Combinations of organic and inorganic fertilizers for vine, carotene and root yields of orange-fleshed sweetpotato at Umudike, southeastern Nigeria

Field experiment was conducted during 2013 and 2014 cropping season at Umudike, southeastern Nigeria, to  evaluate the effect of fertilizer combinations (poultry manure, NPK (15:15:15) and agrolyser) on two varieties  of orange-fleshed sweetpotato (Ipomoea batatas). The experiment was a split-plot laid out in randomized  complete block design (RCBD) with three replications. Combined application of 2.5 t/ha poultry manure + 200  kg NPK produced significantly higher leaf area index of 3.3, shoot biomass of 31.9 t/ha and multiplication ratio  of 1:48than the control or application of NPK or agrolyser alone. Application of 2.5 t/ha poultry manure + 200 kg  NPK also produced significantly higher average storage root yield of 29.1 t/ha than no fertilizer or agrolyser application, and also gave higher carotenoid level than application of NPK or the control. Umuspo 1 suppressed weeds more and significantly produced 598% higher shoot biomass and 125% higher average storage root yield than Umuspo 3. Umuspo 3 variety however, had a carotenoid level of 2268.1mg/g, which was higher than that of Umuspo 1 by 1860%. The highest net monetary returns from the cultivars accrued from a combined  application of 2.5t/ha poultry manure and 200 kg NPK while the lowest return was from where no manure was applied or where agrolyser was applied alone. Keywords : Carotene, fertilizer combinations, orange-fleshed, Ipomoea batatas, yields