A woman was airlifted to hospital after a tractor overturned while spreading slurry.
The tractor rolled down a hillside.
It is understood the male driver was thrown from the vehicle 80ft down a wooded gully, but was not injured.
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A 23-year-old woman also in the cab at the time suffered serious injuries and was airlifted to hospital.
The incident happened on Tuesday afternoon at Leighton Reservoir, near Masham. Emergency services were called at 2.25pm.
Volunteers from Swaledale Mountain Rescue Team (SMRT) were called to the scene, along with police, firefighters, Yorkshire Ambulance paramedics, the North East Ambulance Hazardous Area Response Team and a Yorkshire Air Ambulance helicopter.
A spokesman for SMRT said: “The farmer had rolled a tractor with slurry tank down a steep wet hillside and was then thrown from the tractor another 80 feet down a wooded gully.”
The woman was flown to Leeds General Infirmary with serious injuries.
It is understood she suffered a badly broken pelvis.