Nutrient Uptake and Efficiencies of Orange-Fleshed Sweet Potato (Ipomoea batatas L.) Varieties under Different Rates of Nitrogen and Phosphorus Fertilizers

Sweet potatoes serve as a staple food and animal feed in Africa and serve as a source of raw materials for the food, feed, pharmaceutical, cosmetic, chemical, and energy industries. The yield of orange-fleshed sweet potatoes is increased when nitrogen (N) and phosphorus (P) are added to low-fertility soils. The objective of this study was to evaluate the nutrient uptake and use efficiency of orange-fleshed sweet potato varieties under applied N and P. The experiment was conducted for two growing seasons (2019 and 2020) under rain-fed conditions in the field. The study included five orange-fleshed sweet potato varieties (Kulfo, Kabode, Alamura, Dilla, and NASPOT-12), three N levels (0, 23, and 46 kg·N·ha−1), and two levels of P (0 and 46 kg P2O5·ha−1) fertilizers designed in 5 × 3 × 2 with α-lattice design in factorial arrangement using 3 replications. The interaction effect of variety, N, and P fertilizers affected nutrient uptake, physiological efficiency, and agronomic efficiency of sweet potatoes. NASPOT-12 was the better variety in nutrient uptake but poor in apparent recovery at all levels of N and P. The highest nutrient uptake, agronomic efficiency, and physiological efficiency were observed on NASPOT-12 when subjected to 23 kg N·ha−1 and 46 kg P2O5·ha−1. Overall, NASPOT-12 with 23 kg·N·ha−1 and 46 kg P2O5·ha−1 could be recommended for its high nutrient uptake, agronomic, and physiological efficiencies