Effectiveness of sulfentrazone 39.6% SC (w/w) as a pre-emergent herbicide against weeds in transplanted paddy under coastal conditions in Karnataka, India

The lowland rice ecosystem in coastal Karnataka is dealing with a variety of weed species, including both monocot and dicot weeds. A field experiment was conducted at the Zonal Agricultural & Horticultural Research Station in Brahmavar, Udupi, and Karnataka during the Kharif and Rabi seasons of 2020. The soil at the experimental site was sandy loamy with medium organic carbon (0.68%), available nitrogen (336 kg/ha), available phosphorus (23.64 kg/ha), and available potassium (107 kg/ha), along with acidic pH (5.10). The dominant weeds associated with transplanted rice during the Kharif and Rabi seasons included monocot weeds like Echinochloa crusgalli, Echinochloa colonum, Cyperus iria, and Cyperus difformis, as well as dicot weeds such as Ludwigia parviflora, Eclipta prostrate, Monochoria vaginalis, and Marsilea quadrifolia. The experiment included seven treatments, consisting of three doses of sulfentrazone 39.6% SC (w/w) at 250, 300, and 500 g/ha, two standard checks of Pretilachlor 50% EC at 500 g/ha, penoxasulam 0.97% + butachlor 38.8% SE at 820 g/ha, and hand weeding twice with weedy checks. The layout followed a randomized block design with three replications. Sulfentrazone 39.6% SC (w/w) at 300 g/ha was found to be effective in reducing the density of both monocot and dicot weeds at the 30th (5.3 & 3.1 g in Kharif, 4.5 & 1.5 g in Rabi), 45th (16.0 & 8.0 g in Kharif, 15.5 & 4.8 g in Rabi), and 60th (37.3 & 15.5 g in Kharif, 23.3 & 8.1 g in Rabi) days after transplanting, compared to the weedy check at the same intervals. The treatment also showed the highest weed control efficiency (WCE %).