Alms Tax: Doubt Between Mixed and Manual Irrigation

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 1894

If a person doubts whether it would be commonly considered that their irrigation is by both means or by means of buckets of water and suchlike, it is sufficient to give one-twentieth [5%]. The same applies if he deems it probable that it would be commonly considered that their irrigation is by rain.

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