Granular applicators can be calibrated in turf or other areas off of the application site. You can also use plain fertilizers of the same type that you'll use in fertilizer combination products. For manually operated spreaders, the person who does the actual application should be the one who calibrates the equipment.
Follow these simple steps:
1. Mark out a test strip of 440 square feet (approximately 1/100th of an acre).
2. Weigh your granular product before and after you apply.
3. Subtract the difference to get the amount applied, then multiply by 100 to get the amount you need per acre.
4. Adjust your equipment and repeat the test until you have the correct setting for the required amount per acre.
Different products may have granules of different sizes and densities. Also, they may change the size of its granules from one year to the next. So you should repeat your calibration procedure each time you apply a different granular product. Contact us or spreader manufacturer for details.