The University of Georgia
College of Agricultural and Environmental Sciences
Cooperative Extension Service
Broadcast Dry Fertilizer
Calibration
Paul E. Sumner, Extension Engineer
It is essential for economical and efficient crop production that spreaders be calibrated so that exact amounts of fertilizers may be applied per acre. Plant nutrients need to be applied according to the individual crop requirements. Yields may be reduced with insufficient nutrients and excess nutrients can lead to accumulation in soils and water.
Materials needed for calibration of a spreader:
1. Collection pans the length that the spreader will cover. The sheet or tarp should be five to eight feet wide. Pans can be 2 feet square.
2. Graduated Cylinder (milliliters)
Calibration steps:
1. Distribute the collection pans across a smooth, flat area where fertilizer can be applied.
2. Drive the spreader across the collection pans at the speed to be used in the field. The spreader should be operating several yards before and after you reach the collection pans to ensure an even fertilizer flow. Record the speed, RPM and gear selection of the tractor.
3. Measure the material collected with the graduated cylinder in ml.
4. The above procedures should be repeated several times to get a reliable average weight.
5. The following equation is for calculating rate per acre using a graduated cylinder.
Substitute into the following equation.
Lbs/Acre = (1.5377 * ml * __ lbs/ft^3) / (Collection Area ft^2)
| Material | g/cc |
lbs/ft^3 |
| Ammonium nitrate (prilled) | 0.95 |
59.31 |
| Ammonium nitrate (granular) | 0.86 | 53.69 |
| Ammonium phosphate (11-48) | 0.86 | 53.69 |
| Ammonium Phosphate (16-20) | 0.85 | 53.07 |
| Ammonium Sulfate | 0.87 | 54.31 |
| Manure (poultry) | 0.66 | 41.20 |
| Mixed Fertilizer, granular | 0.92 | 57.44 |
| Mixed Fertilizer, N-K | 0.94 | 58.68 |
| Mixed Fertilizer, N-P-K | 0.97 | 60.56 |
| Mixed Fertilizer, P-K | 1.07 | 66.80 |
| Magnesium Sulfate, Epson salt | 0.81 | 50.57 |
| Urea, crystal | 0.57 | 35.59 |
| Urea, pellet | 0.66 | 41.20 |
| Urea-form | 0.45 | 28.09 |
The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service, the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.
An Equal Opportunity Employer/Affirmative Action Organization Committed to a Diverse Work Force
Issued in furtherance of Cooperative Extension work, Acts of May 18 and June 30, 1914, The University of Georgia College of Agricultural and Environmental Sciences and the U.S. Department of Agriculture cooperating.
Gale A. Buchanan, Dean and Director
Engineering 05/03/00