Chlorophyll, Herbicide residue, Liquid chromatography, Onion, QuEChER, Tandem mass spectrometry, Weeds

Management of weeds is the major challenge to the success of onion. Chemical weed control has been intensively used to reinforce crop yield; however, even selective herbicides can potentially interfere with biochemical and physiological changes in onion. A field experiment was conducted to evaluate the efficacy of different herbicides pendimethalin, oxyfluorfen and quizalofop-ethyl individually and in combinations on weed control efficiency, yield attributes, changes in photosynthetic pigments, membrane injury and persistence of herbicides in onion. The combined application of oxyfluorfen and quizalofop-ethyl efficiently influenced the weed density and biomass causing higher yield and net returns. The application of oxyfluorfen recorded highest weed control efficiency, while a decline in photosynthetic pigments caused lesser yield. The results of QuEChER method of liquid chromatography tandem mass spectrometry (LC-MS/MS) revealed that herbicide residue did not find in both leaves and bulb in any treatment.