Replacing oxen with tractors: Reduction or shift in direct on-farm greenhouse gas emissions?

Cattle provide over 60% of the draught power in African mixed crop–livestock (MCL) systems, but also emit more than 60% of livestock-sector greenhouse gases (GHG) from the region. This study estimated and compared GHG emissions from MCL farms to assess how replacing draught oxen with tractors affects direct total on-farm emissions. Forty-eight farmers in Arsi Zone, Ethiopia, were purposively selected and interviewed on their production practices pre- and post-adoption (between 2002 and 2022) of tractor services. Employing a semi-structured questionnaire, we collected data on cattle herd dynamics and husbandry, use of animals and tractors for cropping activities, as well as crop production practices and parameters. On-farm GHG emissions were estimated using the IPCC Tier 2 method. On average, herd size decreased by 59.5%, whereas the land cropped increased by 52.3% between pre- and post- adoption of tractor services. The reduced herd size resulted in a decrease from 528.7 to 223.7 t CO 2 equivalents (CO 2 e) in livestock GHG emissions, whereas emissions from cropping activities increased from 12.2 to 37.3 t CO 2 e post-adoption of tractor services. Adopting tractors for on-farm activities decreased direct on-farm total GHG emissions by 51.7% and reduced emission intensity from 0.72 to 0.43 kg CO 2 e per Mcal produced. These findings should be interpreted with caution because estimates of pre-adoption production practices rely on farmer recall over long time periods. However, the reduced need for draught oxen led to smaller cattle herds and lower production of animal-source foods, which may have unintended consequences for the nutritional security of rural populations.