The experiment was carried out in two cropping
seasons (2004/2005 and 2005/2006) at research
farms of National Root Crops Research Institute
(NRCRI), Umudike located on longitude 07° 33΄ E
and latitude 05° 29΄ N. The soil was a sandy loam
with acidic reaction which characteristics were as
follows: Soil pH 5.20 and 4.90 (1:2.5 soil: water),
organic carbon 0.81 and 1.24%, total N 0.14 and
0.16%, available P 30.0 and 28.3 cmol/K,
exchangeable K 0.16 and 0.14 cmol/kg for
2004/2005 and 2005/2006 experiments,
respectively