IN THE REPORT OF THE ACCIDENT, THE OPERATOR STATED THAT THE AGRICULTURAL PILOT HAD LANDED BETWEEN APPLICATION FLIGHTS. THE CHEMICAL HOPPER WAS REFILLED; HOWEVER, THE PILOT ELECTED NOT TO ADD FUEL. WHILE ENROUTE TO BASE FOLLOWING THE LAST APPLICATION FLIGHT THE ENGINE QUIT BECAUSE OF FUEL EXHAUSTION. A FORCED LANDING ENSUED IN THE ONLY CLEAR AREA AVAILABLE.