Granular Broadcast Treatment
Using a Spreader and Calculating Rates
A broadcast application, aka blanket application when using liquids, is when you cover a large area with a uniform amount of herbicide, fungicide, insecticide, or fertilizer.Table of Contents
- Step 1: Making a Property Map
- Step 2: Calculating How Much
- Step 3: Fill Your Spreader
- Step 4: What Setting to Use
- Step 5: How to Walk
Granular broadcast applications are typically done with a broadcast spreader. These spreaders consist of a hopper that holds the granular product, an adjustment knob to control the rate at which the product flows out of the hopper, and a spreading disk which flings the product outward at a consistent rate and pattern, guaranteeing uniform application.
Many product labels have a list of settings to use when applying granular products, but they are not always consistent or they may not have a listing for your particular spreader. However, if it doesn't, every granular product will have a "lbs per 1,000 sq ft" application rate that you can rely on.
Settings listed on Scotts bags
Settings listed on Scotts bags
Heavy-duty and built to last
Step 1: Making a Property Map
Since you can be sure that every product will have a "per 1,000 sq ft" rate listed, having a property map is essential. You can break your property up into zones to make this easier.
Once you’re made the property map, it should look something like this:
Step 2: Calculating How Much
Now that you know the area size that you want to cover, let's figure out how much total product to spread over that size of area.
Let’s follow an example. You can use our generic granular broadcast application calculator (also below) to calculate how much total product to put over an area. Also, we may have a CertainLabel™ Optimized Label Rate Calculator for your particular product so you can automatically populate the label rates.
Example: The back yard is 4,000 square feet. The label rate listed on the bag is 2 lbs of product per 1,000 square feet.
For your convenience, here is the granular broadcast calculator:
|# of Units||Cost Per Unit||Units Needed||Application Cost|
Did you get 8 lbs over 4000 square feet? If you did, you’re correct. In this example, you would evenly spread 8 lbs of product over the 4,000 square foot area.
Measuring Without a Shipping Scale
To be fair, you can get a shipping scale on Amazon for about $20 and it can be used for tons (or pounds) of other things. If you don’t have one, you’ll have to eyeball how much of the bag you’re using. In this case, 8 lbs out of a 40 lb bag is 20% aka 8 ÷ 40 = 0.2. You can split the bag from the bottom to the top of the granular product with a marker into 5 equal parts… or just eyeball it. That way, you know how much a 8 lb increment is.
Step 3: Fill Your Spreader
Now that you know the correct amount of product to use for the zone you're doing, put the measured out granular in the spreader. Whether you go by % of total bag or use the scale.
Step 4: What Setting to Use
If you don't know what setting to use, put your spreader on a low setting. If you have to go over the area multiple times, that's fine. If not enough granular is coming out, then increase the knob a bit more. So as long as you get an even coating over the area – that's the goal. You'll get a feel for what is the right setting is. Then, when you move on to other zones, you'll be zeroed in.
Step 5: How to Walk
There is no set pattern to follow, but I typically like to do the edges first, and then the inner areas, as such:
The dark green area is the area that the product covers. Try to let your product meet edge-to-edge and not overlap. The goal is an even coating over the whole area with little to no overlapping.