7.1 Calibrating Solid and Slurry Spreaders

Spreaders discharge at varying rates depending on ground and PTO speeds, equipment settings, and manure moisture content.

You will need the following information:

Load Weight

To determine load weight of solid manure spreaders:

Load and weigh the contents of the spreader, or an alternative method is to weigh a 5 gallon bucket of manure and take the weight x 1.5 x length x width x height / 2000 to estimate tons per load.

To determine load weight of liquid/slurry spreaders:

Determine the volume of material in gallons from manufacturer specifications,
or by taking the length x width x height of the spreader x 7.5.

For the volume in cylindrical tanks multiply length x diameter x diameter x 0.8 x 7.5.

Distance traveled to spread one load (feet)

Distance can be measure or estimated based on known field length or by counting fence posts along the length of the spread and multiplying by the average distance between posts.

Width of spread

Estimate the width of spread in feet, allowing a 10-20% pass overlap to ensure uniform coverage.

Use the following Worksheet (Calibrating Manure Spreaders) which determines your application rate of manure.


(*Note- Excel spreadsheets are programed to do calculations for you. On some computers you can do calculations directly on your computer. On others you must save Excel files to your computer or disk before using the spreadsheets. )

Direction for Calibrating Manure Spreaders Worksheet:

1. Load Weight

Enter load weight (tons) or volume (gallons)

2. Distance traveled (feet)

Enter distance traveled to spread one load in feet

3. Width of spread (feet)

Enter width of spread in feet allowing 10-20%overlap for uniform coverage

4. Area of spread (square feet)

The Excel spreadsheet will multiply line 2 by line 3.

5. Acres covered

The Excel spreadsheet will divide line 4 by line 43,560

6. Application rate (tons / acre or gal / acre)

The Excel spreadsheet will divide line 1 by line 5 to give you the recommended application rate.

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