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 (IR_N) and deficit irrigation (cutting irrigation after anthesis stage - IR_D). 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 (P_n) was observed in Bio + N₇₅ (24 and 20 µmol CO₂ m⁻² s⁻¹ at the milking and soft dough stages, respectively) under IR_N. The IR_D decreased P_n 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 IR_D when bio-fertilizer was applied. The highest grain yield was found by N₁₅₀ under IR_N, 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 IR_D. Overall, since the lowest reduction in photosynthetic traits, assimilate remobilization, and grain yield of triticale under IR_D conditions occurred when bio-fertilizer was applied, this N fertilizer regime could be recommended for the arid areas where water shortage occurs frequently.

Keywords:

• deficit irrigation
• instantaneous water use efficiency
• net photosynthesis rate

Disclosure statement

No conflict of interest was reported by the authors.