Cessna 206 Pilot reported loss of control while landing on a dirt runway. The aircraft's tires ran into a parallel ditch and became stuck.

Narrative

While operating in ZZZZ off of a private strip; the Cessna 206 had a subsequent runway excursion/veer off to the right. The morning of the flight; the pilot did a full preflight walk around; visually inspected all airworthiness; and registration documents; calculated weight and balance checked the fuel and checked the weather for the local flight around the pattern to get familiar with the runway and area. The narrow private dirt runway has a large crown in the runway surface with subsequent ditches on both sides of the dirt strip for water runoff. Upon landing the opposite end of the runway becomes obscured and not visible due to terrain pitching down after about 1/3rd down the runway. The Cessna 206 was modified with increased larger tires; wingtip extensions; and vortex generators to help handle the rough limestone dirt runway. While on the roll out after landing Runway XX on the center line; the plane started to drift slightly right of center line due to possible wind gust or other factors like low tire pressure. Because of the large crown in the runway the plane was pulled to the right of center line; the pilot used full left rudder to bring the plane back to center line to no avail. Brakes were applied as well; the large oversize tires were sucked into the 2-3 foot deep soft mud ditch on the right side of the runway. Once in the ditch there was no way to get out other than to stop; then use equipment to pull it out. The aircraft ended up becoming stuck in the soft mud of the ditch. Some contributing factors were the large crown on the runway; the down sloping terrain after the first third of the runway; the deep ditches right next the sides of the runway. New runway and location the pilot had not flown before. Large oversize tires and ditches in very close proximity to runway edge. To help make it so this never happens again; I would advise the airport owner to flatten out the large crown in the runway so it is more flat. The deep ditches on both sides of the runway should have drains put in and covered so water can go in but airplanes cannot. The runway should be widened. Where the single taxiway meets the runway; the taxiway should not be higher than the runway. The runway should be routinely graded because of other use besides flying.