Here Is What the Numbers on a Spreader Mean: All the Details.

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You’ve got your fertilizer ready, gardening gloves are on, and you grab your spreader prepared to feed your lawn essential nutrients. But then you can’t really figure out what settings to use on your spreader? Understanding what the numbers on your spreader mean is important to properly distribute your fertilizer appropriately in desired areas for the overall health of your lawn and vegetation. 

The numbers on a spreader tell you how much fertilizer or product will be applied over a certain amount of land. You’ll use these numbers, often guided by the instructions on the fertilizer, to determine the most effective way to spread the product.

Below, you’ll learn what the numbers mean on both the fertilizer and spreader and how to calibrate your spreader. We’ll also explore the types of spreaders and their potential benefits and drawbacks. 

What the Numbers Mean on Your Spreader and How To Calibrate It

Each spreader is different and can be affected by variables such as the model, age, condition, and how fast and consistently you walk when applying fertilizer. After use, you should follow the manufacturers’ guidelines for cleaning, lubrication, and storing your spreader.

After you have purchased your spreader, you’ll see a range of numbers on it. These numbers represent settings for distributing the fertilizer, and they’re essential since they determine how fast the fertilizer will get applied to the ground. If you don’t adjust your spreader to the numbers on your fertilizer, you may end up with an uneven and patchy lawn.

What the Numbers Mean

For example, numbers such as 5, 5½, and 18½ on the spreader represent different fertilizer application rates over a specified amount of square footage. This calibration will vary depending on the type or size of the granules of fertilizer that you’re spreading and controls how fast the fertilizer will leave the opening in the hopper. 

Numbers on the fertilizer bag that appear like this, 10-20-15, represent the percentage of the nutrients Nitrogen (N), Phosphorus (P), and Potassium (K), respectively, which may be referred to as NPK. NPK is specially formulated for different growing needs to grow healthy plants.

You must correlate the numbers on the spreader with the numbers on the fertilizer bag so that your grass is getting the proper amount of nutrients. This requires calculation per square foot to adjust your spreader accordingly. Settings will depend upon the type of spreader you’re using as well.

The settings on your fertilizer spreader are usually dependent on the type of spreader and the type of fertilizer you are using. You can check your bag of fertilizer to see if any guidelines are there. However, it may be possible that you won’t have access to this information. If this is the case, there are some general ways you can calibrate your spreader to apply your fertilizer.

What Settings To Use for Your Spreader

Here are the steps on how to determine calibration for your spreader:

  1. Look at your fertilizer bag to see the square footage that it covers. Divide that number by 100.
  2. Multiply the weight of the bag by the number you got.
  3. Use the answer you have to determine the amount of fertilizer you need to cover 100 square feet (9.29 sq. m). This works for broadcast spreaders. For a drop spreader, you’ll need to determine the required length by the width of your spreader and then apply the same process using those numbers.
  4. Place this amount in your spreader.
  5. Mark a 100 square foot (9.29 sq. m) area of your lawn that is 10×10 ft (3.05×3.05 m).
  6. Apply fertilizer using the suggested setting if it’s indicated on the bag. You may have to monitor and adjust to get the correct application rate if not. If the fertilizer runs out before the marked-off area is done, decrease the setting. Mark off another area and try again to observe if any fertilizer is left. But if the fertilizer is still left in the spreader, increase the setting. Mark off another area and try again, paying attention to the fertilizer usage.
  7. Once you’ve figured out the right setting to calibrate for your fertilizer, write it down on the bag, so you remember for the next time.

Here’s a YouTube video about “DIY Lawn Care,” to help you out:

It’s also important to note that you should first mow your lawn before using fertilizer and read the fertilizer’s application directions. Some types will ask you to make two passes or walk twice over the areas you wish to fertilize, applying 50% of the product as you walk in one 

direction and then the other 50% in the opposite direction.

Is There a Difference Between Settings (Numbers) for a Broadcast Spreader or Drop Spreader?

If you’re not using your hands to scatter fertilizer, there are two main types of mechanical spreaders that you’ll probably be using. They are:

  • Broadcast spreaders
  • Drop spreaders

There is a difference between settings for a broadcast spreader and drop spreader given that they distribute product differently. Even if the settings themselves are similar, broadcast spreaders may be more difficult to calibrate given that measuring the fertilizer output is more difficult. 

That being said, all mechanical spreaders will have a hopper, the bucket-like part that holds the fertilizer, and an adjustable opening. 

The opening allows the user to control how much fertilizer is distributed at a time. Consider your lawn and preferences before selecting the type of spreader you want to use.

Choosing Between Drop Spreaders and Broadcast Spreaders

Both types of spreaders are useful, and the one that’s right for you will depend on various factors, including your lawn size. We’ll look more closely at each type down below. 

Drop Spreaders

Drop spreaders are known for their accuracy in distributing even rows of fertilizer in exact places. This makes them an ideal choice for fertilizing small areas. This style also helps to reduce the spread of fertilizer as loose contamination onto walkways or roads. Don’t open the opening to release fertilizer until you start walking.

When using, you should overlap the wheel marks to cover all that needs fertilization. If you don’t make adjacent paths as you walk, you may miss patches or strips of the ground. Missed spots will create color variances, and you might see stripes of different shades of green or brown on your lawn. 

The pace at which you walk will affect the concentration of how much product falls to the ground. Try your best to walk at a brisk and consistent pace. Close the opening when you reach the end of your path while still moving. If you leave the gap open while you stop or turn, too much fertilizer may fall out on that part of the lawn or vegetation.

If you need a review of these steps, you can check out this YouTube video:

Benefits of a Drop Spreader

  • They’re easy to operate and navigate obstacles, corners, and tight spaces.
  • The user can have precise and controlled coverage, thus keeping the product off paths and walkways.
  • The distribution of fertilizer won’t be significantly impacted by wind.
  • Less product will end up on your driveways, walks, and paths.

Potential Drawback of a Drop Spreader

  • They cover small areas at a time, meaning it’ll take you longer to fertilize. If your lawn is over 5,000 square feet (464.52 sq. m), this type of spreader may not be your best option.

Broadcast Spreader

A broadcast spreader is also known as a rotary spreader and comes in two different types; walk-behind or handheld. This spreader will distribute fertilizer in all directions in a fan-like pattern. Broadcast spreaders cover a more expansive (broader) area as you walk with it.

Like the drop spreader, the rate you walk and the size of the application opening will affect how much fertilizer comes out. However, it’s important to note that the outer edge of the “fan” distribution will naturally have less product. The manual for your broadcast spreader can provide information about how far different types of fertilizer will travel from the spreader.

When using this kind of spreader, you should also make sure to overlap wheel marks, making adjacent paths as you walk to avoid creating missed spots that result in color variances and growth in your lawn. However, this spreader is more forgiving due to the way it disperses fertilizer, so it’s okay if your paths aren’t as straightforward or overlapped.

To use a handheld broadcast spreader, place it on a flat surface and fill it with your fertilizer. There’s a handle to hold the weight of the spreader and a crank for the other hand. You hold the spreader at a right angle perpendicular to your torso in front of you, walking consistently and cranking the handle to distribute the fertilizer.

For a quick and upbeat review of what to do, here’s a YouTube on using a walk-behind broadcast spreader:

You can also watch a YouTube video about using a handheld broadcast spreader:

Benefits of a Broadcast Spreader

  • These are ideal for larger lawns with a greater coverage area so that you can fertilize more area in less time.
  • You have the option of walk-behind or handheld models, so you can choose what you’re most comfortable using.
  • The hopper bin of a walk-behind style usually holds more product, so you save time without having to do as many refills.
  • Some broadcast spreaders come with a side-shield feature. This allows you to turn off half of the spreader. This gives you the option to apply fertilizer around the perimeter of your lawn to keep it off of pathways and driveways.

Potential Drawbacks of a Broadcast Spreader

  • The fan-like distribution can cause products to land in spots where you don’t want them. This can be especially problematic if your fertilizer has a pesticide in it, causing problems for nearby vegetation and flowers. If it lands on hard surfaces and walkways, it can run off into water sources, unsuitable for the environment.
  • Handheld spreaders can also lead to application in undesired areas, especially if you don’t hold the spreader steadily in front of you. It’s also higher above the ground and can spread farther in the wind, potentially causing damage to nearby vegetation, pathways, and flowers.
  • A handheld spreader’s design might not work for you if you are left-handed.
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