Effects of irrigation water quality and NPK-fertigation levels on plant growth, yield and tuber size of potatoes in a sandy loam alluvial soil of semi-arid region of Indian Punjab

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.