Potato is one of the most important food security and cash crops in Ethiopia. It is constrained by poor soil fertility. A field experiment was conducted at Assosa Agricultural Research Centre to investigate the effect of phosphorus and potassium fertilizers on the growth performance and yield of potato. The experiment was laid out as a randomized complete block design (RCBD) in 4×6 factorial arrangement of potassium (0, 100, 200 and 300 kg K2O ha-1) and phosphorus (0, 46, 92, 138, 184 and 230 kg P2O5 ha-1) in three replicates. A potato variety, Gudanie (CIP-386423-13) was used. Analysis of the data revealed that the interaction effect of both phosphorus and potassium did not influence the phonotypic, growth parameters and tuber yields of potato, but their main effect they significantly influenced days to 50% flowering, physiological maturity, plant height , marketable and total tuber yields, leaf area, above and underground dry biomasses. Optimum above and underground dry biomass (232.11 and 494.74 Mg* ha-1), marketable (23.94 kg K2O ha-1) and total tuber (29.56 kg K2O ha-1) yields were attained at 200 kg K2O ha-1 ; for phosphorus, optimum marketable tuber (23.30 Mg ha-1), total tuber (28.83 Mg ha-1), and yield of above ground and underground dry matter (218.48 and 479.60 Mg ha-1) were attained at 138 kg P2O5 ha-1. The lowest yield obtained from above ground and underground dry matter, marketable and total tuber in both fertilizers were recorded at zero level.
Key words: Fertilizer rate, phenotypic parameter, plant height, biomass, tuber yield, 1 Mg (Megagram) = 1000 kg.
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