The fire was reported about 4:30 p.m. Monday and burned about five acres on a farm on Mamer Lane, just north of Lewis Lane.
Kuna Fire Chief Bruce Allcott said the fire was fed by old wood, railroad ties, equipment trailers and a fifth-wheel camper, which was gutted in the blaze. "It was mostly a trash fire," Allcott said.
No structures were damaged, but because houses were nearby, firefighters from Kuna were assisted by the Nampa, Meridian, Melba and Upper Deer Flat fire departments. Three engines, two water tenders and two brush trucks were deployed.
"There's houses around and when the smoke's that bad, you've got to get on it," Allcott said.
The fire was apparently caused by a tractor operated by the farm owner. "We don't know exactly," Allcott said. "It could have been or spark from the exhaust or just something hot underneath."