ABSTRACT

This research work was designed to investigate the effect of different integrated soil nutrient management methods and storage period on the nutrient content and carotenoid profile of two orange fleshed sweet potatoes (OFSP). There were eight levels of integrated soil nutrient management: control, poultry manure at 10 t/ha, poultry manure at 5 t/ha, NPK:15:15:15 at 400 kg/ha, Agrolyser at 5.3 t/ha, poultry manure at 2.5 t/ha plus NPK at 200 kg/ha, poultry manure at 5 t/ha plus NPK at 200 kg/ha, Agrolyser at 2.7 kg/ha plus NPK at 200 kg/ha, poultry manure at 2.5 t//ha plus NPK at 200 kg/ha plus Agrolyser at 2.7 kg/ha and two varieties of orange fleshed–sweet potato: Umuspo 1 and Umuspo 3. Mineral, vitamin, anti-nutrient and proximate composition of the tubers were also analysed using standard methods. High performance liquid chromatography (HPLC) was used to determine the carotenoid profile in two varieties of orange fleshed sweet potato as influenced by integrated soil nutrient management and storage period. Integrated soil nutrient management significantly (p ) increased the mineral, vitamins, anti-nutrient, proximate content. Ipomea batatas grown on soils treated with poultry manure at 2.5 t/ha plus NPK at 200 kg/ha plus Agrolyser at 2.7t/ha had the best nutrient composition for the two varieties. There was significant (p ) increase in the Lutein (2.37 μg/100g to 4.83 μg/100g); zexanathin (2.03 μg/100g to 3.84 μg/100g); β-cryptoxanthin (7.31 μg/100g to 10.99 μg/100g); all-trans (84.41 μg/100g to 89.88); total β-carotene (89.89 μg/100g to 94.24 μg/100g) after 6 weeks of storage in almost all the potato samples. Alpha-carotene, 13-cis and 9-cis decreased significantly (p ) after 6 weeks of storage. The percentage retention of carotenoid was better in Ipomea batatas grown of soil subjected to Agrolyser at 5.3 t/ha for Umuspo 1 variety while in Umuspo 3, higher percentage retention of carotenoid was from Ipomea batatas treated with poultry manure at 5 t/ha plus NPK at 200 kg/ha, and poultry at 2.5 t/ha plus NPK at 200 kg/ha plus Agrolyser at 2.7 kg/ha. Storage significantly (p ) increased the mineral, fat, ash, carbohydrate and fibre content of the sweet potato samples while anti-nutrients and vitamins content decreased significantly (p ) with increase in storage period.