What is the zakat on grains and fruits, and what is the minimum taxable amount (nisab)?

Zakat (definition) is obligatory on grains and fruits by scholarly consensus, based on the Almighty's saying: "And give its due on the day of its harvest." It is a condition that they be measurable, storable, and reach a nisab (definition) of five awsuq (300 sa's). The amount of obligatory Zakat varies according to the method of irrigation: for what is irrigated without cost (like rainwater and springs), it is one-tenth; and for what is irrigated with cost (like irrigation with machinery), it is half of one-tenth.