Hay prices have risen this year across the Midwest as total forage acres are down and weather factors have diminished first cutting yields in many locations. If your supply is already short, this valuable commodity to fire can make matters worse.
Each year there are hay fires in the farming community and this year has already proven to be no exception. It is one thing to lose round bales stacked outside, but it is even more catastrophic when fire destroys a farm building, animals or even threatens human life. Hay fires have many causes: a discarded cigarette, a lightning strike, or an electrical wire short but most commonly it is the result of bailed hay when it’s too wet.
The popularity of the round bale over the past thirty years has actually decreased the frequency of hay fires because of the ability to leave this bale package outside. The cylindrical shape of round bales reduces their rate of decomposition. More rainfall runs off a round bale versus a square bale and there is less of the bale surface in contact with the ground, which draws moisture into the bales and leads to rot. Some round bales never see the inside of a barn, but even those that do usually stay outside for three days or longer to go through a “sweat” before being moved inside, which reduces the risk of fire.
This sweating process is the normal respiration of the cut plants that are still giving off some moisture, carbon dioxide and heat from the plant cells. This process can continue for two days or more after mowing. In hay that is baled too wet and stacked on top of each other in a building, this moisture and heat cannot escape from the interior of the stack. Square bales, both small and large, make the matter worse. They cannot be left outside to sweat because they will draw moisture from the ground, plus their square shape allows them to be stacked tightly together in a building, reducing air circulation. Even chopped piles of dry hay or straw can heat and combust if the material is put in wet or becomes wet, because piles tend to seal in the heat and moisture as well.
This heating of the wet forage can lead to bacteria growth in the hay over the next one to two weeks. At the very least this can lead to moldy hay, with dusty bacteria spores that will have a slightly lower feed quality, an off color and possibly cause health problems in the animals that consume the hay. In the worst case, there may be too much moisture in the hay to dissipate and heat loving bacteria will grow, creating even more heat and increasing the temperature to a point where combustion is possible.