Direct and indirect greenhouse gas emissions under conventional, organic, and conservation agriculture

Farm activities contribute to approximately one-third of Greenhouse Gas (GHG) emissions. Most of the GHG in the atmosphere comes from carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The main objective of this research is to investigate direct and indirect GHG emission in five different agroecosystems, contrasted by tillage agricultural, farm practices (oat and maize-fava and vetch).CO2, N2O y CH4 concentrations were measured using two closed static chambers. Total biomass and production costs were determined. Indirect emissions were calculated from fuel used in producing and packing of synthetic fertilizers and herbicide, and sheep manure mineralization. The results showed that CO2 was the gas that most contributes to GHG emissions followed by the CH4 and NO2. The agrosystem with reduce tillage and synthetic inputs had the highest emissions (979 CO2 eq kg ha- 1). Agrosystems using synthetic inputs (conventional and reduce tillage) showed higher indirect emissions (958 and 856 CO2 eq kg ha � 1 respectively). Maize in monoculture produced more than the systems with rotation or intercropping. Reduced tillage with intercropping and organic inputs was the most expensive to produce but had the least gas emission per dollar invested and per kilogram of biomass produced while conventional tillage agrosystems with organic or synthetic inputs stored little carbon in the soil, produced less biomass per unit area and presented higher CO2 eq emissions per unit of biomass.