Potato (Solanum tuberosum L.) Tuber Yield and Yield Components as Influenced by Different Levels of Nitrogen, Phosphorus and Potassium in Rwanda

Despite potato yield potential, its intensification level remain low in Rwanda, translating into low yield occasioned mainly by the decline in soil fertility. Field experiments were conducted in Birunga, Mudende [L₁]) and Buberuka, Rwerere [L₂] highlands Agro-Ecological Zones (AEZs), during September- December 2016 and March-June 2017 crop growing seasons to determine the effects of varying rates of N, P and K on potato tuber yield and yield components. The experiments were laid out using randomized complete block design with factorial arrangement, with four replicates. Factors were N rates (N_X) i.e  N₁-0 kg ha^-1, N_{2 –} 50 kg ha^-1, N_{3 –} 100 kg ha^-1 ; P₂O₅ rates (P_X) i.e P₁-0 kg ha^-1, P_{2 –} 50 kg ha^-1, P_{3 –} 100 kg ha^-1and K₂O rates (K_x) i.e K₁- 0 kg ha¹and K₂- 50 kg ha^-1. Number of tubers per plant, fresh tuber weight, small tuber yield, medium tuber yield, large tuber yield and total tuber yield were measured. Analysis of variance, performed using SAS-version 9.2, revealed that interaction effects of N×P×K were very highly significant on all parameters. Generally, N₃×P₃×K₂ performed better than other treatments and recorded highest tuber yields in all situations: (32.73 ± 0.43) t ha^-1[L₁] and (29.36 ± 0.41) t ha^-1 [L₂] and (31.05 ± 0.52) t ha^-1for pooled ANOVA. Contrarily to what happened at L₂, N₃P₃K₂ andN₂P₃K₂ were not significantly different at L_1. N₂P₃ K₂ is recommended to L₁ whereas N₃P₃K₂ is recommended to L₂.