Learn to calibrate your fertilizer spreader

Why should you calibrate your fertilizer spreader?

When it’s time to fertilize your lawn, make sure you’re spreading the right amount of fertilizer. Too much and you may burn your lawn and waste valuable product. Too little and you’ll have wasted your efforts. Our simple tips will help you make the best of your gardening.

A properly calibrated fertilizer spreader:

  1. prevents product waste
  2. prevents excess product from getting into the watershed and creating pollution
  3. ensures a healthy lawn.

Did you know that excess fertilizer can also get into the watershed and create pollution? This leads to overgrowth of algae which is deadly to the delicate ecosystem of our waterways and their biology.

Before you apply a product, have your soil analyzed at the Clemson Extension office for your county. Knowing your lawn’s nutritional needs will help you purchase the right type of product with the right concentrations of nitrogen, phosphorus and potassium.

Begin by determining the total square footage lawn you need to treat.

Use this simple formula to determine the application rate of each fertilizer: 100 divided by the % nitrogen (nitrogen is the first component indicated by the three numbers on the fertilizer bag) = the amount of fertilizer to spread over 1,000 square feet.

Therefore, 100 ÷ 16 = 6.25 pounds of fertilizer per 1,000 square feet. 6.25/1000 x a 5,000 square foot lawn = 31.25 pounds of fertilizer.

A 40 pound bag of fertilizer will be all that you need to buy to fertilize a 5,000 square foot lawn.

Once you know the concentrations needed by your yard, you will need to calculate how much product your spreader flings.

Steps to calibrate your fertilizer spreader

You do this by using a particular number of square feet of lawn and test spreading your product.

Because granular products come in many different particle sizes and densities, the speed you walk, spreader condition, texture of ground and other factors, there is no way to determine a universal pounds per thousand spreader setting. One simple solution is to do a 50 foot by 20 foot test. The 50 by 20 rule will allow you to determine appropriate pounds per thousand rates for any product in any spreader. Weigh out and place enough material in the hopper to cover 1,000 sq. ft.

  •  Place the spreader setting on a low setting about 1/4 of the way open.
  • Apply the weighed material over a 50 x 20 ft. area (This is 1,000 sq. ft.).

If material is left over, you are under applying, and will need to increase the setting accordingly; before applying to the remainder of the lawn. If you come up short, you are over applying and you will need to decrease the setting; before applying to the remainder of the lawn.

Download our tip sheet to help you calibrate your spreader.

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