Community
26 January, 2024
High hay moisture a fire risk
AGRICULTURE Victoria is reminding farmers to be mindful that even well-made hay can still be prone to spontaneous combustion.
The reminder comes after a haystack in Garvoc recently spontaneously combusted, resulting in smoke over the Princes Highway.
Agriculture Victoria program manager for dairy - north Brett Davidson said spontaneous combustion is usually caused by excess moisture at baling.
“Fires can also start due to heavy rainfall events which has soaked into stacks,” he said.
“Intense rainfall could compromise even well covered stacks, as water can pool at the base of a stack, seep into gaps or could be blown under covers.”
Mr Davidson said for those with moisture meters, ideally hay moisture levels should be in the ranges that decrease as the bales increase in size.
For small square bales, moisture content should range between 16 and 18 per cent.
For large round bales, the recommended moisture range decreases to between 14 and 16 per cent; large square bales, however, should have a moisture content of between 12 and 14 per cent.
Export hay should have a moisture level of less than 12 per cent to reduce the risk of combustion.
Mr Davidson said even at two to three per cent above the maximum recommended moisture contents, hay will start to lose dry matter and nutritive value due to plant respiration or mould growth, resulting in heating of the bale and/or stack.
“Even at 2 – 3 per cent above the maximum moisture contents, hay will start to lose dry matter (DM) and nutritive value due to plant respiration or mould growth, resulting in heating of the bale/stack,” he said.
“Higher moisture contents, well above the maximum (more than four per cent), could lead to more mould and heating, possibly resulting in spontaneous combustion.”
Mr Davidson said it’s vitally important to regularly monitor the stack from one week after rainfall for signs of heating.
Signs of heating could include:
dampness on the tops of bales;
steam rising from the stack;
moisture build-up on roofing iron or under tarps of outside stacks;
unusual odours, such as stacks smelling of pipe tobacco and caramel, or having a musty or burning scent;
sometimes the stack may slump in places; and
corrosion on underside of tin roofs.
Mr Davidson said much of the heating will occur in the stack centre which is difficult to pick up.
“To try and get an idea on how hot a stack has become, use a crowbar pushed into the stack as far as possible and after a couple of hours, remove the crowbar and feel how hot it is,” he said.
A rough guideline to check a haystacks temperature using a crowbar:
At less than 50 degrees, you can handle the bar without discomfort. Check temperature daily;
Between 50 and 60 degrees, you can handle the bar for a short time. Check temperature twice daily;
Between 60 and 70 degrees, you can touch bar only briefly. Check temperature every two hours. It is recommended to move hay from top layers to improve air flow.
Above 70 degrees, the bar is too hot to hold. Potential for fire - avoid walking on top of stack.
Mr Davidson said an alternative monitoring method can be achieved by using thermal couplings, which can be placed into various areas of the stack at stacking and monitored simply and regularly.