I am a Hunter Safety Instructor.
Part of the Hunter Safety Course requires the student to ask permission from(me) the landowner in their field test. We emphasize to the students they should be polite, tell the landowner they have graduated from Hunter Safety and if he/she says no, thank them for their time and leave.
If the person grants permission tell them you could spend a weekend or two doing chores in the summer, give him a stick of venison sausage or something and pick up any litter you find. Also, it' s not a bad idea to inform a farmer of a possible problem with some fencing if you see it.
You are representing all of us. One slob will ruin it for others for years as someone already stated.
I don' t like knocking on doors myself but since I don' t own any land, I don' t have much choice.
Good Luck.

Tim