Firefighters were called to the ''extensive'' blaze about 4pm, after a tractor making bales set straw stubble alight on the Whiteside farm about 4km southwest of Waiwera South.
Southern Baling Ltd driver Chad Cullen said he was just completing a bale when he saw flames emerge near the right-hand tyre of the tractor.
He stopped the vehicle quickly, and attempted to extinguish the embryonic blaze with an on-board fire extinguisher.
Unfortunately, that proved ineffective.
''In these conditions, once it starts, that's it. Straw burns.''
Mr Cullen was unharmed.
Farm co-owner Tom Whiteside, also present when the blaze started, praised the response of firefighters in bringing the fire under control quickly.
''We've had a fantastic response from the boys here and, as you can see, the farm has managed to avoid any significant losses thanks to their quick action.''
About five bales had been lost, and there had been ''minor'' damage to a shelter belt. He estimated 1.5ha of stubble had been burnt.
An adjacent paddock had been cropped and burnt off last week, preventing a potentially bigger fire and more serious financial losses.
''It's just a bit of good luck we got that out of the way. These things happen.''
Firefighters and tankers from Clinton, Waiwera South, Gore, Balclutha, Clutha Valley and Papatowai were summoned to the incident when it began.
A team including four appliances, three tankers and at least 15 firefighters brought the blaze under control by about 4.25pm.
After a northwest breeze picked up, firefighters remained on the scene to damp down the still-smouldering tractor and several small bale fires until 6.30pm.
Waiwera South fire chief Maurice Walter said under windier conditions, the fire could have caused more extensive damage.
''The tractor and baler were pretty well gone when we arrived, so we concentrated on a hedge that had become involved near buildings. Those have been saved, fortunately, so everything's gone OK.''
