It will depend on the size and ply rating of your tire. Look on the sidewall of you tire or the owners manual for the recommend pressure.
An 8-ply 10-16.5 tire should have about 45 psi.
A 10-ply 12-16.5 tire should have about 40 psi.
My 10-ply 31.5-13-16.5 floatation tires only need 30 psi.