This is going to be my first year haying, and after doing considerable research, I learned that, as Richard said, the limiting factor is the baler. If you run a full sized baler, a compact tractor is way too small. In addition, a mower conditioner is the best way to cut hay, and a compact probably wouldn't run that either. I'm going to try my first harvest with a sickle bar mower (unless I find a moco cheap), but eventually I intend to get a moco. I just bought an Oliver 1550 for haying. It's 55 hp at the pto, and should be just enough to run everything.