Cover Crops and Carbon: Integrating Field and Stream Carbon Budgets in Tile-Drained Indiana Farmland

Commodities

Practices

In the intensively farmed Midwestern Corn Belt, subsurface tile drainage accelerates the transport of nutrients and carbon (C) from agricultural fields to streams, impacting both terrestrial and aquatic C cycles. This project addresses a critical knowledge gap by examining how winter cover crops influence C fluxes across the atmosphere-land-water continuum in tile-drained agricultural landscapes. While cover crops are widely promoted for soil conservation and carbon sequestration, their effects on dissolved organic carbon (DOC) export via tile drains and subsequent in-stream metabolism remain poorly understood. Understanding these dynamics is essential for farmers and land managers aiming to improve soil health, reduce greenhouse gas emissions (GHG), and participate in carbon markets. This study leverages two tile-drained fields in the Shatto Ditch Watershed (SDW; Kosciusko County, IN) - one planted with winter cereal rye cover crops and one left fallow. Utilizing eddy covariance towers, we will quantify terrestrial carbon exchange to calculate net ecosystem productivity (NEP). Concurrently, biweekly sampling of tile drain water analyzed for DOC concentrations will measure C losses from fields via tile drains. Continuous stream metabolism will be assessed downstream of each field using two-station open-channel metabolism to quantify aquatic carbon cycling. By integrating terrestrial NEP, tile drain DOC export, and in-stream metabolic rates, this project will construct a comprehensive C budget at the field scale, revealing how cover crops affect soil C retention, aquatic CO₂ emissions, and overall ecosystem sustainability. Outcomes from this research will inform farmers about the carbon cycling benefits of cover cropping, helping them understand the role of these practices in enhancing soil C sequestration while mitigating aquatic C losses and GHG emissions. Our results will guide on-farm management decisions and foster the co-production of knowledge between farmers and scientists for improved agricultural sustainability. Evaluation of learning and action outcomes will involve surveys assessing farmer knowledge gains and intentions to adopt cover cropping strategies based on project findings. This interdisciplinary project builds upon long-term (>17 years) collaborations with local growers in SDW, and integrates expertise and facilities at the University of Notre Dame and Indiana University Bloomington, ensuring rigorous science with direct applicability to Midwestern agricultural stakeholders.

The primary audiences for this project include farmers, conservation professionals, policymakers, and regional stakeholders in the North Central Region. Through this project, these audiences will gain enhanced knowledge and awareness of how winter cover crops influence C dynamics and water quality in agroecosystems, particularly regarding reductions in CO₂ emissions and improvements in soil health via enhanced soil C sequestration.

Learning outcomes include:

• Farmers and conservation staff will learn how cover cropping affects stream C cycling, increasing their understanding of ecosystem services across environmental compartments (e.g., terrestrial and aquatic) provided by conservation practices.
• Policymakers will gain insight into the broader environmental benefits of cover crops beyond soil health, informing future agricultural and water resource policies.
• Regional stakeholders and students will develop improved skills and awareness around monitoring stream metabolism and interpreting aquatic ecosystem health.

Action outcomes include:

• Farmers may adopt or expand the use of winter cover crops with greater confidence in their environmental benefits, especially related to reducing C losses from agricultural landscapes.
• Conservation professionals will integrate new findings into their advisory and outreach efforts, supporting broader adoption of climate-smart agricultural practices.
• Policymakers could incorporate these results into decision-making frameworks that promote sustainable land and water management.

Evaluation of outcomes will involve tracking participant knowledge gains and intended behavior changes through listening sessions and feedback collected during farmer meetings, Kosciusko County (Indiana) SWCD presentations, and outreach events.