impact, that sort of feeding works only if the grain is well-scattered. If you use a clock-feeder which spins the grain out in a big circle, set the feeder pretty much inside a brushy spot and under a tree, if possible. Out in the open is a Bad Thing.
(Foxes like corn. They'll eat the cracked corn from beneath my bird feeder, and then later come up on my porch and leave evidence that foxes don't digest corn.