The 2021 Beginners Guide to Lawn Fertilizer


Jan 01, 2021

Share the Love!

As a homeowner, one of the first things you’ll learn is your yard is the gateway to a great-looking home. It’s the first thing people see as they approach your front door, and a yellowing, dying carpet is a quick way to make a bad first impression. That’s why we’ve put together the 2021 Beginners Guide to Lawn Fertilizer.

Lawn fertilization is so crucial, as it ensures your grass gets the nutrients it needs to stay green and healthy for the long haul.

Sure, you can pay someone hundreds or even thousands of dollars per year to handle this for you, or you can do your own fertilization and save that cash. Our Beginner’s Guide to Lawn Fertilization will put you firmly on the path of saving all that cash by doing it yourself.

In This Guide

You can use the quick links below to access specific parts of this guide.

What is NPK?
Fast vs Slow Release Fertilizers
Organic and Inorganic Fertilizer
Liquid vs Granular
Which Fertilizer Does My Lawn Need?
Creating a Fertilization Schedule
Knowing How Much Fertilizer You Need
Application Methods
Monitoring Your Results

Grass Grows Naturally. Why Fertilize?

It’s common to hear the old argument that grass grows naturally and looks just fine in the pastures and fields, so there is no need to fertilize my lawn. While it is true that grass grows wild across the U.S. and may look stunning from a distance, things get muddied up once you get into residential application.

Residential Expansion

We can all see just how wild residential expansion has gotten over the years, as new developments seemingly crop up overnight and spread like weeds. This insane expansion has forced developers into areas that may have less-than-favorable soil conditions, especially in coastal areas like Florida and desert areas like Arizona and parts of Texas.

These developers often lay sod to make the lawns look great when the new owners move in, but without proper care, these beautiful lawns can regress to a barren wasteland.

This is where fertilization plays a huge role. With the right fertilization program, you can keep the soil full of all the nutrients your lawn needs to remain lush year-round, despite the sandy or rocky conditions just a few inches below it.

Creating the Best Fertilization Program for Your Lawn

When you decide it’s time to take control of your lawn and launch a fertilization program, the last thing you want to do is run to the nearest store, grab the first bag you see labeled “fertilizer” and dump it on your lawn.

The best fertilization programs take careful testing, planning and scheduling. They also take a certain amount of commitment to keep your lawn green and lush. This is why so many homeowners unnecessarily pay professionals hundreds to thousands of dollars per year to fertilize their lawns.

Understanding Fertilizer Grades

The 2021 Beginners Guide to Lawn Fertilizer 1

The first step in creating the best fertilizer program for your lawn is understanding the product you’re using. This starts with figuring out what in the world those numbers on the front of the fertilizer bag mean.

On most bags of fertilizer, you’ll find three bolded numbers separated by dashes. This is the fertilizer grade.

The first number indicates the percentage of nitrogen in the fertilizer, the second number is the percentage of phosphorus and the third is the percentage of potassium. Many simply call this series of numbers the N-P-K.

If you grab a 50-pound bag of 10-10-10 fertilizer, you have 5 pounds of nitrogen, 5 pounds of phosphorus and 5 pounds of potassium in each bag. The rest of the fertilizer is made up of other fillers, including limestone or sand.

Some fertilizers may only have one of those three essential nutrients in them too, which helps when your lawn needs just one nutrient boost.

Star Tip: Some states have banned phosphorus in retail sales, so you will notice that the second number on every bag is a “0.”

Release Rates

Another critical variable in fertilizers is the release rate. There are only two options here, fast and slow release.

Fast-Release Fertilizers

Fast-release fertilizers are generally water-soluble and deliver immediate nutrition to your lawn. These are great for treating urgent issues between your standard fertilization times. You must use with care when applying these types of fertilizers. With fast-release nutrients, if you overapply, there is a higher risk of the fertilizer burning your grass so follow the instructions carefully.

Slow-Release Fertilizers

Slow-release fertilizers are the pillar on which you build your lawn care program. This is because of the longevity and practicality of using slow-release nutrients. These fertilizers give the soil a delayed and steady release of nutrients over the course of several weeks. The slow drip of nutrients produces longer lasting results and decreases the risk of over fertilizing and burning your lawn.

Can I Mix Slow- and Fast-Release Fertilizers?

Of course! You just have to be mindful of timing and how much fertilizer your throwing down on your lawn. Remember, too much of a good thing can be a bad thing. It’s important to keep track of your last applications and understanding the release rate of the fertilizers you use. Poor timing and miscalculations here will do more harm than good for your lawn.

Luckily, there are plenty of products (more commonly liquid solutions) on the market that utilize both fast and slow release nutrients in a single fertilizer, so you get the best of both worlds. These solutions ensure there are plenty of quickly available nutrients in the soil to kick off growth and enough long-lasting nutrients to sustain it.

Organic and Inorganic Fertilizer

Another option in the wild world of fertilizer is organic or inorganic. To start, the terminology can be confusing since words like organic, inorganic, natural, artificial and synthetic are thrown around so casually on product labels. Luckily, the options can be broken down to either organic or inorganic fertilizers.

Organic Fertilizer

Typically, when you see the words “organic” or “natural” on the label this simply means that the product is minimally processed, and the nutrients remain in their natural forms, rather than being extracted and refined.

Organic fertilizer is derived from plants or animals and is generally thought to be reserved for gardens. Though, this is not always the case as some folks prefer it in their yards as well to help condition and feed the soil.

Some examples of organic fertilizer include compost, manure, and fish emulsions, but there are also commercially available organic blends that mix several types or contains specific nutrients into one bag. There are plenty of organic based fertililzers on the market and a quick search on the internet will help you find out which one is right for you.

Inorganic Fertilizer

Inorganic fertilizer is made up of partly, or all synthetic materials and chemicals that contain the nutrients your lawn needs. Because it is already in a consumable form for grass, inorganic fertilizer delivers nearly immediate nutrition.

When planning your fertilization, remember that organic fertilizers release its nutrients significantly slower than inorganic. Both fertilizer types have their place in lawn care. Finding a balance between both inorganic and organic, or using a product that blends both types can cause a powerhouse effect and really take the health of your lawn to a new level.

Liquid and Granular

The final key category to know about is liquid vs granular. Whether you’re using a liquid or a granular fertilizer, there is no difference in the total amount of nutrients being supplied. You may need to apply more frequently depending on the type of product you use, but the end result is generally the same when done correctly. Although, each application method has their differences, you can choose one or the other, or find a balance of using both that enhance your lawn’s health and works best for you.

Granular Fertilizer

This is a dry fertilizer in a granular form that you can apply by using a broadcast spreader.


  • Cheaper in bulk
  • Longer shelf life if stored properly
  • May only need two or three applications throughout the year
  • Great option for low maintenance lawn care


  • Higher risk of burning the turf if over applied
  • Difficult to apply evenly
  • Nutrients are absorbed into the lawn slower
Liquid Fertilizer

This is a fertilizer that comes as a liquid or a crystal that you mix with water.


  • Great for beginners because of low burn potential formulas
  • Can blend with other liquid products
  • Nutrients are made bioavailable quicker
  • Coverage is well balanced and applications are more efficient


  • More expensive than granular in most cases
  • Requires more frequent applications throughout the growing season
  • Applications are more weather dependent than granular

Which Fertilizer Does My Lawn Need?

The 2021 Beginners Guide to Lawn Fertilizer 2

Figuring out the right fertilizer for your lawn can often be the hardest part of maintaining healthy turf. But it is also the most important part, as applying the wrong type of fertilizer can cause even more damage.

The first step to determining the type of fertilizer you need is a soil test. This will check the pH levels and let you know if your lawn is too acidic or alkaline. Understanding your pH and how to adjust it is the first step to cultivating a healthy lawn and boosting the results of any fertilizer program you’ll be doing in the future.

If the test shows a pH under 5.5, then the soil is too acidic and requires a lime application to help raise the pH to a more neutral level. If the pH is over 7, it is too alkaline and needs a fertilizer with sulfur to lower the pH. The goal here is to have a soil with a pH of 7 or slightly acidic.

Soil goes well beyond pH levels, though. You also need to know what nutrients your lawn needs. Many soil tests will tell you where your soil is lacking and the right type of fertilizer to spread for the best results. For example, if your soil requires a nitrogen boost, the test may recommend a 30-0-0 fertilizer.

These soil tests vary greatly. Some are for folks who are familiar with tests and have no issue performing the testing process themselves. Others are more hands-off and require you just to collect a few samples and send them away for analysis. In some areas, there are also professional services you can call to come and collect the soil samples for you.

Star Tip: A good rule of thumb is you should be testing your soil every 1-3 years. Doing a soil test regularly is a great way to find out what your lawn needs. Keep in mind the frequency of when you should do a test will depend on the type of soil you’re working with.

If you’re between seasonal fertilization and notice your lawn is browning or thinning out, the last thing you want to do is drop random fertilizer on it. Too much of any of the nutrients can cause burning or other problems. This is where a soil test will also help. Once the test returns, you will know exactly what your lawn needs to thrive again.

Creating a Fertilization Schedule

It’s recommended to fertilize your lawn between two and six times per year (for granulars), and every two to four weeks during the growing season (for liquids), depending on your lawns nutrient needs, method of application, and desired results. The specific times to feed depends on the type of grass in your yard. It is important to note to only fertilize your grass when it is actively growing. Fertilizing while your grass is dormant or transitioning into dormancy can add unnecessary stress to your lawn and have long lasting negative effects.

Star Tip: It’s important to note that your lawn’s fertilizing needs may very depending on if you are actively grasscycling after every mow. Grasscycling is the natural recycling of grass by leaving clippings on the lawn when mowing. This process naturally fertilizes your lawn and can provide 15-20% or more of a lawn’s yearly nitrogen requirements.

Fertilization Schedule for Cool-Season Grasses

If you live in a region that battles the cold or just have a very shady yard, you likely have a cool-season grass like bluegrass, rye or fescues.

Cool-season grasses do best when they receive their nitrogen in early spring and late summer through fall. It is important to keep an eye on soil temperatures when planning out a fertilization program as you will have different milestones to consider.

A great rule-of-thumb here is to start fertilizing when your soil temperatures reach 55F and to stop fertilizing when they reach 75F in late spring/early summer. Once soil temps drop back down 70 degrees in fall you can pick up fertilizing again until they drop below 55F in early winter.

If you have a cool season grass, lucky for you, things are pretty simple. Barring no major nutrient deficiencies you are aiming to add between 2-4 pounds of nitrogen to your lawn per year. This should be your benchmark.

Fertilization Schedule for Warm-Season Grasses

If you live below the Mason Dixon line, there is a good chance you have a warm-season grass like bahiagrass, bermudagrass, St. Augustine, centipedegrass, and more. These grasses thrive in the hot southern sun but struggle when the weather cools or if they’re in too much shade.

Because warm-season grasses are more nutrient-specific, you need to know what primary type of grass makes up your lawn. Unless your lawn is new, there is a good chance you have a blend of sorts, but knowing the dominant species will help you determine how much nitrogen it needs to thrive.

The amount of nitrogen common warm-season grasses need per year is as follows:

  • Bermudagrass: 2-5 pounds per 1,000 square feet per year
  • Zoysiagrass: 2-4 pounds per 1,000 square feet per year
  • Centipedegrass: 1-2 pounds per 1,000 square feet per year
  • St. Augustine: 2-5 pounds per 1,000 square feet per year
  • Buffalograss: 1-2 pounds per 1,000 square feet per year
  • Bahiagrass: 2-4 pounds per 1,000 square feet per year

Warm-season grasses are easier to manage than cool-season grasses because they become active in late spring and go dormant in the fall. This gives you a consistent and broad growing season for fertilization. Basically, once the soil temperature rises above 60 degrees, kick off your fertilization program. Once it dips below 55 degrees F, cut it off.

If you happen to live in the deep south, where soil temperatures seldom fall below 55 degrees F still scale back the fertilization in the cooler months. Remember, you only fertilize when your grass is actively growing. If your grass has significantly slowed down its growth and is turning yellow in some parts this a good indicator to give fertilizing a break for a little while until the weather warms up again.

If you’re not sure when your soil temperatures are 55 degrees F or higher you can buy a soil themometer (or cooking thermometer) off of amazon for about 10 bucks.

Like cool-season grasses, a 16-4-8 grade fertilizer is a nice balance for warm-season grasses. The only exception is if soil tests reveal nutrient shortages that require a different grade.

Getting into a Fertilization Routine

Sometimes, the hardest thing about fertilizing your lawn is getting into a routine of doing it. This is where technology and a little creativity help.

We are busier than ever today with life, work, kids, soccer games, doctor visits, etc. Sure, you can write down the fertilization dates on a calendar – and then forget to look at it. Fortunately, almost everyone has a portable scheduler in their pockets that’ll even play a cool jingle when it’s time to fertilize – your cell phone.

Use your cell phone’s calendar app to create an alert every three weeks, the first week of each month or whatever schedule you need to keep your grass happy. Set it to remind you a few days in advance so you don’t accidentally set plans over this critical date.

After a while, this will all become second nature, and you’ll no longer need that alarm.

Knowing How Much Fertilizer You Need

The 2021 Beginners Guide to Lawn Fertilizer 3

Now comes the fun part. Time to feed that lawn. You can’t just roll out and start tossing fertilizer like birdseed. You need to know at what rate to apply the fertilizer based on your lawn size and what the best application method is for your lawn.

Knowing how much fertilizer you need starts with the size of your yard. You can do this the old-fashioned way and use a tape measure or measuring wheel, or you can get a little more technologically advanced and use online estimators. We have a full article about measuring your yard. Check it out before diving into this all-important project.

From there, you can use the fertilizer grade and the amount of fertilizer you need to spread to determine how much fertilizer you need.

For example, if you have a 4,000-square-foot lawn and plan to drop 1/2 pound of nitrogen per 1000 sq.ft. in this round, you will need 2 pounds of nitrogen to get the job done. Picking up a 30-pound bag of 10-10-10 should do the trick.

Star Tip: It’s important to know that sometimes light and frequent fertilizer applications to get the “pounds on the ground” (such as with liquid fertilizers) can be healthier for your lawn and the environment.

Fertilizer Application Methods

There are various ways to apply fertilizer. The best way is to figure out first what works for you while giving your lawn the nutrients it needs.

Broadcast Spreader

A broadcast spreader is a go-to method for most do-it-yourselfers when applying granular fertilizer. Whether it’s an electronic handheld spreader, a manual handheld spreader, a walk-behind, or a tow-behind spreader, they all work the same way. You set the rate of application and walk or drive. With the handheld units, you must also crank or hold the trigger while walking.

Walk- and tow-behind spreaders have the added benefit of pacing their broadcast with your walking or driving speed, providing the most accurate applications. Handheld spreaders, on the other hand, allow you to get into crevices the walk- or tow-behind does not.

Broadcast spreaders make quicker work of your fertilization duties, as they drop the granules on a spinning wheel and throw them out a few feet. With this speed comes far less accuracy, though.


A sprayer is the go-to method for people wanting to apply a liquid product to their lawns. Similarly, to broadcasters they are either hand-held, push, or tow behind where you set the rate of application before you spray.

The big difference here is that you’re adding water into the equation. Luckily, most sprayers are very simple to use and most liquid products will come with an application guide so you know exactly how much water you’ll need to apply the product. Some bottles will even do it for you!

An added benefit to sprayers is that they can be much more accurate than broadcasting and can eliminate the need to further “water in” your applications. This gives you a more holistic approach to fertilizing saving you some time.

Monitoring Your Fertilization Results and Adjusting

The 2021 Beginners Guide to Lawn Fertilizer 4

As a nonprofessional homeowner, the key to ensuring your fertilizing your lawn the right way is constant monitoring. Are you out tossing the football with the kiddos or just enjoying a drink with friends on the porch? Try to have one eye on your lawn looking for signs of malnutrition.

Signs of Lawn Malnutrition

Your grass never hides its feelings and will let you know when it needs more nutrition. When your lawn is malnourished, you will generally notice it turning from a lush green to light green or yellow. In some cases, you will only see patchy yellowing, which indicates you missed a spot when fertilizing.

Star Tip: If you’re not sure where to start or what’s effecting your lawn we’ve written a helpful guide to spotting common nutrient deficiencies in your lawn.

Fixing the Malnutrition Issue Now

If the malnutrition issue has gotten to the point where a patch of grass or large portions of your yard are more yellow than green, you may want to take immediate action.

Start by getting a soil-testing kit online or from a landscaping store and finding out what nutrients your lawn is lacking. Once you know the culprit in your yellowing lawn, you can pick up some fast-release fertilizer that’s heavy on the nutrient your lacking and apply it for a quick regreen between fertilizations.

Fixing the Malnutrition Issue Long Term

The immediate fix is great for now, but those nutrients will not last. The long-term fix is to adjust the fertilizer grade you’re using to one that has more of the nutrient your soil lacks.

If you need more nitrogen, you may need to bump to a 30-0-0 fertilizer. Need more phosphorus, you may need a 8-16-8 fertilizer next time. If you’re low on potassium, you may want to supplement your next fertilization with a 0-0-29 fertilizer.

Continue running soil tests to ensure the nutrients are getting your soil levels back where they should be. If they are still low, you will want to consider aerating your lawn and dethatching to help clear a path for the nutrients on your next fertilization.

Once you get consistent readouts of a balanced, nutrient-rich soil, you can revert to your regular fertilization schedule and product.

Got questions? The lawn experts at LawnStar have got you covered. Just shoot us a note at [email protected]. We’d be happy to help!