Bio-efficacy of fomesafen plus fluazifop-p-butyl mixture against weeds and its effect on productivity and profitability of soybean (Glycine max) in Central India

Grassy and broadleaf weeds are simultaneously growing in soybean (Glycine max L.) crop and there is a lack of herbicides to control all types of weeds in a soybean crop. Thus, a field experiment was conducted during rainy (kharif) seasons of 2017 and 2018 to evaluate efficacy of fomesafen + fluazifop-p-butyl mixture against weeds and consequent improvement in productivity of soybean. Bio-efficacy was evaluated with 10 weed control treatments comprising of 4-doses of fomesafen + fluazifop-p-butyl mixture (90+90, 110+110, 130+130 and 220+220 g/ha), alone application of imazethapyr (100 g/ha), market check - fomesafen + fluazifop-p-butyl (110 + 110 g/ha), combined application of imazethapyr + imazamox (35 + 35 g/ha) as early post-emergence, hand weeding twice at 15 and 30 DAS, weedfree and weedy-check, were laid-out in a randomized complete block design with three replications. Application of premix fluazifop-p-butyl + fomesafen (130+130 g/ha) as early-post-emergence resulted in lower density, dry weight of all individual weeds with 99.2% weed control efficiency (WCE) and higher value of yield parameters and yield (2.01 t/ha) of soybean which was statistically at par with weed-free plots (2.04 t/ha). The higher dose of fomesafen + fluazifop-p-butyl (220+220 g/ha) was found effective against weeds but caused phytotoxicity to soybean crop and reduced seed yield marginally (1.98 t/ha). The fomesafen residues up to 130 g/ha dose were found below the detectable limit in the soil with zero per cent persistence at harvest. However, the highest dose of fomesafen (220 g/ha) resulted in residues in soil (0.016 mu g/g) with 4.44% persistence and half-life of 13 days. These results suggested that premix fomesafen + fluazifop-p-butyl at 130+130 g/ha as early-post-emergence can be safe for the application in soybean crop.