Climate change mitigation necessitates negative emissions technologies, including soil carbon sequestration in agricultural lands. While government and private sector initiatives incentivize farmers to adopt beneficial practices for carbon sequestration, the effectiveness of these incentives is debatable. Previous research indicates that farmers primarily adopt such practices due to local environmental co-benefits and soil health improvements, rather than climate mitigation services. This study aims to understand the motivations and concerns of both participating and non-participating US farmers (specifically conventional row-crop farmers and organic farmers) regarding agricultural soil carbon markets developed since 2017, focusing on two primary offset project producers: Nori and Indigo. The core assumption of additionality—that activities are solely due to financial incentives—is examined. The study hypothesizes that participating farmers adopted practices for both environmental co-benefits and financial reasons, while non-participating organic farmers adopted them solely for environmental reasons.

Existing literature highlights various facilitators and barriers to farmer adoption of soil carbon sequestering activities. Facilitators include local environmental co-benefits and soil health benefits, while barriers include unfamiliarity with practices, lack of information, and concerns about implementation costs. Much previous research focuses on landowners in biodiversity conservation programs, rather than row-crop farmers. Studies consistently demonstrate that farmer motivations are primarily driven by perceived co-benefits, not financial returns or carbon sequestration itself. The challenges faced by voluntary carbon offset developers include ensuring accurate carbon sequestration measurement and guaranteeing additionality (i.e., the sequestration wouldn't have occurred without the financial incentive). Existing protocols, such as those from the Verified Carbon Standard, Climate Action Reserve, and American Carbon Registry, attempt to address these challenges but may not fully succeed, particularly in ensuring genuine additionality.

This qualitative study employed semi-structured interviews with two groups of farmers: (1) conventional row-crop farmers participating in voluntary carbon markets (primarily through Nori and Indigo), and (2) certified organic row-crop farmers not participating in these markets. Participants were recruited via email or phone using contact information from market websites and organic farmer registries. Seventeen interviews were conducted between January 2021 and February 2022, lasting 30 minutes to 1.5 hours. Interviews were recorded, transcribed, and analyzed using a modified grounded theory approach. Two main coding goals were established: (1) identifying motivations for adopting carbon sequestering activities, and (2) identifying concerns about existing offset markets. Iterative readings of transcripts by both authors led to the development of a two-level code book, which was refined by comparing categories with existing literature on barriers and facilitators. After achieving saturation, all coding was redone using NVivo software and manual coding, with intercoder reliability checked (91% agreement). Response rates were 69% for participating farmers and 45% for non-participating farmers.

The primary motivations for adopting beneficial farming practices were consistent across both farmer groups: (1) economic profitability and (2) maintaining healthy soils for future generations. Participating farmers, while aware of carbon credit payments, did not primarily adopt practices for that reason. They viewed the payments as a "gravy on top" of practices already implemented for other reasons. Organic farmers expressed similar motivations, focusing on soil and crop health, economic productivity, and adapting to extreme weather. Both groups shared concerns about carbon markets. These included: (a) payments being too low to incentivize new practice adoption, (b) burdensome paperwork and data requirements, (c) unpredictable and opaque payout calculations, (d) biases favoring larger farms, (e) greenwashing by companies using carbon credits, and (f) additionality requirements penalizing early adopters of beneficial practices. Farmers felt that current payment levels are insufficient to change the behavior of farmers not already interested in these practices and that additionality requirements unfairly penalize early adopters, creating perverse incentives. Many felt that the opaque and complex systems used to calculate payments discourage participation. There is a significant disconnect between market-defined additionality and farmers' perception of additionality. While the protocols do not require additional farmer motivation beyond the fact that they are undertaking new activities, farmer perceptions suggest that the credits are frequently not additional in terms of their motivations.

The findings challenge the assumption of additionality in voluntary carbon offset markets. Farmers' primary motivations for adopting beneficial practices are consistent across both participating and non-participating groups, emphasizing economic sustainability and soil health. The carbon credit payments are largely perceived as an added benefit rather than a primary driver of practice adoption. The concerns raised by farmers regarding market complexity, paperwork, unpredictability, bias, and additionality highlight significant barriers to wider participation and raise questions about the effectiveness of these markets for climate change mitigation. These results align with previous research indicating that administrative burdens hinder participation and that simple information provision isn't sufficient to address underlying trust issues. The study also underscores the disconnect between how carbon markets define themselves and farmers' actual motivations and perceptions regarding the generation of carbon credits. This may hinder the effectiveness of these markets in achieving true climate change mitigation.

This study reveals a significant disconnect between the intended function of voluntary carbon markets for agricultural soil carbon sequestration and the reality of farmer participation and motivation. While carbon credits provide additional income, they are not the primary driver of adoption of beneficial practices. Farmers' concerns about market design, paperwork burdens, and the additionality requirement highlight critical issues that need to be addressed to improve the effectiveness and fairness of these programs. Future research should explore alternative incentive mechanisms that better align with farmer motivations and address the concerns highlighted in this study.

The study's limitations include a relatively small sample size, geographically limited scope (primarily Midwest and Southeast US for participating farmers, and New York State for non-participating farmers), and reliance on self-reported data. The response rate for non-participating farmers was lower than for participating farmers, potentially introducing bias. The focus on two specific carbon market companies might not fully represent the diversity of market mechanisms available. The study's findings may not be generalizable to all regions or farming systems.