Hay Baling with Moisture

It’s springtime in Central Texas and while you might still be trying to cut and/or bale those first hay cuttings of the year, you should consider the moisture content.  The moisture content during baling and storage can considerably effect to the nutritive value of the hay.  Hay baled with high moisture content levels can have negative impacts such as hay spoilage, barn fires, and decreased nutrition.

A natural event, commonly referred to as “heating,” occurs when growing forages are cut and continue to give off heat due to respiration.  Plant and mold respiration generates lots of heat; providing proper growing conditions for bacteria.  If wet hay is baled while it is too wet, microbe populations will flourish and intensify the heating process.  This results in hay that is lower in nutritive value and dry matter availability.

Allowing cut hay to dry (or cure) will slow down the respiration process.  Respiration slows down as moisture content decreases but will not completely stop until plant moisture reaches 20 percent or less.  Moisture levels above 20 percent allow the respiration process to continue and mold to develop, which then produces heat.

If the internal temperature of a bale of hay exceeds 130 degrees F, a chemical reaction occurs within the bales that release flammable gases that can ignite.  So when harvesting, the most effective way to reduce the potential of spontaneous combustion in hay bales is to make sure the cut has dried sufficiently prior to baling.  Consider the weather conditions because this greatly influences the rate at which hay dries.  Cut hay that has been rained on or is slightly wet should be mechanically teddered, or fluffed, to speed up the drying process.

Moisture levels for safe storage vary with the size and density of the bale and the type of hay. Hay in small square bales should be baled between 15 and 22 percent moisture to minimize leaf shattering, molding and heating.  Larger round bales or the large square bales are larger in size and weight.  So obviously these will retain core moisture, thus internal heat longer than the small square bales. These larger bales should not be baled with a moisture content level in excess of 18 percent.  If you are deciding to bale your large bales while the moisture content is in excess of 22 percent, you should not stack the bales for at least 30 days and consider this when feeding.

Large bales stored outside will suffer variable losses, depending upon the moisture of the hay at baling, the extent of exposure to precipitation, soil drainage characteristics where the bales are stored, the amount of space between the bales and the type of hay.  Properly-baled hay should be stored in well-drained areas, with a minimum of three feet between bale rows, away from trees or shade, and all facing the same direction as prevailing winds (ends facing north and south).   Check newly stacked hay for possible heating, especially for hay that has been rained on. It is not unusual for hay to heat to 100 degrees F within the first couple of weeks after it is baled.

For more information, please contact Chelsea Dorward at the Texas A&M AgriLife Extension Service – Bosque County Office at 254-435-2331

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