A: Firstly,
Zakah
is due on grains and fruits that provide nourishment, if they reach the Nisab (the minimum amount on which Zakah is due), which is 300 Sa` (1 Sa`=3 kg. Approx.) according to the Sa` of the Prophet (peace be upon him). The Zakah would then be one-tenth of the harvest if the land is irrigated without any expenditure, and half of one-tenth (i.e. one-twentieth or 5%) of the harvest if the irrigation involves expenditure. In addition, being indebted does not exempt you from paying Zakah.
Secondly,
it is not permissible for someone who is obliged to pay Zakah to be deceptive in paying it by deducting it from a debt which another owes them; as Zakah is meant to purify wealth. (Part No. 9; Page No. 196) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.