Progress in Applying a Multi-Model Ensemble Approach to Soil Carbon

By David I Gustafson, Adjunct Research Faculty at Washington State University

Flowering potato crop, with center pivot across the background
Potatoes are an important crop in the Pacific Northwest, that could benefit from more accurate estimates of carbon sequestration under different practices. Photo: WSDA under CC BY-NC 2.0.

When it comes to climate adaptation and mitigation opportunities in agriculture, few (if any) are of greater importance than practices that sequester more soil carbon, which can directly reduce the heat-trapping effects of atmospheric CO2. Boosting soil carbon also has multiple direct benefits for growers, such as increasing yield potential and resilience to both drought and heavy rainstorms.

This is a global challenge, including all producers across the Pacific Northwest (PNW). Its sheer size and scope mandates coordinated action across multiple sectors, including grower groups, the research community, industry, and government scientists. I serve on two such multi-sector groups: Conservation Technology Information Center (CTIC) and Field to Market.

Formed in 1982, CTIC is a membership-based non-profit with a mission to accelerate adoption of conservation practices like no-till and cover crops, whose climate benefits are now evident. CTIC leads partnerships with farmers, universities, government and business on projects that explore and champion conservation agriculture, including practices that help sequester soil carbon.

Field to Market is also a membership-based non-profit, but is younger, having been launched in 2013. It convenes diverse stakeholders to support multi-sector collaboration, while providing useful measurement tools and educational resources for growers and the value chain to track and create opportunities to improve the resilience of ecosystems and enhance farmer livelihoods. Field to Market focuses on row crops, including potatoes and wheat, obviously of keen interest in the PNW. Field to Market collects farmer data through its Fieldprint® Platform, used on more than 5 million acres nationwide.

These two groups have joined forces on the new workgroup I introduced in an article last November. We are pursuing a more rigorous and reliable way to quantify and estimate how much carbon is sequestered in agricultural soils using different practices under different conditions. If we are successful, our approach will ultimately result in greater accuracy and tighter confidence intervals on carbon sequestration estimates, and higher payments for farmers, ranchers, and other producers for their efforts to sequester that carbon in soils. There is a close analogy between the complexities of modeling soil carbon and forecasting the weather. It turns out that ensemble approaches are the best in both cases, which is why our workgroup is pursuing a multi-model ensemble (MME) approach to soil carbon.

The workgroup is co-led by myself and Paul Hishmeh (Field to Market). Core team members include Jeff Lail (Syngenta), Ross Bricklemyer (Bayer), and Ellen Herbert (Ducks Unlimited). Our primary deliverable is an API (Application Programming Interface – basically, an online tool) that is free and will allow any interested party to deploy the MME to more accurately calculate changes in soil carbon that will result from the adoption of climate smart practices.

As a real world example, it will allow a PNW wheat grower to quantify the likely climate benefits of avoiding tillage—measured as additional carbon sequestered in their soils—and to better evaluate the potential payout in one of the emerging climate smart market opportunities that credit such practices.

The workgroup held its initial meeting on March 21, attended by about 30 members of this emerging community, including leading public- and private-sector teams, e.g., USDA/NRCS, HabiTerre, Indigo, Nori, and Regrow. The workgroup’s guiding principles (Fig. 1) and deliverables were broadly endorsed as being both achievable and valuable for building trust and credibility, qualities that have fallen prey to skepticism in certain corners of the climate smart marketplace.

List of guiding principles for the Workgroup
Figure 1. Guiding principles for the activities of the workgroup. MME = Multi-Model Ensemble. IP = Intellectual Property. API = Application Programming Interface.

Also at the March 21 meeting, workgroup member Bruno Basso (Michigan State U) reported that he is developing a shareable tool that runs an ensemble of seven leading crop and soil models: APSIM (CSIRO et al.), ARMOSA (U Milan), CropSyst (from WSU’s Claudio Stöckle), DayCent (NREL/Colorado State U), DSSAT (U Florida et al.), EPIC (Texas A&M), and SALUS (Michigan State U). Dr. Basso will be presenting this work at AgMIP9, to be held June 26-30 at Columbia University (New York City), where I plan to join him and invite additional participation in our workgroup. Based on Dr. Basso’s excellent progress and openness to continued collaboration, we’ve developed an overall vision for how the API will work (Fig.2).

Diagram showing inputs to the ensemble of models, and outputs, including probability distributions of soil carbon for different models and the ensemble
Figure 2. A schematic showing how the proposed API will function, running a set of seven leading models based on the same input data currently required by the Fieldprint Platform.

On June 6, the workgroup’s core-team members gave an update in the form of a panel presentation at the Field to Market Plenary in St. Louis. The diverse, multi-sector audience included farmers, industry, researchers, and government scientists. They expressed keen interest and we heard a strong sense of urgency to make this new tool available as soon as possible, so that these more accurate calculations can be utilized in the many climate smart projects that are now launching on millions of acres of farmer fields nationwide. The initial focus will be on the row crops covered by Field to Market, and therefore not yet for possible future applications in grazing lands, orchards, or other specialty crops. Nevertheless, as noted above, the tool will be highly relevant to potato and wheat growers in the PNW. Please stay tuned for updates!

David I Gustafson, Ph.D., is an independent scientist who uses modeling to help food systems meet human nutrition needs in more sustainable ways. In 2020, he joined WSU in an Adjunct Research role and now resides in his hometown of Spokane.