The pilot said he landed the airplane on the sod strip, and that all three landing gear touched down at the same time. He said the airplane bounced, touched down, and the airplane nosed over and came to rest inverted. The nose landing gear was separated from the airplane. Examination of the fracture surfaces on the nose landing gear components revealed that all failures were due to overstress. The pilot said there were no mechanical deficiencies with the airplane prior to the accident.