There are several benefits to choosing a dop-spreader. They are accurate and easy to use. Visual wheel tracks from the spreader make it easy to see where you last applied product. Product placement is precise since product drops down between the wheels and doesn’t fall or get thrown onto nearby sidewalks or driveways. And bonus they are great for smaller areas like strips of lawns or smaller lawns. 


It doesn’t matter which method you choose as long as your spreader is calibrated.

The Multiple Pass Method

  1. Measure the length and width and calculate the total square footage of the area to be treated.
  2. Calculate the total area occupied by the house, sidewalks, driveway, plantings, etc., and subtract from the total area determined in the first step.
  3. Read the label to determine how many square feet one bag of product will cover.
  4. Divide the number in Step 2 by the number in Step 3 to determine how many bags would be needed to treat the entire area.
  5. Set the gate lower than the 5 ¾ recommended setting given by the product label or the owner’s manual for the spreader.
  6. Place about a half of bag of product into the hopper.
  7. Push the drop spreader back and forth across the lawn until the product is gone. Fill the hopper with another half bag and repeat the treatment in a different direction (at right angles to the first application). Continue until 1 ¼ bags are completely used. Make sure that the wheel tracks of each pass slightly overlap the tracks from the previous pass.


The Single Pass Method

  1. Set the gate openings on your spreader using the product label directions; or set them so that they are slightly larger than the granules. Read the label recommended rate of application.
  2. Measure the width of the bottom of the hopper between the wheels.
  3. Convert the inches in Step 2 to feet by dividing by 12.
  4. Measure and mark a convenient distance on clean pavement such as a driveway; fifty feet is suggested. Ten passes back and forth along this distance will result in the release of enough product, to calibrate the equipment accurately.
  5. Calculate the area covered by multiplying the length of the hopper (Step 3) times the length of the area (Step 4).
  6. Weigh the amount of product that you use to fill the hopper. Turn the spreader on and push it over the test strip ten times, using a consistent walking speed. Be sure to turn the spreader off, immediately, when you reach the end of the test strip so the remaining product in the hopper is not lost.
  7. Weigh the amount of product that is left in the hopper.
  8. Compute the amount of product that was used to cover the test area by subtracting the leftover amount (Step 7) from the amount put into the hopper (Step 6). The result represents the amount of product applied to the 1,000 -square-foot test area.
  9. If the amount of the product used (Step 8) is within 10 percent (high or low) of the label-recommended rate (Step 1), the spreader is calibrated correctly. If the amount of product is not between 90 and 110 percent of the labeled rate, (that is, if it is not within ±10 percent), reset the gate openings and repeat the process.


The Swath Width and Distribution Pattern

For a drop spreader, the swath width is the measurement of the bottom of the hopper.  The pattern should be uniform across the swath. Using the opening setting for your spreader from the product label instructions, make a short test run on a clean paved surface where you will be able to see the distribution pattern. If it is not even, you may need to clean the openings in the bottom of the hopper or correct the agitator operation. Remove granules from the paved surface. Choose from three ways to measure using the Swath method.


  1. Catch Pan

Attach a catch pan to the bottom of the hopper.  It should be wide enough to capture all the granules and attached in a way that does not interfere with the shut-off bar or rate-control linkage.


Step 1 — Measure a straight test area that will give the equivalent of 100 square feet. For example, a drop spreader with a 3-foot swath width should cover an area 33 feet long (100 / 3 = 33).  A spreader with a 2-foot swath width should cover a 50-foot area (100 / 2 = 50).

Step 2 — Fill the hopper half full with product and select a gate setting based on the product label or spreader manual.

Step 3 — Push the spreader over the test area. Begin walking at the desired speed before you cross the starting line.  Turn on the flow of material as you cross the starting line. Turn it off when you cross the finish line.  Weigh the amount of material captured in the pan. Convert ounces or grams to pounds.

Step 4 — Determine spreader application rate in pounds/1,000 square feet, by multiplying the weight by 10.

Step 5 — Compare the spreader application rate to the product label rate. If the spreader rate is not within 10 percent of the label rate, adjust the gate opening and repeat Steps 3 and 4 until it is. Note that even small changes in the settings can result in large changes in the flow of material.


  1. Sweep and Weigh

Instead of catching the material during application to the test area, you can lay out a course on a concrete surface or plastic sheet. Sweep up and weigh the material.


  1. Weigh Before and After

Place a known weight of granules in the hopper, conduct a calibration run over the test area, and reweigh the granules remaining in the spreader.  The difference is the amount applied.


If you would like Organic Turf Trade to calibrate your spreader just let us know. We are happy to help. or 856.478.6704.