Effects of Drought Stress on the Quantitative and Qualitative Yield of Forage Faba Bean Varieties (Vicia faba L.)

Faba bean (Vicia faba L.) is important source of food and feed worldwide and provides a range of advantages in crop rotations. However, faba bean is susceptible to water stress, which limits its yield potential in Water deficit coditions. This study aimed to evaluate the effects of drought stress on the quantitative and qualitative yield of forage faba bean genotypes in autumn cultivation, which is considered a strategy for adapting to drought and climate change. This study was conducted in Gorgan Agricultural Research Station, Iran over two crop years (2022-2023 and 2023-2024). A randomized complete block design with three replications was employed to investigate the effects of drought stress on both the quantitative and qualitative forage yield of new faba bean varieties under autumn cultivation. Accordingly, nine new faba bean lines along with two control varieties of Mehta (low tannin) and Shadan (high tannin) were compared and evaluated under two environmental conditions: drought stress after flowering and normal irrigation. The combined analysis of variance indicated significant interaction effects between treatments and the measured traits. Specifically, the interaction between year and environment in both the optimal irrigation and drought stress conditions revealed that the highest fresh forage yields (37294 kg/ha and 18382 kg/ha, respectively) and dry forage yields (5948 kg/ha and 5523 kg/ha) were observed under normal irrigation and drought stress environments, respectively. The interaction between environment and variety, as well as the triple interaction of environment × variety × year, demonstrated that the WRB1-5 genotype, Shadan variety, and BPL4104 genotype yielded the highest fresh and dry forage yields in both environments. In terms of forage quality, the S2008-0330 genotype had the highest percentage of non-acid detergent insoluble fiber (NDF) (33.97%) under optimal irrigation, while the FLIP03-07FB genotype exhibited the highest NDF percentage (16.15%) under drought stress. The results indicate that drought stress after the flowering stage reduced both fresh and dry forage yields and increased ADF, CF, and NDF values across all varieties. However, the BPL4104 and WRB1-5 genotypes consistently outperformed other genotypes in both environments, suggesting that these genotypes are more resilient to drought stress while maintaining higher forage yields. Therefore, they could be considered potential candidates for cultivation in drought-prone areas.