ABSTRACT

The experiment was carried out in 2019 cropping season at National Root Crops Research Institute (NRCRI), Umudike, to assess agronomic attributes of sweet potato varieties (Ipomea batatas (L)) under the application of nitrogen fertilizer (urea). A piece of land was cleared and thrash packed. It was slashed, ploughed, harrowed and ridged mechanically with tractor and converted to plots of beds with an Indian hoe manually. The size of each bed measured 1 m x 1.5 m with a space of 0.5 m separating the plots and 1m separating the replicates. Thirty three sweet potato vines each measured 30 cm long and four nodes were planted on each bed at a spacing of 10 cm x 20 cm resulting to plant population density of 500,000 plants /ha. The experiment was laid out as 5 x 2 factorial in a randomized complete block design (RCBD). The treatments consisted of two factors, Factor A comprised of five rates of Nitrogen (Urea) fertilizer (0, 30, 60, 90 and 120 N kg/ha) whereas factor B consisted of two varieties of oranges fleshed sweetpotao (Umuspo 1 (king) and Umuspo 4 (solo gold). These two factors produced ten (10) treatment combinations replicated thrice to a total of thirty (30) observations. The fertilizer rates were applied to the crops four weeks after planting (WAP). Data were collected on vine length, number of leave, number of branches, yield parameter and weight of above ground biomass (kg) and were subjected to Analysis of Variance (ANOVA) with Genstat (2003) edition (windows). Significant difference was determined and means separated with Fisher’s least significant difference (F-LSD) at 0.05 significant level. Results showed that application of Nitrogen (urea) fertilizer and variety significantly (p<0.05) affected the number of branches, vine length, number of  leaves, weight of above ground biomass (kg), number of cuttings (vine yield) at different sampling period, while their interactions were non-significant. Umuspo 4 variety produced the highest yield compared to Umuspo 1 variety. Nitrogen fertilizer (urea) application at the rate of 120kg/ha produced the highest number of vine cuttings.