Air Tractor - Extreme aerial application - How low can you go?

Air Tractor 402B crop duster spraying a field of wheat. Pilot is doing this for a job everyday for the past 30 years and more. Aircraft has a turbo prop Pratt & Whitney PT6A engine. The same engine as in a Air Tractor AT-802 but just a a much lower power setting. This was this pilot’s last season before retiring as a crop duster pilot at the age of 70. Aerial application is commonly used when crops can be damaged by agricultural machinery. Low flying is an everyday occurrence for an ag pilot.