Influence of higher levels of NPK fertilizers on growth, yield, and profitability of three potato varieties in Surma, Bajhang, Nepal

Potato is a crucial food and cash crop with high yield potential in many parts of the Bajhang district. However, achieving optimal yields can be hindered by inconsistent NPK fertilizer application rates and suboptimal potato variety selection, including instances where no fertilizers are used at all by the farmers. To address these challenges and determine the most effective NPK fertilizer rates and potato varieties, a field experiment was conducted in Surma rural municipality of Bajhang district. The experiment utilized a randomized complete block design (RCBD) with three replications, to evaluate the effects of four NPK fertilizer rates (0:0:0, 50:50:50, 100:100:60, and 150:150:90 kg NPK/ha) and three potato varieties (Khumal Seto, Cardinal, and Bajhang Local), on growth, yield, and economic profitability. Statistical analysis, including analysis of variance and Duncan's multiple range test (DMRT), indicated that the highest values for plant height, canopy diameter, number of leaves, number of main stems, tuber weight, fresh weight of leaves and stems, average tuber diameter and number of marketable tubers per hill were consistently observed higher in either the Khumal Seto or Bajhang Local potato varieties. Similarly, these results were particularly prominent with the application of 150:150:90 kg NPK/ha. Economic analysis demonstrated that the Khumal Seto variety showed superior performance in terms of gross benefit, net benefit, and benefit-to-cost ratio (NPR 1,805,714.29, NPR 1,306,168.83, and 3.61, respectively) when compared to other varieties. Similarly, the application of 150:150:90 kg NPK/ha resulted in higher economic returns (NPR 1,645,714.29, NPR 1,129,908.83, and 3.19). In conclusion, using higher levels of mineral fertilizers (150:150:90 kg NPK/ha) with high yielding and well adapted potato varieties such as Khumal Seto and Bajhang Local significantly enhances growth, yield, and profitability in potato cultivation, as demonstrated by the findings of this study.