At 11.13pm on Friday (24) one crew from Cambridge was called to a fire on the A1303 near Bottisham.
Firefighters arrived to find around two tonnes of baled straw alight. They separated the bales and extinguished the fire using a hose reel, while also damping the area around the stacks to prevent the fire spreading.
The crews returned to their station by 12.10am.
The cause of the fire was deliberate. Anyone with information can contact police on 101 or Crimestoppers on 0800 555111.