Effect of sequential application of herbicides for weed management in drill sown onion (Allium Cepa L.) Under Rainfed Condition

Field experiments were carried out during kharif seasons of 2011 and 2012 to study the effect of sequential application of herbicides for weed management in rainfed drill sown onion at Main Horticultural Research and Extension Centre, University of Horticultural Sciences, Bagalkot, Karnataka. Seventeen weed control treatments were tested in randomised block design replicated thrice. Application of pre emergence herbicides, either pendimethalin @ 1.0 kg ha⁻¹, butachlor @ 1.0 kg ha⁻¹ or oxyfluorfen @0.08 kg ha⁻¹ with post emergence herbicides either fenoxaprop-p-ethyl @ 75g ha⁻¹ or propaquizafop @ 100 g ha⁻¹ reduced the grass density (0.88 0.5m⁻²) at harvest. Among the herbicide treatments, application of oxyfluorfen @ 0.08 kg ha⁻¹followed by oxyfluorfen @ 0.25 kg ha⁻¹ showed significant reduction in broad leaved and total weed density. All the pre emergence herbicides recorded favorable weeds control at 7 and 14 days after sowing (DAS). Later on, at21 and 28 DAS, oxyfluorfen (@ 0.08 kg ha⁻¹) treated plots showed higherweed control rating than all other treatments except weed free check and farmer's practice. Pre-emergence spray of butachlor @ 1.0 kg ha⁻¹was toxic 14 and 21 days after spraying, while oxyfluorfen showed toxic symptoms, 7 and 14 days after post emergence spray. Sequential application of oxyfluorfen @ 0.08 kg ha⁻¹followed by oxyfluorfen @ 0.25 kg ha⁻¹at 30, 60, 90 DAS and at harvest recorded lower weed dry weight. Weed control Index (WCI) was highest at all the growth stages in weed free check, however, sequential application of oxyfluorfen @ 0.08 kg ha⁻¹followed byoxyfluorfen @ 0.25 kg ha⁻¹ recorded higher WCI at various growthstages. Italso recorded significantly higher bulb yield. The weed index was also lowest in this treatment.