Worku Burayu, Sombat Chinawong, Rungsit Suwanketnikom, Thongchai Mala, & Sunanta Juntakool. (2006). Tillage System and Fertilizer Rate Effects on Sorghum Productivity in the Central Rift Valley of Oromiya, Ethiopia. Agriculture and Natural Resources, 40(1), 1–10. retrieved from https://li01.tci-thaijo.org/index.php/anres/article/view/243498