Dairy cattle slurry tanks could represent significant sources of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) to the atmosphere. To monitor greenhouse gas (GHG) emitted during storage, a new method based on tracer gas ratios was developed. For this purpose, a controlled quantity of sulphur hexafluoride (SF6, tracer gas) was continuously released above the storage tank to supplement the GHG emissions. The ratio between GHG and SF6 was calculated from data measured using gas chromatography units. These systems allowed continuous monitoring of SF6, CH4, N2O and CO2 concentrations in the upwind and downwind air from the storage tank during a full year period. The sampling systems were concurrently installed in an organic and a conventional cattle farm. Dairy cow slurry production and chemical characteristics were also monitored. For the conventional farm, methane emissions rates were comprised between 0 to 1023 g.C-CH4.m-3.d-1 with an average of 35 g.C-CH4.m-3.d-1. The emission rates varied from 0 and 384 g.C-CH4.m-3.d-1 -1 for the organic farm with an average of 26 g.C-CH4.m-3.d-1. In both farms, no emissions of nitrous oxide were measured attributed to storage conditions. For carbon dioxide, no emissions were recorded because the emission rate was not high enough to increase the background atmospheric concentration.