The pilot reported that before his 12th aerial application flight of the day, the airplane was overloaded with fertilizer due to faulty ground loading equipment. Knowing the airplane was overloaded the pilot decided to dump some of the fertilizer over the grass strip during takeoff. As the airplane reached the point on the grass strip that he felt he could safely stop, the “airplane felt like it was wanting to fly” so he continued the takeoff. As the pilot turned toward the field that he intended to apply the fertilizer to, the airplane settled and impacted in a field. The airplane sustained substantial damage to both wings, empennage, and fuselage, and the engine separated from the airframe. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. No Title 14 Code of Federal Regulations Part 137 certificate was found for the operator and there was no record of a knowledge and skill test for the pilot as required by 14CFR 137.19.