South Dakota Regional Conservation Partnership Program project gains ground, giving initial hints of farming practices impact on soil carbon.
By Susanne Retka Schill
A multi-faceted, in-depth project is gaining traction in the counties surrounding Dakota Ethanol in southeastern South Dakota. Thirty farmers from seven counties are closely watching the fields enrolled in the Regional Conservation Partnership Program (RCPP) project looking at the carbon intensity on biofuel feedstocks grown using cover crops, 4R fertilizer management and/or reduced tillage.
The American Coalition for Ethanol (ACE) pulled together the team that successfully landed a $7.5 million RCPP project in 2021 through the United States Department of Agriculture’s (USDA's) Natural Resource Conservation Service (NRCS). $5.25 million is earmarked to reimburse farmers for carbon intensity reducing practices. The remainder reimburses the partners implementing the project and collecting and analyzing the data from farmers. In addition to NRCS and ACE, other partners include Dakota Ethanol, South Dakota Corn, South Dakota State University (SDSU), Virginia-based Cultivating Conservation and the Department of Energy’s (DOE’s) Sandia National Laboratory.
While SDSU is focused on soil organic carbon changes occurring with the conservation practices, it has taken advantage of the RCPP project to add complementary activities, such as South Dakota Soybean funding for research that aids in sharing the results with others. Also, a former USDA Agricultural Research Services scientist who formed a group called Agronomic, Geologic, and Environmental Services (AGES) in Missouri is helping to quantify the impact of the new conservation practices on soil health. Some of that data has already resulted in papers published in peer review journals, and one earned the honor of being selected as the 2025 paper of the year by the American Society of Agronomy.
Implementing the farm practices took a little bit of time to get started. A few practices were implemented in the fall of 2023, but most were adopted last year, making 2025 the first year of full data collection. The final project design involves nearly 30,000 acres enrolled by 30 producers using three practices—no-till, cover crops and nitrogen management. Two-thirds of farmers are doing more than one practice, with between 5,500 and 8,300 acres adopting each practice. In addition, 19 farmers are sharing their historical data on some 6,000 acres. Farmers are providing yield data and fertilizer records and allowing access to fields for soil sampling and data collection.
Grower Participation
SDSU research associate Brennan Lewis is working closely with the farmers who’ve enrolled nearly 250 fields in one or more of the three practices. While most are conscious of soil health, they have been hesitant to risk potential yield and income loss from adopting new practices, Lewis says. “Having the RCPP reimbursements gave them the opportunity to experiment on their own farm and see what works for them.”
When enrolling farmers, Lewis sits and discusses SDSU’s and their responsibilities during the project. Farmers enrolling fields in 4R nutrient management (right rate, right time, right place and right nitrogen source) learn what they need to do to receive a reimbursement payment. They also learn about other techniques that can be used to improve nutrient efficiency and reduce expenses. “This project has helped with opening their eyes to new possibilities when changing practices, to allow them to be successful,” Lewis says. “And to counter some of the stigmas they’ve heard.”
For example, many have heard that with no-till they’ll have to wait for the soil to warm up in the spring and thus delay planting, which increases the risk of a yield hit. In the past few dry years, the farmers keeping a heavy residue in their no-till fields haven’t seen the yield hit that conventional fields experienced, Lewis says, because the residue conserved what rain did fall. Similarly, it’s often thought cover crops will create issues in the spring, but Lewis reports farmers using cover crops have had an advantage in a wet spring because the winter crop has taken up some water, allowing the field conditions to firm up for earlier planting.
DATA COMPARISON: Landsat satellite imagery gives enrolled farmers feedback on the change in crop health far more quickly than the field data being collected and analyzed in the RCPP. The NDVI image (normalized difference vegetation index) compares the previous year’s image with the current year. Red shows declines in greenness, often indicating drowned out areas, while the blue and green indicate positive responses to the treatments showing healthier plants. The scientists use the images to target the best areas for additional work, such as soil plant or water sampling to assess soil, environmental and plant health.
Lewis’ favorite story is about a farmer who was already in the process of transitioning some fields to no-till and experimenting with grazing cattle on cover crops during the winter. “This project really helped him to jump in with other fields. We came up with a plan for cover crops with some turnips, radishes and rye. The next spring I’m talking to him, and he says he’s pretty sure he has to buy cover crops every year because those cattle absolutely love the mix.” The cover crop cost was made up by weight gain on the cattle, Lewis says, plus the animals did some free tillage for him by breaking up compacted ground. “Those cows just dug through the snow, found the roots and pulled them right up.” In addition, grain yields weren’t impacted by the transition because of the nutrient cycling from the cattle. “He’s been really happy with this project and wondering why he didn’t do this 10 years sooner. It’s one of those things—he’s been doing it a certain way for so long, he wasn’t sure if he wanted to take the leap.”
Besides consulting with the farmers to plan the adoption of new practices, Lewis coordinates with scientists documenting the impact of those practices on soil carbon. This summer the AGES group from Missouri collected deep soil samples at the sites to conduct an extensive soil health assessment. This benchmark information will be used for future comparisons.
In turn, those real-world observations from SDSU and AGES soil sampling are being used to test the ability of scientific models to predict agricultural greenhouse gas emissions. “Different models give us different answers,” explains Dr. David Clay, distinguished professor of soil science at SDSU and South Dakota Corn chair. “So, when we use multiple models, we have more confidence in the prediction of those mathematical models. For example, how will planting cover crops impact corn and soybean yields in South Dakota?”
The DOE’s Sandia National Laboratory is running four models — DACENT, Ecosys and DNDC, plus a combination of the three that they call the “Ensemble” model—to predict soil carbon sequestration and GHG emissions. Then those predictions are compared with actual field observations. In the initial modeling work using current data, the Ensemble model was 50% more accurate than the individual models. The field data from the RCPP project will be used to further improve the accuracy of the modeling.
Expanded Research by SDSU
The RCPP project is being informed by related research. “We are attempting to investigate soil and plant health from a fresh perspective,” Clay explains. “We are making discoveries that are changing how we view agricultural systems. For example, we discovered that the cover crop rye increased the reduction of nitrous oxide to nitrogen gas. Findings such as these can lead to more accurate models. In addition, we use real data to show that our farmers are making a difference. Our studies show that soil health and productivity are improving.”
Clay points to earlier studies that looked at the adoption of reduced tillage in the northern Great Plains, growing from 0 in 1970 to 49% in 2011. Based on 12 million soil samples sent to Midwest Laboratories for fertilizer recommendations by farmers in four states over two decades, soil organic matter in the surface 6 inches is increasing at a rate of 650 pounds per acre every year. These increases are attributed to tillage reductions and increasing yields. Increases in soil organic matter are important, he explains, because it contributes to increased plant-available water, reduced erosion and higher productivity. Higher soil organic matter may also be associated with the 25% decrease in South Dakota nitrogen recommendations, Clay adds.
IMPROVING DATA: The three models on the right are used to predict soil carbon sequestration and GHG emissions. The DOE’s Sandia National Laboratory combined those in an “Ensemble” model, which is 50% more accurate than the three individual models when compared to field observations. The data from the RCPP project will be used to further improve modeling accuracy.
Nutrient Lessons
Nitrogen management is another area of RCPP focus that is being informed by the research focus of doctoral candidate Skye Brugler. “I’m trying to understand how we can apply nitrogen at the right time so we’re not losing carbon dioxide,” she explains. By reducing losses to mineralization, carbon is kept in the soil. Working on her master’s degree, she studied split fertilizer applications and now, working on her doctorate, she’s looking at fall versus spring application of broadcast urea. She’s using instrumentation that measures the carbon dioxide released to the air, along with ammonia, nitrous oxide and methane—all gases associated with nitrogen loss. For three years, her research has taken intensive measurements of some 900 samples six times a day, accompanied by well over 1,000 soil samples.
What she’s found counters the dominant recommendation that favors spring over fall applications. “When we are applying nitrogen to really warm soil, we have a lot more biological activity going on that releases carbon dioxide,” she says.
“It’s always been thought that fall application is not a preferable time,” Clay explains. “What Skye’s showing is that for us in South Dakota, fall application may be preferable over spring. Her research is asking the question whether what we’ve learned in more humid areas is appropriate for drier systems like we have in South Dakota.”
Past studies that resulted in the spring application recommendations were done in higher rainfall areas with coarse soils where the leaching of nitrogen into ground water is a major concern. That isn’t a big issue in South Dakota with its rainfall nearly one-fourth that of those areas studied, plus soil types far less susceptible to leaching. The South Dakota research indicates that 4R nitrogen management recommendations will need to be site specific, Clay says.
CI Score Impact
The RCPP project findings are important for ACE’s work in encouraging policies that will help farmers and ethanol producers monetize low-carbon farming practices through clean fuel markets and tax credits.
“The data we gather from this RCPP project, and the model runs the scientists conduct with the data is critically important because, for example, that's what's ultimately going to give the California Air Resources Board more confidence that they could begin to reward farming practices in the Low Carbon Fuel Standard,” says Brian Jennings, ACE CEO. “The goal is for market regulators to take what we've discovered from our RCPP and have more confidence in what the Ensemble modeling shows—for example, that no-till corn in Lake County, South Dakota, generates a carbon credit of eight or 10 points.”
While the California LCFS doesn’t yet incorporate feedstock CI accounting, the 45Z Clean Fuel Production Credit might. An eight- or 10-point reduction for no-till could seriously help reduce corn ethanol’s CI score wherever enough farmers in a plant’s corn draw makes it worthwhile to document and verify feedstocks. The IRA legislation set a 47.5-point threshold to qualify for a 20 cent-per-gallon 45Z tax credit, with an added incentive for each point of reduction below that. On average, corn ethanol scores around 50 points, with about half the CI score attributed to the corn feedstock.
Most ethanol companies have a firm handle on their CI score, Jennings says, “and there’s enough initial 45Z guidance out there that a lot of ethanol plants feel confident they can make a claim on a tax credit for 2025. However, their claim for a tax credit will likely not include farming practices because we don’t have clarification on that yet.”
In its final weeks, the Biden Administration put out a draft feedstock carbon intensity calculator and technical guidelines on how to quantify and verify low-carbon farming practices through 45Z and other markets, but Treasury does not plan to issue proposed rules until 2026, and it remains unclear if farming practices will be included, he adds.
“It's going to be really hard for an ethanol company to let farmers know what they might expect to get paid for low-carbon corn until the ethanol company knows the final rules, what the final quantification requirements look like, and what sort of third-party verification is involved. Until they have more information on the associated costs, it's going to be impossible for them to let farmers know what they think they can pay.”
While ACE works toward getting low-CI corn feedstock properly valued in ethanol markets, Clay says the work at SDSU is focused on improving productivity on the farms that will pay even without those premiums, while compiling the data to prove the practices’ impact on soil carbon. “We’re going from Brennan working with the farmers and implementing practices to writing the scientific papers so we can change the policy on how the carbon scores are actually calculated.”
