The pilot reported that he took off and departed the airport traffic pattern. He stated that about two minutes after reducing power, the engine lost power. He stated that he checked the mixture and applied carburetor heat to no avail. He then announced his emergency and attempted to return to the departure airport. During the glide, he determined that he would not be able to make the airport and elected to land in a soccer field. After touchdown, he braked hard, but the airplane struck a berm which tore the nose landing gear from the airplane. Subsequent examination of the engine, carburetor, fuel selector valve, fuel shutoff valve, and the remainder of the fuel system failed to reveal any pre-impact anomalies.