What Do The Numbers Mean on Fertilizer Spreaders?

by Alex Kountry
Updated on

Have you ever wondered what the numbers on a fertilizer spreader mean ?

After buying your fertilizer spreader, you notice a range of numbers on the body of the spreader. 

Numbers on fertilizer spreaders usually mean the settings to place the spreader for effective distribution of fertilizer.

For do-it-yourself applications of fertilizer with spreaders, most people usually get it wrong because the numbers on the fertilizer are not properly adjusted and just end up getting patchy and uneven lawns. 

These numbers have their uses and it is important that you know what they mean because they usually determine how fertilizer gets applied to the soil.

This article will serve as a guide on how to know the meaning of the numbers on your fertilizer spreader and how to set them to get the most out of your fertilizer.

What Do The Numbers Mean?

What Do The Numbers Mean on Fertilizer Spreaders

For fertilizer spreaders the numbers usually represent the amount of fertilizer that is to be applied over a specific square feet of land.

On spreaders you can find numbers such as 5, 5 and a half or 18 and a half.

There are usually three numbers on a fertilizer bag label which could come as 10-10-10 or 25-15-15 or 10-0-0.

The first thing to understand about the numbers is that they are values for macronutrients used on plants and crops.

These macronutrients are known as NPK. N stands for Nitrogen, P for Phosphorus and K for Potassium.

Proper knowledge of these macronutrients is also good for you so you can know which is more important for the kind of plant or crop you are growing.

You can always read up about NPK and fertilizer application.

Correlating the numbers on the fertilizer spreader to the numbers on the bag is important.

To do this, you are required to calculate the right amount of the fertilizer per square feet and then adjust your spreader setting accordingly.

What Settings Should My Spreader Be On?

A fertilizer spreader settings are the rate at which the spreader applies the fertilizer or other products to your lawn.

The settings on your fertilizer spreader is usually dependent on the type of spreader you are using.

Because the various fertilizer spreaders have different settings, the setting you will use for a broadcast spreader will be different from the setting for a drop spreader.

For example, a drop spreader usually drops the fertilizer to the area directly under it while a rotary spreader disperses the fertilizer evenly with a wheel.

Usually on the bag of fertilizer there are guides on how much fertilizer is to be applied per 1000 sq. feet of land and recommended spreader settings for the product.

This information usually correlates the product with various spreader models and types. 

However not all the fertilizer bags usually come with this information and your particular model of spreader might not be included in the guide

Also, though the recommended spreader settings makes the process easier it does not always deliver the required amount of fertilizer which can lead to a waste of time and resources. 

This is usually due to a number of  variables such as the age of the spreader, the condition, type and your rate of walking.

The best way to ensure proper and even application of the spreader is to calibrate the spreader to determine the exact amount of fertilizer for your lawn or yard. 

We will explain how to properly adjust your fertilizer setting next.

Related: Here is an article I wrote on the uses of a fertilizer spreader

How Do You Adjust a Fertilizer Spreader?

Adjusting your fertilizer spreader or calibrating is the right way to get the best out of your spreader for even application. To do this there a few steps you would have to follow and we will explain them:

  • The first step in calibrating your fertilizer spreader is to calculate the amount of fertilizer needed per 100 sq ft. This is done by dividing 100 sq. ft by the square ft area the fertilizer is supposed to cover.
  • The number obtained from this is then divided by the weight of the fertilizer bag. For example if the fertilizer is supposed to cover a total area 5,000 sq. ft and the fertilizer bag weighs 25lbs then it will be: 25 lbs x (100sq. ft / 5,000 sq. ft) = 0.5lbs
  • This means that 0.5lbs worth of fertilizer is to be applied for every 100sq. ft area. This amount is placed in the spreader.
  • For broadcast spreaders, it is advisable to start off  with a 10ft x 10ft area which is 100 sq ft. For drop spreaders however the required length is determined by the width of the spreader. 
  • Apply the fertilizer using the suggested setting.
  • However if the fertilizer is used up before you completely cover the area, decrease setting and then start off on another 100sq feet until the correct amount setting is achieved.
  • Also if the fertilizer remains after the area has been covered up, increase the setting and then start off on another 100 sq feet until the correct amount needed is achieved. 

 What is the Best Ratio For Lawn Fertilizer Spreader?

Like we said earlier the fertilizer you apply to your lawn is basically made up of macronutrients.

And those macronutrients include Nitrogen (N), Phosphate (P) and Potassium (K) which is usually known as NPK.

The basic purpose of applying fertilizer to the lawn is to get a healthy, lush and full grown lawn.

Therefore it is important that the right ratio of these macronutrients are applied to the lawn to get the best effects.

Typically while shopping for fertilizer, various fertilizer bags can come with numbers printed on the label.

These numbers refer to the percentage of each macronutrient available in that bag. 

So a bag with 20-20-5 means that there is 20 percent Nitrogen, 20 percent phosphate and 10 percent potassium available in the bag while the rest is made of materials that ensures even and uniform application of the fertilizer.

The ratio of each macronutrient that would be applied to the soil is dependent on a number of factors such as:

  • Soil type
  • Planting season e.g spring, fall, summer etc.
  • Purpose of fertilization
  • Fertilizer type e.g. fast release or controlled release fertilizer
  • Grass type

Nitrogen is the most required of these macronutrients by the soil and as thus it usually comes first in the fertilizer number label.

Also the concentration of nitrogen in the fertilizer usually determines the amount of fertilizer that will be applied to the soil. 

To get the most effective fertilizer ratio for your lawn you have to assess the factors above; however some recommended ratios of NPK lawn fertilizers include 3:1:2, 4:1:2 or 5:1:2. 

This easy guide to fertilizing lawns also explains more about the ratio of the macronutrients, the best periods for fertilizing your lean, the interludes you should have between fertilizer application and the right quantity of water that should be applied to get the best results out of your lawn.

How Do You Set a Scotts Broadcast Spreader?

The Scotts-Miracle Gro is a leading brand in production of lawn care products, fertilizer and fertilizer spreaders, grass seeds among a host of other things. 

If you recently purchased a Scotts broadcast spreader and stumped about how to properly calibrate it to give you the best results for your lawn here are easy ways to go about it.

The Scotts broadcast spreader is easy to use and usually comes with instructions in the owner’s manual.

However we will make the process easy for you by explaining how to set your spreader in 4 easy steps. 

  • Check your lawn fertilizer bag for information on what setting to place your Scotts Broadcast Spreader. It is important to note that various fertilizers might come with different setting instructions depending on the ratio of NPK in it.
  • The dial for adjusting the rate at which the fertilizer is applied is usually located on the same side as the handle of your Scotts spreader. This dial is usually orange and numbers ranging from 2 to 15 will be printed around it.
  • For a higher setting, turn the dial clockwise while you turn anti-clockwise for a lower setting. High settings on a Scotts spreader will usually range from 10 to 15.
  • For larger granules of fertilizer turn your Scotts broadcast spreader to a higher setting while for smaller granules turn your spreader to a smaller setting. 3 to 5 are usually considered low settings on a Scotts broadcast spreader. 

With those four easy steps, you can start using your Scotts broadcast spreader to achieve the best results on your lawn.

 How Do I Choose a Spreader Setting?

Choosing the best setting for your spreader to achieve maximum effect from the fertilizer is very important. 

Recommended settings usually come with both the fertilizer spreader and the fertilizer bag you are working with.

Some important thing you need to note to choose the best spreader settings include:

  • Type of fertilizer: different fertilizer comes with different instructions. So if you have recently changed your lawn fertilizer type, you need to look up the label to discover which settings work with your fertilizer spreader model.

Also fertilizer could come in large or small granular forms. Larger granules require a larger hole and as such you need to set your spreader to a higher setting while for smaller granules, the hole should be smaller hence a lower setting.

  • Walking Speed: for broadcast spreaders the rate at which you walk affects the spreading ratio and pattern so you have to ensure that your walking speed matches the amount of fertilizer that is actually supposed to be applied.
  • Calibration process: effectively following the calibration process for your spreader will help you choose the best settings.

In this article we have been able to explain what the numbers on fertilizer spreaders mean and how it is essential to the lawn fertilizer application process.

How you set your spreader significantly affects how much fertilizer gets impacted into your soil.

With this guide however, you can confidently go out to get your spreader, and begin the fertilizer application process.

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About the author

Alex Kountry

Alex Kountry is the founder of HayFarmGuy and has been a backyard farmer for over 10 years. Since then he has decided to write helpful articles that will help you become a better backyard farmer and know what to do. He also loves to play tennis and read books


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