Hay Storage Safety

By Lynda M. Vanden Elzen
(Published originally in the Langley Times, June 29 2016, page 27)

Pages-from-i20160629054201873Did you know that hay can spontaneously combust, causing barn fires and loss of life, equipment, and structures? Hay is cut in the field, and then baled and stored. If the plants do not dry sufficiently before baling, the hay bales will go through a curing process in storage, sometimes called a “sweat.” This curing process produces heat, which can build up to over 200°F and ignite! When hay is baled before it is dried sufficiently, heat can build as a result of live plant tissue respiration coupled with bacteria and mold growth. Ambient moisture in the air surrounding stored hay can also be a factor.

In the Lower Mainland of BC, our wet climate can produce a perfect storm leading to hay combustion due to the high ambient moisture in our air, and the difficulty our local farmers can experience when trying to dry their hay sufficiently before baling. Hay should test at 10-12% moisture or less in order to avoid risk of heating. In dryer climates, hay can be baled and stored safely with higher moisture levels of up to 15%. Unfortunately, in the lower mainland and other areas with excessive ambient moisture in the air, hay baled and/or stored at higher moisture levels cannot cure properly, because the air is already saturated, leaving nowhere for excess moisture in the hay to go. Very high ambient moisture in the air can even increase moisture inside the bales!

Warning signs can include steam rising from your hay which may condense on the roof and barn eves. Molds can begin to grow on those surfaces, and there may be a tobacco-like odour around the hay bales. If these signs occur, it is advisable to remove livestock and equipment from the vicinity and call the fire department for assistance. Use extreme caution when moving hay from a stack that is heating, as this could introduce oxygen into the stack and cause the bales to ignite! In addition to the risk of combustion, hay that is baled with too much moisture will lose nutritional value during the curing process. Agriculture Victoria (AUS) provides the following guideline for protein loss during curing of round bales, as an example:

Yield loss of round bale hay is that 1% of original yield will be lost for each 1% moisture that is lost as stored hay reaches its equilibrium storage moisture. For example, when hay is baled at 22% moisture which then dries to 14% moisture, dry matter loss will be approximately 8%.”

In order to avoid possible heating and combustion of stored hay, it is advisable to purchase tested hay with moisture levels of less than 10-12% and to avoid stacking hay in your barn that was baled less than 3 weeks prior.



“Haystack fires (spontaneous combustion) – Agriculture Victoria (AUS) (http://agriculture.vic.gov.au/agriculture/dairy/pastures-management/haystack-fires-spontaneous-combustion)

“Causes and Prevention of Spontaneous Combustion of Hay” – Lester R. Vough, Forage Crops Extension Specialist, University of Maryland (http://www.equineguelph.ca/pdf/facts/HAYCOMBUSTION.PDF)

“Spontaneous Combustion and Hay Fires” – Ontario Ministry of Agriculture, Food and Rural Affairs (http://www.omafra.gov.on.ca/english/livestock/dairy/facts/hayfires.htm)

“Spontaneous Combustion of Hay” – Steve Fransen and Ned Zaugg, Washington State University Extension (http://ext.wsu.edu/hay-combustion.html)

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