Mosrt tractors can have the belt replaced without pulley removal,you may need to remove some guide pins or bolts that keep the belt in the pulley grooves though..dont give in to the temptation to simply bend them out of the way and hammer them back into position,it doesn't always work!..
I suppose you could use a strap wrench to keep the pulley from turning,but you'll need 3 hands to hold it still AND try loosening the pulley bolt..I have had to resort to drilling a hole in the pulley and used a punch shoved through the hole and butted against something on the chassis to hold the pulley still while removing that bolt,when I had no access to an impact wrench or air..I've used the breaker bar and 5 lb. hammer trick Maybar suggested many times with success too..sometimes they used locktite on those bolts and they can be a real bear to get off..I've had to heat a few up and ended up ruining the main seal on the engines crank in the process..for that reason I'd do my best to avoid removing that pulley unless you have no choice or its junk and has to be replaced..borrow an impact gun or take it to a gas station or something,it'll save a lot of grief..