Storing Hay Safely

Storing hay before it has dried thoroughly is a risky practice because of the danger of spontaneous combustion.

For stacking square bales, the moisture content should be no more than about 18 to 20%, and large round bales are safe to stack when the moisture level reaches about 16 to 18%. Damp hay gives off heat as it cures, sometimes reaching a point at which it can ignite.

To determine the temperature deep within a stack of hay, tie a string to a thermometer and lower it into the stored hay through a piece of PVC pipe pushed or driven into the center of the stack. Wait at least ten minutes and then determine the temperature.

Readings above 150 degrees indicate the hay may be getting dangerously hot, while a temperature of 175 degrees is a sign that the stack needs to be dismantled immediately. In this case, call the fire department and get help; don’t stay around the stack by yourself.

Suspect hay should be monitored for about six weeks after stacking, although hay that has gotten wet can heat up at any time. Avoid problems by allowing hay to dry properly before baling, stacking loosely, and having plenty of ventilation around and between bales.