Effects of chemical and mechanical weed control strategies on bulb yield, physiological traits, and antioxidant enzyme activities in Persian shallot (Allium hirtifolium Boiss.)

A two-year field experiment (2021-2023) was conducted using a randomized complete block design to evaluate the effects of mechanical and chemical weed control strategies on weed suppression, yield, and physiological responses of Persian shallot (Allium hirtifolium Boiss.) under semi-arid conditions. Treatments included season-long hand weeding, post-emergence application of the commercial formulations of ioxynil (22% EC), oxyfluorfen (24% EC), and oxadiazon (25% EC), each applied at 2 L ha⁻¹ of formulated product, and an untreated control. Results showed that the untreated control had the highest weed biomass and the lowest bulb yield. Oxyfluorfen provided the most effective chemical control, reducing weed biomass by 54%. However, hand weeding resulted in superior crop performance, producing the highest leaf dry weight, leaf area index, and bulb yield. Herbicide treatments reduced growth-related traits and photosynthetic pigments, particularly under oxadiazon. Physiological analyses indicated that stress markers, including proline content and antioxidant enzyme activities (CAT and POD), were highest in the untreated control and herbicide-treated plants, while the lowest values were observed under hand weeding. In contrast, soluble sugars, relative water content, electrolyte leakage, and total phenolics were not significantly affected by treatments. Year effects were significant for several growth traits, but the interaction between year and treatment was tested and found to be non-significant for all measured traits. Overall, although oxyfluorfen was the most effective herbicide for weed suppression, hand weeding provided the best balance between yield and physiological stability. These findings highlight a trade-off between chemical weed control efficiency and crop physiological integrity in semi-arid production systems.