Management of saline water through desalination or blending with low salinity canal water may be a viable strategy for potato irrigation in semi-arid regions having saline ground water and scarce canal water. A 4-year study was conducted to investigate the effects of four water qualities canal water (CW), desalinated water (DSW), saline ground water (GW) and mixed water (MW) (CW + GW), three N-P-K-fertigation levels F100 = 100% NPK (190, 28.4 and 53.9 kg ha−1 of N, P and K, respectively), F80 = 80% NPK and F60 = 60% NPK and their interaction on the performance of two potato varieties grown in a sandy loam alluvial soil of semi-arid region. The electrical conductivity (EC) of CW, DSW, GW and MW ranged from 0.3 to 0.4, 0.2–0.3, 3.2–4.2 and 1.8–2.2 dS m−1, respectively. Drip irrigation with GW resulted in 21–44% reduction in total tuber yield compared with CW, however, the maximum reduction (54%) was observed in grade-A tuber yield that was accompanied by a considerable increase in grade-C tuber yield. Irrigation with MW increased total tuber yield by 9–37% compared with GW. Irrigation with DSW manifested a 41% and 14% increase in total tuber yield as compared with GW and MW, respectively. The tuber yield obtained with MW was comparable with DSW up to soil EC1:2 of 0.65 dS m−1, and beyond that level, DSW was observed to be superior. The variety ‘Kufri Surya’ had slight yield advantage over ‘Kufri Pukhraj’ when CW, DSW and MW were used, however, yields of both varieties were statistically at par under GW irrigation. The variety ‘Kufri Jyoti’ exhibited a 13–22% yield advantage over ‘Kufri Surya’ for all irrigation water qualities. Plant growth and yield attributing parameters were the highest at F100 which declined progressively with a decrease in fertigation level for all water qualities. However, these differences were narrow between GW and MW and moderate between CW and DSW. Therefore, in drip fertigated potatoes using saline or mixed water in a sandy loam soil, it is advocated to use 80% of recommended NPK without any loss in tuber yield and to reduce cost of cultivation & environmental pollution. •Four water qualities & 3 NPK-fertigation dose effects on potato were studied for 4 years.•Saline water yielded 21% (1st year) to 44% (4th year) lower than that with fresh water.•Desalinated water yielded 19% (1st year) to 75% (4th year) higher over saline water.•Blending of saline with fresh water yielded 9–37% higher than saline water irrigation.•Mixed water + 60% NPK gave higher tuber yield than that with saline water + 100% NPK.