Robert Seay warns that certain weather conditions can increase the chance for a fire to break out in hay bales and spread to the facility where it’s being stored.

Seay, Benton County agent with the University of Arkansas Cooperative Extension Service, said when hay is baled at moisture levels above 20 percent, heat can build in a bale, similar to heat generated in a compost pile.

“Damp bales slowly build heat, and the more elevated the internal temperature becomes, the greater the risk of internal combustion,” he said.

“The problem sneaks up on us because this internal bale temperature may not peak until two weeks or more after harvest,” he said.

A number of factors are involved in hay fires such as bale moisture, bale type, bale density and how tightly bales are placed in storage. A leaky roof in the barn where hay is stored could even play a part, Seay said.

The moisture meter and temperature probe are increasingly becoming more important in hay harvest management.

“The initial costs of a moisture meter and temperature probe may be questionable to some, but at current hay values, saving even a few bales, not to mention a barn, will easily offset the expense,” he said.

To reach comfortable storage conditions, bales have to “breathe” to allow moisture to evaporate. Physical constraints placed on and around a bale can slow, or even prevent, this necessary moisture loss. In that case, through microbial action similar to that occurring in a compost pile, heat will build, and a chain reaction begins, Seay said.

“Frequent bale checks with a temperature probe will keep you aware of internal bale conditions and might help you sleep better at night,” he said.