Musannaf Ibn Abi Shayba 28:184

Abu Mu'awiyah narrated to us, from al-Shaybani, from Abu 'Awn Muhammad ibn 'Ubayd Allah al-Thaqafi, who said: 'Umar imposed upon the people of al-Sawad, for every jarib—whether cultivated or uncultivated—one qafiz and one dirham. And upon a jarib of clover (alfalfa), five dirhams and five qafiz. And upon a jarib of trees, ten dirhams and ten qafiz. And upon a jarib of grapevines, ten dirhams and ten qafiz. And he did not mention date palms.