Background: Rice is India&rsquo;s staple food, but boro rice cultivation often uses intensive irrigation and fertilizers, leading to severe weed infestation and yield losses. To manage this, modern herbicides like Quinclorac 35% SC, a post-emergent, selective and systemic herbicide, has been identified, which effectively controls diverse weed flora. 
 
Methods: A field trial was conducted during the boro seasons of 2021-2022 and 2022-2023 at the Instructional Farm, Bidhan Chandra Krishi Viswavidyalaya, West Bengal, to assess the effectiveness of Quinclorac 35% SC at different doses for weed control in transplanted boro rice (variety IET 4786/Satabdi) compared to hand weeding and bispyribac sodium. Seven treatments were laid out in a randomized block design with three replications. Herbicides were applied at 15 DAT and crop growth, weed suppression, soil microbial populations and nutrient status were monitored before sowing and after harvest. 
 
Result: The results revealed that treatment T6&nbsp;(hand weeding twice at 20 and 40 DAT) achieved the highest weed control efficiency, followed by T5&nbsp;(Quinchlorac 35% SC @ 1400 ml ha-1) and T3&nbsp;(Quinchlorac 35% SC @ 700 ml ha-1). However, T6&nbsp;recorded a lower benefit-cost ratio due to higher labour costs. Although T5&nbsp;effectively suppressed weeds, it caused severe phytotoxicity. In contrast, T3&nbsp;provided strong weed control with minimal crop injury and the highest benefit-cost ratio, making it the most effective and economical herbicide treatment for managing weed flora in boro rice. 
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Assessing the Impact of Quinchlorac 35% SC on Weed Flora, Soil Nutrient ond Microbial Status in Transplanted Boro Rice (Oryza sativa L.)