About 75 tonnes of hay was destroyed at the Yambinya Feedlot near Burraboi on Tuesday.
Rural Fire Service firefighters were called to the property about 12.30pm on September 8, and worked for the next four hours to bring the blaze under control and extinguish the flames.
None of the hay housed in the area where the fire started could be saved.
Bales not burned were either smoke or water damaged.
Spontaneous combustion is the suspected cause of the blaze.
Farmers are encouraged to check their hay stacks on a regular basis, and always ensure any valuable stock and machinery is stored separately.
NSW RFS Inspector Doug Adamson said landholders should also now be implementing their fire protection strategy.
‘‘This includes landholders placing firebreaks around valuable assets on their property and ensuring firefighting equipment is in good working order,’’ he said.
‘‘Loose fuels such as dry grass, fallen leaves and dead branches should be cleared in a wide area around all buildings and fences.
‘‘An effective fuel break can be achieved by grazing, slashing or mowing and by using summer fodder crops, herbicides or burning off.’’
For more tips and information on required permits, including the new online notification tool, go to www.rfs.nsw.gov.au/notify.