Regenerative Versus Conventional Nutrient Management: Effects on Growth, Yield, and Nutritional Quality of Orange-Fleshed Sweet Potato Varieties in Akwa Ibom State, Nigeria

Abstract

An experiment was conducted at the Teaching and Research Farm of Akwa Ibom State University, Obio Akpa Campus, Oruk Anam Local Government Area, Akwa Ibom State, Nigeria, to evaluate the growth, yield, and nutritional quality of orange-fleshed sweet potato (OFSP) varieties (UMUSPO 1 and UMUSPO 3). The study was arranged as a split-plot experiment fitted into a randomised complete block design (RCBD) with three replications. The main plot consisted of the two OFSP varieties, while the subplot comprised five nutrient management treatments: no amendment (CA), 400 kg ha⁻¹ NPK fertiliser (CB), 5 t ha⁻¹ poultry manure + 200 kg ha⁻¹ organomineral fertiliser (RA), 10 t ha⁻¹ poultry manure (RB), and 5 t ha⁻¹ biochar (RC). The results revealed significant varietal differences in growth performance. UMUSPO 1 produced significantly higher numbers of leaves and branches per plant, whereas UMUSPO 3 recorded longer tuberous lengths. Nutrient management practices significantly influenced growth and yield parameters. The regenerative treatments, particularly RA and RB, consistently enhanced leaf production, branching, vine length, shoot biomass, root weight, and storage root yield compared with the conventional fertiliser and control treatments. The highest storage root yields were obtained under RA, while the control treatment recorded the lowest values across both varieties. The sweet potato varieties UMUSPO 1 and UMUSPO 3 showed contrasting nutrient profiles, with UMUSPO 3 being higher in beta-carotene and B vitamins and UMUSPO 1 being higher in zinc, iron, and calcium; vitamin C was unaffected by variety. Fertiliser application significantly improved all nutrients, with poultry manure and biochar performing best and no variety × fertiliser interaction. Organic amendments enhanced nutritional quality, and variety choice should match the target nutrient. The study demonstrated that regenerative nutrient management practices, particularly the combined application of poultry manure and organomineral fertiliser, offer a sustainable strategy for improving the growth, yield, and nutritional quality of orange-fleshed sweet potato.