By Chris Hicks, County Director – UT Extension Smith County
There are a lot of burning issues being talked about right now in our country. Many people have strong opinions on these political, social, financial, etc. matters. I’ll spare you my opinions on these and instead focus on a “burning issue” related to hay production.
At Extension meetings, we often stress the importance of putting up high quality hay by cutting hay early before it ripens. We also emphasize storing hay under cover (such as in a barn) so it doesn’t lose quality and dry matter. While I stand behind both of those recommendations, we also need to emphasize making sure hay is properly dried before it is baled and stored.
What sometimes happens is producers try to “beat the rain” and bale hay that isn’t quite cured well enough. Dry hay needs to be baled below 18% moisture, and while it may seem counterintuitive, having too much moisture in the hay can contribute to problems leading to spontaneous combustion.
Keep in mind that freshly cut forage is not dead. Respiration continues after cutting, and a small amount of heat is released. This heat leads to the growth of bacteria and other microorganisms, which create more heat. These microorganisms are no problem when the hay is harvested and cured to the proper moisture content before baling and storage; however, higher moisture levels lead to more thermophilic (heat loving) bacteria being present. This bacteria can heat bales to temperatures as high as 170 degrees Fahrenheit or more.
The simple, although not always easy to follow, recommendation is to make sure hay is below 18% moisture before baling. If you do harvest hay that was baled with some wet spots, monitor the temperature of the bales for a few weeks after baling. A 20 to 30 inch compost thermometer can be used to check the temperature inside a bale, and we also have a probe available for check-out at the UT Extension office.
Hay that has heated to 120 degrees Fahrenheit will suffer protein breakdown and reduced quality. At 140 degrees Fahrenheit, the sugars begin to caramelize which you may be able to smell. At temperatures between 150-180 degrees Fahrenheit, combustion risks are extremely high. Be careful about moving hay at extremely high temperatures, as exposing overheated hay to oxygen could create a raging fire. Call the fire department in this scenario.
Putting up hay that is too wet isn’t worth the risk of losing an entire crop—or worse yet, a hay barn. If you do wind up harvesting hay that is suspect, be sure to monitor the internal temperature of the bales for 3-4 weeks after harvest. For more information, contact UT Extension at 615-735-2900.
