Don’t let your hay profits go up in smoke

Hay is a hot commodity, but don’t let it ignite.

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.

Tips to avoid hay fires include:

  • Consider seeding a grass mix with alfalfa as most grasses allow hay to dry more rapidly in the windrow and today’s improved grasses can still provide great feed quality and yield even for dairy farms.
  • Provide good weed control as certain weeds tend to dry slower in the windrow than alfalfa.
  • Know the proper moisture levels for safe baling of different bale packages and avoid the temptation to start baling too early in the day.
  • Use approved hay preservatives if bales must be made wetter than what is advised.
  • Properly adjust conditioning rollers on mowing implements to maximize drying without causing excess leaf loss.
  • Utilize moisture testing equipment, such as handheld hay probes or in-chamber testing units on newer balers, to support decisions on when hay is dry enough to bale, but with a new unit always check it against another moisture testing process or unit as these systems can be highly variable in their results.
  • Set aside any wet square bales in a separate location that will preferably be under cover and not in direct contact with the ground, but still allowing airflow around each bale, with non-combustible surroundings if possible.
  • Use a thermometer probe, or in an emergency a metal pipe with a thermometer lowered inside,  to check the interior temperature of a suspicious hay stack for two to three weeks after stacking; for temperatures 115 – 130 degrees F, monitor twice a day; 131 – 149 degrees F, check every few hours; 150 – 174 degrees F, have a good supply of water ready with extra help on hand and the fire department on standby and then pull out hot bales; 175 > degrees F, call the fire department, remove equipment and animals from the building, but do not pull out any bales until the fire department is on site (at this stage the introduction of oxygen into a hot spot in a stack is all that is needed for the hay to ignite and burn out of control within minutes).
  • Do not walk on top of a hot spot as burned out cavities can cause cave-ins, instead lay down a ladder and walk on it when probing a hot spot.

The recommended moistures to bale without preservatives are:

  • Small square bales (30 – 60 pound bales) - 14 - 18 percent moisture
  • Large square bales (600 – 1,200 pound bales) - 14 - 16  percent moisture
  • Large round bales (500 – 1,200 pound bales) - 15 - 19  percent moisture

Large square bales are more densely packed than other bale types and do not allow moisture and heat to escape as easily, thus the hay must be drier in those packages. In the Midwest it is difficult to dry hay to 16 percent moisture or less early in the afternoon so many apply a hay preservative like proprionic acid when large square baling begins in order to start baling earlier. Dry matter loss increases and forage quality decreases anytime we bale hay below 16 percent moisture, especially in round balers. Thus the optimum moisture ranges are the middle of the road between being too wet and too dry. In a good drying day a mowed crop of hay will pass through both ends of this range from 19 percent to 14 percent moisture in four hours so perfection in the making of hay bales is always a difficult target to constantly hit. But with knowledge and attention to detail farms can greatly reduce the risk of ever experiencing the loss of a hay fire.

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