Firefighters from Huntingdon, Sawtry and St Neots were in Little Stukeley on Friday evening after reports of a straw fire.
At about 9.15pm firefighters were called to find around 250 tonnes of baled straw alight.
A spokesman for Cambridgeshire Fire and Rescue Service said: "Fire crews managed to contain the fire and stopped it from spreading to nearby machinery. The fire was allowed to burn out under supervision.
"The crews remained at the scene until the early hours of the morning and carried out regular inspections to ensure the area was safe."
The fire service said that, following an investigation, the cause of the fire was determined to be accidental.