The amount of zakah on produce from the earth.

The Shaykh : But what is the amount of zakah on produce from the earth? If it is watered at a cost, it is half of one-tenth; if it is watered without cost, it is the full one-tenth. This is because the Prophet (peace and blessings be upon him) said: The difference between the two is clear, for the farmer who waters at a cost labors over it, whereas the one who does not water at a cost does not labor over it. These are the zakah-eligible assets, and the details of this are found, praise be to Allah, in the books of Islamic jurisprudence. Many people, indeed many young people, study this in the curricula of primary, middle, and secondary schools.