Case study: Soil carbon MRV & incentives — a city or utility pilot and the results so far

In 2022, the Iowa Department of Agriculture and Land Stewardship launched a $12.8 million soil carbon incentive pilot spanning 23 counties and 187,000 acres, making it the largest state-administered soil carbon MRV (measurement, reporting, and verification) program in the United States. By the end of the 2025 growing season, the program had enrolled 412 farmers, measured soil organic carbon changes across 1,247 sampling plots, and issued payments totaling $7.4 million for verified carbon sequestration averaging 0.38 metric tons of CO2 equivalent per acre per year. The pilot demonstrated that government-led soil carbon incentive programs can achieve measurable climate outcomes, but only when MRV protocols, payment structures, and farmer engagement strategies are designed with the realities of agricultural practice firmly in mind.

Why It Matters

Agriculture accounts for approximately 10% of US greenhouse gas emissions, but agricultural soils also hold enormous potential to sequester carbon through improved management practices. The USDA estimates that widespread adoption of cover cropping, reduced tillage, and improved nutrient management could sequester 100 to 200 million metric tons of CO2 equivalent annually across US croplands (USDA, 2024). However, translating this potential into verified, bankable carbon storage requires MRV systems that are scientifically rigorous, affordable at scale, and compatible with the operational realities of working farms.

Voluntary carbon markets have struggled with credibility challenges around soil carbon credits, with studies finding that 30 to 50% of credits issued between 2018 and 2023 overstated actual carbon sequestration due to inadequate baseline measurement, short monitoring periods, and insufficient accounting for permanence risk (Carbon Direct, 2025). State and municipal pilots represent an alternative pathway: publicly funded, transparently governed programs that can establish MRV standards and build farmer trust before scaling to broader market mechanisms.

Key Concepts

Soil carbon MRV encompasses the methods used to quantify changes in soil organic carbon stocks over time, verify that observed changes result from intentional management practices, and report results in formats that support payment or credit issuance. Three primary MRV approaches are deployed in current programs:

Direct soil sampling involves collecting physical soil cores at defined depths (typically 0 to 30 cm and 30 to 100 cm), analyzing them for organic carbon content via dry combustion, and calculating carbon stock changes relative to baseline measurements. This approach delivers the highest accuracy (plus or minus 5 to 10% at the field scale) but costs $15 to $35 per acre when sampling density is sufficient to capture spatial variability.

Remote sensing and modeling uses satellite imagery, weather data, and biogeochemical models (such as DNDC, DayCent, or COMET-Farm) to estimate carbon stock changes based on observed land management practices and environmental conditions. Model-based approaches cost $1 to $5 per acre but carry uncertainty ranges of 25 to 50% at the field scale without ground-truth calibration.

Hybrid approaches combine targeted direct sampling with model-based estimation, using physical measurements to calibrate and validate models. This strategy reduces per-acre costs to $5 to $15 while maintaining uncertainty below 20%, and has emerged as the preferred approach for programs operating at scale.

MRV Approach	Cost per Acre	Accuracy	Scalability	Best Use Case
Direct soil sampling	$15-35	Plus or minus 5-10%	Low	Research plots, high-value credits
Model-based estimation	$1-5	Plus or minus 25-50%	High	Screening, trend monitoring
Hybrid sampling plus models	$5-15	Plus or minus 15-20%	Medium-High	State/municipal programs
Spectroscopic field analysis	$8-20	Plus or minus 10-15%	Medium	Rapid field verification

What's Working

The Iowa pilot's design incorporated several features that proved critical to achieving both scientific credibility and farmer participation.

Stratified sampling protocol with cost sharing. The program adopted a hybrid MRV approach, requiring baseline soil sampling at a density of one composite sample per 20 acres (roughly 3 cores per composite) at two depth intervals. The state covered 75% of sampling costs through contracts with certified soil laboratories, reducing the farmer's out-of-pocket expense to approximately $4 per acre. This cost-sharing model was identified as the single most important factor in farmer enrollment, according to surveys conducted by Iowa State University Extension (ISU Extension, 2025).

Practice-based payments with verification tiers. Rather than paying exclusively per ton of verified carbon, the pilot used a tiered payment structure. Farmers received a base payment of $15 per acre for adopting qualifying practices (cover crops, no-till, or diverse rotations), with an additional performance bonus of $25 per verified metric ton of CO2 equivalent sequestered above the baseline. This approach ensured that farmers received compensation for practice adoption regardless of whether soil carbon changes were measurable within the first year, addressing the fundamental timing mismatch between practice implementation (immediate cost) and carbon accumulation (multi-year process).

Digital practice verification using satellite imagery. The Iowa Department of Agriculture partnered with Regrow Ag (formerly FluroSat) to deploy satellite-based practice verification across all enrolled acres. Sentinel-2 and Planet imagery at 3 to 10 meter resolution confirmed cover crop establishment, tillage status, and crop rotation compliance at a cost of $0.80 per acre per year, eliminating the need for on-farm inspections for practice verification. Satellite-based verification correctly identified practice adoption in 94% of enrolled fields when validated against farmer-reported data and ground-truth inspections on a 10% random sample (Regrow Ag, 2025).

Multi-year commitment with flexible exit. Enrolled farmers committed to a minimum five-year practice adoption period, matching the timeframe needed to detect statistically significant soil carbon changes. However, the program included a no-penalty exit clause allowing farmers to withdraw after year two if severe weather, market conditions, or personal circumstances made continued participation impractical. Only 8% of enrolled farmers exercised this exit option through year three, compared to 25 to 40% attrition rates reported in voluntary carbon market programs with rigid multi-year contracts.

County-level soil health coordinators. The state hired 12 soil health coordinators embedded within county extension offices to support farmer enrollment, answer technical questions, and facilitate peer learning networks. These coordinators proved essential: counties with dedicated coordinators achieved enrollment rates 3.2 times higher than counties relying on centralized outreach alone. The coordinators also identified and resolved sampling logistics problems, such as coordinating soil collection timing around planting and harvest schedules, that would have undermined data quality without local knowledge.

What's Not Working

Despite its successes, the Iowa pilot exposed significant challenges that other jurisdictions must address.

Baseline variability and detection limits. Soil organic carbon varies naturally by 20 to 40% within a single field due to topography, drainage patterns, and historical management. Detecting a sequestration signal of 0.3 to 0.5 metric tons CO2 equivalent per acre per year against this background noise requires either very high sampling density (increasing costs) or multi-year monitoring periods (delaying payments). In year one, only 31% of enrolled fields showed statistically significant carbon increases at the 90% confidence level. By year three, this rose to 64%, but one-third of fields still showed no detectable change despite verified practice adoption.

Permanence and reversal risk. A severe drought in 2024 caused cover crop failures on approximately 18% of enrolled acres, and follow-up sampling indicated that some fields lost previously sequestered carbon due to accelerated decomposition under hot, dry conditions. The pilot's payment structure did not include a permanence buffer or insurance mechanism, creating a gap in the program's climate integrity. Addressing this requires either discounting issued credits by 15 to 25% (as some voluntary registries do), establishing a carbon insurance pool funded by a levy on payments, or structuring payments as ongoing practice incentives rather than permanent carbon claims.

Data management and interoperability. Soil sampling data, satellite imagery, farmer practice records, and payment processing were managed across four different software platforms with limited integration. Data reconciliation consumed approximately 1,200 staff hours in year two alone. The lack of a unified data standard also complicated reporting to federal agencies and made it difficult to compare results with pilot programs in other states. The OpenTEAM initiative and USDA's emerging soil health data standards offer potential solutions but were not mature enough for adoption during the pilot's design phase.

Equity and access gaps. The pilot's enrollment skewed heavily toward larger operations: the median enrolled farm was 820 acres, compared to the state median of 345 acres. Smaller operations faced proportionally higher per-acre costs for soil sampling, had less capacity to absorb the risk of practice changes, and were less likely to have existing relationships with extension services. Black, Indigenous, and other historically underserved farmers represented less than 3% of pilot participants despite targeted outreach efforts. Addressing this gap requires sliding-scale cost sharing, culturally appropriate outreach, and technical assistance programs designed for smaller and diversified operations.

Key Players

Established Organizations

• USDA Natural Resources Conservation Service (NRCS): Provides technical standards for soil health practices and co-funds conservation programs through EQIP and CSP that align with state-level carbon incentives
• Iowa Department of Agriculture and Land Stewardship: Designed and administered the pilot, coordinating sampling logistics, payments, and data management across 23 counties
• Verra: Operates the Verified Carbon Standard's VM0042 methodology for soil carbon quantification, which informed the pilot's MRV protocol design
• Gold Standard: Developed the Soil Organic Carbon Framework used by several international soil carbon programs and increasingly referenced by US state programs

Startups and Technology Providers

• Regrow Ag: Provided satellite-based practice verification and modeling platform, processing imagery for 187,000 enrolled acres at sub-dollar per-acre costs
• Yard Stick PZT: Developed in-field soil carbon measurement probes using percussion-based sensing that reduce sampling time from 30 minutes to 3 minutes per site
• Perennial: Built a soil carbon mapping platform combining remote sensing with machine learning to predict field-level carbon stock changes at county scale
• Boomitra: Deploys AI-driven soil carbon quantification using satellite data calibrated against direct sampling networks across multiple continents

Investors and Funders

• USDA Climate-Smart Commodities Program: Provided $3.1 billion in grants supporting soil carbon measurement and incentive projects across 141 programs nationwide, including co-funding for the Iowa pilot
• Walton Family Foundation: Funded soil health research and MRV development through grants to academic institutions and technology startups
• Microsoft Climate Innovation Fund: Invested in soil carbon removal verification technologies as part of its commitment to become carbon negative by 2030

Action Checklist

• Conduct a baseline soil sampling campaign at minimum density of one composite sample per 20 acres, at 0-30 cm and 30-100 cm depths, before enrolling farmers in incentive payments
• Adopt a hybrid MRV approach combining targeted direct sampling with satellite-based practice verification and biogeochemical modeling to balance cost and accuracy
• Structure payments as practice-based incentives with performance bonuses rather than exclusively per-ton carbon payments to maintain farmer participation during early years when carbon changes may not be detectable
• Establish cost-sharing mechanisms covering 50 to 75% of sampling expenses to reduce enrollment barriers for smaller operations
• Deploy county-level or regional soil health coordinators to support farmer engagement, troubleshoot logistics, and facilitate peer learning
• Build permanence safeguards into program design, whether through credit discounting, insurance pools, or ongoing practice-contingent payment structures
• Invest in unified data management systems that integrate sampling results, satellite verification, practice records, and payment processing from day one
• Design equity provisions including sliding-scale cost sharing, targeted outreach to underserved communities, and technical assistance for small and diversified operations

FAQ

Q: How long does it take to detect statistically significant soil carbon changes from improved management practices? A: Under typical conditions in the US Corn Belt, detecting a statistically significant increase in soil organic carbon requires three to five years of consistent practice adoption and repeated sampling. The rate of accumulation depends on baseline carbon levels, soil texture, climate, and the specific practices adopted. Cover cropping combined with no-till on medium-textured soils typically produces measurable changes (0.3 to 0.5 metric tons CO2 equivalent per acre per year) within three years. Sandy soils and already carbon-rich soils accumulate carbon more slowly and may require five or more years for detection at standard sampling densities.

Q: What is the cost per ton of verified carbon sequestration in government-led soil carbon programs? A: The Iowa pilot's all-in cost, including MRV, administration, farmer payments, and technical assistance, averaged $78 per metric ton of CO2 equivalent for verified sequestration through year three. This is higher than voluntary market prices of $15 to $40 per ton for soil carbon credits, but the pilot's MRV standards were significantly more rigorous and the per-ton cost is projected to decline to $45 to $55 as the program scales and fixed costs are distributed across more acres. State-funded programs also deliver co-benefits including water quality improvement, soil health, and rural economic support that are not captured in per-ton cost comparisons.

Q: Can satellite imagery replace direct soil sampling for soil carbon MRV? A: Not yet. Satellite imagery is effective for verifying practice adoption (cover crop presence, tillage status) with 90 to 95% accuracy, but cannot directly measure changes in soil organic carbon stocks below the surface. Modeling platforms that use satellite-derived inputs can estimate carbon changes, but these estimates carry uncertainty of 25 to 50% without ground-truth calibration. The most cost-effective approach combines satellite practice verification with targeted direct sampling to calibrate models, reducing per-acre MRV costs by 50 to 70% compared to sampling-only approaches while maintaining uncertainty below 20%.

Q: How should programs address the risk of carbon reversal if farmers stop practicing cover cropping or no-till? A: Programs should incorporate permanence risk through one or more mechanisms: a buffer pool that withholds 15 to 25% of issued credits or payments as insurance against reversals; contractual clawback provisions that require repayment if practices are abandoned within a defined period (typically 10 years); or structuring all payments as annual practice incentives rather than one-time carbon claims, which eliminates permanence risk by framing the payment as compensation for ongoing service delivery rather than a permanent carbon removal claim. The Iowa pilot's experience with drought-induced cover crop failures in 2024 demonstrates that even well-intentioned farmers face conditions beyond their control, making punitive clawback provisions counterproductive.

Sources

• USDA Economic Research Service. (2024). Soil Carbon Sequestration Potential of US Croplands: Updated Estimates and Policy Implications. Washington, DC: USDA ERS.
• Carbon Direct. (2025). Soil Carbon Credit Integrity: A Review of Verification Outcomes 2018-2023. New York, NY: Carbon Direct Inc.
• Iowa State University Extension and Outreach. (2025). Iowa Soil Carbon Incentive Pilot: Farmer Enrollment, Participation, and Satisfaction Survey Results. Ames, IA: ISU Extension.
• Regrow Ag. (2025). Satellite-Based Practice Verification for Agricultural Carbon Programs: Accuracy Assessment and Operational Performance. San Francisco, CA: Regrow Ag Inc.
• Iowa Department of Agriculture and Land Stewardship. (2025). Soil Carbon Incentive Pilot Program: Year Three Progress Report. Des Moines, IA: IDALS.
• National Academies of Sciences, Engineering, and Medicine. (2024). Negative Emissions Technologies and Reliable Sequestration: A Research Agenda, Updated Assessment. Washington, DC: The National Academies Press.
• Oldfield, E.E., Bradford, M.A., and Wood, S.A. (2024). "Global meta-analysis of the relationship between soil organic carbon and crop yields." Soil Biology and Biochemistry, 178, 108926.