Tinderbox conditions during harvesting caused a spark to set field alight off Mill Lane in Earls Barton, with six crews on the scene at the height of the blaze.
In an attempt to stop the flames ripping through the whole crop on Saturday (July 23), a plough was used to create a firebreak of freshly turned soil.
Arriving just after 7pm, crews found the field well alight and called for back up - in totalsix fire appliances attended the incident along with a water bowser.
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A spokesman for Northants Fire and Rescue said: “Firefighters wearing breathing apparatus used two hose reel jets and an ultra-high pressure lance to tackle the flames which had spread to a nearby hedgerow.
“Crews left the scene at 10.15pm and another crew returned to the scene at 11.25pm to check for any further hotspots.
“This was an accidental fire that was caused by a spark from a combine harvester.”