Are Agricultural Greenhouse Gas Mitigation Activities Ready for Protocols or Programs? An Assessment of Potential and the Knowledge Gaps.

Agricultural land management practices within the United States have significant potential to mitigate greenhouse gases (GHGs) in voluntary market or regulatory contexts – by sequestering soil carbon or reducing N₂O or CH₄ emissions. Before these practices can be utilized in active protocols or within a regulatory or farm bill framework, we need confidence in our ability to determine their potential impact on GHGs. We develop a side-by-side comparison of biophysical and economic potential and implementation readiness for a suite of agricultural GHG mitigation practices, with an extensive literature review and economic land-use modeling. We also consider scientific certainty, environmental and social co-effects, regional specificity, and potential barriers. An advisory board and expert consultation were essential contributors in determining the list of possible activities, the scientific certainty of GHG impact, and regional implications.

Biophysical GHG mitigation potential from agricultural land management activities could reach more than 500 Mt CO₂e/yr in the U.S. (7.1% of annual emissions). Up to 75% of the total potential comes from soil C sequestration. Economic potential is lower, given necessary resources to incentivize on-farm adaptations, but lower cost activities such as no-till, fertilizer N management, and cover crops show promise for near-term implementation in certain regions. Scientific uncertainty or the need for more research limit no-till and rice water management in some areas; and technical or other barriers need to be addressed before biochar, advanced crop breeding, and agroforestry can be widely embraced for GHG mitigation. Significant gaps in the current research and knowledge base exist with respect to interactions between tillage and N₂O emissions, and with fertilizer application timing impacts on N₂O emissions.

This synthesis and translation of state of the art scientific knowledge is intended to aid implementation of GHG mitigation programs as well as best management practices for other measures of sustainability.