The employee vs partner question holds the answer.  If he's working 10 or 12 hrs a day, but doesn't start till 8:00 or 9:00 or whenever, does it really matter when he gets out of the house?  If he's an employee and a specific start time is a condition of the job, then there has to be consequences of his actions.  I don't know what those consequences are...........you're the only one who can decide that.  Consequences have to be concrete and enforced, and must affect his bottom line (wallet).  But if he's a partner in the farming business,  you have to figure out a way to work with his preference to start later in the day ( and probably work later into the nite than you do ).