Hay tarps can be a good alternative to barns or commodity sheds when storing hay, says Karla Hernandez, forages field specialist with South Dakota State University.

Solid structures protect hay from water and allow for acceptable moisture loss if stored well and ventilated. But they can be expensive to build and maintain.

Plastic hay tarps are cheap and keep water off bales. They also offer maximum flexibility. “The advantage of plastic traps is they allow more protection while minimizing field transportation,” she says. “It allows hay to be stored in the field or in the bale yard until is ready to use or to be sold.”

But there can be downsides to plastic tarps, including issues with trapped moisture as bales dry out. Also, exposure to ultra-violet light can significantly reduce tarp service life.

Breathable hay tarps are pricier than their traditional plastic counterparts – costing up to five times as much. They do, however, protect against rain and allow passage of air and vapor, which prevents mold growth. They’re also resistant to wind lifting, extremely tear-resistant, ultra-violet light stable and similar to the commercial product "Goretex" in function, she says. “People who work outdoors appreciate this material for its ability to keep their feet dry in a durable, lightweight fabric boot.”

No matter which storage option selected, producers should regularly inspect and repair the covered surfaces of hay to maintain feed quality. “In general, catching a damaged cover early can help minimize spoilage from excessive moisture,” says Hernandez. “An annual evaluation of covering and feeding practices can help a livestock producer extend their hay inventory and feed higher-quality forage all year long.”