Tillage System, Summerfallow, and Crop Type Influence Nitrous Oxide Emissions On a Udic Boroll On the Canadian Prairies.

Agricultural activities are an important source of anthropogenic nitrous oxide (N₂O) emissions. A better understanding of how crop management decisions such as tillage intensity, summerfallow and crop selection influence N₂O emissions is needed to refine national greenhouse gas inventories and design strategies to minimize emissions. We measured soil-emitted N₂O from a sustainable cropping study located near Three Hills, Alberta, Canada. Our intent was to quantify emissions from several crop rotations that are typical of the region and investigate possible interactions between rotation and tillage management. Non-flow through non-steady state flux chambers were employed through out the frost-free periods from May 2000 until May 2006. Measurements were taken from continuous spring wheat, spring wheat-summerfallow, and the spring wheat and pea phases of a canola-barley-pea-spring wheat rotation, each of which was maintained under no-till and tillage-based management.  Annual mean N₂O loss estimates ranged from less than 0.7 kg to greater than 3.6 kg N₂O-N ha^-1. Variability in the annual loss estimates was related to differences in the magnitude and pattern of precipitation during the study period as well as cropping practices. Emissions were consistently lower under no-till compared to the tillage-based management, and from plots cropped to field pea compared those seeded to spring wheat and receiving nitrogen fertilizer. Although highly variable, emissions from summerfallowed plots were comparable to emissions from plots seeded to spring wheat and receiving nitrogen fertilizer. This study brought better estimates of the mitigation potential of cultural practices on the Canadian prairies.