NSW Farmers' Association Business Economics and Trade Committee chair, Susan McLeish, said insurance guidelines for hay have been reviewed by insurance companies, with exclusion periods and rules changing.

"There were widespread haystack fires in NSW last year, particularly in the Riverina District where some 400 haystacks were destroyed," Mrs McLeish said.

"As a result, insurance companies have revised their rules regarding haystack insurance, which is something that all members, and farmers generally, need to be aware of.

"In some cases, farm machinery is no longer covered by insurance if it is stored in a shed with hay, and open stacks can only be covered for $50,000 each."

According to Mrs McLeish, as well as ensuring the right level of insurance protection, farmers also need to take preventative steps to guard against haystack fires.

"Hay stacks can generate enough heat to self combust if they are wet or not cured properly," Mrs McLeish said.

"Hay must be allowed to dry adequately before bailing, stacking and storing.

"Once cured, bales should be stacked to allow for good airflow, and farmers should check hay in sheds and stacks regularly.

"To check the temperature of bales, carefully break open a bale or ram a crowbar or metal rod into the stacks.

"If the rod comes out hot, pull the stack apart as soon as possible.

"Machinery should also be stored separately to reduce the risk of hay fires."