Do More Species Equal More Benefits?

On many farms, a cover crop is a single species planted between cash crops. The Cover Crop Cocktails project takes a different approach, planting several species together to see what a mix can do that one species alone cannot. Funded through federal grants since 2012, the project studies these mixtures in an organic corn, soybean, and wheat rotation. The idea behind it is that a diverse blend of cover crops brings more ecological stability and could do more for the soil than any single component, from cycling nitrogen to feeding the crops that follow. 

A cover crop cocktail can handle several jobs at once. A legume in the mix pulls nitrogen from the air and fixes it in the soil, giving the next crop a natural fertility boost, while other species suppress weeds, build organic matter, or support beneficial insects. To observe all of these effects, the project brings together multiple labs studying different pieces of the puzzle, from weeds and pests to entomology. Researchers compare mixtures against single-species plantings and test how those mixes hold up across different seasons, sites, and growing conditions. 

The goal is to give farmers information they can trust before they commit their own fields to a new practice. Rather than learning through trial and error, farmers can lean on research that shows which mixes work under which conditions. At its heart, the project is about producing food more sustainably while cutting the environmental costs of farming. Cover crop mixtures deliver several benefits at once, which is what makes them so promising for organic systems.  

Current work is comparing the effects of exclusively annual cropping rotations with those with a diverse mix of perennial forages and taking a closer look at ecosystem services like pollinator support and building up soil organic matter. 

Part of that work, led by soil scientists Dr. Charlie White and Dr. Jason Kaye, focuses on nitrogen, delivering it to the corn crop and keeping it in the field rather than losing it. Better nitrogen estimates help farmers save money on fertilizer without giving up yield, and the legumes in a cover crop mix stretch those savings even further. Dr. Carolyn Lowry is studying ways to manage weeds ecologically, while Master's student Allie Rice examines how weed populations respond in these systems.  

On the insect side, postdoctoral scholar Dr. Kayleigh Hauri studies how a plant's defenses shape its interactions with pests, and how those defenses trace back to the soil. Its microbes and chemistry determine how well a plant defends itself, and each cover crop mixture leaves behind a different soil legacy. Working mainly with corn, she's testing which combinations build the best insect resistance. She's drawn to the work because the effects are visible. She can see caterpillars grow larger or smaller depending on the soil legacy they're feeding on, and she values contributing one piece to a much larger puzzle. 

Brosi Bradley, a research technician on the project since its 2012 start, finds it both rewarding and a joy to help farmers understand the impact of practices like cover crops, alongside such an excellent team of researchers. She also values the chance to look beyond the short-term results of a single year or a single research focus. 

Researchers hope the 14-year-and-counting length of the experiment, and the broad interests of its research team, will reveal impacts from different cover crops and mixtures that matter to farmers but are hard to catch in short, single-focus studies.