On July 9, 1999, at 1705 central daylight time, a Cessna A188B agricultural airplane, N731AR, was substantially damaged during a forced landing following a loss of engine power during climb out from an airstrip near Gheens, Louisiana. The instrument rated commercial pilot, sole occupant of the airplane, sustained minor injuries. The airplane was registered to and operated by Golden Ranch Aviation, Inc., of Gheens, Louisiana. Visual meteorological conditions prevailed for the Title 14 CFR Part 137 flight for which a flight plan was not filed. The flight originated from the operator's private airstrip approximately 5 minutes prior to the accident. The pilot reported that the airplane was loaded with 1,000 pounds of rice seed to be dispensed to rice fields within the company's 27,000 acre ranch. He further reported that the engine lost power following his first power reduction during the initial takeoff climb. The pilot was able to dump the payload as he maneuvered the airplane to clear trees in his path. The airplane touched down in a marshy grass area. Upon touch down, the main landing gear tires sank in the soft mud, and the airplane nosed over, coming to rest in the inverted position, partially submerged in water. The pilot reported that the left wing of the airplane separated from the airframe, the vertical stabilizer and rudder "were smashed," and the propeller assembly separated from the engine. The pilot reported that the 300-horsepower Continental IO-520-D173B engine, serial number 812837-R, had accumulated 144.9 hours since its last factory overhaul. Examination of the wreckage by the pilot and the FAA inspector revealed that the loss of engine power was the result of fuel starvation as result of a blocked fuel vent tube. In the enclosed NTSB Form 6120.1/2, the pilot recommends installing small mesh wire over the fuel vents to prevent vent blockage from occurring.