The rate of zakah differs according to the method of irrigation. If it is watered naturally without the use of artificial means, then the zakah payable is a tithe (one-tenth) of the produce. However, if it is irrigated by a mechanical device or with purchased water, then the zakah payable is half a tithe.
Mu’azh reports that the Prophet, upon whom be peace, said: “On that which is watered by the heavens, or by an adjacent water channel, a tithe is due. As for what is irrigated through a well or a stream, its zakah is half a tithe.” This hadith is narrated by alBaihaqi and al-Hakim, and is graded sahih.
Ibn ‘Umar reported that the Prophet, upon whom be peace, said: “On that which is watered by the heavens or springs or its own roots, a tithe is due, and on that watered by a well or a stream, half a tithe.” This hadith is narrated by al-Bukhari and others.
In case the land is watered equally by artificial as well as natural means, then zakah payable will be three-fourths of a tithe.
Ibn Qudamah stated that he did not know of any difference of opinion on the preceding hadith. If one method of watering is used more than the other, then for calculating zakah, this would be the determining factor. This is the view of Abu Hanifah, Ahmad, athThauri, and ash-Shaf’i (one of his two opinions).
All of the costs involved in harvesting, transportation, threshing, cleaning, storing, and others are to be borne by the owner from his property and should not be accounted for against the zakah to be paid.
Ibn ‘Abbas and Ibn ‘Umar hold that whatever is borrowed for the purpose of tilling, planting, and harvesting should first be taken out.
This is evident from their following statements reported by Jabir ibn Zaid that Ibn ‘Abbas and Ibn ‘Umar said that a man who borrows in order to spend it either on cultivation (of his land) or on his family must first pay off his debt, then pay zakah on the rest. Ibn ‘Abbas said: “First he must pay off what he spent on cultivation, and then pay zakah on the rest.” Yahya ibn Adam related this in al-Kharaj.
Ibn Hazm relates from ‘Ata that all expenses are to be deducted first. If zakah is applicable to the remaining amount, only then will it be paid.