On November 9th, 2023, ICCON was joined by Etienne Sutton, a PhD candidate and National Institute of Food and Agriculture fellow from the University of Michigan School for Environment and Sustainability. Etienne shared her research on cover crop performance in the Great Lakes Region which used citizen science, participation by the public in the scientific process, to gather field data across the region. Her research goal is to examine how and why cover crop growth varies from farm to farm, and by season. With this information, she hopes to advise farmers on how to best strategically manage cover crops for improved agricultural sustainability.
Etienne began by giving an overview of how she partnered with Great Lakes region farmers on 253 fields. Her objective was to quantify the variation in cover crop biomass across farms, identify the key drivers of that variation, then use that information to develop management recommendations. She noted that the study is specifically designed to overcome some of the typical time and labor constraints that are associated with on-farm research. Farmer participants were asked to perform two tasks. First, complete a short online management survey to allow the research team to better understand what specific field conditions could be impacting growth. Questions covered a diverse range of management practices, soil health practices, and environmental conditions. Second, perform a simple field assessment composed of a cover crop canopy photo to assess percent ground cover and followed by height measurements, calculating the estimated quantity of cover crop biomass. Researchers also noted approximate weed biomass and cover crop mixture biomass (if applicable). The field assessment took place over three field locations prior to cover crop termination and used the Foliage app to estimate ground cover from photos. Following data analysis, farmers were paid $50/field (up to $100 total payment, but more fields could be enrolled) and received a cover crop performance report detailing project results and personalized estimates of cover crop biomass and nutrient composition.
Etienne described the methods used to calculate the estimated cover crop biomass, including the combination of an app estimating canopy cover percentage and height measurements taken in the field.
The examination of cover crops in the spring of 2022 and 2023 led to a variety of interesting observations. The study found that cover crop mixture biomass often far outperformed cereal rye biomass. However, Etienne noted that upon further examination, farmers were typically growing multispecies mixes following a small grain, compared to rye, which was planted generally after corn/soybeans. As a result, multi-species mixes were on average planted one month earlier and had nearly double the accumulated Growing Degree Days (GDD) when compared to cereal rye. For mix composition, Etienne noted that there were benefits to both increasing number of species (three grasses vs. one) and number of plant types (mixing grass, legumes, and brassicas), but more research was needed. The following graph shows some of the relationships Etienne found between management or environmental factors and final cover crop mix biomass.
This decision tree could support farmers in understanding how species richness, precipitation, management decisions, and soil types can influence biomass production.
Etienne noted that when looking at cereal rye specifically, the most important factor in biomass determination is GDD, as expected. The approximate cutoff found in the data was 823 GDD (base 32 degrees). Cereal rye plantings receiving less than 823 GDDs had an average biomass of 465 kg/ha, while those above 823 GDDs had an average biomass of 1429 kg/ha. She noted that there were several techniques that farmers were using to increase GDD accumulation. Farmers were either planting earlier in the fall by aerial application or interseeding, or terminating later in the spring and planting green.
Lastly, Etienne stressed the importance of getting farmers involved in research and developing management and outcome based recommendations. Diversified rotations stood out in their research as an optimal place to incorporate cover crops successfully, but ultimately the outcome of a cover crop is determined by complex environmental and management factors. While there is not a third round of studies planned, Etienne mentioned the possibility of additional funding that may be used to continue working with farmers in the program to adjust the management survey to hone in on the reasons farmers use cover crops and the innovations they use to incorporate them into operations. For more information, visit their lab’s website at https://bleshlab.com/ or reach out to Etienne directly at herricke@umich.edu
Etienne’s full presentation can be viewed on ISAP’s YouTube channel. During the December call, ICCON will be joined by Rob Myers, Director of the Center for Regenerative Ag at Missouri State University, who will present on the 7th National Cover Crop Survey report, released by SARE, CTIC, and the American Seed Trade Association this summer. Register for upcoming ICCON calls here. If you are interested in joining the Illinois Cover Crop On-Farm Network to learn about new research and hear from cover crop specialists across the Midwest, please join our google group by sending an email to hvanbeck@farmland.org.
