Manure Manager

Manure spreader calibration can save money

April 28, 2008  by NDSU Extension

Apr. 28, 2008, Carrington, ND – Manure spreader calibration is an important aspect of nutrient management.

Apr. 28, 2008, Carrington, ND – Manure spreader calibration is an important aspect of nutrient management.

“With the increasing costs of fertilizer, it can save producers money and prevent pollution,” says Chris Augustin, nutrient management specialist at North Dakota State University’s Carrington Research Extension Center .

Soil and manure testing and spreader calibration save money by letting producers know and control the amount of fertilizer applied to a field, which prevents over-fertilization. Testing and calibration protect the environment by minimizing the loss of nitrogen to groundwater and phosphorous to surface water.

Spreader calibration can be completed as easily as weighing the loaded spreader before application, determining the spread area (acres) and weighing the empty spreader, according to Augustin.


If a truck scale is unavailable, then spreading the manure on a plastic sheet of known dimensions can be almost as effective, he says. Follow these steps to use the plastic sheet calibration method:

Anchor the sheet with rock or stakes.
Apply the manure by driving over the sheet with the spreader.
Weigh the sheet and manure in a plastic bucket (a 5-gallon pail will work well).

To determine the tons of fertilizer you’d be applying per acre at your current application rate, multiply the pounds of manure on the sheet by 21.8, then divide by the square feet of the sheet.

Augustin suggests using a 21.8-square-foot sheet to simplify your calculations. A sheet that is 3 feet by 7 feet 4 inches or 4 feet by 5 feet 6 inches is close to 21.8 square feet. Then all you need to do is weigh the sheet after applying the manure because the weight in pounds is equal to tons applied per acre with this size of sheet. Thus, if the manure on the sheet weighs 30 pounds, you’d be applying 30 tons of fertilizer at your current application rate.

He also recommends repeating the sheet method three or more times and averaging the results to account for variability.

Once you’ve determined your current application rate, if it’s not the right one, adjust the spreader and measure the application rate again until you achieve the desired rate.

To maintain the correct manure spreader calibration, be sure to record the tractor gear, engine’s revolutions per minute and spreader settings as you calibrate, Augustin says.

For more information on manure and determining the correct application rates for your crops, check out NDSU’s fertilization and manure publications at: and .


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