[masraum]

Originally Posted by flipper35

Wet hay will start to compost and get hot enough to spontaneously combust.

Yep, I didn't expect that.

Baled stored hay can get wet during spring as a result of melting snow or rainwater. Stored forages with high sugar content (i.e. hay baled at high quality-early vegetative stage) usually have higher nutritive value. At the same time, they could be at greater risk of achieving higher temperatures upon exposure to air particularly when they are not stored at the right moisture. As spring progresses, higher ambient temperatures together with air infiltration favor the growth of bacteria and molds that further build-up heat. If air continues to penetrate the mass, oxidation by these microorganisms may continue until spontaneous combustion occurs. For this reason, bales stored with excessive moisture are also more susceptible to heating as they constitute and ideal substrate for microorganisms.