Agriculture can potentially contribute to Canada meeting its commitment to reduce net greenhouse gas (GHG) emissions under the Kyoto protocol. A representative crop - livestock feeding farm on the Canadian prairies is used to estimate the cost of net GHG abatement, taking into account CO2 equivalent emissions and carbon sequestration. Optimal cropping systems use direct seeding and continuous cropping, production systems that have lower net GHG emissions. Livestock feeding uses rations with high energy concentration (grain based) because they are more profitable and also produce less methane per animal than forage based diets. Reducing tillage is the least costly means of lowering net emissions ($20/t CO2 eq.), followed by reducing cattle feeding ($32/t CO2 eq.). If emission reductions are high or cattle numbers can not be reduced, cropping is altered to use very little nitrogen fertilizer ($272-567/t CO2 eq.), and cattle feeding is switched to a higher forage diet (up to $1500/t CO2 eq.). The high forage diet has lower emissions per capacity animal, but only because one-half the number of animals can be finished with the same facility capacity. A regional analyses of aggregate emissions will need to incorporate the heterogeneity of farms and soil carbon levels that exist.