Decomposition of dung in grazed dairy farm systems is an important microbial ecosystem service to recycle nutrients. The decomposition rates of the dungs vary by farms as well as greenhouse gas emission rates during decomposition processes but factors controlling them are not fully known. This study aimed to understand the soil and dung properties that promote the decomposition rates of dungs and how those factors impact gas emissions. An incubation study was set-up using soils and dung sampled from six different grazed dairy farms. Their physicochemical properties were analyzed, DNA extracted, and sequenced looking at the microbial communities. Gas was measured for 24 days. On average, dung application increased the cumulative amount of gas emissions by 0.02%, 80%, and 71% in methane, nitrous oxide, and carbon dioxide respectively compared with the control without dung. Methane emission significantly correlated with nitrate amount R = 0.92, P = 0.009, while the total carbon also influenced the nitrous oxide emission R = −0.95, P = 0.011 among the farms. The microbial communities were influenced differently depending on the farm. Therefore, it can be suggested that dung decomposition differences with regards to each farm strongly depend on the key drivers controlling emissions.