Water use efficiency and grain yield of water stressed-field grown triticale as affected by combined application of biochar and biological fertilizer

Water stress poses a significant constraint on crop productivity in arid regions. A 2-year field experiment was conducted using a split-factorial layout within a randomized complete block (RCB) design to determine whether the combination of Azospirillum brasilense and Pseudomonas fluorescens (plant growth-promoting rhizobacteria [PGPRs]) with organic matter (OM) can mitigate the negative impacts of water stress on the grain yield of triticale (×Triticosecale Wittmack), as well as on water use efficiency for grain (WUEg) and biomass (WUEb). Irrigation treatments, including full irrigation (IRN) and post-milking deficit irrigation (IRD), were assigned to the main plots. Subplots were allocated to different OM sources (no OM, wheat residue, and its biochar) and nitrogen-phosphorus (N-P) sources, viz: chemical N-P fertilizer and integrated N-P fertilizer (50% chemical N-P fertilizer combined with PGPRs). Results indicated that IRD led to a significant decrease in grain yield (60.1%) and, ultimately, WUEg (43.4%) without OM application. However, using biochar resulted in the lowest reductions in these traits (41.1% and 14.6%, respectively) compared to the other OM treatments. The application of integrated N-P fertilizer resulted in an increase in grain yield, WUEg, and WUEb, across all types of OM compared to chemical N-P fertilizer. Notably, the most substantial improvements were observed with the application of biochar, which enhanced grain yield, WUEg, and WUEb by 24.5%, 27.7%, and 18.6%, respectively. Additionally, the application of integrated N-P fertilizer mitigated the decline in average grain weight, a crucial factor influencing the grain yield of triticale, under post-milking water stress conditions. Finally, integrated N-P fertilizer in conjunction with biochar is recommended for arid regions facing irrigation water restrictions during the grain-filling stage of triticale.