THE PILOT COMPLETED A SMOKE DISPENSING RUN FROM WEST TO EAST ALONG THE NORTH EDGE OF A FIELD TO BE SPRAYED. THERE IS A POWERLINE ALONG THE NORTH EDGE OF THE FIELD. UPON COMPLETION OF THE SMOKE RUN THE PILOT EXECUTED A LEFT TURNAROUND. AT THE COMPLETION OF THE TURNAROUND THE AIRCRAFT COLLIDED WITH THE POWERLINE AND CRASHED.