Carbon Credits in Minnesota: Evaluating the Dual Impact of Agricultural Management Practices on Carbon Sequestration and Crop Yield
Carbon farming refers to a carbon-sequestering change made in a farm in exchange for receiving payment for carbon credits. A carbon credit is essentially a certificate attesting that a specific amount of carbon dioxide has been removed from the atmosphere and sequestered for a long period. It is claimed that carbon credits represent an opportunity for farmers to earn an additional income from the carbon market while at the same time adopting sustainable farming practices and contributing to environmental conservation. Carbon credit programs for farms are mainly based on the change of agricultural practices from which the adoption of cover crop, or the adoption of reduced tillage are the ones with the greatest value. There can also be a marginal contribution from increasing diversity of the rotation and changing the fertilization strategy. Minnesota has a low adoption rate of cover crops and reduced tillage, so the potential impact of a turn to the Carbon market is relatively high. In fact, a crescent number of Minnesota farmers want to know or estimate the economic or financial benefits that this market would bring to their systems. An estimation of the potential economic benefit would require answering, among others, these two questions: i) How much carbon can be sequestered by adopting no-till or cover crops or both in Minnesota Ag systems? and ii) how these changes in management can affect crops yield?
Cover cropping is proposed as the more impactful practice to increase Carbon credits. The main benefit of cover crops is linked to biomass production and accumulation. Nevertheless, there can be a trade-off between cover crop biomass accumulation and the optimum cash crop planting date. Delayed planting affects the capacity of the crop to reach full radiation interception (soil coverage) before the beginning of the critical stages. Water used by the cover crop during the spring can also decrease the following cash crop yield, especially during drought summers. However, there is scarce information about the Carbon credits that a cover crop could generate or the possible effect of the cover crop on the cash crop yield under real farm rotations and conditions in Minnesota farms. No-till or strip-tillage are also proposed as important tools to generate crop credits. In this case, the main expected effect is a reduction in the carbon loss from the soil because of the lack of disturbance. The residue cover acts as a mulch, reducing water evaporation from the soil while increasing the rate of infiltration, which has been claimed to be an advantage especially during drier years. However, in cold and short seasons, there are some concerns and challenges associated with the adoption of reduced tillage systems. In colder climates, the soil may take longer to warm up in the spring under a no-tillage system compared to conventional tillage. This delay in soil warming can affect crop development and growth during the initial stages in a way that the conditions for crop growth during the critical reproductive stages to be less favorable compared with a crop in a conventional system. However, as for cover crops, there is limited data available to fully assess the impact of no-till or strip tillage on carbon storage or on the cash crop yield for real farm conditions in Minnesota.
Because of their relatively small annual effect, any attempt of assessing the impact of management on soil carbon sequestration would imply several years before having a result. In the same direction, when assessing the impact of management on crop yield (i.e., cover crops, tillage systems), and recognizing the importance of complex interactions, it is important to gather information from diverse weather scenarios, a goal that can be achieved by assessing several and variable seasons. Lastly, soil carbon sequestration capacity of a combination of management practices can be affected by the nitrogen inputs to the system, because of its impact on biomass production and soil organic matter degradation, nitrogen input can also impact on NOx emissions. Therefore, the nitrogen input scenario must be considered or assessed in any attempt of estimation of the ability of a management practice to generate carbon credits.
This project aims to provide answers to the aforementioned questions, utilizing our established long-term experiment located near Wells, Minnesota. This experiment has been assessing different tillage systems under different N inputs in a corn-soybean rotation for the last 7 years. In addition, recently, we also started to assess the effect of the cover crop, assessing the interactions among all factors. Focusing on both the effect of management on carbon sequestration and yield, this project seeks to generate a better idea of the implications of these management practices on carbon sequestration and yield for Minnesota cropping systems.
Because of the extremely dynamic and complex nature of carbon sequestration and carbon intensity (CI) score markets, supporting framer decision-making regarding contracts has been a challenge. Recently, the Minnesota Department of Ag has teamed with MN Farmers Union to produce a “Farmer’s guide to Carbon Market Contracts in Minnesota” and the Department of Applied Economics at the University of Minnesota is looking to hire a faculty member to work in this space. Dr. Anna Cates, Soil Health Specialist at the University of Minnesota has a keen interest in engaging producers to support farmers as they examine opportunities to search out opportunities to contract with private companies for enhanced conservation adoption. Our aim with this project is to begin to integrate various resources and education efforts to support farmers in this new area.