Water scarcity and the excessive use of chemical fertilizers are the key destructive factors that negatively affect the quantity and quality of crops. Chitosan nanoparticles (Cs-NPs) and biofertilizers ( BFS) have been shown to alleviate the effects of drought stress on plants, but information is scant on the effect of their co-addition on minimizing the effects of drought stress on plants. This study investigated the effect of the combined application of nanoparticles and biofertilizer to improve drought tolerance in camelina (Camelina sativa L.). The experimental design was constituted by a split plot arranged in a randomized complete block design (RCBD) with 16 treatments and three replications. The main factor was the cultivation in rainfed and supplementary irrigation conditions. Subplots were assigned to eight fertilizer sources, including no fertilizer (control), complete chemical fertilizer (CHF), biofertilizer ( BFS), chitosan nanoparticles ( CS-NPS), 50% CHF+ BFS, 50% CHF+ CS- NPS, BFS+ CS- NPS, and CS- NPS+ BFs + 50% CHF. The results showed that the highest antioxidant enzyme activity, total soluble proteins, phenolics, and flavonoid content were recorded by the treatment of CS- NPS+ BFS+ 50% CHF in rainfed conditions. The highest photosynthesis pigments and total soluble sugar content were observed in supplementary irrigation conditions along with CS- NPS+ BFS+ 50% CHF. The application of CS- NPS+ BFS+ 50% CHF in rainfed and supplementary irrigation conditions increased camelina grain yield by 53.76 and 78.95% versus the control plants, respectively. The CS- NPS+ BFS+ 50% CHF treatment mitigated the adverse effects of the limited water supply on the physiological, biochemical, and yield traits of camelina. These findings revealed that the combined application of CS- NPS+ BFS+ 50% CHF can be used as an alternative to chemical fertilizers to improve crop production sustainabilit
