Taking a few simple steps when harvesting and storing hay can go a long way in reducing the possibility of fires and associated costs.

For instance, Bob Schultheis, University of Missouri Extension natural resources engineer, explains hay fires usually occur within six weeks of baling. The most common cause is excessive moisture.

"You can reduce fire and mold risk by baling small square bales at 18-22% moisture content and large round bales at 14-18% moisture content,” says Schultheis. “Higher moisture levels increase microbial activity and also result in loss of dry matter and usable protein, which can reduce the feeding value of the hay by as much as one-third."

According to Schultheis, heating in hay bales will occur to some extent in all forages over 15% moisture, with a peak in temperature 3-7 days after baling. "It takes 15-60 days for the hay temperature to decline to non-damaging levels, depending on outdoor humidity, density of the bales and amount of rain the bales soak up,” he explains. “The longer it takes for the hay temperature to decline, the more damage is done to the hay."

New hay stacked in the field or placed in a barn should be checked at least twice a day for abnormal heating. Schultheis recommends using a garden-composting thermometer. If you’re storing hay inside, be sure the barn roof and plumbing do not leak and that surface water cannot run into the barn.

If the hay temperature reaches 130°F., move the hay to allow increased air circulation and cooling. If the temperature climbs above 150-175°, call the fire department and be prepared to inject water to cool hot spots before moving the hay.

"Don't open the barn door if the hay is smoking. The added oxygen can cause the hay to burst into flame," says Schultheis.
--From eHay Weekly (July 7) at Hay and Forage Grower.