One advantage to storing hay bales outside is that there is less risk of the hay bales catching fire. Hay lofts or barns can sometimes trap such high levels of heat that the hay in the middle of the pile spontaneously combusts, according to the University of Maryland. The goal of storing square bales of hay outside is to make sure they stay dry. Wet hay becomes mouldy hay, which is too spoiled to feed to livestock even though the animals may eat it.
Select a dry area of ground to store the square hay bales. Select an area away from trees or buildings, just in case the hay catches fire. Also, condensation from the walls or rain dripping off of the roof may cause the hay to get wet. If the area is muddy or has some moist grass, take some straw or a bucket of sand and place a thin layer down to help dry the ground out.
Lay down wooden pallets or large truck tires over the dry ground to make a base for the hay. This keeps the hay off of the ground, which will get wet again over time.
Pile the square hay bales on the tires or pallets. Make the piles as tall as yourself or smaller because you may need to get on top of the pile. Stack the bottom layer facing one direction and the next layer facing another. This will keep the hay pile from toppling over.
Place one tarpaulin over the hay pile and tie securely to the wooden pallets or tires with rope or twine. Repeat with the second tarpaulin. The second tarpaulin helps to repel condensation that occurs on the inside of the first tarpaulin.
The University of Minnesota recommends that the best time to store hay outside is during autumn, especially if the hay is to be used during the winter. Hay loses its nutritional value between 12 and 18 months, so be sure to have it used by then.
Don’t use thin, flimsy tarpaulins just to save money. Wind and rain easily damage them, making them useless for keeping hay dry. Never feed mouldy or foul-smelling hay to horses or other animals. Never leave poison out to kill any rodents that may be attracted to the hay. Not only could this kill other farm animals like dogs and cats, but the poison may get into the hay.