Wall of Salt is lower level, by 1, and gives infinitely more salt per casting than most applications of flesh to salt.
138 lbs is 1 ft^3 of solid salt, 76 lbs if it is loose salt (The spell specifies solid rock salt, so it would be the former), according to the Salt Institute. 4.25 cubic feet of salt are made per caster level of the spell, which is a minimum of 7 (4th level spell).
4105.5 lbs of salt, per casting. Let's see that cow, now.