The boy was given first aid by a community first responder - a trained volunteer - before fire engines from Dover and Deal arrived on the scene, along with two South Coast Ambulance cars, two ambulances, the ambulance service’s Hazardous Area Response Team (HART) and the Kent Surrey Sussex Air Ambulance.
The emergency teams were able to free the boy within an hour, using hydraulic spreaders to part the rotavator blades. He was treated at the farm before being taken to Kings College Hospital, London.
Kent Police, who also attended the scene in Townsend Farm Road, St Margaret’s, said he was in a serious condition.
Richard Airey, media relations manager for South East Coast Ambulance, said: "The HART attended with ambulance crews after a teenage boy suffered a serious leg injury. The air ambulance also attended.
“They all worked together to treat the boy before the decision was made to take him by road to Kings College Hospital.
"Members of the air ambulance team went with him in the ambulance to continue treating him.”
"He was treated for injuries to his upper and lower leg."
The police are not treating the incident as suspicious and have referred the case to the Health and Safety Executive, which confirmed it has opened an investigation into the cause.