Musannaf Ibn Abi Shayba 5:921

Ali ibn Mushir narrated to us, from al-Shaybani, from Abu Awn Muhammad ibn Ubayd Allah al-Thaqafi, who said: Umar ibn al-Khattab imposed upon the people of al-Sawad, for every jarib that water reaches—whether cultivated or uncultivated—one dirham and one qafiz of food. Upon orchards, for every jarib, ten dirhams and ten qafiz of food. Upon vineyards, for every jarib of land, ten dirhams and ten qafiz of food. Upon fresh fodder (al-rutab), for every jarib of land, five dirhams and five qafiz of food. He did not impose anything upon date palms, and he made them subordinate to the land. Upon the heads of men: upon the wealthy, forty-eight dirhams; upon the middle-class, twenty-four dirhams; and upon the poor, twelve dirhams.