The aircraft was departing from an 1100 metre grass strip which contained some soft patches. The pilot reported that the aircraft became airborne after a takeoff roll of approximately three quarters of the strip length. He deliberately adopted a shallow climb angle to build up speed. Shortly after crossing the upwind end of the strip, the pilot felt the aircraft sink. The left main landing gear contacted the ground and was torn from its mount. The aircraft came to rest about 200 metres beyond the end of the strip. The pilot was familiar with the strip but this was his first flight into the strip in a PA-32 aircraft. Previous operations had been in an aircraft of significantly higher performance. Although the pilot had 73 flying hours on type, his only PA-32 experience in the previous seven years was two and one half hours in the 24 hours before the accident.