A field experiment was conducted during Kharif (rainy season) 2019 to study the weed management efficacy of pre-emergence application (PE) of diclosulam, pendimethalin + imazethapyr and pendimethalin at 20, 1000 and 1000 g/ha, respectively and post-emergence application (PoE) of propaquizafop + imazethapyr, sodium acifluorfen + clodinafop propargyl and imazethapyr at 127, 180 and 75 g/ha, respectively and compared with hand weeding (HW) twice and unweeded check. The diclosulam 20 g/ha PE followed by (fb) HW resulted in reduced weed density and biomass and recorded higher weed control efficiency at 30 and 60 days after seeding (DAS). The next best treatment in suppressing weed growth was pendimethalin + imazethapyr 1000 g/ha PE fb HW. Among the post-emergence herbicides, propaquizafop + imazethapyr 127 g/ha was superior in reducing weed density and biomass. Diclosulam 20 g/ha PE and imazethapyr 75          g/ha PoE showed phytotoxicity rating of ‘2’ and ‘1’, respectively. Initially, blackgram population was reduced by 15.83% due to diclosulam phytotoxicity. Pendimethalin + imazethapyr 1000 g/ha PE fb HW resulted in higher plant height, dry matter production, yield components and seed yield of blackgram and it was comparable with HW twice and diclosulam 20 g/ha PE fb HW. The highest benefit-cost ratio was obtained with pendimethalin + imazethapyr 1000 g/ha PE.