According to the pilot, at the end of a day of aerial application flights, he received a call from a customer who wanted a small field sprayed that evening. The airplane was not equipped with lights for night spraying; however, the pilot felt there was still enough light to safely accomplish the 10-minute job. The flight departed from the pilot's private airstrip at dusk and proceeded to the job area, which was flat terrain with no obstructions except canal banks at each end of the field. The first of three intended spray runs was completed without incident. At the end of the second spray run, the pilot did not see the canal bank at the end of the field. The airplane impacted the canal bank, bounced into the air, glided for about 1/4 mile, hit a second canal bank, nosed over and came to rest inverted. The pilot stated that the accident could have been prevented "by not allowing anyone, including myself, to pressure me into doing something that I knew was a substantially higher than normal risk for very little benefit."