A fertilizer is most effective when properly applied. Take the time to calibrate your spreader for every application to ensure that the effort put into researching and selecting the proper fertilizer for your turf translates into a job well done. Below are descriptions of the three, basic pieces of information necessary to calibrate a spreader: Rate, Speed and Width.

RATE
The amount of product applied by a spreader to an area will vary from the calculated amount if the spread pattern is overlapping (recommended) and also if the fertilizer is being applied in two directions. The amount of product coming out of the spreader would be ½ of the calculated rate for wheel-to-wheel overlap and ¼ if also applied in two directions.

SPEED
Many factors affect the ground speed while spreading.  When a person is calibrating a pedestrian spreader, they should walk at a steady pace that can be maintained throughout the entire spreading job.  Determining the speed of vehicle and tractor mounted spreaders takes more of the terrain and obstacles into account where the application is being made to ensure that the job can be performed safely.  Ideally, application ground speed would be slow enough to handle turns and slopes without incident, but be fast enough to finish the job in a timely manner.

EFFECTIVE WIDTH
The distribution pattern of spreaders can vary greatly from one spreader to the next.  It is necessary to determine the pattern and effective width of each granular material that is spread to ensure uniformity and proper application rate.  To do this, place identical catch pans in a row and spread over them in one direction, multiple times if on a surface other than turf, and then measure the amount in each pan.  Find the pans on the left and right sides of the path of travel that contain ½ the amount of fertilizer as the center pan; the distance between these outer pans is the effective width.  If the distance from the center pan to the edge of the effective width is greater on one side than the other, make adjustments to correct the bias, where possible.