I have powered a 7' haybine and a IH 37 sq baler easily with both our L2550 and L3450 tractors. -- We have gone to a drum mower now because of slow cut speeds or clogs with the haybine. -- I think a 9' would be ok if the haybine cutter is in good shape and you dont have hills.I am wondering if a L3540 is too small to pull a 540 pro rated 9ft haybine and a square baler around? Wife needs bales for her horses, hope tractor will be big enough.
If used lightly its ok. But in heavy rows the plunger motion and compression forces for firm bales can react enuf against travel speed to throw the HST trans into pressure relief with every stroke. If that happens it will eventually fail the trans.I think you will be fine. My dad cut, raked, and baled hay for about 12 years with a B8200 hst and still hadn't had any issues with it. It was not ideal and you had to be careful since the baler was heavier than the tractor but it was what he had and it worked.
I wondered the same question myself as I have the L3430HST. While I have not gotten into hay yet, I came across this thread where member rankrank1 offered some good advice about smaller balers that may work for you.
http://www.tractorbynet.com/forums/haying/138497-small-hay-baler-search.html
I am eager to follow this discussion as it seems from my reading that tractors of this size could bale a few acres of flat land going slow and not also towing a wagon behind the baler.
I've seen a BX run a small square baler although I had to laugh at what the plunger was doing to the tractor!!!