Quantifying the impact of cover crop implementation on sediment and nitrogen export in small agricultural watersheds and beyond

Commodities

Practices

Agriculture is a vital component of life and is needed to provide food for a growing population. However, conventional agricultural practices can have negative environmental consequences like sedimentation and eutrophication of downstream waterbodies. Therefore, research is needed on agricultural conservation practices that reduce soil and nutrient loss to protect both farmers from financial losses, as well as water quality in downstream waterways. Winter cover crops are a conservation practice whereby fields are planted with green cover during the fallow season, instead of being left bare. Vegetative cover can retain topsoil and nutrients, especially during storms or snowmelt, by reducing water erosion. Much of the past cover crop research has focused on headwater streams, but their effect on nutrient and sediment export to downstream systems and how these exports compare to those from larger river basins remains a critical understudied issue. Many of these large river basins are of great concern for nutrient and sediment export, as they feed into the Mississippi River which drains much of the US. Placing small agricultural watersheds with high cover crop coverage into the context of larger basin export, especially for river basins of concern in key agricultural states like Indiana, will help improve our understanding of the benefits of cover crops at multiple spatial scales. This context will also be critical as climate change increases the frequency and intensity of storm events in the North Central Region. Here, we propose to use a combination of grab-sample data, sensor data, and USGS monitoring data to quantify the effects of cover crops on nutrient and sediment export at the field-, agricultural watershed-, and river basin-scales. This work will require year-round field work and will build on the larger “Indiana Watershed Initiative” project starting in 2015. We will share our data and findings with producers, resource managers, government officials, and others in order to convey the potential benefits of cover crops on water quality. We will evaluate our progress through frequent data downloads and analyses, with progress reports and summarized findings given to project partners quarterly. The learning and action outcomes of this project will provide quantitative support and knowledge on the effects of cover crop implementation on sediment and nutrient export in agricultural watersheds using long-term, multi-year data that incorporates hydrologic variation over space and time.

Learning Outcomes:

I will provide producers and resource managers [i.e., Soil and Water Conservation District (SWCD)] with data quantifying the effects of cover crops on nutrient and sediment export at the field-, watershed-, and river basin-scales. I will compare nitrate-N (NO₃^--N) and sediment export over 7 years, for two small agricultural watersheds in Indiana using grab sample and sensor data. I will then compare these data to export from major Indiana river basins with a range of cover crop coverage using publicly available data. This approach will place export estimates into context with larger systems and enables us to examine the scale of cover crop impacts on fluvial export. Our research impact will extend beyond watershed science; I will share our findings at farmer field days, stakeholder meetings, and with government officials, thus translating our research to diverse audiences.

Action Outcomes:

Our working relationship with landowners and resource managers in two small agricultural watersheds began in 2008. Since then, our year-round field sampling and monitoring continues to support SWCD efforts to encourage adoption of conservation practices by producers including planting cover crops. The analysis of multi-year data will enhance our understanding of cover crop benefits, including their impacts on nutrient and sediment transport. Findings will enable SWCD staff to communicate the benefits of cover crops to producers using data-informed examples. We will share our findings at local, regional, and national interdisciplinary meetings. Lastly, we will communicate results to government stakeholders and agencies to better inform policy and management decisions.