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 (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.