Synthesizing the evidence of nitrous oxide mitigation practices in agroecosystems

Abstract

Nitrous oxide (N _2 O) emissions from agricultural soils are the main source of atmospheric N _2 O, a potent greenhouse gas and key ozone-depleting substance. Several agricultural practices with potential to mitigate N _2 O emissions have been tested worldwide. However, to guide policymaking for reducing N _2 O emissions from agricultural soils, it is necessary to better understand the overall performance and variability of mitigation practices and identify those requiring further investigation. We performed a systematic review and a second-order meta-analysis to assess the abatement efficiency of N _2 O mitigation practices from agricultural soils. We used 27 meta-analyses including 41 effect sizes based on 1119 primary studies. Technology-driven solutions (e.g. enhanced-efficiency fertilizers, drip irrigation, and biochar) and optimization of fertilizer rate have considerable mitigation potential. Agroecological mitigation practices (e.g. organic fertilizer and reduced tillage), while potentially contributing to soil quality and carbon storage, may enhance N _2 O emissions and only lead to reductions under certain pedoclimatic and farming conditions. Other mitigation practices (e.g. lime amendment or crop residue removal) led to marginal N _2 O decreases. Despite the variable mitigation potential, evidencing the context-dependency of N _2 O reductions and tradeoffs, several mitigation practices may maintain or increase crop production, representing relevant alternatives for policymaking to reduce greenhouse gas emissions and safeguard food security.

Keywords

• agricultural soils
• nitrous oxide
• greenhouse gas
• mitigation
• evidence synthesis
• meta-analysis