Nitrogen nutrition effects on triticale photosynthesis and assimilate translocation under late-season water stress conditions

Abstract

In this study, photosynthesis and assimilate translocation and their contribution to improving grain yield and harvest index (HI) of triticale under different N sources and irrigation regimes in an arid climate were evaluated. There were two levels of water regimes: normal irrigation (IRN) and deficit irrigation (cutting irrigation after anthesis stage - IRD). Four N sources: 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. Results showed the highest net photosynthesis rate (Pn) was observed in Bio + N75 (24 and 20 µmol CO2 m−2 s−1 at the milking and soft dough stages, respectively) under IRN. The IRD decreased Pn in all N sources, however, the highest reduction was observed in N150 and the lowest in Bio and Bio + N75 treatments. Similar trends were observed in other photosynthetic traits and assimilate remobilization, except for the instantaneous water use efficiency (IWUE), which increased by IRD when bio-fertilizer was applied. The highest grain yield was found by N150 under IRN, which was not significantly different from Bio + N75 treatment. In contrast, application of Bio + N75 resulted in the highest grain yield compared to the other N sources under IRD. Overall, since the lowest reduction in photosynthetic traits, assimilate remobilization, and grain yield of triticale under IRD conditions occurred when bio-fertilizer was applied, this N fertilizer regime could be recommended for the arid areas where water shortage occurs frequently.