In order to develop a suitable soil management adapted to the low activity fragile dominant Alfisol in southwest Nigeria, two field experiments were carried out at two sites in 2007 and 2008 on Alfisols at Owo, southwest Nigeria to evaluate the effect of years, tillage and poultry manure on soil properties, plant height, cormel and corm yields of cocoyam. The treatments were five tillage methods: manual clearing (MC), manual ridging (MR), manual mounding (MM), ploughing plus harrowing (P+H) and ploughing plus harrowing twice (P+2H) and five poultry manure (PM) levels: 0, 2.5, 5.0, 7.5 and 10.0 Mg ha-1. These were factorially combined and arranged in a randomized complete block design and replicated three times. Years of study did not have effect on soil bulk density. Soil water content and soil temperature were significantly higher (p = 0.05) in 2008 compared with 2007. Among tillage methods, P+H had the least bulk density and highest plant height, cormel and corm yields of cocoyam while MC which had the highest soil organic matter, N, P, K, Ca and Mg, and the highest bulk density produced the lowest values of plant height, cormel and corm yields of cocoyam. Soil chemical properties, growth and yields were higher in 2007 than 2008; the reduction of cocoyam plant height, cormel and corm yields between 2007 and 2008 were 9.6, 7.5 and 10.3%, respectively. Bulk density dictated the performance of cocoyam in this study and not soil chemical properties. Poultry manure tended to lower soil bulk density and temperature, and increased soil water content, soil organic matter and soil nutrients. Poultry manure increased soil OM, N, P, K, Ca and Mg from 0 to 10 Mg ha-1. Poultry manure only increased soil K, Ca and Mg, growth and yield of cocoyam up to 7.5 Mg ha-1 which is the optimum value for cocoyam production on Alfisols of southwest Nigeria.

Keywords: Tillage, Cocoyam, Poultry manure, Soil bulk density, Soil water content, Soil chemical properties