If you are serious about your hay you might want to consider building a hay barn. The smart kids at Texas A&M say a hay barn is the first AG building that will certainly pay for itself.
Hay bales are an investment worth protecting | AgriLife Today
INSIDE HAY STORAGE WOULD PAY FOR EAST TEXAS PRODUCERS | AgriLife Today
Definitely on the right track with stacking off the ground on tires and covering it but a Hay building would be a better investment.
>>"The same study showed that storing hay outside on pallets or tires brought the losses down to about 12 percent. Hay stored on pallets or tires and covered with a tarpaulin brought losses down to 7 percent. But hay stored on the ground (without pallets or tires) and covered, lost nearly 13 percent.
By far, the lowest losses occurred to hay stored inside barns or sheds — only about 3.5 percent. You say you don’t have enough barn space to store all your hay? Then building another barn, particularly a relatively inexpensive one such as a pole barn, might pay off, said Greg Clary, economist with Texas Cooperative Extension."<<