Bava Metzia 105 - Shavuot - June 12, 6 Sivan

Rava discusses more issues regarding a heiter iska. If a sharecropper who pays a fixed amount to the owner is not permitted to decide not to weed the field, for various reasons cited in the Mishna and Gemara. If one sharecrops for percentages and there is very little yield, the sharecropper does not assume responsibility. However, there is a minimum amount. What is that amount? The Gemara digresses to measurements in other areas of halakha including ritual impurity, particularly cases in which Rabbi Yannai takes a position. One who works in another's land as a chokher and a plague or windblast ruins the crops - in which scenarios can the chokher pay less than the agreed upon amount?