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Manure Spreader Calibration

Calibration Documents

Precision Manure Management

Manure Spreader Calibration for Nutrient Management Planning - NM1418

Manure Spreader Calibration Saves Money and Environment

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 testing, manure testing and spreader calibration saves money by knowing and controlling the amount of fertilizer applied to a field, which prevents over-fertilization. It protects the environment by minimizing nitrogen loss to ground water 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 sheet of landscaper's cloth of known dimensions can be almost as effective, he says. Follow these steps to use the plastic sheet calibration method:

  • Anchor the sheet with rocks or stakes.
  • Record tractor and spreader settings.
  • Apply the manure by driving over the sheet with the spreader.
  • Weigh the sheet in a plastic bucket (5-gallon bucket works well).

To determine the tons of fertilizer you would 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 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 would 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 have determined your current application rate and it is not the right one, adjust the spreader and measure the application rate again until you have achieved the desired rate.

To maintain the correct manure spreader calibration, be sure to record your tractor gear, engine's RPM and spreader settings as you calibrate, Augustin says.

Calibrating a Manure Spreader with the Sheet Method


Laying out a sheet for manure spreader calibration.

NDSU Agriculture Communication


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