Spreader Calibration Getting the most out of your fertilizer applications

Spreaders… Are we paying attention to what is being used from an equipment perspective? Is calibration important enough to dedicate the time to discuss and do? When was the last time we calibrated our spreading equipment? The product might get blamed but, fertilizer performance may not be the issue…many of the perceived failures in the field are due to operator error, substandard equipment or equipment that just hasn’t been calibrated…

Broadcast Spreader Calibration 2 steps required for calibration 1. Determine the “effective swath width” of spreader…note this is not the same as spread width… –Granular product throws distance to either side of spreader…do this with “collection trays” –Distribution is not uniform –Even distribution achieved by overlapping 2. Measure amount of product being applied –“collection trays” –“catch pan” method –“weigh in-weigh out” method

Broadcast spreader calibration Calculate the area covered by the broadcast spreader that travels a specified distance Determine the throw distance and the “effective swath width” –Throw distance = 20 ft –Example “effective swath width” = 12 ft Measure and mark a distance to travel –83’4” x 12 ft = 1,000 ft 2

Broadcast spreader calibration Measure amount of product being applied –“collection tray” method Use the center collection tray from the previous effective swath width determination –“catch pan” method Attach a collection bag or container around the impeller to catch the product being applied –“weigh in-weigh out” method Weigh total product at start. “Apply” the product to a benign surface then re-weigh remainder of product Repeat the procedure 2-3 more times or until consistent results are obtained (10%)

Broadcast spreader calibration Set the hopper opening to a low to medium range setting Fill the hopper half full with a product Push the spreader at a comfortable walking speed…the same pace used to actually apply product…open the hopper…travel the marked off distance…close the hopper (the same concept applies to fairway and rough broadcast spreaders Beware…a 6’4” assistant will not walk as quickly as a 5’5” superintendent and tractor speed needs to be consistent for large areas…

Target is to apply 0.5 lb / 1000 ft 2 nitrogen using ammonium sulfate (21-0-0) –Ammonium sulfate has 21% N –0.5 lb N / 21 % = 2.38 lb ammonium sulfate Spreader must be calibrated to throw 2.38 lb ammonium sulfate / 1000 ft 2 Example calibration

Spreader Calibration-Keys Travel Speed (walking or riding) is often underestimated… +/- 0.5 mph = +/-16.7% change in rate or.167 lbs on a 1 lb application!!! +/- 1.0 mph = +/-33.3% change in rate or.333 lbs on a 1 lb application!!! Tire Pressure at 20lbs critical… Regular lubrication of the gear box and shut off valves…Do it regularly! Be aware that “effective swath width” and “actual spread width” are NOT one and the same…

Importance of Closing Spreader on ‘starts and stops’

Turns with open spreader

Spreading Techniques…Half Rate x Two Directions

Spreading Techniques…Full Rate x One Direction

Spreading Techniques…Half Rate x Half Width Recommended!!!

Reminders… Settings are “suggested” only and annual calibration is important as equipment wears or changes and personnel change. We calibrate our sprayers on a regular interval; why not our spreaders too? You spend wisely on fertilizer…why not make sure it gets where you want it to go as accurately as possible! Questions? Contact me at