Public Comment on USDA Greenhouse Gas Monitoring Strategy
The USDA recently requested public input for a draft Federal Strategy to Advance Greenhouse Gas Measurement and Monitoring for the Agriculture and Forest Sectors developed by the Greenhouse Gas Interagency IWG (GHG IWG). The proposed strategy “outlines a framework for an integrated U.S. Government (USG) approach to improving and advancing measurement, monitoring, reporting and verification (MMRV) of GHG fluxes from agriculture and forestry.” Because the soil microbiome plays a significant role in GHG emissions in agriculture, and because we have the means to improve microbiome monitoring, Trace Genomics issued a public comment. The full text is below and may also be accessed here.
The Federal Strategy to Advance Greenhouse Gas Measurement and Monitoring for the Agriculture and Forest Sectors developed by the GHG IWG acknowledges on page 1 that “net agricultural emissions now represent roughly 10 percent of U.S. GHG emissions”. According to the EPA, “Management of agricultural soils accounts for just over half of the greenhouse gas emissions from the Agriculture sector” (1). In order to have the most holistic understanding of soil GHG emissions, the IWG should consider soil tests that analyze the soil microbiome in conjunction with traditional soil chemistry and carbon measurements.
Soil microbes are known to produce the greenhouse gasses methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) (2). Considering the difficulty of measuring these gasses directly on a fine scale (3), microbiome analysis could be incorporated into monitoring plans for better geospatial understanding and management of GHG emissions. Metagenomics (sequencing all DNA in a sample) is a scalable, high-throughput, and rapid tool that can be used to analyze the species composition as well as the biological functional capacity of a soil sample (4). By examining the DNA, different genetic pathways can be measured, including those that impact production of GHG such as methanogenesis, ammonia oxidation, nitrification, denitrification, and nitrate reduction.
Access to soil microbiome data has collateral benefits to producers and landowners. In addition to data on their overall soil health and potential for GHG emissions, metagenomics provides a comprehensive test for soil-borne pathogens (5). Unlike targeted assays that search for a single gene or pathogen, metagenomics has the capacity to use one test for any pathogen with a reference genome. Data on functional genes (such as those responsible for N2O production) are not only beneficial for GHG monitoring, but they can also be used by growers and agronomists when creating a fertility management plan. By optimizing nitrogen fertilizer input alongside other management products like nitrogen stabilizers, growers can reduce N2O emissions as well as nitrogen leaching and runoff into waterways. Similarly, genetic pathways impacting phosphorus cycling can be measured and used to optimize phosphorus inputs.
Additional metagenomics-based studies would help to build a more complete understanding of GHG emissions and help to develop emission models based on microbial functional profiles, environmental factors, cropping systems and management practices, soil chemistry, and agricultural inputs. Taken together, these models can help to better identify and quantify the source and sinks for GHG in croplands.
Growers have been increasingly turning to regenerative agriculture (RegenAg) practices such as reduced tillage and cover cropping to reduce their carbon footprint and improve soil health, however there are technical and institutional barriers to adoption of these practices (6). Recently, metagenomics has been incorporated into soil health evaluations and used to monitor the effectiveness of RegenAg practices. A proponent of RegenAg, the Soil Health Institute (SHI) is a nonprofit organization that brings together academic, industry, and government researchers in a cross-discipline effort to understand soil health (7). The IWG should utilize the network already in place by the SHI to plan and implement the proposed Strategy for GHG monitoring and emissions.
Trace Genomics performs comprehensive soil testing by analyzing soil biology, chemistry, and carbon. Since 2015, Trace has amassed a database of soil samples covering a wide geographical area and developed tools to predict the potential for GHG emission from microbial functional profiles. Many of these samples had soil carbon analyzed and could be incorporated into a soil carbon monitoring network. Moving forward, soil samples analyzed using metagenomics can and should be incorporated into GHG emission monitoring strategies.
Moving forward, the IWG should address and work to overcome barriers to adopt RegenAg practices. As part of the proposed Strategy, education programs and other forms of encouragement (including financial support) should be implemented to increase availability of comprehensive soil tests that include microbiome analysis. With increased accessibility, growers can use metagenomics to evaluate the effectiveness of RegenAg, and the potential for availability of the data to the IWG can inform GHG emissions from agricultural soils.
You may browse all posted comments issued in response to this request here.
References
- https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions
- https://journals.asm.org/doi/10.1128/mbio.00800-22
- https://link.springer.com/chapter/10.1007/978-3-030-55396-8_2
- https://www.soilsa.com/pdf-163080-92536?filename=Metagenomics%20approaches.pdf
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9280627/
- https://www.mdpi.com/2071-1050/15/3/2338
- https://soilhealthinstitute.org/about-us/vision-values/
