Alms Tax: Doubt Regarding the Method of Irrigation

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 1893

In the event that one doubts whether it would be commonly considered that their irrigation is by both means or, for example, by rain, then it is sufficient if he gives three-fortieths [7.5%].

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