Alms Tax: The Amount of Zakat Based on the Method of Irrigation

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 1891

If wheat, barley, dates, or grapes are irrigated by rain or a stream, or if like in Egypt, crops use the moisture in the earth, the zakat on them is one-tenth [10%] of them. If they are watered by buckets of water or by means of a pump and suchlike, then the zakat on them is one-twentieth [5%].

-Ayatullah Sistani, Practical Laws of Islam, Alms Tax (Zakat)