I agree, I think I have seen 5 messages on various forums about baling & what hp tractor is required in the past week.
Hp is _not_ the issue. A small older baler only takes 17 hp to run, add 10 hp to pull it & the tractor through the field, and an IHC H or old Ford can bale with 30 hp or less.
I do all my square baling (5,000 bales/ year) with a NH square baler & an IH 300 - a souped up H with ~36 hp - and I pull a rack with 130 bales or a bale basket on hills.
I could _never_ do that with a 45 hp compact utility tractor. You need to have a real tractor on the front of a baler, not a compact. The baler is actually run by a flywheel which can push 50 hp to the bale chamber on peak. You need a real tractor with a robust drive train to handle this shock load - keeping that flywheel spinning with such a variable load.
Also the baler is heavy & has a lot of heavy motion - you need a good heavy cast iron tractor to aborb those motions.
This is not a hp question - it is a whole tractor question.
a compact tractor makes a real poor baler tractor for several reasons. Buy an old 35-50 hp real tractor for $2500 if you want to bale square bales.
As to round bales, you can make a 4x4 bale with 45 hp, but there is again the weight issue - you can have the tail wagging the dog. Think about the inertia of spinning an 800 lb ball of hay behind you in a 3000# baler & controling it.... with your 2800# tractor?
--->Paul