<p>Water scarcity and soil salinization constrain irrigated agriculture in semi-arid regions. Desalination technologies offer promising solutions, but their agronomic and economic performance under field conditions remains insufficiently documented. This study evaluated the effects of nanofiltration (NF) and electromagnetic (EM) water treatment on irrigation water quality, soil salinity, crop performance, and economic outcomes for potato cultivation in Tunisia. A spring field experiment compared three irrigation treatments: untreated saline water (SW), EM-treated water, and NF-desalinated water. Water quality, soil electrical conductivity, plant growth, yield, tuber quality, and production costs were assessed. NF significantly improved irrigation water quality by reducing salinity and major ion concentrations, which lowered soil electrical conductivity and enhanced nutrient uptake. These improvements resulted in higher biomass and tuber yield compared with SW. Although NF achieved the best agronomic performance, it also generated substantially higher production costs. EM provided intermediate agronomic results at lower cost, making it a more economically viable option under saline conditions. Overall, the findings underscore the trade-off between desalination efficiency and economic feasibility and highlight the need for long-term field evaluations to determine the sustainability and profitability of these technologies.</p>