Weed-management indices and short-term crop phytotoxicity under herbicide programmes in transplanted rice (Oryza sativa L.)

Weed interference remains a major constraint to rice productivity, particularly under diverse weed flora comprising grasses, sedges, and broad-leaved species. A field experiment was conducted during the kharif season of 2024 at the Agronomy Main Research Farm, Odisha University of Agriculture and Technology (OUAT), Bhubaneswar, Odisha, India, to evaluate different weed management programs based on weed flora composition, weed management efficiency indices, and herbicide-induced phytotoxicity. Six major weed species were recorded, comprising two grasses, one sedge, and three broad-leaved weeds. Broad-leaved weeds constituted the dominant group (47%), followed by grasses (36%) and sedges (17%). Weed management indices varied among treatments at 30 and 60 days after transplanting (DAT), indicating differential responses of the crop–weed system to the evaluated herbicide programs. Among the treatments, T3 (pyrazosulfuron-ethyl applied pre-emergence, followed by florpyrauxifen-benzyl + cyhalofop-butyl post-emergence) recorded the lowest weed index (0.00%) and the highest reported crop resistance index (11.17 and 15.27), weed management index (0.60 and 0.59), and herbicide efficiency index (4.16 and 4.72) at 30 and 60 DAT, respectively. Phytotoxicity assessments revealed slight, transient injury in T1, T2, T3, and T6, with scores not exceeding 1 and no visible injury by 12 days after herbicide application. No visible phytotoxic symptoms were observed in T4, T5, or T7, whereas T8 received no herbicide treatment. The findings highlight the importance of evaluating weed management indices alongside crop safety when comparing herbicide programs in transplanted rice. Under the conditions of this single-season field experiment at OUAT, Bhubaneswar, T3 appeared promising based on the reported indices, although verification of index calculations and supporting yield and economic data is necessary before making broader recommendations.