How much fertilizer should you use on your lawn? Too much can result in turf burn, wasted product and money, and potential environmental concerns. Too little will result in a low-density lawn that will not be attractive or competitive against weed invasions. To insure that you apply the proper amount of fertilizer to your lawn, you must calibrate your fertilizer spreader. You should calibrate your spreader each time you use a new (different) fertilizer because not all fertilizers have the same particle size or density. The information on the fertilizer bag is a good starting point for the calibration process but remember that spreaders can differ significantly. Calibrating your spreader will take a little bit of work, but the series of fairly simple steps below will help you complete the task.