The pilot attempted a practice 180-degree autorotation to a grass airstrip during a personal flight. The helicopter overshot the grass airstrip and touched down in an area of uncut grass that contained a tractor tire rut. During touchdown, the helicopter turned sharply to the left and then snap rolled to the right when the landing gear skid contacted the tire rut. The helicopter sustained damage to the tail boom and rotor blades resulting in substantial damage. The commercial pilot and passenger were uninjured.