Edem, I. D., U. C. Udoinyang, and P. I. Udounang. “Tractor Effects on Soil Properties and the Consequences on Cassava (Manihot Esculenta Crantz) Yield in Ultisol”. International Journal of Environment 4, no. 1 (February 22, 2015): 210–223. Accessed April 23, 2024. https://www.nepjol.info/index.php/IJE/article/view/12190.