Yahya related to me from Malik from a reliable source from Sulayman ibn Yasar and from Busr ibn Said that the Messenger of Allah ﷺ said, "On land that is watered by rain or springs or any natural means there is (zakat to pay of) a tenth. On irrigated land there is (zakat of) a twentieth (to pay)."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ فِيمَا سَقَتِ السَّمَاءُ وَالْعُيُونُ وَالْبَعْلِ الْعُشْرُ وَفِيمَا سُقِيَ بِالنَّضْحِ نِصْفُ الْعُشْرِ