The NSW Rural Fire Service (RFS) has issued the warning after five crop fires in the Orana district within a number of weeks.

Acting manager of the NSW RFS Orana team Bronwyn Waters said fires that start during harvesting operations could destroy homes, crops and livelihoods, however could be preventable.

"We've seen a few headers burnt to the ground recently, as well as the fire on Saturday there was 300 hectares worth of crop which went as well," she said.

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"So that's heartbreaking for farmers who have already dealt with tough times in the drought for the last couple of years, and then to lose [crops] as well."

The acting manager said a majority of recent crop fires had been started by machinery.

"A lot of harvesting machinery haven't been used for a couple of years due to the drought. So there's possible dry bearings, or hot items come into contact with the crops, and with a bit of wind, the crops just get away really quickly."

Officer Waters said it was a landholder's responsibility to limit the ignition and prevent the spread of fires from a property.

She said people should maintain their equipment, have firefighting equipment on standby and ensure there are breaks around crops to help reduce the spread of fire.

"Crews are volunteers, so sometimes it can take 20 minutes, half an hour or longer before they can get there, and a grass fire ... can travel several kilometres in that time, because the fuel is fine and quite readily available to ignite, especially with a strong wind behind it," Officer Waters said.

"So that's why I stress the importance for landowners to have their own firefighting equipment available ... even if they have a slip on unit on the back of their ute or trailer, to try and knock a fire down and contain it before it gets too big."

Landowners are also being urged to watch weather conditions, particularly when it's warm and windy.

"If it's quite warm and windy and the humidity is down that's obviously when a fire will spread a lot quicker and a lot harder to control," Officer Waters said.

"Put off harvesting if it is really windy or extra hot, until it cools down and the wind drops."

A Harvest Safety Alert may be issued for districts when necessary. Harvest Safety Alerts provide a signal to farmers that they should be taking extra precautions during harvesting operations to prevent the ignition and spread of fire due to the prevailing weather conditions.

Harvest Safety Alerts will be promoted via local radio and the NSW RFS Website.

If a Harvest Safety Alert is issued for your area landholders should:

In the event of a fire people should call triple zero (000).

More information on harvest fires visit www.rfs.nsw.gov.au