By Jeff Burbrink
Extension Educator, Purdue Extension Elkhart County
GOSHEN — A timely reminder from Keith Johnson, Purdue Extension’s forage specialist, reminded me of the importance of checking hay once it goes into the barn. As one of the largest hay producing counties in the state, we have seen more than our share of hay fires in Elkhart County over the years.
It is normal for hay to heat a bit as it cured in the barn. That’s part of the process of preserving the nutrients for later use. But, when the temperatures exceed 125 F, there is a real possibility that trouble is coming. It has been my observation that people keep a close eye on the hay for five days or so, and then assume it’s okay. In reality, fires often break out three to four weeks after being stacked.
What causes the fire? The root cause is excessive moisture. The target moisture for beginning to bale hay without a preservative is 20% for small rectangular bales, 18% for large round bales, and 17% for large rectangular bales. Moisture levels higher than this result in microorganisms creating mold, reduced protein in the hay, reduced forage quality and the possibility of spontaneous combustion.
The critical temperatures to watch for in stored hay are:
- 125 F or lower – No action needed
- 150 F — Entering the danger zone. Check temperature twice daily. If possible, disassemble stacked hay to allow more air to move around and cool heated bales.
- 160 F — The hay is reaching the danger zone. Check temperature every couple of hours. If possible, disassemble stacked hay to allow more air to move around and cool heated bales.
- 175 F — Hot spots or fire pockets are likely. Continue to check temperature frequently. If possible, stop all air movement around hay. Alert fire service of possible hay fire incident.
- 190 F — Fire is likely. Remove hot hay with fire service assistance. The fire service should be prepared for the hay to burst into flames as it contacts fresh air.
- 200 F or higher — Fire is imminent. Remove hot hay with fire service assistance. The fire service should be prepared for the hay to burst into flames as it contacts fresh air.
There are numerous places to purchase hay temperature probes. The key features are to make sure the probe is strong enough to penetrate through tightly packed bales to a length of around 6 feet. Another nice feature is the ability to insert a thermometer with the probe.