How that the feudal tax Champart Functioned?

Answer 1

It was one of the Noble privileges the French nobility kept over the free peasants after the end of serfdom in the 15th century :

"champart (work): to work the noble's private domain, to give the lord a portion of their harvest"

"CHAMPART, French law. By this name was formerly understood the grant of a piece of land by the owner to another, on condition that the latter would deliver to him a portion of the crops. IS Toull. n. 182."

"French nobility" : http://en.wikipedia.org/wiki/French_nobility

"Manorialism" : http://en.wikipedia.org/wiki/Manorialism

"Bouvier's Law Dictionary, Revised 6th Ed (1856)" : http://onlinedictionary.datasegment.com/word/champart