One appliance and crew from Newport Pagnell, one from Broughton, one from West Ashland, along with an officer attended.
Hay bails were on fire near to a farm building.
The firefighters used two sets of breathing apparatus, one hose reel jet, small gear and a positive pressure ventilation fan.
A full road closure was put in place.
The firefighters reinspected the scene later on that evening to check for hot spots.
