Nitrogen and water use efficiencies and yield response of barley cultivars under different irrigation and nitrogen regimes in a semi-arid Mediterranean climate

Experiments were conducted to determine barley cultivars (Yousefsix-rowed and Nimrouztwo-rowed) response to different water and nitrogen (N) regimes at Fars Agricultural Research Center using split-split-plot design. There were three levels of water regimes (full-irrigation (I100), 75% and 50% of I100: I75 and I50, respectively) in 2010. Rainfed treatment (I0) was included in 2011. Three N levels (0, 60 and 120 kg ha−1) were used. Grain and biomass water use efficiencies (WUEg and WUEb, respectively) were positively affected by N supply. The I75 improved WUEg and WUEb by 17% and 20% as compared to I100, respectively. Two-rowed cultivar showed higher WUEg and WUEb than six-rowed. Nitrogen use efficiency (NUE) was negatively affected by water stress and N fertilization. The highest grain yield was achieved by 120 and 60 kg N ha−1 under I100 and drought stress conditions, respectively. Two-rowed cultivar showed significantly higher NUE and grain yield than six-rowed cultivar under I50 and I0; by contrast, si...