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A Complete Fertilization Guide for Sports Fields (2021)

Updated: Sep 23, 2023

Fertilizing your field can seem like an intimidating, difficult chore. All the ratios and calculations can be confusing to anyone who didn’t major in Organic Chemistry.

Yet understanding the basics of fertilization is essential for the health and beauty of an athletic field. Here’s an uncomplicated, painless breakdown of how the process works.

Why Starting with a Soil Test will Literally Change the Game

Think of your sports field like a dehydrated athlete. Not only does your player need water, but he or she also needs to replace electrolytes. If they don’t have electrolytes, their body can’t function properly. They’ll faint in the middle of the game.

Your field works the same way. A soil test will tell you exactly which “electrolytes” your field doesn’t have plus the exact quantities it needs to be healthy again. You should test the soil at least every 2-3 years, and it costs between $50-200 depending on how much information you want about your soil. If you’re part of a regular maintenance program, soil testing is often provided.

Grass needs 16 key nutrients to grow, but for fertilization purposes, the most important three are nitrogen, phosphorus, and potassium. These are the nutrients your grass probably doesn’t have enough of, and these are the three that will help your grass grow thicker, faster, and stronger. The soil test will tell you the exact concentrations of these nutrients in your soil, plus you can test for the other 16 nutrients as well, which can only help your field.

If you’re ordering the soil test yourself, remember to also ask for the pH of the soil. If it’s higher or lower than 7.0, your grass won’t consume nutrients as it should. Not having a perfect pH will transform cell parts and slow down all grass growth. If the soil pH is above 7.0 (basic) then you need an acidic fertilizer to decrease it. If the soil pH is below 7.0, your soil is too acidic. The elements in the dirt are naturally basic, so this is less common.

In order for the soil test to work, you need to do the sampling right. Follow the instructions on the sample kit and sample from various places on the field. Make sure there are no chemicals or fertilizers on the field that could alter the test results. Another helpful test is to test the grass blade itself, which is known as “tissue testing”. Knowing the nutrient concentrations in the grass tissue can also help determine the right type of fertilizer.

How to Effectively Choose an Awesome Fertilizer

So you have the soil test report.

Now it’s time to pick a fertilizer, and the options are endless. The report will tell you the pH, the concentration of soil nutrients, and it should tell you how much of each nutrient to apply to your field.

Every fertilizer has a fertilizer grade, which is a 3-number ratio on the front of the bag. The first number is the percentage of nitrogen. The second is phosphorus and the third is potassium. For example, 13-13-13 is the most common fertilizer grade. This means the fertilizer contains 13% nitrogen, 13% phosphorus, and 13% potassium. The other 61% is filler or elements that don’t affect the grass.

Why so much? Filler helps “dilute” the mix to prevent the grass blades or roots from getting chemically burned. Some fertilizers contain other elements like iron and calcium, which can be applied to a field if the soil test results say the concentration is low.

Why are nitrogen, phosphorus, and potassium so important? Their effects can be remembered with the phrase “up, down, and all around.” Nitrogen helps grass grow up, phosphorus helps roots grow down, and potassium increases the all-around health of the grass, like disease resistance.

Now a side note: Nitrogen also increases the density and color of the grass. You’ll probably see on the fertilizer bag that there are 2 types of nitrogen: quick-release and slow-release. Quick-release is water soluble (it can dissolve in water) and is immediately available to the grass. Slow-release nitrogen is not water soluble, so it degrades over weeks or months. Slow-release nitrogen costs more and is less efficient per pound, but it lasts longer and has a lower potential to burn your grass. Most fertilizers have a combination of the two. On the bag, fertilizers don’t report the percentages of pure phosphorus and potassium. They use the compound potash, which contains potassium, and phosphate, which contains phosphorus. The actual concentrations of phosphorus and potassium are less than the fertilizer grade ratio but don’t worry. The soil report will recommend the amount of potash and phosphate to apply to your field, so you don’t need to do the math. You just have to follow their guidelines.

Remember: Even though 13-13-13 fertilizer is the most common, it might not be right for your field. Without testing your soil, you can’t know what nutrients it lacks. Applying the wrong concentration could seriously damage your field. For example, you might get your soil test back and find out the potassium concentration is perfect, but you need a lot of nitrogen. The soil test report will most likely tell you how many pounds of each nutrient to apply to 1,000 square feet. Those numbers must be converted into a ratio of fertilizer grade. 13-13-13 is a 1:1:1 ratio. Your field might need a 3:1:1 ratio, which is found in an 18-6-6 bag of fertilizer.

Because the math is kind of tricky, expert help is almost essential. (To learn how to do the math, click here.) Your fertilizer choice also depends on the time of year, the type of grass, and what expectations you have for your field (if you want it denser, greener, etc). Unfortunately, there’s not a “one size fits all” solution, but there are trained professionals who can help you.

So let’s talk price. Hiring out to fertilize your football field ranges from $400-600, depending on the type of fertilizer chosen. Contracting for a regular maintenance program is beneficial because the company should run the soil test for you, pick the top-notch fertilizer on the market, and use the most specialized equipment. If you don’t want to hire out or don’t have the budget, you can do it yourself if you have a staff member with a chemicals license who knows what he/she is doing.

Let’s Get Physical: Granular or Liquid Fertilizer?

You’re ready!

It’s time to pick the type of fertilizer you want. You’ve got two options: liquid or granule. Liquid fertilizers can be bought as a liquid or as a dry powder that is dissolved into water.

The benefits?

Even distribution, for one. It’s also nice because lawnmowers don’t pick it up. Our only warning is to follow the storage and application guidelines, which vary depending on the climate where you live. Granular fertilizers need to have pebbles of uniform size. If not, it won’t get distributed evenly according to Peter Landschoot, a professor at Penn State. Also try to find a fertilizer without a lot of broken granules or a lot of dust, as this ruins even distribution on the field.

Do you have a golf course? If using granular fertilizer for a low-cut field (like a golf course), be sure to use small granules. Every granular fertilizer has a size guide number, or SGN, indicating the average size of the granules in that bag. Golf courses use a fertilizer with an SGN of around 90, while football fields should use bigger granules of around 225.

How to Correctly Apply Fertilizer for Powerful Results


You tested your soil and you know what type of fertilizer you need.

You might be wondering: How much should you buy?

We’ll be honest- determining how much of it you need for your field is also complicated. For example, spreading a 50 lb bag of 13-13-13 fertilizer on ¼ of a field will produce very different results than applying that same bag over the whole field. The key is the recommended rate on the soil test report and the weight of the bags of fertilizer. Again, this is where you want trained experts on your team.

Let’s say you’re fertilizing your field, and you end up with extra. Should you use it all? You think, “If a little fertilizer does a little good, a lot of fertilizer will do a lot of good!”

Nope. That’s not how it works. More fertilizer does not equal better grass. Adding more than the soil report tells you will throw off the nutrient balance in the soil and harm your field, not help it. Too much can be just as harmful as too little.

When To Apply Fertilizer to Maximize Benefit

When, you ask?

Science has your answer:

According to Professor Landschoot, a field with cool-season grass should be fertilized three times a year: late fall, late summer, and late spring.

  1. The most important time is late summer, around the beginning of September. This is to boost your grass field before the crazy hectic fall season.

  2. In the late fall, fertilize with more slow-release nitrogen to last through the winter.

  3. In late spring, around late May or early June, use a mixture of slow-release and fast-release, so that the nitrogen can feed the grass during the scorching summer months.

Want to decrease the cost of fertilizer? Increase the nutrient concentration in your soil, and do it naturally. Replace the plugs pulled during aerification and replace grass clippings. This can increase the nutrients in the soil and decrease the amount of fertilizer you need, thereby decreasing the cost.

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