Is Zakat obligatory on the produce of land worked by a paid laborer who takes his wage (one-fifth), if the total produce reaches the Nisab, but the share of each heir, if divided, does not reach the Nisab? And is it permissible for the paid laborer to pay this Zakat?

Zakat (definition) is not obligatory on crops or fruits produced by the land if the share of each partner does not reach the minimum threshold (nisab (definition)), and combining the fruits does not affect the obligation of zakat. It is not permissible for an employee to dispose of the partners' money without their knowledge, and paying zakat without their permission is not sufficient. As for an employee working under a musaqat (irrigation) contract, he must pay zakat on his share if it reaches the nisab. However, if the employee works for a known wage (as a harvester - al-jadhdhadh), there is no zakat due on him because the fruit is not owned by him at the time zakat becomes obligatory.