Methane and Nitrous Oxide Emissions From Organic and Conventional Dairy Systems.

Agriculture is responsible for roughly 25% of total anthropogenic emission of greenhouse gases (GHG) globally. Management practices vary across the industry and have large impacts on the emissions from agriculture. Impact of management practices and farming practice on GHG emissions is essential to determine the influence of agriculture on the atmosphere. Since agriculture is also more likely to release methane (CH₄) and nitrous oxide (N₂O) than carbon dioxide (CO₂) it is essential to reduce emissions from agriculture as this can greatly reduce global GHG emissions. Agricultural emissions of N₂O are estimated to account for 50-75% of the global N₂O budget.  However, most of these fluxes occur during soil freeze-thaw and wetting-drying cycles and are thus underestimated in most literature. On a farm scale these large fluxes of N₂O from soil “hot moments” can account for up to 60% of the total GHG emissions and thus it is essential to capture the full flux.  Enteric Fermentation and the manure excreted by the animals also represents a large flux of CH₄ from the agricultural sector.

 The University of New Hampshire Agriculture Experiment Station (NHAES) operates a Conventional and Organic dairy that allow for a unique comparison of management techniques. Emissions from housing, manure management, enteric fermentation, and soil “hot moment” fluxes (freeze-thaw and wetting-drying) at both UNH dairy farms were examined. The data was collected by a combination of static chamber measurements and SF₆ tracer tests operated at both farms. We measured trace gas fluxes that will help develop a farm scale GHG budget by looking at “hot spot” and “hot moment” GHG releases on both farms.