The helicopter pilot reported that, after an agricultural application flight, he set the bucket down in a predetermined operations zone near a semi-truck loading hopper to be refilled. He added that another truck arrived to top off the semi-truck hopper, which emitted fertilizer dust and led to the pilot being concerned that it would deteriorate visibility. He advised the ground crew that he was going to temporarily move out of the operations zone. The pilot reported that he set the bucket in the new temporary operations zone. As the skid steer approached, he eased the helicopter backward to keep the other ground equipment in his view. The pilot heard a "bang," disconnected the helicopter from the long-line, and then landed the helicopter without further incident. Postaccident examination revealed that the auger from the semi-truck hopper was fully extended behind the helicopter and that a tail rotor blade had sustained substantial damage. The pilot reported that he might have backed the helicopter into the extended auger. The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation.