type of grass and your soil test’s results, which we’ll cover down below.

When is the best time of day to fertilize your lawn?

Early morning is the best time of day to fertilize your lawn. Fresh morning dew provides just enough moisture for your grass to absorb the fertilizer. Avoid fertilizing later in the day. Why? Because the sun can burn your grass. 

Can I spread granular by hand?

It’s best not to spread dry fertilizer by hand. It’s challenging to apply fertilizer evenly without the help of a spreader. Fertilizing by hand is likely to result in uneven patches of green grass, and in many cases, you’ll be able to see the path of your throws appearing as streaks in the lawn. 

Fertilize your lawn in 11 simple steps

1. Conduct a soil test

You can’t give your grass a healthy dose of fertilizer if you don’t know which nutrients the soil is lacking and which it already has. You won’t do your lawn much help if you ignore where the soil is deficient. 

Conducting a soil test is the best way to determine the right amount of nitrogen, phosphorus, and potassium for your turf. At-home soil kits are available, but sending a soil sample to your local county extension office will provide you the most detailed results. 

2. Identify your grass

illustration showing the cool and warm season grasses on the US map, along with the transitional zone

Do you have warm-season or cool-season turf? You likely have cool-season turf if you live up north, where winter is frigid, and summer is mild. If you live down south, where summer is scorching, and winters are mild, you likely grow warm-season grass. 

But what if I’m right in the middle? Between the northern and southern states lies the Transition Zone, where both summer and winter are extreme. If you live in the Transition Zone, you might be growing either warm- or cool-season grass. 

Why grass type matters: Whether you grow warm- or cool-season grass will determine what time of year you apply fertilizer. You want to apply fertilizer during a turf’s most active growing season. 

The best time of year to fertilize warm-season grass is in summer and the best time to fertilize cool-season grass is early fall. Avoid fertilizing your cool-season turf in early spring, as this can trigger an unhealthy growth surge.

Warm-season grasses:

  • Zoysiagrass
  • Bermudagrass
  • St. Augustine grass
  • Centipedegrass
  • Buffalograss
  • Bahiagrass

Cool-season grasses:

  • Kentucky bluegrass
  • Perennial ryegrass
  • Tall fescue

3. Calculate your lawn’s square footage

Calculating your lawn’s size will help you determine how much fertilizer you need for the job. 

You’ll need to calculate your lawn area in square feet. If your lawn has a distinct shape, like a rectangle, circle, or square, then that shape’s area is all you’ll need to calculate. Pretty easy! 

But if your lawn doesn’t have a distinct shape, then you’ll need to: 

  1. Break the lawn up into imaginary shapes 
  2. Calculate the square footage of each imaginary shape
  3. Add each imaginary shape’s area for a total area of the lawn

Need a quick lesson on calculating the square footage of different shapes?

Square: Length x Width

Rectangle: Length x Width

Circle: 3.14 x Radius x Radius 

Triangle: (Height x Base) / 2

4. Calculate how much fertilizer you need 

It’s common for homeowners to over-apply fertilizer, which can negatively affect your turf and the environment. Rainwater washes excess fertilizer away as runoff into streams, rivers, and ponds, creating a toxic environment for aquatic organisms. 

To minimize your fertilizer’s impact, you must apply your fertilizer responsibly, and that includes making the proper calculations. 

Plugging in more numbers might sound daunting, but don’t worry –– there won’t be a Fertilizer 101 exam. 

When fertilizing your lawn, you’ll want to aim for 1 pound of nitrogen per 1,000 square feet. Let’s say your soil test recommends a fertilizer with the N-P-K ratio 29-0-5, which is 29% nitrogen, 0% phosphorus, and 5% potassium. 

The goal is to determine how many pounds of fertilizer you need to spread across the lawn to achieve 1 pound of nitrogen per 1,000 square feet. It’s much simpler than you might think: 

  1. Convert 29% to a decimal, which is 0.29
  2. Divide 1 pound of nitrogen by 0.29. The result is how many pounds of 29-0-5 fertilizer you’ll need to achieve 1 pound of nitrogen per 1,000 square feet. 

(1 pound of nitrogen) / 0.29 = 3.45 pounds of 29-0-5 fertilizer is needed to supply 1 pound of nitrogen per 1,000 square feet.

5. Pick your type of fertilizer

Have you decided on which fertilizer you want to use? Remember, most granular fertilizer is slow-release, which is optimal for long-term grass health. Liquid fertilizer supplies the nutrients immediately but will likely require a reapplication. 

6. Check the weather

After a busy morning spreading fertilizer, you wouldn’t want to see your hard work wash away in a rainstorm. Before you apply fertilizer, check the weather forecast. If it doesn’t predict rain for at least two days after you fertilize, you’re in the clear. 

A small rain shower a couple of days before fertilization is OK, as long as the grass is dry before you fertilize. You’ll need to give your grass a thorough watering anyway, so a small shower means less work for you. 

The bottom line: Don’t fertilize your lawn immediately after a rainstorm, and don’t fertilize when rain is in the forecast. 

7. Prepare your turf

Give your lawn a thorough watering a couple of days before you fertilize. 

Another great way to prepare your turf for fertilizer is to mow and rake the grass. Cutting grass and removing debris helps expose more soil to the fertilizer. 

8. Wear the right gear

Nitrogen in the fertilizer can cause chemical burns on the skin. Keep yourself well protected by wearing gloves, safety goggles, long pants and sleeves, and a dust mask. 

9. Read all product instructions

Misusing fertilizer can cause serious harm to you and the environment. Read all product instructions carefully before fertilizing. Some fertilizer brands may have special instructions that are not mentioned here in our guide. 

10. Apply the fertilizer

Once you’ve calculated how much fertilizer you’ll need, put on the right gear, and read all the instructions, it’s time to get to work. 

Spreading granular fertilizer

There are three tools you can use to spread granular fertilizer:

  • Rotary spreader (also known as a broadcast spreader)
  • Drop spreader
  • Hand-held spreader

How do you decide which tool is best for the job? It depends on your lawn’s size. The University of Arkansas Division of Agriculture recommends spreaders for the following lawn sizes

  • Rotary spreader: Medium to large yards (greater than 2,000 square feet)
  • Drop spreader: Small lawns (less than 2,000 square feet)
  • Hand-held spreader: Best for tiny areas

A rotary spreader is a push-powered tool that looks similar to a small wheelbarrow. You pour the granules into the tool’s hopper, which later discharges the granules through small holes near the bottom. 

Most rotary spreaders allow you to open and close the holes using a lever located at the handle. When the holes are open, the granules flow out and strike a spinning plate which distributes the granules 3 to 5 feet away from the spreader.  

A drop spreader is also a push-powered tool. It has a rectangular hopper with equally spaced holes arranged in a row. The drop spreader doesn’t have a spinning plate that distributes the granules. Instead, the granules drop straight down onto the ground between the spreader’s wheels.  

A hand-held spreader is an excellent tool for fertilizing small areas or tight spaces in the yard. The device is equipped with a handle that you crank to expel the granules.

Once you’re ready to spread the fertilizer, follow these steps

  1. You’ll need to calibrate your spreader to release a certain amount of fertilizer, and many fertilizer products have instructions on how to set the spreader. It’s a good idea to make two passes over your lawn instead of one, so you’ll want to calibrate the spreader to deliver half the desired application rate. 
  2. When pouring the granules into the hopper, complete this step on a driveway, patio, or other hard surface. Otherwise, an accidental spill could harm your grass where excess fertilizer lands. 
  3. Starting in one corner of your yard, push your spreader at a consistent pace around the perimeter. Most rotary spreaders send the granules 3 to 5 feet away from the spreader. Position your spreader so that the granules land right at the edge of the bordering driveway, sidewalk, or patio. 
  4. Once you’ve walked along the whole perimeter, it’s time to make the first pass inside its border. Position the spreader within the perimeter. Starting from one corner, walk forward straight. If you’re using a rotary spreader, pay close attention to where the fertilizer lands.
  5. Once you’ve reached the perimeter, turn the spreader and walk forward again, leaving enough space between where the previous granules landed and where the next batch will land. 
  6. Continue walking in straight lines parallel to your last pass. If you’re using a rotary spreader, keep a few feet in between your rows.  If you’re using a drop spreader, you don’t need to leave any space in between your rows. 
  7. After covering the whole lawn, turn 90-degrees and make your second pass across the yard, creating a grid pattern. 
  8. Once you’re done fertilizing, take a leaf blower (or broom) and blow any excess fertilizer that landed on the driveway, sidewalk, or patio back onto the grass.
illustration showing how to spread fertilizer

Spreading liquid fertilizer

Liquid fertilizer often comes in a spray bottle which you attach to the garden hose. Attach the spray applicator to the hose and spray the fertilizer evenly across the lawn. Avoid an uneven application; otherwise, you risk overfertilizing some areas and killing your turf. 

Don’t apply liquid fertilizer on a windy day, as the wind can disrupt your application. 

11. Follow post-application instructions

This last step will vary depending on your fertilizer brand. Some products require light watering after applying fertilizer, while others recommend delaying water. 

Graduate Fertilizer 101 with a healthy lawn

Greening up your lawn needn’t feel like an impossible chore. With the right tools, fertilizer, and calculations, you can get the job done with ease. 

Taking shortcuts –– like skipping the directions, spreading by hand, or fertilizing before a storm –– might be tempting, but it will be a waste of time, effort, and money. 

Haven’t got the time to maintain the yard? Hire a local lawn care professional to feed the lawn for you. When you hire a qualified professional, you won’t have to worry about over-applied fertilizer or your turf looking spotty. Even better, a pro can handle the mowing, trimming, and edging. Just sit back, relax, and leave your turf in good hands. 

Main Photo Credit: Shutterstock

Jane Purnell

Jane Purnell is a freelance writer and actor in New York City. She earned her B.A. from the University of Virginia and enjoys a warm cup of French press coffee.