The aircraft was engaged in joy flights at an agricultural field day. Operations were being conducted from a paddock with a downslope of 7 toward the north. Part of the paddock had been slashed for a helipad, leaving a thick layer of loose hay on the surface. The pilot had been using the slipperyness of the loose hay to assist in obtaining translational lift, by turning and sliding the skids down the slope. He reported that the wind had been variable from the north-west. On the last take-off, the helicopter became airborne but failed to climb above about 10 feet. The rotor RPM began to decrease and the helicopter started to descend. The pilot started "milking" the collective and noticed that the wind had swung to a westerly and increased to about 15 knots. He considered turning into wind but was concerned that he would either have to land in the long grass adjacent to the pad, or that he would have problems outclimbing the heavily populated exhibition area to the west. He was also concerned that he would not be able to outclimb a set of powerlines to the north over which he had normally flown on climb out. He elected to land down the slope in a north-north-westerly direction. He flared for landing and the helicopter touched down gently, slightly tail first. As it rocked forward onto the skids the tail rose up into the main rotor disc. Part of the tail frame and tail rotor drive shaft were severed. The helicopter came to rest approximately 50 metres from its parking position at the top of the pad.