Interaction Effects of Nitrogen Source and Irrigation Regime on Tuber Quality, Yield, and Water Use Efficiency of Solanum tuberosum L.

Two field experiments were conducted to investigate the effects of three drip irrigation regimes (G(1): 120% crop evapotranspiration (ETc), G(2): 100% ETc, and G(3): 80% ETc) and four nitrogen (N) source treatments (S(0): non-fertilized; S(1): urea, S(2): ammonium nitrate, and S(3): 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 G(1) S(2) (65.8 Mg ha(−1)), G(1) S(3) (63.6 Mg ha(−1)), G(2) S(2) (64.1 Mg ha(−1)), and G(2) S(3) (62.4 Mg ha(−1)), while the lowest tubers yield was obtained from potato grown with G(3) S(0) (10.1 Mg ha(−1)) and G(2)S(0) (17.4 Mg ha(−1)). Different treatments of N source resulted in a significant increase for water use efficiency (WU(t)E) compared with unfertilized treatment. For the interaction effect, the highest WU(t)E was obtained from potato grown with G(3) S(2) (18.1 kg m(−3)), followed by G(3) S(3) (17.6 kg m(−3)), while the lowest WU(t)E was obtained from plants grown with G(3)S(0) (3.0 kg m(−3)). However, the highest chlorophyll content was obtained from plants grown with G1 and any N source, followed by G(2)S(1-3), while the lowest chlorophyll content was obtained from those grown with G(3)S(0). The highest N, S, protein, and P contents in tubers were obtained from plants grown with G(3)S(3,) G(3)S(2), and G(2)S(2), while the highest K content in tubers was obtained from plants grown with G(1)S(1) and G(1)S(2). In concussion, the integrative effects of G(1) or G(2) with S(2) or S(3) is recommended for high productivity, while the integrative effects of G(3)S(3) and G(3)S(2) are recommended for high quality tubers.