A field experiment was conducted during 2013-14 and 2014-15 at Jabalpur to assess the effect of conservation tillage and weed management practices on the total bacteria, fungi, actinomycetes and dehydrogenase activity under soybean - wheat cropping system in vertisols. The results of the investigation revealed that tillage systems to influence significantly the microbial population. Among the tillage treatments, zero tillage + crop residue (soybean) fb zero tillage + crop residue (wheat) had higher bacterial, fungal population and dehydrogenase activity during both the seasons. But actinomycetes population was higher in zero tillage + crop residue (soybean) fb zero tillage (wheat) during both seasons. However, there was no adverse effects of herbicides use in soybean-wheat cropping system on microbial population during both crop seasons except Rabi season 2014 -15 in which bacterial population was reduced by 27.3% when mesosulfuron (12 g/ha) + iodosulfuron (2.4 g/ha) mixture was applied in wheat following application of pendimethalin (750 g/ha) fb imazethapyr (100 g/ha) in preceding  soybean crop.