The pilot reported that he and the pilot-rated passenger, departed from the turf runway in calm wind conditions. During the initial climb, the airplane’s climb rate was not as expected and he attributed this degraded climb performance to likely being the result of the addition of the passenger’s weight. Upon reaching 200 feet above ground level (agl), the pilot began a 180-degree turn to the north in an effort to gain altitude while avoiding maneuvering over obstacles and a more densely populated area. As the airplane entered the bank, the pilot felt a degradation in performance despite indications that both the engine power and airspeed were adequate. The airplane was not maintaining altitude and in an effort to avoid colliding into a subdivision, the pilot increased the bank angle. The airplane subsequently collided into terrain and came to rest in a ditch adjacent to the airport’s perimeter fence. During the accident sequence the airplane sustained damage to the wings and empennage. The pilot further stated that he believed the airplane’s descent during the turn was a result of either of the following: a downdraft, too high angle-of-attack attitude, or possible decrease in engine power output. He reported no mechanical malfunctions or failures with the airplane that would have precluded normal operation. The passenger opined that the accident was a result of the airspeed being too slow for the steep bank angle.