Wind is a consideration - 60mph is common in winter, and we've had gusts to 130mph (!!). Can a tarp even be anchored to stay put in that kind of wind? How?
My main question, though, is footing - what should I use UNDER the pile of hay? Just the dirt/rocks? Concrete? Stall mats (maybe those ones with holes)? Pallets (um, no. Rabbits and mice)... the idea is to make sure that bottom layer is useable, but also to minimize homes for critters.
Suggestions of other ways to store hay outside the barn are welcome. I'm assuming regular bales at this point, as I'm unsure if I can find a supplier for horse-quality round bales, which would actually be my preference.