Kent Fire and Rescue Service was called to approximately 200 tonnes of hay on fire in Longend Lane, Marden.
Over a period of nearly 24 hours, five fire engines attended. Crews used beaters and drag rakes to extinguish the flames and a hose reel jet to dampen down the surrounding area.
No casualties were reported.
Residents in the area have been asked to close their windows and doors due to smoke.