The pilot had completed the aerial application of a field prior to spraying another agricultural field where the airplane experienced a partial loss of engine power. The pilot stated that when he applied engine power while executing a climbing right turn over the field, the engine lost power. Additional increases of the throttle control further reduced engine power. The pilot stated that had he not changed or reduced the throttle control setting, the engine would have not lost power. The pilot then executed a forced landing on a butte, which resulted in substantial damage to the airplane. The pilot was uninjured. No mechanical anomalies relating to the airplane were reported.