One appliance and crew from Amersham and one from Gerrards Cross attended.
Smoke was visible in the area when they arrived.
The firefighters located a fire involving around 50 square metres of agricultural and building waste within a field. A 13 kg LPG cylinder was involved in the fire and venting.
The firefighters established a scene cordon and used one main jet and small gear.
Thames Valley Police was notified.