Optimizing intra‑row spacing and seed tuber weight to enhance yield, quality, economic return, and profitability of potato (Solanum tuberosum L.) in Nepal

Potato (Solanum tuberosum L.) is an important food and cash crop in Nepal, but its yield remains below potential partly due to suboptimal plant spacing and seed tuber size management. This study evaluated the effects of three intra-row spacings (70 × 25 cm, 70 × 35 cm, 70 × 45 cm) and three seed tuber weight classes (21-30 g, 31-40 g, 41-50 g) on growth, yield, tuber size distribution, starch yield, and economic performance of potato cv. MS-42 under subtropical lowland conditions in Chitwan, Nepal. The experiment was conducted in a 3 × 3 factorial randomized complete block design with four replications from November 2020 to March 2021. Intra-row spacing significantly affected plant height, leaf number, biomass, and tuber yield, while seed tuber weight influenced plant height, canopy diameter, stem number, tuber number per hill, yield, tuber size distribution, and starch yield. The closest spacing (70 × 25 cm) produced the highest total (32.97 t/ha) and marketable yield (30.01 t/ha), whereas the heaviest seed tuber class (41-50 g) gave the highest yield (29.57 t/ha) and benefit-cost ratio (2.83). Heavier seed tubers increased the share of large tubers (>60 g) and starch content. Economic analysis showed that 70 × 25 cm spacing combined with 41-50 g seed tubers maximized gross return (Nepalese Rupees [NRs.] 1,094,271/ha) and net return (NRs. 707,668/ha). These findings suggest that this treatment combination can provide a high-yielding and profitable option for smallholder potato production under comparable subtropical lowland conditions. However, further multi-season, multi-location, and multi-cultivar validation is needed.