An investigation was carried out at Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu during 2015 and 2016 to study the effect of pre- and post-emergence application of herbicides on weed dynamics, microbial population and yield of summer blackgram. Thirteen weed management treatments was comprised of imazethapyr 70 g/ha as pre and post-emergence, imazethapyr 80 g/ha as pre- and post-emergence, imazethapyr + imazamox 70     g/ha as pre- and post-emergence, imazethapyr + imazamox 80 g/ha as pre- and post-emergence, pendimethalin 1000 g/ha as pre-emergence, imazethapyr + pendimethalin 1000 g/ha as pre-emergence, two hoeings at 15 and 30 DAS, weedy check and weed free were assessed. The results revealed that a significant reduction in total weed density and total weed biomass was observed with two hoeings at 15 and 30 DAS, imazethapyr + pendimethalin 1000 g/ha as pre-emergence and imazethapyr + imazamox 80 g/ha as post-emergence. Aapplication of imazethapyr + pendimethalin 1000 g/ha as pre-emergence recorded the highest seed yield and B:C ratio. Initially, after the herbicides treatment (15 and 30 DAS) microbial counts were slightly less in pre-emergence, reaching a maximum at 30 DAS.