While maneuvering during an aerial application flight, the airplane impacted two power lines. The 4,180-hour commercial pilot departed the grass airstrip with 65 gallons of water and grazon (chemical) on board. He entered the field from the south to spray on the west side of the field, and over trees. He descended into the field, and immediately impacted a utility pole and two power lines that were aligned east and west. The airplane was able to continue to fly to the airstrip and land.