Rain or mold damage can easily drop the price of hay $50 per ton or more, but hay bale fires cost thousands of dollars in building, feed replacement and lost revenues.
Hay fires generally occur within six weeks after baling, but have been known to occur even after a year, according to a report by eHay Weekly. They begin through spontaneous combustion. Hay bale fires can occur not only in barns, but also in field stacks and during transport on trucks. As more growers have switched to big bales, the frequency of hay fires has also increased, the report said.
Stem moisture is crucial - Fires occur most often when stem and bale moisture is too high, and the bales haven't been adequately 'sweated' (when moisture and heat dispels from newly-baled hay) before movement and storage.
Research found the moisture content of the hay at the time of baling is the primary factor affecting the likelihood of a hay fire. However, even with favorable curing conditions fires can still occur. The larger the bale and the higher the density, the greater is the risk of a hay fire.
People are also reading…
The maximum recommended moisture content for safe baling is generally considered to be 18-20 percent for small two-tie bales, 16-18 percent for three-tie bales and 14-15 percent for large bales. However, these numbers should not be considered absolute, and depending upon compaction, aeration, and stacking, heating can occur at even lower moisture. Rain on recently baled hay that has not completed “the sweat” is also especially prone to spontaneous combustion. There can also be bales or portions of bales with higher moisture levels that may be sufficient to cause a fire as the wet spot becomes larger driving heat and moisture into the surrounding hay.
What can a grower do to prevent hay fires?
Experienced growers can tell a lot by visual appearance and feeling the hay; however, use of an electronic moisture meter as a backup, especially when conditions become more “marginal,” is recommended. Baler mounted moisture sensors are particularly useful for big bales.
Monitor at least the first 3 bales produced and then periodically throughout the baling period, especially when conditions change. A total of twelve readings from different ends of a large bale is recommended. Bales with readings much above 20 percent or averages over 14-16 percent should be stacked separately-away from structures or equipment. Stacking hay with an air gap between bales allows the moisture to dissipate more readily and can help avoid problems. Be certain all the bales fall at or below the acceptable range stated above for different bale sizes before storing hay in a barn.
Hay that becomes wet during storage can become a potential fire hazard, too. Hay barns should be weather tight and have adequate drainage to prevent hay damage during storms. Hay stored outside should be covered with plastic or some other waterproof material to prevent rain penetration. Protect bales from ground moisture by placing them on a bed of gravel, old tires, poles, or pallets.
Monitoring hay temperatures during storage
The temperature of hay that has been baled at a high moisture concentration should be checked twice a day for six weeks after baling. Hay temperature should stabilize six weeks after baling and monitoring can be discontinued.
Use a probe and thermometer to accurately determine the temperature inside a stack of hay. Fire is imminent if interior bale temperatures exceed 175 degrees. Other symptoms of hot hay or an internal fire include a slight caramel or strong burning odor, visible vapor or smoke, a strong musty smell, and/or hay that feels hot to the touch.
If any of these symptoms occur, call the fire department immediately. Let firefighters take control of the situation once they arrive. Do not move hay if signs of fire are present; doing so exposes the overheated or smoldering hay to oxygen and may cause the fire to burn uncontrollably.
Controlling hay fires
In the event of a hay fire, surveying the fire scene is the most important step to ensure everyone's safety. If flammable products (e.g. gasoline, fertilizers, and pesticides) are located nearby, leave the area immediately.
If there are no flammable products in the area and time permits, there are several steps you can take before the fire department arrives.
Hay stored outside
Use a disk to create a firebreak around the stacked hay. The firebreak should be approximately 15 feet wide. If water and a high-pressure hose are available, water the hay and the surrounding vegetation to keep the fire from spreading.
Hay stored inside a building
If the area is safe and time permits, evacuate any livestock from the building to a pasture a safe distance from the structure. Turn off the building's electricity to prevent an electrical fire. If water and a high-pressure hose are available, water the roofs of adjacent structures downwind of the fire.
Damaged hay
Hay damaged by heat, smoke, or water should be removed to a safe location. Use damaged hay as mulch for erosion control on slopes and in gullies. If you are uncertain whether heat has damaged hay too much for feeding, have a sample tested.
