Alberta contributed the most to Canada's NH3 emissions in 2013, with 29% (142 kt) of the national total (492 kt). Saskatchewan ranked second, with 21% (102 kt). Ontario and Quebec emitted the next highest proportions, with 18% and 14% (89 and 69 kt), respectively. For all provinces, livestock farms and the application of fertilizers were the most important sources of NH3 emissions. Almost all of the increase in emissions between 1990 and 2013 took place in Manitoba, Saskatchewan and Alberta.