Methodology for N ₂ O Emission Reductions through Fertilizer Rate Reduction

The American Carbon Registry (ACR) in 2010 approved a Methodology for N ₂ O Emissions Reductions through Changes in Fertilizer Management , which was developed by Winrock International and Applied Geosolutions and approved through ACR’s public consultation and scientific peer review process. The methodology uses the Denitrification-Decomposition (DNDC) biogeochemical process model to quantify direct and indirect N ₂ O emissions in the baseline (pre-project) fertilizer management scenario vs. a project to modify fertilizer type, timing, placement or rate, or to use timed-release fertilizers, nitrification inhibitors or other advanced fertilizer technologies. The methodology offers full flexibility to farmers on which practices to implement, and can be used on any crop and location for which DNDC has been properly calibrated and validated.

ACR now posts for public comment a second methodology, developed by Michigan State University with support from the Electric Power Research Institute, entitled  Quantifying Nitrous Oxide (N ₂ O) Emissions Reductions in Agricultural Crops through Nitrogen (N) Fertilizer Rate Reduction .

Under this methodology, practice changes are limited to on-farm reductions in Nitrogen fertilizer rate – i.e. reducing the quantity of N-containing synthetic and organic fertilizers applied and thus reducing net N ₂ O emissions from annual or perennial cropping systems. While more limited in scope, the methodology offers a simplified accounting approach for projects in continuous corn and corn rotation systems in the U.S. North Central Region (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota and Wisconsin), as well as default factors applicable to U.S. cropland outside the North Central Region and cropland outside the U.S.

Two peer-reviewed references are provided along with the methodology:

·         Millar, N., Robertson, G.P., Grace, P.R., Gehl, R.J., and Hoben, J.P. (2010). Nitrogen Fertilizer Management for Nitrous Oxide (N ₂ O) Mitigation in Intensive Corn (Maize) Production: An Emissions Reduction Protocol for US Midwest Agriculture. Mitigation and Adaptation Strategies for Global Change 15:185–204.

·         Hoben JP, Gehl RJ, Millar N, Grace PR, Robertson GP (2011). Non-linear nitrous oxide (N ₂ O) response to nitrogen fertilizer in on-farm corn crops of the US Midwest. Global Change Biology 17:1140–1152. 

Projects using this methodology must comply with all requirements of the ACR Standard , submit a GHG Project Plan for certification by ACR, and secure independent validation and verification by an ACR-approved third-party verifier.

Please send all comments by close of business June 17, 2011 to publiccomment@americancarbonregistry.org referencing “Michigan State fertilizer methodology.”