Research Highlights

Research Highlights
Long-Term Research Incorporates Cover Crop Questions to Uncover Solutions

Photo: Iowa Soybean Association

By Laura Temple

Every growing season is unique. Weather interacts with crops, soil systems, pests and countless other factors, impacting yield. But over time, those unique seasons combine into averages that help farmers understand how to best manage their fields. That’s part of the reason long-term research can identify best practices and demonstrate responses to major system changes.  

The Iowa Soybean Association’s Research Center for Farming Innovation (RCFI) has been conducting long-term research on cover crops. Working with multiple partners, the RCFI has leveraged soy checkoff investments to study cereal rye cover crops in a soybean-corn cropping system for eight years.

“This research seeks to answer questions from farmers about cover crops,” says Matt Carroll, analytics and insight lead for the Iowa Soybean Association. “Over several years, these on-farm trials with cooperating farmers across Iowa have helped find answers by comparing cover crops with no-till systems, leading us to improve the project to answer new questions.”

Long-Term Research Produces On-Farm Data

He says the trials have proven that a cereal rye cover crop following both soybeans and corn can be successful. And that time and experience make a difference.

“As growers gain more experience with cover crops, we see less variability in the yield differences between cover crops and no-till,” he says. “In soybeans in the first year, our results show a yield variability range of 10.5 bushels, and by the seventh year, the variability has been minimized to 2.4 bushels per acre.”

Carroll explains that seeing the range of the boxplots in the chart (right) shrink over time is a good indicator that farmers are learning how to better manage cover crops. Especially in soybeans, a cereal rye cover crop has little to no effect on yield after a few years.

On-Farm Data Raises New Questions

Leading into the 2024 growing season, the RCFI is leveraging a soy checkoff investment into a comprehensive long-term research project focused on improving soybean-corn cropping systems with NRCS funding. 

“Our goal is to figure out how to optimize the soybean and corn rotation if a farmer decides to implement cover crops,” Carroll explains. “This on-farm research aims to address cover crop questions based on the entire cropping system.”

The long-term cover crop trials will continue, with a shift from focusing on cereal rye cover crops. The new research project compares the incorporation of a multi-species cover crop with the standard system used on each cooperating farm. 

Carroll believes these trials will generate in-depth data that will show how the different practices impact soils. Sensors in the fields will monitor spring soil moisture and temperature to understand how these factors affect planting date and equipment access. Soil samples taken each fall will measure nutrient content, physical soil characteristics and much more. 

“We expect to better answer questions about how cover crops impact nitrogen availability and other nutrient cycling in-season, how termination timing of cover crops impacts weed control, if cover crops influence planting timing and days suitable for fieldwork, and much more,” Carroll says. “We don’t yet know what will work, but this effort will help us find out.”

On-Farm Questions Guide New Research

Like the long-term cover crop trials, the protocols for the new research reflect the focus on answering farmer questions. 

“Our team takes collaboration very seriously,” explains Alex Schaffer, research agronomist with the Iowa Soybean Association. “Our conservation agronomists, who work directly with farmers and retailers in the field, pass on ideas to our research team.”

He says farmers were asking about cover crop species, so the conservation agronomists looked at a variety of different species in small plots.

“They shared their observations about what grew well and what didn’t with our research team,” he says. “From that, we developed cover crop blends and seeding rates for the improved cropping systems trials.” 

The new trials use a three-species cover crop blend following soybeans and a different three-species blend following corn. Cooperating farmers have the flexibility to choose a cover crop seeding method that best fits their system, though the first cover crop was flown into standing crops via drones during fall 2023 to start the trials consistently.

Schaffer and Carroll note this is just one example of how current research is built from farmer questions.

Results Translate to On-Farm Recommendations

After each growing season, the RCFI research team shares the generated data and reports with conservation agronomists. That concrete data from on-farm trials provides information to farmers who are implementing cover crops for the first time or improving their current cover crop practices.

For example, the long-term cover crop trials show more variability in corn yields following cover crops than in soybean yields.

“Years of research from across the state shows farmers that a bit of yield loss is expected when implementing cover crops,” Schaffer reports. “When they have that information and details about how specific practices influence cover crops, they are more likely to have a better cover crop adoption experience.”

He notes that the benefits of cover crops can be oversold. He expects that the detailed soil data that will come out of the improved cropping systems trials will deepen understanding of those benefits. 

“We hope to figure out how to measure soil health and show improvements,” he says. “The data should help us understand how cover crops enhance nutrient use, improve water infiltration and more.”

With communication between farmers and researchers conducting on-farm trials going both ways, the team expects to get strong data that will point to practical cover crop solutions and encourage long-term adoption. The RCFI has proven the model of using research to inform adoption of conservation practices with other areas.

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Additional resources

Long-Term Conservation Practices Improve Soil Chemistry – SRIN article

Published: Mar 25, 2024