The aircraft was at 4,000 feet descending toward the airport when the pilot intentionally ran the right fuel tank dry, then switched to the left tank. The pilot could not affect an engine restart and the aircraft landed in a plowed field about 2 miles short of the airport and encountered soft earth which sheared the landing gear off the aircraft, damaging the wings. FAA inspectors found that the right fuel tank contained less than 1 gallon while the left tank held 10 gallons. Each of the fuel tanks holds 40 gallons total. The flight manual for the aircraft cautions against takeoffs, landings or maneuvering with less than one quarter of fuel in the tank selected. The fuel pick up ports were noted to be in the rear corner of each fuel tank. The fuel system was functionally tested with no abnormality in system function found. The pilot stated that he made two trips between Brawley and San Diego without refueling the aircraft.