beercrofter wrote:

This is how to calibrate your spreader from Vaginal Cooperative
extension service.
http://pubs.ext.vt.edu/430/430-017/430-017.html

Good for a laugh! Admits that a spreader cannot actually be
calibrated, only in theory. And they are incorrect about a broadcast
spreader pattern, it is not circular, it throws 1/4 circle to one
side, very easy not to fertilize paved areas, simply walk in the
correct direction... of course the morons who mow so the discharge
chute is aimed at the paved areas won't do any better with broadcast
spreaders.