Assessing the impacts of tillage, cover crops, nitrification, and urease inhibitors on nitrous oxide emissions over winter and early spring

There are increasing demands to reduce greenhouse gas emissions from agricultural soils worldwide. A significant portion of these emissions occur in cold regions during soil's freezing and thawing. Focusing on over-winter cropland nitrous oxide (N2O) emissions, a review of 21 relevant peer-reviewed studies with a total of 88 comparisons was conducted to quantify the efficacy of field management practices (no-till, cover crops (CCs), nitrification, and urease inhibitors (NI + UI)) in reducing emissions. We also assessed these mitigation practices' efficacy across soil types and between cold humid and cold dry areas. The ratio of non-growing season emissions to full-year N2O emissions reported in the studies used in this review ranged between 5 and 91%. No-till significantly reduced N2O emissions by 28%, and this effect was more pronounced in drier climates. NI + UI also significantly reduced over-winter emissions by 23% compared to conventional fertilizers, and this effect was more evident in medium-textured soils than coarse soils. CCs showed an overall reduction potential of 18%; however, this effect was not significant. This review showed that under the CC practice, N2O emissions were reduced overall in humid climates but increased in drier climates, while no-till and NI + UI practices effectively reduced over-winter emissions in both dry and humid winter regions and all soil types.