Asian Journal of Research in Crop Science

The objective of the present investigation was to evaluate the effect of location and NPK fertilizer on three sweet potato varieties raised in Triple S system in south eastern Nigeria. Sweet potato is usually produced by small holder farmers living in marginal and fragile environments, the crop has been reported to respond to good soil fertility or fertilizer application. The development and introduction of new varieties of sweetpotato have resulted in yield improvements in the humid forest zone of south eastern Nigeria, but sustainable production has been constrained by poor soil fertility, due to high rainfalls which create problem through leaching of nutrients in the sandy loam ultisols of the region. The study was conducted in 2019 and 2020 in southeastern Nigeria to determine the effect of location and NPK fertilizer (15:15:15) on three sweet potato varieties raised in the Triple S system (storage in sand and sprouting). The experiment was laid out as a split-split plot in a randomized complete block design with three replications. Two locations in Abia state (Obingwa and Umuahia), southeastern Nigeria were the main plot treatments. Subplot treatments were three sweet potato varieties (white-fleshed T1S87/0087 and orange-fleshed Umuspo1 and Umuspo 3), while the sub-sub plot treatments were three levels of NPK fertilizer (0, 200, and 400kg/ha). Leaf area index at 8 and 12 WAP in 2019 and shoot biomass and storage root yield in both years were significantly higher in Obingwa than Umuahia location. The white-fleshed T1S87/00867 and orange-fleshed Umuspo1 varieties had higher values for above-ground biomass than orange-fleshed Umuspo 3, but the latter had significantly highest storage root yield, followed by Umuspo 1. In both cropping seasons, there was a linear increase in leaf area index, shoot biomass and storage root yield with an increase in NPK fertilizer up to 400kg/ha. The highest root yield was obtained from Umuspo 3 at Obingwa site when NPK fertilizer was applied at 400kg/ha. Decisions on the use of higher fertilizer rates must be based on economic considerations given the high costs of fertilizers, which in most cases are beyond the reach of the resource-poor farmers.