When environmental temperatures reach the highs they have for much of this summer, there are risks of spontaneous combustion of hay supplies, and of manure piles, especially when moisture levels are elevated. Several years ago, horse manure pile on a farm in New York State burst into flames resulting in smoke and odors impacting nearby neighbors (https://www.wired.com/2016/08/manure-fire-new-york/).
The fire started in a large manure pile. With all of the hot weather in recent days, the interior temperature may have reached several hundred degrees. And if too wet, it is likely that bacterial activity caused the elevation of temperatures in the core of the pile and resulted in spontaneous combustion of the pile.
Normal composting will cause a manure pile to heat. The excess heat will destroy microbes that are present in the pile and ultimately the temperature will drop. But if the pile temperature gets too high – probably 180º Fahrenheit or higher, and is exacerbated by elevated environmental temperatures, there is a risk of spontaneous combustion.
When excess heat is expected in the manure pile, it should be turned and distributed into several smaller piles. The increased surface from this approach will allow greater heat loss from the pile. This may help to prevent combustion.
A similar fire in stored poultry litter occurred in Arkansas in 2017 (https://www.chicagotribune.com/nation-world/ct-manure-pile-fires-20170114-story.html). According to Dr. Karl VanDevender (as quoted in the article linked above), an extension engineer for the University of Arkansas System, normal composting occurs at 130 to 145 degrees. This is sufficient to kill pathogens, parasites, and weed seeds. However, temperatures in the 170 degree or greater range, raise the risk of fire. These types of fires in stored poultry litter are not uncommon. Whenever smoke is visible, extreme precautions must be in place.
The bottom line is that manure piles should be turned regularly when composting, manure should be disposed of properly, and manure piles should always be monitored to prevent overheating.
Overheating can also occur when hay is harvested and put up too wet. Small rectangular bales should have no more than 20% moisture and round bales should have no more that 18% moisture. This excess moisture can result in overheating of a hay stack, and combustion can result. Hay storage and barn fires still occur from time to time.
Some precautions can be taken if hay is suspected of being too wet. First, store hay out of doors, if possible for several weeks until heating risk is passed. Air movement is important so hay should be stacked loosely. Allow space between bales to allow good air circulation and heat dissipation. The more surface area between hay bales will speed drying by increasing the hay surface exposed to air. There are several preservatives on the market that can be sprayed on hay during the baling process. These will prevent fungal and bacterial growth, reduce heating, and improve storage value.
Steps to Consider When Using Rained-On Hay
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Remember to always check moisture levels before baling. For accurate results use a microwave, Koster or electronic, moisture tester.
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Recognize that rained-on hay will be more prone to molding due to the increased exposure to soil-borne fungi.
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Analyze hay for nutrient content and Relative Feed Value.
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Consult with your nutritionist and consider using this lower quality hay for livestock with low nutritional demands.
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Formulate diets based on Relative Feed Value, the nutrient content of the feed and the animal’s needs.
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Remember that rained-on hay may have toxins associated with spoilage. Never feed spoiled feed to a horse. This might be OK for feeding some classes of animals, but should be avoided when feeding animals that are reproducing or lactating.
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When fed it should be only a portion of a balanced diet.
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Consider utilizing a hay preservative when hay is too high in moisture or rained on.
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Pioneer Brand Products: Nutritional Insights https://www.pioneer.com/CMRoot/Pioneer/US/products/alfalfa/pdfs/alfalfa_harvest_rainedonhay.pdf
Heating of higher moisture hay can lead to loss off feed quality and in extreme circumstances, loss of hay by fires. Poor management of manure piles can also lead to overheating and combustion. Managing the processes (microbes) occurring in hay stacks and in manure piles can help to prevent fires such as the one described above.
Taken from the New Jersey Farmer, September 15, 2020
