A tractor driver is in hospital with lower leg injuries after he had to bail from the farm machinery when it started to slide down a hill.

The Waikato Westpac Rescue Helicopter was dispatched to a farm near Piarrere, east of Lake Karapiro, on Tuesday to fly the injured man to hospital.

'A tractor, towing a trailer, lost traction and slipped down a muddy slope, coming to rest approximately 20 metres down a very steep hill,” says a spokesperson for the rescue helicopter.

'The 24-year-old driver suffered abdominal and lower leg fractures after he attempted to bail out of the vehicle as it slid down the hill.

'The man was carried to the waiting rescue helicopter by the NZFE and was flown to Waikato Hospital for further assessment and treatment.”