I say, and with God's success: The factors that are prepared for work, like the cultivation of the land, are not subject to zakat unless they are for trade, in which case they are subject to zakat like trade goods; for Ali (may Allah be pleased with him) said: "There is nothing due on the factors" in Sahih Ibn Khuzaymah 4: 20, and Sunan Abu Dawood 2: 99. Refer to: Umdat al-Ri'ayah 1: 275, and Allah knows best.