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Don't Over Apply Fertilizer - Calibrate Your Spreader

Over or misapplication of soil amendments like fertilizer may be a source of pollution and health concerns.  Nationwide more fertilizer is applied to an average acre of lawn than an acre of agricultural land.  After you have received your soil test results and the corresponding fertilizer recommendations for the grass variety being grown and determined the proper timing of application it is important to calibrate your spreader.  Calibrating your spreader will help ensure that the fertilizer is applied at the proper rate.

How to Calibrate a Spreader

In some cases the recommended spreader settings for your spreader may be listed on the fertilizer bag or at the company web site.   If it is not listed you will have to calibrate your spreader for the fertilizer being used.  Here are some steps to help you with the calibration. 

1. Walking at the normal speed you push the spreader, spread a small amount of fertilizer across a surface like a driveway where you can see the distribution pattern.  Measure the width the fertilizer is spread.

2. Mark the width and length for 1000 sq. ft., on your lawn.  For example, if your spreader distributed the fertilizer a 10 ft., width, mark out 10 ft. by 100 ft. on your lawn for 1000 sq., ft. 

3. Calibrate the spreader by weighing out a quantity of fertilizer equal to one-half the amount to be applied over a 1000 sq., ft.  area of lawn.  This is accomplished by first weighing yourself on a bathroom scale while holding a clean bucket and record the weight.  Then continue the procedure adjusting the amount of fertilizer in the bucket until the difference between your weight and the weight of the bucket plus the fertilizer minus your weight plus the empty bucket equals one-half the weight of fertilizer to be applied on 1000 sq., ft.  Note the calibration is for one-half the amount so that one-half of the fertilizer can be spread in one direction and then the remaining half in another direction to ensure even fertilizer distribution.  Once the correct quantity of fertilizer is determined, with a marker, mark the level of the fertilizer on the side of the bucket.

4. Set the initial spreader setting using your best estimate, erring on the side of being conservative.

5. Load the clean spreader hopper with the fertilizer measured in step 3.

6. Spread the measured quantity of fertilizer across the 1000 sq. ft. area staked out on the lawn in step 2.

7. If a portion of the measured quantity of fertilizer remains after covering the 1000 sq. ft., or runs out before the area is covered make the necessary adjustments to the spreader setting.  Reload the hopper with the desired amount of fertilizer, this time using the mark on the bucket instead of the scale to measure the correct quantity of fertilizer.  Repeat as necessary until the setting applies the desired amount of fertilizer.

8. If it takes more than two applications to complete the calibration it is recommended that a different 1000 sq. ft. area is staked out to prevent over application of fertilizer in that area.

9. Once the calibration and fertilizer application is completed, sweep or blow any fertilizer from impervious surfaces back onto the lawn to help prevent any fertilizer from leaving the site as pollution.  

Choose earth friendly practices.  Choose organic lawn care.


Earth Friendly Land Care, Inc. (March 2013)

​Earth Friendly Land Care, Inc. - Organic Lawn Care  

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