Nitrogen Source and Deficit Irrigation Influence on Yield and Nitrogen Translocation of Triticale in an Arid Mediterranean Agroecosystem

To identify the important features of triticale that contribute to improving grain and biomass Water Use Efficiency (WUEg and WUEb, respectively), grain yield, and Nitrogen (N) remobilization, a 2-year side-by-side experiment was carried out on triticale with different nitrogen sources and water regimes, in a typical Mediterranean environment of Iran. There were two levels of water regimes: Normal Irrigation (IRN) and irrigation cut off after anthesis stage (IRMD). Rain-fed treatment (IR0) was included in the second year. Four N sources including Azospirillum brasilense (Bio), Azospirillum brasilense+75 kg N ha-1 as urea (Bio+N75), 150 kg N ha-1 as urea (N150), and control unfertilized (N0) plots were used. This study showed that the highest grain yield (6,258 kg ha-1) was achieved by chemical N fertilizer application (N150) under IRN. In contrast, the application of Bio+N75 resulted in the highest grain yield as compared with the other N sources under IRMD (4,409 kg ha-1) and IR0 (2,960 kg ha-1) conditions. Water stress significantly increased WUEb at all N sources. However, WUEg slightly increased by IRMD and then sharply decreased by IR0 in all N sources, except N150 plots, where WUEg drastically decreased by water stress imposed by IRMD and IR0. The Bio+N75 treatment had the highest N remobilization. Although N remobilization was not affected by IRMD in dryer year, it increased by IRMD (8.4%) in the relatively wet year. Totally, for a more sustainable farming system in arid Mediterranean conditions, integration of biofertilizer and chemical N fertilizer could be successfully used for increasing grain yield, WUE, and N remobilization of triticale, especially under deficit irrigation regimes.