The agricultural airplane was substantially damaged when it impacted terrain during initial climb from runway 22 (2,784 feet by 40 feet, asphalt). Prior to departure the pilot completed a preflight inspection of the airplane, including loading the airplane with 350 gallons of an aerial application chemical and 125 gallons of avgas, and warming up the engine. The pilot reportedly did not experience any engine problems during the takeoff ground run, but he noted that the tail took longer than normal to come up into a flying position. The airplane became airborne about two-thirds down the runway. After liftoff, the pilot lowered the aircraft nose to gain additional airspeed and increased engine power because the airplane's performance was reportedly "sluggish." After the airplane had cleared some irrigation equipment the pilot lowered the nose again in an attempt to gain additional airspeed, but the airplane was "vibrating and felt rough." The pilot then noted trees and houses ahead of the airplane and began a slight right turn to clear them. The airplane "stalled" and impacted terrain while the pilot attempted to avoid the obstacles. The aircraft's type-certificate data sheet lists the maximum gross weight as being 9,260 lbs. The pilot reported that the airplane's gross weight was 10,500 lbs, but supporting documentation for the gross weight increase was not located. The airplane's weight at departure was reportedly 10,289 lbs.