Fire and Emergency New Zealand has attended at least two fires in Canterbury in the past few weeks relating to baled hay and its storage.
Fenz group manager Al Hutt said land managers had started cuts of hay this spring-summer but rain, especially early on, had added pressure.
"[It] can put pressure on them to get the work done quickly and miss some crucial steps, which has created the perfect storm in terms of fire risk with hay bales," he said.
"Hay bales contain moisture and sometimes that means they can self-combust. Hay bale fires can burn through farmland or the sheds the hay is stored in.
"Then a fire that starts in a shed could spread to machinery stored there and to connecting buildings," Mr Hutt said.
Fenz said there were important steps for land managers to take when baling hay and storing it.
"It is important to provide air flow where possible.
"Allow the hay to breathe; check bales using a moisture meter or a simple steel rod — if the rod is too hot to hold, unstack the pile.
"If the rod is very warm, regularly monitor your stack, and keep bales clear of other flammable objects like implement sheds, hedges and trees.
"Rushing the job can easily cause costly and dangerous consequences," he said.
