Project Summary:
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 8 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 farmer decision-making regarding contracts has been a challenge. The Minnesota Office for Soil Health (led by Cates and Marcelle Lewandowski) has worked with consultants from EOR to leverage the MOSH baseline data on adoption of soil health practices such as no-till and cover crops to estimate CI scores in various ethanol supply-sheds across Minnesota. Here we propose to build this work into a useful web and print resource for farmers, which would show them the potential payouts of adopting various practices. While each farm scenario is unique, and growers will need to enter their own information into online calculators to determine their scores, we think providing ballpark estimates will increase grower confidence to engage in the markets, and to try new practices with assurance of financial return. Since much information on these topics has come into Minnesota via private entrepreneurs offering services around CI score mapping and enhancement, there’s a definite need for an unbiased source of information on the markets.
Project methodology:
Field Research: The study will be conducted in a long-term research site near Wells in south central Minnesota. Drainage regimes were established in 2012. In 2017, three tillage treatments were imposed: 1) conventional, 2) strip-till, and 3) no-till. The site is divided into eight blocks where four blocks were randomly assigned to be drained and four were randomly assigned to be undrained that give us another environment that could interact with the tillage system, therefore by the end of next season we are going to have seven seasons, assessing two environments yielding 16 different situations to assess the cumulative effect of the tillage system on soybean yield and soil properties.
We plan to gather subject matter experts and educators focused on carbon and CI score contracting to begin to develop an active Extension program to support farmers in this area. 2025
CI Score Extension Program development: The team, led by the MN Office for Soil Health, is calculating CI scores of corn ethanol in different cropping scenarios across MN in 2024-25. Cates and Ryan Pesch will present these scenarios at the Soil Management Summit and Minnesota Ag Expo in early 2025. Based on feedback from these programs, Cates, Pesch, and Naeve will add content to the soil management section of the Extension web page, write a blog post summarizing the updates, and provide at least one more program on CI scores in 2025-26. As the federal policy landscape surrounding CI scores may change in 2025, the PIs will be prepared to frame the output as a valuable metric of sustainability if 45z tax credits are not forthcoming in the next year.