Tillage Effects on Soil Properties, Growth and Yield of Cocoyam (Xanthosoma sagittifolium Schott) on an Alfisol of Southwest, Nigeria

Hitherto information on tillage requirement of cocoyam (Xanthosoma sagittifolium Schott) is scarce on Alfisols of humid tropics. Five tillage methods were compared as to their effects on soil physical and chemical properties, growth and yield of cocoyam on an Alfisol at Owo in the forest-savanna transition zone of southwest Nigeria. The experiment which consisted of five tillage methods [manual clearing (MC), manual ridging (MR), manual mounding (MM), ploughing + harrowing (P+H) and ploughing plus harrowing twice (P+2H)] was carried out over 3 years at two sites in a randomized complete block design with three replications. In the first two years (2007 and 2008), P+H had the least soil bulk density and highest growth and yield, whereas in the third year (2009), MC produced the lowest soil bulk density and best performance of cocoyam. Manual clearing (MC) had the highest values of soil chemical properties in both years (2008 and 2009). Averaged over the 3 years, P+H, MR and MM had lower soil bulk density hence better growth and yield compared with P+2H and MC. Compared with P+2H, MC, MM, MR and P+H increased cocoyam cormel yield by 10, 21, 23 and 32%, respectively. The corresponding increases in corm yield were 7, 15, 13 and 21%, respectively. Bulk density rather than soil chemical properties dictated the performance of cocoyam in the Alfisol of the experimental area. Ploughing plus harrowing twice (P+2H) degraded soil quality. For small farms, either MR or MM is recommended while P+H is recommended for large scale farming of cocoyam. 1