Two field experiments were conducted to investigate the effects of three drip irrigation regimes (G1: 120% crop evapotranspiration (ETc), G2: 100% ETc, and G3: 80% ETc) and four nitrogen (N) source treatments (S0: non-fertilized; S1: urea, S2: ammonium nitrate, and S3: ammonium sulfate on water consumption use, water utilization efficiency, chlorophyll, yield and tubers quality of potato (Solanum tuberosum L.; cv Diamond) under a drip irrigation system during two successive winter seasons (2015/16 and 2016/17)). Nitrogen fertilization was applied at 380 kg ha−1 as standard application for potato in the investigated area. The highest tubers yield was obtained from potato grown with G1 S2 (65.8 Mg ha−1), G1 S3 (63.6 Mg ha−1), G2 S2 (64.1 Mg ha−1), and G2 S3 (62.4 Mg ha−1), while the lowest tubers yield was obtained from potato grown with G3 S0 (10.1 Mg ha−1) and G2S0 (17.4 Mg ha−1). Different treatments of N source resulted in a significant increase for water use efficiency (WUtE) compared with unfertilized treatment. For the interaction effect, the highest WUtE was obtained from potato grown with G3 S2 (18.1 kg m−3), followed by G3 S3 (17.6 kg m−3), while the lowest WUtE was obtained from plants grown with G3S0 (3.0 kg m−3). However, the highest chlorophyll content was obtained from plants grown with G1 and any N source, followed by G2S1-3, while the lowest chlorophyll content was obtained from those grown with G3S0. The highest N, S, protein, and P contents in tubers were obtained from plants grown with G3S3, G3S2, and G2S2, while the highest K content in tubers was obtained from plants grown with G1S1 and G1S2. In concussion, the integrative effects of G1 or G2 with S2 or S3 is recommended for high productivity, while the integrative effects of G3S3 and G3S2 are recommended for high quality tubers.
