The pilot had serviced the airplane prior to an aerial application flight of a field during which the airplane lost engine power. The pilot performed a forced landing in a northerly direction on a hard surface road near the field, which had corn along its left side and a pole along its right side. While the pilot was trying to avoid the pole along the right side of the road, the airplane impacted the corn and terrain with its left wing resulting in substantial damage to the airplane. The left and right wings were buckled and bent from the impact. The pilot was uninjured. Examination of the airplane revealed that the oil filler cap was not installed resulting in a total loss of engine oil. The oil filler cap was found in the lower portion of the engine nacelle.