THE PILOT STATED THAT APROX 20 YARDS INTO THE TAKEOFF ROLL THE NOSE WHEEL SANK INTO A SOFT SPOT IN THE CENTER OF THE GRAVEL STRIP AND COLLAPSED. THE PILOT ALSO STATED THAT THE SOFT SPOT WAS HARD TO SEE, AND THAT THE RUNWAY APPEARED TO HAVE BEEN RECENTLY GRADED. THE ALASKA AIRPORT FACILITY DIRECTORY CAUTIONS PILOTS THAT THE CONDITION OF THE RUNWAY IS NOT MONITORED.