Debele, Tolessa, Du Preez, C.C. Ceronio, and G. M. 1. “Effect of Tillage Systems and Residue Management on Penetrometer Resistance of Nitisols under Maize Production in Western Ethiopia”. Ethiopian Journal of Applied Science and Technology 8 (2), 10-18. https://ejhs.ju.edu.et/index.php/ejast/article/view/695.